Physics of auroral phenomena : proceedings of the 40th annual seminar, Apatity, 13-17 March, 2017 / [ed. board: N. V. Semenova, A. G. Yahnin]. - Апатиты : Издательство Кольского научного центра РАН, 2017. - 143 с. : ил., табл.

THEMIS space-ground observations in midnight sector during the substorm recoveryphase Nishimura et al. (2011) have demonstrated correlation between the pulsating auroral intensity and lower-band chorus intensity observed by the satellite at the equatorial plane of the magnetosphere at 5-9 Re. However in our event the correspondence between whistler wave activity observed by the THEMIS satellite at 6.5-9.25 Re and pulsation is insignificant. 20:30 21:00 21:30 22:00 22:30 23:00 UT Figure 4, Wave activity in В and E fields and particle spectrograms at THD and ground-based magnetograms at LOZ and AND in the interval 20:30-22:40 UT on Nov 14, 2014. 3. Discussion The EEA structures, observed in our event during A3 in the midnight sector, showed similar properties to the omega bands. However, there are some differences. EEA structures were observed in the midnight sector just after Pi2 pulsations onset during substorm activation whereas omega bands are usually observed during the substorm recovery phase in the morning sector. Besides, the EEA structures show strong pulsations in the X component, which would be somewhat unusual for omega bands. Although the direct coincidence between the EEA structures and the omega bands was not found, one can suggest that these phenomena may have the same source mechanism in the near-Earth plasma sheet in the end of substorm expansion phase. Kawasaki and Rostoker (1979) have modeled the eastward propagating disturbance by a three- dimensional current system of narrow longitudinal extent (Cowling channel) in which antiparallel Birkeland current sheets are linked by southward flowing current. Downward flowing FAC located on the poleward side and upward flowing FAC on the equatorward side of the channel. In this model, the electric field is assumed to be uniform, but the conductance is enhanced inside the Cowling channel. 4. Conclusion The formation o f plasma vortices in the magnetosphere during the omega band is usually explained by two models, i.e., bursty bulk flows (BBF) ( Nishimura et al., 2011) and the Kelvin-Helmholtz instability arising in sheared flows in the equatorial regions of the tail ( Rostoker and Samson, 1984). We suggest that the omega-like (EEA) structures observed at ~7.2 Re during the substorm on 14 November 2014 are consistent with the results of Kelvin - Helmholtz type instability near the poleward boundary of the auroral oval at midnight sector o f magnetosphere. References Connors M. and G. Rostoker (1993) Source mechanisms for morning auroral features. Geophys. Res. Lett. V. 20, N. 15. P.1535-1538. Connors et al. (2003) Ps6 disturbances: relation to substorms and the auroral oval. Ann Geophys. V.21, P.493. Elphinstone R. D. et al. (1995) Observations in the vicinity of substorm onset: implications for the substormprocess. J. Geophys. Res. V.100, A5. P. 7939-7969. Kawasaki K. and G. Rostoker (1979) Perturbation magnetic fielgs and current systems associated with eastward drifting auroral structures. J. Geophys. Res. V.88, A4, P. 1464-1480. Liang J, et al. (2005) Substorm dynamics revealed by ground observations of two-dimensional auroral structures on 9 October 2000. Ann. Geophys., V23, P. 3599-3613. Nishimura Y. et al. (2011) Relations between multiple auroral streamers, pre-onset thin arc formation, and substorm auroral onset. J. Geophys. Res., V I16, doi: 10.1029/2011JA016768. Opgenoorth H. J. Persson M. A. L., Pulkkinen Т. I., Pellinen R. J. (1994) Recovery phase of magnetospheric substorms and its association with moming-sector aurora. J. Geophys. Res., V. 99, N. АЗ. P.4115-4129. Rostoker G. and Samson J.C. (1984) Can substormexpansive phase effects arid lowfrequency Pc magnetic pulsations be attributed to the same source mechanism? Geophys. Res. Lett, V.l 1, P. 271. Tanaka et al. (2015) Eastward-expanding auroral surges observed in the post-midnight sector during a multiple-onset substorm. Earth, Planets and Space, doi: 10.1186/s40623-015-0350-8. Wild J.A., and Т.К. Yeoman (2000) CUTLASS HF radar observations of high-latitude azimuthally propagating vortical currents in the nigKtside ionosphere during magnetospheric substorms. Ann. Geophys., V.l8, P. 640-652. 33