Response of the high-latitude ionospheric convection to changes in the interplanetary medium
thesisposted on 15.12.2014, 10:40 by Hina. Khan
Studies have been conducted on the flow in the high-latitude ionosphere and how this depends on the properties of the interplanetary medium. Specifically, the response of the convection pattern of changes in the interplanetary magnetic field (IMF) have been studied in detail, using the European Incoherent Scatter (EISCAT) radar to measure ~300 h of tristatic field-perpendicular F region ionospheric velocities at 66.3o magnetic latitude, in combination with simultaneous solar wind/IMF measurements from theIMP-8 spacecraft located upstream of the bow shock.;Firstly, a statistical cross-correlation analysis is performed using each ionospheric flow component and a function of IMF Bz for all local times. Upon combining the response delays from each of the velocity components to determine the 'first response' of the flow to IMF changes, the minimum response delay was found to occur at 1400 MLT. The average response delay over the 12 h interval centred on 1400 MLT is 1.3 0.8 min, while that for the 12 h sector centred on 0200 MLT is 8.8 1.7 min. A second complementary 'event study' was conducted on the same data set, where polarity changes in IMF Bz were located and the time for the ionosphere to respond examined. The combined data set also indicated a minimum response delay centred on 1400 MLT, with the 'dayside' average as 4.80.5 min, and the 'nightside' increasing to 9.20.8 min.;Finally, the perturbation flow effect an auroral zone field lines associated with IMF By was examined through a cross-correlation analysis of the velocity components with IMF By. A principally zonal eastward flow perturbation ~several tens of m s-1 nT-1 was observed for positive IMF By. A model describing the distortion of the magnetospheric field lines with a perturbation IMF By was used, producing the correct orientation and magnitude of the flow effect observed, when an appropriate magnetospheric model was used.