The Sun, Space Weather and Effects

Sammanfattning: The Sun and the solar magnetic activity is responsible for a variety of effects in space and on the Earth. High energy radiation and charged particles are constantly being emitted from the solar atmosphere interacting with our atmosphere and technological systems in space and on the ground. The research papers included in this thesis cover analysis of solar magnetic activity, solar indices, solar wind data and geomagnetic data. Also included are calculations of induced currents in power grids from geomagnetic disturbances and prediction of the geomagnetic field. The most common solar index, the sunspot number, was studied as a proxy for the total solar irradiance. The solar magnetic activity, in the form of synoptic maps, was analysed on many time scales from about a day up to several years. The data and the analysing tools used in the papers, wavelets and neural networks, are also briefly described. This doctoral thesis is about space weather and solar-terrestrial physics. It is divided into a summary and five research papers. In the summary I present an outline of the solar-terrestrial environment: The Sun, solar magnetic activity, the heliosphere and the solar wind, geomagnetic storms and ground effects. I also briefly summarise each paper. In the second part all five papers are reprinted. Papers A and B compare induced currents in technological systems, both measured and calculated, with geomagnetic disturbances and other solar-terrestrial data. Paper C use an empirical model, based on neural networks, to predict the local ground magnetic field fluctuations from solar wind data. Paper D, studies the relationship between solar indices and the total solar irradiance using wavelet analysis. Finally, paper E includes a multiresolution analysis of solar synoptic magnetic fields.