Calculation of certain characteristics of extended air showers in the lower part of the atmosphere for large fluctuations of the elementary act

Inelastic interaction role in calculation of extended air shower characteristic

Simulations of Galactic Cosmic Rays Impacts on the Herschel/PACS Photoconductor Arrays with Geant4 Code

We present results of simulations performed with the Geant4 software code of the effects of Galactic Cosmic Ray impacts on the photoconductor arrays of the PACS instrument. This instrument is part of the ESA-Herschel payload, which will be launched in late 2007 and will operate at the Lagrangian L2 point of the Sun-Earth system. Both the Satellite plus the cryostat (the shield) and the detector act as source of secondary events, affecting the detector performance. Secondary event rates originated within the detector and from the shield are of comparable intensity. The impacts deposit energy on each photoconductor pixel but do not affect the behaviour of nearby pixels. These latter are hit with a probability always lower than 7%. The energy deposited produces a spike which can be hundreds times larger than the noise. We then compare our simulations with proton irradiation tests carried out for one of the detector modules and follow the detector behaviour under 'real' conditions.Comment: paper submitted to Experimental Astronomy in March 200

Relationships among Solar Activity, SEP Occurrence Frequency, and Solar Energetic Particle Event Distribution Function

Abstract The solar cycle 20-22 direct spacecraft measurement results are used to analyze the occurrence frequency and distribution function of solar energetic particle (SEP) events as dependent on solar activity. The analysis has shown that • the mean occurrence frequency of the SEP events with ≥30 MeV proton fluence sizes exceeding 10 6 is proportional to sunspot number, • the SEP event proton distribution functions for periods of different solar activity levels can be described to be power-law functions whose spectral form (spectral indices and cutoff values) are the same. The above results permit the following conclusions: a) to within statistical deviations, the total number of SEP events observed during any given time interval is proportional to the sum of mean-yearly sunspot numbers; b) large SEP events can occur to within quite a definite probability even during solar minima

Simulations of Galactic Cosmic Ray Impacts on the Herschel/PACS bolometer Arrays with Geant4 Code

The effects of the in-flight behaviour of the bolometer arrays of the Herschel/PACS instrument under impacts of Galactic cosmic rays are explored. This instrument is part of the ESA-Herschel payload, which will be launched at the end of 2008 and will operate at the Lagrangian L2 point of the Sun-Earth system. We find that the components external to the detectors (the spacecraft, the cryostat, the PACS box, collectively referred to as the `shield') are the major source of secondary events affecting the detector behaviour. The impacts deposit energy on the bolometer chips and influence the behaviour of nearby pixels. 25% of hits affect the adjacent pixels. The energy deposited raises the bolometer temperature by a factor ranging from 1 to 6 percent of the nominal value. We discuss the effects on the observations and compare simulations with laboratory tests.Comment: Experimental Astronomy, 2008, in pres

Observation of nuclei with energies 8-30 MeV per nucleon in the Earth's magnetosphere at the altitudes 350 KM

Observations of the flux of nuclei with an energy of IO MeV per nucleon on the Salyut-7 Station in September 1984 are presented. The observed flux is smaller by a factor of 50 than the flux detected in May, 1981

Cosmic ray particles with different LET values under various thicknesses of shielding in low altitude orbits: Calculations and Cosmos-2044 measurements

Fluxes of cosmic ray particles with different LET values were measured on board the COSMOS-2044 biosatellite under various thicknesses of shielding by stacks of CR-39 and nitrocellulose plastic nuclear track detectors (mounted outside the satellite). The component composition of the particles detected under shieldings of 0.1-2.5 g cm(exp -2) is verified by comparing experimental data with the results of model simulations of the fluxes of galactic cosmic ray particles and of radiation belt protons

Detailed Calculation of Test-Mass Charging in the LISA Mission

The electrostatic charging of the LISA test masses due to exposure of the spacecraft to energetic particles in the space environment has implications in the design and operation of the gravitational inertial sensors and can affect the quality of the science data. Robust predictions of charging rates and associated stochastic fluctuations are therefore required for the exposure scenarios expected throughout the mission. We report on detailed charging simulations with the Geant4 toolkit, using comprehensive geometry and physics models, for Galactic cosmic-ray protons and helium nuclei. These predict positive charging rates of 50 +e/s (elementary charges per second) for solar minimum conditions, decreasing by half at solar maximum, and current fluctuations of up to 30 +e/s/Hz^{1/2}. Charging from sporadic solar events involving energetic protons was also investigated. Using an event-size distribution model, we conclude that their impact on the LISA science data is manageable. Several physical processes hitherto unexplored as potential charging mechanisms have also been assessed. Significantly, the kinetic emission of very low-energy secondary electrons due to bombardment of the inertial sensors by primary cosmic rays and their secondaries can produce charging currents comparable with the Monte Carlo rates.Comment: 31 pages, 18 figures, 4 tables. to be published in Astroparticle Physics. Changed due to error found in normalisation of the simulation result

The virtual enhancements − solar proton event radiation (VESPER) model

A new probabilistic model introducing a novel paradigm for the modelling of the solar proton environment at 1 AU is presented. The virtual enhancements − solar proton event radiation model (VESPER) uses the European space agency's solar energetic particle environment modelling (SEPEM) Reference Dataset and produces virtual time-series of proton differential fluxes. In this regard it fundamentally diverges from the approach of existing SPE models that are based on probabilistic descriptions of SPE macroscopic characteristics such as peak flux and cumulative fluence. It is shown that VESPER reproduces well the dataset characteristics it uses, and further comparisons with existing models are made with respect to their results. The production of time-series as the main output of the model opens a straightforward way for the calculation of solar proton radiation effects in terms of time-series and the pairing with effects caused by trapped radiation and galactic cosmic rays

Balloon measurements of the vertical ionization profile over southern Israel and comparison to mid-latitude observations

Airborne measurements using meteorological balloons were conducted for the first time from southern Israel (geographic 30°35’N, 34°45’E geomagnetic 27°6’N 112°23’E) for measuring the vertical ionization profile during solar cycle 24. The results show the differences (increase of ~30%) in count rates as we proceed from solar maximum toward solar minimum. The observed altitude of maximum ionization (the Regener-Pfotzer maximum) was between 17–20 km, and it agrees well with results from other simultaneous measurements conducted at different latitudes (Reading, UK and Zaragoza-Barcelona, Spain). When compared with predictions of an analytical model, we find a highly significant correlation (R2=0.97) between our observations and the computed ionization profiles. The difference in count rates can be attributed to the height of the tropopause due to the model using a US standard atmosphere that differs from the measured atmospheric parameters above Israel

Ionization of the Venusian atmosphere from solar and galactic cosmic rays

The atmospheres of the terrestrial planets are exposed to solar and galactic cosmic rays, the most energetic of which are capable of affecting deep atmospheric layers through extensive nuclear and electromagnetic particle cascades. In the Venusian atmosphere, cosmic rays are expected to be the dominant ionization source below ∼100 km altitude. While previous studies have considered the effect of cosmic ray ionization using approximate transport methods, we have for the first time performed full 3D Monte Carlo modelling of cosmic ray interaction with the Venusian atmosphere, including the contribution of high-Z cosmic ray ions (Z=1-28). Our predictions are similar to those of previous studies at the ionization peak near 63 km altitude, but are significantly different to these both above and below this altitude. The rate of atmospheric ionization is a fundamental atmospheric property and the results of this study have wide-reaching applications in topics including atmospheric electrical processes, cloud microphysics and atmospheric chemistry