Particle Acceleration by Induced Electric Fields in Course of Electric Current Oscillations in Coronal Magnetic Loops
A mechanism for acceleration of electrons driven by the oscillations of the electric current in solar magnetic loops is considered. The magnetic loop is presented as an equivalent RLC-circuit with the electric current generated by convective motions in the photosphere. Eigen oscillations of the current in a loop induce the electric field directed along to the loop axis. It is shown that pulsating type III bursts and the sudden reductions that occur in the course of type IV continuum in solar flares provide evidence for acceleration and storage of energetic electrons in the coronal magnetic loops. Energization rate of electrons accelerated by sub-Dreicer electric field are determined. The energy spectra of fast electrons under both intermediate and strong regimes of pitch-angle diffusion are discussed. Two examples of the electron acceleration in the pulsating type III solar bursts are considered. We also discuss the efficiency of suggested mechanism as compared with the electron acceleration during 5-min photospheric oscillations and with the acceleration driven by the magnetic Rayleigh-Taylor instability.
This work was supported by the Russian Science Foundation grants no. 16-12-10448 (sections 1, 2), no. 16-12-10528 (sections 5,6), and grants RFBR no. 17-02-00091a (section 4), and no. 18-02-00856a (section 3), as well as the RAS Program no. 28.
- 3.Bespalov, P.A. and Trakhtengerts, V.Yu., Cyclotron instability of the Earth radiation belts, in Reviews of Plasma Physics, Leontovich, M.A., Ed., New York: Plenum, 1986, vol. 10, pp. 155–293.Google Scholar
- 10.Kliem, B., Karlický, M., and Benz, A., Solar flare radio pulsations as a signature of dynamic magnetic reconnection, Astron. Astrophys., 2000, vol. 360, pp. 715–728.Google Scholar
- 12.Kuijpers, J., Pulsed acceleration in solar flares, Astron. Astrophys., 1978, vol. 69, pp. L9–L12.Google Scholar
- 14.Landau, L.D. and Lifshitz, E.M., Electrodynamics of Continuous Media, Elmsford: Pergamon, 1984.Google Scholar
- 15.Lin, R.P., Krucker, S., Hurford, G.J., Smith, D.M., Hudson, H.S., Holman, G.D., Schwartz, R.A., Dennis, B.R., Share, G.H., Murphy, R.J., Emslie, A.G., Johns-Krull, C., and Vilmer, N., RHESSI observations of particle acceleration and energy release in an intense solar gamma-ray line flare, Astrophys. J., 2003, vol. 595, pp. L69–L76.CrossRefGoogle Scholar
- 21.Zaitsev, V.V. and Stepanov, A.V., On the origin of fast drift absorption bursts, Astron. Astrophys., 1975, vol. 45, pp. 135–140.Google Scholar