Abstract
I would like to thank my Solar Physics colleagues for asking me to write this chapter on my professional life. My main interest has always been focused on the Sun, our star, from the heating of the corona, to the dynamics of prominences and their eruptions, flares and coronal mass ejections to their impact on the Earth. I built a new group in solar physics and gave to them my enthusiasm. They brought to me a lot of satisfaction. We have made important advances in solar physics with a step forward to understand the triggers of solar activity and their terrestrial effects. Our avant-garde research and discoveries have opened new topics for the solar community. Mixing observations obtained on the ground and in space with theory and numerical simulations brings about a new perspective in research.
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1 Early Days
1.1 Childhood
I grew up after the second world war in an intellectual family with my older sister. My mother always motivated us to learn very hard and get a good job. She had been a little frustrated by not being able to do what she wanted because of the war. She traveled before her wedding to Greece and Algeria alone. It was each time an adventure for her. My father was an engineer who worked in a shipping company when he was single, landing in famous harbors in Asia (Yokohama, Hong Kong, and Saigon). Just before the war, he was hired by an oil company but was rapidly appointed to do charcoal work in a forest in Burgundy. Therefore we did not go to school and my mother was our teacher before we passed the exam at age ten to be accepted into the Lycée Marie Curie in Sceaux (city located 7 km to the south of Paris). My childhood was very peaceful (Figure 1, top left panel). After literature and Latin, I studied mathematics and physics with Catherine Lacombe and after the baccalaureate I was accepted in the Lycée Fénelon in Paris. After studying mathematics with Prof. Dixmier and fluid mechanics with Prof. Germain at the Sorbonne I attended the lectures of astrophysics with Profs. Evry Schatzman (the greatest physicist I ever met), Jean-Claude Pecker, Jean Paul Zahn, Henri van Regemorter, Roger Cayrel and Gérard Wlérick. During this time I belonged to a group of students and young post-docs, doing sport, skiing and tennis (Figure 1 bottom left panel). We were meeting every Friday in a café in the Sorbonne square, “chez Sylvain” to drink coffee and to decide what we would do the next weekend. Ngyuen Rieu belonged to the group and spoke to me about astrophysics. I was fascinated by this kind of research and by the Observatory in Meudon where he had a position in the radio astronomy department. Therefore when G. Wlérick asked if students were interested in training, I followed him and went to Meudon once a week. When I entered his office for the first time, he told me that my name “Pailhas” was familiar to him because his father, a disciple of Rodin, sculpted the bust of Mrs. Pailhas when she was very young. In fact, she was the wife of my grand uncle.
Top left, with my sister, my father, my mother (M. and Mme. Pailhas) and two of their friends in Combloux (Alps), top right: with the student group of G. Wlérick at Pic du Midi, bottom left: high school class-mates, bottom right: Saint Michel Observatory, with the electronic camera at the focus plane of the 193 cm mirror telescope. The author is indicated by red arrows.
During my master degree in astrophysics, I started to work at the Observatory of Paris in Meudon (in the stables of the castle) with G. Wlérick preparing for a “Doctorat es Sciences”. The research for my thesis effectively started when Pierre Mein, my thesis advisor moved from the Institut d’Astrophysique (IAP) in Paris to Meudon in the solar department. I defended my thesis in 1977.
1.2 University Training Time
During this long time period with G. Wlérik and P. Mein, I learned astrophysics in many of its different aspects. My training started by looking at the spectra obtained during the eclipse of 1961 at the Observatoire de Haute Provence in Saint Michel. I discovered that G. Wlérick gave this task to each student who arrived in his laboratory. Then, I computed theoretically the ratio of the forbidden Ni xv lines using atomic data updated by Burgess and Seaton in the UK. I wanted to compare my results with the spectral observations of Bernard Lyot obtained at Pic du Midi. One morning Audouin Dollfus brought me the boxes containing the frames made by B. Lyot. One frame was missing and it was just the frame of the wavelengths of the Ni xv. We never found it. During this time I was also working with the electronic camera invented and developed by André Lallemand in a laboratory in Paris. We had to check the cells and had to make a vacuum in the tube during half a day before observing. With the group of students of G. Wlérick we observed the planets (using UBV filters) at Pic du Midi and at the Observatoire de Haute Provence with the new 193 cm telescope (Figure 1, right panels). It was really fun to wait during the night for a clear sky. One winter we built an igloo in the snow on the terrace of the Pic du Midi Observatory during our waiting periods. I remember a few of my colleagues: Pierre Charvin, Loic Vapillon, Michel Combes, Paul Felenbok, Philippe Véron, and Michelle Loulergue and many young female students from the Ecole Normale Supérieure of Fontenay-aux-Roses.
Back in Meudon, I had to work to build a new spectrograph in a building called Petit Siderostat with the engineers Rolland Hellier and Christian Coutard. It never really worked because we put a selector of wavelengths after the grating which could not be adjustable. After that I participated with R. Michard in the construction of the solar tower telescope implemented by the first Multichannel Substrative Double Pass (MSDP) spectrograph invented by Pierre Mein. The observatory in Meudon developed quickly during these years, and after the construction of the solar tower we moved to new buildings adjacent to the tower. During this time, I acquired an extensive knowledge in instrumentation, in astrophysics and in atomic physics. All these different works did not lead to any publication but they would be very helpful for my future work in science. However, I realized only much later that they did not help me to get a better position. I learned at my own expense that research not published is not valuable. It is why now I always push my students and collaborators to publish their results and I am well known to ask them frequently “Where is the paper?”.
1.3 Heating of the Corona – Thesis – 1977
When Pierre Mein arrived in Meudon, I finally got a topic for my thesis: “Solar coronal heating by dissipation of acoustic waves: development of a radiative code and applications to observations”.
In 1948 Evry Schatzmann proposed that acoustic wave dissipation could work for heating the corona. Grant Athay, an American researcher, confirmed this hypothesis after theoretical computations finding that such a mechanism could be efficient. In fact nobody was really measuring the phases, velocities and amplitudes of the waves. With my observations we concluded that the waves were reflected back from the transition region between the chromosphere and the corona and were mainly standing waves. They could not heat the corona. The dissipation was too small. Before 1981 I published seven papers either alone or with Nicole Mein on this topic (Schmieder, 1972, 1976, 1977, 1978, 1979; Schmieder and Mein 1980; Mein and Schmieder 1981). After my thesis, Christensen Dalsgaard told me that I had to change my radiative transfer code in LTE (local thermodynamic equilibrium) from two to three dimensions because we had discovered that the oscillations were resonant waves in the 3D sphere of the Sun. I would have to transform my full box of computer punch cards with small holes to a new code. Each day I had to transport this box to Orsay where the computer ran the program overnight. Often I came back the next day to discover that I had forgotten a comma somewhere. It was too tiring to run such a heavy code. Therefore I decided to change of topic after my thesis defense (see Section 2.1).
Obtaining observations concerning the waves was a challenge. The solar tower in Meudon was just built and the spectrograph allowed us to get spectra of the Mg i b line in the low chromosphere, as well as H\(\upalpha\) and Ca K lines in the chromosphere. After the observations, I was running a Fourier transform code when discovered that I was measuring the oscillations of the solar tower, or of people who were going down the stairs. Indeed Jean Claude Pecker and the engineers had an office upstairs. The interior and the external towers were tied together in the basement by concrete. After inspection, M. Remondet, the architect, agreed to separate the two towers with a hammer drill. At the same time Pierre Mein thought that the best way to track the granules and the chromospheric pattern was to open the slit and use algorithms to follow them. It was the birth of the MSDP. In fact Pierre Mein spent one year at Sacramento Peak Observatory in New Mexico and the best for me was to go there (my first airplane trip lasted 36 hours!). I observed there during the day and digitized the spectra during the night. They had great facilities that we did not have in France at that time. I met many famous scientists at Sac Peak: Dave Rust, Richard Altrock, Richard Canfield, and only one woman, Joan Vorpahl. When Pierre Mein was at Sac Peak and I was back in Meudon, I could discuss my problems of radiative transfer with Philippe Delache and Christian Magnan.
