AN INVESTIGATION OF SOLAR FACTORS GOVERNING CORONAL MASS EJECTION CHARACTERISTICS

Abstract

This paper deals with the influence of the distance of the apparent axes of coronal mass ejections (CMEs) from a neutral line (NL) on the source surface and of coronal hole (CH) boundaries upon apparent characteristics of CMEs: e.g., the structure, the velocity of individual features, and the width. (a) It is found that the chance of measuring a CME velocity of ascent appears to decrease with increasing distance from a neutral line or coronal hole. (b) The apparent velocity of a CME appears to depend on the distance of its core from a neutral line or coronal hole boundary. CME speeds for events within 15 deg of a ‘surface’ neutral line are significantly higher than those apparently much farther from ‘surface’ neutral lines. (c) CME spans tend to be wider when they are more closely associated with ‘surface’ neutral lines. It is shown that the contribution of CMEs in the neighbourhood of the NL (the heliomagnetic latitude of the CME apparent axis L < 15 deg) decreases with increasing length of the chain of coronal streamers separating the CH of like polarity of the magnetic field and depends on the character of the relationship between CMEs and other forms of activity. The study revealed a concentration of the apparent axes of CMEs toward zero lines of the photospheric magnetic field from the J. M. Wilcox Solar Observatory at Stanford.