Solar Energetic Particles: Sampling Coronal Abundances |
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Authors: | Donald V Reames |
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Institution: | (1) NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA |
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Abstract: | In the large solar energetic particle (SEP) events, coronal mass ejections (CMEs) drive shock waves out through the corona
that accelerate elements of the ambient material to MeV energies in a fairly democratic, temperature-independent manner. These
events provide the most complete source of information on element abundances in the corona. Relative abundances of 22 elements
from H through Zn display the well-known dependence on the first ionization potential (FIP) that distinguishes coronal and
photospheric material. For most elements, the main abundance variations depend upon the gyrofrequency, and hence on the charge-to-mass
ratio, Q/A, of the ion. Abundance variations in the dominant species, H and He, are not Q/A dependent, presumably because
of non-linear wave-particle interactions of H and He during acceleration. Impulsive flares provide a different sample of material
that confirms the Ne:Mg:Si and He/C abundances in the corona.
This revised version was published online in June 2006 with corrections to the Cover Date. |
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