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| INSTITUTET FÖR RYMDFYSIK | UPPSALA |
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| Swedish Institute of Space Physics | (59°50.272′N, 17°38.786′E) |
Master thesis (30c)/Examensarbete (30hp)
Statistical study of shock reformation
Student: Hannah Wik, Royal Institute of Technology (KTH), StockholmMain supervisor: Andrew Dimmock
Assistant supervisors: Yuri Khotyaintsev, Ahmad Lalti, Tomas Karlsson (KTH)
Period: Spring 2023
Abstract
Collisionless shocks are widespread phenomena in the universe, and understanding the mechanisms behind their energy dissipation, with a rare number of collisions between particles, remains a significant unresolved question. The Earth's bow shock provides an excellent opportunity to study this phenomena in situ. For high Mach number shocks, the shock cannot be sustained without partial reflection of the incoming ions. At higher Mach numbers, the shock surface starts to exhibit non-stationary behaviours, meaning that the shock surface starts evolving. One such behaviour is known as shock reformation, where a new shock forms upstream of an existing one. This study aims to investigate shock reformation using data obtained from NASA's MMS mission, which offers precise measurements with high spatial and temporal resolutions through its constellation of four spacecraft. Using the MMS shocks database (Lalti et al., 2022), the gradient of the magnetic field magnitude is computed to infer non-stationary behaviour and identify potential instances of shock reformation and other shock behaviours. Through the analysis of the MMS measurements, some insight into the non-stationary characteristics of shocks is obtained using the gradient of the magnetic field. However, further analysis is needed in order to refine the method of identifying non-stationary behaviour of shocks, for future applications.Results
![[MMS]](shock_mms.png)
MMS data showing one of the shocks studied in the project.