HR: 1340h
AN: SA13A-0231    [Abstracts]
TI: The Absolute Scattering Cross-Section of Polar Mesospheric Summer Echoes at VHF and UHF radar frequencies
AU: * La Hoz, C
EM: Cesar.La.Hoz@phys.uit.no
AF: University of Tromsø, Auroral Observatory, Tromsø, 9037 Norway
AU: Havnes, O
EM: Ove.Havnes@phys.uit.no
AF: University of Tromsø, Auroral Observatory, Tromsø, 9037 Norway
AU: Rietveld, M
EM: Mike.Rietveld@eiscat.uit.no
AF: EISCAT Scientific Association, EISCAT, Ramfjordbotn, 9027 Norway
AU: Næsheim, L
EM: Lars.Nasheim@phys.uit.no
AF: University of Tromsø, Auroral Observatory, Tromsø, 9037 Norway
AB: Simultaneous and collocated measurements of Polar Mesospheric Summer Echoes (PMSE) with the EISCAT VHF (224 MHz) and the UHF (930 MHz) radars and ionosonde measurements of electron number density, have allowed to make accurate calculations of the absolute cross-section of PMSE. The values of the cross-sections per unit volume obtained are in the range of a few times 10^-15--10^-14 m^-1 for the VHF measurements and a few times 10^-18--10^-17 m^-1 for the UHF measurements, namely the VHF echoes are typically three orders of magnitude stronger than the UHF echoes. These results are at variance with proposed theories of PMSE. In particular, the theory based on neutral air turbulence with an extended convective-diffusive subrange due to charged dust particles as the driver of the electron inhomogeneities, predicts that the strength of PMSE at the VHF frequency should be about 70 times stronger than the strength of PMSE at the UHF frequency. Thus, we suggest that PMSE still remains largely unaccounted for by any theory.
DE: 0305 Aerosols and particles (0345, 4801, 4906)
DE: 0335 Ion chemistry of the atmosphere (2419, 2427)
DE: 0340 Middle atmosphere: composition and chemistry
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005