Can a halo CME from the limb be geoeffective?

Abstract

[1] The probability for a halo coronal mass ejection (CME) to be geoeffective is assumed to be higher the closer the CME launch site is located to the solar central meridian. However, events far from the central meridian may produce severe geomagnetic storms, like the case in April 2000. In this work, we study the possible geoeffectiveness of full halo CMEs with the source region situated at solar limb. For this task, we select all limb full halo (LFH) CMEs that occurred during solar cycle 23, and we search for signatures of geoeffectiveness between 1 and 5 days after the first appearance of each CME in the LASCO C2 field of view. When signatures of geomagnetic activity are observed in the selected time window, interplanetary data are carefully analyzed in order to look for the cause of the geomagnetic disturbance. Finally, a possible association between geoeffective interplanetary signatures and every LFH CME in solar cycle 23 is checked in order to decide on the CME's geoeffectiveness. After a detailed analysis of solar, interplanetary, and geomagnetic data, we conclude that of the 25 investigated events, there are only four geoeffective LFH CMEs, all coming from the west limb. The geoeffectiveness of these events seems to be moderate, turning to intense in two of them as a result of cumulative effects from previous mass ejections. We conclude that ejections from solar locations close to the west limb should be considered in space weather, at least as sources of moderate disturbances.

Short-term variability of the Sun-Earth system: an overview of progress made during the CAWSES-II period

“…The primary link between a geomagnetic storm and a CME is the out of the ecliptic component (Bz) of the interplanetary magnetic field (Gonzalez et al, 1994;Zhang et al 2007;Gopalswamy 2008;Echer et al 2008aEcher et al , 2008bEcher et al , 2013Cid et al 2012). Echer et al (2008a) conclusively showed that for all 90 major (Dst < −100 nT) storms that occurred during cycle 23, it was the Bz component that was responsible for the storms (some people have thought that it was possible that the IMF By component was also important).…”

Flare-CME Models: An Observational Perspective (Invited Review)

“…Halo CMEs are commonly associated with energetic flares and are frequently geoeffective. However, we note that halo CMEs launched from regions close to the solar limb during Solar Cycle 23 were never very geoeffective (Cid et al, 2012). To be strongly geoeffective, the CME source has to be close to the central meridian.…”

The Physical Processes of CME/ICME Evolution

“…According to study by Gopalswamy et al (2009b), almost ten percent of large geospace storms are caused by CMEs that originate close to the limb of the Sun. In such cases, the ICME sheath is typically the primary driver of the storm (see also Huttunen et al 2002), but cases have been reported where clear ejecta signatures upstream of the Earth and geomagnetic activity have been associated with limb CMEs (e.g., Schwenn et al 2005;Cid et al 2012;. For example, the CME studied by was initially heading toward the STEREO-B, but it deflected in the heliosphere and arrived at the Earth instead, which was located about 35°away from the STEREO-B at that time.…”