I had to develop everything by myself, there being no existing material, e.g., codes or observations. Pierre Mein was there to encourage me and give me good advice every six months. I would really like to thank him for his bright ideas. Pierre Mein and Nicole Mein are still working on the new generation of MSDP and very active in making and observations, enthusiastic in taking part in coordinated campaigns. I had and still have an intensive collaboration with them throughout my research career (see my recent paper on prominence-tornadoes with them using observations made at the Meudon solar tower with the MSDP (Schmieder et al. 2017b)).
1.4 Family
During my thesis I had also another task to do. A thesis was at that time a long piece of work and could last for ten years before the change of thesis format to fit with the international Ph.D. thesis of 3 years. I built a family with three children: one boy, Laurent, and two daughters, Anne and Céline (Figure 2). I would like to thank my husband Eric who always helped me to realize my wishes, to go to Sac Peak for one month with a two years old baby at home. I could manage to combine the mother’s life with my work thanks to him. After bringing the children to school at 8:30 am I was back home at 6 pm for the homework.
Left, on the French Riviera with my three children: Céline, Anne and Laurent, right, winter sport in the Alps with Anne, Laurent and Céline.
My husband after his university studies, his administration school (Ecole Nationale d’Administration – ENA) and his military service entered in the Ministry of Health directed by Simone Veil. He was hard working and came back home only after 8 or 9 pm. We were well organized with a nurse/nanny who received nearly all my salary. But I knew that it would benefit me in the future. This situation lasted only for 15 years. It is a short period of time in a long professional career. I never interrupted my career for more than six weeks even with my three maternity leaves. Research is progressing fast and we always need to read and update our knowledge to be able to have the right questions. We enjoyed very much to spend time with our three children during our holidays in our country house in Faverdines since 1966 (3 hours from Paris), in the Alps since 1980 (Val Thorens), on the sea side in Rayol Canadel or visiting different countries (Germany, Portugal, Morocco, US) (Figure 3). It was a fascinating time for us to see them growing so fast. They get very rapidly an autonomy which helped them for their future. All three children obtained very good jobs. Laurent, after the Ecole des Arts et Métiers (ENSAM), is an engineer at the CEA (Commissariat à l’énergie atomique) and is building the ITER facility in Cadarache. Anne and Céline earned very good diplomas from the school Ecole Polytechnique Féminine (EPF) and entered in the bank research and development department. In industry they have to work very hard until 8 pm. They sometime regret not having chosen a career in research where you have a lot of work to do but you are your own manager. They saw their mother always working but they realized only later the freedom that the researchers have. By this time I was also involved in discussions about the ethic of research in a working group at the Assemblée Nationale (French Parliament) managed by Alain Lamassoure, an elected representative of parliament.
Where I spend my holidays with my children and friends and now where I am writing my papers and reviews: Val Thorens in the Alps, Saint Antonin Noble Val in Tarn et Garonne department, Le Rayol Canadel with its famous beach on the Riviera, Faverdines, a charming small house with a large garden that many of my colleagues know.
Now I have eight grand children and am happy to invite them to our different holiday residences or to visit different countries where meetings take place (Figure 4). They particularly appreciate watching the solar eclipses and like very much the COSPAR General Assemblies with their space exhibitions (Figure 4). They discovered that the English language is important to communicate with others.
Top left, my family: me, my husband Eric with our three children, the spouse of our son and husbands of our two daughters and our eight grand children in the garden at Faverdines. Top right: visit of the Forbidden City in Beijing with my grand children Camille and Adrien during COSPAR in 2006, bottom left, the eclipse in 2009 in Hangshou (China) with Wahab Uddin, me, Grégoire and my husband. Bottom right: the eclipse on August 21 in 2017 in Madras (Oregon, US) with Sarah Gibson and Mark Miesh and their family seated on chairs, behind them, standing up, my family: Capucine, Grégoire, Eric, Gautier and me (in red tee shirt).
2 Research
2.1 My Concept of Research
In 1980 the Solar Maximum Mission (SMM) was launched. The researcher Einar Tandberg-Hanssen, a Norwegian who had emigrated to the US, and very fond of France, visited our laboratory (see his memoir – Tandberg-Hanssen 2011). He was the principal investigator of the UVSP spectrometer onboard SMM. He demonstrated to us the interest of combining multi-wavelength observations to understand the activity of the Sun. These two events changed completely my research topics and my life. During the preceding ten years I have been mostly alone in my office, not traveling, and then I discovered foreigners working together and discussing together.
It was a new world for me, more appropriate to my life concept. E. Tandberg-Hanssen has been the main actor to open to me the NASA laboratories in the US (GSFC, MSFC) and also to make strong links with Norway (Figure 5). Later on, I became the advisor of Jun Elin Wiik, a Norwegian student (thesis defense in 1993). And finally, because of the success of Jun Elin Wiik, I got a part time professorship in Norway from 1996 to 2006 working on filaments with Oddbjorn Engvold and his staff, e.g., Jun Elin Wiik and Yong Lin (Ph.D. student). I was the second woman to teach physics at the University of Oslo in Blindern. I appreciated very much all my visits in Oslo between the fjords and the mountains with my colleagues: Oddbjorn Engvold, Olav Kjeldseth-Moe and Mats Carlson who became a Chevalier du Tastevin in Burgundy due to my sponsorship.
Top left, photo taken at the SMM Workshop in Airlie in 1987: Art Poland, Einar Tandberg-Hanssen, Brigitte Schmieder (BS), Guy Simon, Jean-Marie Malherbe (Ph.D. student), top right, waiting for the eclipse in 1999 at Szombathely in Hungary: Spiro Antiochos with his son and wife, BS, Pascal Démoulin with his wife, Eric Schmieder, bottom left, Guo Yang defended his thesis in Nanjing 2011 with the jury: Mingde Ding, Cheng Fang, BS, Hubert Baty. Bottom right, during the Aussois meeting in 1997, a concert was given by Véronique Bommier, Bernard Foing with his daughter, Petr Heinzel, Jean-Francois Mein and Pierre Mein.
All my research was oriented according to the collaborations that I managed through bilateral research projects which led me to visit many countries (US with Einar Tandberg-Hanssen, Art Poland, Dave Rust, and Leon Golub, Japan with Hiroki Kurokawa and Kazunari Shibata, Czech Republic with Petr Heinzel, Greece with Kostas Alissandrakis, Georgia Tsiropoula and Kostas Tziotziou, China with Fang Cheng, Argentina with Marcos Machado and later with Cristina Mandrini, India with Venkatakrischnan and now with Ramesh Chandra in ARIES, and recently Korea with Tetsuya Magara at Kyung Hee University and Young Deuk Park in KASI). All these researchers brought and still bring to me a lot of knowledge in different aspects of astrophysics.
I visited China for the first time in 1991. I was invited by Xiaoma Gu for one month in Kunming and again in 2004 (Figure 6, top left panel). There I also met Jun Lin as a young student. In China at that time there was no xerox machine to copy the rolling paper where flare spectra of interest were recorded. I traced the spectra on a paper and in Meudon I digitized them by using a machine overlying each curve with a stiletto and then published a paper on post-flare loops (Gu et al. 1992). Before returning to France, I visited Beijing with Ai Guo Xian and Fu Qi Jun and Nanjing with Cheng Fang (see his memoir – Fang 2018) who could speak French fluently after his stay in France in 1987. I have a nice story about the arrival of Cheng Fang in our laboratory. Jean-Claude Hénoux, our director at that time, received a letter asking him if we would agree to have a Chinese visitor for two years. He said yes. After three months he received the same letter. He replied: Yes of course. In fact, one was Cheng Fang and the other one was Feng Cheng from Kunming. Finally both came for two years. Later I visited China again, mainly for giving lectures to young students (Figure 6 right panels), and to attend meetings, e.g., the French–Chinese meetings in Xian and Shanghai, the 36th COSPAR General Assembly in Beijing, the first Chinese–European meeting in Kunming in 2017. I was co-advisor of two Chinese Ph.D. students: Yang Guo (Figure 5, bottom left panel) and Jie Zhao, who defended their theses in 2011 and 2014, respectively.
