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.

Т. V. Kozelova, В. V. Kozelov Fig. 5. Schema of magnetic field lines and current locations relative to spacecraft positions. When the djw was at site '1' (overhead of THC at -21:02 UT), the magnetic field line stretching was observed both at the THA and THC. The plasma sheet thinning result to the drop of the particle fluxes observed at THC. The appearance the j E at site '2' (earthward of spacecrafts at -21:09 UT) results to the increase of stretching more appreciable at THA. The equatorial crossing point of the field line threading the THA approached the site '3', where subsequent CD occurs at 21:10 UT. Just in this time the THA observed the energetic particle injection. The THC observed the particle injection later, at -21:15 UT, when the field line threading the THC approached to the CD region at site '4'. Thus, the spacecrafts locates far from the neutral sheet observe local dipolarization and energetic particle injection when the CD region locates tailward the spacecrafts. However the only small increases of low energy particle fluxes and the weak variations of magnetic field occur when the CD region locates Earthward the spacecrafts. This signature of particles and fields variations is not what one would expect if the disruption region were a neutral line. Another point (matter) concerns the conditions before the substorm explosive phase. We observed two states. First state - Stage o f development with low-frequency pulsations - observed five minutes before the substorm onset, when the increase of the djw was at 8.5-10.5 RE. Maynard et al [1996] observed similar stage before sustorm onset at CRRES at 5-6.6 RE. However we found a new signature, i.e. the appearance of earliest localized eastward current y'E stealed into the range of this increasing djw at - 10 RE. This may mean transition from a quasi-steady to more unstable state o f the plasma sheet. Second state - Slow 'dipolarization' - observed four minutes before Tnp, when the changes of В and E fields have no explosive character and associated with the local thickening (along the Z axis) of the plasma sheet at 10.5 - 11 RE. 6 Conclusion We found that 1) the magnetic field and particle flux changes depend critically on the position of the observing spacecraft relative to the CD region, 2) the substorm current disruption develops discretely by creating the new localized CD region outside previous activity (tailward or Earthward in accordance with large-scale substorm phase), and 3) the dynamics of the CD region corresponds to the subsequent development of the ground activity in a given sector. The spacecrafts, located earthward the CD region, observe the local dipolarization and the energetic particle injection which displaces Earthward with the velocity about 340 km/s. However the only small increases of low energy particle fluxes and the weak variations of magnetic field occurs when the CD region locates Earthward the spacecraft. Acknowledgements. Authors thank the CDAWEB for FGM data at THEMIS spacecraft, and Finnish Meteorological Institute for data of IMAGE magnetometer network. The work is supported by the Programme № VI. 15 of the Division of Physical Sciences of RAS “Plasma Processes in Solar System”. References Moore Т. E., Amoldy R.L., Feynman J., and Hardy D. A. Propagating substorm injection fronts. - J. Geophys. Res., V. 86, NO. A8, P. 6713- 6726, 1981. Russell C.T., and McPherron R.L., The magnetotail and substorms, Space Sci. Rev., 15, 205, 1973 Козелова T.B., Лазутин Л.Л., Козелов Б.В. Электрические поля во время суббури по данным спутника CRRES, Геомагнетизм и аэрономия.Т. 41,№ l.c.39-49, 2001 Kozelova T.V.,Kozelov B.V., Lazutin L.L. et al., Changes in the magnetospheric cross-field current during substorm expansion phase as observed by CRRES. Substorm-4.p.393-396, 1998 Lopez et al., Onthe relationship between the energetic particle flux morphology and the change in the magnetic field magnitude during substorms. J. Geophys. Res., V. 94, NO. A12, P. 17105-17119, 1989. Maynard N.C. et al., Dynamics of the inner magnetosphere near times of substorm onsets. J. Geophys. Res., V. 101, NO. A4, P. 7705- 7736, 1996. Jacquey et al., Location and propagating of the magnetotail current disruption durind substorm expansion: analysis and simulation of an ISEE multionset event. Geophys. Res.Lett., 18,389, 1991. Lui A.T.Y. et al., A case study of magnetotail current sheet disruption and diversion . Geophys. Res.Lett., 15,721,1988. 16