Solar and Magnetic Declination Control on the Electrojet and Distributed Currents in the Ionosphere over Jicamarca

摘要

Daytime variation in the average east-west drift velocity of electrons in the height range of 95 to 110 km over Jicamarca (0.9 deg N, dip latitude), Peru, estimated from VHF radar measurements, is compared with variation in the horizontal component of the geomagnetic field at the closeby Huancayo station (0.6 deg N, dip latitude). On magnetically quiet days, the ratio of delta H to the electron drift velocity shows a local time variation asymmetric with respect to local noon, though one would expect a symmetric cos X (where X is the solar zenith angle) type of variation for the same, if indeed delta H arises solely from the electrojet region in which the electron drift velocities are measured. The observed asymmetry indicates significant contribution of distributed currents from height regions above the electrojet in the integrated current represented by delta H. Further, the observed seasonal variation in the degree of the asymmetry seems to point out the importance of magnetic and solar declination angles in controlling the relative contributions of the distributed (and electrojet) currents to the magnitude of the observed delta H values.