Flares Particle Acceleration Near the Sun and Contribution to Large SEP Events

Team Chair: Glenn Mason
Next Team Meeting: October 25-26, 2009, University of New Hampshire
Team-Maintained Web Site:
Team Publications: Annual Report: 2008-2009, Annual Report: 2009-2010
Team Members:

Target Description: Recent studies have shown that energetic particles accelerated during solar flares could make direct and significant contributions above tens of MeV during some large SEP events observed at Earth. However, the basic mechanisms by which particles are accelerated to such high energies in flares are not well understood. Uncertainties in comparing the timing of various forms of solar activity, as well as scattering uncertainties in the inner heliosphere, has made it difficult to assess the relative contribution of flares to any given large SEP event. To understand and predict solar particle radiation near the Earth and in the heliosphere requires a cross-disciplinary approach from the solar and heliospheric communities. Specifically, it is necessary to utilize remote and in situ observations of solar flares and SEP events to test and improve existing analytic and numerical models of particle acceleration in solar flares.

Goals and measures of success: The goal of this topic is to combine theoretical studies, numerical simulations, and remote and in situ observations to understand the basic mechanisms by which particles are accelerated to >50 MeV energy in solar flares. The measure of success, and the criterion for proposal selection, is the potential impact of the work in quantifying the limits of various particle mechanisms (e.g, magnetic reconnection, parallel electric-fields, shocks, second-order Fermi acceleration, etc.,), and in determining if the flare-accelerated ions could also make direct and significant contributions to the large gradual SEP events observed at Earth.

Types of solicited investigations: Proposals that contribute to our fundamental understanding of the energization and escape of particles accelerated during solar flares using either observations or theoretical analysis are encouraged. Observational studies that seek to characterize the solar origin and key properties (e.g., ion composition, electron association, electromagnetic emission) of SEP events at Earth using remote and in situ measurements are also relevant. Analytical and numerical models that seek to predict the energy extent, the observed ion composition i.e., the enhancements in 3He, heavy and ultra-heavy ions, and the associated spectral forms, are also encouraged. Proposals that seek to quantitatively test the predictions of various numerical and analytical models and determine the relative contributions of flare-accelerated ions to large gradual SEP events are highly relevant. Proposals that combine existing datasets or numerical models with relevant datasets from upcoming missions like STEREO, SDO, and Solar-B are also encouraged.