Abstract


  STUDY OF RADIAL DISTRIBUTION OF THE ELECTRON VELOCITY DISTRIBUTION FUNCTION FROM SUN TO EARTH

  G. Nampoothiri, Space Physics Laboratory, VSSC, ISRO, govindgn9@gmail.com

R. Satheesh Thampi, Space Physics Laboratory, VSSC, ISRO, satheesh_thampi@vssc.gov.in
Anil Bhardwaj, Space Physics Laboratory, VSSC, ISRO , anil_bhardwaj@vssc.gov.in





Sun is continuously giving out its energy in the form of both electromagnetic radiation and particles (solar wind). Solar wind is a magnetized plasma emanating from the Sun in all directions with an average bulk velocity of ~ 400 km/s at 1 AU. It consist mainly of protons, alpha particles and electrons. Earlier studies shows that the electrons present in the solar wind are characterized by three different populations based on their thermal energy and its direction of propagation with respect to the Interplanetary Magnetic Field (IMF) and they are: the thermal core, the suprathermal halo and the field aligned strahl. The observed Electron Velocity Distribution Function (EVDF) in the solar wind have shown a Maxwellian core and a non-Maxwellian extended tail. Several studies were reported to understand the Non-Maxwellian component of the EVDF including the models using kinetic approach in which the Lorentzian distribution function was fitted to a certain extent. An attempt is made to get the radial distribution of the EVDF at different solar altitudes using kinetic approach, in which the Coulomb collisions between the solar wind particles are considered for getting a better fit to the non-Maxwellian component . Data from various missions such WIND, SOHO and ACE are used for getting the EVDF moments such as the electron number density, particle flux, bulk velocity, dynamic pressure, temperature and the energy flux. Scientific outcomes of this study are presented in-detail and discussed in this paper.