Return currents and energy transport in the solar flaring atmosphere

Abstract

According to a standard ohmic perspective, the injection of accelerated electrons into the flaring region violates local charge equilibrium and therefore, in response, return currents are driven by an electric field to equilibrate such charge violation. In this framework, the energy loss rate associated to these local currents has an ohmic nature and significantly shortens the acceleration electron path. In the present paper we adopt a different viewpoint and, specifically, we study the impact of the background drift velocity on the energy loss rate of accelerated electrons in solar flares. We first utilize the Rutherford cross-section to derive the formula of the energy loss rate when the collisional target has a finite temperature and the background instantaneously and coherently moves up to equilibrate the electron injection. We then use the continuity equation for electrons and imaging spectroscopy data provided by RHESSI to validate this model. Specifically, we show that this new formula for the energy loss rate provides a better fit of the experimental data with respect to the model based on the effects of standard ohmic return currents.

Submitted to The Astrophysical Journal

References in corpus (4)

• Properties of the Acceleration Regions in Several Loop-structured Solar Flares
• Determination of the Acceleration Region Size in a Loop-structured Solar Flare
• The Specific Acceleration Rate in Loop-structured Solar Flares -- Implications for Electron Acceleration Models
• Fast Spectral Fitting of Hard X-Ray Bremsstrahlung from Truncated Power-Law Electron Spectra

Cited by in corpus (7)

• Suppression of parallel transport in turbulent magnetized plasmas and its impact on non-thermal and thermal aspects of solar flares
• Determination of Stochastic Acceleration Model Characteristics in Solar Flares
• Understanding breaks in solar flares x-ray spectra: Evaluation of a co-spatial return-current model
• Role of Suprathermal Runaway Electrons Returning to the Acceleration Region in Solar Flares
• Energy Deposition by Energetic Electrons in a Diffusive Collisional Transport Model
• Onset of Electron Acceleration in a Flare Loop
• Interplay of Boltzmann equation and continuity equation for accelerated electrons in solar flares