Solar-Terrestrial Physics Division

Aurora in space
photographed from
a NASA space shuttle

Space Weather

Space Weather is a modern phrase for the conditions in space that are deterimined by the intensity of hard radiation, the magnitude of electric and magnetic fields, the level of electric currents, and other disturbances. Space "storms" often result from flare or coronal mass ejection events at the Sun which greatly intensify the solar wind. With a delay of a few days such disturbances may impact the near Earth environment.
Space weather conditions are extremely important for the behaviour of satellites and space probes. Radiation damage from high energy particles may destroy the solar panels, cause upsets in the onboard computer systems, and may sometimes cause destructive sparking in space instruments. The atmosphere can get heated and expand to cause satellite braking and subsequent re-entering.
Space weather conditions may also affect systems at ground. During geomagnetic storms with brilliant auroras in the polar regions, currents of millions of amps may flow in the upper atmosphere at heights around 100 km. These currents induce secondary electric fields and currents at ground level, for instance, in high-voltage power lines, where they may cause failure in line protection relays and damage to transformers resulting in power outages over large regions. Extended telephone lines and other signal lines may also be disturbed and damaged. Even steel pipe-lines carrying oil and gas from fields in the arctic regions to consumers south of the auroral zone are damaged by the corrosive effects of such Geomagnetically Induced Currents (GIC).
The Solar-Terrestrial Division of DMI conducts observations in the auroral and polar regions of magnetic disturbances and precipitation of high-energy radiation. The division is also active in the Oersted satellite project. These observations are used for monitoring of actual space weather conditions and for research in space weather effects. Data and results are, among others, exchanged via this web site.

Solar Activity and Climate

Space weather may also in the long term affect the Earth's climate. Solar ultra-violet, visible and heat radiation are the primary factors for the Earth's climate, including global average temperatures, and these energy sources appear to be quite constant. However, many scientists have observed corrrelations between the solar magnetic activity, which is reflected in the sunspot frequency, and climate parameters at the Earth. Sunspots has been recorded through several hundreds of years which makes it possible to compare their variable frequency to climate variations to the extent that reliable climatological records exists. One of the most striking comparisons was published by E. Friis-Christensen og K. Lassen, DMI, in "Science" in 1991. In their work they compared the average temperature at the northern hemisphere with the average solar activity defined through the interval between successive sunspot maxima. The more active the sun - the shorter the interval: the solar cycle runs more intense. Their results are displayed in the figure below:

The red curve illustrates the solar activity, which is generally increasing through an interval of 100 years, since the cycle lenght has decreased from around 11.5 years to less than 10 years. Within the same interval the Earth's average temperature as indicated by the blue curve has increased by approximately 0.7 degree C. Even the finer structures in the two curves have similar appearances.
(Reference: Friis-Christensen, E., and K. Lassen, Length of the solar cycle: An indicator of solar activity closely associated with climate, Science, 254, 698-700, 1991).

DMI 19 oktober 1998. PSt