The work deals with ULF radar observations of the high-latitude ionosphere. Doppler data from the Norwegian STARE instrument are analyzed for the moderate magnetic storm observed on December 31, 1999–January 01, 2000. Upon averaging the Doppler signals along radar beams, the spectral power of signals is determined for each beam as a function of frequency ranging from 1 to 10 mHz. Sharp drops (about 10 dB) of spectral powers with frequency are found for all radar beams. A variational analysis of spectral powers is carried out by least squares, with power drops being modeled by stepwise profiles constructed of mean spectral powers preceding and succeeding the drops. Using this variational analysis, the frequency of the power drop is determined for each radar beam. Being averaged over all beams, this frequency is 4.8 ± 0.5 mHz. The results obtained are interpreted as resonant absorption of ultra-low-frequency (ULF) waves occurring on eigenfrequencies of magnetic field lines over wave propagation from the magnetopause deep into the magnetosphere.
ULF waves, electric fields, high-latitude ionosphere
1. Allan W., Knox F.B. A dipole field model for an axisymmetric Alfven wave with finite ionosphere conductivities. Planet. Space Sci. 1979, vol. 27, no. 1, pp. 79–85.
2. Allan W., Poulter E.M., Nielsen E. STARE observations of a Pc5 pulsation with large azimuthal wave number. J. Geophys. Res. 1982, vol. 87, no. A8. pp. 6163–6172.
3. Alperovich L.S., Fedorov E.N. Hydromagnetic waves in the magnetosphere and the ionosphere. New York: Springer, 2007. 421 p.
4. Anderson B.J., Engebretson M.J., Zanetti L.J. Distortion effects in spacecraft observations of MHD toroidal standing waves: Theory and observations J. Geophys. Res. 1989, vol. 94, no. A10, pp. 13425–13445.
5. Badin V.I. Excitation and absorption of ULF oscillations from Doppler radar observation at high latitudes. Geomagnetizm i aeronomiya [Geomagnetism and Aeronomy]. 2016, vol. 56, no. 1, pp. 93–101. (In Russian).
6. Belakhovsky V.B., Kozlovsky A.E., Pilipenko V.A. Determination of the latitudinal profile of the resonant frequency of Pc5 pulsations from EISCAT radar data. Vestnik Kol’skogo nauchnogo tsentra RAN [Bull. of Kola Scientific Centre RAS] 2015, vol. 22, no. 3, pp. 64–72. (In Russian).
7. Bland E.C., McDonald A.J. High spatial resolution radar observations of ultralow frequency waves in the southern polar cap. J. Geophys. Res. Space Phys. 2016, vol. 121, pp. 4005–4016. DOI: 10.1002/2015JA022235.
8. Chelpanov M.A., Mager P.N., Klimushkin D. Yu., Berngardt O.I., Mager O.V. Experimental evidence of the drift of compressional waves in the magnetosphere: An Ekaterinburg coherent decameter radar case study. J. Geophys. Res. Space Phys. 2016, vol. 121, pp. 1315–1326. DOI: 10.1002/ 2015JA022155.
9. Chen L., Hasegawa A. A theory of long-period magnetic pulsations: 1. Steady state excitation of field line resonance. J. Geophys. Res. 1974, vol. 79, no. A7, pp. 1024–1032.
10. Cheng C.Z., Zaharia S. Field line resonances in quiet and disturbed time three-dimensional magnetospheres. J. Geophys. Res. 2003, vol. 108, no. A1. 1001. DOI: 10.1029/2002JA009471.
11. Greenwald R.A., Weiss W., Nielsen E., Thomson N.R. STARE: A new radar auroral backscatter experiment in northern Scandinavia. Radio Sci. 1978, vol. 13, no. 6, pp. 1021–1039.
12. Guglielmi A.V., Potapov A.S. On the peculiarity of MHD wave field in inhomogeneous plasma. Issledovaniya po geomagnetizmu, aeronomii i fizike Solntsa [Research on geomagnetism, Aeronomy and Solar Physics]. 1984, iss. 70, pp. 149–157. (In Russian).
13. Hardy D.A., Gussenhoven M.S., Raistrick R., McNeil W.J. Statistical and functional representations of the pattern of auroral energy flux, number flux, and conductivity. J. Geophys. Res. 1987, vol. 92, no. A11, pp. 12275–12294.
