Time-dependent hydrodynamic equations were solved in order to study the refilling of plasmaspheric flux tubes depleted during magnetic storms. Depending on the initial density profiles in the depleted flux tube, a variety of shock formations occur during the early stage (•-1 hour) of the refilling. After this early stage, an important feature of the flow is the formation of a pair of shocks, which propagate down, one in each hemisphere. The refilling occurs by the downward propagating shocks with speeds • 1.5 km/s and by a simultaneous increase in the plasma density between the two shocks. The time rates of this increase in the density are given for magnetic shells L = 4 and 6.6. These rates depend on the density (No) at the ionospheric boundaries. Depending on No, a fair agreement is found between the refilling rates obtained from our calculations for L = 6.6 and those determined from the GEOS 2 observations. The refilling of a flux tube with different densities in the conjugate ionospheres was also considered, and it was found that after the initial stage of about one hour, the filling occurs through the propagation of only one shock from the hemisphere of the weak ionospheric source to that of the strong one. An interesting feature of the temporal evolution of the density of the shocked plasma after the early stage is the persistence of fluctuations with time periods ranging from about 2 to 10 minutes and corresponding wavelengths ranging from about one to several thousand kilometers. These fluctuations appear to be sound waves. Prior to the shock formation, counterstreaming of the ions is expected to occur in the equatorial region. The single-fluid hydrodynamic model used in the present study is not suited to handle such multiple plasma streams. Therefore, some kinetic considerations for the formation of shocks are given. ResUlts from the particle simulations of counterstreaming plasma expansion show that a potential hill, which eventually slows down the ion streams, leads to the formation of a shock pair in the "equatorial plane." These shocks propagate in opposite directions in a manner analogous to that obtained with the hydrodynamic model of a geomagnetic flux tube. However, the kinetic calculations show that the shock formation occurs only when the electron temperature Te • 3 T/, where T/is the ion temperature. tions become valid. Banks et aL [ 1971] estimated that for the L = 5 flux tube the transition from supersonic to subsonic flow should occur about 22 hours after the filling process began. Schulz and Koons [1972] studied the stability of counter-streaming ion flows using a one-dimensional analysis based on the ion acoustic mode. They concluded that electrostatic shocks were not likely to form at the equator, but that ion trapping could occur via wave-particle interactions. Specifically, they predicted that the interaction between the ion streams occurs via an electrostatic instability until the equatorial density reaches about 20 cm -3. The electrostatic waves induce weak pitch angle : diffusion su...

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Electron density and temperature profiles in the mid latitude ionosphere are derived from the ”resonance cone” in the radiation pattern of high‐frequency point antennas aboard a sounding rocket. By comparing the shapes for reversed wave propagation direction it is possible to study electron drift motion and field‐aligned beams. The data from the COREX‐I (Cooperative Resonance Cone Experiment) experiment show close agreement of electron density and temperature profiles from resonance cones with results from independent instruments. There was no indication of a substantial temperature anomaly at E region altitude during this flight. An unexpected electron drift can be interpreted as electron Hall current in the presheath of the negatively charged payload. Field‐aligned beams, which have been suggested in connection with the temperature anomaly, were not detected.

Strong electrostatic double layers were produced with a triple plasma configuration in the large plasma chamber (5 m long, 2·5 m diameter) at IPM in Freiburg, Federal Republic of Germany. Owing to relatively low densities (1011 1012m−3), Debye lengths of a few centimetres and layer thicknesses of the order of a metre were obtained. Layers both with and without magnetic fields were studied. Analysis of particle spectra prove that wave-particle interactions play a minor role in maintaining the strong electric field. The three-dimensional potential distribution is measured and is qualitatively discussed in terms of particle budget. For cases with a magnetic field it tends to agree with observations above the aurora. Comparisons are made with double-layer theory and computer experiments, and general agreement is found as far as the available results allow.

Various mechanisms for driving double layers in plasmas are briefly described, including applied potential drops, currents, contact potentials, and plasma expansions. Some dynamical features of the double layers are discussed. These features, as seen in simulations, laboratory experiments, and theory, indicate that double layers and the currents through them undergo slow oscillations which are determined by the ion transit time across an effective length of the system in which the double layers form. It is shown that a localized potential dip forms at the low potential end of a double layer, which interrupts the electron current through it according to the Langmuir criterion, whenever the ion flux into the double is disrupted. The generation of electric fields perpendicular to the ambient magnetic field by contact potentials is also discussed. Two different situations have been considered; in one, a low-density hot plasma is sandwiched between high-density cold plasmas, while in the other a high-density current sheet permeates a low-density background plasma. Perpendicular electric fields develop near the contact surfaces. In the case of the current sheet, the creation of parallel electric fields and the formation of double layers are also discussed when the current sheet thickness is varied. Finally, the generation of electric fields (parallel to an ambient magnetic field) and double layers in an expanding plasmas is discussed.