3D GUMICS Simulations of Northward IMF Magnetotail Structure

L. J. Fryer, R. C. Fear, I. L. Gingell, J. C. Coxon, Minna Palmroth, Sanni Hoilijoki, Pekka Janhunen, A. Kullen, P. A. Cassak

Research output: Contribution to journalArticleScientificpeer-review


This study presents a re-evaluation of the Kullen and Janhunen (2004, ) global northward interplanetary magnetic field (IMF) simulation, using the Grand Unified Magnetosphere-Ionosphere Coupling Simulation version 4 (GUMICS-4), a global MHD model. We investigate the dynamic coupling between northward IMF conditions and the Earth's magnetotail and compare the results to observation-based mechanisms for the formation of transpolar arcs. The results of this study reveal that under northward IMF conditions (and northward IMF initialization), a large closed field line region forms in the magnetotail, with similarities to transpolar arc structures observed from spacecraft data. This interpretation is supported by the simultaneous increase of closed flux measured in the magnetotail. However, the reconnection configuration differs in several respects from previously theorized magnetotail structures that have been inferred from both observations and simulations results and associated with transpolar arcs. We observe that dawn-dusk lobe regions form as a result of high-latitude reconnection during the initialization stages, which later come into contact as the change in the IMF B-y component causes the magnetotail to twist. We conclude that in the GUMICS simulation, transpolar arc-like structures are formed as a result of reconnection in the magnetotail, rather than high-latitude reconnection or due to the mapping of the plasma sheet through a twisted magnetotail as interpreted from previous analysis of GUMICS simulations.
Original languageEnglish
Article numbere2023JA031317
JournalJournal of Geophysical Research
Issue number8
Number of pages24
Publication statusPublished - Aug 2023
MoE publication typeA1 Journal article-refereed

Fields of Science

  • 115 Astronomy, Space science
  • MHD simulation
  • Magnetotail reconnection
  • northward IMF
  • Transpolar arc

Cite this