HR: 0800h
AN: SA31A-0354    [Abstracts]
TI: Plasma line measurements with the EISCAT Svalbard Radar
AU: * Stromme, A
EM: anja@eiscat.se
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AU: Heinselman, C
EM: craig.heinselman@sri.com
AF: SRI International, 333 Ravenswood av., Menlo Park, CA 94025 United States
AU: Rietveld, M
EM: mike.rietveld@eiscat.uit.no
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AU: van Eyken, A
EM: tony@eiscat.se
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AU: Westman, A
EM: assar.westman@eiscat.se
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AU: Haggstrom, I
EM: ingemar@eiscat.se
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AU: Markkanen, J
EM: jussi.markkanen@eiscat.sgo.fi
AF: EISCAT Scientific Association, Box 432, Longyearbyen, 9171 Norway
AB: In Incoherent Scatter Radar (ISR) measurements, the transmitted electromagnetic wave is scattered by naturally occurring wave modes in the ionosphere. Low frequency Landau damped ion acoustic waves traveling parallel and anti-parallel to the radar beam are responsible for the characteristic double-humped ion line, typically some tens of kHz wide. In addition, Langmuir waves traveling along the radar beam produce two spectral peaks known as up- and down-shifted plasma lines. The frequency offsets of the plasma lines are close to the local plasma frequency, i.e. 2-10 MHz for most ionospheric conditions. The scattering from Langmuir waves in a thermal plasma is much weaker than that from the ion acoustic waves and is in practice normally below the detectability thresholds of current ISRs. However, there are mechanisms that lead to the enhancement of these waves above thermal levels. Since routine plasma line measurements at the EISCAT Svalbard Radar (ESR) started, the occurrence of strong features in the plasma lines appears to be much more frequent that at lower latitudes; this has substantial implications for the possible mechanisms responsible for the enhancements. In this paper we will present plasma line data from the ESR system, and discuss enhancement mechanisms which may be at work.
DE: 2407 Auroral ionosphere (2704)
DE: 2455 Particle precipitation
DE: 2483 Wave/particle interactions (7867)
SC: SPA-Aeronomy [SA]
MN: Fall Meeting 2005