Physics of auroral phenomena : proceedings of the 36th Annual seminar, Apatity, 26 February – 01 March, 2013 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2013. - 215 с. : ил., табл.

‘Physics o f Auroral Phenomena", Proc. XXXVI Annual Seminar, Apatity, pp. 81 - 84, 2013 © Kola Science Centre, Russian Academy of Science, 2013 Polar Geophysical Institute PRECIPITATION OF PROTONS RELATED TO EMIC WAVES ON THE DAYSIDE A.G. Yahnin and T.A. Yahnina (Polar Geophysical Institute, Apatity, Russia) Abstract. In our previous works we found that some EMIC waves (geomagnetic pulsations Pci and IPDP) relate to localized precipitation of energetic protons (LPEP) equatorward o f the isotropic boundary. Typically, LPEP map onto the equatorial plane at r<7 RE. At the same time, observations of EMIC waves in the magnetosphere showed that most of EMIC wave events are observed well beyond the geosynchronous orbit on the dayside. In this report we describe another type of proton precipitation that can be produced by interaction of EMIC waves and magnetospheric protons. In contrast to LPEP, this precipitation occupies a wide latitudinal range and is observed at relatively high latitudes (but still, like LPEP, equatorward of the isotropy boundary). The relationship between such precipitation of energetic protons and EMIC waves is confirmed on the basis of the case and statistical comparisons. 1. Introduction Several recent studies were devoted to investigation of global characteristics of EMIC waves in the equatorial magnetosphere. Usanova et al. (2012) and Min et al. (2012) used data from the THEMIS mission. In agreement with earlier study by Anderson et al. (1992), they found that probability to observe EMIC waves is generally small within the geosynchronous orbit (< 3%) and increases beyond it. Usanova et al. found the maximal occurrence (some 10%) of waves at noon-dusk sector at L=9 (note that radial coverage in that study was L =3-10). Usanova et al. did not distinguish between H and He bands of EMIC waves. In contrast, Min et al., considered these bands separately. For the H band they found the maximal occurrence (some 20%) at L=10-12 and MLT=5-8 with secondary maximum (10%) at noon-dusk. The maximal occurrence of the He band waves was found in the afternoon (20%) at L=8-12 and the minor maximum (10%) was found at the dawn sector. Keika et al. (2013) used data from the AMPTE/CCE spacecraft at L=3-9, and also examined the occurrence rate for He and H bands separately. They found the maximal occurrence of EMIC waves in the afternoon (25% and <10% for the H and He bands, respectively). Ali above- mentioned authors (see, also Fraser and Nguyen , 2001) noted a reduced occurrence of EMIC waves in the night sector in comparison with dayside. Since EMIC waves scatter resonant ions into the loss cone, the fact that EMIC waves are mostly occur on the dayside should be manifested in the ion precipitation. Using data from the NOAA-12 satellite, Yahnina et al. (2003) selected a specific pattern of proton precipitation related to the EMIC waves seen on the ground as quasi- monochromatic geomagnetic pulsations Pci and intervals of pulsations o f diminishing periods (IPDP). This is localized (<1° in latitude) precipitation of energetic protons (LPEP) within anisotropy zone equatorward of the isotropic proton precipitation region. The localized nature of the precipitation is, likely, related to the fact that wave- particle interaction responsible for Pci and IPDP and LPEP occurs at gradients o f the cold plasma density in the equatorial magnetosphere ( Yahnin et al., 2007, 2009, 2013; Morley et al., 2010; Yuan et al., 2012; Liu et al., 2013). The maximal occurrence rate o f the LPEP was found to be equal to -1% and -2% at dawn and dusk, respectively ( Yahnina et al., 2003). However, due to peculiarities of the orbit, NOAA-12 observations did not cover the 10 < MLT <15 sector. Also, LPEP are typically observed at L<7 ( Yahnina et al., 2000; 2003). Thus, LPEP events can hardly be associated with a major part of EMIC waves on the dayside in the outer magnetosphere. The aim of this paper is to find and describe a proton precipitation pattern that might be associated with the bulk of the EMIC wave events on the dayside. To solve this problem we use the data from low-orbiting satellites of the NOAA POES series. The satellites are equipped with the MEPED instrument, which measures charged particles with the energy £ > 3 0 keV, both within the loss cone and trapped at the satellite altitude (-800 km). In section 2 an example of particle measurements conjugated with a dayside EMIC wave event is shown. Some characteristics o f the revealed proton precipitation pattern including the occurrence distribution in MLT-CGLat coordinates are described in section 3. Section 4 presents the discussion and conclusion. 2. Low-orbit observations of the proton precipitation conjugated with dayside EMIC waves in In the paper by Min et al. (2012), the example of wave observations in the day sector of the outer magnetosphere was presented (their Fig. 1). The waves in frequency range 0.2-0.4 Hz were observed at 01- 04 UT of 31 August 2007 in the distance range of 6-10 RE. Below 7.4 REthese waves were identified as EMIC waves in the He band, and further from the Earth as EMIC waves in the H band. In projection onto the ionosphere the waves were observed within a wide range of CGLat (67°-72°). Fig. 1 shows the trace of the THEMIS A spacecraft for the time of space 81