Radio Science

Long and Short Period Changes in Magnetic Activity at Huancayo During the Solar Cycle


  • Edwin J. Chernosky


Forty years of geomagnetic activity data at Huancayo are evaluated in two periodicities: the hourly and the daily changes of the horizontal magnetic field intensity. Monthly means of both periodicities are affected similarly by solar activity in that they both show the characteristic semiannual variation. Although the amplitudes of the hourly changes follow solar activity changes closely, the daily changes show a ‘bite out’ near sunspot maximum when annual means of each are compared. The ‘bite out’ may be due to the occurrence of magnetic storm depressions of a different duration at that time. The results suggest that the slower magnetic variations at the dip equator should not be studied as a single manifestation but in periodicity bands, as micropulsations are studied.