Particle Acceleration in Solar Flares and Associated CME Shocks

Abstract

Observations relating the characteristics of electrons seen near Earth (SEPs) and those producing flare radiation show that in certain (prompt) events the origin of both population appears to be the flare site, which show strong correlation between the number and spectral index of SEP and hard X-ray radiating electrons, but in others(delayed), which are associated with fast CMEs, this relation is complex and SEPs tend to be harder. Prompt event spectral relation disagrees with that expected in thick or thin target models. We show that using a a more accurate treatment of the transport of the accelerated electrons to the footpoints and to the Earth can account for this discrepancy. Our results are consistent with those found by Chen and Petrosian (2013) for two flares using non-parametric inversion methods, according to which we have weak diffusion conditions, and trapping mediated by magnetic field convergence. The weaker correlations and harder spectra of delayed events can come about by re-acceleration of electrons in the CME shock environment. We describe under what conditions such a hardening can be achieved. Using this (acceleration at the flare and re-acceleration in the CME) scenario we show that we can describe the similar dichotomy that exists between the so called impulsive, highly enriched (${}^3$He and heavy ions) and softer SEP events, and stronger more gradual SEP events with near normal ionic abundances and harder spectra. These methods can be used to distinguish the acceleration mechanisms and to constrain their characteristics.

26 pages, 10 figures, ApJ in press

References in corpus (5)

• Double Coronal Hard and Soft X-ray Source Observed by RHESSI: Evidence for Magnetic Reconnection and Particle Acceleration in Solar Flares
• First detection of >100 MeV gamma rays associated with a behind-the-limb solar flare
• Variations in Abundance Enhancements in Impulsive Solar Energetic-Particle Events and Related CMEs and Flares
• Relative Spectra and Distributions of Fluences of 3He and 4He in Solar Energetic Particles
• Acceleration of Thermal Protons By Generic Phenomenological Mechanisms

Cited by in corpus (16)

• Characteristics of Sustained >100 MeV Gamma-ray Emission Associated with Solar Flares
• Fermi-LAT Observations of High-energy Behind-the-limb Solar Flares
• Recent Progress on Particle Acceleration and Reconnection Physics during Magnetic Reconnectionin the Magnetically-dominated Relativistic Regime
• Probing the Puzzle of Behind-the-Limb $\gamma$-ray Flares: Data-driven Simulations of Magnetic Connectivity and CME-driven Shock Evolution
• Sources of Solar Energetic Particles
• Evidence for a Coronal Shock Wave Origin for Relativistic Protons Producing Solar Gamma-Rays and Observed by Neutron Monitors at Earth
• Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra
• Statistical results for solar energetic electron spectra observed over 12 years with STEREO/SEPT
• Multiple injections of energetic electrons associated with the flare/CME event on 9 October 2021
• Connecting solar flare hard X-ray spectra to in situ electron spectra. A comparison of RHESSI and STEREO/SEPT observations
• The Relation Between Escape and Scattering Times of Energetic Particles in a Turbulent Magnetized Plasma: Application to Solar Flares
• Effect of acceleration and escape of energetic particles on spectral steepening at shocks
• Electromagnetic Emission Produced by Three-wave Interactions in a Plasma with Continiously Injected Counterstreaming Electron Beams
• Implications of loop-top origin for microwave, hard X-ray, and low-energy gamma-ray emissions from behind the limb flares
• Modeling Hadronic Gamma-ray Emissions from Solar Flares and Prospects for Detecting Non-thermal Signatures from Protostars
• Energetic particle acceleration and transport with the novel Icarus$+$PARADISE model