Hard X-ray emitting energetic electrons and photospheric electric currents

Abstract

The energy released during solar flares is believed to be stored in non-potential magnetic fields associated with electric currents flowing in the corona. While no measurements of coronal electric currents are presently available, maps of photospheric electric currents can now be derived from SDO/HMI observations. Photospheric electric currents have been shown to be the tracers of the coronal electric currents. Particle acceleration can result from electric fields associated with coronal electric currents. We revisit here some aspects of the relationship between particle acceleration in solar flares and electric currents in the active region. We study the relation between the energetic electron interaction sites in the solar atmosphere, and the magnitudes and changes of vertical electric current densities measured at the photospheric level, during the X2.2 flare on February 15 2011 in AR NOAA 11158. X-ray images from RHESSI are overlaid on magnetic field and electric current density maps calculated from the spectropolarimetric measurements of SDO/HMI using the UNNOFIT inversion and Metcalf disambiguation codes. X-ray images are also compared with EUV images from SDO/AIA to complement the flare analysis. Part of the elongated X-ray emissions from both thermal and non-thermal electrons overlay the elongated narrow current ribbons observed at the photospheric level. A new X-ray source at 50-100 keV (produced by non-thermal electrons) is observed in the course of the flare and is cospatial with a region in which new vertical photospheric currents appeared during the same period (increase of 15%). These observational results are discussed in the context of the scenarios in which magnetic reconnection (and subsequent plasma heating and particle acceleration) occurs at current-carrying layers in the corona.

References in corpus (3)

• Abrupt changes in photospheric magnetic and Lorentz-force vectors during neutral-line flares
• Magnetohydrodynamic Simulation of the X2.2 Solar Flare on 2011 February 15: I. Comparison with the Observations
• Temporal Evolution of the Magnetic Topology of the NOAA Active Region 11158

Cited by in corpus (14)

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• 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
• Flare Energy Release in the Lower Solar Atmosphere Near the Magnetic Field Polarity Inversion Line
• Relationships between Photospheric Vertical Electric Currents and Hard X-Ray Sources in Solar Flares: Statistical Study
• Electric current evolution at the footpoints of solar eruptions
• Solar Active Region Electric Currents Before and During Eruptive Flares
• Successive occurrences of quasi-circular ribbon flares in a fan-spine-like configuration involving hyperbolic flux tube
• Comparative study of electric currents and energetic particle fluxes in a solar flare and Earth magnetospheric substorm
• Electric Currents through J-shaped and Non-J-shaped Flare Ribbons
• Density distribution of photospheric vertical electric currents in flare active regions of the Sun
• Ion Traps at the Sun: Implications for Elemental Fractionation
• Using the Stokes V widths of Fe I lines for diagnostics of the intrinsic solar photospheric magnetic field