Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 4 of 4
Full-Text Articles in Physics
Model Study Of Ionospheric Dynamics During A Substorm, Lie Zhu, Robert W. Schunk, Jan Josef Sojka, Michael David
Model Study Of Ionospheric Dynamics During A Substorm, Lie Zhu, Robert W. Schunk, Jan Josef Sojka, Michael David
All Physics Faculty Publications
A global substorm electrodynamic model and a global ionospheric model were coupled in order to study ionospheric dynamics during substorms, with the focus on small-scale substorm electrodynamic and plasma structures. The simulation results show that in the expansion phase, structured precipitation and channeled field-aligned currents quickly develop in the substorm onset region. The Hall and Pedersen conductance ratio in the region increases significantly, and the magnetospheric field-aligned currents are mainly closed by highly structured Hall currents. Correspondingly, the plasma in the ionosphere also undergoes significant changes during a substorm and is highly structured in both the horizontal and vertical directions. …
Model Study Of Ground Magnetic Signatures Of Traveling Convection Vortices, Lie Zhu, P. Gifford, Jan Josef Sojka, Robert W. Schunk
Model Study Of Ground Magnetic Signatures Of Traveling Convection Vortices, Lie Zhu, P. Gifford, Jan Josef Sojka, Robert W. Schunk
All Physics Faculty Publications
We conducted a model study of ground magnetic signatures of traveling convection vortices (TCVs) that included both the ionospheric conductivity enhancement associated with the TCVs and the ground induction effect. We found that the localized conductivity enhancement can cause a significant distortion of the TCV current system and lead to a distortion of the ground magnetic disturbance patterns. The patterns of all three magnetic components are asymmetric, mainly in the E-W direction, and the patterns of the Z component show the strongest asymmetry (20–30%). We also found that the effect of induction currents on ground magnetic signatures of the TCVs …
Model Study Of Multiple Polar Cap Arcs: Occurrence And Spacing, Lie Zhu, Jan Josef Sojka, Robert W. Schunk, D. J. Crain
Model Study Of Multiple Polar Cap Arcs: Occurrence And Spacing, Lie Zhu, Jan Josef Sojka, Robert W. Schunk, D. J. Crain
All Physics Faculty Publications
A new scenario for the formation of multiple polar cap arcs is proposed based on the results from a time‐dependent electrodynamic model of polar cap arcs developed by Zhu et al. [1993]. The results suggest that the appearance of multiple polar cap arcs may not be due to multiple structures in the magnetospheric source region, but instead, may primarily be determined by the coupled magnetosphere‐ionosphere system in which the ionosphere plays an active role. It was found that with the same magnetospheric driver, a strong ionospheric background convection and an ionospheric background Hall conductance in the range of from 0.5 …
A Model Study Of How Electric Field Structures Affect The Polar Cap F Region, Jan Josef Sojka, Robert W. Schunk
A Model Study Of How Electric Field Structures Affect The Polar Cap F Region, Jan Josef Sojka, Robert W. Schunk
All Physics Faculty Publications
A three-dimensional time-dependent ionospheric model was used to study how electric field structures affect the polar F region. The electric field structures are represented by elongated Volland two-cell models whose dimensions range from tens to 1000 km. These model structures are intended to represent the polar cap electric field for IMF Bz northward conditions. A statistical method is used to generate a set of these structures. Their electric field strength and polarity are varied in order to study the F region’s dependence on this magnetospheric input. For electric field structures whose size and electric field strengths are consistent with …