Temperature of the Source Plasma for Impulsive Solar Energetic Particles

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.

17 pages, 9 figures, accepted by Solar Physics

References in corpus (5)

• The Two Sources of Solar Energetic Particles
• Element Abundances in Solar Energetic Particles and the Solar Corona
• Abundance Enhancements in Impulsive Solar Energetic-Particle Events with Associated Coronal Mass Ejections
• Variations in Abundance Enhancements in Impulsive Solar Energetic-Particle Events and Related CMEs and Flares
• The Onset of Ion Heating During Magnetic Reconnection with a Strong Guide Field

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• Temperature in Solar Sources of 3He-rich Solar Energetic Particles and Relation to Ion Abundances
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