Showing papers by "Stanley W. H. Cowley published in 1984"

A survey of dayside flux transfer events observed by ISEE 1 and 2 magnetometers

Abstract: Flux transfer events (FTEs), observed on both the interior and exterior of the dayside magnetopause region by the ISEE 1 and 2 spacecraft, are noted to be a feature of the magnetopause region covered by the spacecraft when the magnetic field in the magnetosheath has a southward component, but not when it is northward. During periods of southward magnetosheath field, the average number and recurrence time of FTE signatures/magnetopause crossing are similar to those observed in the magnetopause interior, implying that the magnetosheath and magnetosphere FTEs are aspects of the same physical phenomenon. It is speculated that FTEs may provide the dominant means of flux transfer required for the driving of geomagnetic disturbances.

Magnetospheric flux erosion events are flux transfer events

Abstract: Recent results have shown that magnetic reconnection at the Earth's dayside magnetopause manifests itself most frequently as an impulsive process. Haerendel et al.1, using data from the HEOS 2 spacecraft, were the first to notice short time scale magnetic field perturbations inside the magnetopause, which they interpreted as flux erosion events resulting from transient reconnection in the polar cusp regions. Using higher time resolution data from the ISEE 1 and 2 satellite pair, Russell and Elphic2 subsequently discovered certain characteristic magnetic field signatures in the magnetosheath, which they termed flux transfer events (FTEs). They also interpreted these events in terms of transient, localized reconnection. It has often been suggested3–7 that Haerendel et al.'s flux erosion events and Russell and Elphic's FTEs have a close physical connection, but proof of this has so far been lacking. Here we show that flux erosion events and flux transfer events are indeed the same physical phenomenon.

Acceleration of lithium test ions in the quiet time geomagnetic tail

Abstract: One of the active experiments to be performed as part of the Active Magnetospheric Particle Tracer Explorers mission involves the release of lithium ions in the geomagnetic tail and their subsequent detection after earthward convection into the nightside outer ring current region. In this paper we have used the guiding center approximation to integrate ion trajectories in a simple two-dimensional model of the quiet time nightside magnetosphere in order to estimate expected ion properties at the latter location. Our principal conclusion is that under typical quiet time conditions these ions will predominantly form a field-aligned beam (∼5°–20° pitch angle) at energies from a few hundred eV to ∼1 keV.

Evidence for the heating of thermal electrons at the magnetopause boundary layer

Abstract: The suprathermal plasma analyser on the geostationary satellite Geos-2 can identify magnetospheric, boundary layer and magnetosheath electron distributions around the dayside equatorial magnetopause. As examples, data from two days when magnetopause crossings occurred, 28 August 1978 and 12 November 1978, are discussed. The boundary layer electrons are intermediate in temperature and density between those in the ring current and the magnetosheath but cannot be a simple admixture of the two populations. The transition from boundary layer to magnetosheath electrons is often sudden. We believe it to be coincident with the magnetopause where the magnetic field changes from terrestrial to interplanetary.