Ion Trough Research Articles

Field-line connection between scintillation and ionospheric conditions causing spreadE

Analysis of amplitude records of transmissions from satellites indicates that F-region irregularities causing scintillation and ionospheric conditions causing spread E are connected by the magnetic-field lines. The connection between spread E and scintillation can be explained by the E × B instability mechanism proposed by G. C. Reid (1968). Other evidence presented to support this hypothesis includes (1) the negative (positive) correlation between scintillation activity and magnetic activity south (north) of Jamaica, which is located in the vicinity of the Sq focus, and (2) the presence of spread E at the foot of ionization troughs caused by neutral winds.

Study of the thermal plasma on closed field lines outside the plasmasphere

Using OGO 4 ion composition measurements near the midlatitude light ion trough below 1000 km, a model for the plasma state along the magnetic field lines is developed which produces, in the equatorial plane, the sharp density gradient characteristic of the plasmapause. In this model the field aligned plasmasphere boundary is a boundary across which the characteristics of the proton flux along the field lines change. Within the plasmasphere the proton fluxes along the field lines are of small or vanishing magnitude and may be directed either away from or towards the Earth. By contrast, the small equatorial ion densities (∼1/cc) known to exist on closed field lines outside the plasmasphere are consistent with the measured low altitude densities only if large proton fluxes, of the order of the critical flux, are directed along the field lines. These latter fluxes are directed away from the Earth and correspond to the attainment of supersonic proton flow velocities on closed field lines outside the plasmasphere. This is consistent with the model of a supersonic polar wind convecting onto closed field lines.

Comparison of coincident OGO 3 and OGO 4 hydrogen ion composition measurements

Ion composition measurements made on August 8, 1967 and August 28, 1967 by the topside ionospheric polar orbiting satellite OGO 4 and simultaneously by the eccentric orbiting magnetospheric satellite OGO 3 were compared on nightside passes through the plasmasphere. Throughout most of the midlatitude regions sampled, an isothermal diffusive equilibrium model at an ion temperature of 1000°K provides a good approximation for coupling these ionospheric regions. However temperature gradient components directed upwards along the field lines of the order of 1°K/km or greater are required to bring the profiles into agreement near the plasma pause assuming diffusive equilibrium and assuming the magnitude of the temperature gradient does not vary along the field line. Similar gradients are also required along the low latitude field lines traversed on the August 28, 1967 passes. In agreement with previous studies of the average local time asymmetry of the plasmasphere boundary, the plasmapause L coordinates measured by OGO 3 near midnight were greater than the L coordinates associated with the light ion troughs observed near dawn on the coincident OGO 4 pass. In the steady state, if field line preservation is assumed and the convection stream-line pattern in the equatorial plane is known, the H + densities measured at different local times along the OGO 3 trajectory can be transformed into densities at a local time characteristic of the OGO 4 measurements so that the transformed OGO 3 plasma-pause is located on the same field line as the plasmapause determined from the OGO 4 measurements.

Ion depletion in the high-latitude exosphere; simultaneous OGO 2 observations of the light ion trough and the VLF cutoff

Ion depletion in high latitude exosphere, considering OGO 2 simultaneous observations of positive ion concentration, VLF signal propagation and whistlers