Earth Planets Space, Vol. 58 (No. 6), pp. 735-740, 2006
Pavel Hejda, Josef Bochníek, Josef Horáek, and Jaroslava Nejedlá
Geophysical Institute of the Academy of Sciences, 141 31 Prague, Czech Republic
(Received April 28, 2005; Revised June 9, 2005; Accepted June 10, 2005; Online published June 2, 2006)
The quality of magnetic surveys is essentially influenced by the geomagnetic activity. As the in situ mea-surements are usually limited to very short time period, they must be compared with observatory continuous registrations. When reducing measurements one makes an assumption that diurnal variations of the magnetic field are identical at both the station and the reference observatory. During magnetically quite periods, this as-sumption is satisfied to an acceptable extent. However, under high geomagnetic activity, the error may easily exceed the acceptable limit. Our analysis indicates that, in mid-latitudes, magnetic surveys should not be made, if some of the Kp values are over 5. Long-term and medium-term forecasts of geomagnetic activity are based on known periodicities (11-year, half-year and 27-day). Short-term forecasts are based on the knowledge of the ac-tual conditions on the Sun, in the solar wind and in the interplanetary magnetic field. Regional Warning Centres, associated in the International Space Environment Service (ISES) deal with forecasts of geomagnetic activity. Links to all 12 centres can be obtained through http://www.ises-spaceweather.org/about ises/index.html.
Key words: Magnetic surveys, repeat stations, geomagnetic activity.