Large-Scale Magnetic Structures Responsible for Coronal Disturbances

Abstract

In the first part of our communication, in a short summary of our recent results, it is demonstrated that over the last 15 years (the time interval for which the magnetic synoptic charts are available) the largest solar activity, usually connected with proton-flare occurrence, has been very closely related to a characteristic large-scale pattern in the magnetic field distribution with a life-time of the order of 8–10 solar rotations. These regular features are seen in the negative as well as in the positive polarity, although they can be seen better in the negative polarity where their forms are more pronounced, regardless of the activity cycle. The form alternates with the location in the northern or the southern solar hemispheres due to the mutual relations of both polarities, individual active regions, the influence of the differential rotations, the shift in longitude, etc. This pattern could be observed up to the large August 1972 proton-flare activity.

The large-scale magnetic patterns described are accompanied by characteristic large-scale features in the green (λ5303) coronal emission, presented in the form of isophotes on the synoptic charts (reduced to a unified photometric scale).

In the second part of the presentation, preliminary results, concerning the correlation of the longitudinal distribution of the green coronal emission with the negative and the positive polarity fields for two time intervals (August 1960–September 1961 and January 1969–December 1969) are described. The existence of two ‘coronal active longitudes’ in both intervals, as well as the close relation of these longitudinal emission maxima to certain parts of the large-scale characteristic bodies of negative polarity, is discussed. Also, the existence of one heliographic longitude, connected with ‘coronal holes’ (minimal green corona emission), and its relation to the positive polarity large-scale pattern are proved.