Dosimetric mapping inside BIORACK

The experiment was flown in different locations inside BIORACK on the D1 mission. It contained different plastic detectors (cellulose nitrate, Lexan, and CR 39) and emulsions to measure the high LET components of the radiation environment. For low LET measurements thermoluminescence dosimeters (L iF) were used. The paper gives data about total dose, charge, energy, and LET spectra so far obtained. These data are compared with data of previous spaceflights.     

Embryogenesis and organogenesis of Carausius morosus under spaceflight conditions

The influence of cosmic radiation and/or microgravity on insect development was studied during the 7 day German Spacelab Mission D1. Eggs of Carausius morosus of five stages differing in sensitivity to radiation and in capacity to regeneration were allowed to continue their development in the BIORACK 22°C incubator, either at microgravity conditions or on the 1 g reference centrifuge. Using the Biostack concept - eggs in monolayers were sandwiched between visual track detectors - and the 1 g reference centrifuge, we were able to separate radiation effects from microgravity effects and also from combined effects of these two factors in space. After retrieval, hatching rates, growth kinetics and anomaly frequencies were determined in the different test samples. The early stages of development turned out to be highly sensitive to single hits of cosmic ray particles as well as to the temporary exposure to microgravity during their development. In some cases, the combined action of radiation and microgravity even amplified the effects exerted by the single parameters of space. Hits by single HZE particles caused early effects, such as body anomalies, as well as late effects, such as retarded growth after hatching. Microgravity exposure lead to a reduced hatching rate. A synergistic action of HZE particle hits and microgravity was established in the unexpectedly high frequency of anomal larvae. However, it cannot be excluded, that cosmic background radiation or low LET HZE particles are also causally involved in damage observed in the microgravity samples.     

The composition and distribution of anomalous cosmic rays

The composition of anomalous cosmic rays (ACR), is thought to reflect that of the neutral atoms in the very local interstellar medium, such as helium, nitrogen and neon. Recent observations in the outer heliosphere have provided the first unambiguous evidence for ACR argon, carbon and hydrogen, as well, and a method has been developed to relate the ACR abundances to those of the interstellar medium. The observations also indicate persistent negative latitudinal gradients, opposite to that observed by Pioneer 11 during the previous minimum in solar activity. These and other results are consistent with the presence of gradient and curvature drift during solar minimum periods when the tilt of the interplanetary neutral sheet is small.     

Correction to: Determining the Relative Cratering Ages of Regions of Psyche’s Surface

Space Science Reviews - Analysis of Homestake, Gallex and GNO measurements reveals evidence of variability of presumed solar-neutrino-flux measurements. Analysis of Super-Kamiokande neutrino...     

SIGMA observations of hard X-ray and soft gamma-ray emission from X-ray binaries

After more than two years of operation, the imaging γ-ray SIGMA telescope has accumulated several days of observation toward well known X-ray binaries. Four bright sources falling in this category have been detected so far: The pulsar GX 1+4 near the center of our galaxy, the stellar wind accreting system 4U 1700-377, and the black hole candidates Cygnus X-1 and GX 339-4. Moreover, SIGMA have observed three transients sources, which turned out to be also hard X-ray sources : The burster KS 1731-260, Tra X-1, and the Musca Nova. The properties of these systems in the SIGMA domain will be reviewed and a spectral distinction between black holes and neutron stars will be sketched.     

Observations of diffuse galactic positron annihilation radiation

The Galactic plane was scanned nearly three times by the UCSD/MIT Hard X-Ray and Low Energy Gamma-Ray Experiment on HEAO-1 from August 1977 through September 1978. Its Medium Energy Detectors were of the NaI/CsI phoswich type and operated over the 100 keV to 2 MeV range, with a 17° FWHM field of view and a 9% energy resolution at 511 keV. Sky maps for each epoch of observation were constructed in several energy bands. After subtraction of known point sources, a component associated with the galactic plane remains, whose spectrum is consistent with a power law and a positron annihilation spectrum. In the 333 to 583 keV energy band the flux is concentrated within ±35° of the galactic center, and the ratio of flux/radian (anticenter) is high, with a 2σ lower limit of 13. The parameters of the galactic center region's annihilation spectrum are positronium fraction of 0.9±0.1 and 511 keV flux of (2.0±0.7)×10⁻³ photons/cm²-sec-rad.     

