How unstable is the solar wind?

The solar wind is a plasma flow that emanates from the solar corona and fills the interplanetary space. Collisions between plasma particles are very rare. Therefore, the plasma can deviate from thermodynamic equilibrium. If these deviations are large enough, the plasma drives kinetic instabilities, which create small-scale fluctuations and bring the plasma closer to equilibrium by scattering particles in velocity space. I will show signatures of these instabilities in spacecraft observations of both the particles and the electromagnetic fields in the solar wind. An automated method based on Nyquist’s instability criterion applied to a large dataset of spacecraft measurements actually suggests that the majority of the solar wind is unstable. These instabilities play an important role for the energetics and may be responsible for part of the observed local heating of the solar wind. At the end, I will introduce our novel ALPS code to determine the stability of the solar wind based on future direct measurements of particle distribution functions with modern spacecraft like Solar Orbiter and Parker Solar Probe

26 Jul 2018
Dr. Daniel Verscharen, Mullard Space Science Laboratory, University College London