Low-energy proton interaction with interplanetary magnetohydrodynamic discontinuities

Low energy proton measurements associated with interplanetary MHD discontinuities were detected by the DFH instrument on ISEE-3 spacecraft during the solar maximum period, September 1978–March 1980. The observations were made by three detectors, within eight sectors 45°wide each around the spacecraft, in eight energy channels extended from 35–1600Kev. They confirm that local magnetohydrodynamic conditions, especially discontinuities, significantly affect the propagation of low energy particles in the interplanetary medium.     

Observed and model N(h) profiles for the Bulgarian region

In this paper, combined bottom- and topside ionospheric N(h)-profiles are presented for the Bulgarian region. The profiles were constructed using ground (ionospheric observatories Sofia and Michurin) and satellite (Interkosmos-19) observations /1/.The observatories make quarter-hourly observations; in order to connect bottom and upper parts of the N(h) profile, we selected satellite orbits passing rather near to the observatory (zenith distance lsss than 100 km). Thus the time difference between ground station and satellite measurement was never more than 7.5 min.     

Sporadic emission of ultra high energy gamma rays from crab pulsar

In a further study of sporadic emission from pulsars we find evidence for short lived intense emission from the Crab pulsar.     

Properties of electrophoretic fractions of human embryonic kidney cells separated on Space Shuttle flight STS-8.

Suspensions of cultured primary human embryonic kidney cells were subjected to continuous flow electrophoresis on Space Shuttle flight STS-8. The objectives of the experiments were to obtain electrophoretically separated fractions of the original cell populations and to test these fractions for the amount and kind of urokinase (a kidney plasminogen activator that is used medically for digesting blood clots), the morphologies of cells in the individual fractions, and their cellular electrophoretic mobilities after separation and subsequent proliferation. Individual fractions were successfully cultured after return from orbit, and they were found to differ substantially from one another and from the starting sample with respect to all of these properties.     

Progress in the study of homologous flares on the sun — Part II

Studies of groups of homologous flares in active regions in 1980 have been made using a variety of space and ground based instruments. Detailed properties of three of these groups have been studied, and are combined to form a possible sequence of events.     

The incompressible zero-pressure-gradient turbulent boundary layer: An assessment of the data

The available data describing the incompressible zero-pressure-gradient boundary layer are reviewed in association with a range of studies which are either new or, to date, not very generally available. The new data cover a Reynolds number range 2.5 < Re_δ2 × 10⁻³ < 58 and include measurements of all three turbulence perlurbations and the Reynolds shear stress. They are assessed in relation to data in the range 0.4 < Re_δ2 × 10⁻³ < 211 using established scaling laws. In common with other investigators we find that while scaling the mean flow leads to a high degree of apparent similarity, scaling of the turbulence quantities is in general not so satisfactory.     

Hermes: Learning from our mistakes

The paper draws conclusions from the course of the European Hermes program with the aim of identifying major programmatic, organisational and technical difficulties encountered and deriving consequences to avoid similar problems with comparable future projects. Points of interest are the basic objectives and underlying requirements and specifications, the structures implemented for the realisation and the technical philosophy of the specific solutions chosen. In all areas, severe obstacles were not detected in due time and subsequently caused complications in the course of the project. Since the majority of the deficiencies can be traced to a number of fundamental causes, a short synthesis of the important results and recommendations is presented for each of the above mentioned areas.     

Possible evidence of hydrocarbons released by the nucleus of Halley's comet.

After subtracting the intense dust-scattered continuum from the original spectra transmitted by the Vega 2 three-channel spectrometer, a broad-band emission emerges in the 342-375 nm spectral range when the cometocentric projected distance p is smaller than 5000 km. This newly detected emission varies as p-1, which implies that the involved molecule(s) has a parent-type behavior. The emission band presents four peaks at 347, 356, 364 and 373 nm. It is tentatively identified as being due to phenanthrene, a three-cycle aromatic condensed hydrocarbon. A determination of the gQ product, where g is the fluorescence quantum efficiency and Q the production rate gives gQ = 1.2 x 10(25). If g = 0.012, it comes Q = 1 x 10(27) s-1. The detection of phenanthrene in Halley's inner coma is an important argument in favor of a similarity of composition between cometary material and interstellar matter. It supports the hypothesis that comets have kept trace of the interstellar composition through the solar system formation epoch.     

Comet Halley: Nucleus and jets (results of the VEGA mission)

The VEGA-1 and VEGA-2 spacecraft made their closest approach to Comet Halley on 6 and 9 March, respectively. In this paper those results of the onboard imaging experiment which were obtained around closest approach are discussed. The nucleus of the comet was clearly identifiable as an irregularly shaped object, with overall dimensions of (16±1)×(8±1)×(8±1) km. The nucleus rotates in the prograde sense about an axis nearly perpendicular to the orbital plane with a period of 53±2 hours. Its albedo is only $\text{0.04±}\text{0.02}\text{0.01}$ Many of the jet features observed during the second fly-by have been spatially reconstructed. Their sources form a quasi-linear structure on the surface. The dust above the surface is shown to be generally optically thin with the exception of certain specific dust jets. Brightness features on the surface are clearly seen. Correlating our data with other measurements, we conclude that the dirty snow-ball model will probably need to be revised.     

The role of nonlocalities in magnetosphere-ionosphere coupling processes

Microinstabilities are believed to play a crucial role in the physics of Magnetosphere-Ionosphere coupling. The current driven ion cyclotron instability is a very important microinstability in this respect. We give a nonlocal formalism for studying the ion cyclotron instability in a more realistic magnetospheric environment than is available in the widely used local theory. This formalism includes the magnetic shear produced self-consistently by the field aligned currents and the finite extent of such currents. Significant departures from the local theory are noted.