Work

Dipolarization Regions in Mercury's Magnetosphere: Observation of Flux Pileup and Formation of a Substorm Current Wedge

Year: 2025

Type: article

Abstract: At the end of its mission, the MESSENGER spacecraft's orbit intersected Mercury's nightside magnetic equator at low altitudes below 420 km, enabling the first in situ observations of this region, where the magnetic field strength is typically sub‐dipolar. We present 5 events from these orbits where MESSENGER encountered Earth‐like dipolarization regions characterized by enhanced field strengths up to 20 nT above the intrinsic planetary field, and an average decrease and increase in plasma proton density and temperature, respectively, for 1–2 min periods, comparable to Hermean substorm timescales. The events span local times of 1.5 hr pre‐ and post‐midnight, and are present from the magnetic equator up to magnetic latitudes of at least north. Supported by estimates of decreased flux tube entropy during these events, we suggest these dipolarization regions are formed by the pileup of dipolarization fronts and formation of a substorm current wedge.

Source: Geophysical Research Letters

DOI: 10.1029/2025gl117281

Authors: A. T. Cushen, W. Sun, J. Slavin, R. Dewey, X. Jia, J. Zhao

Institutions: University of Michigan, Space Sciences Laboratory, University of California, Berkeley

Language: English

Topic: Ionosphere and magnetosphere dynamics

Subfield: Astronomy and Astrophysics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,190

Funders: National Science Foundation, National Aeronautics and Space Administration, Nuclear Safety and Security Commission