TY JOUR TI The Borok INTERMAGNET magnetic observatory KW Borok Geophysical Observatory KW INTERMAGNET KW magnetic observatories KW geomagnetic jerks KW geomagnetic data. JO Russian Journal of Earth Sciences AU Chulliat, A.. AU Anisimov, S.. PY 2008 IS 10 PB Geophysical Center of the Russian Academy of Sciences