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arXiv · 1505.02741

Temperature of the Source Plasma for Impulsive Solar Energetic Particles

Donald V. Reames·Edward W. Cliver·Stephen W. Kahler
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Abstract

The steep power-law dependence of element abundance enhancements on the mass-to-charge ratios [A/Q] of the ions in impulsive solar energetic-particle (SEP) events causes these enhancements to reflect the temperature-dependent pattern of Q of the ions in the source plasma. We searched for SEP events from coronal plasma that is hotter or cooler than the limited region of 2.5 - 3.2 MK previously found to dominate 111 impulsive SEP events. Fifteen new events were found, four (three) originated in 2-MK (4-MK) plasma, but none from outside this temperature range. Although the impulsive SEP events are strongly associated with flares, this result indicates that these ions are not accelerated from flare-heated plasma, which can often exceed 10 MK. Evidently the ions of 2 - 20 MeV/amu that we observe in space are accelerated from active-region plasma on open magnetic-field lines near the flare, but not from the closed loops of the flare. The power-law dependence of the abundance enhancements on A/Q of the ions is expected from theoretical models of acceleration from regions of magnetic reconnection.

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Donald V. Reames, Edward W. Cliver, Stephen W. Kahler. 2015-05-11. Temperature of the Source Plasma for Impulsive Solar Energetic Particles. https://doi.org/10.1007/s11207-015-0711-2

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