Epoch‐Based Model for Stormtime Plasmapause Location

• Published in: Journal of geophysical research. Space physics 2019-06, Vol.124 (6), p.4462-4491
• Main Authors: Goldstein, J., Pascuale, S., Kurth, W. S.
• Format: Article
• Language: English
• Subjects: Basis functions; Computer simulation; Electric fields; epoch‐based model; Evolution; Mathematical models; Plasmapause; plasmasphere; plume; Solar wind; Storms
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2018JA025996

The output of a plasmapause test particle (PTP) code is used to formulate a new epoch‐based plasmapause model. The PTP simulation is run for an ensemble of 60 storms spanning 3 September 2012 to 28 September 2017 and having peak Dst of −60 nT or less, yielding over 7 million model plasmapause locations. Events are automatically identified and epoch times calculated relative to the respective storm peaks. Epoch analysis of the simulated plasmapause is demonstrated to be an effective method to reveal the dynamical phases of plume formation and evolution. The plasmapause radius is found to be strongly correlated with positive solar wind electric field. The epoch‐binned PTP data are used to create the first analytical model of the plasmapause that explicitly includes plumes. We obtain this result by employing as basis functions our derived exact solutions for the Volland‐Stern convection potential. The analytical plasmapause model depends on epoch time, for moderate and strong storms, and is specified by three main parameters: the duskside plasmapause radius and two tuning coefficients. The epoch‐based analytical model is shown to agree to within 0.5 RE with nightside in situ plasmapause crossings by the Van Allen Probes on 17 March 2015. Compared to dayside plume crossings on 26 June 2000, the model agrees within 0.7 RE of radius and 0.8 RE azimuthal distance. This level of agreement is comparable to that achieved by the full dynamic PTP simulation. Key Points Epoch analysis of simulated plasmapause is an effective method to reveal plume dynamics (phases) under influence of convection First analytical model of storm time plasmapause radius that explicitly includes plumes is obtained For two case studies, epoch‐based analytical model agrees with nightside plasmapause within 0.5 RE, with dayside plumes within 0.7 to 0.8 RE