Are non-driven fast-mode shocks responsible for the wide longitudinal spread of SEP events?
Abstract
Fast-mode shock waves are believed to be the primary agent in the acceleration of solar energetic particles (SEPs) over a wide range of energies across the solar corona and heliosphere. In this regard, the spatial distribution of the initial SEP injections from the solar corona should depend on the three-dimensional (3D) geometry of coronal shock waves. Using remote-sensing observations by STEREO-Ahead, -Behind, SDO, and SOHO, we determine the 3D structure and properties of the shock waves initially driven by coronal mass ejections (CMEs). As the shock wave expands, we distinguish two types of shock waves: One is the driven shock wave that is observed in white light observations as propagating ahead of the CME leading edge from the low corona into the interplanetary space. The other is the non-driven shock wave that is observed as a nearly-circular propagating disturbance seen in EUV observations of the low corona (i.e., the so-called EUV wave) and also observed as a halo-shaped disturbance in white light observations far from the eruption site. While the super-Alfvenic CME drivers constantly energize the driven shock waves, and the angular widths are limited to those of the drivers, the non-driven shock waves propagate in a very broad spatial range with deceleration. The magnetic connection of the spacecraft with the different proportions of the shock determines the properties of the observed SEP events. Spacecraft magnetically connected to the non-driven shock will see SEP events with intensities peaking at the prompt component and falling off rapidly. By contrast, spacecraft continuously connecting to driven shock waves will observe SEP events that increase in intensity with time and that may peak at the arrival of the shock. We suggest that the non-driven shock waves propagating far from the eruption site contribute to the broad longitudinal spread of SEPs. Illustrative examples of SEP events observed by STEREO and near-Earth spacecraft and how each spacecraft establishes magnetic connection with the different portions of the shock will be shown.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMSH32A..02K
- 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