Global distribution of ionospheric and field‐aligned currents during substorms as determined from six IMS meridian chains of magnetometers: Initial results

Abstract

As a part of the joint efforts of operating six meridian chains of magnetometers during the IMS, magnetic records from 70 stations are used to deduce patterns of electric fields and currents in high latitudes on March 17, 18, and 19, 1978. First of all this data set is used to examine the fidelity of the AE(12) index by comparing it with the AE(70) index and also the fidelity of the AL(70) index as a measure of the total westward electrojet intensity. The coefficients for the two correlations are found to be more than 0.8. Then the distribution of both ionospheric currents and field‐aligned currents, as well as the electric field, are for the first time determined with a time resolution of 5 min by using an appropriate conductivity distribution model. Although much improvement is still needed for better accuracy, especially in the estimation of ionospheric conductivity, it has now become possible to study the growth and decay of the three‐dimensional current system over the north polar region during individual magnetospheric substorms with sufficient time resolution. Our initial results show that the gross features of the instantaneous distributions of the ionospheric and field‐aligned currents are remarkably similar to the daily average pattern during a very weak activity and at different substorm epochs and that the large‐scale current pattern grows and decays systematically as a whole. There are, however, significant changes in local scales.

A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions

“…The large-scale morphology of ionospheric convection, and its dependence on the prevailing IMF conditions, has been well understood for a number of years, mainly as a result of statistical studies using low-altitude spacecraft (Heppner and Maynard 1987;Rich and Hairston 1994;Weimer 1995) and ground magnetometers (Kamide et al 1982;FriisChristensen et al 1985;Papitashvili et al 1994). Early SuperDARN studies provided a statistical characterization of nightside convection (Ruohoniemi and Greenwald 1995), (see colour table for scale).…”

“…Before the advent of SuperDARN, global studies of high-latitude convection had been largely statistical (Kamide et al 1982;Friis-Christensen et al 1985;Heppner and Maynard 1987;Hairston 1994, Papitashvili et al 1994;Weimer 1995), due to the limited spatial extent of the contributing data sets, with studies of the dynamics of convection being limited to the small (*10 km) or meso-scale (*100 km). SuperDARN allowed the measurement of convection on a more global scale.…”

Auroral Substorms: Search for Processes Causing the Expansion Phase in Terms of the Electric Current Approach

“…4.1. The results are based on magnetometer records from the international six meridian chains of stations (Kamide et al 1982) with the two methods KRM and MNOC. , and compared them with the radial current vectors (red arrow) on the equatorial plane obtained by a satellite (Iijima et al 1990); this result confirms the validity of the analysis of both methods This is also one of the most important products of the analyses based on the electric current approach, although it is only a first approximation Akasofu 2013).…”

“…In order to find such a current distribution over the whole polar ionosphere, six meridian chains of magnetic observatories were set up by an international effort (International Magnetosphere Study); see Kamide et al (1982). The magnetic records were analyzed to obtain magnetic disturbance vectors at each station.…”

Spatial distribution of conductances and currents associated with a north-south auroral form during a multiple-substorm period

“…During and after the International Magnetospheric Study (IMS, 1976±1979), several studies were carried out that combined ground magnetic ®eld data from the arrays set up during this period with ionospheric electric ®eld data measured by coherent scatter radars (e.g., Akasofu et al, 1980;Kamide et al, 1982; see the review of Untiedt and Baumjohann, 1993, for the studies carried out with observations from Scandinavia). Many of these works addressed the spatial conductance, electric ®eld, currents, and FAC distribution associated with auroral forms, such as the westward traveling surge (WTS; e.g., Inhester et al, 1981;Opgenoorth et al, 1983a), the auroral breakup (e.g., Opgenoorth et al, 1980;Baumjohann et al, 1981), or omega bands (e.g., Andre and Baumjohann, 1982;Opgenoorth et al, 1983b).…”