Abstract
Abstract. Interhemispheric contrasts in the ionospheric convection response to variations of the interplanetary magnetic field (IMF) and substorm activity are examined, for an interval observed by the Polar Anglo-American Conjugate Experiment (PACE) radar system between ~1600 and ~2100 MLT on 4 March 1992. Representations of the ionospheric convection pattern associated with different orientations and magnitudes of the IMF and nightside driven enhancements of the auroral electrojet are employed to illustrate a possible explanation for the contrast in convection flow response observed in radar data at nominally conjugate points. Ion drift measurements from the Defence Meteorological Satellite Program (DMSP) confirm these ionospheric convection flows to be representative for the prevailing IMF orientation and magnitude. The location of the fields of view of the PACE radars with respect to these patterns suggest that the radar backscatter observed in each hemisphere is critically influenced by the position of the ionospheric convection reversal boundary (CRB) within the radar field of view and the influence it has on the generation of the irregularities required as scattering targets by high-frequency coherent radar systems. The position of the CRB in each hemisphere is strongly controlled by the relative magnitudes of the IMF Bz and By components, and hence so is the interhemispheric contrast in the radar observations.Key words. Magnetospheric physics · Auroral phenomena · Magnetosphere-ionosphere interactions · Storms and substorms
Highlights
A number of so-called conjugate studies were carried out during the 1950s and 1960s
In the present study we examine an example of interhemispheric contrast in the ionospheric convectionow, observed by the Polar AngloAmerican Conjugate Experiment (PACE) system, which can be attributed to a large-scale interhemispheric dierence in the position of the convection reversal boundary and the MLT of the observing instrumentation
Each of the periods outlined in the previous section will be discussed with reference to the model proposed by Cowley and Lockwood (1992), which describes the auroral ionospheric convection pattern in terms of two time-variant driving mechanisms associated with magnetic ®eld line merging at the dayside magnetopause and within the nightside magnetotail
Summary
A number of so-called conjugate studies were carried out during the 1950s and 1960s (see reviews by Wescott, 1966; Oguti, 1969; Nagata, 1987). An investigation of the high-latitude convection pattern, observed simultaneously in both hemispheres observed by high-frequency (HF) radars, can provide the opportunity to examine the time-dependent nature of the coupling between the solar wind, magnetosphere and ionosphere during a period of energy transfer throughout the solar wind-magnetosphere-ionosphere system Such a conjugate study undertaken during a period of substorm activity will provide valuable information concerning the mechanism of, and the ionospheric response to, the substorm process within opposite hemispheres and the control of such a process by the orientation and magnitude of the IMF. In the present study we examine an example of interhemispheric contrast (non-conjugacy) in the ionospheric convectionow, observed by the PACE system, which can be attributed to a large-scale interhemispheric dierence in the position of the convection reversal boundary and the MLT of the observing instrumentation The location of this boundary in each hemisphere is suggested to be controlled by the IMF. The location of theow reversals from the satellite data provides a representation of the auroral ionospheric convection pattern independent of the ground-based radar data
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