The atmosphere carries a continuous electric current and , even during fair weather, there is a strong electrostatic electric field, up to 200 volts per meter, close to the ground. This electric current is thought to be due to the accumulated effect of thousands of thunderstorms, mostly in the tropical regions of the Earth. These storms feed a current from the ground up to the ionosphere, a highly conducting layer in the atmosphere which lies above about 70 km altitude. The current spreads out around the globe through this layer and returns to Earth through the atmosphere as the 'fair weather current' outside the thunderstorm areas. Objective: Investigation of the part of the Earths global electrical circuit: fair weather current and its interaction with geomagnetic phenomena, such as, for example, a magnetic substorms. We use the data of the air-earth current measured by a long wire antenna installed in Kiruna/Esrange, Sweden. In July 1999 we have installed a new portable antenna at a distance of about 30 km from the old one. This antenna has a length of nearly 50 m, and we are recording the near ground vertical current with a time resolution of 10 seconds. The data from both instruments will be analysed together - for comparison and possible separation of the meteorological effects.
Observations of the fair weather current using a long wire antenna (100 m long) situated near the top of a hill at Esrange. A second antenna will be placed at a nearby site during 1999 and comparisons are also made with similar measurements from Sodankylä in Finland. It is important to have measurements from several sites in order to separate local (meteorological) variations from true fair-weather global effects. Vertical profiles of atmospheric electric field are also collected in the SKERRIES programme.
Esrange (European sounding rocket launching range)