Determination of the total accelerated electron rate and power using solar flare hard X-ray spectra

Abstract

Solar flare hard X-ray spectroscopy serves as a key diagnostic of the accelerated electron spectrum. However, the standard approach using the collisional cold thick-target model poorly constrains the lower-energy part of the accelerated electron spectrum, and hence the overall energetics of the accelerated electrons are typically constrained only to within one or two orders of magnitude. Here we develop and apply a physically self-consistent warm-target approach which involves the use of both hard X-ray spectroscopy and imaging data. The approach allows an accurate determination of the electron distribution low-energy cutoff, and hence the electron acceleration rate and the contribution of accelerated electrons to the total energy released, by constraining the coronal plasma parameters. Using a solar flare observed in X-rays by the {\em RHESSI} spacecraft, we demonstrate that using the standard cold-target methodology, the low-energy cutoff (and hence the energy content in electrons) is essentially undetermined. However, the warm-target methodology can determine the low-energy electron cutoff with $\sim$7\% uncertainty at the $3\sigma$ level and hence permits an accurate quantitative study of the importance of accelerated electrons in solar flare energetics.

arXiv commentAccepted for publication in the Astrophysical Journal, 18 pages, 5 figures

References in corpus (22)

• Global Energetics of Thirty-Eight Large Solar Eruptive Events
• Implications of X-ray Observations for Electron Acceleration and Propagation in Solar Flares
• Deducing Electron Properties From Hard X-Ray Observations
• Global Energetics of Solar Flares: V. Energy Closure in Flares and Coronal Mass Ejections
• Looptop Hard X-Ray Emission in Solar Flares: Images and Statistics
• The Formation of Kappa-Distribution Accelerated Electron Populations in Solar Flares
• Compton backscattered and primary X-rays from solar flares: angle dependent Green's function correction for photospheric albedo
• Chromospheric magnetic field and density structure measurements using hard X-rays in a flaring coronal loop
• Global Energetics of Solar Flares: III. Non thermal Energies
• Kappa distribution and hard X-ray emission of solar flares
• Collisional relaxation of electrons in a warm plasma and accelerated nonthermal electron spectra in solar flares
• Wave-particle interactions in non-uniform plasma and the interpretation of Hard X-ray spectra in solar flares
• On the variation of solar flare coronal x-ray source sizes with energy
• Estimating the properties of hard X-ray solar flares by constraining model parameters
• Multi-thermal representation of the kappa-distribution of solar flare electrons and application to simultaneous X-ray and EUV observations
• Understanding breaks in solar flares x-ray spectra: Evaluation of a co-spatial return-current model
• Particle Acceleration in Solar Flares and Associated CME Shocks
• The role of diffusion in the transport of energetic electrons during solar flares
• Solar Flare Composition and Thermodynamics from RESIK X-ray Spectra
• Statistically-derived flaring chromospheric-coronal density structure from non-thermal X-ray observations of the Sun
• Fast electron slowing-down and diffusion in a high temperature coronal X-ray source
• High-temperature differential emission measure and altitude variations in the temperature and density of solar flare coronal X-ray sources

Cited by in corpus (19)

• Accelerated electrons observed down to <7 keV in a NuSTAR solar microflare
• Thermal-nonthermal energy partition in solar flares derived from X-ray, EUV, and bolometric observations
• Energetic Electron Distribution of the Coronal Acceleration Region: First results from Joint Microwave and Hard X-ray Imaging Spectroscopy
• STIX X-ray microflare observations during the Solar Orbiter commissioning phase
• Global Energetics of Solar Flares: VIII. The Low-Energy Cutoff
• The Role of Energy Diffusion in the Deposition of Energetic Electron Energy in Solar and Stellar Flares
• Probing solar flare accelerated electron distributions with prospective X-ray polarimetry missions
• Forward modelling of particle acceleration and transport in an individual solar flare
• FOXSI-2 Solar Microflares II: Hard X-ray Imaging Spectroscopy and Flare Energetics
• Spatio-temporal energy partitioning in a non-thermally dominated two-loop solar flare
• The Multi-Instrument (EVE-RHESSI) DEM for Solar Flares, and Implications for Non-Thermal Emission
• Energy budget of plasma motions, heating, and electron acceleration in a three-loop solar flare
• A Very Narrow RHESSI X-ray Flare on 25 September 2011
• Spectral and Imaging Diagnostics of Spatially-Extended Turbulent Electron Acceleration and Transport in Solar Flares
• The efficiency of electron acceleration during the impulsive phase of a solar flare
• Particle acceleration and their escape into the heliosphere in solar flares with open magnetic field
• Solar Gamma-Ray Evidence for a Distinct Population of $>$ 1 MeV Flare-Accelerated Electrons
• Flare-accelerated Electrons in the Kappa Distribution from X-Ray Spectra with the Warm-Target Model
• Energy-Containing Electrons in Solar Flares: Improving Hard X-Ray and EUV Diagnostics