Solar wind influences on atmospheric electricity variables in polar regions

Abstract

The measurement techniques applied in magnetospheric and ionospheric research enable detection of strong, intrinsic effects of solar wind on ionospheric electrical potential distribution and conductivity of the atmosphere. These manifestations of the solar wind interaction with the magnetosphere and ionosphere are especially evident at high latitudes. The possibility of observing there the response of the atmospheric electricity variables to solar wind has been questioned for a long time despite the fact that the atmospheric electric field and current variations at the ground are physically linked with electric potential of the ionosphere and conductivity of the lower atmosphere. The serious doubts were mainly due to the generally accepted opinion that the highly conducting ionosphere is an almost ideal equipotential electric screen that separates the weakly conductive lower atmosphere of the influence from space. This assumption could not be further upheld in view of the new findings. They have been provided for some time by ground‐based atmospheric electric field and current measurements (AEMs) with simultaneous upper atmosphere observations and by corresponding balloon measurements. Recent ground‐based AEMs in polar regions, i.e., in the near‐subauroral, auroral, and polar cap high‐latitude regions, have detected considerable influence of solar wind on the lower‐atmosphere electric variables. However, the use of atmospheric electric observations in studying solar‐terrestrial relations is still limited. The main reason is difficulty in separating various local meteorological effects, anthropogenic effects, and the effects of the global electric current circuit which affect simultaneously the measured quantities. Transmission of the electric signals through the lower atmosphere can also introduce troublesome disturbances. The paper outlines these problems and hints how the difficulties involved might be partly overcome in a feasible way. The needs and possible prospects of the polar AEMs are discussed. At selected favorable conditions, these measurements appear to be able to bring supplementary and complementary data on the temporal ionospheric potential variations over the measuring site and, in the case of suitable network of the AEM stations, also on its spatial variation. They are indispensable to providing a better understanding of current flow in atmospheric global electric current circuit. Some suggestions are given toward an extension of present models of this circuit into a model of geospace global electric current circuit.