Xue Wang successfully defended her PhD thesis on plasma transport and energization in Mercury’s low-latitude boundary layer.
28 Sep. 2026
- Abstract
- The low-latitude boundary layer (LLBL) is a key region for plasma exchange between the magnetosheath and the magnetosphere. While Earth’s LLBL has been studied extensively, earlier studies at Mercury focused mainly on the dayside. BepiColombo’s third Mercury flyby revealed ion energy dispersion in the dusk-side LLBL, but the layer’s global distribution and internal structure remained poorly understood.
- Using MESSENGER magnetic-field and ion measurements from 2011 to 2015, this thesis identifies 202 LLBL events spanning nearly the full range of magnetic local time. The survey reveals a dawn–dusk asymmetry and a general increase in LLBL thickness from noon toward the flanks. Analysis of proton energy distributions distinguishes three types: single-population events concentrated near noon, double-population events found near noon and toward dusk, and energy-shifted events on the dawn side. Their distinct local-time distributions, dependence on the interplanetary magnetic field, and proton properties show that Mercury’s LLBL is not uniform. This organization points to different processes across the boundary layer: reconnection near noon, Kelvin–Helmholtz mixing toward dusk, and proton drift and energization on the dawn side. Mercury’s small size and the strong curvature of its magnetic field may enhance dawnside energization. These processes offer a physical explanation for the observed dawn–dusk asymmetry. BepiColombo’s orbital observations will provide broader ion energy coverage, along with measurements of low-energy electrons, electric fields, and plasma waves. These measurements will help clarify how plasma is transported and energized within the LLBL and test the proposed roles of reconnection, Kelvin–Helmholtz mixing, and drift-driven energization.
- Date & Location
- Friday, 25th of September 2026 at 2:00pm
- Astier amphitheater, Esclangon builing, Pierre & Marie Campus, Sorbonne Université, Paris
- Composition of the PhD Committee
- President: Dr. Karine ISSAUTIER Research Director, CNRS, LIRA
- Reviewer: Dr. Tomas KARLSSON Professor, KTH
- Reviewer: Dr. Iannis DANDOURAS Emeritus Research Director, CNRS, IRAP
- Examiner: Dr. Aurélie MARCHAUDON Research Director, CNRS, IRAP
- Examiner: Dr. Nicolas ANDRÉ Professor, ISAE-SUPAERO
- Supervisor: Dr. Fouad SAHRAOUI Research Director, CNRS, LPP
- Co-advisor: Dr. Lina HADID Research Scientist, CNRS, LPP
- Co-advisor: Dr. Sae AIZAWA Research Scientist, CNRS, LPP