Stochastic particle acceleration by helical turbulence in solar flares

Gregory Fleishman, Igor N. Toptygin

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Flaring release ofmagnetic energy in solar corona is only possible if the magnetic field deviates from a potential one. We show that the linear magnetohydrodynamic (MHD) modes excited on top of the non-potential magnetic field possess a non-zero kinetic helicity. Accordingly, this necessarily results in a noticeable kinetic helicity of the turbulence, composed of these linear modes with various scales and random phases, generated at the flare site by the primary energy release, which may be important for many applications. In particular, a non-zero turbulence helicity has a potentially strong effect on the particle acceleration because the helical component of the turbulence induces a mean regular large-scale (DC) electric field capable of directly accelerating the charged particles in addition to the commonly considered stochastic turbulent electric field. In this paper, we derive the kinetic helicity density of the linear MHD modes excited on top of a twisted large-scale magnetic field, estimate the corresponding turbulence helicity and take its effect on stochastic particle acceleration by the turbulence into consideration; in particular, we compare this induced mean electric field with the electron and estimated effective ion Dreicer fields. We have discovered that this, so far missing but highly important, ingredient of the turbulence at the flare site can be responsible for the thermal-to-non-thermal energy partition in flares by controlling the process of particle extraction from the thermal pool and formation of the seed particle population to be then stochastically accelerated to higher energies. In addition, it is naturally consistent with such puzzling flare manifestations as spatial separation of electron and proton emission sites, electron beam formation, and enrichment of the accelerated particle population by 3He and other rare ions.

Original languageEnglish (US)
Pages (from-to)2515-2526
Number of pages12
JournalMonthly Notices of the Royal Astronomical Society
Issue number3
StatePublished - Mar 1 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


  • Acceleration of particles
  • Diffusion
  • Magnetic fields
  • Sun: Radio radiation
  • Sun: flares
  • Turbulence


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