Physics of auroral phenomena : proceedings of the 33rd Annual seminar, Apatity, 02 - 05 March, 2010 / [ed.: A.G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 206 с. : ил.

“Physics o f Auroral Phenomena", Proc. XXXIIIAnnual Seminar, Apatity, pp. 49 - 52, 2011 © Kola Science Centre, Russian Academy of Science, 2011 Polar Geophysical Institute MORNING - EVENING ASYMMETRY OF AURORAL PRECIPITATION DURING MAGNETIC STORMS O.I. Yagodkina, V.G. Vorobjev, I.V. Despirak (Polar Geophysical Institute, RAS, Apatity, Murmansk region, 184200, Russia) Abstract. Dynamics of the electron precipitation boundaries during magnetic storms on 10-11 January, 1997, 21- 22 October, 2001 and 15-16 July, 2000 were investigated. The magnetic storms with a minimum in Dst o f -80 nT, - 200 nT and -300 nT, respectively were driven by interplanetary magnetic clouds. The locations of auroral precipitation boundaries from DMSP F10-15 spacecraft observations were compared to those obtained by means of empirical model ( http://pgia-webapps-www/apm/) . In this model the locations of different auroral precipitation regions depend on geomagnetic activity level expressed by the AL- and Dst indices. It is shown a good agreement between observed and calculated data in different MLT sectors that allowed using the model to examine the dynamics of auroral precipitation and creating the global pattern of precipitation. The significant latitudinal displacements of the diffuse auroral zone (DAZ) and the auroral oval precipitation region (AOP) along with the increase of magnetic activity were observed. During the magnetic storms the width o f the DAZ precipitation in the evening sector (18-21 MLT) does not change significantly while the width of these precipitation in the morning sectors (03-06, 06-09 MLT) increase up to -5° of latitude. The AOP region displays the opposite pattern: weaker widening o f the precipitation in the morning sector than in the evening. In the evening sector about 10° expansion of the structured precipitation is observed. Differences in dawn-dusk widening (i.e., asymmetry) of the DAZ and AOP zones during magnetic storms are demonstrated. Introduction There are several empirical models o f the auroral precipitation depending on geomagnetic activity level (McDiarmid et al., 1975, Spiro et al., 1982; Hardy et al., 1985). These models give the averaged precipitation features in fixed intervals of CGL and MLT. However the position of the region of the different precipitation types varies depending on magnetic activity level and MLT, so that averaging of different precipitation types with different and unknown rate of occurrence takes place. This defect is corrected in the models of Sotirelis and Newell (2000), based on data from 12 years and the eight DMSP satellites. However for selection of data according to the magnetic activity level authors used the latitudinal position of the ion isotropy boundary (b2i), which location was divided into several latitude intervals. Such model is difficult to use in practical purpose since the magnetic activity level is traditionally defined by the value of the AE (AL) and Dst indices. Thus, the existing auroral precipitation models obtained from satellite observations have a greater space-temporary resolution in contrast with our model, but they use as measures of magnetic activity either 3-hour Kp index, or 1-hour AE index. For practical purpose these models are rather difficult to use since they can give only rough estimation of the situations. It is impossible to use these models for more detailed studies, in particular, for study o f the auroral precipitation during storms and substorms. The used here model ( http://pgia-webapps-www/apm/) allows to construct the planetary distribution (geomagnetic latitude - local geomagnetic time) of different types of auroral precipitation depending on the level of geomagnetic activity determined by AL and Dst indexes. The following classification o f the regions of electron penetrations suggested by Starkov et al. (2003) was used in our paper: DAZ (diffuse auroral zone) is the region of diffuse precipitation, located equatorward an auroral oval and spatially coincided with a zone o f diffuse aurorae. This is the zone o f hard electron precipitation formed by the electrons injected into the near-Earth region on the night side and then drifted around the Earth. The typical energy of electrons here exceeds 1 keV. AOP (auroral oval precipitation) is the region of structured precipitation, which equatorward boundary spatially coincides with the equatorial border of the oval of discrete auroral forms. SDP (soft diffuse precipitation) is the region of soft diffuse precipitation poleward o f the AOP region. Aim of this study is the investigation of the electron precipitation boundaries and the creation of planetary pattern o f auroral precipitation during magnetic storms driven by the magnetic clouds. Data used To investigate the planetary distribution o f auroral precipitation during the magnetic storms with a minimum in Dst - 80 nT on 10 January, 1997, - 200 nT on 21-22 October, 2001 and - 300 nT on 15-16 July, 2000 the DMSP F10-F15 observation data (OMNIWeb, http://nssdc.gsfc.noaa.gov) , the AL- and Dst- indices (http://swdcdb.kugi.kvoto- u.ac.ip) . and the empirical model ('http://pgia-webapos-www/apm/'l (Vorobjev and Yagodkina, 2005; Vorobjev and Yagodkina, 2007) were used. The solar wind and interplanetary magnetic field parameters were taken for the WIND satellite (http://cdaweb.gsfc.nasa.gov/cdaweb/istp public/L 49