[en] The measurement of auroral X-rays with balloon-borne instruments is an efficient way to study electrons with energies exceeding about 30 keV in the magnetosphere during disturbed periods. This paper discusses the perspectives for such measurements in the 1980's. Recently developed payloads are described that can be used as a basis for further technical developments and satellite projects scheduled for the 1980's are presented that are suited for coordinated X-ray measurements (these projects include EISCAT-SAT and OPEN)

[en] Metallic ions like Mg(+) and Fe(+) can be quite abundant at E region heights during meteor showers. Since their mass is significantly different from the mass of the normal E region ions like NO(+) and O2(+) the E region plasma will behave quite differently in the presence of these ions. As a consequence, the results of the dispersion relation of the modified two stream and the gradient drift plasma instability, occurring in the high latitude E region, are significantly different from the normal case. Some of these results are presented and the implications for the interpretation of auroral radar results (STARE) are discussed. 17 references

[en] Electrical currents, defined in terms of the net flux of charge transported by particles, deduced from the curl of the magnetic field in most of the observational work to date as well as in many theoretical contexts, are related to plasma dynamics both by the momentum equation and by the MHD connection between plasma flow and the magnetic field configuration (relations not easily representable by circuit analogies). The momentum equation provides directly an expression for the current density perpendicular to the magnetic field and, in combination with the current continuity equation, also provides an expression for the field-aligned gradient of the parallel (Birkeland) current density these expressions are here given with all inertial and pressure anisotropy effects taken into account. 15 references

[en] Measurements of the plasmaspheric electron content are reviewed with particular reference to the ATS-6 radio beacon experiment. From the review, it appears likely that measurement of the plasmaspheric electron content is the only one capable of monitoring electron fluxes continuously between L 1 and L 2. Some recent important results deduced from plasmaspheric electron content measurements are discussed

[en] The sun and the solar wind are considered in terms of the 'ballerina' model first proposed by Alfven (1977), taking into account high speed streams, the slow solar wind, stream-stream interactions, the relation of streams and magnetic structure, and transients caused by solar activity. The main features of the solar wind behavior are illustrated with the aid of data, covering one complete solar rotation in 1974/1975, which were obtained with instruments aboard the Helios-1 solar probe. It is pointed out that the solar wind acts like a huge buffer pushing onto the earth's magnetosphere with a highly variable pressure. Of the energy in the highly variable solar wind reservoir only a tiny fraction is absorbed by the magnetosphere in an obviously very nonstationary way

[en] Quasi-steady-state descriptions of local and global magnetic-field-line-reconnection phenomena are reviewed and illustrated with diagrams. Consideration is given to the bulk plasma flow and electric field in the region near the magnetic X line (separator), the time-variation-independent derivation of the electric field via Faraday's law, the existence of intermediate (macroscopic but local) length scales, the distribution of magnetic-field lines and flow streamlines on electric equipotential surfaces, the potential contours on a surface passing through the X lines, and the closing of the single X line of the open magnetosphere to form a ring with distinct dayside and nightside segments. 14 references

[en] The direct transfer of energy to cosmic rays from supersonic motions of the background medium via shock waves, by means of an efficient first order Fermi mechanism, is considered. The acceleration of cosmic rays by shock waves is most effective in the dilute and hot, 1,000,000-K component of the interstellar medium. There is no limit to the energy that can be achieved by shock acceleration, if enough time is available and the particles can be contained in the vicinity of the shock. The two basic first order Fermi mechanisms contributing to the overall process of shock acceleration of cosmic rays are reflection at, or transmission through, the magnetic field jump associated with the shock, and multiple reflection between the media upstream and downstream of the shock, due to the presence of waves that scatter the particles in pitch angle

[en] Reevaluation of the interplanetary meteoroid mass flux at 10 AU obtains a value of M of about 60,000 g/sec for the meteoroid mass loading rate to the rings of Saturn. This meteoroid impact flux suggests that a large change to the configuration of the ring system could occur in a relatively short time (less than about one million years). This new element thus should be taken into consideration in discussion of the dynamical evolution of the rings

[en] Geometrical considerations based on a conical sheet model of the observed DAM sources show that DAM is generated on field lines in the active longitude sector of 200 + or - 90 deg. The present study shows how Io excites Alfven waves and calculates the propagation of these waves through the inhomogeneous torus and magnetosphere. The power flux at high latitudes is largest at two longitudes which are seen as the B1, B2, A, and C sources. The parallel electric field accompanying the Alfven wave pulses is also discussed, and it is shown that at high latitudes electrons can be accelerated to energies in excess of 1000 eV. It is suggested that these current carrying electrons excite ion-cyclotron, upper and lower-hybrid electrostatic waves which may all play crucial roles in the generation of DAM

[en] The role of variations in the size distribution, optical depth, and surface composition of Saturnian ring material in the dynamics of production and recycling of dust particles in the whole ring system is examined. A simple Monte Carlo model incorporating the ballistic motion of small dust particles ejected by meteoroid impact as well as the inelastic collision of the ejected particles with the ring plane is presented. It is found that the redistribution of the ejected matter depends on the optical depth variation across the ring system and the initial ejection speed, and hence the scale length of random walk on the ring plane. For small values of the scale length, the ejecta would accumulate at positions of sharp change in optical depth. On the basis of this result, it is conjectured that the double-peaked feature observed for a number of narrow ringlets may be generated in this manner also. 20 references