Electron Acceleration and the Development of Power-Law Energy Spectra in Magnetic Reconnection with A Force-free Current Sheet

Jul 8, 2021, 5:44 PM


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Working Group 2: Particle acceleration Working Group 2: Particle acceleration


Haihong Che (University of Alabama in Huntsville)


Extensive observations have discovered that a huge number of energetic electrons with energy up to MeV (~0.9c and Lorentz factor ~2) are produced during solar flares. These very mild relativistic energetic electrons demonstrate two-stage power-law spectral evolutions. What mechanism efficiently accelerates non-relativistic particles to a power-law has been a long-standing “ injection problem” in particle acceleration theory since Fermi first proposed his famous Fermi-acceleration model in 1949. In this talk, I will discuss why particle acceleration in solar flares is an “injection problem” and what problems are with the previous and current widely invoked models. I will present a new acceleration mechanism in magnetic reconnection. I will show how the velocity shear stored naturally in force-free currents drives an electron Kevin-helmholtz instability (EKHI) during magnetic reconnection and efficiently acceleration electrons to a power-law energy spectrum via a two-stage soft-hard-hard evolution. Finally, I will discuss the potentially broad application of this mechanism in solar physics and how the complexity of solar flares may impact the further development of this model.

Primary author

Haihong Che (University of Alabama in Huntsville)


Dr G. P. Zank (University of Alabama in Huntsville) Dr A. O. Benz (University of Applied Sciences and Arts Northwestern Switzerland, CH-5210 Windisch, Switzerland)

Presentation materials