Abstract
AbstractWe exploit a database of high‐latitude ionospheric electric potential patterns, derived from radar observations of plasma convection in the Northern Hemisphere from the years 2000–2006, to investigate the timescales of interplanetary magnetic field (IMF) control of ionospheric convection and associated magnetospheric dynamics. We parameterize the convection observations by IMF clock angle, θ (the angle between geocentric solar magnetic (GSM) north and the projection of the IMF vector onto the GSM Y‐Z plane), and by an IMF timescale, τB (the length of time that a similar clock angle has been maintained prior to the convection observations being made). We find that the nature of the ionospheric convection changes with IMF clock angle, as expected from previous time‐averaged studies, and that for τB∼30 min, the convection patterns closely resemble their time‐averaged counterparts. However, as τB increases we find that the convection evolves away from the time‐averaged patterns to reveal modified characteristic flow features. We discuss these findings in terms of solar wind‐magnetosphere‐ionosphere coupling and consider their implications for understanding the time‐dependent nature of magnetospheric dynamics.
Highlights
Magnetic reconnection between the interplanetary and terrestrial magnetic fields drives convection of plasma and magnetic flux in the coupled magnetosphere-ionosphere system [Dungey, 1961]
We find that the nature of the ionospheric convection changes with interplanetary magnetic field (IMF) clock angle, as expected from previous time-averaged studies, and that for τB ∼30 min, the convection patterns closely resemble their time-averaged counterparts
The observations described above show that, in addition to the expected dependencies on IMF orientation reported by numerous authors [e.g., Heppner and Maynard, 1987; Rich and Hairston, 1994; Weimer, 1995; Ruohoniemi and Greenwald, 1996, 2005], the nature of the high-latitude ionospheric convection pattern is dependent on the length of time over which a given IMF orientation has been dominant at the magnetopause
Summary
Magnetic reconnection between the interplanetary and terrestrial magnetic fields drives convection of plasma and magnetic flux in the coupled magnetosphere-ionosphere system [Dungey, 1961]. The history of the IMF may be expected to play a role in governing the dynamics of the system for timescales of anywhere up to 12 h, given that its influence may persist on open and newly closed flux during this time This is likely in respect to the influence of IMF BY (i.e., the dusk-dawn component defined in, for example, geocentric solar magnetospheric coordinates, or GSM), which is known to introduce a dusk-dawn asymmetry into the coupled magnetosphere-ionosphere system and which tends to demonstrate a longer characteristic timescale in the system than BZ. We utilize this method to investigate the effects of solar wind-magnetosphere-ionosphere coupling over various timescales
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
