Coronal Transient Events During Two Solar Minima: Their Solar Source Regions and Interplanetary Counterparts

Abstract

In the frame of two coordinated observational and research efforts, two full solar rotations were investigated in the times of two distinct solar minima. These two campaigns were dubbed Whole Sun Month (WSM; 10 August – 8 September 1996) and Whole Heliosphere Interval (WHI; 20 March – 16 April 2008). The nearly uninterrupted gathering of solar coronal data since the beginning of the Solar and Heliospheric Observatory (SOHO) era offers the exceptional possibility of comparing two solar minima for the first time, with regard to the coronal transient aspect. This study characterizes the variety of outward-traveling transients observed in the solar corona during both time intervals, from very narrow jet-like events to coronal mass ejections (CMEs). Their solar source regions and ensuing interplanetary structures were identified and characterized as well, toward a global-scale description of their role in determining the heliosphere’s conditions. Multi-wavelength images provided by the space missions SOHO, Yohkoh (only WSM), and Solar-Terrestrial Relations Observatory (STEREO; only WHI) and ground-based observatories were analyzed for coronal ejecta and their solar sources, while data registered by the Advanced Composition Explorer (ACE) spacecraft were inspected for interplanetary CMEs and magnetic clouds. Notable differences arise from the analysis of the detailed survey of events: more (fewer) ejecta during WHI (WSM), 12% (40%) were produced by active regions during WHI (WSM), and nearly no (high) deflection from the radial direction was observed during WHI (WSM). Instrumental aspects such as dissimilar resolution, cadence, and fields of view are considered in order to discern instrumentally driven disparities from inherent differences between solar minima.