Previous investigations have shown that the electrical potential of the Earth's ionosphere is a promising globally integrated indicator of the status of the world climate. The ionospheric potential is inhomogeneous in the polar regions. The knowledge about distribution and variations of ionospheric potential is limited today. The aim of this research project is to develop a ground-based method for the acquisition of information on the ionospheric potential variations following the main ideas of the international global atmospheric electric measurement (GAEM) programme, included as a subprogramme in the solar terrestrial energy programme (STEP).

The method is based on measurement of the atmospheric electrical vertical current simultaneously by several ground-based long-wire antennas located in various sites in auroral region and in mid-latitudes. The ionosphere-induced signals are to be detected on the background of local turbulence-induced variations. Research into the turbulence-induced variations of atmospheric electrical current is therefore included as a part of the project.

Simultaneous measurements with long-wire antennas will be carried out in Kiruna, Nattavaara and Uppsala (Sweden), Sodankyla (Finland) and Borok (Russia). Efforts will be made to bring Hornsund (Spitzbergen), Swider (Poland) and Tartu (Estonia) additionally into the list of measurement stations. The vertical current density will be measured simultaneously and will be recorded independently in each station. Measurement frequency from 0.1 Hz to 1 Hz will be used in various measurement campaigns. Measured time series of a length of several months will be recorded on computer disks. Methods of multidimensional statistical analysis will be used to identify the ionosphere-induced component in the time series. Available from other sources, data of routine ionospheric and magnetometric measurements will be included in the database and will be used simultaneously with vertical current measurements.

The following results will be obtained: a quantitative model of the turbulence-induced variations of the signal of a long-wire antenna and the method for estimation of the level of turbulence-induced variations using micro-meteorological data; database of vertical current time series measured synchronously in several locations in the Aurora region; preliminary quantitative model of the ionospheric potential variations in the aurora region based on the ground level measurements; and estimates of ionospheric effects realised through atmospheric electrical mechanisms in the lower atmosphere.