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the peculiar behavior of halo coronal mass ejections in solar cycle 24We report on the remarkable finding that the halo coronal mass ejections (CMEs) in cycle 24 are more abundant than in cycle 23, although the sunspot number in cycle 24 has dropped by approx. 40%. We also find that the distribution of halo-CME source locations is different in cycle 24: the longitude distribution of halos is much flatter with the number of halos originating at a central meridian distance greater than or equal to 60deg twice as large as that in cycle 23. On the other hand, the average speed and associated soft X-ray flare size are the same in both cycles, suggesting that the ambient medium into which the CMEs are ejected is significantly different. We suggest that both the higher abundance and larger central meridian longitudes of halo CMEs can be explained as a consequence of the diminished total pressure in the heliosphere in cycle 24. The reduced total pressure allows CMEs to expand more than usual making them appear as halos.
Document ID
Document Type
Reprint (Version printed in journal)
Gopalswamy, N.
(NASA Goddard Space Flight Center Greenbelt, MD United States)
Xie, H.
(Catholic Univ. of America Washington, DC, United States)
Akiyama, S.
(Catholic Univ. of America Washington, DC, United States)
Makela, P.
(Catholic Univ. of America Washington, DC, United States)
Yashiro, S.
(Catholic Univ. of America Washington, DC, United States)
Michalek, G.
(Jagiellonian Univ. Cracow, Poland)
Date Acquired
May 5, 2016
Publication Date
May 1, 2015
Publication Information
Publication: The Astrophysical Journal Letters
Volume: 804
Issue: 1
ISSN: 2041-8205
Subject Category
Solar Physics
Report/Patent Number
Funding Number(s)
Distribution Limits
coronal mass ejections