Search Publications

Performance of ERNE in particle flux anisotropy measurement

Valtonen, E.; Lumme, M.; Riihonen, E. +3 more

The HED particle detector of the ERNE experiment to be flown on the SOHO spacecraft is unique compared to the earlier space-born detectors in its high directional resolution (better than 2°, depending on the track inclination). Despite the fixed view cone due to the three-axis stabilization of the spacecraft, the good angular and temporal resoluti…

Geminga in the Space Telescope Era.

Caraveo, P. A.; Bignami, G. F.; Mignani, R. +1 more

The distance to Geminga inferred from the γ-ray flux, the interstellar absorption of the soft X-ray emission and the proper motion measured for its optical counterpart, range from tens of parsecs to an upper limit of severl hundreds of parsecs. These distance estimates, however, are based on a number of assumptions on the emission mechanisms, on t…

Camera Artifacts in IUE High-Dispersion Spectra

Crenshaw, D. Michael; Bruegman, Ottow W.; Johnson, Rita +1 more

Sky-background images obtianed with the International Ultraviolet Explorer (IUE) have been analyzed to identify camera artifacts in high-dispersion point-source spectra observed through the large aperture. The camera artifacts are artificial emission features that are apparent in all IUE spectra with exposure times longer than about one hour. The …

Comment on “The underlying magnetic field direction in Ulysses observations of the southern polar heliosphere” by Forsyth et al.

Smith, Charles W.; Bieber, John W.

3D heliospheric simulations of cosmic rays in the light of Ulysses.

Jokipii, J. R.; Kota, J.

Recent Ulysses observations in the polar regions of the heliosphere have provided fundamental new insights into the modes of cosmic-ray transport in the heliosphere. Ulysses discovered variations in the magnetic field which are large enough to produce significant cosmic-ray effects, and which are consistent with a previous prediction. In addition …

Taurid complex meteoroids detected near aphelion with ULYSSES

Grün, E.; McDonnell, J. A. M.; Taylor, A. D.

Between 3.4 and 4.0 AU the dust detection system aboard the Ulysses spacecraft showed an increase in detection rate for particles with masses greater than 5 x 10^-13 g. The spacecraft meteoroid encounter geometry indicates highly eccentric orbits detected near aphelion. The outer limit of the enhanced flux is imposed as meteoroids on such orbits m…

Collision of comet Shoemaker-Levy 9 with Jupiter: impact study of two fragments from the timing of precursor events.

Sekanina, Z.

The impacts of fragments K and R of comet Shoemaker-Levy 9 are examined with the aims to interpret the timing of the observed precursors to the main thermal emission event and to correlate the results of ground-based infrared observations with a variety of observations made onboard the Galileo spacecraft. Analysis of the phenomena associated with …

A multi-layered backpropagation artificial neural network algorithm for UV spectral classification

Gupta, Ranjan; Mukherjee, Soma; Bhattacharya, Ujjwal +2 more

In this paper we present an application of an artificial neural network model based on a multi-layered backpropagation algorithm for spectral classification of UV data from the International Ultraviolet Explorer (IUE) low dispersion spectra reference atlas. The model used is similar to that of von Hippel et al. (1994), and is found to reduce the c…

Comparison of the wave energy transport at comets p/Halley and p/Giacobini-Zinner

Tsurutani, B. T.; Glassmeier, K. -H.; Neubauer, F. M. +2 more

Using magnetic field, plasma density and flow observations from spacecraft flybys of two comets, Elsässer variables are determined in order to study wave propagation directions. The inbound path of the Giotto spacecraft flyby of comet p/Halley is investigated outside the bow shock (between 10:36 and 19:11 UT on March 13, 1986, corresponding to dis…

Calculating the Plasma Deformation Tensor and Kinetic Vorticity from Magnetic Field Time Series: Applications to the Solar Wind

Moussas, X.; Polygiannakis, J. M.

It is shown that the magnetic induction equation reduces to an autoregressive model equation. Assuming weakly ergodic field variations in steady mean plasma flow, this model permits the estimation of the mean flow deformation tensor, velocity divergence and kinetic vorticity from magnetic field time series. Applications, made to hourly-averaged, i…