Physics of auroral phenomena : proceedings of the 35th Annual seminar, Apatity, 28 Februaru – 02 March, 2012 / [ed. board: A. G. Yahnin, A. A. Mochalov]. - Апатиты : Издательство Кольского научного центра РАН, 2012. - 187 с. : ил., табл.

A.G. Yahnin etal. during the date given as input and 24 hours before are taken into account. It has been demonstrated that this plasmapause model reproduces the plasmapause observed from the IMAGE spacecraft rather well (e.g., Pierrard and Cabrera, 2005; Pierrard and Stegen, 2008). 2. Results of the sub-oval proton aurora spot mapping The set of sub-oval proton aurora spot events for this study has been selected after a search through the IMAGE data for 2000-2005. In all, 17 events were selected. Most of them have been described by Frey et al. (2004) and Yahnin et al. (2007, 2008). The list of the events is given in Table 1. The entries in the Table are, respectively, the date when the proton aurora spot was observed, the time (in UT) selected for mapping, MLT of the proton aurora spot at this time, the latitudinal extension of the spot (AMLatsp), the radial extension of the spot projection (ALsp), the location of plasmapause (Lpp) and, finally, the distance between the center of the spot projection and the modeled plasmapause (Lsp -Lpp). No special criteria for the selection of the moment when the mapping was performed were applied except the spot was well discerned. Since the spot stays approximately at the same latitude and drifts eastward with the co-rotation speed (Frey et al., 2004), mapping at other moments does not significantly change mutual locations of the spot projection and the plasmapause. Table 1. Mutual location of the proton aurora spots and plasmapause. Date yyyymmdd UT hhmmss MLT hour AMLatsp О ALsp R e Lpp R e Lsp-Lpp R e 1 20000827 040013 10.3 67.5-68.0 6 .8-7.2 4.8 2.20 2 20000920 115257 10.8 56.5-58.5 3.3-3.7 3.8 -0.30 3 20010228 070115 09.3 65.0-68.0 5.6-12 4.8 1.60 4 20010728 190037 11.4 67.0-69.0 6.6-7.8 4.9 2.30 5 20011126 080653 04.3 55.0-56.5 3.0-3.3 4.3 -1.15 6 20020803 192733 10.0 60.0-62.0 4.0-4.5 4.2 0.05 7 20020906 015715 10.8 62.0-64.0 4.5-5.2 4.4 0.45 8 20030625 130035 15.3 60.5-62.5 4.1-4.7 4.0 0.40 9 20030714 132622 13.0 59.0-62.0 3.8-4.5 4.5 -0.35 10 20030717 122852 14.0 57.0-60.0 3.4-4.0 3.3 0.40 11 20040730 234429 03.6 58.0-60.0 3.6-4.0 3.9 - 0.10 12 20040902 070201 10.8 59.0-62.0 3.8-4.5 4.3 -0.15 13 20041121 012909 02.0 56.0-58.0 3.2-3 .6 4.2 -0.80 14 20050210 153137 17.8 60.0-62.0 4.0-4.5 4.0 0.25 15 20050509 135524 13.2 56.5-58.5 3.3-3.7 4.0 -0.50 16 20050531 102913 11.2 58.0-60.0 3.6-4.0 4.1 -0.30 17 20050917 232610 03.2 56.0-58.0 3.2-3.6 4.0 -0.60 To perform the mapping one needs a magnetic field model. It seems to be reasonable to use the same magnetic field model as for the calculation of the plasmapause location. The model М2 gives the magnetic field intensity in the equatorial plane. This model includes the noon-midnight asymmetry of the magnetic field, but at distances from the Earth up to 5 it only insignificantly differs from the azimuthally symmetric dipole field. Most of the proton aurora spot events listed in Table 1 were observed at magnetic latitude MLat <63.5, which corresponds to L < 5. Thus, for mapping of these spots the dipole approximation comes true. For three of the events at higher latitudes, the mapping with the dipole magnetic field will somehow overestimate the distance of the spot projection from the Earth. In Figure 1 four examples of the mapping are presented. Before the event of 2 September 2004 the geomagnetic activity was low for a long time, in contrast to the event of 17 July 2003 when the activity was variable. This leads to different forms of the modeled plasmapause (black dots). Nevertheless, in both this cases the proton aurora spot (filled circle) maps onto the vicinity of the plasmapause. Conditions for the event of 28 February 2001 are characterized by modest geomagnetic disturbances during the preceding day and geomagnetic calmness just before the event. This associates with the expansion of the plasmapause. The spot maps even further from the Earth, and the distance between spot projection and plasmapause is ~1.5 Rj. On 26 November 2001 and preceding days the geomagnetic activity was variable. In this event, the center of the spot maps at distance ~1 Re inside the modeled plasmapause. Mapping of this proton aurora spot relatively to the plasmasphere observed with IMAGE EUV has been done by Frey et al. (2004). The outer boundary of the cold plasma revealed from the EUV image is in a reasonable agreement with the modeled plasmapause (see, Fig. 5 by Frey et al.). At the same time, a gradient of cold plasma inside the plasmasphere at distance of -3-3.5 Re from the Earth is also clearly recognized. The projection of the proton aurora spot coincides with this gradient. Such gradients, however, cannot be reproduced with the plasmapause location model used in our study. Eleven of seventeen proton aurora spots listed in Table 1 50