[1] The PC index estimates the polar cap magnetic activity generated by the solar wind and its embedded magnetic field. It shows a high degree of correlation with geophysical disturbance parameters characterizing the state of magnetosphere. After transition to 1-min PC index values, significant differences were revealed between the PCN and PCS indices, derived on the basis of magnetic data from Thule and Vostok stations, respectively. Differences in values of the 1-min PCN and PCS indices may give rise to discrepancy in results of various analyses and to quite erroneous physical conclusions.

We use a comprehensive set of data collected from space-borne instruments and from ground-based facilities to estimate the energy deposition associated with the three major magnetospheric sinks during the event. It is found that averaged over the 2-day period, the total magnetospheriC energy deposition rate is about 400 GW, with 190 GW going into Joule heating rate, 120 GW into ring current injection, and 90 GW into auroral precipitation. By comparison, the average solar wind electromagnetic energy transfer rate as represented by the e parameter is estimated to be 460 GW, and the average available solar wind kinetic power Usw is about 11,000 GW. A good linear correlation is found between the AE index and various ionospheric parameters such as the cross-polar-cap potential drop, hemisphere-integrated Joule heating rate, and hemisphere-integrated auroral precipitation. In the northern hemisphere where the data coverage is extensive, the proportionality factor is 0.06 kV/nT between the potential drop and AE, 0.25 GW/nT between Joule heating rate and AE, and 0.13 GW/nT between auroral precipitation and AE. However, different studies have resulted in different proportionality factors. One should therefore be cautious when using empirical formulas to estimate the ionospheric energy deposition. There is an evident saturation of the cross-polar-cap potential drop for large AE (•1000 nT), but further studies are needed to confirm this.•High Altitude Observatory, NCAR, Boulder, Colorado.

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[1] Pressure variations at 11 Antarctic sites and 7 Arctic sites have been examined and show significant correlations with a daily proxy for the output of the meteorological generators of the global atmospheric circuit. This proxy is derived from vertical electric field measurements made at Vostok on the Antarctic ice plateau. Taken with the finding of proportionate pressure variations correlated with atmospheric circuit changes owing to coupling with the interplanetary electric field, particularly for the Antarctic plateau (magnetic latitude > 83°) region, this provides experimental evidence that a small portion of the surface pressure variations are due to the influence of the global atmospheric circuit. The response to the interplanetary electric field is an example of Sun-weather coupling. To evaluate it, the daily average interplanetary magnetic field (IMF) east-west component (B y ) is used as a proxy for the north-south interplanetary electric field, which produces opposite ionospheric potential changes in the northern and southern polar caps. The correlation with IMF B y for the pressure variations for the Antarctic sites for a solar cycle (1995)(1996)(1997)(1998)(1999)(2000)(2001)(2002)(2003)(2004)(2005) is small (0.9% average covariance for the magnetic latitude > 83°sites) but significant (99.7% confidence level). The Arctic stations show a negative regression between pressure variations and IMF B y , a relationship expected if the linkage process operates by the atmospheric circuit, but it is only found when the interval is restricted to the peak of the sunspot cycle (1999)(2000)(2001)(2002).

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