Browsing by Author "Sazykin, S."

Now showing 1 - 4 of 4
  • Thumbnail Image
    Item
    Erosion of the plasmasphere during a storm
    (Wiley, 2017) Krall, J.; Huba, J.D.; Sazykin, S.
    The erosion of the plasmasphere during a storm is analyzed using the Naval Research Laboratory Sami3 is Also a Model of the Ionosphere ionosphere/plasmasphere code, coupled to the Rice Convection Model of the inner magnetosphere and ring current. We reproduce the commonly observed poststorm plasmasphere profile, with strong erosion outside of a sharp, poststorm plasmapause, and weak erosion inside the plasmapause. We find that inclusion of the ring current E field sharpens the poststorm plasmapause. In the case of a weak storm, erosion inside the poststorm plasmapause might not occur. In all cases, plasma flows are dominated by E × B drifts. For strong storms, we find that erosion, both inside and outside of the poststorm plasmapause, is caused by outward E × B drifts.
  • Thumbnail Image
    Item
    Large-scale current systems and ground magnetic disturbance during deep substorm injections
    (American Geophysical Union, 2012) Yang, J.; Toffoletto, F.R.; Wolf, R.A.; Sazykin, S.; Ontiveros, P.A.; Weygand, J.M.
    We present a detailed analysis of the large-scale current systems and their effects on the ground magnetic field disturbance for an idealized substorm event simulated with the equilibrium version of the Rice Convection Model. The objective of this study is to evaluate how well the bubble-injection picture can account for some classic features of the substorm expansion phase. The entropy depletion inside the bubble is intentionally designed to be so severe that it can penetrate deep into geosynchronous orbit. The results are summarized as follows: (1) Both the region-1-sense and region-2-sense field-aligned currents (FACs) intensify substantially. The former resembles the substorm current wedge and flows along the eastern and western edges of the bubble. The latter is connected to the enhanced partial ring current in the magnetosphere associated with a dipolarization front earthward of the bubble. In the ionosphere, these two pairs of FACs are mostly interconnected via Pedersen currents. (2) The horizontal ionospheric currents show a significant westward electrojet peaked at the equatorward edge of the footprint of the bubble. The estimated ground magnetic disturbance is consistent with the typical features at various locations relative to the center of the westward electrojet. (3) A prominent Harang-reversal-like boundary is seen in both ground DH disturbance and plasma flow pattern, appearing in the westward portion of the equatorward edge of the bubble footprint, with a latitudinal extent of 5 and a longitudinal extent of the half width of the bubble. (4) The dramatic dipolarization inside the bubble causes the ionospheric map of the inner plasma sheet to exhibit a bulge-like structure, which may be related to auroral poleward expansion. (5) The remarkable appearance of the westward electrojet, Harang-reversal-like boundary and poleward expansion starts when the bubble reaches the magnetic transition region from tail-like to dipole-like configuration. We also estimate the horizontal and vertical currents using magnetograms at tens of ground stations for a deep injection substorm event occurred on April 9, 2008, resulting in a picture that is qualitatively consistent with the simulation. Based on the simulations and the observations, an overall picture of the ionospheric dynamics and its magnetospheric drivers during deep bubble injections is obtained.
  • Thumbnail Image
    Item
    Recent Developments in Our Knowledge of Inner Magnetosphere‐Ionosphere Convection
    (Wiley, 2018) Kunduri, B.S.R.; Baker, J.B.H.; Ruohoniemi, J.M.; Sazykin, S.; Oksavik, K.; Maimaiti, M.; Chi, P.J.; Engebretson, M.J.
    Plasma convection in the coupled inner magnetosphere‐ionosphere is influenced by different factors such as neutral winds, penetration electric fields, and polarization electric fields. Several crucial insights about the dynamics in the region have been derived by interpreting observations in conjunction with numerical simulations, and recent expansion in ground‐ and space‐based measurements in the region along with improvements in theoretical modeling has fueled renewed interest in the subject. In this paper we present a comprehensive review of the literature with an emphasis on studies since 2012 relevant to the National Science Foundation Geospace Environment Modeling program. We cover four specific areas: (1) the subauroral polarization stream, (2) penetration electric fields, (3) the disturbance dynamo, and (4) quiet time subauroral convection. We summarize new observations and resulting insights relevant to each of these topics and discuss various outstanding issues and unanswered questions.
  • Thumbnail Image
    Item
    Storm time ionosphere and plasmasphere structuring: SAMI3-RCM simulation of the 31 March 2001 geomagnetic storm
    (American Geophysical Union, 2014) Huba, J.D.; Sazykin, S.
    We present the first self-consistent modeling study of the ionosphere-plasmasphere system response to a geomagnetic storm. We use the coupled SAMI3-Rice Convention Model (RCM) of the global ionosphere and inner magnetosphere, with self-consistent electrodynamics, to simulate the 31 March 2001 magnetic storm. We find that the penetration electric fields associated with the magnetic storm lead to a storm time-enhanced density (SED) in the low- to middle-latitude ionosphere and that the separation in latitude of the Appleton anomaly peaks increases. The SED exhibits magnetic conjugacy, occurring in both the Northern and Southern Hemispheres. Moreover, mapping the boundary of the SED into the equatorial plane coincides with the development of a ﾓplume-likeﾔ structure in the plasmasphere. These preliminary results are consistent with observations.