Astrophysics and Cosmology Seminar — Remote Zoom seminar
Dissipative processes in relativistic astrophysical plasma
Mr. Ivan Demidov
BGU
Abstract
I will outline two problems from my PhD thesis:
1) Soft gamma repeaters, believed to be magnetars (neutron stars with ultra-strong magnetic fields), produce powerful bursts whose luminosity exceeds the Eddington limit. The energy is released in the magnetosphere, forming a magnetically trapped electron-positron fireball that irradiates the neutron star’s surface. We propose a mechanism by which this radiation drives a baryonic outflow from the surface. The outflow forms a dense baryonic sheath around the fireball and, if the polar cap is illuminated, launches a baryonic wind, the properties of which we have studied.
2) Understanding magnetic field generation in collisionless unmagnetized shocks is essential for explaining the observed emission from gamma-ray burst afterglows. We consider such shocks in electron-positron plasma and propose a mechanism in which magnetic fields emerge naturally through the nonlinear evolution of Weibel current filaments. This evolution leads to the formation of magnetized plasma cavities in the upstream region of the shock.
1) Soft gamma repeaters, believed to be magnetars (neutron stars with ultra-strong magnetic fields), produce powerful bursts whose luminosity exceeds the Eddington limit. The energy is released in the magnetosphere, forming a magnetically trapped electron-positron fireball that irradiates the neutron star’s surface. We propose a mechanism by which this radiation drives a baryonic outflow from the surface. The outflow forms a dense baryonic sheath around the fireball and, if the polar cap is illuminated, launches a baryonic wind, the properties of which we have studied.
2) Understanding magnetic field generation in collisionless unmagnetized shocks is essential for explaining the observed emission from gamma-ray burst afterglows. We consider such shocks in electron-positron plasma and propose a mechanism in which magnetic fields emerge naturally through the nonlinear evolution of Weibel current filaments. This evolution leads to the formation of magnetized plasma cavities in the upstream region of the shock.