Top left, Kunming in 2004: Kejun, Li, Xiaoma Gu, Xiaoyu Zhang and Brigitte Schmieder (BS), top right, Huairou 1991: Fu Qi Jun, BS, Ai Guo Xian, bottom left: dinner by Eijero Hiei (on the right) in Tokyo in 1993: Hong Qi Zhang, Cheng Fang, Tang, BS, bottom right: after the 36th COSPAR 2006, during lectures in Beijing: first row, Yuanyong Deng, BS, Shibata, Yokoyama, second row: Hong Qi Zhang, Guiping Ruan, third row: Xinming Bao and students.
I should also mention my numerous trips to India. I was first invited in Nainital in 2005 by Wahab Uddin where I met Ramesh Chandra and Navin Joshi, who are very good observers. I got an official collaboration (CEFIPRA) with Nainital, Udaipur, and Oooty. This allowed me to work and have many exchanges with colleagues and their students in India. I was invited to watch the eclipse in 2009 with Grégoire, my grandson by W. Uddin and Siraj Hasan in Hangshou where we arrived after a long trip during the night. They were still waiting for us. Siraj said, Brigitte did not cancel her trip, so we have to wait for her all the night. And we were rewarded with clear skies (Figure 4 top bottom panel). I will refer later to our scientific results.
In addition, we had individual foreign visitors who also interacted strongly with our team and our Ph.D. students. I will refer to them later to this memoir. All my Ph.D. students (Jean-Marie Malherbe, Pascal Démoulin, Guillaume Aulanier, and Etienne Pariat) could work with them. That was an excellent training for my students and we maintained good relationships and even friendships with all of the foreign visitors. Our French team developed as an extended group with all these researchers without frontiers. With this very friendly and active ambience, and due to their excellent skills, all my French Ph.D. students cited above got a permanent job at the Paris Observatory and formed the roots and core of the present solar group.
2.2 Time of SMM and J.M. Malherbe – 1980s
Jean Claude Pecker encouraged Guy Simon to submit a proposal to the Guest Investigator program committee of the Ultra Violet Spectrometer (UVSP) on UV waves after flares. The proposal was successful and we got a few weeks of observing time during several years. Guy Simon and I went to the building 7 or 21 at NASA/GSFC in Greenbelt near Washington DC for planning our observations (Figure 5, top left). Each morning we had a meeting to decide the target of the next day to determine the pointing of the telescope. The members of the committee hated our proposal which required one to move away from the flare site but E. Tandberg-Hanssen regularly reminded them that they had accepted the proposal so it should run. On Sundays Guy Simon was not allowed to enter the NASA compound because of his involvement in politics and I had to discuss alone the target of the day. These observations were coordinated with Meudon using the MSDP at the solar tower. Christian Coutard and Roland Hellier were our observers and they had to develop wrapping black and white films in dark rooms every day. Besides it was not easy for Pierre and Nicole Mein to receive the coordinates of the target. In the 1980s internet communications were just starting. In Meudon there was only one telephone-modem in the computer center with which we could communicate with the operation center at NASA/GSFC.
The aim of the proposal was to study the propagation of waves in UV after flares. It was a completely unknown topic at that time, only the Moreton waves were observed. We were really pioneers on this topic. To achieve our goal we requested that after the flare flag we move the center of the field of view to the edge of the camera and wait for the passage of the wave. With a Fourier transform code we tried to detect the waves. After nights and nights spent on the computer no wave was detected, due to the low cadence of the instrument. However, the data that we obtained were generally centered on filaments so we started to work on filaments. I met many scientists during that period with whom we continued to work later, e.g., George Simnett, Art Poland (Figure 5, top left). All became good friends and visited France frequently. Recently I started to work again on these famous EUV waves that have been discovered with the next satellite instruments in UV onboard SOHO /EIT and SDO/AIA (Delannée et al. 2014; Chandra et al. 2018).
During all these years (1980s) I was organizing coordinated campaigns observing simultaneously on the ground with the MSDP either in Meudon or at Pic du Midi with Pierre and Nicole Mein. With the MSDP we were observing mainly in the H\(\upalpha\) line jointly with the UVSP instruments in the EUV lines like C iv for Dopplershifts of the plasma at \(10^{4}\) to \(10^{5}\) degrees. Different topics were open to us: the understanding of the dynamics of the cool plasma in prominences, cool jets or surges, and flares. We reported our results in many conferences, e.g., Airlie (US) in 1987 (Figure 5, top left), in Palma de Majorca in 1987 (Figure 7), in Aussois in 1997 (Figure 5, bottom right), in Hungary for the eclipse in 1999 (Figure 5, top right).
Workshop on the Dynamics and structure of solar Prominences in Palma de Mallorca in November 1987, first row, from left to right: Pierre Mein, Oddbjorn Engvold, Ulrich Anzer, Brigitte Schmieder, Eric Priest, Marie José Martres, Guillermo Vizoso Miguel del Sola, Art Poland, Horst Balthazar, Alan Hood, Bogdan Rompolt, second row, José Ballester, Eberhard Wiehr, Jean Marie Malherbe, Véronique Bommier, Jean Louis Leroy, –, Pascal Démoulin, –, –, Fernando Moreno Insertis, Pierre Gouttebroze.
Jean-Marie Malherbe came in the group to start a thesis in the early 1980s. He was interested in instrumentation, physics, and computations. He worked with us on the dynamics of prominence plasma condensations and on the dynamics of flare ribbons. We had a great chance to meet two bright theoreticians who visited us many times, Mike Raadu and Terry Forbes. They brought innovative ideas during fruitful discussions. Our measurements from the MSDP were quantitative and not only descriptive, therefore they were interested in checking their ideas or computations. A very intensive collaboration with theoreticians started at that time. It was the seed of the birth of the Meudon solar MHD group in the future. With the observations at Pic du Midi combined with the C iv data of the UVSP provided by Einar Tandberg-Hanssen and Art Poland, we could measure the dynamics in fine structures of filaments, up and down motions in the feet and horizontal flows along the axis of the filament, rotation along the filament axis in the case of disturbances, and oscillations in filaments (Martres et al. 1981; Malherbe, Schmieder, and Mein 1981; Malherbe et al., 1982, 1983, 1987; Mein et al. 1982; Schmieder et al., 1984, 1985; Simon et al. 1986). Mike Raadu proposed to us some simple models to explain the drainage of cool matter when the loops passed through the photosphere, the empty basket model (Raadu et al. 1987a), and also a destabilization model of a filament showing twisted motions in a flux rope which lifted up as in the torus instability advanced later on by Tibor Török (see Török et al. 2011 and the references therein). Filament destabilization could be explained by photospheric motions; see Raadu et al. (1987b, 1988).
With George Simnett and Einar Tandberg-Hanssen we understood that surges formed of cool plasma observed in H\(\upalpha\), and jets of hot plasma visible in UV and X-rays, were co-aligned and had similar velocities (Schmieder et al., 1982, 1983, 1984, 1988b, 1988c, 1993, 1996c; Fontenla et al. 1994). At the same time I worked also on surges with American scientists who were visiting us: Leon Golub and Spiro Antiochos (Schmieder, Golub, and Antiochos 1994). Both of them became good friends of the group and we could apply for post-doc positions at NRL in Washington and visitorships at SAO at Harvard for our students for their training in MHD, e.g., Guillaume Aulanier, Etienne Pariat, and Sophie Masson.
