VARIATION OF THE GEOMAGNETIC-FIELD IN COSTA-RICA DURING THE TOTAL SOLAR ECLIPSE OF JULY 11, 1991

Ground measurements of the geomagnetic field. during the total solar e clipse of July 11, 1991, were carried out at three sites in Costa Rica located within the eclipse's path of totality. Near totality, there w as a significant change in the total intensity. F. Its normal decrease in the afternoon hours was interrupted during a period of about 45 mi n, in which F varied very little. This was due mainly to a small varia tion in horizontal intensity, H, during such a period. The departure o f F from normal lasted about 100 min; its maximum departure was near 1 0 nT and occurred about 38 min after totality. The declination, D, als o experienced a small change (about 2.3 min) during the total period o f the eclipse. The vertical intensity, Z. and the inclination, 1, did not show significant changes.