Pedersen current carried by electrons in auroral D-region

Abstract

We present, for the first time, an appearance of Pedersen current layer carried by the electrons in the auroral D-region. Such a layer was detected by the EISCAT VHF radar in Troms, Norway when an intense pulsating aurora (PA) occurred. Due to the high-energy electron precipitation during the PA, a significant ionization was observed not only in the E-region but also in the upper part of the D-region (80-95 km). An altitude profile of the Pedersen conductance derived from EISCAT exhibited two distinct layers of enhanced conductance. The upper one occurred at 120 km altitude which corresponded to the normal Pedersen current layer carried by the ions. The lower one appeared as a thin layer between 80 and 95 km in altitude, which was mainly carried by the collisional motion of electrons. Such an electron Pedersen layer is detectable only when the electron density is sufficiently high for allowing an appreciable current to flow in the D-region. The Pedersen conductance at the peak of the electron Pedersen layer was 8 × 10 -5 S m -1, which is only 13% of that at the peak of the ion Pedersen layer (6 × 10 -4 S m -1). However, the electron Pedersen current flows exactly in the altitudes where the pulsating ionization occurs; thus, it would play more important role in the closure of FAC associated with the patch of PA.Copyright © 2010 by the American Geophysical Union.