HR: 11:35h
AN: SM42A-06    [Abstracts]
TI: Ionospheric electron upflow along open field lines: Derived from ISIS 2 measurements
AU: Nsumei, P
EM: Patrick_Nsumei@student.uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk St., Lowell, MA 01854, United States
AU: * Song, P
EM: Paul_Song@uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk St., Lowell, MA 01854, United States
AU: Reinisch, B W
EM: Bodo_Reinisch@uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk St., Lowell, MA 01854, United States
AU: Tu, J
EM: Jiannan_Tu@uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk St., Lowell, MA 01854, United States
AU: Huang, X
EM: Xueqin_Huang@uml.edu
AF: Center for Atmospheric Research, University of Massachusetts Lowell, 600 Suffolk St., Lowell, MA 01854, United States
AB: Using the mass conservation equation, the parallel electron upflow velocity normalized by the base velocity in the open field line region of the topside ionosphere is derived as a function of electron density and neutral species densities. The normalized parallel velocity profiles are calculated using ISIS 2 electron density profile observations and neutral species density profiles from the MSIS model. From the cases analyzed, the derived velocity profiles show a similar trend of (a) a region of slow acceleration starting at the ionospheric F layer density peak height and up to about 150 km above it, (b) a region of fast acceleration (~ 500 km - 1100 km), and (c) another region of weak or no acceleration (> ~1100 km). A simple analytical function is proposed to describe the normalized parallel velocity profile. The parameters in the function have been determined by a multivariate least-square fit of calculated profiles to the analytical expression. These parameters define the magnitude and the height of maximum acceleration. For the cases studied the maximum acceleration height is in the range of 774 - 924 km. The parallel velocity can increase by a factor of up to 8 within the acceleration region. The results from the cases studied suggest that the chosen analytical function suitably describes the normalized parallel electron velocity in the high-latitude topside ionosphere. Furthermore, the acceleration mechanisms have been investigated. Using an existing model of the electron temperature, our results suggest that the enhanced pressure gradient force at low ionospheric altitudes may be the main driver of the observed acceleration in the electron upflow.
DE: 2431 Ionosphere/magnetosphere interactions (2736)
DE: 2437 Ionospheric dynamics
DE: 2451 Particle acceleration
DE: 2475 Polar cap ionosphere
DE: 2736 Magnetosphere/ionosphere interactions (2431)
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Joint Assembly