Ionospheric Conductivity Dependence of the Cross-Polar Cap Potential Difference and Global Joule Heating Rate.

摘要

Examine the extent to which the cross-polar cap potential difference psi and the global Joule heating rate U, both determined by the magnetogram - inversion method, depend upon the assumed conductance models. For this purpose two statistically determined conductance models and a realistic conductance distribution estimated from bremsstrah-lung X-ray image data have been used. As expected from earlier studies, U is less affected by the choice of conductance models than is psi. This is because U is a globally integrated quantity, and thus the local structures of the electric potential pattern do not affect it appreciably, whereas they are crucial in determining psi, which is defined as the difference between the maximum and minimum potential values usually found in the dawn and dusk sectors, respectively. A comparison between U and psi based on the statistical conductance models and U and psi based on a realistic conductance distribution shows that there are considerable similarities, thus enabling us to use statistical conductance models as a first approximation in deriving such global quantities as the cross-polar cap potential difference and the global Joule heating in the study of solar wind-magnetosphere coupling. Several suggestions are made for improving the present available conductance models and some limitations (possibly intrinsic ones) are also discussed. (jhd)