Abstract
AbstractWe present Super Dual Auroral Radar Network observations of ionospheric convection during substorms. Substorms were grouped according to their onset latitude, onset magnetic local time, and the prevailing sense of interplanetary magnetic field (IMF) BY. The radar observations were then sorted according to substorm group and average convection patterns produced. Here we discuss the patterns corresponding to substorms with onsets occurring in the 65∘–67∘ onset latitude range, at either early (20–22 h) or late (01–03 h) magnetic local times, during intervals of either dominant positive or negative IMF BY. We show that the morphology of the convection patterns differs from that predicted by existing empirical models, with the location of the nightside convection throat being largely consistent with the location of substorm onset. The expected IMF BY‐induced dawn‐dusk convection asymmetry can be enhanced on the nightside when the substorm onset occurs at a fortuitous location but can equally be removed or even reversed from this expected state. Thus, the nightside convection asymmetries are seemingly unrelated to the instantaneous sense of IMF BY.
Highlights
The morphology of the ionospheric convection pattern is governed by the superposition of flows driven independently by dayside coupling processes and by internal magnetospheric dynamics such as substorms (e.g., Lockwood et al, 1990)
We show that the morphology of the convection patterns differs from that predicted by existing empirical models, with the location of the nightside convection throat being largely consistent with the location of substorm onset
In this paper we have presented maps of the average ionospheric convection morphology for different conditions of interplanetary magnetic field (IMF) orientation and substorm onset location
Summary
The morphology of the ionospheric convection pattern is governed by the superposition of flows driven independently by dayside coupling processes (e.g., magnetopause reconnection) and by internal magnetospheric dynamics such as substorms (e.g., Lockwood et al, 1990). It is well documented that in the case of dayside driving, the BY component of the interplanetary magnetic field (IMF) introduces asymmetries into the coupled solar wind-magnetosphere-ionosphere system (Haaland et al, 2017, and references therein). The morphology at any given time will be governed by a combination of IMF BY , dipole tilt angle (e.g., Pettigrew et al, 2010) and the effects of internal magnetotail driving (e.g., Grocott, 2017). Substorms are already known to influence the ionospheric convection in ways that will produce asymmetries. Weimer (1999, 2001, 2005), for example, used Dynamics Explorer 2 spacecraft observations of the ionospheric electric field to reveal that the Harang discontinuity (Maynard, 1974) was considerably more pronounced when substorms were in progress. Provan et al (2004) and Bristow and Jensen (2007) used Super Dual Auroral
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