Comment on Lockwood and Davis, ”On the longitudinal extent of magnetopause reconnection pulses”

Lockwood and Davis (1996) present a concise description of magnetopause reconnection pulses, with the claimed support of three types of observations: (1) ̄ux transfer events (FTE), (2) poleward-moving auroral forms on the dayside, and (3) steps in cusp ion dispersion characteristics. However, there are a number of errors and misconceptions in the paper that make their conclusions untenable. They do not properly take account of the fact that the relevant processes operate in the presence of a plasma. They fail to notice that the source of energy (a dynamo with E J < 0) must be close to the region of dissipation (the electrical load with E J > 0) in transient phenomena, since energy (or information) cannot travel faster than the group velocity of waves in the medium (here the Alfve n velocity VA). In short, Lockwood and Davis use the wrong contour in their attempt to evaluate the electromotive force (emf). This criticism goes beyond their article: a dynamo is not included in the usual de®nition of reconnection, only the reconnection load. Without an explicit source of energy in the assumed model, the idea of magnetic reconnection is improperly posed. Recent research has carried out a superposed epoch analysis of conditions near the dayside magnetopause and has found the dynamo and the load, both within the magnetopause current sheet. Since the magnetopause current is from dawn to dusk, the sign of E J re ̄ects the sign of the electric ®eld. The electric ®eld reverses, within the magnetopause; this can be discovered by an application of Lenz's law using the concept of erosion of the magnetopause. The net result is plasma transfer across the magnetopause to feed the low latitude boundary layer, at least partly on closed ®eld lines, and viscous interaction as the mechanism by which solar wind plasma couples to the magnetosphere. Introduction Lockwood and Davis (1996; hereafter denoted by LD) present a concise description of magnetopause reconnection pulses, with the claimed support of three types of observations: (1) ̄ux transfer events (FTE), a concept introduced by Russell and Elphic (1978); (2) polewardmoving auroral forms on the dayside, ®rst investigated in detail by Sandholt et al. (1986); and (3) steps in cusp ion dispersion characteristics, which are common in low altitude satellite observations of the dayside cusp (e.g. Woch and Lundin, 1992). However, there are a number of errors and misconceptions in the paper that make their conclusions untenable. They do not properly take account of the fact that the relevant processes operate in the presence of a plasma. Furthermore, it is dicult to check causality of their envisioned process.