Search for: All records

Abstract. It is well known that the polar cap, delineated by the open–closed field line boundary (OCB),responds to changes in the interplanetary magnetic field (IMF).In general, the boundary moves equatorward when the IMF turns southward and contractspoleward when the IMF turns northward. However,observations of the OCB are spotty and limited in local time,making more detailed studies of its IMF dependence difficult.Here, we simulate five solar storm periods with the coupled model consisting of the OpenGeospace General Circulation Model (OpenGGCM) coupled with the Coupled Thermosphere IonosphereModel (CTIM) and the Rice Convection Model (RCM),i.e., the OpenGGCM-CTIM-RCM, to estimate the location and dynamics of the OCB.For these events, polar cap boundary location observations are also obtained from Defense MeteorologicalSatellite Program (DMSP) precipitation spectrograms and compared with the model output.There is a large scatter in the DMSP observations and in the model output.Although the model does not predict the OCB with high fidelity for every observation,it does reproduce the general trend as a function of IMF clock angle.On average, the model overestimates the latitude of the open–closed field line boundaryby 1.61∘. Additional analysis of the simulated polar cap boundary dynamics acrossall local times shows that the MLT of the largest polar cap expansion closely correlateswith the IMF clock angle, that the strongest correlation occurs when the IMF is southward, thatduring strong southward IMF the polar cap shifts sunward, and that the polar cap rapidlycontracts at all local times when the IMF turns northward. 

Community honours, such as those bestowed by professional scientific societies like the American Geophysical Union (AGU) are an important element of both individual career advancement and contributes to the historical record of scientific progress. The process by which honours are bestowed is not widely shared amongst the community. The purpose of this article is to share the recent experiences of several members of the AGU Space Physics and Aeronomy (SPA) Fellows committee. We outline the criteria for selection, the evaluation process, difficulties encountered by the committee, and steps taken to mitigate these difficulties. Of particular note is the impact of implicit bias in the award system. Steps could be taken by the awarding scientific societies to reduce the impact of these biases, but in the meantime individual award committees can employ some of the strategies we outline in this article. By sharing our experiences, we hope to improve the process of granting awards and honours for the scientists putting together award nominations, future committee members, and the scientific societies granting these awards. 

Recent analysis of energetic electron measurements from the Magnetic Electron Ion Spectrometer instruments onboard the Van Allen Probes showed a local time variation of the equatorial electron intensity in the Earth’s inner radiation belt. The local time asymmetry was interpreted as evidence of drift shell distortion by a large-scale electric field. It was also demonstrated that the inclusion of a simple dawn-to-dusk electric field model improved the agreement between observations and theoretical expectations. Yet, exactly what drives this electric field was left unexplained. We combine in-situ field and particle observations, together with a physics-based coupled model, the Rice Convection Model (RCM) Coupled Thermosphere-Ionosphere-Plasmasphere-electrodynamics (CTIPe), to revisit the local time asymmetry of the equatorial electron intensity observed in the innermost radiation belt. The study is based on the dawn-dusk difference in equatorial electron intensity measured at L = 1.30 during the first 60 days of the year 2014. Analysis of measured equatorial electron intensity in the 150–400 keV energy range, in-situ DC electric field measurements and wind dynamo modeling outputs provide consistent estimates of the order of 6–8 kV for the average dawn-to-dusk electric potential variation. This suggests that the dynamo electric fields produced by tidal motion of upper atmospheric winds flowing across Earth’s magnetic field lines - the quiet time ionospheric wind dynamo - are the main drivers of the drift shell distortion in the Earth’s inner radiation belt.