Cold plasma and magnetic reconnection at the magnetopause boundary layer

International audience; Magnetic reconnection is a fundamental plasma process that permits the exchange of energy and mass between colliding plasmas, e.g., between the Solar Wind and the Earth's magnetosphere. Several studies have reported the presence of cold plasma of ionospheric origin at the magnetospheric side of the magnetopause. As a result, the particle distribution functions involved in reconnection are far from equilibrium, exhibiting a cold plasma beam in addition to the typical hot plasmas from the magnetosheath and the magnetosphere. Cold ions possess a much smaller gyroradius and therefore introduce a new length-scale into the system. This situation leads to structures of the size of the cold ion gyroradius and allows for the existence of new instabilities. In addition, the energization of cold plasma by reconnection is governed by different processes than for the hot plasma.