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[9/18] Particle Acceleration at Weak shocks in High-beta Intracluster Medium
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2020.09.15
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Title: Particle Acceleration at Weak shocks in High-beta Intracluster Medium

Date & Time: Friday, September 18th, 2020, 11:00 AM

Location: Online

( https://zoom.us/j/6210767044?pwd=SkRuRzZtbjcwQkszS2g4QThiWVl3dz09 , It will open at 10:30 AM)

Language: English

Speaker: Prof. Hyesung Kang (Pusan National University)


Abstract

Weak shocks with low sonic Mach numbers are induced by mergers and/or supersonic flow motions in the hot tenuous intracluster medium (ICM). High energy cosmic ray (CR) protons are expected to be accelerated at quasi-parallel shocks via diffusive shock acceleration (DSA), while CR electrons are expected to be accelerated preferentially at quasi-perpendicular shocks. The key element in determining the DSA efficiency is the so-called injection process, which energizes thermal particles to suprathermal energies sufficient to diffuse across the shock transition layer.  Reflection of incoming particles and ensuing self-excitation of MHD/plasma waves play important roles in particle injection to DSA. Using particle-in-cell (PIC) simulations, we study the injection and early acceleration of protons and electrons at weak shocks in high beta plasma. We find that the proton (electron) injection at quasi-parallel (quasi-perpendicular) shocks is effective only for supercritical shocks  with the sonic Mach number greater than about 2.3. Further investigation is necessary to examine if subcritical shocks can re-accelerate pre-existing populations of protons and electrons in the ICM.

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