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Electrostatic Solitary Waves in Non-Maxwellian Space Plasmas: On the Role of Suprathermal Particles

February 11, 2021 @ 12:00 pm - 1:00 pm

Space plasmas are generally characterized by the presence of highly energetic particles, which are accelerated via various mechanisms. These suprathermal particles populate the upper zone in the velocity space, leading to a long-tailed (non-thermal) distribution and a power law dependence for high velocities, that is effectively modeled by a kappa-type (non-Maxwell-Boltzmann) distribution. Electrostatic solitary waves (ESWs), i.e. localized density and electric field propagating at supersonic speeds are ubiquitous e.g. in the Earth’s magnetosphere and in the ionosphere; these are essentially stationary-profile pulse-shaped electrostatic potential disturbances associated with particle density enhancement (or depletion) regions observed in abundance by satellite and spacecraft missions.

The talk will review the basic principles of the modeling of ESWs in Space plasmas in the presence of suprathermal particles in the background. The effect of superthermality on the dispersion characteristics of linear waves will be discussed, mainly focusing on the role of suprathermals on the phase speed. The main aspects of the nonlinear modeling of ESWs based on plasma-fluid theory will be revisited from first principles, taking into account a kappa-distributed background. Focusing on nonlinear modes, the role of the spectral index (kappa) on dynamical localized wave features (amplitude, existence region and propagation characteristics) will be elucidated. Applications of this modeling in relation with space observations will be discussed, in particular focusing on satellite observations and on data provided by the Cassini (Saturn) and the MAVEN (Mars) mission.

This talk is aimed at an audience with moderate prior knowledge of modeling in geophysics and in Space science. It consists of an overview of earlier research work carried out in collaboration with Michael McKerr (UAE & Belfast, UK), Ibrahem Elkamash (Egypt), Manfred A. Hellberg (Durban, South Africa), Frank Verheest (Gent, Belgium), Nareshpal Singh Saini (GNDU, India) and S. Maharaj (SANSA, Hermanus, S. Africa) among others.