The Solar-Terrestrial Physics

At DMI the Solar-Terrestrial Physics  group is concerned with research into the relation between solar activity and phenomena in the space around Earth (often referred to as "geospace"). "Solar activity" comprises a range of events evolving from the Sun and the solar corona which can be recurrent or transient but which are unsteady. Solar activity includes flares, coronal mass ejections, radio bursts, variations of the solar wind and the embedded magnetic field, variations of solar radio flux, to name but a few, but it excludes steady (or quasi-steady) solar irradiance. "Geospace" is the upper atmosphere and magnetosphere around the Earth including magnetospheric boundary regions. Research in the Division is driven by geophysical observations  which form the basis of the work performed here.

The external magnetic field, particularly in polar regions, constitutes a main topic of research of the Division. The external magnetic field has its source in electric currents flowing in the upper atmosphere and the magnetosphere (see the magnetic field of the Earth). Observing the external magnetic field can thus be considered a diagnostic method to probe the upper atmosphere, its conditions and dynamics. Magnetic field measurements are supplemented by other ground-based methods such as riometer recordings of cosmic noise absorption as a result of varying ionospheric conditions, and by space borne observations.  

The Ørsted satellite project  with its magnetometers, particle spectrometers and GPS receiver has opened a new and important field of research of the Division.

Research in solar-terrestrial physics serves to support laying foundations for the understanding and potential application of various physical processes in the upper atmosphere.

• Energy from solar activity which reaches geospace is to a large extent dissipated in the polar ionosphere through a range of different processes. Effects on the entire atmosphere are possible.
• Dynamical connections between the upper and the lower atmosphere are widely discussed but conclusions have not yet been reached. The state and dynamics of the upper atmosphere may have substantial influence on the dynamics of the lower atmosphere including the troposphere.
• The state of the ionospheric plasma has significant impact on the propagation of radio waves including those transmitted from ground and from the GPS and future Galileo navigation satellites. The quality of GPS-derived results depends thus on the quality of ionospheric models.
• Violent solar events can lead to storms in geospace and may have adverse effects on a range of technical systems (see Space Weather and Aurora).

The Division is headed by PhD Georg Bergeton Larsen and comprises scientific, engineering, technical and clerical staff. Over the last five years division members authored and co-authored almost 100 publications in international refereed journals and monographs.

Oktober 2007