Magnetopause rotational forms

Abstract

Magnetic field data from the Goddard Space Flight Center magnetometer experiment on board Ogo 5 are analyzed by the minimum variance technique for two magnetopause crossings, believed to provide the best evidence presently available of magnetopause rotational discontinuities. Approximate agreement with predictions from MHD and first‐order orbit theory is found, but available low‐energy electron data suggest the presence of significant non‐MHD effects. The paper also illustrates an improved method for data interval selection, a new magnetopause hodogram representation, and the utility of data simulation.

Waves in the Vicinity of the Magnetopause

“…Although careful searches have revealed a few examples of such normal components (Sonnerup, 1971;Sonnerup and Ledley, 1974), c is clear (see also Aubry 1971;Ledley, 1971) that any identifiable normal component is small or larking most of the time.…”

“…Fairfield, 1971) and there is a growing body of evidence in support of the Kelvin-Helmholtz instability (e.g. Dungey and Southwood, 1970;Ledley, 1971;Aubry et al 1971;Wolfe and Kaufmann, 1975 (Aubry et al 1971;Ogilvie et al 1971;Neugebauer et al, 1974;Sonnerup and Ledley, 1974) and the presence of waves near the proton gyrofrequency has been only briefly noted.…”

Properties of standing Kruskal-Schwarzschild-modes at the magnetopause

“…Usually, in the absence of reconnection, it can be treated as a tangential discontinuity, across which hardly any normal flow of plasma takes place (Sonnerup and Cahill, 1967;Sonnerup and Ledley, 1974). Although most of the plasma parameters change across the boundary (for instance direction and strength of the magnetic field, particle densities and temperatures), the magnetopause is characterized by an equilibrium of the total pressure (Paschmann et al, 1993;Phan and Paschmann, 1996): On the magnetosheath side the thermal and magnetic pressures may be of similar importance; they are balanced by the dominant magnetic pressure on the magnetospheric side where, nevertheless, the thermal pressure may also be non-negligible.…”

Structure of the magnetopause: Observations and implications for reconnection

“…This conclusion is reached by using techtriqucs which do not require estimates of boundary motions and it is consistent with the more numerous studies which must use t hest , more uncertain estimates. The frequvntIy cited number of a 100 km thermal gyroradius In n strict M111) rotational discontinuity the total field strength does not change across the discontinuity, but Sonnerup and ]b Ledley (1974) have introduced tilt-term "rotational form" to extend tit.…”

“…Sonnerup and Ledley (1974) present their two best examples of rotational forms which they extracted from a set of 50 crossings. A further study of the hotindary of the entr y laver (Fairfield and Hanes, 1978) utilized more rapidly sampled data from tier IMI'-h spacecraft.…”