Abstract | Magnetic reconnection is a fundamental plasma process that permits the exchange of energy and mass between colliding plasmas, and it is either known or believed to occur in a wide variety of environments: plasma laboratories, planetary magnetospheres, stellar coronae, pulsars or accretion disks, for instance. It also corresponds to one of the main coupling mechanisms between the Solar Wind and the Earth's magnetosphere and it is responsible for energy conversion from electric and magnetic fields into kinetic energy of the particles. The Cluster (ESA, launched in 2000) and MMS (NASA, launched in 2015) spacecraft missions provide in-situ observations of the reconnecting magnetopause and allow us to study magnetic reconnection down to ion and electron scales. Several studies have reported the presence of cold (eV) plasma of ionospheric origin at the magnetospheric side of the magnetopause boundary layer that escapes via ionospheric outflows or plasmasphere erosion, which mass-loads the magnetosphere and reduces its reconnection rate with the solar wind. In addition, the ion particle distribution functions involved in reconnection exhibit a cold plasma beam in addition to the 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, which affect and modify the particle energization mechanisms at kinetic scales involved in magnetic reconnection. I will focus on our recent findings and ongoing studies on the microphysical effects and the consequences of ionospheric plasma for magnetic reconnection between the solar wind and the Earth's magnetosphere. |
