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Walen and Slow-mode Shock Analyses Applied to High-Speed Flows of the Near-Earth Magnetotail

S. Eriksson 1 , C. Mouikis 2 , M. W. Dunlop 3 , M. Oieroset 4 , D. N. Baker 1 , C. Cully 1 , H. Reme 5 , and A. Balogh 6 1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA 2 Space Science Center, University of New Hampshire, Durham, USA

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Walen and Slow-mode Shock Analyses Applied to High-Speed Flows of the Near-Earth Magnetotail

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  1. S. Eriksson1, C. Mouikis2, M. W. Dunlop3, M. Oieroset4, D. N. Baker1, C. Cully1, H. Reme5, and A. Balogh6 1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, USA 2 Space Science Center, University of New Hampshire, Durham, USA 3 Rutherford Appleton Laboratory, Chilton, UK 4 Space Sciences Laboratory, University of California, Berkeley, USA 5 Centre d’Etude Spatiale des Rayonnements, Toulouse, France 6 Imperial College, London, UK Walen and Slow-mode Shock Analyses Applied to High-Speed Flows of the Near-Earth Magnetotail Contact information: eriksson@lasp.colorado.edu

  2. Outline • Introduction • Tail reconnection and slow-mode shocks • deHoffmann-Teller and Walen analyses • Slow-mode shock criteria • Cluster observations 2001-08-27 from 03:50 UT to 04:35 UT 2001-09-15 from 03:55 UT to 05:20 UT 2002-08-21 from 07:50 UT to 08:40 UT • Summary

  3. Tail Reconnection and Slow-mode Shocks [Feldman et al., JGR, 92, 83, 1987] [Hill, T.W., JGR, 80, 4689, 1975] • Acceleration in tail reconnection is assumed to take place across a slow-mode shock (SS) connected to the diffusion region. • SS generated due to near-symmetric conditions (comparable plasma density and magnetic field strength) on either side of the current layer. • Configuration essentially that of Petschek [1964] (above right).

  4. Tail Reconnection and Slow-mode Shocks [Feldman et al., JGR, 92, 83, 1987] [Hill, T.W., JGR, 80, 4689, 1975] • Slow-mode shocks were first observed in the tail by e.g. Feldman et al. [1984, 1987] using the Rankine-Hugoniot (RH) jump conditions on ISEE 2 data. • Later confirmed by Geotail RH observations [e.g. Saito et al., 1995; Seon et al., 1996] and by Wind data [Oieroset et al., 2000] using the shear-stress balance test on Wind data 60 Re downtail.

  5. deHoffmann-Teller Analysis [Khrabrov and Sonnerup, ISSI Sci.rep., 1998] • The existence of an HT frame indicates the presence of a quasi-stationary coherent pattern of magnetic field and plasma velocity.

  6. Shear-Stress Balance (Walen) Test • Disturbance generated by reconnection propagates away from the diffusion region at a field-aligned phase speed in the HT shock frame determined by the type and strength of the shock.

  7. Shear-Stress Balance (Walen) Test • The sign of the Walen slope depends on whether the B-field is parallel or antiparallel to the flow direction.

  8. Walen Analysis in the Magnetotail Walen slope Oieroset et al., JGR, 105, 25,247, 2000.

  9. Walen Analyses at Wind (x= -60 Re) Oieroset et al., JGR, 105, 25,247, 2000. • Earthward jet • Negative Bx • Walen slope • should be positive (Note that there is no ion composition in the Wind data set and that these slopes were derived assuming 100% H+.)

  10. Slow-mode Shock Criteria

  11. Cluster Observations on 2001-08-27 A B C

  12. Walen Analyses 2001-08-27 A: Tailward flows in Northern Hemisphere

  13. Walen Analyses 2001-08-27 B: Earthward flows in Northern Hemisphere

  14. Walen Analyses 2001-08-27 C: Earthward flows in Northern Hemisphere

  15. Shock Analysis on 2001-08-27 A B C A C

  16. Shock Normal Optimization 2001-08-27

  17. Cluster Observations on 2001-09-15 A B C

  18. Walen Analyses 2001-09-15 A: Tailward flows in Northern Hemisphere

  19. Walen Analyses 2001-09-15 B: Tailward flows in Northern Hemisphere

  20. Walen Analyses 2001-09-15 C: Tailward flows in Southern Hemisphere

  21. Shock Analysis on 2001-09-15 A B C A B

  22. Cluster Observations on 2002-08-21 A B C

  23. Walen Analyses 2002-08-21 A: Tailward flows in Northern Hemisphere

  24. Walen Analyses 2002-08-21 B: Tailward flows in Northern Hemisphere

  25. Walen Analyses 2002-08-21 C: Tailward flows in Southern Hemisphere

  26. Shock Analysis on 2002-08-21 A B C B

  27. Summary • The Walen test together with the location of Cluster suggest the presence of slow-mode shocks on the tailward sides of near-Earth X-lines (X>-19 Re) for three events: 2001-08-27, 2001-09-15, 2002-08-21. • Earthward jets seemingly fail the Walen test more readily than tailward jets. • Joint Walen and RH analyses generally confirm the presence of slow-mode shocks during accelerated tailward flows. Based on three events and several jets. • Shock-normal analyses suggest that magnetic coplanarity theorem results in a normal near the optimized (minimum RH deviations) direction.

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