Decrease of the first Schumann resonance frequency during solar proton events

The variations of the first-order Schumann resonance frequency in Kola peni nsula are studied for four solar proton events on November 4 and 6, 1997 an d on May 2 and May 6, 1998. It is found that the frequency decreases by abo ut 0.15 Hz during the peaks of the proton penetrations. Such a decrease is in agreement with modeling calculations. A very intensive solar X ray burst preceding the proton flare on November 6 caused an increase of the resonan ce frequency. The decrease of amplitude about of 0.2 pT and the decrease of the resonance bandwidth about of 0.2 Hz are observed in the November event s.