14. James M.K., Yeoman T.K., Mager P.N., Klimushkin D.Yu. Multiradar observations of substorm-driven ULF waves. J. Geophys. Res. Space Phys. 2016, vol. 121, pp. 5213–5232. DOI: 10.1002/2015JA022102.
15. Kivelson M.G., Southwood D.J. Coupling of global magnetospheric MHD eigenmodes to field line resonances. J. Geophys. Res. 1986, vol. 91, no. A4, pp. 4345–4351.
16. Krinberg I.A., Tashchilin A.V. Ionosfera i plazmosfera [Ionosphere and Plasmasphere]. Moscow, Nauka Publ., 1984. 189 p. (In Russian).
17. Lanzerotti L.J., Shono A., Fukunishi H., Maclennan C.G. Long-period hydromagnetic waves at very high geomagnetic latitudes. J. Geophys. Res. 1999, vol. 104, no. A12, pp. 28423–28435.
18. Lee D.-H., Lysak R.L. Magnetospheric ULF wave coupling in the dipole model: Impulsive excitation. J. Geophys. Res. 1989, vol. 94, no. A12, pp. 17097–17103.
19. Leonovich A.S., Mazur V.A. Eigen ultralow frequency magnetoacoustic oscillations of near plasma layer. Kosmicheskie issledovaniya [Cosmic Research]. 2008, vol. 46, no. 4, pp. 336−343. (In Russian).
20. Mager P.N., Berngardt O.I., Klimushkin D.Yu., Zolotukhina N.A., Mager O.V. First results of the high-resolution multibeam ULF wave experiment at the Ekaterinburg SuperDARN radar: ionospheric signatures of coupled poloidal Alfvén and drift-compressional modes. J. Atmos. Solar-Terr. Phys. 2015, vol. 130–131, pp. 112–126.
21. Menk F.W., Waters C.L., Fraser B.J. Field line resonances and waveguide modes at low latitudes. 1. Observations. J. Geophys. Res. 2000, vol. 105, no A4, pp. 7747–7761.
22. Newton R.S., Southwood D.J., Hughes W.J. Damping of geomagnetic pulsations by the ionosphere. Planet. Space Sci. 1978, vol. 26, no. 3, pp. 201–209.
23. Nishida A. Geomagnitnyi diagnoz magnitosfery [Geomagnetic diagnosis of the magnetosphere]. Moscow, Mir Publ., 1980. 299 p. (In Russian).
24. Poulter E.M., Allan W. Transient ULF pulsation decay rates observed by ground based magnetometers: The contribution of spatial integration. Planet. Space Sci. 1985, vol. 33, no. 6, pp. 607–616.
25. Pilipenko V., Belakhovsky V., Kozlovsky A., Fedorov E., Kauristie K. Determination of the wave mode contribution into the ULF pulsations from combined radar and magnetometer data: Method of apparent impedance. J. Atmosph. Solar-Terr. Phys. 2012, vol. 77, no. 1, pp. 85–95.
26. Roelof E.C., Sibeck D.G. Magnetopause shape as a bivariate function of the interplanetary magnetic field B z and solar wind dynamic pressure. J. Geophys. Res . 1993, vol. 98, no. A12, pp. 21421–21450.
27. Southwood D.J. Some features of field resonances in the magnetosphere. Planet. Space Sci. 1974, vol. 22, no. 3, pp. 483–491.
28. Tsyganenko N.A. Modeling the Earth's magnetospheric magnetic field confined within a realistic magnetopause. J. Geophys. Res. 1995, vol. 100, no. A4, pp. 5599–5612.
29. Urban, K.D., Gerrard A.J., Bhattacharya Y., Ridley A.J., Lanzerotti L.J., Weatherwax A. T. Quiet time observations of the open-closed boundary prior to the CIR-induced storm of 9 August 2008. Space Weather. 2011, vol. 9, S11001. DOI: 10.1029/2011SW000688.
30. Walker A.D.M., Greenwald R.A., Stuart W.F., Green C.A. Stare auroral radar observations of Pc5 geomagnetic pulsations. J. Geophys. Res. 1979, vol. 84, no. A7, pp. 3373–3388.
31. Wallis D.D., Budzinski E.E. Empirical models of height integrated conductivities. J. Geophys. Res. 1981, vol. 86, no. A1, pp. 125–137.
32. Yumoto K., Pilipenko V., Fedorov E., Kurneva N., Shiokawa K. The mechanisms of damping of geomagnetic pulsations. J. Geomagnenism Geoelectricity. 1995, vol. 47, no. 1, pp. 163–176.