Physics
Scientific paper
Jan 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006adspr..38.2541b&link_type=abstract
Advances in Space Research, Volume 38, Issue 11, p. 2541-2550.
Physics
16
Scientific paper
The radar phenomenon PMSE (Polar Mesospheric Summer Echo), which is associated with the charged dust in the noctilucent clouds (NLCs), can be affected by artificial electron heating. If the heater is run in a cycle with equal, and comparatively short (10 20 s) off and on periods, the PMSE strength is observed to weaken when the heater is on, and recover to approximately the same strength when the heater is switched off [Chilson, P.B., Belova, E., Rietveld, M.T., Kirkwood, S., Hoppe U.P., 2000]. First artificially induced modulation of PMSE using the EISCAT heating facility. Geophys. Res. Lett. 27, 3801]. We have adopted a new heater cycling, during which the heater is on for 20 s and then off for a period of 160 s. With this cycling we very often observe an “overshoot” effect where the PMSE strength, when the heater is switched off, increases by a factor of several compared to what it was directly before the heater was switched on [Havens, O., LaHoz, C., Naesheim, L.I., Rietveld, M.T., 2003. Chilson, P. B., Belova, E., Rietveld, M. T., Kirkwood, S., Hoppe U. P., 2000. First artificially induced modulation of PMSE using the EISCAT heating facility. Geophys. Res. Lett. 30, 2229]. By analysing the time-dependant reflected power showing that the PMSE weakens when the heater is switched on, overshoot when it is switched off and subsequently relaxes back to the original strength, we should be able to obtain a considerable amount of information about the PMSE dusty plasma. Until now, the only model presented for the overshoot is based on the assumption that the dust density is low so that absorption of plasma by the dust does not seriously affect the overall electron and ion density throughout the overshoot cycle. Observations indicate that this probably is true in many, possibly most cases, but it will not always be the case. Here, we present a model for the overshoot in which we include the absorption of plasma due to the dust. If the dust density is comparatively high, this will influence the equilibrium density of the plasma, since the dust is a sink for plasma. Further, when the electrons are heated, the flux of electrons to the dust increases and the background electron density will also decrease during the time the heater is on. We will present model results and compare with observations and discuss the possible information which can be gained from the overshoot effect.
Biebricher A.
Hartquist Thomas W.
Havnes Ove
Lahoz C.
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