Polar cap electric field dependence on solar wind and magnetotail parameters

Abstract

A magnetic field model with a linearly superposed uniform external field is used to study the effects of the magnetotail field intensity BT on the relationship between the convection pattern in the polar cap and the interplanetary magnetic field (IMF). It is found that as BT increases, the polar cap size increases, the overall electric field intensity decreases, and the dependence of the total "open" flux on the magnitude and direction of the IMF weakens. In addition, the tail field introduces significant differences between the convection patterns corresponding to "toward" and "away" IMF sectors, respectively: in the northern (southern) polar cap, features such as polar cap boundary displacements and electric field intensity gradients are more pronounced when the earth is in an "away" ("toward") sector. On the other hand, in the case of a northward‐tilted IMF, sunward convection in the north (south) polar cap is extended over a larger area for a "toward" ("away") sector. Since dipole tilt was not taken into account in the model, these results should mainly apply to periods around equinox.

Solar wind energy transfer through the magnetopause of an open magnetosphere

“…The tail magnetopause can be divided into two regions ( The open flux (18) can be calculated by using quantitative models of the magnetospheric field. Several authors have studied reconnection geometries; all assume a uniform interplanetary magnetic field linearly superposed to a magnetospheric model field [Stern, 1973;Saunders, 1976;Voigt and Fuchs, 1979;Akasofu and Ahn, 1980;Longenecker and Roederer, 1981]. In particular, Akasofu and Ahn [1980] found that, approximately, 6---Bsw sin (0/2), which, according to (18), corresponds to a = « and G(0) = sin (0/2).…”

“…On the other hand, Longenecker and Roederer [1981] used the well-tested Hones-Taylor model with a superposed interplanetary field. With the cross-tail current adjusted to the latter as is experimentally observed, they find that 6 oc Bsw 2/3 sin (0/2), corresponding to a = • in (18).…”