Coronal Mass Ejections from the Same Active Region Cluster: Two Different Perspectives

Abstract

The cluster formed by active regions (ARs) NOAA 11121 and 11123, approximately located on the solar central meridian on 11 November 2010, is of great scientific interest. This complex was the site of violent flux emergence and the source of a series of Earth-directed events on the same day. The onset of the events was nearly simultaneously observed by the Atmospheric Imaging Assembly (AIA) telescope onboard the Solar Dynamics Observatory (SDO) and the Extreme-Ultraviolet Imagers (EUVI) on the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite of telescopes onboard the Solar-Terrestrial Relations Observatory (STEREO) twin spacecraft. The progression of these events in the low corona was tracked by the Large Angle Spectroscopic Coronagraphs (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the SECCHI/COR coronagraphs on STEREO. SDO and SOHO imagers provided data from the Earth's perspective, whilst the STEREO twin instruments procured images from the orthogonal directions. This spatial configuration of spacecraft allowed optimum simultaneous observations of the AR cluster and the coronal mass ejections that originated in it. Quadrature coronal observations provided by STEREO revealed many more ejective events than were detected from Earth. Furthermore, joint observations by SDO/AIA and STEREO/SECCHI EUVI of the source region indicate that all events classified by GOES as X-ray flares had an ejective B H. Cremades H. Cremades et al. coronal counterpart in quadrature observations. These results directly affect current space weather forecasting because alarms might be missed when there is a lack of solar observations in a view direction perpendicular to the Sun-Earth line.

Analysis of a long-duration AR throughout five solar rotations: Magnetic properties and ejective events

“…As a consequence, it has been subject of independent, short-term studies that address different aspects and stages of its evolution, e.g. Guo et al (2013); Zuccarello et al (2014); Mandrini et al (2014); Cremades et al (2015). In the latter two articles, AR 11121 is analyzed together with the closely related AR 11123, which emerged within AR 11121 during November 2010.…”

“…The nearly-quadrature observations enabled a better estimation of the ejecta source regions, a sometimes challenging task, in particular for events propagating along the Sun-observer line (halo CMEs) which can lack structure, be diffuse and dim (see e.g. Lara et al 2006;Cremades et al 2015). The location of the AR was decisive to determine which instrument was best to observe the region and its associated eruptive phenomena.…”

“…• Angular width (AW): The AW was measured in the set of coronagraphic images where the CME propagation direction was closer to the corresponding plane of the sky (e.g. Cremades et al, 2015). For completeness, we also consulted the LASCO CME Catalog (Yashiro et al, 2004) and the Computer-Aided CME Tracking catalog (CACTus, Robbrecht and Berghmans 2004).…”

“…comparative CME-production (e.g. Cremades et al 2015;Murray et al 2018), preand post-eruptive coronal magnetic field topology (e.g. Mandrini et al 2014Mandrini et al , 2006Chandra et al 2011Chandra et al , 2017 and magnetic helicity evolution (e.g.…”

Blowout jets and impulsive eruptive flares in a bald-patch topology

“…They recognized that many narrow CMEs may not be listed in the catalog because they are too faint and it is difficult to identify them. Faint CMEs of all widths may be attributed either to a scarcity of material associated with the event or to a significant propagation component away from the observer's plane of the sky (POS) (e.g., Cremades et al 2015).…”