Cluster and MMS Simultaneous Observations of Magnetosheath High Speed Jets and Their Impact on the Magnetopause

Frontiers in Astronomy and Space Sciences

H. Fu¹  I. Dandouras²  Jonathan P. Eastwood²  Owen Roberts³  Y. V. Bogdanova³  H. Laakso⁴  Jim L. Burch⁴  R. C. Fear⁵  Arnaud Masson⁶  M. G. G. T. Taylor⁶  M. Dunlop⁷  K. J. Genestreti⁷  C. Carr⁸  Daniel B. Graham⁹  C. T. Russell^1,10  G. Paschmann^1,11  G. Lapenta^1,11  Yu V. Khotyaintsev^1,11  R. B. Torbert^1,12  Benoit Lavraud^1,13  C. Pollock^1,14  A. Varsani^1,14  J. Berchem^1,15  R. Nakamura^1,15  A. P. Dimmock^1,16  S. Toledo-Redondo^1,18  L. Turc^1,19  C. Philippe Escoubet^2,20  P. Kajdič^2,20  A. Fazakerley^2,21  C. Norgren^2,21  S. E. Haaland^2,22  K.-J. Hwang^2,23  B. L. Giles^2,23  N. Aunai^2,24  D. G. Sibeck^2,25  J. Dargent^2,26 

[1] Astronomy, University of Southampton, Southampton, United Kingdom;0Blackett Laboratory, Imperial College London, London, United Kingdom;0Rutherford Appleton Laboratory Space, Science and Technology Facilities Council, UK Research and Innovation, Didcot, United Kingdom;1IWF, Space Research Institute (OAW), Graz, Austria;;1School of Physics &2European Space Astronomy Centre, Madrid, Spain;2Space Science Institute, School of Astronautics, Beihang University, Beijing, China;3Instituto de Geofísica, Universidad Nacional Autónoma de México, Cuernavaca, Mexico;3Space Science Center, University of New Hampshire, Durham, NC, United States;4Denali Scientific, Healy, AK, United States;4Institute for Space Physics (Uppsala), Uppsala, Sweden;5Department of Earth, Planetary and Space Science, University of California, Los Angeles, Los Angeles, CA, United States;5Department of Mathematics, Center for Mathematical Plasma Astrophysics, KU Leuven, Leuven, Belgium;6Goddard Space Flight Center, National Aeronautics and Space Administration, Greenbelt, MD, United States;7Mullard Space Science Laboratory, Faculty of Mathematical and Physical Sciences, University College London, Dorking, United Kingdom;8Department of Physics and Astronomy, University of California, Los Angeles, Los Angeles, CA, United States;9Max Planck Institute for Extraterrestrial Physics, Garching, Germany;Department of Electromagnetism and Electronics, University of Murcia, Murcia, Spain;Department of Physics, Helsinki University of Technology, Helsinki, Finland;ESA, European Space Research and Technology Centre, Noordwijk, Netherlands;IRAP, CNRS, UPS, CNES, Université de Toulouse, Toulouse, France;Max Planck Institute for Solar System Research, Göttingen, Germany;Southwest Research Institute, San Antonio, TX, United States;UMR7648 Laboratoire de physique des plasmas (LPP), Palaiseau, France;University of Bergen, Bergen, Norway;University of Pisa and National Interuniversity Consortium for the Physical Sciences of Matter (CNISM), Pisa, Italy;

关键词: magnetosheath;    magnetopause;    high-speed jet;    multi-scale;    turbulence;   

DOI  :  10.3389/fspas.2019.00078

来源: DOAJ

【 摘 要 】

When the supersonic solar wind encounters the Earth's magnetosphere a shock, called bow shock, is formed and the plasma is decelerated and thermalized in the magnetosheath downstream from the shock. Sometimes, however, due to discontinuities in the solar wind, bow shock ripples or ionized dust clouds carried by the solar wind, high speed jets (HSJs) are observed in the magnetosheath. These HSJs have typically a Vx component larger than 200 km s−1 and their dynamic pressure can be a few times the solar wind dynamic pressure. They are typically observed downstream from the quasi-parallel bow shock and have a typical size around one Earth radius (RE) in XGSE. We use a conjunction of Cluster and MMS, crossing simultaneously the magnetopause, to study the characteristics of these HSJs and their impact on the magnetopause. Over 1 h 15 min interval in the magnetosheath, Cluster observed 21 HSJs. During the same period, MMS observed 12 HSJs and entered the magnetosphere several times. A jet was observed simultaneously by both MMS and Cluster and it is very likely that they were two distinct HSJs. This shows that HSJs are not localized into small regions but could span a region larger than 10 RE, especially when the quasi-parallel shock is covering the entire dayside magnetosphere under radial IMF. During this period, two and six magnetopause crossings were observed, respectively, on Cluster and MMS with a significant angle between the observation and the expected normal deduced from models. The angles observed range between from 11° up to 114°. One inbound magnetopause crossing observed by Cluster (magnetopause moving out at 142 km s−1) was observed simultaneous to an outbound magnetopause crossing observed by MMS (magnetopause moving in at −83 km s−1), showing that the magnetopause can have multiple local indentation places, most likely independent from each other. Under the continuous impacts of HSJs, the magnetopause is deformed significantly and can even move in opposite directions at different places. It can therefore not be considered as a smooth surface anymore but more as surface full of local indents. Four dust impacts were observed on MMS, although not at the time when HSJs are observed, showing that dust clouds would have been present during the observations. No dust cloud in the form of Interplanetary Field Enhancements was however observed in the solar wind which may exclude large clouds of dust as a cause of HSJs. Radial IMF and Alfvén Mach number above 10 would fulfill the criteria for the creation of bow shock ripples and the subsequent crossing of HSJs in the magnetosheath.

【 授权许可】

Unknown