Spatio-temporal structure of poloidal alfvén waves in the magnetosphere

1Klimushkin, DYu., 1Mager, PN, 1Zolotukhina, NA
1Institute of Solar-Terrestrial Physics, Siberian Branch of Russian Academy of Sciences, Irkutsk, Russia
Kosm. nauka tehnol. 2010, 16 ;(1):46-54
Publication Language: English
This paper overviews some recent studies of spatio-temporal structure of poloidal (high-m) Alfvén waves (Pc4-5) in the magnetosphere, with taking into account finite field line curvature and plasma pressure. The effects of finite pressure plasma are especially essential near the magnetospheric equator, where an opaque region for Alfvén waves can be formed. This region is bounded by two turning points which restrain penetration of the wave energy far from the ionosphere, and an Alfvén resonator appears on a part of the field line adjacent to the ionosphere. Due to this effect the ULF pulsations in the Northern and Southern hemispheres can be non-conjugated.
              Another result is a peculiar field-aligned structure of the wave magnetic field: its fundamental harmonic must have three nodes, rather than one node as with cold plasma. The transverse structure of the wave is determined by the excitation mechanism. It is supposed in the report that wave is emitted by an alternating current created by the drifting particle cloud or ring current inhomogeneity. It is shown that the wave appears in some azimuthal location simultaneously with the particle cloud arrival at the same spot. The wave propagate westward, in the direction of the proton drift. The expected properties of the wave (amplitude, polarization, hodogram) are close to the observed properties of poloidal ULF pulsations.
Keywords: Alfven waves, magnetic field, plasma
1. Anderson B. J., Potemra T. A., Zanetti L. J., et al. Statistical correlation between Pc3—5 pulsations and solar wind/ IMF parameters and geomagnetic indices. Physics of Space Plasmas: SPI Conference Proceedings and Reprint Series, Eds T. Chang, G. B. Crew,J. B. Jasperse, Vol. 10, 419—429 (Scientific Publishers Inc., Cambridge, Massachusetts, 1991).
2. Eriksson P. T. I., Blomberg L. G., Walker A. D. M., et al. Poloidal ULF oscillations in the dayside magnetosphere: a Cluster study. Ann. Geophys., 23, 2679— 2686 (2005).
3. Frey H. U., Mende S. B., Angelopoulos V., et al. Substorm onset observations by IMAGE-FUV. J. Geophys. Res., 109, A10304 (2004).
4. Guglielmi A. V., Zolotukhina N. A. Excitation of Alfvén oscillations of the magnetosphere by the asymmetric ring current. Issled. geomagn. aeron. i fiz. Solntsa, 50, 129—137 (1980) [in Russian].
5. Kadomtsev B. B. Hydromagnetic stability of plasma. In: Voprosy teorii plazmy, Ed. by M. A. Leontovich, 132—176 (Gosatomizdat, Moscow, 1963) [in Russian].
6. Klimushkin D. Yu., Mager P. N. The spatio-temporal structure of impulse-generated azimuthal small-scale Alfvén waves interacting with high-energy charged particles in the magnetosphere. Ann. Geophys., 22, 1053—1060 (2004).
7. Klimushkin D. Yu., Mager P. N., Glassmeier K.-H. Toroidal and poloidal Alfvén waves with arbitrary azimuthal wave numbers in a finite pressure plasma in the Earth’s magnetosphere. Ann. Geophys., 22, 267—288 (2004).
8. Leonovich A. S., Mazur V. A. A theory of transverse small scale standing Alfvén waves in an axially symmetric magnetosphere. Planet. Space Sci., 41, 697—717 (1993).
9. Leonovich A. S., Mazur V. A. Standing Alfvén waves in an axisymmetric magnetosphere excited by a non-stationary source. Ann. Geophys., 16, 914—920 (1998).
10. Mager P. N., Klimushkin D. Yu. Alfvén ship waves: high-m ULF pulsations in the magnetosphere, generated by a moving plasma inhomogeneity. Ann. Geophys., 26, 1653—1663 (2008).
11. Mager P. N., Klimushkin D. Yu., Ivchenko N. On the equa-torward phase propagation of high- m ULF pulsations observed by radars. J. Atmospheric and Solar-Terrestrial Phys., 71, 1677—1680 (2009).
12. Mager P. N., Klimushkin D. Yu., Pilipenko V. A., et al. Field-aligned structure of poloidal Alfvén waves in a finite pressure plasma. Ann. Geophys., 27 (2009).
13. Pilipenko V. A., Mazur N. G., Fedorov E. N., Engebret-son M. J., et al. Alfvén wave reflection in a curvilinear magnetic field and formation of Alfvénic resonators on open field lines. J. Geophys. Res., 110, A10S05 (2005).
14. Roederer J. G. Dynamics of geomagnetically trapped radiation.(Springer-Verlag, New York, 1970).
15. Schäfer S., Glassmeier K.-H., Eriksson P. T. I., et al. Spatio-temporal structure of a poloidal Alfven wave detected by Cluster adjacent to the dayside plasmapause. Ann. Geophys., 26, 1805—1817 (2008).
16. Wright D. M., Yeoman T. K., Rae I. J., et al. Ground-based and Polar spacecraft observations of a giant (Pg) pulsation and its associated source mechanism. J. Geophys. Res., 106, 10837—10852 (2001).
17. Yeoman T. K., Wright D. M., Baddeley L. J. Ionospheric sigatures of ULF waves: active radar techniques. In: Magnetospheric ULF waves: Synthensis and New Directions. Geophys. monograph ser., No. 169, 273— 288 (2006).