Abstract
Particular emphasis is laid on the application of whistlers recorded at low latitude ground station, Nainital during magnetically quiet times to estimate the eastward/westward electric field in the plasmasphere. The east-west components of electric field during quiet magnetic (average Kp = 1) are obtained for the first time from low latitude station on the basis of the available whistler data on March 7, 1971 (ΣKp = 8) in the 01:22 to 03:21 IST sector and 22:10 to 23:20 IST sector, April 18, 1971 (ΣKp = 19-) in the 22:15 to 23:44 IST sector and April 19, 1971 (ΣKp = 15) in the 01:26 to 03:31 IST sector. During above quiet times in the whistler activity period, a decrease in dispersion with time is observed. The method of measuring electric field from the observed cross-L motion of whistler ducts within the plasmasphere, indicated by changes in nose frequency of whistlers has been outlined. The nose frequency of the non-nose whistlers under consideration have been deduced by means of an accurate curve fitting method as developed by Tarcsai (1975). Our measurements demonstrate an average estimated electric field of ∼0.06 mVm-1 in the premidnight local time sector and an average westward electric field of ∼0.05 mVm-1 in the post-midnight local time sector. These values are in good agreement with similar results reported by earlier workers. Near midnight there is a sharp transition from eastward field to westward electric field. The electric fields during quiet days at low latitudes are thought to be generated by the dynamo mechanism.
