Electric fields at L = 2.5 during geomagnetically disturbed conditions

We have used observations of the group time delay and Doppler shift of ducted VLF whistler mode signals propagating near L = 2.5 to deduce the azimuthal component of the plasmaspheric electric field during geomagnetically disturbed periods in June and July 1986. The whistler mode signals originated in the US Navy transmitters NAA and NSS and were recorded at Faraday, Antarctica. The average Ewversus LT curve for periods when Kp > 2+ has been compiled; when this is compared with the Ewversus LT curve for quiet times, it is found that the electric field is more eastwards from 18–22 LT and more westwards from 00–01 LT in disturbed times. This difference is consistent with published calculations of the penetration of the dawn-dusk electric field to L = 2.5. A variety of behaviour is evident when the data are examined on a case to case basis. Sometimes the dawn-dusk electric field becomes apparent during isolated intense substorms; this is attributed to increased penetration due to an increase in the auroral zone Pedersen conductivity. On one night the drifts seemed to be partly due to the ionospheric disturbance dynamo.


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Authors: Saxton, J.M., Smith, A.J.

1 September, 1991
Planetary and Space Science / 39
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