Interplanetary shocks and sudden impulses during solar maximum (2000) and solar minimum (1995–1996)

In this work a study is performed on the correlation between fast forward interplanetary shock parameters at 1 Astronomical Unit and sudden impulse (SI) amplitudes in the H-component of the geomagnetic field, for periods of solar activity maximum (year 2000) and minimum (year 1995–1996). Solar wind temperature, density and speed, and total magnetic field, were taken to calculate the static pressures (thermal and magnetic) both in the upstream and downstream sides of the shocks. The variations of the solar wind parameters and pressures were then correlated with SI amplitudes. The solar wind speed variations presented good correlations with sudden impulses, with correlation coefficients larger than 0.70 both in solar maximum and solar minimum, whereas the solar wind density presented very low correlation. The parameter better correlated with SI was the square root dynamic pressure variation, showing a larger correlation during solar maximum (r = 0.82) than during solar minimum (r = 0.77). The correlations of SI with square root thermal and magnetic pressure were smaller than with the dynamic pressure, but they also present a good correlation, with r > 0.70 during both solar maximum and minimum. Multiple linear correlation analysis of SI in terms of the three pressure terms have shown that 78% and 85% of the variance in SI during solar maximum and minimum, respectively, are explained by the three pressure variations. Average sudden impulse amplitude was 25 nT during solar maximum and 21 nT during solar minimum, while average square root dynamic pressure variation is 1.20 and 0.86 nPa^1/2 during solar maximum and minimum, respectively. Thus on average, fast forward interplanetary shocks are 33% stronger during solar maximum than during solar minimum, and the magnetospheric SI response has amplitude 20% higher during solar maximum than during solar minimum. A comparison with theoretical predictions (Tsyganenko’s model corrected by Earth’s induced currents) of the coefficient of sudden impulse change with solar wind dynamic pressure variation showed excellent agreement, with values around 17 nT/nPa^1/2.     

Great solar bursts of October 19, 22 and 23, 1989

Itapetinga measurements at 48 GHz with the multibeam technique are used to determine the relative position of solar burst centroid of emission with high spatial accuracy and time resolution. For the Great Bursts of October 19,22, 1989, with a large production of relativistic particles, and October 23, it is suggested that, at 48 GHz, the bursts might have originated in more then one source in space and time. Additionally the October 19 and 22 Ground Level Events exhibited very unusual intensity-time profiles including double component structures for the onset phase. The Bern observatory spectral radio emission data show a strong spectral flattening typical for large source inhomogeneties. The interpretation for this is that large solar flares are a superposition of a few strong bursts (separated both in space and time) in the same flaring region.     

Digital signal processing and numerical analysis for radar in geophysical applications

Numerical solutions for signal processing are described in this work as a contribution to study of echo detection methods for ionospheric sounder design. The ionospheric sounder is a high frequency radar for geophysical applications. The main detection approach has been done by implementing the spread-spectrum techniques using coding methods to improve the radar’s range resolution by transmitting low power. Digital signal processing has been performed and the numerical methods were checked. An algorithm was proposed and its computational complexity was calculated.     

Modelling and observing Jovian electron propagation times in the inner heliosphere

The propagation of Jovian electrons in interplanetary space was modelled by solving the relevant transport equation numerically through the use of stochastic differential equations. This approach allows us to calculate, for the first time, the propagation time of Jovian electrons from the Jovian magnetosphere to Earth. Using observed quiet-time increases of electron intensities at Earth, we also derive values for this quantity. Comparing the modelled and observed propagation times we can gauge the magnitude of the transport parameters sufficiently to place a limit on the 6 MeV Jovian electron flux reaching Earth. We also investigate how the modelled propagation time, and corresponding Jovian electron flux, varies with the well-known ∼13 month periodicity in the magnetic connectivity of Earth and Jupiter. The results show that the Jovian electron intensity varies by a factor of ∼10 during this cycle of magnetic connectivity.