Abstract
Abstract. The antiparallel merging hypothesis states that reconnection takes place on the dayside magnetopause where the solar and geomagnetic fields are oppositely directed. With this criterion, we have mapped the predicted merging regions to the ionosphere using the Tsyganenko 96 magnetic field model, distinguishing between regions of sub-Alfvénic and super-Alfvénic magnetosheath flow, and identifying the day-night terminator. We present the resulting shape, width and latitude of the ionospheric dayside merging regions in both hemispheres, showing their dependence on the Earth's dipole tilt. The resulting seasonal variation of the longitudinal width is consistent with the conjugate electric fields in the northern and southern cusps, as measured by the SuperDARN HF radars, for example. We also find a seasonal shift in latitude similar to that observed in satellite cusp data.Key words: Ionosphere (ionosphere-magnetosphere interactions) · Magnetospheric physics (magnetopause · cusp and boundary layers; magnetosphere-ionosphere interactions)
Highlights
The concept of magnetic reconnection at the dayside magnetopause, introduced by Dungey (1961), has become accepted as the most important process conditioning the interaction between the solar wind and the terrestrial magnetosphere
The potential drop across the magnetopause X -line is mapped to the ionosphere by newly reconnected ®eld lines: the consequences of this projected merging line can be observed in enhancedows, particle precipitation and polar cap boundary
Using the antiparallel merging hypothesis, we have modelled the mapping of dayside magnetospheric reconnection sites to the ionosphere, in both hemispheres for a range of seasons, for southward IMF
Summary
The concept of magnetic reconnection at the dayside magnetopause, introduced by Dungey (1961), has become accepted as the most important process conditioning the interaction between the solar wind and the terrestrial magnetosphere. We employ the antiparallel merging hypothesis (Crooker, 1979) here, which states that reconnection takes place on those regions of the magnetopause where the magnetosheath and magnetopause ®elds are oppositely directed. Lockwood (1997) noted that Stasiewicz had neglected ®eld line draping, and had virtually no openux threading the dayside magnetopause This study includes both these phenomena in the modelling. We discuss the sensitivity of the results to the model parameters
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