Geomagnetic field variations observed by INTERMAGNET during 4 total solar eclipses

Abstract

We investigate variations of the geomagnetic field observed by INTERMAGNET geomagnetic observatories over which the totality path passed during a total solar eclipse. As a result, we have presented results of examining the geomagnetic field data observed by 6 geomagnetic observatories during the 4 total solar eclipses (11 August 1999, 1 August 2008, 11 July 2010, and 20 March 2015). These total solar eclipses are the only total solar eclipse, since 1991 when the INTERMAGNET began to work, during which the umbra of the Moon swept an INTERMAGNET geomagnetic observatory and simultaneously variations of the geomagnetic field are recorded at the geomagnetic observatory. We have confirmed previous reports that, at least on average, during the solar eclipse characteristic increase of Y component of the geomagnetic field Y and decreases of X,Z and F are conspicuous. Interestingly, we have noted that variations of X,Y,Z and F observed during the total solar eclipse at Isla de Pascua Mataveri (Easter Island) in Chile (IPM) in the southern hemisphere show distinct decrease of Y and increases of X and Z on the contrary. We have found, however, that variations of X,Y,Z and F observed at Hornsund in Norway (HRN) at 77°N in latitude seem to be dominated by other geomagnetic occurrence since the solar activity is near maximum, and the geomagnetic field is disturbed on the day of eclipse. We further discuss a possibility of exploring an effect of the solar eclipse on the amplitude of harmonic components of the geomagnetic field using the wavelet analysis technique, which has revealed suppression in the amplitude during the middle of a solar eclipse. Finally, we conclude by discussing implications of what we have found.