Drifting pulsating structures generated during tearing and coalescence processes in a flare current sheet

Astronomical Institute of the Academy of Sciences of the Czech Republic, 25165 Ondřejov, Czech Republic e-mail: [karlicky;barta]@asu.cas.cz

Received: 6 July 2006
Accepted: 4 December 2006

Abstract

Aims.Based on particle-in-cell simulations, drifting pulsating structures are interpreted as the radio emission generated during tearing and coalescence processes in the current sheet of a flare.

Methods.A 2.5D particle-in-cell electromagnetic relativistic code was used considering two versions of the model: a) the model with one current sheet with free boundary conditions and b) the model with two current sheets and periodic boundary conditions. The dispersion diagrams of electromagnetic waves we then constructed using the 2D Fourier transform.

Results.It is found that electrons are accelerated most efficiently in the region near the x-point of the magnetic field structure in the phase at the end of tearing process and at the beginning of plasmoid coalescence. The most energetic electrons are distributed mainly along the x-lines of the magnetic field structure. During these processes, Langmuir waves are generated, along with the electromagnetic (radio) ones. It looks as these electromagnetic waves can be observed mainly on the second harmonics of the plasma frequencies corresponding to the plasma densities in the external parts of the plasmoids.