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 ± 57° 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 ∼35 kV, derived by Reiff et al. (1981), is used to calibrate IZMEM's potential patterns. The model's responses to changes in the IMF By and Bz components 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 Bz = By = 0 is found to be ∼37 kV. Average values of the modeled potential drop caused by each nanotesla of the IMF are the following: ∼14 kV for southward Bz; ∼ −4 kV for northward Bz; and ∼ ±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.

1] A large database of anomalies, registered by 220 satellites in different orbits over the period 1971--1994, has been compiled. For the first time, data of 49 Russian Kosmos satellites have been included in a statistical analysis. The database also contains a large set of daily and hourly space weather parameters. A series of statistical analyses made it possible to quantify, for different satellite orbits, space weather conditions in the days characterized by anomaly occurrences. In particular, very intense fluxes (>1000 particles cm À2 s À1 sr À1 (pfu) at energy >10 MeV) of solar protons are linked to anomalies registered by satellites in high-altitude (>15,000 km) near-polar (inclination >55°) orbits typical for navigation satellites such as those used in the GPS network, NAVSTAR, etc. (the rate of anomalies increases by a factor of $20) and to a much smaller extent to anomalies in geostationary orbits (the rate increases by a factor of $4). The efficiency in producing anomalies is found to be negligible for proton fluences <100 pfu at energies >10 MeV. Elevated fluxes of energetic (>2 MeV) electrons >10 8 cm À2 d À1 sr À1 are observed by GOES on days with satellite anomalies occurring at geostationary (GOES, SCATHA, METEOSAT, MARECS A, etc.) and low-altitude (<1500 km) near-polar (>55°) orbits (Kosmos, SAMPEX, etc.). These elevated fluxes are not observed on days of anomalies registered in high-altitude near-polar orbits. Direct and indirect connections between anomaly occurrence and geomagnetic perturbations are also discussed. Citation: Iucci, N., et al. (2005), Space weather conditions and spacecraft anomalies in different orbits, Space Weather, 3, S01001,

Geomagnetic field variations and electromagnetic waves of different frequencies are ever present in the Earth's environment in which the Earth's fauna and flora have evolved and live. These waves are a very useful tool for studying and exploring the physics of plasma processes occurring in the magnetosphere and ionosphere. Here we present ground-based observations of natural electromagnetic emissions of magnetospheric origin at very low frequency (VLF, 3-30 kHz), which are neither heard nor seen in their spectrograms because they are hidden by strong impulsive signals (sferics) originating in lightning discharges. After filtering out the sferics, peculiar emissions are revealed in these digital recordings, made in Northern Finland, at unusually high frequencies in the VLF band. These recently revealed emissions, which are observed for several hours almost every day in winter, contain short (∼1-3 min) burst-like structures at frequencies above 4-6 kHz, even up to 15 kHz; fine structure on the 1 s time scale is also prevalent. It seems that these whistler mode emissions are generated deep inside the magnetosphere, but the detailed nature, generation region and propagation behaviour of these newly discovered high latitude VLF emissions remain unknown; however, further research on them may shed new light on wave-particle interactions occurring in the Earth's radiation belts.

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