Statistical Analysis of Mercury's Magnetotail Lobe Field Strength using MESSENGER Observations
Abstract
Here, we present an analysis of the properties of Mercury's magnetotail lobes, as observed by the Mercury Surface, Space Environment, Geochemistry and Ranging (MESSENGER) orbital mission. The magnetotail lobes are characterized by low plasma β (the ratio between thermal and magnetic pressure) and low fluctuating magnetic field strength.The extent and properties of the lobes respond to changes in flux content and magnetopause flaring, making them a crucial region for analyzing the magnetospheric response to the intense solar wind conditions at Mercury's orbit. We utilize data from the Fast Imaging Plasma Spectrometer (FIPS) and magnetometer (MAG) instruments onboard MESSENGER to define a set of empirically determined criteria which automatically determine time intervals when the spacecraft traversed the magnetotail lobes. From 3332 MESSENGER orbits, we identify 975 lobe magnetic field intervals. We derive a new expression for the average falloff of Mercury's lobe field strength based on the complete MESSENGER sampling: Blobe(r)=(131 ± 10)*r(-2.3 ± 0.3)+(32 ± 6). This relationship allows us to assess the extent to which each lobe crossing event is enhanced or diminished compared to its nominal state. Our findings reveal a direct correlation between the relative strength of the magnetotail lobe and the upstream solar wind dynamic pressure, estimated at the closest dayside magnetopause crossing along MESSENGER's orbit. Thus, our study provides evidence for lobe magnetic flux enhancement as a response to upstream dynamic pressure conditions. The upcoming BepiColombo mission, featuring two spacecraft, will provide simultaneous measurements of Mercury's dayside and magnetotail environment. This capability will offer an optimal opportunity to further explore the relationship between the solar wind and the lobe magnetic field.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2023
- Bibcode:
- 2023AGUFM.P31C3107B