DP 2 electric field fluctuations in the dusk-time dip equatorial ionosphere

Abstract

We have studied the geomagnetic and ionospheric manifestations of the DP 2 activity that occurred on April 7, 1995 using high time resolution magnetometer data of IMAGE network in Scandinavia and of Alcantara (dip 1.2° N), Brazil, and F layer vertical plasma drift, Vz measured by an HF Doppler radar at Kodaikanal (dip 4° N), India. Quasi-periodic fluctuations in dusk-time (1730-1900 LT) F layer vertical plasma drift (eastward electric field) occurred over Kodaikanal coherent with DP 2 type magnetic fluctuations (period ≈ 25 min) at the day-side dip equator and auroral/subauroral latitudes. This first-ever observation at the dusk-side equator is in agreement with the two-cell equivalent current system previously proposed for DP 2 fluctuations. The results strongly suggest that the magnetospheric electric field responsible for DP 2 fluctuations penetrates to equatorial ionosphere on the dusk-side as on the day-side. An additional observation is that the electric field fluctuation amplitude increases towards the nightside suggesting the influence of dusk sector electrodynamics in the observed signature of the DP 2 electric field.