Early-Stage Acceleration of SEPs by CME-Driven Shocks and Compressions
Abstract
Most Coronal Mass Ejections (CMEs) exhibit a typical three-stage kinematic profile from their onset until about 5 Rs. It consists of an initial relatively slow onset very low in the corona, followed by a period of rapid acceleration and expansion, and a final period when their speed adjusts to the surrounding solar wind speed and their expansion slows down. Most of the Solar Energetic Particle (SEP) acceleration associated with the CME evolution is expected to occur during these three stages, especially the second one, when CMEs may drive plasma pile-up compressions and shocks. However, the lack of in situ observations near the Sun requires the use of indirect methods for constraining the acceleration. We review recent techniques for assessing the SEP acceleration efficiency of early-stage CME-driven compressive waves. The relevant parameters may be obtained from EUV, white light, and radio observations in combination with models for the coronal magnetic field, plasma density and temperature. EUV imaging with the Atmospheric Imaging Assembly (AIA) instrument on the Solar Dynamics Observatory spacecraft has proven particularly useful for detecting large-scale short-lived coronal bright fronts. We have take a further step, and applied analytic and numerical models of diffusive shock acceleration of protons in several large-scale plasma compressive fronts. We present the modeling results of acceleration efficiency and extent in this dynamic region near the Sun, for several cases of CME kinematic profiles, and demonstrate in detail the intimate connection between SEP production and compression/shock evolution. Comprehensive understanding of where and when CMEs accelerate SEPs is important for constraining the heliospheric populations and to improve the mitigation of space radiation; understanding CME-driven shock acceleration near the Sun is a crucial piece of this puzzle.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH32A..01K
- Keywords:
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- 7509 Corona;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7513 Coronal mass ejections;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7514 Energetic particles;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMYDE: 7524 Magnetic fields;
- SOLAR PHYSICS;
- ASTROPHYSICS;
- AND ASTRONOMY