The Conductance of Auroral Magnetic Field Lines
- Tom Chang,
- M. K. Hudson,
- J. R. Jasperse,
- R. G. Johnson,
- P. M. Kintner and
- M. Schulz
Published Online: 21 MAR 2013
Copyright 1986 by the American Geophysical Union.
Ion Acceleration in the Magnetosphere and Ionosphere
How to Cite
Weimer, D. R., Gurnett, D. A. and Goertz, C. K. (1986) The Conductance of Auroral Magnetic Field Lines, in Ion Acceleration in the Magnetosphere and Ionosphere (eds T. Chang, M. K. Hudson, J. R. Jasperse, R. G. Johnson, P. M. Kintner and M. Schulz), American Geophysical Union, Washington, D. C.. doi: 10.1029/GM038p0108
- Published Online: 21 MAR 2013
- Published Print: 1 JAN 1986
Print ISBN: 9780875900636
Online ISBN: 9781118664216
- Ion flow dynamics—Congresses;
- Space plasmas—Congresses
Recent results from the Dynamics Explorer satellites have indicated that in the auroral zone a linear relationship exists between the field aligned current density and the potential drop parallel to the magnetic field lines. Evidence for this “Ohm's law” relationship was found in the mapping of perpendicular electric fields and field-aligned currents between high and low altitudes. The mapping depends on the perpendicular wavelength of the electric field variations. A scale length in the mapping formula is determined by the ratio of the parallel field line conductance and the ionospheric Pedersen conductance. The wavelength and the conductivity ratio also control the relationship between the perpendicular electric and magnetic fields at high altitudes.
We show here that at the short-wavelength limit the ionospheric conductivity is no longer important in the relationship between the northsouth electric field and the east-west magnetic field at high altitudes (i.e., above the parallel potential drop). At the short-wavelength limit the relationship takes on a simple form: The integral of the perpendicular electric field results in a potential profile which, according to the linear theory, is proportional to the current density. Assuming that the currents are in the form of “infinite sheets” orientated eastwest, the second integral of the electric field is proportional to the magnetic field.
High time-resolution data from the DE-1 satellite are shown here for two events with very large electric fields which reversed directions within a short distance. The results agree very well with the linear theory. The field line conductance is determined to be of the order of 10−9 mho/m2. The samec onductancea ppearst o be valid for both upward and downward currents. Ions are accelerated from the ionosphere to magnetosphere by the potential drops in regions of upward current.