Physics of auroral phenomena : proceedings of the 37th Annual seminar, Apatity, 25 - 28 February, 2014 / [ed. board: A. G. Yahnin, N. V. Semenova]. - Апатиты : Изд-во Кольского научного центра РАН, 2014. - 125 с. : ил., табл.

L.L. Lazutin e 1.7 M e V 23.07.2004 03-09 U T Figure 2. Asymmetry of the radial profiles: low latitude shifts starts earlier and deeply in the evening sector (broken lines) as compared with the morning ones. L' is an approximation for the evening profiles (see text). 2. Real drift L-value. By the upper abscissa axis at Fig. 1 a Mcllwain L-value for an undisturbed magnetosphere was taken. During magnetic storms particle magnetic drift trajectory does not corresponds to such L values. For a disturbed part of the magnetosphere corrected L-value must be calculated based on a current local magnetic field configuration. Therefore if one wants to investigate particle magnetic drift, L-value calculated for the evening sector must differs from the morning one. The evening profile must be shifted to the lower latitudes and possibly for the explanation of observed effects one mast just use different L scales, as shown schematically by the bottom axis at Fig. 1. We did not know real magnetic field configuration during main phase of magnetic storms. There are models with down-dusk asymmetry, such as Tsyganenko [2002], but inevitable deviation from the real one will not allow us to calculate improved L and to found, whether this effect totally or only partially explain observed down-dusk radiation belt asymmetry. 3. Adiabatic transformation. There is another possible explanation of down-dusk effect by simple adiabatic transformation: at evening sector electrons decrease their energy and changes position because of magnetic field decrease while at the midnight-day side it recovers initial position and energy. Adiabatic effect was described times ago by Mcllwain [1966] and receive the name "Dst-effect" [Kim and Chan, 1997; Kim et al., 2010; Lemaire et al., 2013] consider this effect as a main factor of radiation belt transformation. Adiabatic effect is based on the condition of conservation of adiabatic invariants. Conservation of the third invariant means that if the magnetic flux inside particle magnetic drift orbit decreased, outward shift of the orbit must follow. Then because of the increase of the length of the magnetic field line mirror points became shifted upward as demands second invariant conservation. And finally conservation of the first adiabatic invariant leads to decrease of particle energy. All that will cause severe decrease o f the particle intensities registered by low-altitude satellites. During magnetic field recovery adiabatic recovery of the particle energy and position will return situation to the prestorm condition. Figure 3. Difference of the particle shifts at low and high altitudes. During magnetic field decrease field lines located on some points at low altitude change equatorial position from Al to A2 and B1 to B2. Adiabatic cooling results by the particle shift from Al to B2, with increasing distance from the Earth at the magnetic equator plane and decreasing latitude at the field line footprints [Lazutin, 2012]. The same physics may be attributed to single magnetic drift orbit of an electron if magnetic field in the evening sector is decreasing while at the midnight-day side it increased for example due to the enhance solar wind pressure or substorm hyperdipilarization effect [Lazutin, 2014]. In such a case electron energy and position will be changing as shown schematically by Fig. 3 for two drift orbits. 2. Discussion and conclusion Because essential evening side particle loses as a source of the down-dusk asymmetry must be excluded, observed profile differences may be explained by the combination of two other effects discussed above. First effect must decrease asymmetry by the use of a real L' calculated for a magnetic fields distorted at the evening side instead of L- 27