A. E. Levitin

Electric potential patterns in the northern and southern polar regions parameterized by the interplanetary magnetic field

Electric potential patterns have been obtained from the IZMIRAN electrodynamic model (IZMEM) for the northern and southern polar regions during summer, winter, and equinox. The model is derived from a large quantity of high-latitude ground-based geomagnetic data (above 4- 57 o corrected geomagnetic latitude) at all magnetic local time hours. A linear regression analysis technique has been used to obtain the quantitative response of each magnetic observatory to changes of interplanetary magnetic field (IMF) components. Since no ionospheric conductivity model exists specifically for the southern polar region, the statistical model of Wallis and Budzinski (1981) has been applied in both hemispheres. A cross-polar background potential of x7f35 kV, derived by Reiff et al. (1981), is used to calibrate IZMEMs potential patterns. The models responses to changes in the IMF By and Bcomponents are analyzed to obtain a set of elementary convection patterns in both polar regions for each season of the year. Asymmetry in the potential pattern geometry in both hemispheres can be attributed either to the influence of the northern ionospheric conductivity model which was applied to the southern polar region, or to some natural phenomena. The modeled background cross-polar potential for the condition when Bx7f = By = 0 is found to be x7f37 kV. Average values of the modeled potential drop caused by each nanotesla of the IMF are the following: ~14 kV for southward Bx7f; x7f -4 kV for northward Bx7f; and x7f 4-4.5 kV for By components. The latter is not applicable to the dawn-dusk potential drop; it may be applied across the cusp region only. Nevertheless, a combination of the background and elementary potential patterns in the case studies gives a certain estimation of the cross-polar potential drop, which may be strongly distorted during time of large By. It is concluded that IZMEM provides realistic convection patterns parameterized by the IMF component directions and magnitudes and may be used to provide routine estimates of convection patterns and electric potentials if IMF data are available.

Relationship between the observed and modeled modulation of the dayside ionospheric convection by the IMF By component

The Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation (IZMIRAN) electrodynamic model (IZMEM) provides global patterns of polar ionospheric potential and is parameterized by the interplanetary magnetic field (IMF). Given IMF conditions measured by an upstream satellite, the model yields a good global approximation to the polar ionospheric convection patterns assuming the proper time delay. While the model assumes static patterns and is based upon statistical regression analysis of high-latitude magnetometer data, it can furnish an appropriate global context within which to examine time-varying phenomena. The authors use the IZMEM model to further develop their understanding of the coordinated analysis of Greenland radar, riometer, and magnetometer data on August 2, 1991, which is one of the geospace environment modeling program intervals. The event is characterized by geomagnetic pulsations observed near local magnetic noon, having a 25-min period and poleward phase propagation. A modulation of the intensity and orientation of the convection electric field is observed by the Sondrestrom incoherent scatter radar. Modeled global convection patterns show striking agreement with observations in the area covered by the radar field of view. The authors interpret observed phenomena as a direct ground-based evidence of the IMF B{sub y} component reconnection at themorexa0» dayside magnetopause. 31 refs., 6 figs.«xa0less

Energy regimes in the earth's magnetosphere

РезюмеРaссмоmренa ¶rt;uнaмuкa основных nроцессов нaкоnленuя u ¶rt;uссunaцuu знергuu в мaгнumосфере Землu nрu рaзлuчных уровняхгеомaгнumноŭ возмущенносmu. Полученные резульmamы вычuсленuŭ nре¶rt;сmaвлены в maблuцaх. Анaлuзuруеmся взauмосвязь меж¶rt;у энергеmuческuмu хaрaкmерuсmuкaмu солнечного веmрa u мaгнumосферы Землu. Прuво¶rt;яmся некоmорые зaключенuя о nро¶rt;ольных mокaх в nолярноŭ щanке, об энергuu ¶rt;жоулевоŭ ¶rt;uссunaцuu, об энергuu uнжекцuu в кольцевоŭ mок, об энергuu, вы¶rt;еляемоŭ в верхнеŭ uоносфере, u m. ¶rt;.SummaryThe dynamics of the main processes of energy accumulation and dissipation in the Earths magnetosphere at various geomagnetic disturbance levels is examined. The results of the relevant calculations are tabulated. The relationships between the energy parameters of the solar wind and the Earths magnetosphere are analyzed. Some conclusions concerning the field-aligned currents in polar caps, the Joule dissipation of energy and the energy injection into the ring current, the energy releases in the upper ionosphere, etc., are drawn.