Dynamics of the low latitude terrestrial magnetopause from THEMIS measurements

1Agapitov, AV
1Taras Shevchenko National University of Kyiv, Kyiv, Ukraine
Kosm. nauka tehnol. 2009, 15 ;(1):19-30
Publication Language: Russian
Multi-spacecraft THEMIS observations in temporal orbit during March ‒ September 1997 provide a unique opportunity to collect material on the dayside magnetopause surface dynamics. During this period THEMIS crossed the magne-topause surface more than 300 times. About half of observed crossings were found to be a multicrossing (several inward and outward crossing of a single spacecraft during short-term interval). Taking into account the magnetopause surface normal velocity magnitude (averaged normal velocity is about 40 km/s), we speculate what periodic oscillations of the magne-topause position were observed. Two types of the magneto-pause motion, namely, «flapping» (one-dimensional change of surface position) and «waving» (two-dimensional structure propagation) were found. Amplitudes of observed oscillations were estimated to be in the range of (0.1‒2.2)RE. The algorithm based on minimum variance analysis for surface normal definition, the Hoffman-Theller and timing surface velocity definition technique is proposed to distinguish these two types of the magnetopause surface dynamics. Two-dimensional wavelike travelling disturbances were found mainly on the flanks of the magnetosphere. The magneto-pause motion normal velocity was found to lie in the range of 50 to 150 km/s. One-dimensional flapping of the surface (the magnetopause motion normal velocity was found to be in the range from 10 to 70 km/s) was observed predominantly in the midday magnetosphere sector.
                    We speculate that such quasi-periodic motion is the manifestation of the same phenomena in different magnetosphere regions. The generation can be initiated by dayside magnetosphere cavity modes (such events were associated with the magnetopause surface oscillations in several cases) or quasiperiodic changes of solar wind parameters. Surface disturbances are driven by magnetosheath plasma flow tailward with velocity about 140‒180 km/s. In the case of periodic oscillations of the subsolar magnetopause the wavelike structures can be observed on the flanks of the mag-netopause. The amplitude of surface disturbances can be increased by the Kelvin ‒ Helmholtz instability.
Keywords: flapping, magnetopause, waving
1. Anderson K., Binsack J., Fairfield D. Hydromagnetic disturbances of 3- to 15-minute period on the magnetopause and their relation to bow shock spikes. J. Geophys. Res., 73 (7), 2371—2386 (1968).
2. Angelopoulos V. The THEMIS mission. Space Sci. Rev., 141, 5—34 (2008).
3. Auster H. U. et al. The THEMIS fluxgate magnetometer. Space Sci. Rev., 141, 235—264 (2008).
4. Boller B., Stolov H. Explorer 18 study of the stability of the magnetopause using a Kelvin-Helmholtz instability criterion. J. Geophys. Res., 78 (34), 8078 — 8086 (1973).
5. Cahill L., Winckler J. Periodic magnetopause oscillations observed with the GOES satellites on March 24. J. Geophys. Res., 97A (6), 8239—8243 (1992).
6. Contin J. E., Gratton F. T., Farrugia C. J. Theoretical results on the latitude dependence of the Kelvin-Helmholtz instability at the dayside magnetopause for northward interplanetary magnetic fields. J. Geophys. Res., 108A (6), P. 1227 (2003).
7. DeHoffmann F., Teller E. Magnetohydrodynamic shocks. Phys. Rev., 80, P. 692 (1950).
8. Dunlop M.W., Balogh A., Glassmeier K.-H. Four-point CLUSTER application of magnetic field analysis tools: the discontinuity analyzer. J. Geophys. Res., 107A (11) (2002).
9. Fairfield D. H. Average and unusual locations of the Earth’s magnetopause and bow shock. J. Geophys. Res., 76, 6700—6716 (1971).
10. Khrabrov V. A., Sonnerup B.U. O. Orientation and motion of current layers: Minimization of the Faraday residue. Geophys. Res. Lett., 25, 2373—2376 (1998).
11. Khrabrov V. A., Sonnerup B. U. O. DeHoffmann-Teller analysis. In: Analysis Methods for Multi-Spacecraft Data, Eds G. Paschmann, P. W. Daly, 1850 p. (ESA Publ. Div., Noordwijk, Netherlands, 1998).
12. Kivelson M. G., Chen S. H. The magnetopause: Surface waves and instabilities and their possible dynamical consequences. AGU Monograph 90, Physics of Magnetopause, Eds P. Song, B.U.O. Sonnerup, P. 257 (Washington, D.C., 1995).
13. Kokubun S., Kawano H., Mukai T., et al. Surface waves on the dawn magnetopause: Connection with ground PC 5 pulsations. Adv. Space Res., 25 (7–8), 1493—1502 (2000).
14. McFadden J. P., Carlson C. W., Larson D., et al. The THEMIS ESA plasma instrument and in-flight calibration. Space Sci. Rev., 141, 277—302 (2008).
15. Owen C. J., Taylor M. G. G. T., Krauklis I. C., et al. Cluster observations of surface waves on the dawn flank magnetopause. Ann. Geophys., 22, 971—983 (2004).
16. Paschmann G., Haaland S., Sonnerup B. U. O., et al. Characteristics of the near-tail dawn magnetopause and boundary layer. Ann. Geophys., 23, 1481— 1497 (2005).
17. Phan T. D., Paschmann G. Low-latitude dayside magnetopause and boundary layer for high magnetic shear 1. Structure and motion. J. Geophys. Res., 101, 7801 — 7816 (1996).
18. Russell C. T., Mellott M. M., Smith E. J., King J. H. Multiple spacecraft observations of interplanetary shocks: Four spacecraft determination of shock normals. J. Geophys. Res., 88, 4739—4748 (1983).
19. Russell C. T., Petrinec S. M., Zhang T. L., et al. The effect of foreshock on the motion of the dayside magnetopause. Geophys. Res. Lett., 24, 1439—1442 (1997).
20. Shafrankova J., Zastenker G., Nemecek Z., et al. Small scale observation of magnetopause motion: preliminary results of the INTERBALL project. Ann. Geophys., 15, 562—569 (1997).
21. Smith E., Davis L. Magnetic measurements in the Earth’s magnetosphere and magnetosheath: Mariner 5. J. Geophys. Res., 75 (7), 1233—1245 (1970).
22. Song P., Russell C., Fitzenreiter R., et al. Structure and properties of the subsolar magnetopause for northward interplanetary magnetic field: Multiple-instrument particle observations. J. Geophys. Res., 98A (7), 11319—11337 (1993).
23.Sonnerup B. U. O., Scheible M. Minimum and maximum variance analysis. In: Analysis Methods for Multi-Spacecraft Data, Eds G. Paschmann, P. W. Daly, 1850 p. (ESA Publ. Div., Noordwijk, Netherlands, 1998).
24. Walker A. D. M. The Kelvin-Helmholtz instability in the low-latitude boundary layer. Planet. Space Sci., 829, 1119—1133 (1981).