Secular variations of the geomagnetic field and solar activity
© Sumaruk Yu., Reda J.
The attempt was made to separate SV generated by external sources. The data from the following observatories
were used: Nurmijarvi, Lerwick, Leningrad, Niemegk, Belsk, Hartland, Kiev, Lviv, Chambonla Foret,
Odessa, Surlari, Coimbra. It was shown that three types of SV due to external sources exist. Short period
variations (about two years) and middle period (about 11 years) are well known. Assumption is made that long-term
modulation of SV with period of 80 year exists. The modulation also happens due to solar activity changes.