Detection of transverse oscillations in filaments in H\(\upalpha\) was achieved by Bill Thompson using MSDP observations (Thompson and Schmieder 1991). The SMM mission launched in 1980 was lost during a few years before a cosmonaut going out of the Space Shuttle could recover and repair it by using a Canadian robotic arm. It was an unbelievable rescue for the spacecraft. Our group (Nicole Mein, Pierre Mein, Guy Simon, Jean-Marie Malherbe, and I) could work with the data until 1989 with our friends of the UVSP spectrometer. The Meudon solar tower was closed in the 1990s and could re-open only in 2003 when THEMIS, the French–Italian magnetograph, on Tenerife, the Canary islands (opened in 1997) was fully operating and also after recording on film was replaced by J.M. Malherbe with a CCD camera, more convenient for the observations. J.M. Malherbe was a very fast thinking student and it is always interesting to work and discuss with him and Thierry Roudier in Toulouse the horizontal flows below filaments (Roudier et al., 2008, 2018; Schmieder et al. 2014a).
Our work with Terry Forbes concerned mainly flares. He and Jean-Marie Malherbe developed an MHD model (using the code SHASTA) to explain reconnection in the corona and the cooling of the plasma inside the reconnected loops (Forbes and Malherbe 1986). The observations of the flare ribbons that I had obtained in Meudon followed exactly their predictions. It was the discovery of the evaporation of the chromosphere with two phases: the impulsive phase and the gentle evaporation phase in post-flare loops (Schmieder et al., 1988a, 1990). I had the chance to meet again Terry Forbes in New Hampshire and during conferences, e.g., in Romania in conferences organized by Cristiana Dumitrache (Figure 8, bottom right panel). In the 2000s we could confirm the predictions of Forbes and Malherbe simulations concerning the chromospheric evaporation by using NLTE (non-local thermodynamic equilibrium) radiative transfer computations and data of SOHO/CDS with Arek Berlicki and Guilio Del Zanna (Berlicki et al. 2005; Del Zanna et al. 2006). In the 1980s we were pioneers in this field of research.
Left, Hokaido in Sapporo Island visit of the Inuits after S-Ramp meeting in 2000 organized by the SCOSTEP to summarize the results of the STEP program, first row, Lidia van Driel, Stefaan Poedts, second row, Ed Cliver, Dave Webb, Brigitte Schmieder, top right Berlin, during a JOSO meeting in Potsdam in 1999: Lidia van Driel, BS, Pascal Démoulin, Cristina Mandrini, bottom right, after the Space Weather meeting in Bucharest in 2008: Stefaan Poedts, BS, Terry Forbes.
Other interesting topics involved collaborations with our Greek colleagues. While working on sunspots the Evershed effect was found to reverse in the chromosphere compared to the direction observed in the photosphere (Alissandrakis et al. 1988; Dere, Schmieder, and Alissandrakis 1990). With Georgia Tsiropoula we analyzed carefully the MSDP data concerning the chromospheric fine structure to understand if mottles on the disk were the same as spicules visible at the limb and had fruitful discussions with Petr Heinzel who was not always in agreement with our results (Tsiropoula, Alissandrakis, and Schmieder, 1993, 1994; Tsiropoula and Schmieder 1997; Heinzel, Schmieder, and Mein 1992).
From 1990 to 1996, I was elected as vice president of the European Solar Physics Division (ESPD). As ESPD vice president I organized two meetings (ESPM) with president George Simnett in Catania (1993), and in Thessaloniki (1996). In 1992 I was also elected as president of the Joint Organization of Solar Observations (JOSO) in Europe until 2002. JOSO had been created to develop collaborations between the solar observatories in Europe. Therefore I organized each year a meeting, e.g., Trieste in 1994 (Figure 9, top left and bottom right panels), and Potsdam in 1999 (Figure 8, top right panel). Because the attendance increased to more than 150 participants, I wrote proposals to the European Union to be sponsored. I got two successful EU contracts during my JOSO presidency to organize successively two series of European conferences: three of them on “Advances in Solar Physics” in Tenerife (1996), Preveza (1997), and Catania (1998) published in PASP journals and two of them on “Solar cycle and Space Weather” (SOLSPA) in Tenerife (2000) and in Vico Equenze near Napoli (2001) published by ESA publications.
JOSO group visiting the radio telescope in Trieste in October 1994: from left to right we can recognize some scientists: Bojan Vršnak, Mauro Messerotti, Paolo Zlobec and behind Axel Hofmann, Peter Brandt, Edith Muller – former president of JOSO –, behind, Richard Muller, Thierry Roudier and BS (president of JOSO), Janusz Sylwester, Pierre Mein, Lucas Vlahos, top right: BS and Nicole Mein working in Meudon observatory, bottom right, dinner during a JOSO meeting in Trieste in 1994: Costas Alissandrakis, BS, Paul Brekke, Greek scientist, Bob Bentley, –, Philippa Browning, David Alexander, Bernard Fleck, behind Meir Semel and Peter Brandt, bottom left: Lidia van Driel, George Simnett, BS during the Preveza Euroconference in 1997 on Advances in Solar Physics visiting Dodona in Greece.
The main objective of JOSO was to involve the solar physicists of all the European countries to create a data-base of solar observations, and to define the characteristics of a future large European telescope. Now this objective is pursued by the European Association for Solar Telescopes (EAST) consortium, which has been charged to build the European Solar Telescope (EST) (4m mirror). Today the plan is to start construction in 2021 and to achieve the first light in 2027. Let us see what the future of EST will be.
Between 1980 and 1992, I was the public outreach manager of the Observatoire de Paris. I was in charge of press releases and the organization of visits to the Observatoire de Paris in Meudon of students and the general public. I organized night shows for journalists, lectures for teachers on Wednesdays and also open doors for the public once a year. People appreciated these initiatives and it happened that we had more than one visit of 30 persons each day. Particularly memorable was the open house in May 1985 when 10 000 persons visited the observatory during the weekend (Figure 10). I got funding from the Ministry of the Culture for renovating the big dome (over the Meudon castle) and the refractor built by Jules Janssen.
Left, poster for the open house on 11 and 12 May 1985 in Meudon (drawn by André Mangeney), right, poster for the IAU S300 symposium in Paris dedicated to Einar Tandberg-Hanssen (designed by Sylvain Cnude).
But after the tornado in Paris in December 1999 the dome lost part of its cover and despite some ministry funding, it is still under reconstruction and no visits are possible anymore.
2.3 Time of Yohkoh and P. Démoulin – 1990s
My work all along my career was guided by the new solar missions launched to resolve the problem of coronal heating. It is still an up-to-date topic as we heard on TV on August 12, 2018 when the Parker Solar Probe was launched to approach the Sun, the main goals being to understand the heating of the corona, and to measure in situ the solar wind for future journeys of humans to Mars or the Moon.
After SMM, Yohkoh, the Japanese–American mission was launched in 1991 with several instruments. I was mainly involved with the Soft X-ray Telescope (SXT). During that time period TRACE (1998) was dedicated to observing the Sun in UV. Both SXT and TRACE observed partial fields-of-view and we needed to select the targets. I was guest investigator for both missions and organized multi-wavelength campaigns; Yohkoh was open to foreigners only after 1993. I went to the Institute of Space and Astronomical Science in Fuchinobe several times learning how to process the data. It was the beginning of the solar software (SSW).
