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[en] Complete text of publication follows. During large magnetic storm the geomagnetically induced current has a negative impact on ground conducting technology system. The time derivative of horizontal and northern component of geomagnetic field (dH/dt, dX/dt) is greater than 30nT/min for induced current causing undesirable consequence in power grids. Multiple regression analyses were developed to predict level of geomagnetic disturbance using time derivatives of horizontal geomagnetic field, northern component of time derivatives of geomagnetic field, east and north component of geoelectric field, auroral electrojet and disturbance storm time from 1994- 2007 at low and subauroral latitudes. The statistical test RMSE (Root Mean Square Error) and MBE (Mean Bias Error) were employed to evaluate the accuracy of the geomagnetic disturbance. Different variables have been used to develop different types of models. There are high values of correlation coefficient and coefficient of determination which gives good results and with also low statistical indicator. The equations produced the best correlations at subauroral and low latitude, the best correlation is obtained with low values of RMSE and MBE.
[en] Complete text of publication follows. Recent studies, both from conjugate observations and statistics from one hemisphere have shown that the asymmetry at substorm onset is largely dependent on the orientation of the interplanetary magnetic field. Using conjugate UV imaging from the Polar and IMAGE spacecraft, we show that the rapid changes associated with the substorm expansion phase have significant implications for the interhemispheric asymmetry. Our findings indicate that the interhemispheric asymmetry is imposed by tension forces from the lobes.
[en] Complete text of publication follows. The observations and modeling of an additional layer, called F3 layer, over the equator during the main phases of five super geomagnetic storms are presented. The observations show the occurrence, re-occurrence (in some cases) and quick drift to the topside ionosphere of unusually strong F3 layer during the main phases of all the five super storms. The unusual F3 layers, with large reductions in peak electron density, occurred in the longitudes that were in daytime sector during the main phases of the super storms; IMF Bz was also strongly southward. These observations indicate that the unusual F3 layers are produced by strong daytime eastward prompt penetration electric filed (PPEF) events. The PPEF events are identified in the equatorial electrojet strength in all five cases; the PPEF events are also measured in some cases. By using a measured PPEF event, the SUPIM model qualitatively reproduces the observed F3 layer. The observations and modeling suggest that the sudden appearance of strong F3 layer that quickly drifts to the topside ionosphere can be used as an indicator of daytime eastward PPEF event. The suggestion can be confirmed by a statistical study of the F3 layer during major and supper geomagnetic storms.
[en] Complete text of publication follows. The equatorial ring current (ERC) theory suggested that the global distribution of horizontal geomagnetic field only dependent on the cosine of station's latitude. However, we always observe a larger disturbed H at higher latitude stations than lower ones, implying that the ERC could tilt or/and shift with respect to the equatorial plane during several intense storms. In this paper, we analyze 11 intense magnetic storms from 2000 -2004, and introduce two configurational factors to characterize the topology of storm time ring current. The results show that ERC has occasionally deviated off equatorial plane with both tilt angle δt ∼ 13 ∼ 250 and latitudinal shift δs ∼ 0 ∼ 21.80. The ground disturbed field distribution should be improved as ΔHk = Dst cos(ψk - δ, which agree well with the most geomagnetic observations.
[en] Complete text of publication follows. First discovered by Chung Park in 1973, the plasmasphere within the new plasmaspheric boundary layer during magnetic storms could undergo a noticeable decrease in density, and this depletion could represent a significant fraction of the overall losses from the plasmasphere. Several processes, such as plasma dumping to the ionosphere, have been proposed as the cause of internal plasmaspheric depletion during storm times, but finding the responsible physical mechanism remains an outstanding problem. As an effort to identify the important causes to this complicated phenomenon, this study examines a collection of critical ground and satellite observations, including the mass density inferred from field line resonance sounding, the charge density deduced from whistler traces, ionosonde data, and the RPI observations from the IMAGE satellite. We find that the plasmasphere within the new plasmaspheric boundary layer does not necessarily decrease in all magnetic storms. An enhancement in plasmaspheric density can sometimes be found. The increase or decrease in plasmaspheric density echoes the change in ionospheric content during the storm event. Our results suggest that, during magnetic storms, the related ionospheric storms may play a major role controlling the internal plasmaspheric content.
[en] Complete text of publication follows. Different structures in solar wind are observed depending on the type of solar activity: magnetic clouds (MC), recurrent streams (RS), and regions of their interaction with undisturbed solar wind (Sheath and CIR). Three of these structures, namely, Sheath, CIR, and MC, are the sources of geomagnetic storms. Furthermore, the storms originating from these three sources differ in intensity, recovery phase duration, etc. We have searched for distinctions in the development of substorm bulges occurring during geomagnetic storms connected with the MC, Sheath and CIR. Solar wind parameters were taken from the Wind spacecraft observations and the auroral bulge parameters were obtained by data from the Ultra Violet Imager onboard Polar. We determined the longitudinal and latitudinal dimensions of the auroral bulges, the poleward aurora propagation and the onset latitude of auroral bulge. It is shown that auroral bulges 'geometry' is different for these types of storms. The largest sizes of auroral bulge are found for CIR- and Sheath-storms situations. The latitudinal size of the auroral bulge during MC-storms is smaller, but the longitudinal size is larger. As consequence, the ratio between longitudinal and latitudinal sizes for substorms during MC is also larger. We suggest the this latter feature is explained by different configuration of the near-Earth magnetotail during CIR- and MC-storms.
[en] Complete text of publication follows. The relative importance of diffusion, electric field and neutral wind on equatorial plasma fountain and ionospheric storms during strong daytime eastward electric field events are evaluated using SUPIM and the electric fields obtained from the equatorial electrojet during the super geomagnetic storm of 08 November 2004. The plasma fountain rapidly develops into a super fountain during the strong daytime eastward prompt penetration electric field (PPEF) event. The super fountain becomes strong with less poleward turning of the plasma flux vectors in the presence of an equatorward wind that reduces (or stops) the downward velocity component due to diffusion and raises the ionosphere to high altitudes of reduced chemical loss. The equatorial ionization anomaly (EIA) crests in Nmax and TEC shift rapidly to higher than normal latitudes during the PPEF event. However, the crests be- come stronger than normal only in the presence of an equatorward neutral wind. The results suggest that the presence of an equatorward neutral wind is required to produce strong positive ionospheric storms during daytime eastward PPEF events. The model results are supported by the positive ionospheric storms observed in Ne, Nmax, TEC and airglow. The plasma fountain becomes a reverse plasma fountain during a strong westward electric field event.