Asymmetric magnetosphere deformation driven by hot flow anomaly(ies)

• Published in: Geophysical research letters Vol. 39; no. 15
• Main Authors: Šafránková, J., Goncharov, O., Němeček, Z., Přech, L., Sibeck, D. G.
• Format: Journal Article
• Language: English
• Published: Washington, DC Blackwell Publishing Ltd 16.08.2012; American Geophysical Union; John Wiley & Sons, Inc
• Subjects: Astrophysics; Atmospheric sciences; Deformation; Earth sciences; Earth, ocean, space; Exact sciences and technology; hot flow anomaly; Magnetism; magnetopause; Planetology; Space; Spacecraft; models; Position; Magnetosheath; Magnetopause; case studies; pressure; monitoring; anomalies; lead; solar wind; magnetosphere; displacements; discontinuities; deformation; Magnetospheric shock wave; flow
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2012GL052636

We present a case study of a large deformation of the magnetopause on November 26, 2008. The investigation is based on observations of five THEMIS spacecraft located at the dawn flank in the magnetosphere and magnetosheath, on Cluster measurements at the dusk magnetosheath, and is supported by ACE solar wind monitoring. The main revelation of our study is that the interaction of the IMF discontinuity with the bow shock creates either one very elongated hot flow anomaly (HFA) or a pair of them that is (are) simultaneously observed at both flanks. Whereas the dusk HFA is weak and does not cause observable deformation of the magnetopause, the pressure variations connected with the dawn HFA lead to a magnetopause displacement by ≈5 RE outward from its nominal position. This is followed by a rapid inward motion of the magnetopause ≈4 RE inward with respect to the model location. The surface deformation is so large that the outermost THEMIS spacecraft was in the magnetosphere, whereas the spacecraft located 9 RE inbound entered into the magnetosheath at the same time. The whole event lasted about 5 minutes. Key Points Interaction of the IMF rotation with the bow shock Large deformation of magnetopause and bow shock surfaces Creation of a pair of HFAs at dawn and dusk