I met many scientists again: Bob Bentley (Figure 9, bottom right), Jim Lemen, Lidia van Driel (Figure 8 left) and by chance a few Japanese in Mitaka: Tadashi Hirayama, Eijiro Hiei (Figure 6 bottom left), Takashi Sakurai, Hiroki Kurokawa and Kazunari Shibata (Figure 11) (see the paper on surges by Schmieder et al. 1995a) and those on X-ray bright points (van Driel-Gesztelyi et al. 1996; Mandrini et al. 1996). The main topic that we worked on was flare-loop formation. For the coordinated campaign with Yohkoh we (J.M. Malherbe, P. Mein, and the author) were observing with the MSDP at the “spectro tourelle” at the Pic du Midi in the 1990s. We obtained very fine observations of flare loops with the MSDP in June 26, 1992 to compare with the Yohkoh loops. These observations led to more than six papers with Jun Elin Wiik, Jean Marie Malherbe, Lidia van Driel, and Petr Heinzel (Schmieder et al., 1995b, 1996b; Wiik et al., 1996, 1997; Malherbe et al. 1997; van Driel-Gesztelyi et al. 1997). I had already started with Petr Heinzel to work on plasma conditions in post-flare loops (Heinzel, Schmieder, and Mein 1992). We continued and computed the theoretical times needed to cool the X-ray loops to H\(\upalpha\) temperature by radiative cooling and conduction (Schmieder et al. 1995b) and could confirm what the model of Terry Forbes predicted: that the hot loops visible after reconnection in X-rays with Yohkoh were cooled down to \(10^{4}\) K after a certain time and observed in H\(\upalpha\). Other papers appeared later on post-flare loops visible after the impulsive phase of flares (Gu et al. 1997; Schmieder, Fang, and Harra-Murnion 1998).
St. Andrews 2007, first Flux Emergence Workshop, in front of the house of Eric Priest, from left to right, first row: Isobe Hiroaki, Fernando Moreno Insertis, BS, Shibata Kazanari, Eric Priest, Gael the wife of Dave Rust, Clare the wife of Eric, second row: David Hughes, Dave Rust, Laurène Jouve, Evy Kersale, Clare Parnel, Etienne Pariat, Alan Hood, Dana Longcope, Sacha Brun, Klaus Galsgaard.
However, during the loss of SMM and before the launch of SOHO (1996), the space data were not easy to access and it was the period when Jean Heyvaerts, who was the responsible professor assigning Ph.D. students in different laboratories, proposed to me to be an advisor of Ph.D. students. Heyvaerts appreciated the way that I was training students on solar observations with a broad view. In the first year, I got a very bright Chinese student Z.S. She (She, Malherbe, and Raadu 1986) but he wanted to work only on turbulence so after one year he moved to Nice to work with Uriel Frish. The next year I got Pascal Démoulin, and Heyvaerts told me that I should be able to teach him to explain the whole “zoo of solar physics: flares, sunspots, plages, surges and eruptions.” It is with Pascal that our solar MHD group was finally born. For his Ph.D. I had to find a theoretical group which could give to him a proper theoretical background. I had a good relationship with theoreticians in Florence, e.g., Georgio Einaudi, Franca and Claudio Chuideri. Pascal was very enthusiastic to interact with them. However, after one year no paper has emerged. My famous question “Where is the paper” was asked. At that point he had only one but very impressive paper with me and Mike Raadu on the role of parallel and perpendicular conduction in the stability of filament fine structures (Démoulin et al. 1987). Because I knew that he had to publish if he wanted a permanent position, I asked Eric Priest if Pascal could visit him in St. Andrews. Eric Priest reported in his memoirs: “It was a real pleasure to work with him, since he is so bright and couples a superb physical understanding with great technical skills” (Priest 2014). And this is how and why a solar MHD group developed in Meudon. Pascal and myself were invited to many meetings, e.g., in Potsdam for the JOSO meeting in 1999 (Figure 8, top right panel) and in Hungary for the 1999 eclipse (Figures 5, top right panel).
As a Ph.D. student, P. Démoulin began to work with the general topic of prominence equilibria, the formation of dips and their support and loss of equilibrium or instability in a force-free field (Démoulin and Priest, 1988, 1993; Démoulin, Malherbe, and Priest 1989; Démoulin and Raadu 1992). These ideas were further developed by Guillaume Aulanier in his thesis (Aulanier and Démoulin 1998, Aulanier et al. 1998b, 1999; Aulanier and Schmieder 2002). And so later on Pascal Démoulin kept contributing intensively to the theoretical training of my other Ph.D. students. By that time (1990s) P. Démoulin was also interested in the topology of the flaring active regions and pioneered research on reconnection without null points, along the quasi-separatrix layers (QSLs) (Démoulin et al., 1996, 1997). This theory was applied to many observations, by the successive scientists of our group, e.g., Guillaume Aulanier, Etienne Pariat, Kevin Dalmasse, and also in Argentina, China and India (Deng et al. 1999; Mandrini et al., 1996, 1997, 2006; Schmieder et al., 1997, 2007b; Moore et al. 1997; Berlicki et al. 2004). This work continues to be developed by the Argentinean group, still with linear force-free field extrapolations. By comparing the similarity of the locations of QSLs for a few case-studies using linear and non-linear force-free field approaches, the robustness of the QSLs, regions of intense electric currents before flares, has been demonstrated (Mandrini et al. 2014; Chandra et al. 2011; Dalmasse et al. 2015; Joshi et al. 2019).
In the 2000s P. Démoulin applied the theory of the conservation of magnetic helicity to active regions and showed that the excess of magnetic helicity in twisted flux ropes can be expelled by coronal mass ejections (CMEs). This created a stream of various papers in our group (see the papers in Patriat’s thesis, Chandra et al. 2009; Zhao et al. 2014) and more recently papers by Kevin Dalmasse (Dalmasse et al. 2018). It is still a topic of focus in the group with our new Ph.D. student Luis Linan.
2.4 Flux Emergence – Flare Genesis Experiment – E. Pariat – 2000s
The Flare Genesis Experiment (FGE) was a balloon-borne telescope that made a journey of 17 days around the South Pole at 36 km altitude in the sky (Figure 12). This experiment was a precursor of the recent SUNRISE instrument. FGE was a Fabry–Pérot instrument with which we could observe the chromosphere in the H\(\upalpha\) line and a magnetograph which registered the Stokes parameters. Dave Rust was the PI of the different flights of this experiment. In 1998 the balloon came down in the French territory Terre Adélie in Antarctica just a few days before the closing of the base. Dave Rust did not have the official contacts between NASA and the French CNES needed for the telescope to be retrieved. Finally he phoned me on a Sunday asking me if I could help. I called Roger Gendrin in Brest and everything went smoothly. The observations were recovered and sent back to MacMurdo by using a small French airplane. In 2000 Dave proposed to me to participate in the second flight of FGE in case similar problems with the French territory arose. I spent a month at MacMurdo base helping to adjust the instruments, and, after the launch, to define the targets for FGE, jointly with observations obtained with TRACE and Yohkoh. Dave Rust was a fantastic manager and organized our stay (only six persons at the base including Pietro Bernasconi) very smoothly. I thank him very much for giving me the opportunity to go to Antarctica.
Left, launch of the Flare Genesis Experiment hung below a balloon in MacMurdo (Antarctica) in 2000, right: Brigitte Schmieder and Dave Rust adjusting the coelostat in the barn before the launch.
We were lucky to observe newly emerging magnetic flux during this flight. With my new Ph.D. student Etienne Pariat, we could, for the first time, derive the undulatory behavior of the flux tubes as they emerged through the photosphere, by analyzing the magnetic vectors and constructing the magnetic field in the corona using a linear force-free extrapolation. We also located the heating points where magnetic reconnection occurs and the cooling and heating loops at different temperatures over the emerging flux region (Georgoulis et al. 2002; Pariat et al. 2004; Schmieder et al. 2004c) (Figure 13). Now with SDO/AIA and HMI it is possible to see all the UV bursts over the full disk produced by flux emergence. My more recent Ph.D. students, e.g., Zhao Jie and Michalina Grubecka, continued this work as a part of their theses to determine where the reconnection really occurs, in the photosphere or higher up, based on a non-linear force-free extrapolation as well as with the NLTE modeling of Ellerman bombs (EBs) provided by Arek Berlicki and Petr Heinzel (Pariat et al. 2007; Zhao et al. 2017; Grubecka et al. 2016).
