A case study of the aurora, high‐latitude ionosphere, and particle precipitation during near‐steady state conditions

Abstract

An Isis 2 pass is singled out for a detailed examination of the particle fluxes, optical emissions, and ionospheric parameters observed during a quiescent period (late recovery) between two substorms. This pass was chosen because it was part of a coordinated data acquisition period between the Air Force Geophysics Laboratory (AFGL) Airborne Ionospheric Observatory, Isis 2, and DMSP (Defense Meteorological Satellite Program). As a result, both long‐duration measurements (aircraft) and transient, snapshot (spacecraft) data are available. This allows, on a macroscopic level, the separation of space and time effects. On the basis of the joint data set it was established that the latitudinal morphology observed by the satellite is basically spatial in nature. It is concluded that the observed particle fluxes are most easily understood in terms of precipitation from the quiet time plasma sheet without intervening acceleration. The observed optical emissions and ionospheric parameters are found to be in good qualitative and quantitative agreement (within experimental error) with the electron fluxes, although establishment of this point has required careful determination of the viewing direction of the optical instruments, removal of scattered light (albedo) from underlying cloud and snow, and consideration of the effects of photon‐counting statistics on contour plots of the optical data.

Ground and satellite observations of the evolution of growth phase auroral arcs

“…To summarize, before the beginning of a growth phase, FAST observations of electron fluxes associated with diffuse aurora (see Figure 14) agree with previous reports [ Deehr et al , 1976; Winningham et al , 1978; Meng et al , 1979] in that they typically show a broad energy peak, centered near ∼1 keV. Although solid evidence is lacking, a commonly proposed mechanism is that the electrons are scattered from the equatorial region via electron cyclotron harmonic waves.…”

A survey of electron cyclotron waves in the magnetosphere and the diffuse auroral electron precipitation

“…Paper number 88JA03715. 0148-0227/89/88JA-03715505.00 the evening sector precipitation have been published by Deehr et al [1976], Winningham et al [1978], and Meng et al [1979]. Observations on the morning side have been reported by Gustafsson [ 1973] and Lyons and Fennell [ 1986].…”

Relationships between auroral particle distributions and magnetic field perturbations associated with field‐aligned currents

“…This instrument measures the differential energy spectrum of both electrons and positive ions over an energy range from 5 eV to approximately 15 keV once each second. The instrument's field of view is normal to the spin axis, and, since the spacecraft is spinning with a period of 18 s, the full range of pitch angles is measured each 9 s. The SPS instrument and its data have been discussed extensively in previous publications [see Winningham et al, 1978]. Figure 2.…”