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In this study, a new high-latitude empirical model is introduced, named for Auroral energy Spectrum and High-Latitude Electric field variabilitY (ASHLEY). This model aims to improve specifications ...

The expanding/contracting polar cap (ECPC) model, or the time-dependent Dungey cycle, provides a theoretical framework for understanding solar wind-magnetosphere-ionosphere coupling. The ECPC describes the relationship between magnetopause reconnection and substorm growth phase, magnetotail reconnection and substorm expansion phase, associated changes in auroral morphology, and ionospheric convective motions. Despite the many successes of the model, there has yet to be a rigorous test of the predictions or nowcasts made regarding ionospheric convection, which remains a final hurdle for the validation of the ECPC. In this study we undertake a comparison of ionospheric convection, as measured in situ by ion drift meters on board DMSP (Defense Meteorological Satellite Program) satellites and from the ground by SuperDARN (Super Dual Auroral Radar Network), with motions nowcasted by a theoretical model. The model is coupled to measurements of changes in the size of the polar cap made using global auroral imagery from the IMAGE FUV (Imager for Magnetopause to Aurora Global Exploration Far Ultraviolet) instrument, as well as the dayside reconnection rate, estimated using the OMNI data set. The results show that we can largely nowcast the magnitudes of ionospheric convection flows using the context of our understanding of magnetic reconnection at the magnetopause and in the magnetotail.

[1] We describe the introduction of the first all-sky imaging system for low-light-level optical observations of the disturbed ionosphere over mid-latitude Europe. Using 6300 angstrom auroral emissions that come from the 200-400 km altitude range, we demonstrate that sub-visual optical patterns spanning the European continent can be obtained from a single site in Italy. Pilot observations during the 26-27 September 2011 geomagnetic storm show that the diffuse aurora's low latitude boundary can be used to find where the poleward wall of the ionospheric trough is located. This relates directly to regions of radiowave disruptions caused by the precipitation of energetic particles from the magnetospheric plasma sheet that move to lower latitudes during space weather events. Images of stable auroral red (SAR) arcs can be used to track the magnetospheric ring current and plasmapause location, a second region of radiowave interference. Comparisons with ground-based and satellite observations of the ionosphere during the same storm demonstrate how ASI images reveal the lowest energy components of magnetospheric input to the ionosphere-thermosphere system. Such observations can be used, potentially, for both now-casting of storm effects spanning Europe, and for retrospective validation of existing models of space weather impacts at sub-auroral locations. Citation: Baumgardner, J., et al. (2013), Imaging space weather over Europe, Space Weather, 11, 69-78, doi:10.1002/swe.20027.

[1] For most space scientists, the general expectation of ionospheric measurements is that if properly binned, observations will obey a normal or Gaussian distribution. This paper challenges this assumption and argues that a lognormal distribution can better describe ionospheric densities. It presents a simple mathematical argument for ionospheric density observations obeying a lognormal distribution. To demonstrate the efficacy of the lognormal distribution, a sample distribution of total ion densities is presented and is compared with a lognormal distribution characterized by parameters estimated from the data. This distribution of DMSP observations fits a lognormal distribution with a probability plot correlation coefficient (PPCC) of 0.99932. The PPCC is the linear correlation between the ordered distribution and ordered statistical medians and measures how well a given set of values conforms to a given distribution. When the PPCC = 1, the distribution perfectly fits the data. When binned by solar activity (on the basis of the F10.7 cm proxy) and geomagnetic latitude, over 95.3% of the binned observations follow a lognormal distribution with a PPCC over 0.9. Since the topside electron densities tend to obey a lognormal distribution, the existing metrics for forecast performance need to be revised.