Flare Genesis Experiment results: (a) magnetic field in the photosphere, (b) electric currents in the photosphere, (c) Ellerman bombs in H\(\upalpha\) and joint observations obtained with TRACE (d) temperature minimum and transition region (e) as well as (f) Yohkoh/SXT observations of very hot loops in the corona (Pariat et al. 2004; Schmieder et al., 2004c).
We summarized the main results of this work in a review on emerging flux (Schmieder, Archontis, and Pariat 2014) and a review on UV bursts (Young et al. 2018). The first workshop on flux emergence (FEW) has been organized in St. Andrews to celebrate the success of the Flare Genesis Experiment by Dave Rust in 2007 (Figure 11) and since that time a FEW is organized every two or three years. In 2019 it was held in Japan without Dave, who passed away during the winter of 2019.
2.5 Prominence Studies – Jun Elin Wiik–Petr Heinzel – From 1990 to Now
In the early 1990s Einar Tandberg-Hanssen asked me to be the advisor for the thesis of Jun Elin Wiik, a Norwegian student of Eberhart Jensen in Oslo. He recommended that we worked on the fascinating structures called prominences which have a long history since their discovery by Secchi (1875) and the successive classifications existing on material protruding over the limb (Tandberg-Hanssen 1995). Jun Elin started to work on the characteristics of prominence plasma by deriving the electron density (Wiik, Heinzel, and Schmieder 1992). Then she studied the dynamics in filaments using observations made with the MSDP at the spectro tourelle at Pic du Midi. We discovered flows in both directions along filament threads, which would be called “counter-streaming” flows seven years later (Schmieder, Raadu, and Wiik 1991). Using the UV data of the rocket-launched High Resolution Telescope Spectrometer (HRTS), she computed the differential emission measure in prominences and uncovered their multiple sub-resolution thread morphology (15 to 30 threads per pixel) (Wiik, Dere, and Schmieder 1993). This former result has been, more than ten years later, the basis of the development of multi-thread models (Gunár et al. 2007).
After her thesis defense in 1993 Jun Elin Wiik got a post-doc in Norway and I obtained a part time professor fellowship in Oslo in 1996. It was the time when SOHO was just launched. SOHO is a fantastic mission; its coronagraph LASCO is still working as I write this. However, I was more interested in the spectroscopy data obtained with SUMER. I spent a lot of time during my visits in Norway processing the data by using the software developed by the Norwegian group, e.g., Mats Carlson, Oddbjorn Engvold, and Olav Kjeldseth-Moe. The SUMER data were obtained during coordinated campaigns focused on filaments and prominences with the Swedish solar telescope (SST) at La Palma, the MSDP at Pic du Midi, and the space instrument TRACE.
At the same time we invited Petr Heinzel to Meudon. After working on prominences and post-flare loops with Jun Elin Wiik (see Section 2.3), he oriented his research towards developing his NLTE radiative-transfer codes to interpret the SUMER spectra. With SUMER we could observe all the hydrogen Lyman series lines and derive the plasma conditions in filaments, prominences and chromospheric fibrils. Lyman lines obtained with SUMER were a good diagnostics for determining the characteristics of the plasma (Wiik et al., 1997, 1999; Schmieder et al. 1999). Many interesting results were obtained on eruptive prominences, multi-threads and fine threads in prominences (Schmieder et al. 2004a). In particular we showed that filament absorption fine structures observed in H\(\upalpha\) with SST corresponded exactly to the darker fine threads observed at 195 Å by TRACE in the filament channel.
Petr Heinzel developed his MALI codes to adapt them to many different cases and structures. It was and it still is a real pleasure to have discussions with him. He is a hard worker and always finds a solution. I have always found it fun to be invited for a barbecue in his house during my visits in Ondřejov (Figure 14, bottom right panel). We published 30 papers on prominences from 1998 up to now. For ten of them he is the first author, mainly concerning theoretical aspects, for ten other papers on observations I am the first author. The observations are limiting conditions of theoretical models for prominence formation and mass loading for coronal mass ejections during filament eruptions. Let us mention some of them: (Schmieder et al., 1999, 2004b, 2007b; Heinzel et al., 2000, 2008; Heinzel, Schmieder, and Tziotziou 2001; Schmieder, Tziotziou, and Heinzel 2003; Heinzel, Anzer, and Schmieder 2003). The other ten papers from the 30 papers were led by scientists of his group in Ondřejov, e.g., Pavel Schwartz, Arek Berlicki, Stano Gunàr, Jaro Dudik (Schwartz et al., 2004, 2006; Gunár et al., 2010, 2018; Berlicki et al. 2011; Parenti et al. 2012). In particular S. Gunàr adapted the MALI 2D-code of radiative transfer to multi-thread structures which could be applied to the SUMER and MSDP observations (Gunár et al., 2007, 2008, 2012). The asymmetry in the Lyman line profiles could be explained by multi-structures having different velocities along the line of sight.
Top left, THEMIS in Tenerife in 2008, top right: visit of the observatory in Ténerife during the EU meeting in 1996: Guillaume Aulanier, Guillaume Molodij, Arturo Lopez Ariste, bottom left, ISSI meeting in Bern on Solving the Prominence Paradox, first row: Stano Gunár, Jack Jenkins, Manuel Luna, Terry Kucera, Arturo Lopez Ariste, Nicola Labrosse (PI), second row: Petr Heinzel, Maciej Zapiór, Sonja Jejčič, T. Rees-Crockford, Andrew Rodger, Duncan Mackay, BS, bottom right: Dinner in the garden of Petr Heinzel, from left to right BS, Petr Heinzel, Pavol Schwartz, the wife of P. Heinzel, Arek Berlicki in 2009.
With Hinode, a Japanese solar mission, high resolution observations were obtained in the optical range with the SOT. They allowed us to see fine structures of prominences and their high dynamic nature in Ca ii and H\(\upalpha\) lines. Many intriguing structures were discovered, e.g., rising bubbles, plumes, vertical threads. I started to discuss with my MHD group how we could reconcile the MHD model of horizontal field lines with dips developed in Aulanier’s thesis (Aulanier et al. 1998a) with such observations. We invited Jaro Dudik to model these structures and we concluded that the quasi-vertical threads were just pile-ups of dips in horizontal magnetic field lines and the bubble was a magnetized volume surrounded by a separatrix and a null point (Dudík et al., 2008, 2012). We demonstrated that the bubbles were not hotter than the surrounding corona (Gunár et al. 2014). Reconnection at the null point could initiate the dynamics of the plasma and the direction change of the dips to form a plume.
With the new UV spectrograph, Interface Region Imaging Spectrograph (IRIS), launched by NASA in 2013, I, with Nicolas Labrosse from the University of Glasgow, we continued to organize multi-wavelength observations during coordinated campaigns with THEMIS in Tenerife and the MSDP at the Meudon solar tower in the years 2013 – 2016 (Figure 16). I was observing with Arturo Lopez Ariste, then resident astronomer at THEMIS, our French magnetograph in the Canary Islands (Figure 14 top panels). It was a great experience for all of our team as they joined us successively (Nicolas Labrosse, Peter Levens (Ph.D. student of Nicolas), Stano Gunár). We observed more than 138 prominences and we confirmed the old results of Véronique Bommier, Sylvie Sahal, and Jean Louis Leroy that the magnetic field in prominences is mainly horizontal (Lopez Ariste 2014).
The high spatial resolution of IRIS allowed us to measure Doppler shifts. Even in quiescent prominences flows could reach 60 to \(70~\mbox{km}\,\mbox{s}^{-1}\) (Schmieder et al., 2013, 2014b). The thesis of Peter Levens in Glasgow was based on these campaigns of observation and focused on the existence of “solar tornadoes” (Levens et al., 2016a, 2016b, 2017).
