2020/09/21 by E. E. Davies, Emma E. Davies, R. J. Forsyth +5 · 26 citations
Physics and Astronomy · #Astro and Planetary Science #Earth's magnetic field #Flux (metallurgy) #Magnetic cloud #Magnetic field #Magnetic flux #Planetary Science and Exploration #Protein filament #Rope #Solar and Space Plasma Dynamics #Spacecraft #Variation (astronomy) #physics.space-ph
paper · pdf · doi:10.1007/s11207-020-01714-z
published in Solar Physics 295(11) (Springer Science+Business Media)
arxiv created 2020/09/21 · openalex created_date 2020/09/25 · openalex publication_date 2020/11/01 · arxiv updated 2020/11/18 · openalex updated_date 2026/08/05
Abstract We present observations of the same magnetic cloud made near Earth by the Advance Composition Explorer (ACE), Wind, and the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon’s Interaction with the Sun (ARTEMIS) mission comprising the Time History of Events and Macroscale Interactions during Substorms (THEMIS) B and THEMIS C spacecraft, and later by Juno at a distance of 1.2 AU. The spacecraft were close to radial alignment throughout the event, with a longitudinal separation of 3.6∘ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msup> <mml:mn>3.6</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> between Juno and the spacecraft near Earth. The magnetic cloud likely originated from a filament eruption on 22 October 2011 at 00:05 UT, and caused a strong geomagnetic storm at Earth commencing on 24 October. Observations of the magnetic cloud at each spacecraft have been analysed using minimum variance analysis and two flux rope fitting models, Lundquist and Gold–Hoyle, to give the orientation of the flux rope axis. We explore the effect different trailing edge boundaries have on the results of each analysis method, and find a clear difference between the orientations of the flux rope axis at the near-Earth spacecraft and Juno, independent of the analysis method. The axial magnetic field strength and the radial width of the flux rope are calculated using both observations and fitting parameters and their relationship with heliocentric distance is investigated. Differences in results between the near-Earth spacecraft and Juno are attributed not only to the radial separation, but to the small longitudinal separation which resulted in a surprisingly large difference in the in situ observations between the spacecraft. This case study demonstrates the utility of Juno cruise data as a new opportunity to study magnetic clouds beyond 1 AU, and the need for caution in future radial alignment studies.