[en] Measurements of the drift velocity vector of themal O⁺ ions at high latitudes have revealed the existence of a significant component along the magnetic field lines. In this paper we report two observations: - a downward flow of O⁺ in the noon sector of the polar cap, - a reversal of the O⁺ flow along B from upward to downward apparently associated with changes in the structure and intensity of energetic electron precipitations. The first observation is in agreement with a model proposed by Whitteker (1977) to determine the ionospheric perturbations induced by soft particle precipitations. The second one also indicates that heating processes act with different time constants upon the vertical velocity and temperature of ionospheric ions

[en] Impulsive bursts of positive ions were observed in the polar cusp during two rocket flights. Dispersion of arrival time with energy implies a modulation or acceleration region at a distance of 11 to 13 Rsub(E), presumably in the magnetosheath. The ion energy spectra closely match typical magnetosheath spectra. The bursts had a duration of about 20s and repetition period on the order of 100s. These results suggest that ions have intermittent rather than continuous entry at the polar cusps. At times, the ion and electron precipitation was anticorrelated in a manner consistent with a parallel electric field. (Auth.)

No abstract available

[en] The production of ionospheric ionisation at night by auroral electrons and its height dependence are discussed. It is found that the altitude dependence of the effective recombination coefficient αsub(e) of the ions involved is of great importance in determining the ionisation profile produced by a given incident electron spectrum. Electron density profiles obtained in the auroral zone at night are examined for several nights during conditions of diffuse aurora. The incident electron spectra are computed from these measurements. (author)

[en] A number of case studies of large, transient, field-aligned ion flows in the topside ionosphere at high-latitudes have been reported, showing that these events occur during periods of frictional heating and/or intense particle precipitation. This study examines the frequency of occurrence of such events for the altitude range 200-500 km, based on 3 years of incoherent scatter data. Correlations of the upgoing ion flux at 400 km with ion and electron temperatures at lower altitudes are presented, together with a discussion of possible mechanisms for the production of such large flows. The influence of low-altitude electron precipitation on the production of these events is also considered. (author)

[en] Data obtained from a sounding rocket flight which reached an apogee of 927 km and passed through several auroral arcs are reported. During portions of the flight when the rocket was not in an energetic auroral structure, the ion data are fit to a Maxwellian function which yields the plasma parameters. Throughout the middle portion of the flight when above 700 km altitude, ion distributions having a superthermal tail were measured. These ion distributions generally coexisted with a cold thermal core distribution and peaked at pitch angles slightly greater than 90 degree, which identifies them as conic distributions. These ions can be modeled using a bi-Maxwellian distribution function with a perpendicular (to B) temperature about 10 times greater than the parallel temperature of 0.15 eV. When the rocket was immersed in energetic auroral electron precipitation, two other ion distributions were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed. Transversely accelerated ions which represented bulk heating of the ambient population were observed continuously in these arcs. The characteristic perpendicular energy of the transversely bulk heated ions reached as high as 3 eV compared to typically less than 0.4 eV during nonauroral times. Cold ions flowing down the magnetic field were also continuously observed when the rocket was immersed in auroral electron precipitation and had downward speeds between 3 and 5 km/s. If one balances electric and collisional forces, these speeds translate to an electric field pointing into the atmosphere of magnitude 0.01 mV/m. A close correlation between auroral electron precipitation, measured electrostatic oxygen cyclotron waves, cold downflowing ions and transversely bulk heated ions will be shown

[en] An ion trap having two end cap electrodes disposed asymmetrically about a center of a ring electrode is disclosed. The inner surface of the end cap electrodes are conformed to an asymmetric pair of equipotential lines of the harmonic formed by the application of voltages to the electrodes. The asymmetry of the end cap electrodes allows ejection of charged species through the closer of the two electrodes which in turn allows for simultaneously detecting anions and cations expelled from the ion trap through the use of two detectors charged with opposite polarity. 4 figs

[en] The injection of a barium plasma from a sounding rocket by the shaped charge technique offers several possibilities of application that cannot be achieved by conventional releases. They can be grouped into three classes: tracing at high altitudes; modifications; alternate ionization processes. Project Porcupine has contributed in several ways to these aspects. (Auth.)

[en] This report is the second phase of an attempt to find a unified description of auroral electric fields based on the interaction between a hot plasma and the Earth's magnetic field. It is shown that a large electrostatic potential difference must exist along the magnetic field lines under very general conditions, as a direct consequence of this interaction. This does not require 'anomalous resistivity' and is not a consequence of anisotropic pitch-angle distributions, but the electric field always produces anisotropy. In general, the electric field has a time-varying (unstable) spatial structure. An important source of temporal fluctuations is charge trapping in the combined electric and magnetic fields, which is an inevitable effect of scattering. A necessary condition for a stable electric field structure to form is that this trapping saturates. The conditions for this are most favourable in a thin 'double layer' structure, in particular one that is aligned along the magnetic field with |Esub(perpendicular to)|>>|Esub(parallel to)|. A secondary effect of charge trapping is a collimation of the electron precipitation flux. Another effect consists of increasing the transverse energy of cold ions (where |delsub(perpendicular to). E|>=|delsub(parallel to).E|). This effect is particularly strong for oxygen, resulting in a 'conical' pitch-angle distribution. (author)

No abstract available