Many filaments approaching the limb looked like tornadoes when observed in SDO/AIA movies. They appeared to rotate around their axes like tornadoes on Earth. Therefore they were named tornadoes. However, we found their rotation to be very suspicious and that these tornadoes would be better interpreted as the legs of prominences observed from a certain perspective as they cross the limb as demonstrated by a 3D reconstruction of the magnetic field lines for a helical prominence (Schmieder et al., 2017a, 2017b). This topic led to press releases at the Observatoire de Paris,Footnote 1 at IRAP, and at the University of Glasgow in April 2018. In these papers Arturo Lopez Ariste processed the data of THEMIS and concluded that the magnetic field was not vertical as it should be in tornadoes. We continued our collaboration with Petr Heinzel working on the Mg ii line profiles observed with IRIS (Heinzel et al. 2015). We obtained new data in 2017 with the MSDP at the solar tower jointly with IRIS spectra. These lines give strong constraints on radiative-transfer models in 1D and 2D (Ruan et al. 2018).
J.M. Malherbe, S.T. Wu, and myself organized in Paris an IAU symposium on “The nature of prominences and their role in space weather”, IAU S300, in June 2013, dedicated to Einar Tandberg-Hanssen who died in 2011 (Figures 10 and 15). Together we published a book (Schmieder, Malherbe, and Wu 2014). After intensive Team Meetings in Bern, at ISSI, we wrote two important reviews on prominences (Labrosse et al. 2010; Mackay et al. 2010). More recently we got a new ISSI Team project on tornadoes (Figure 14, bottom left panel). We are currently writing a review on tornadoes which should be published soon (Labrosse et al., in preparation).
IAU S300 Symposium on the Nature of prominences and their role in Space Weather in Paris in June 2013 in memory of Einar Tandberg-Hanssen: the participants in the Ecole de Chimie in Paris.
2.6 Flares and CMEs – THEMIS – 2000 – 2020
Since SMM we observed flares during all our multi-wavelength campaigns with the MSDP, either at the Meudon solar tower (1980s), or at Pic du Midi (1990s), and finally with THEMIS after 2000 (Figure 14, top left). I spent nearly two weeks per year on these campaigns with Pierre and Nicole Mein. Always a student accompanied us, e.g., Jean-Marie Malherbe, Pascal Démoulin, Guillaume Aulanier, Yang Guo, Petr Levens. It was very exciting to observe at THEMIS on the top of the mountain (Figure 14 top panels). We were accommodated at the summit and benefited from beautiful sunsets. THEMIS, designed by Jean Rayrole, with his two post-focal instruments, the MTR and the MSDP, was built well after the first designs were made, and their promotors died or retired before THEMIS became fully operational. Therefore the young generation never completely invested its effort in the instrument and many of them left the field. The present director of THEMIS, Bernard Gelly, is still convinced of the importance of THEMIS, i.e. for prominences, which is presently the only magnetograph working on the ground. Gelly is working on the installation of adaptive optics for THEMIS which reopens in 2019. We hope that THEMIS will soon get a second life.
Coming back to the end of the 1990s, I had the pleasure to have Guillaume Aulanier as a Ph.D. student. For his thesis (1998) G. Aulanier developed a linear force-free extrapolation code for filament support. Using his code we showed that the differential shear above the inversion line in an active region induced the formation of a filament low down and that the magnetic field loops progressively become more potential with increasing altitude in the corona (Schmieder et al. 1996a). This way, the importance of 3D magnetic configurations to support prominences and to understand their destabilization was fully demonstrated (Schmieder et al. 1999; Kucera et al. 1999; Aulanier and Schmieder 2002; Dudík et al., 2008, 2012).
With the observations obtained with Yohkoh and the MSDP at Pic du Midi, G. Aulanier and I worked on flare ribbons and flare loops to understand how reconnection in flares can occur (Schmieder et al. 1997). Later joint THEMIS/MSDP observations with SDO allowed us to investigate the physical conditions of the flaring active regions including their magnetic topology (Aulanier, Janvier, and Schmieder 2012; Dalmasse et al. 2015; Joshi et al., 2016, 2019; Zhao et al. 2016) (Figure 17).
Left, eruptive sigmoidal loop in the corona observed by SDO/AIA at 94 Å, middle: reconstruction of the magnetic loop by a non-linear force-free extrapolation, right: electric current measured in the photosphere using SDO/HMI data (Zhao et al. 2016).
In flares the roles of bald patches (Schmieder et al. 1997; Aulanier et al. 1998a; López Ariste et al. 2006), null points (Li et al. 2006; Schmieder et al. 2007a), magnetic twists in flux ropes (van Driel-Gesztelyi et al. 2000; Canou et al. 2009; Török et al. 2009; Guo et al. 2010; Schmieder et al. 2013), emerging flux (Tang et al. 2000; Pariat et al. 2004; Schmieder et al. 2006; Chandra et al. 2009), slipping reconnections (Dudík et al. 2016), and flux rope reconnections (Török et al. 2011) were intensively analyzed in the group.
After working on so many case-studies, G. Aulanier wrote his own MHD simulation code (the Observationally driven High-order scheme Magnetohydrodynamic code – OHM), which allowed him to develop a 3D extension of the flare standard model (Aulanier, Démoulin, and Grappin 2005; Aulanier et al. 2010). He found in his 3D models innovative solutions to explain different signatures of the flares, e.g., flare ribbons, post-flare loops, vortex (Aulanier, Janvier, and Schmieder 2012; Aulanier et al. 2013; Janvier et al. 2014; Zhao et al. 2016; Zuccarello et al. 2017; Dudík et al. 2017) and the causes of flares–CMEs (Schmieder and Aulanier 2012). We approached the topic of electric currents, observations and theory by using OHM to see if there is a net current before flares (Schmieder and Aulanier 2018).
The intuitive sense in physics and fast thinking of G. Aulanier are very important in the group. He is still interested in all observations made on the ground with THEMIS, as well as in space (from Yohkoh to SDO). His high level of knowledge leads him to find unexpected solutions to explain the causes of flares, bright points and eruptions. Therefore he is involved in many collaborations.
Up to now P. Démoulin, G. Aulanier and me make a very good team to supervise Ph.D. students and post-docs in Meudon. I can count nearly 50 papers by which we have been associated during 20 years. Different observational and theoretical aspects of filaments and flares have been treated. I can name the Ph.D. students that we supervised, e.g., Arek Berlicki, Etienne Pariat, Yang Guo, Kelvin Dalmasse on the magnetic topology of flaring active regions. We had and still have today intensive and very productive collaborations with foreign countries, e.g., China (Cheng Fang C., Y. Tang, Li Hui, Yang Guo, Guiping Ruan), India (Gosain Sanjay, Chandra Ramesh, Navin), Argentina (Cristina Mandrini), UK (Lidia van Driel), and the Czech Republic (Petr Heinzel, Jaro Dudik, Stano Gunar, Maciej Zapior) and more recently with individual post-docs, e.g., Stuart Gilchrist, Jie Zhao, Miho Janvier and Francesco Zuccarello.
Our ideas on physical mechanisms for flares, eruptions, and CMEs are summarized in three reviews (Schmieder, Démoulin, and Aulanier 2013; Janvier, Aulanier, and Démoulin 2015; Schmieder, Aulanier, and Vršnak 2015).
3 Space Weather
Beyond the corona in the heliosphere the solar wind is blowing with a velocity of more than \(400~\mbox{km}\,\mbox{s}^{-1}\) where coronal mass ejections and accelerated particles are traveling toward the Earth. The new problem which arises at the beginning of the 21st century is the analysis of their effects on Earth. We have identified aurora borealis, disruptions to the electric power grid, disturbances in telecommunications. We should be able to predict them in the case of extreme events like those observed on other stars.
