On the radial and longitudinal variation of a magnetic cloud: ACE, wind, ARTEMIS and Juno observations
File(s)Davies2020_Article_OnTheRadialAndLongitudinalVari.pdf (1.49 MB)
Published version
Author(s)
Davies, Emma
Forsyth, Robert
Good, Simon
Kilpua, Emilia
Type
Journal Article
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∘ 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.
Date Issued
2020-11-10
Date Acceptance
2020-09-23
Citation
Solar Physics: a journal for solar and solar-stellar research and the study of solar terrestrial physics, 2020, 295
ISSN
0038-0938
Publisher
Springer
Journal / Book Title
Solar Physics: a journal for solar and solar-stellar research and the study of solar terrestrial physics
Volume
295
Copyright Statement
© The Author(s) 2020. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
License URL
Sponsor
Science and Technology Facilities Council (STFC DTP 2017-2021)
Grant Number
ST/N504816/1
Subjects
Astronomy & Astrophysics
0201 Astronomical and Space Sciences
Publication Status
Published
Article Number
ARTN 157