Monitoring of space weather effects by riometers in Northern Fenno-Scandia

Thomas Ulich, Pekka Verronen*, Jyrki Manninen, Jorma Kangas, and Esa Turunen

Sodankylä Geophysical Observatory, FIN-99600 Sodankylä, Finland
*Finnish Meteorological Institute, Helsinki, Finland


For more than two solar cycles, since the mid-1960s, the Sodankylä Geophysical Observatory, Finland, has carried out continuous measurements of cosmic radio noise by riometers in Finland and Northern Scandinavia. Today the network of riometers covers L-values from 3.7 to 13.2 between 62°N and 77°N in a longitudinal chain. The riometer observations are especially suitable for monitoring the effects of solar proton events (SPE), as well as the effects of high energy auroral electron precipitation in the mesosphere and lower thermosphere. Supported by the large amount of special research instruments and instrument networks in the European Arctic, such as the EISCAT incoherent scatter radars in Tromsø, Kiruna, Sodankylä and on Svalbard, the IRIS imaging riometer in Kilpisjärvi (University of Lancaster), the IMAGE magnetometer network hosted by the Finnish Meteorological Institute (FMI), the pulsation magnetometer network and the neutron monitor of the Sodankylä Geophysical Observatory as well as the regular stratospheric ozone observations at Sodankylä of FMI, just to mention a few, the riometers provide an instrumental basis for studying the possible space weather induced variations in atmospheric properties. We show interpretations of example riometer data during solar particle events, demonstrating observations of space weather effects, as well as examples of long-term trends found in our riometer as well as ionosonde data, which are speculated to be due to an enhanced greenhouse effect.