Earth-arrival of Coronal Mass Ejections originating from close to the Solar Disk Center
Abstract
Not all coronal mass ejections (CMEs) that originate from close to the solar disk center arrive at Earth due to various reasons. In order to find the fraction of CMEs that do reach Earth, we investigated a set of wide CMEs (width ∼ 60 degrees) originating from close to the disk center (Central Meridian Distance < 30 degrees). Seventy such CMEs were identified in 2011 using SOHO and STEREO coronagraphs and heliospheric imagers. The solar sources of these CMEs were confirmed to be close to the disk center using images from the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). We found that only about a third of the disk-center CMEs arrived at Earth. We examined the possible reasons for the non-arrival of the remaining CMEs and found that 1) 31% of CMEs faded out before reaching Earth, 2) 27% were captured by following faster CMEs, and 3) 7% of CMEs left the ecliptic plane. The faded-out CMEs became invisible in STEREO/COR1 (32%), COR2 (32%), or HI1 (36%) fields of view. We also investigated the geoeffectiveness of the Earth-arriving CMEs and found that only 17% (4/22) of them produced at least a moderate geomagnetic storm (Dst index < -50 nT). The Dst index of the largest geomagnetic storms in our data set was -72 nT. In 2011 there were 3 intense geomagnetic storms (Dst Index < -100 nT), but all of them were produced by non-disk center CMEs and hence they are not in our sample. We also found that the Earth-arriving CMEs are faster than the fading-out CMEs ( 700 km/s vs. 300 km/s) from COR1 to COR2 FOVs. We conclude that only a tiny fraction of wide CMEs originating from the disk center are geoeffective (4/70 or 6%). In the future work, we are planning to expand study period to increase the sample size.
- Publication:
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Solar Heliospheric and INterplanetary Environment (SHINE 2015)
- Pub Date:
- July 2015
- Bibcode:
- 2015shin.confE..97A