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Ann. Geophys., 24, 2949-2957, 2006
www.ann-geophys.net/24/2949/2006/
© European Geosciences Union 2006
On the height variation of the E-region cowling conductivity – effect of charged dust particles
P. Muralikrishna1 and V. H. Kulkarni2
1Instituto Nacional de Pesquisas Espaciais – INPE, C.P. 515, 12201-970, S. J. Campos-SP, Brazil
2University of Bombay, Mumbai, India
Abstract. Height profiles of the Cowling conductivity in the electrojet region,
estimated using the atmospheric parameters given by the existing models like
CIRA or MSIS and measured electron density profiles, consistently show the
heights of the electrojet current intensity peak to be more than 3 km below
those estimated from in-situ measurements using magnetometers on board
sounding rockets. Kulkarni and Muralikrishna (2005) attempted to explain
this to be due to the effect of neutral dust particles. They reported that
neutral dust particles, when they exist in sufficient numbers, can modify the
collision parameters, especially in the lower E-region, where dust particles
of meteoric origin are known to exist in large numbers, and thereby can
modify the Cowling conductivity profile in the electrojet region. This work
is extended here to include the effect of charged dust particles. Dust
particles can become charged negatively by the attachment of ambient free
electrons, and can thus reduce the number density of free electrons
especially below the electrojet peak. This can alter the vertical profile of
the east-west Hall current driven by the vertical Hall polarization field,
thereby causing a net reduction in the electrojet current. Such a decrease
in the electrojet current may be observed on the ground magnetograms. This
mechanism, as proposed here, can operate only during periods of strong
meteor shower activity, when the dust particle density at the assumed
deposit height of 103 km can reach extreme values (for example,
5×104 cm−3 of 1-µm diameter dust particles). Such a dense dust
layer may even cause a reversal in the normally upward vertical Hall
polarization field, within the dust layer, causing a reversal of the
electrojet currents below the current peak.
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