Description
The plasma dynamics in near-Earth space are heavily influenced by the solar wind and associated interplanetary magnetic field (IMF). Physics-based models are widely used to investigate the dynamics of the ionosphere-thermosphere system and the response to solar wind forcing. Since the high latitude and polar regions are strongly coupled to interplanetary space, these regions act as a boundary in the models. However, most numerical simulation techniques are sensitive to boundary conditions, and many ionosphere-thermosphere models use empirical models to characterise electrodynamic driving forces in the high latitude region.
Existing empirical models provide statistical descriptions of high latitude electrodynamics but generally either assume stable solar wind driving or treat all observations equivalently, regardless of whether the IMF is stable or undergoing transition. High latitude Birkeland field-aligned currents and plasma convection patterns have been described both statistically and theoretically. However, the system has a relaxation time for the reconfiguration process into a new steady-state following changes in IMF magnitude and clock angle. When focussing on the high latitude ionosphere, a relaxation time of 20-30 minutes is commonly assumed.
Many statistical analyses of this region have therefore used data from times when the IMF has been stable for a minimum of 20-30 minutes. Using the OMNI solar wind IMF data, this work investigates the limitations of current characterisation methods, proposes dynamic definitions of stable IMF conditions, and characterises the properties of transitions between these states. Finally, we introduce a new statistical framework for classifying solar wind behaviour that captures both stable and transitional IMF conditions, providing a more complete representation of high latitude ionospheric dynamics.
| I am the presenting author | Yes |
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