On the Radial and Longitudinal Variation of a Magnetic Cloud: ACE, Wind, ARTEMIS and Juno Observations

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 $3.6^{\circ}$ 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.

In situ multi-spacecraft and remote imaging observations of the first CME detected by Solar Orbiter and BepiColombo

“…The small longitudinal (within 5 • ) and latitudinal separation between Solar Orbiter, Wind, and BepiColombo during the passage of the CME provides an opportunity to study the radial evolution of the CME using in situ measurements of the magnetic field. However, caution must still applied when interpreting results as significant differences in CME magnetic flux rope properties have previously been observed over small longitudinal separations (Kilpua et al 2011;Winslow et al 2016;Davies et al 2020) and therefore differences in observations and properties may also be due to spatial variation of the CME. Similarly to the KFR and 3DCORE models, this analysis focuses on the section of the flux rope which is unperturbed (the UMFR) by the interaction with the following higher speed stream and the phys-Article number, page 5 of 11 A&A proofs: manuscript no.…”

“…separated by less than 5 • in longitude and separated by more than 0.2 AU in heliocentric distance are relatively rare but provide valuable insight into the properties, rotation, expansion, and interaction with other features of the solar wind environment as the ICME propagates (e.g. Good et al 2015Good et al , 2018Winslow et al 2016;Kilpua et al 2019;Lugaz et al 2019;Davies et al 2020).…”

Multi-point analysis of coronal mass ejection flux ropes using combined data from Solar Orbiter, BepiColombo, and Wind

“…More recently, a focus has been placed on the study of multi-point events, namely, ICMEs that are observed in situ by multiple spacecraft (Möstl et al 2009a;Kilpua et al 2009;Good et al 2019;Davies et al 2020;Salman et al 2020) in an attempt to gain a better global understanding of ICME structure and their evolution. Unfortunately, such events are inherently rare due to the limited number of spacecraft with the onboard magnetometers in different solar orbits within similar time frames.…”

Editorial: Towards Future Research on Space Weather Drivers

“…CME evolution and propagation in the heliosphere is still one of the critical areas of research. In this collection, there are several studies that span from a case event analysis, data analysis, 3D simulation, theoretical understanding of the physical processes associated with the evolution, and identification of the internal structure based on artificial intelligence techniques (Davies et al, 2020;Balmaceda et al, 2020;Desai et al, 2020;Florido-Llinas, Nieves-Chinchilla, and Linton, 2020;dos Santos et al, 2020). As stated by Balmaceda et al (2020) (Editor's choice), a proper characterization of the kinematics of CMEs is important not only for practical purposes, i.e.…”

“…Thus, their study focused on the observations obtained with COR2 onboard the Solar Terrestrial Relations Observatory (STEREO) from 2007 to 2014 to investigate the self-similarity assumption as a function of the heliocentric distance of the CME events. Davies et al (2020) reported the case of a multipoint-observed magnetic cloud by the Advanced Composition Explorer (ACE), Wind, the Acceleration, Reconnection, Turbulence and Electrodynamics of the Moon's Interaction with the Sun (ARTEMIS), and Juno satellites on 25 October 2011. This singular opportunity allowed the exploration of the radial and longitudinal variation of the internal properties of the magnetic cloud.…”