CONCERNING THE LOCATION OF MAGNETOPAUSE MERGING AS A FUNCTION OF THE MAGNETOPAUSE CURRENT STRENGTH

We start from an assumption that merging occurs in regions of the magn etopause where current strengths are greater than some threshold value which corresponds to the total jump in the field across the magnetopa use greater than 50 nT. Because time and cost constraints preclude run ning numerical simulations for a wide variety of interplanetary magnet ic field (IMF) orientations to determine these locations, we adopt an analytical model based on previously derived formulations for magnetos pheric and magnetosheath magnetic fields. The magnetospheric magnetic field is confined within a paraboloid. The magnetosheath magnetic fiel d is derived from that in the solar wind and lies between the magnetop ause and a paraboloid bow shock. We allow a slight diffusion of the ma gnetosheath magnetic field into the magnetosphere, The results of the model Show that during periods of due southward IMF orientation, mergi ng occurs (as expected) in a wide region centered on the subsolar magn etopause. During periods of northward IMF, connection continues near t he subsolar point but also poleward of the cusps. Magnetic energy is o nly released to the plasma in the latter regions. During periods of st rongly northward IMF (B-y = 0), reconnection ceases on the subsolar ma gnetopause but continues poleward of the cusp. If the IMF points north ward but By is nonzero, reconnection continues near the subsolar point and poleward of the cusps. During periods of sunward IMF orientation, merging nearly ceases on the northern hemisphere (except in the vicin ity of the subsolar point) but continues outside the southern lobes. D awnward and duskward IMF orientations produce tilted patches of enhanc ed current densities in the subsolar region. We compare the results of our model with previous predictions of the ''component'' and ''antipa rallel'' merging models.