1. CR variation during the extreme events in November 2004 Belov (a), E. Eroshenko(a), G. Mariatos ©, H. Mavromichalaki ©, V.Yanke (a) (a) IZMIRAN), 142190, Troitsk, Moscow region, Russia (b) Physikalisches Institut, University of Bern, Sidlerstrasse 5, CH-3012 Bern, Switzerland

2. Figure. Variation of the parameters of interplanetary space, CR, and geomagnetic activity during the disturbed period on November 2004 -CMEs occurred almost every day (from AR10696); -2-3 disturbances were permanently present and produced shocks ; -Five SSC followed by an abrupt increase in the SW velocity ( 700-800 km/s) and in the IMF (up to 40-45 nT); -the Dst index fell down to - 373 and -289 nT, and Kp reached 8 and 9; -during ~12 hours on 8.11.04 a CR density increase was observed in the FE minimum Such a peak is usually attributed to the geomagnetic effect in CR, but in this case the enhancement of CR density may be a result of the galactic CR modulation by large-scale structures in the interplanetary space.

3. Characteristic features of the event in November 2004 As a consequence of the interaction of different solar wind streams a compressed region was created, with higher CR density and rather complicated structure, which manifested itself in the sharp, short duration changes in the CR anisotropy (Fig. 2). A somewhat similar effect in the time profiles of NM data during the 1991 March 24 FE has been investigated by Hofer and Flückiger [10]. They attributed the effect to a large- scale interplanetary disturbance passing the Earth, possibly a magnetic cloud. In this event the effects of both interplanetary and geomagnetic origin were present simultaneously.

4. The cutoff rigidity variations dRc at different stations were calculated for both events for each hour by the method described in [5, 7]. Fig. 4a. Cut off rigidity variations dRc for the hours of weak and strong disturbed magnetosphere versus Rc [11] in November 2004, obtained by the experimental (points) and model (triangles) calculations. Fig. 4b. Cut off rigidity variations dRc in the maximum of magnetic storm on November 2004 versus Rc referring to the quiescent magnetosphere [11].

5. SUMMARY Solar activity burs in November 2004 led again to significant sporadic CR variations; Permanent releases of the solar substation from the AR10696 followed by shocks, caused significant short time variations in the galactic CR; During the most significant FEs on 7 and 9 November (amplitudes 7.3% and 8.1%) the CR anisotropy reveald sharp and fast changes by the amplitude and direction that is result of complicated quickly varying structures in the interplanetary space; Maximum changes of the cut off rigidity variations (dRc) evaluated for different stations (~ 40) was as much as 0.7GV and occurred at the latitudes corresponded to the Rc=5-6 GV; In a whole, by the level of perturbation, by the number and magnitude effects in CR the situation in November 2004 remains rather disturbed fot the period in a descending phase close to minimum of the solar activity cycle.

6. List of the posters Ground level enhancement of the solar CR in January 20, 2005 SW8; Forecasting and epignose of Galactic Cosmic Ray Variations based on Solar Activity Data (SW10, A.Belov, R. Gushchina, V. Obridko, B. Shelting, V. Yanke; Estimates of long time detector stability of the worldwide Neutron Monitor Network (M25, A.Belov, R. Gushchina, E. Eroshenko, E. Klepach, V. Yanke)