Impact of Magnetic Focusing Effects on the Electron Beam Formation in the Solar Corona

Flare produced electron beams are widely believed to responsible for type III radio bursts. The height of the starting frequency of type III radio bursts is found commonly higher than the site of particle acceleration region of solar flares. The magnetic focusing effect, converting electron kinetic energy from perpendicular to parallel, alone is capable of accelerating the non-thermal electrons in the lower corona to reach and exceed the threshold of nonlinear electron two stream instability within an altitude of 0.5 solar radii as the electrons propagating away from the initial acceleration site along the magnetic field line. During the transport, the power-law energy spectral index of the non-thermal electrons maintains the original one produced in the acceleration region. For the first time, the effect of transferring electron kinetic energy from perpendicular to parallel caused by magnetic focusing has a maximum ratio is discussed. The efficiency of the acceleration of magnetic focusing effect subjected to relative drifting velocity, the magnetic field spectral index, and electron beam spectral index are shown.