HR: 0830h
AN: SA21B-0076    [PDF]
TI: Plasma Viscous Heating in Sheared Regions of the High Latitude Ionosphere
AU: * La Hoz, C
EM: Cesar.La.Hoz@phys.uit.no
AF: Dept. of Earth and Atmospheric Sciences, 2122 Snee Hall, Cornell University, Ithaca, NY 14853 United States
AU: * La Hoz, C
EM: Cesar.La.Hoz@phys.uit.no
AF: Dept. Of Physics, University of Tromso, Auroral Observatory, Tromso, N-9037 Norway
AU: Kebede, S
EM: Solomon.Kebede@phys.uit.no
AF: Dept. Of Physics, University of Tromso, Auroral Observatory, Tromso, N-9037 Norway
AU: Brekke, A
EM: Asgeir.Brekke@phys.uit.no
AF: Dept. Of Physics, University of Tromso, Auroral Observatory, Tromso, N-9037 Norway
AB: A sheet of plasma with elevated ion and electron temperatures has been observed in the high latitude ionosphere with the EISCAT tri-static UHF radar in Northern Scandinavia. The sheet has a thickness of about 100-200 km along geomagnetic latitude or 1-2 degrees and is extended in altitude from about 200 km to beyond the highest measured altitude of 500 km. Both temperatures are several times hotter in the sheet than in the surrounding plasma, reaching up to 7000 K in some occasions. The transition from background values of 1000-2000 K is very sharp. The hot sheet or hot spot is aligned precisely with a region of large velocities and very large shears in the ionospheric plasma convection pattern. The shear is manifested mostly by abrupt changes in direction -- which some times may result in reversals -- and sometimes by transitions to very low velocities. Numerical solutions of the energy balance equation including viscous heating as the source and convection and conduction as the sinks reproduce the measurements well indicating that energy of magnetospheric origin is primarily transfered to the ionosphere by viscous heating in regions of high convection velocity shears.
DE: 2407 Auroral ionosphere (2704)
DE: 2411 Electric fields (2712)
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2463 Plasma convection
DE: 2467 Plasma temperature and density
SC: SPA - Aeronomy [SA]
MN: 2003 Fall Meeting