Solar Energetic Particle Acceleration at a Spherical Shock with the Shock Normal Angle ${\theta }_{B_n}$ Evolving in Space and Time

Abstract

We present a 2D kinematic model to study the acceleration of solar energetic particles (SEPs) at a shock driven by a coronal mass ejection. The shock is assumed to be spherical about an origin that is offset from the center of the Sun. This leads to a spatial and temporal evolution of the angle between the magnetic field and shock normal direction (${\theta }_{Bn}$) as it propagates through the Parker spiral magnetic field from the lower corona to 1 AU. We find that the high-energy SEP intensity varies significantly along the shock front due to the evolution of ${\theta }_{Bn}$. Generally, the west flank of the shock preferentially accelerates particles to high energies compared to the east flank and shock nose. This can be understood in terms of the rate of acceleration, which is higher at the west flank. Double power-law energy spectra are reproduced in our model as a consequence of the local acceleration and transport effects. These results will help better understand the evolution of SEP acceleration and provide new insights into large SEP events observed by multi-spacecraft, especially those close to the Sun, such as Parker Solar Probe and Solar Orbiter.

References in corpus (3)

• The acceleration of high-energy protons at coronal shocks: the effect of large-scale streamer-like magnetic field structures
• Galactic Cosmic-Ray Propagation in the Inner Heliosphere: Improved Force-Field Model
• On the Conservation of Turbulence Energy in Turbulence Transport Models

Cited by in corpus (5)

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• Shock and SEP Modeling Study for the 5 September 2022 SEP Event
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• Radial Evolution of ICME-Associated Particle Acceleration Observed by Solar Orbiter and ACE
• Probing Solar Wind Structures with Solar Energetic Particle Observations from Solar Orbiter