Physics of auroral phenomena : proceedings of the 34th Annual seminar, Apatity, 01 - 04 March, 2011 / [ed.: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2011. - 231 с. : ил.

Trans-polar propagation ofPil wave burst as observed by an Antarctic array during the Themis 2007 /03/23 substorm data from an array of magnetometers in Antarctica. Though it is commonly believed that Pil activity is limited in both local time and latitude [Posch et al., 2005], we will show that Pil bursts observed during this event could be detected at much larger distances than had been expected. activation has leaped westward, so MCQ happened to be just beneath this auroral activation. Fig.l. Map o f search-coil magnetometers in Antarctica. The open diamond denotes the geomagnetic projection o f the Themis-B satellite location at 1100 UT. Search-coil magnetometer array The locations of the Antarctic search-coil magnetometers used in this study are shown in Fig. 1. The array includes US observatories South Pole (SPA); McMurdo (MCM); US AGO stations PI, P2, P3, and P5; Australian stations Casey (CSY), Davis (DVS), and Mawson (MAW); Italian stations Terra Nova Bay (TNB) and Dome С (DMC); and UK station Hailey (HBA). The Antarctic array is augmented by a conjugate station Poker Flat in Alaska (POK) and Macquarie Island (MCQ) in the Southern Pacific. The recording cadence at all stations is 0.5 sec. The substorm event of March 23, 2007 The substorm on March 23, 2007 (day 082) has multiple onsets: at -1110 UT, ~1115 UT, and most intensely at -1120 UT, each accompanied by Pi2 burst. Fig. 1 also shows the geomagnetic projection (according to the T- 96 model) of the Themis-B satellite at 1100 UT on this day. Themis constellation is in the evening sector: three near-by spacecraft A, B, and D are at X—6.9 RE, Y-9.2 Re, Z—0.5 Re. The ionospheric projection of central probe В is -15° eastward from MCQ (Fig. 1). However, a thorough examination of this event showed that in fact the geomagnetic field in this event was substantially twisted, so the actual ionospheric projection should be shifted more to MCQ [Keiling et al., 2008]. Plots of UVI images from Polar spacecraft with superposed location of Antarctic stations show that the first auroral activation occurred -15° eastward from MCQ at -1110 UT. Another, more intense activation occurred at -1120 UT (Fig. 2). The center of this YKAR: 2007 DAY: 0П2 I'olar: 3302, 11:20:10. LU1IL Th-CIBJ WAN(65 11 CHD (64 7*J CAN (-45.9я) MCQ (-64.5-I Fig. 3. Spatially-integrated UV intensity from Polar, Themis-C magnetogram (Bx-component) and magnetograms (H-components) of flux-gate magnetometers in Northern and Southern hemispheres. At nearly-conjugate stations MCQ and POK the emission in the band 0.1-0.5 Hz sharply increased nearly simultaneously during the moment of first activation (Fig. 5). However, the intensification of emission was much stronger during the final auroral activation, when MCQ was covered by the intensified auroral bulge. Most probably, the source of the Pil burst was located in the epicenter of the auroral activation. Thus, a comparison of two subsequent intensifications shows that the Pil power drops off rapidly away from the source. Though the auroral activation starts at -1110 UT, as evident from the variations of spatially-integrated UV intensity, the Pi2 signatures can be evidently seen on the ground during the main activation at -1120 UT (Fig. 3). The dynamic spectra (sonograms) from the Antarctica search-coil array reveal the rapid enhancement of Pil power during each of the substorm onsets (at -1110 UT and -1120 UT). Fig. 5 shows that a very intense Pil burst was observed at the station nearest to the substorm epicenter MCQ. However, rather distinct Pil bursts can be seen at distant stations in the polar cap, at TNB, MCM, P5, and even at PI and CSY (Fig. 4). The Fig. 2. UVI images (LBHL filter) o f auroral activations at 11:20:16 UT from Polar mapped onto the Antarctic stations. ZYK (59.6") PTK(46.3*J EWA (-227") 87