MAGNETOSPHERIC RESPONSE TO COMPLEX INTERPLANETARY DRIVING DURING SOLAR MINIMUM: MULTI-POINT INVESTIGATION R. Koleva, A. Bochev Space and Solar Terrestrial Research Institute, Bulgarian Academy of Sciences, Sofia, Bulgaria

INTERPLANETARY CONDITIONS and GLOBAL CHARACTERISTICS - 22 December at ~ 9:50 an interplanetary shock ahead of ejecta (CME). The shock produced a SC and a storm began to develop. ( - the sheath region - prolonged intervals of IMF Bz south, north and again south; SW rampressure with spikes of at least 20 nPa and IMF of at least 35 nT, and induced E fields of more than 10 mV/m. Two overlaid substorms developed with AL reaching down to –1123 nT and Dst reached of –75 nT. - cloud - the next about 5 hours - IMF Bz turned north, though another substorm took place, the magnetosphere began slowly to recover. - ~ 19:20 UT another interplanetary shock stroke the magnetosphere. It was caused by ejecta, possibly a magnetic cloud [1]. During the next ~ 18 hours IMF Bz stayed south, in the first 8 hours IMF sustained 25 nT or more. Many substorms developed, the largest with AL=-1400 nT. A second storm took place, with minimum Dst=-108 nT, but a prolonged – more than 13 hour interval of Dst < -90 nT November WIND, being at GSM =[183.47, 6.8, 31.15], at 12:50 – 13:05 registered interplanetary sector boundary crossings, pressure change and other variations, the interval showing the possible signature of a magnetic hole. By/Bz By/Bx OMNI 1 AU IP Data

AIM: Study the reaction of the magnetosphere during this complex event using data from both satellites of the INTERBALL pair - the high apogee INTERBALL-Tail and the lower apogee INTERBALL-Auroral; Compare the observations with the results from Tsyganenko'96 and Tsyganenko'2005 storm models.

Position of the satellites INTERBALL - Tail position on model field lines INTERBALL - Auroral footprints Models: Ts’05 and Ts’96

REACTION OF THE OUTER MAGNETOSPHERE: INTERBALL-1 (Tail)

REACTION OF THE INNER MAGNETOSPHERE: INTERBALL-2 (Auroral)

Field aligned currents  auroral arcs

COMPARISON of MEASURED MAGNETIC FIELD With TSyganenko’96 and Tsyganenko’05 MODELS

SUMMARY We have examined the behavior of the high-latitude magnetosphere during the intense geomagnetic storm November 1997, in the minimum of the 23-th solar cycle, using data from the pair of INTERBALL satellites. The storm had complicated interplanetary driver as the action of two ejecta overlaid. During the period of the sheath region after the first interplanetary shock: At the high apogee IB-1 typical loading was registered. No unusual behavior of the magnetotail plasma was observed. At the low apogee IB-2 (footprints at auroral latitudes) the shock triggered slight disturbances in the magnetic field though the auroral activity was very high After the second interplanetary shock: d At the high apogee IB-1 during Dst minimum a thick mantle was observed; Mantle plasma was accompanied by highly anisotropic SW polar rain electrons; during the recovery phase - highly anisotropic SW electrons + accelerated nearer the Earth tailward flowing electrons. At the low apogee IB-2 during Dst minimum and especially in the first hours of the recovery phase intense FAC developed. Comparison of observations with Ts’96 and Ts’05 models showed that Ts’05 is an adequate approximation of the field in the auroral magnetosphere during disturbances with direct interplanetary driving. For disturbances due to stored in the tail energy both models fail. At higher altitudes the By component is not adequately modeled.

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