Date:
Tue, 24/12/202412:30-13:30
Speaker: Dr. Allard Jan van Marle (Extreme Light Infrastructure ERIC, ELI Beamlines Facility, Dolní Břežany, Czech Republic)
Title: Using PIC-MHD to model particle acceleration in astrophysical shocks
Abstract:
When modelling the behaviour of astrophysical plasmas, we run into a fundamental computational problem. One can treat the plasma as a fluid using traditional grid-based magnetohydrodynamics (MHD) or, alternatively, describe the plasma as a collection of individual particles using particle-in-cell (PIC). However, both methods have limitations. MHD is computationally efficient but achieves this efficiency by describing the plasma in terms of averages. Therefore, it cannot model any interaction that requires microphysics. Nor can it handle a plasma that is not in local thermal equilibrium. By contrast, PIC does include microphysics and can handle any plasma, irrespective of whether it is in equilibrium. However, it buys this ability at a high computational cost and, as a result, requires considerable support to model even small structures.
Several methods have been introduced to solve this issue. Here I will demonstrate the concept of PIC-MHD, which treats the plasma as a superposition of a thermal plasma, described through MHD; and a small, non-thermal component, treated through PIC. Using this method, we have explored 2-D and 3-D models of parallel shocks and the influence of shock obliquity on the acceleration process. Currently, we are in the process of extending the method to cover relativistic shocks to cover a wider range of astrophysical phenomena.
Zoom link:
https://huji.zoom.us/j/83482274870?pwd=VjEz4G7wbN7sU1a7TO0s9ReuPbPBLu.1
Meeting ID: 834 8227 4870
Passcode: 005622
Contact: Nir Shaviv
Title: Using PIC-MHD to model particle acceleration in astrophysical shocks
Abstract:
When modelling the behaviour of astrophysical plasmas, we run into a fundamental computational problem. One can treat the plasma as a fluid using traditional grid-based magnetohydrodynamics (MHD) or, alternatively, describe the plasma as a collection of individual particles using particle-in-cell (PIC). However, both methods have limitations. MHD is computationally efficient but achieves this efficiency by describing the plasma in terms of averages. Therefore, it cannot model any interaction that requires microphysics. Nor can it handle a plasma that is not in local thermal equilibrium. By contrast, PIC does include microphysics and can handle any plasma, irrespective of whether it is in equilibrium. However, it buys this ability at a high computational cost and, as a result, requires considerable support to model even small structures.
Several methods have been introduced to solve this issue. Here I will demonstrate the concept of PIC-MHD, which treats the plasma as a superposition of a thermal plasma, described through MHD; and a small, non-thermal component, treated through PIC. Using this method, we have explored 2-D and 3-D models of parallel shocks and the influence of shock obliquity on the acceleration process. Currently, we are in the process of extending the method to cover relativistic shocks to cover a wider range of astrophysical phenomena.
Zoom link:
https://huji.zoom.us/j/83482274870?pwd=VjEz4G7wbN7sU1a7TO0s9ReuPbPBLu.1
Meeting ID: 834 8227 4870
Passcode: 005622
Contact: Nir Shaviv