References

ANGEO

Annales Geophysicae

ANGEO

Ann. Geophys.

1432-0576

Copernicus Publications

Göttingen, Germany

10.5194/angeo-30-1703-2012

THEMIS observations of plasma transport via eddy diffusion

Izutsu

¹ Fujimoto

Department of Earth and Planetary Science, The University of Tokyo, Tokyo, Japan

Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, Kanagawa, Japan

17 12 2012

30 12 1703 1707

2012

This work is licensed under the Creative Commons Attribution 3.0 Unported License. To view a copy of this licence, visit https://creativecommons.org/licenses/by/3.0/

This article is available from https://angeo.copernicus.org/articles/30/1703/2012/angeo-30-1703-2012.html

The full text article is available as a PDF file from https://angeo.copernicus.org/articles/30/1703/2012/angeo-30-1703-2012.pdf

We provide an event study of THEMIS observations of the low-latitude boundary layer in the dayside magnetosphere. Simultaneous multipoint observations obtained on 5 December 2008 show that the magnetosheath-like plasma in the low-latitude boundary layer is transferred earthward from the magnetopause. This earthward transport is accompanied by decrease in the density and fluctuating bulk flow. We calculate the eddy diffusion coefficients, which can be estimated from the observed velocity data, and found that the numbers are in good quantitative agreement with the spatial and time scales of the observed earthward transport signatures. It is shown that other possible plasma transport processes such as convection or diffusion induced by plasma wave turbulence are inconsistent with the observations. Our study strongly suggests that the observed transport is due to diffusive transport via turbulent eddy motions as is the case of an ordinary (Navier–Stokes) fluid.

References 1

Angelopoulos, V.: The THEMIS Mission, Space Sci. Rev., 141, 5–34, <a href="http://dx.doi.org/10.1007/s11214-008-9336-1">https://doi.org/10.1007/s11214-008-9336-1</a>, 2008.

Antonova, E. E.: The structure of the magnetospheric boundary layers and the magnetospheric turbulence, Planet. Space Sci., 53, 161–168, <a href="http://dx.doi.org/10.1016/j.pss.2004.09.041">https://doi.org/10.1016/j.pss.2004.09.041</a>, 2005.

Antonova, E. E. and Ovchinnikov, I. L.: Magnetostatically equilibrated plasma sheet with developed medium-scale turbulence: Structure and implications for substorm dynamics, J. Geophys. Res., 104, 17289–17298, <a href="http://dx.doi.org/10.1029/1999JA900141">https://doi.org/10.1029/1999JA900141</a>, 1999.

Bauer, T. M., Treumann, R. A., and Baumjohann, W.: Investigation of the outer and inner low-latitude boundary layers, Ann. Geophys., 19, 1065–1088, <a href="http://dx.doi.org/10.5194/angeo-19-1065-2001">https://doi.org/10.5194/angeo-19-1065-2001</a>, 2001.

Borovsky, J. E., Elphic, R. C., Funsten, H. O., and Thomsen, M. F.: The Earth's plasma sheet as a laboratory for flow turbulence in high-β MHD, J. Plasma Physics, 57, 1–34, <a href="http://dx.doi.org/10.1017/S0022377896005259">https://doi.org/10.1017/S0022377896005259</a>, 1997.

Borovsky, J. E., Thomsen, M. F., and Elphic, R. C.: The driving of the plasma sheet by the solar wind, J. Geophys. Res., 103, 17617–17640, <a href="http://dx.doi.org/10.1029/97JA02986">https://doi.org/10.1029/97JA02986</a>, 1998.

Borovsky, J. E. and Gary, S. P.: On shear viscosity and the Reynolds number of magnetohydrodynamic turbulence in collisionless magnetized plasmas: Coulomb collisions, Landau damping, and Bohm diffusion, Phys. Plasmas, 16, 082307, <a href="http://dx.doi.org/10.1063/1.3155134">https://doi.org/10.1063/1.3155134</a>, 2009.

