Relationships between Photospheric Vertical Electric Currents and Hard X-Ray Sources in Solar Flares: Statistical Study

Abstract

There are still debates whether particle acceleration in solar flares may occur due to interruption of electric currents flowing along magnetic loops. To contribute to this problem, we performed the first statistical study of relationships between flare hard X-ray (HXR; $50-100$ keV) sources observed by the \textit{Ramaty High-Energy Solar Spectroscopic Imager} (RHESSI) and photospheric vertical electric currents (PVECs, $j_r$) calculated using vector magnetograms obtained with the Helioseismic and Magnetic Imager (HMI) on-board the \textit{Solar Dynamics Observatory} (SDO). A sample of 48 flares, from C3.0 to X3.1 class, observed in central part of the solar disk by both instruments in 2010--2015 was analyzed. We found that $\approx 70$\% of all HXR sources overlapped with islands or ribbons of enhanced ($\left|j_r\right|\gtrsim 10^4$ statampere~cm${}^{-2}$) PVECs. However, less than $\approx 40$\% of the HXR sources overlapped with PVEC maxima, with an accuracy of $\pm 3^{\prime \prime }$. More than in half of the flares there were HXR sources outside regions of enhanced PVECs. We found no correlation between intensity of the HXR sources and PVEC density or total PVEC under them. No systematic dissipation of PVECs under the HXR sources was found during the flares. Collectively, the results do not support the current-interruption flare models. However, the results indicate the importance of the presence of longitudinal currents in flare regions. Understanding of their specific role in the processes of energy release, plasma heating, and acceleration of particles requires further investigation.

arXiv comment56 pages, 21 figures, accepted in ApJ

References in corpus (18)

• An Observational Overview of Solar Flares
• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: SHARPs -- Space-weather HMI Active Region Patches
• The Helioseismic and Magnetic Imager (HMI) Vector Magnetic Field Pipeline: Overview and Performance
• Evolution of Magnetic Field and Energy in A Major Eruptive Active Region Based on SDO/HMI Observation
• Imaging coronal magnetic-field reconnection in a solar flare
• Electric current in flares ribbons: observations and 3D standard model
• Evolution of Flare Ribbons, Electric Currents and Quasi-separatrix Layers During an X-class Flare
• Investigating the Magnetic Imprints of Major Solar Eruptions with SDO/HMI High-Cadence Vector Magnetograms
• A spatio-temporal description of the abrupt changes in the photospheric magnetic and Lorentz-force vectors during the 2011 February 15 X2.2 flare
• Fine structure of flare ribbons and evolution of electric currents
• Spatio-temporal dynamics of sources of hard X-ray pulsations in solar flares
• The nonpotentiality of coronae of solar active regions, the dynamics of the surface magnetic field, and the potential for large flares
• Hard X-ray emitting energetic electrons and photospheric electric currents
• Dynamics of Electric Currents, Magnetic Field Topology and Helioseismic Response of a Solar Flare
• Energy Release and Initiation of Sunquake in C-class Flare
• A Compressed Sensing-based Image Reconstruction Algorithm for Solar Flare X-Ray Observations
• Magnetic structure of solar flare regions producing hard X-ray pulsations
• Solar Active Region Electric Currents Before and During Eruptive Flares

Cited by in corpus (4)

• Flare Energy Release at the Magnetic Field Polarity Inversion Line During M1.2 Solar Flare of 2015 March 15. II. Investigation of Photospheric Electric Current and Magnetic Field Variations Using HMI 135-second Vector Magnetograms
• Properties and Energetics of Magnetic Reconnection: I. Evolution of Flare Ribbons
• Comparative study of electric currents and energetic particle fluxes in a solar flare and Earth magnetospheric substorm
• Solar and stellar flares: frequency, active regions and stellar dynamo