PROBLEMS OF GEOCOSMOS

Proceedings of the 7th International Conference "Problems of Geocosmos" (St. Petersburg, Russia, 26-30 May 2008)
Fig. 5 Observation of the diffuse aurora and SAR
arc dynamics on February 11, 2000 during the
convectional activity enhancement without intense
substorms. The data are presented as in Fig. 3.
Fig. 6 Dynamics of luminosity pulsations in the
N2 + emissions at the latitudes of diffuse aurora
and SAR arc during the convectional activity
enhancement on February 11, 2000.
The data are presented as in Fig. 3. In the bottom
panel the time interval of correlation analysis of the
luminosity pulsations is indicated by a gray column.
a changing dawn-dusk Ey from 1430 UT took place smoothly brightening and equatorward expansion of DA
in the 557.7 nm emission. The intensification of quasi-stationary activity caused the formation of the redband
and the short-term SAR arc equatorward of DA and zenith of observation station. In the region of an
amplified red luminescence at 1630-1900 UT the intensity splashes of the 427.8 nm emission were observed
in the magnetic zenith (see Fig. 5d). Auroral activity slowly decreased after 1800 UT at a northern IMF Bz.
Fig. 6 shows the analysis results of luminosity pulsations in the N2 + emissions during observations of DA
and SAR arc dynamics on February 11, 2000 (see Fig. 5). It is seen that the development of luminosity pulsations
began at ~ 1630 UT synchronously in three directions. At this time the N- photometer registered the
pulsations in DA. Simultaneously Z and S-photometers did it at latitudes of a forming SAR arc (see keogrms
in Fig. 5). Dynamic spectra of the luminosity pulsations in three directions are similar and have discrete
maxima in the frequency range of 0.05-0.1 Hz. The amplitude of harmonics in the power spectrum of pulsations
in DA is approximately greater by an order of the amplitude of harmonics at latitudes of the SAR arc.
3. Discussion
The analysis of photometric observations submitted above shows a clear manifestation of enhancement
of the SW dawn-dusk electric field after the turn of the IMF BZ to the south in the equatorward extension of
DA. The formation and/or brightening of SAR arcs in the three events are most likely connected with a fast
penetration of energetic particles of a developing ring current into the outer plasmasphere during the sub-
storm expansion phase or the intensification of quasi-stationary activity as in the third example. The devel-
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