Energy Partition and Balance at Dipolarization Fronts. Issue 20 (25th October 2022)

• Record Type: Journal Article
• Authors: Liu, C. M.; Cao, J. B.; Pollock, C. J.
• Is Part Of: Geophysical research letters. Volume 49:Issue 20(2022)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2022-10-25
• Subjects: energy partition -- energy balance -- MMS mission -- dipolarization fronts -- particle acceleration -- particle heating; Geophysics -- Periodicals; Planets -- Periodicals; Lunar geology -- Periodicals; 550
• DOI: 10.1029/2022GL100239
• Languages: English
• ISSNs: 0094-8276

Abstract

Abstract: Dipolarization fronts (DFs) have been documented as important structures contributing to energy conversion and flux transport in Earth's magnetotail. However, energy partition and balance at DFs still remain elusive. Using high‐cadence data from NASA's Magnetospheric Multiscale mission, we preform a comprehensive investigation of energy budgets at the DFs. We find that material derivatives of particle energy densities in the DF frame are basically close to zero, indicating that particles experience negligible heating and/or acceleration and that the energy released at the DFs is predominantly manifested in the form of energy flux. The energy flux is found to be dominated by ion and electron enthalpy flux, ion heat flux, and Poynting flux, with electron enthalpy flux being locally elevated. In addition, the energy flux tends to increase during the DFs' earthward propagation, without exhibiting clear asymmetry in the dawn‐dusk direction. These results help further understand energy budgets at the DFs. Plain Language Summary: Dipolarization fronts (DFs), earthward‐propagating magnetic structures characterized by sharp enhancement of northward component ( B z ) of the geomagnetic field, have been suggested as favorable regions for particle acceleration/heating, wave generation, and energy transport, etc. In particular, DFs host significant local energy conversion processes which might be responsible for the global energy transport in the Earth's magnetotail. Therefore they have attracted considerable interest in the recent two decades. In the present study, we aim to investigate one key issue regarding energy conversion at the DFs, that is, energy partition and balance, by taking advantage of unprecedentedly high‐cadence data from the NASA's Magnetospheric Multiscale mission. New results obtained from the present investigation can help better understand energy budgets at the fronts and its role in global energy transport. Key Points: Energy released at dipolarization fronts (DFs) is predominately manifested in the form of energy flux, without significant particle heating and/or acceleration Energy flux is dominated by particle enthalpy flux, ion heat flux and Poynting flux, with electron enthalpy flux locally elevated Energy flux tends to increase during DFs' earthward propagation, without clear asymmetry in the dawn‐dusk direction