Hasegawa, A. and Mima, K.: Anomalous transport produced by kinetic Alfvéen wave turbulence, J. Geophys. Res., 83, 1117–1123, <a href="http://dx.doi.org/10.1029/JA083iA03p01117">https://doi.org/10.1029/JA083iA03p01117</a>, 1978.

Hinze, J. O.: Theory of Space Plasma Microinstabilities, McGraw-Hill, New York, 1975.

McFadden, J. P., Carlson, C. W., Larson, D., Ludlam, M., Abiad, R., Elliott, B., Turin, P., Marckwordt, M., and Angelopoulos, V.: The THEMIS ESA Plasma Instrument and Inflight Calibration, Space Sci. Rev., 141, 277–302, <a href="http://dx.doi.org/10.1007/s11214-008-9440-2">https://doi.org/10.1007/s11214-008-9440-2</a>, 2008.

Mitchell, D. G., Kutchko, F., Williams, D. J., Eastman, T. E., and Frank, L. A.: An extended study of the low-latitude boundary layer on the dawn and dusk flanks of the magnetosphere, J. Geophys. Res., 92, 7394–7404, <a href="http://dx.doi.org/10.1029/JA092iA07p07394">https://doi.org/10.1029/JA092iA07p07394</a>, 1987

Øieroset, M., Phan, T. D., Angelopoulos, V., Eastwood, J. P., McFadden, J., Larson, D., Carlson, C. W., Glassmeier, K. H., Fujimoto, M., and Raeder, J.: THEMIS multi-spacecraft observations of magnetosheath plasma penetration deep into the dayside low-latitude magnetosphere for northward and strong By IMF, Geophys. Res. Lett., 35, L17S11, <a href="http://dx.doi.org/10.1029/2008GL033661">https://doi.org/10.1029/2008GL033661</a>, 2008.

Phan, T. D. and Paschmann, G.: Low-latitude dayside magnetopause and boundary layer for high magnetic shear 1. Structure and motion, J. Geophys. Res., 101, 7801–7816, <a href="http://dx.doi.org/10.1029/95JA03752">https://doi.org/10.1029/95JA03752</a>, 1996.

Schwartz, S. J.: Shock and Discontinuity Normals, Mach Numbers, and Related Parameters, ISSI Scientific Reports Series, 1, 249–270, 1998.

Sonnerup, B. U. O.: Theory of the low-latitude boundary layer, J. Geophys. Res., 85, 2017–2026, <a href="http://dx.doi.org/10.1029/JA085iA05p02017">https://doi.org/10.1029/JA085iA05p02017</a>, 1980.

Stepanova, M., Pinto, V., Valdivia, J. A., and Antonova, E. E.: Spatial distribution of the eddy diffusion coefficients in the plasma sheet during quiet time and substorms from THEMIS satellite data, J. Geophys. Res., 116, A00I24, <a href="http://dx.doi.org/10.1029/2010JA015887">https://doi.org/10.1029/2010JA015887</a>, 2011.

Treumann, R. A., Labelle, J., and Bauer, T. M.: Diffusion Processes: An Observational Perspective, p. 331, the American Geophysical Union, 1995.

Wang, C.-P., Lyons, L. R., Nagai, T., Weygand, J. M., and Lui, A. T. Y.: Evolution of plasma sheet particle content under different interplanetary magnetic field conditions, J. Geophys. Res., 115, A06210, <a href="http://dx.doi.org/10.1029/2009JA015028">https://doi.org/10.1029/2009JA015028</a>, 2010.

Wing, S., Johnson, J. R., and Fujimoto, M.: Timescale for the formation of the cold-dense plasma sheet: A case study, Geophys. Res. Lett., 33, L23106, <a href="http://dx.doi.org/10.1029/2006GL027110">https://doi.org/10.1029/2006GL027110</a>, 2006.