Implications of Space Plasma Instabilities for Intergalactic Magnetic Field and Light Dark Matter

by Dr Oindrila Ghosh (Stockholm University)

Wednesday 4 Oct 2023, 13:30 → 14:30 Europe/Stockholm

Albano 3: 6228 - Mega (22 seats) (Albano Building 3)

https://stockholmuniversity.zoom.us/j/530682073

 

TeV blazars dominate the extragalactic gamma-ray sky and highly energetic pair beams arising from such blazar jets underproduce gamma rays in the GeV band while inverse-Compton scattering off the cosmic microwave background. Isotropic gamma ray background measurements strongly suggest that when the intergalactic magnetic field is feeble, space plasma instabilities can play a crucial role in alleviating this GeV-TeV tension by draining the pair beam energy into the background plasma of the intergalactic medium (IGM). Importantly, as can be realised in laboratory astrophysics experiments, energy losses through instabilities and widening of pair beams via momentum diffusion follow a closed-form Fokker-Planck evolution. This has profound implications not only for TeV astrophysics, but also the strength of the intergalactic magnetic field. A direct consequence of the instability losses and IGM heating is the modification of thermal history at late times, which suppresses structure formation particularly in underdense regions and translates to a favoured mass range for light dark matter candidates such as axion-like particles.

Gosh_2023-10-04.mp4