Magnetosheath Boundary Research Articles

Magnetospheric plasma discontinuity by the geostationary version of the differential phase method during storms

It is shown that the dynamics of the plasmapause, the plasmasphere plasma tails, the plasma sheet and the magnetosheath boundaries of the geomagnetosphere may be investigated by means of the geostationary version of the differential phase method, by which a signal transmitted from a sounding station (a geostationary satellite) and received by a response station on the Earth may be transformed, allowing the sign of the frequency shift and of the phase lag to be changed. Information on the location, the motion of the magnetospheric plasma discontinuities and the concentration drop at their boundaries may be obtained from measurements carried out on board the geostationary satellite of the phase difference of the sounding and response signals ΔΦ, the time of its increase Δt and the phase difference change rate (fast beating frequency Δƒ = ΔΦ 2π Δt ) . The establishment of communication between appropriately spaced ground stations and a satellite with a quasi-polar orbit allows the midlatitude plasmapause dynamics, and those of the ionosphere trough, polar cusp boundaries and of polar cap inhomogeneities to be studied. Equipment with a stability of 10 −11–10 −12 is needed for the most dynamical events (for ΔΦ= 10 −4 tens of rad. and for Δƒ= 10 −5 tens of Hz) occurring in the radio path during storms.

Magnetodynamically induced ambiguity in the data from tilted, spinning fluxgate magnetometers: Possible application to IMP 1

Data from a satellite-borne, tilted, spinning fluxgate magnetometer are subject to inherent ambiguities when the sampled ambient field is dynamically active. These ambiguities are further compounded when the sampling is multirate. In this paper, the intrinsic limitations of a multirate-sampled, tilted fluxgate system are described, the production of false ambient vectors is explained, and the conditions for extracting desired physical quantities, such as field magnitudes and power spectra, are discussed. The results are applied to the Explorer 18 (IMP 1) magnetometer system in the magnetosheath, and it is shown that the ambiguities of the system may in fact limit the interpretability of the Explorer 18 data in some parts of this region or in other regions of magnetic activity. The paper discusses the relevance of dynamic field effects to magnetosheath boundary determinations, to the interpretations of Explorer 18's magnetosheath data as ‘turbulent’ fields, and to the apparent differences between Explorer 18's magnetosheath measurements and those obtained by magnetometers aboard other spacecraft such as Pioneer 1, OGO 1, and Vela 3.