HR: 1340h
AN: SM13A-1185    [Abstracts]
TI: Multi-point observations of density structures in the polar cap
AU: * Santolik, O
EM: ondrej.santolik@mff.cuni.cz
AF: Charles University, Faculty of Mathematics and Physics, Prague, 18000 Czech Republic
AU: Persoon, A M
EM: amp@space.physics.uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Gurnett, D A
EM: gurnett@space.physics.uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Decreau, P
EM: pdecreau@cnrs-orleans.fr
AF: LPCE, CNRS, Orleans, 45071 France
AU: Pickett, J S
EM: jsp@space.physics.uiowa.edu
AF: University of Iowa, Department of Physics and Astronomy, Iowa City, IA 52242 United States
AU: Marsalek, O
EM: ondrej.marsalek@mff.cuni.cz
AF: Charles University, Faculty of Mathematics and Physics, Prague, 18000 Czech Republic
AU: Maksimovic, M
EM: milan.maksimovic@obspm.fr
AF: Observatoire de Paris-Meudon, LESIA, Meudon, 92195 France
AU: Cornilleau-Wehrlin, N
EM: nicole.cornilleau@cetp.ipsl.fr
AF: CETP, IPSL, Velizy, 78140 France
AB: We investigate properties of plasma density irregularities in the polar cap at a radial distance of 5 Earth radii. Our analysis is primarily based on multi-point observations of auroral hiss. We analyze high resolution data of the wave instruments on board the four Cluster spacecraft. The local electron density is estimated, obtaining values close to 1 particle per cc, with density depletions decreasing down to one tenth of the density of the surrounding polar cap plasma. Combined analysis in different points in space gives us the orientation of the normal direction to these structures, the velocity of their drift, their size, and lifetime. We show that the density structures move at speeds of a few km/s. The corresponding convection electric field in the polar cap is then approximately 1 mV/m, consistent with the values expected based on previous observations by different methods. If we map the transverse dimension of the density depletions to the ionospheric heights, we obtain values of the order of a few tens of km. Their lifetime is often longer than tens of seconds.
UR: http://terezka.ufa.cas.cz/santolik/papers/agu2004
DE: 2475 Polar cap ionosphere
DE: 2772 Plasma waves and instabilities
DE: 2776 Polar cap phenomena
DE: 2794 Instruments and techniques
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting