Chelpanov M. A., Zolotukhina N.A. Institute of Solar-Terrestrial Physics, Irkutsk, Russia

1. Subauroral heliosphere-geosphere coupling during November 2004 ionospheric storms: F2-region, North-East Asia Chelpanov M. A., Zolotukhina N.A.Institute of Solar-Terrestrial Physics, Irkutsk, Russia

2. Purposes of the study The main object of our study is disturbances of the F2-layer of the subauroral ionosphere, developed on November 7-11, 2004 in the East Asian sector. We consider two negative phases of the ionosphere storm and find out reasons for differences in the duration of the negative phase.

3. Measurements in the restricted sector 190o to 211o geomagnetic longitude Station geomagnetic coordinates1 Kotel'nyy (KTN) 65.21 195.552 LANL-97A (L7) 63.90 210.883 Chokurdakh (CHD) 62.04 206.714 Tixie (TIK) 61.81 193.495 Zyryanka (ZYK) 57.58 211.026 Zhigansk (ZGN) 56.81 190.707 Yakutsk (YAK) 52.39 196.258 Magadan (MGD) 50.68 210.94

4. Series of the November 2004 superstorms The leading edge of the solar wind irregularities propagated past WIND spacecraft at 02 UT on November 7, and approached the Earth at 02:58 UT

5. Series of the November 2004 superstorms: Kp, SYM-H, AU, AL indices

6. Two negative substorm effects

7. Neutral thermosphere densities Thermosphere mass densities predicted by MSIS model and densities derived from GRACE satellite data for altitude 350 km near noon-midnight meridian.from Burke et al., 2007During the second substorm mass densities even less than these during the first one.

8. Outer conditions: IMF The first difference:the first phase developed at southward IMF, the second one began at northward IMF and 3 hours later the IMF turned to the south.

9. Outer conditions: By, density and speed The second difference: solar wind velocity during the second event was 150 km/s higher than that during the first one.

10. Pc5 geomagnetic pulsations The third difference: the second negative phase was accompanied by intense geomagnetic pulsations of the Pc5 range.

11. Auroral electrojets The negative storm effects in Yakutsk occurred in the north-west electrojet region, southward of unstable currents i. e. in the south-westward reverse convection region

12. Reverse convection region Model calculation (Heelis et al., 2009) reveals that in the north-west electrojet regionelectron density and altitude of the F2 layer decrease.

13. Results Both negative phases occurred in conditions of • the morning-noon magnetosphere contracted to the geostationary orbit radius • negative By component of the IMF • the reverse convection region. Differences in conditions of the second negative storm effect are • the negative phase with prolonged ionosphere effect began at northward Bz component of the IMF • high speed of the solar wind • accompanying by generating of geomagnetic pulsations of the Pc5 band.

14. Conclusions • in both cases one of the reasons for negative phase development was critical frequency and F2 altitude depletion in the strong reverse convection region; • high-latitude reconnection occurring in the north morning magnetosphere at the northward IMF and ULF-waves of the Pc5 band amplified the electromagnetic energy entrance to the subauroral ionosphere; • Amplification of energy entering the ionosphere-thermosphere system has led to the long-lived disturbed composition zone which is supposed to be a reason for the morning-noon negative storm effect.

15. Thank you!