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Abstract The acceleration and transport of energetic electrons during solar flares is one of the outstanding topics in solar physics. Recent X-ray and radio imaging and spectroscopy observations have provided diagnostics of the distribution of nonthermal electrons and suggested that, in certain flare events, electrons are primarily accelerated in the loop top and likely experience trapping and/or scattering effects. By combining the focused particle transport equation with magnetohydrodynamic (MHD) simulations of solar flares, we present a macroscopic particle model that naturally incorporates electron acceleration and transport. Our simulation results indicate that physical processes such as turbulent pitch-angle scattering can have important impacts on both electron acceleration in the loop top and transport in the flare loop, and their influences are highly energy-dependent. A spatial-dependent turbulent scattering with enhancement in the loop top can enable both efficient electron acceleration to high energies and transport of abundant electrons to the footpoints. We further generate spatially resolved synthetic hard X-ray (HXR) emission images and spectra, revealing both the loop-top and footpoint HXR sources. Similar to the observations, we show that the footpoint HXR sources are brighter and harder than the loop-top HXR source. We suggest that the macroscopic particle model provides new insights into understanding the connection between the observed loop-top and footpoint nonthermal emission sources by combining the particle model with dynamically evolving MHD simulations of solar flares.
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This content will become publicly available on December 18, 2026
Spatially Resolved Transport Parameters in Solar Flares
Abstract The time profile of solar flare radio emission is often modeled as an injection of energetic particles onto a closed magnetic loop, where they may be trapped by the pinching of field lines and remain for a time before decaying through loss of energy to the background or escaping to the solar surface through the bottom of the loop. These injection, trapping, and precipitation models for energetic particle transport have often been used to explain the characteristics of spatially integrated microwave emissions in solar flares. With the high-cadence imaging spectroscopy capabilities of modern radio instruments, these ideas can be probed with new depth. Radio imaging allows for the selection of particular regions of flares to spatially and temporally isolate individual injections and determine individual decay parameters that could be confused in spatially integrated spectra. Simultaneous spectroscopy allows the fitting of light curves versus frequency for insight into the evolution of the particle energy spectrum and a deeper physical understanding of the decay process. Using currently available time resolution and data quality, injections and decays can be fit simultaneously to the order of 1 s. These considerations motivate the creation of the Pulsed-Injection-Precipitation Decomposition Fitter (PIP_Decomp), which implements an automated method for fitting a series of light curves with injection functions convolved with exponential decays to produce spectrally resolved fit parameters. Herein, PIP_Decomp is introduced and tested by applying it to model flares. Then, PIP_Decomp is used to investigate two relatively simple flares observed by the Expanded Owens Valley Solar Array.
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- Award ID(s):
- 2436999
- PAR ID:
- 10665280
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- The Astrophysical Journal
- Volume:
- 995
- Issue:
- 2
- ISSN:
- 0004-637X
- Page Range / eLocation ID:
- 210
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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