My first major steps towards Space Weather research were to organize as JOSO president the two SOLSPA conferences in 2000 and 2001 (see Section 2.2) and to be vice president of SCOSTEP from 2007 to 2011. I became vice president of SCOSTEP after serving as IAU representative at the SCOSTEP bureau during ten years (1996 – 2006). I participated in the organization of several General Assemblies, e.g., Longmont, Berlin, Melbourne and in meetings, like in Hokaido during the S-Ramp meeting for the end of the STEP program where I met Ed Cliver and Dave Webb, specialists of extreme events (Figure 8 left panel).
In 2004 the SCOSTEP bureau asked me to form a group with Bob Vincent to define the future program of SCOSTEP and we proposed the Climate and Space Weather of the Sun Earth System (CAWSES) program which was running for eight years (from 2008 to 2016). I discovered that in France we were really pioneers to have such program on the national level, i.e. the PNST (“Programme National Soleil Terre”). I got an award for my services as SCOSTEP vice president in June 2015.
Working on the organization of the science I was also interested to see by myself the causes of magnetospheric disturbances produced by interplanetary coronal mass ejections (ICMEs). I worked in two groups: a French group gathering scientists of different communities and, in Bern (ISSI Teams), a group with Belgian scientists, e.g., Luciano Rodriguez, Stefaan Poedts, Argentinian scientists, e.g., Cristina Mandrini, Sergio Dasso, Hebe Cremades and with the Spanish group of Consuelo Cid. This work was very interesting. It showed to me how difficult it is to find the causes of magnetospheric disturbances. With different techniques there is still an uncertainty of more than ten hours as regards predicting the arrival of ICMEs at the Earth (Dasso et al. 2009; Rodriguez et al. 2009; Cid et al. 2012; Cremades et al. 2015; Bocchialini et al. 2018).
Extreme solar events causing strong disturbances on Earth became a topic of focus because the Kepler satellite registered extreme events on stars similar to the Sun as discovered by the Shibata group (Shibata et al. 2013). Could that happen in the Sun? Guillaume Aulanier used his OHM simulation and the historical frames of the Sun since 1909 kept in the Meudon archives to demonstrate that it could not happen in the present Sun (Aulanier et al. 2013; Schmieder 2018).
4 Conclusion
Extensive progress on the understanding of our Sun has been made during the last 50 years. I realized that our group have been pioneers of many new ideas in different domains. Let me mention some of them: the heating of the corona not by the acoustic waves existing in the photosphere, the evaporation in solar flares explaining bright flare ribbons, the dynamics of prominences (counter-streaming, multi-threads, tornadoes), the filament eruption mass loading of coronal mass ejections, Ellerman bombs and the sea serpentine flux tube as it is crossing the solar surface. Our pioneer ideas were often rediscovered ten years later by other groups when the topic became fashionable. My list of publications in peer reviewed journals contains 280 papers today.
This has been possible because of my concept of research, to combine observations and theory. I created a solar MHD group in Meudon with my previous Ph.D. students. Now we are training many post-docs and students from France and abroad. I am personally invited to many countries to give lectures and advice students. My life was always turned to others: what can I bring to him/her, what can I learn from him or her. It was a continuous exchange and it is why I am traveling to so many countries. During all these years many instruments were developed, in space (SMM, Yohkoh, SOHO, TRACE, Hinode, RHESSI, SDO, IRIS) and on the ground – the French and Italians built a telescope in Tenerife, called THEMIS with a multi-line magnetograph (MTR) and the Multi-Channel Substrative Double Pass (MSDP) spectrograph. Every one of these instruments brought to us new discoveries. THEMIS (1996 – 2016) was a very successful instrument giving specific results that no other instruments can provide, e.g., measuring the magnetic field in prominences. Now the instrument is upgraded with new adaptive optics; let us hope for a new life for it.
For the future, in the horizon of the 2020s, we saw already the launch of the Parker Solar Probe to the Sun, and we soon will see the departure of the Solar Orbiter going also towards the Sun, the first light in the US DKIST solar telescope, and perhaps the construction of EST, the European Solar Telescope, on the ground. I hope that they will also bring about important discoveries on the solar wind, its origin and the processes of the acceleration of particles. Our solar group should get involved in these instruments.
Nowadays international collaborations are even more important than before because astrophysics is a very complex topic, mixing many different physical processes. The new system of post-docs leaving the group after two or three years increases our potential of research but is not as efficient as collaborations with permanent researchers in other countries who can continue to collaborate.
My career was fantastic and is still very lively. I met a lot of friends and worked under wonderful conditions. I was selected in 2010 among 1000 French scientists to be honored by having projected my photo on the Pantheon during the Science Days in Paris (Figure 18, top right panel).
Top left, Award to Brigitte Schmieder (BS) (Officier de la Légion d’Honneur) on June 13, 2012 at the Observatoire de Paris given by Jean Claude Pecker. Our solar team: Pascal Démoulin, Guillaume Aulanier, Miho Janvier, BS, Leon Golub, Etienne Pariat, Kevin Dalmasse, Pierre Mein, top right: BS picture projected on the facade of the Pantheon (1000 best researchers in France). Bottom left: ESPM meeting in Sorrento 2009, champagne for the CNRS position of Etienne Pariat at the Observatory of Paris, BS, Daniel Muller, Stefaan Poedts, bottom right: champagne again in Meudon with my two former Ph.D. students: Etienne Pariat and Guillaume Aulanier for his HDR thesis.
I got the awards of Chevalier and Officier des Palmes académiques in 2010 and the awards of Chevalier and Officier de la Légion d’Honneur in 2012 for my involvement in education and research (Figure 18, top left panel).
I have educated many students (master and Ph.D.) and post-docs in solar physics. We celebrated successes with champagne each time (Figure 18, bottom panels). I apologize that I could not mention all of them. I want to thank all my colleagues from the past and those of today. The ambience is still very friendly and I try to communicate my enthusiasm of the research to my younger colleagues from all over the world (Figure 19). During my thesis research, I had to define the problems to resolve. There was a white page on my desk every day and I had to think during all the day about what to compute and write. Now I have so many questions in solar physics to answer that I have not enough time and people around me to complete the task.
In front of the solar tower of Meudon, the solar group in September 2016: Gherardo Valori, Guillaume Aulanier, Rositsa Miteva, BS, Pascal Démoulin, Kevin Dalmasse, Monique Pick, Marc Linton, Hamish Reid, Etienne Pariat, top right, top of the solar tower with the coelostat in 2015: Eoin Carley, Peter Levens, BS, Francesco Zuccarrello, Stuart Gilchrist. Bottom left, in Meudon 2015: Sophie Musset, Monique Pick, F. Zuccarello, BS, G. Aulanier, E. Carley, Stuart Gilchrist, Carolina Malas-Matamoros, Etienne Pariat, Sophie Masson, bottom right, 2018 Meudon cafeteria, from left to right, Stano Gunar, Miho Janvier, Krysztof Barczynski, F. Zuccarello, Jaro Dudik, N. Vilmer, G. Aulanier, S. Masson, E. Pariat, –, Luis Linan, Guiping Ruan, BS.
I have many other scientific activities as referee of many scientific papers and many proposals (EU, Australian, Belgium FWO). I am a member of the SAF committee (Société Astronomique de France) and animated public events such as eclipses, and the passage of Mercury in front of the Sun. I also like dancing, music, listening to operas, and nature. I like to go to the seashore when it is summer time, play the piano, and grow flowers and enjoy their beauty.
The salary of astronomers is not so high and it was not easy to travel with kids at home but I thank my family for accepting my life as it was. I have fantastic grandchildren whom many of my colleagues know because they accompany me in meetings in different countries (Camille, Adrien, Grégoire, Gautier, Capucine, Baptiste). They are interested in watching the solar eclipses, observing Jupiter and Saturn with a large telescope. The two youngest grandchildren (Clémentine and Margot) hope that it will soon be their turn.
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Schmieder, B. Reminiscences. Sol Phys 294, 53 (2019). https://doi.org/10.1007/s11207-019-1436-4
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DOI: https://doi.org/10.1007/s11207-019-1436-4