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Volume 22, issue 1
Ann. Geophys., 22, 183–212, 2004
https://doi.org/10.5194/angeo-22-183-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 183–212, 2004
https://doi.org/10.5194/angeo-22-183-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Jan 2004

01 Jan 2004

Magnetosheath-cusp interface

S. Savin1, L. Zelenyi1, S. Romanov1, I. Sandahl2, J. Pickett13, E. Amata6, L. Avanov1, J. Blecki9, E. Budnik1, J. Büchner10, C. Cattell15, G. Consolini6, J. Fedder11, S. Fuselier7, H. Kawano4, S. Klimov1, V. Korepanov16, D. Lagoutte12, F. Marcucci6, M. Mogilevsky1, Z. Nemecek8, B. Nikutowski10, M. Nozdrachev1, M. Parrot12, J. L. Rauch12, V. Romanov1, T. Romantsova1, C. T. Russell5, J. Safrankova8, J. A. Sauvaud14, A. Skalsky1, V. Smirnov1, K. Stasiewicz9,3, J. G. Trotignon12, and YU. Yermolaev1 S. Savin et al.
  • 1Space Research Institute, Russian Academy of Sciences, Profsoyuznaya 84/32, Moscow, 117810, Russia
  • 2Swedish Inst. Space Physics, Kiruna, Sweden
  • 3Swedish Inst. Space Physics, Uppsala, Sweden
  • 4Kyushu University, Japan
  • 5IGPP, UCLA, USA
  • 6Interplanetary Space Phys. Inst., CNR, Roma, Italy
  • 7Lockheed Martin Alto Res. Lab., CA, USA
  • 8Faculty Math. Phys., Charles U., Praha, Czech Republic
  • 9Space Res. Center, Polish Academy Sci., Warsaw, Poland
  • 10Max-Planck Inst. Aeronomie, Katlenburg-Lindau, Germany
  • 11Naval Research Lab., Washington, USA
  • 12Laboratory Phys. Chemistry Environment, Orleans, France
  • 13University of Iowa, USA
  • 14Centre d’Etude Spatiale des Rayonnements, Toulouse, France
  • 15University of Minnesota, USA
  • 16Lviv Center for Space Researches, Ukraine

Abstract. We advance the achievements of Interball-1 and other contemporary missions in exploration of the magnetosheath-cusp interface. Extensive discussion of published results is accompanied by presentation of new data from a case study and a comparison of those data within the broader context of three-year magnetopause (MP) crossings by Interball-1. Multi-spacecraft boundary layer studies reveal that in ∼80% of the cases the interaction of the magnetosheath (MSH) flow with the high latitude MP produces a layer containing strong nonlinear turbulence, called the turbulent boundary layer (TBL). The TBL contains wave trains with flows at approximately the Alfvén speed along field lines and "diamagnetic bubbles" with small magnetic fields inside. A comparison of the multi-point measurements obtained on 29 May 1996 with a global MHD model indicates that three types of populating processes should be operative:

  • large-scale (∼few RE) anti-parallel merging at sites remote from the cusp;
  • medium-scale (few thousandkm) local TBL-merging of fields that are anti-parallel on average;
  • small-scale (few hundredkm) bursty reconnection of fluctuating magnetic fields, representing a continuous mechanism for MSH plasma inflow into the magnetosphere, which could dominate in quasi-steady cases.

The lowest frequency (∼1–2mHz) TBL fluctuations are traced throughout the magnetosheath from the post-bow shock region up to the inner magnetopause border. The resonance of these fluctuations with dayside flux tubes might provide an effective correlative link for the entire dayside region of the solar wind interaction with the magnetopause and cusp ionosphere. The TBL disturbances are characterized by kinked, double-sloped wave power spectra and, most probably, three-wave cascading. Both elliptical polarization and nearly Alfvénic phase velocities with characteristic dispersion indicate the kinetic Alfvénic nature of the TBL waves. The three-wave phase coupling could effectively support the self-organization of the TBL plasma by means of coherent resonant-like structures. The estimated characteristic scale of the "resonator" is of the order of the TBL dimension over the cusps. Inverse cascades of kinetic Alfvén waves are proposed for forming the larger scale "organizing" structures, which in turn synchronize all nonlinear cascades within the TBL in a self-consistent manner. This infers a qualitative difference from the traditional approach, wherein the MSH/cusp interaction is regarded as a linear superposition of magnetospheric responses on the solar wind or MSH disturbances.

Key words. Magnetospheric physics (magnetopause, cusp, and boundary layers) – Space plasma physics (turbulence; nonlinear phenomena)

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