On the influence of localized electric fields and fieldaligned currents associated with polar arcs on the global potential distribution
Abstract
The influence of localized fieldaligned current, associated with intense transpolar arcs mostly occurring during periods of northward interplaentary magnetic field (IMF), on the global electrodynamics has been investigated using a numerical simulation model. Idealized fieldaligned current distributions representing both the region 1/2 system of the auroral oval and the transpolar arc as well as a corresponding ionospheric conductivity distribution are fed into the model to calculate the potential distributions. The transpolar arc has been represented by a few alternative fieldaligned current distributions which are different in the way the downward return currents are distributed in the ionosphere. If the conductivity of the main auroral oval is comparable to that of the polar arc the dusk cell will have two local potential minima and thus a region of weak antisunward convection in between. Depending on the direction of the polar arc current sheets the dawndusk electric field will either be reversed (or weakened) or intensified at the location of the transpolar arc. The presence of a reversal depend, however, not only on the relative magnitude between the polar arc current sand those of the region 1/2 system but also on the characteristics of the acceleration region and of the conductivity distributionmore »
 Authors:
 (Royal Inst. of Tech., Stockholm (Sweden))
 Publication Date:
 OSTI Identifier:
 5255923
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Geophysical Research; (United States); Journal Volume: 96:A8
 Country of Publication:
 United States
 Language:
 English
 Subject:
 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; POLARCAP AURORAE; ELECTRODYNAMICS; AURORAL OVAL; ELECTRIC CONDUCTIVITY; ELECTRIC CURRENTS; INTERACTIONS; INTERPLANETARY MAGNETIC FIELDS; MAGNETIC BAYS; MATHEMATICAL MODELS; MORPHOLOGY; SOLAR WIND; AURORAE; CURRENTS; ELECTRICAL PROPERTIES; MAGNETIC FIELDS; PHYSICAL PROPERTIES; SOLAR ACTIVITY; 640201*  Atmospheric Physics Auroral, Ionospheric, & Magetospheric Phenomena
Citation Formats
Marklund, G.T., and Blomberg, L.G. On the influence of localized electric fields and fieldaligned currents associated with polar arcs on the global potential distribution. United States: N. p., 1991.
Web. doi:10.1029/91JA01120.
Marklund, G.T., & Blomberg, L.G. On the influence of localized electric fields and fieldaligned currents associated with polar arcs on the global potential distribution. United States. doi:10.1029/91JA01120.
Marklund, G.T., and Blomberg, L.G. 1991.
"On the influence of localized electric fields and fieldaligned currents associated with polar arcs on the global potential distribution". United States.
doi:10.1029/91JA01120.
@article{osti_5255923,
title = {On the influence of localized electric fields and fieldaligned currents associated with polar arcs on the global potential distribution},
author = {Marklund, G.T. and Blomberg, L.G.},
abstractNote = {The influence of localized fieldaligned current, associated with intense transpolar arcs mostly occurring during periods of northward interplaentary magnetic field (IMF), on the global electrodynamics has been investigated using a numerical simulation model. Idealized fieldaligned current distributions representing both the region 1/2 system of the auroral oval and the transpolar arc as well as a corresponding ionospheric conductivity distribution are fed into the model to calculate the potential distributions. The transpolar arc has been represented by a few alternative fieldaligned current distributions which are different in the way the downward return currents are distributed in the ionosphere. If the conductivity of the main auroral oval is comparable to that of the polar arc the dusk cell will have two local potential minima and thus a region of weak antisunward convection in between. Depending on the direction of the polar arc current sheets the dawndusk electric field will either be reversed (or weakened) or intensified at the location of the transpolar arc. The presence of a reversal depend, however, not only on the relative magnitude between the polar arc current sand those of the region 1/2 system but also on the characteristics of the acceleration region and of the conductivity distribution associated with the polar arc. Comparisons are made between the model results and Viking electric field data for a number of polar arc crossings to reveal the most common electrodynamical signatures of these auroral phenomena.},
doi = {10.1029/91JA01120},
journal = {Journal of Geophysical Research; (United States)},
number = ,
volume = 96:A8,
place = {United States},
year = 1991,
month = 8
}

The comparison of the distribution of fieldaligned currents and ionospheric currents on a very quiet day and a moderately disturbed day, obtained on the basis of the International Magnetosphere Study Alaska meridian chain of magnetometers, reveals that the fieldaligned currents (region I and II currents) consist of two systems: the part I system in the dayside and the part II system in the nightside. On a very quiet day the part II system is either absent or very weak. On the other hand, on a moderately disturbed day the part II system becomes a dominant feature. It is also shownmore »

Polar cap fieldaligned currents for southward interplanetary magnetic fields
It has been common to suppose that polar region fieldaligned currents for southward interplanetary magnetic fields (IMF) consist of two parts: region 1 and region 2 currents. It is often suggested that both of these current systems flow on closed field lines. In this pilot study the limited data available from the ISIS 2 satellite are used to examine region 1 currents with the objective of establishing whether or not they can exist partially on open field lines (i.e., inside the polar caps) for southward IMF. Magnetic field perturbations were used to identify the fieldaligned currents (FACs). The absence ofmore » 
Simulation studies of ionospheric electric fields and currents in relation to fieldaligned currents 1. Quiet periods
Computer simulation studies of the electric fields and currents in the global ionosphere produced by fieldaligned electric currents for quiet periods are conducted. The steady state equations for current conservation are solved numerically by assuming (1) several divided regions of the global earth (such as the polar cap, auroral zone, and middlelow latitudes), (2) exponentially distributed anisotropic electric conductivities for each zone with a continuous change at the boundaries of the regions, and (3) exponentially distributed downward and upward fieldaligned current intensities in the auroral region, assumptions based on our current knowledge of auroral phenomena and geomagnetic variations as wellmore » 
Simulation studies of ionospheric electric fields and currents in relation to fieldaligned currents 2. Substorms
The computer simulation scheme for calculating the electric fields and currents in the global ionosphere in relation to fieldaligned currents for quiet periods that we previously developed is extended to disturbed conditions. In a series of numerical simulations representing various substorms we take into account our current knowledge of characteristics of auroral enhancement in the ionospheric electric conductivities as well as changes in the intensity and location of fieldaligned currents. The possible effects of these variable parameters in producing the observed complexity of the electric field and current patterns are studied, with the following main results: The conductivity inhomogeneity inmore »