Cluster observations of plasma in the high latitude magnetotail associated with cusp‐aligned arcs
Author(s)
Type
Journal Article
Abstract
During periods of northward interplanetary magnetic field (IMF), the magnetospheric structure
and dynamics are dramatically different compared to the southward IMF case. Previous studies using both
observations and simulations have shown that under northward IMF the magnetotail becomes dominated by
closed magnetic flux and associated trapped particle populations. In this study, we analyze three intervals of
plasma observed in the high latitude magnetotail during a period of prolonged northward IMF, coinciding with
observations of cusp‐aligned arcs in the polar region. We observe that the plasma is typically observed by all 4
Cluster spacecraft near simultaneously and has some substructure observed on length scales of 0.5–1.5 RE. The
plasma characteristics in each of the three intervals studied are similar. The ion and electron densities are on the
order of 10− 1–100 cm− 3. The electron energies typically vary between 102 and 103 eV. The ion energies are
higher compared to the electron energies and range between 102 and 104 eV. The ion temperatures are on the
order of 5–18 MK. The speed of the plasma crossing the Cluster spacecraft is between 1 and 10 kms− 1
. In one
interval Cluster observes distinctly different but adjacent plasma populations. We suggest these plasma
populations are on interleaving flux tubes and may present supporting evidence for dual lobe reconnection
acting to trap plasma within the magnetosphere and resulting cusp‐aligned arc formation
and dynamics are dramatically different compared to the southward IMF case. Previous studies using both
observations and simulations have shown that under northward IMF the magnetotail becomes dominated by
closed magnetic flux and associated trapped particle populations. In this study, we analyze three intervals of
plasma observed in the high latitude magnetotail during a period of prolonged northward IMF, coinciding with
observations of cusp‐aligned arcs in the polar region. We observe that the plasma is typically observed by all 4
Cluster spacecraft near simultaneously and has some substructure observed on length scales of 0.5–1.5 RE. The
plasma characteristics in each of the three intervals studied are similar. The ion and electron densities are on the
order of 10− 1–100 cm− 3. The electron energies typically vary between 102 and 103 eV. The ion energies are
higher compared to the electron energies and range between 102 and 104 eV. The ion temperatures are on the
order of 5–18 MK. The speed of the plasma crossing the Cluster spacecraft is between 1 and 10 kms− 1
. In one
interval Cluster observes distinctly different but adjacent plasma populations. We suggest these plasma
populations are on interleaving flux tubes and may present supporting evidence for dual lobe reconnection
acting to trap plasma within the magnetosphere and resulting cusp‐aligned arc formation
Date Issued
2025-04-01
Date Acceptance
2025-03-18
Citation
Journal of Geophysical Research: Space Physics, 2025, 130 (4)
ISSN
2169-9380
Publisher
American Geophysical Union (AGU)
Journal / Book Title
Journal of Geophysical Research: Space Physics
Volume
130
Issue
4
Copyright Statement
©2025. The Author(s). This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.
License URL
Identifier
10.1029/2024JA033252
Publication Status
Published
Article Number
e2024JA033252
Date Publish Online
2025-04-03