Direct Measurement of Electron Cyclotron Emission during High Guide Field Magnetic Reconnection

Significant amount of collisional scatterings of non-thermal electrons accelerated by magnetic reconnection electric field was identified outside the diffusion region in a high-guide-field reconnection experiment using spherical tokamak plasma merging. Electron cyclotron emission (ECE) measurement and orbit calculations of the electrons clarified that enhanced ECE observed during the high-guide-field reconnection event stemmed from gyro-motions of non-thermal electrons having high perpendicular energy generated through the parallel acceleration and scattering by the background ions. The efficient conversion condition of parallel kinetic energy of accelerated electrons to the perpendicular one was attributed to the long connection length of the magnetic field lines inherent to the toroidal experimental configuration of high-guide-field reconnection and moderate collisional condition.