Primary Proton Flux Research Articles

Comparison of Atmospheric Ionization for Solar Proton Events of the Last Three Solar Cycles

Numerical modeling of primary cosmic ray protons’ transport through the Earth’s atmosphere was performed for the energy spectra of solar energetic particle events (SEPs). Several events in the last three solar cycles were considered. A comparative analysis of the characteristics of coronal mass ejections and primary proton fluxes was carried out. The main results were quantitative estimates of the calculated atmospheric ionization count rate for a wide range of altitudes (from sea level up to 98 km). The difference in the influence of solar protons on the Earth’s atmosphere is considered for seven SEPs divided into three groups with similar solar sources (X-flare magnitude and coordinates) but with different characteristics of accelerated particle fluxes. The data obtained in this work are very important for future studies of radio wave propagation, atmospheric chemistry and climate change.

The Atmospheric Radiation Interaction Simulator (AtRIS): Description and Validation

AbstractWe present the Atmospheric Radiation Interaction Simulator (AtRIS), a newly developed GEANT4‐based code tailored specifically to enable parametric studies of radiation propagation through various (exo)planetary atmospheres. Its main purpose is to model the altitude‐dependent atmospheric secondary particle environment and to calculate the ion pair production rates, which are a mandatory input for atmospheric chemistry models in order to, for example, directly characterize the habitability of the modeled planet. Similar codes have been developed previously (e.g., PLANETOCOSMICS; Desorgher, et al., ); however, until now, none possesses the necessary flexibility in the specification of the atmosphere and the regolith that is necessary to model planets outside our solar system. Here we provide a detailed description of AtRIS and its validation against earthbound measurements. For validation, we show comparisons against Earth measurements. Thereby, the focus is on the atmospheric altitude‐dependent ionization, the surface muon, and the neutron fluxes, as well as the primary proton fluxes. Furthermore, a comparison of the computed energy losses of monoenergetic protons based on AtRIS and PLANETOCOSMICS is shown. Our aim is to demonstrate the validity of AtRIS and its importance for future studies on, for example, potential (Earth‐like) exoplanets.

Shape of the primary proton spectrum in the multi-TeV region from data on the vertical muon flux

It is shown, that the primary proton spectrum, reconstructed from sea-level and underground data on the muon spectrum using the QGSJET 01, QGSJET II, NEXUS 3.97 and SIBYLL 2.1 interaction models, demonstrates not only a model-dependent intensity, but also a model-dependent form. For a correct reproduction of the muon spectrum shape the primary proton flux should have a non-constant power index for all considered models, except SIBYLL 2.1, with a break at energies around 10–15 TeV and a value of the exponent before the break close to that obtained in the ATIC-2 experiment.

Shape of primary proton spectrum in multi-TeV region from data on vertical muon flux

It is shown that the primary proton spectrum, reconstructed from sea-level and underground data on muon spectrum with the use of QGSJET 01, QGSJET II, NEXUS 3.97, and SIBYLL 2.1 interaction models, demonstrates not only model-dependent intensity, but also a model-dependent form. For correct reproduction of muon spectrum shape the primary proton flux should have a nonconstant power index for all considered models, except SIBYLL 2.1, with break at energies around 10--15 TeV and a value of exponent before break close to that obtained in the ATIC-2 experiment. To validate the presence of this break, understanding of inclusive spectra behavior in the fragmentation region in $p$-air collisions should be improved, but we show that is impossible to do on the basis of the existing experimental data on primary nuclei, atmospheric muon, and hadron fluxes.

Investigations of the response of hybrid particle detectors for the Space Environmental Viewing and Analysis Network (SEVAN)

Abstract. A network of particle detectors located at middle to low latitudes known as SEVAN (Space Environmental Viewing and Analysis Network) is being created in the framework of the International Heliophysical Year (IHY-2007). It aims to improve the fundamental research of the particle acceleration in the vicinity of the Sun and space environment conditions. The new type of particle detectors will simultaneously measure the changing fluxes of most species of secondary cosmic rays, thus turning into a powerful integrated device used for exploration of solar modulation effects. Ground-based detectors measure time series of secondary particles born in cascades originating in the atmosphere by nuclear interactions of protons and nuclei accelerated in the galaxy. During violent solar explosions, sometimes additional secondary particles are added to this "background" flux. The studies of the changing time series of secondary particles shed light on the high-energy particle acceleration mechanisms. The time series of intensities of high energy particles can also provide highly cost-effective information on the key characteristics of interplanetary disturbances. The recent results of the detection of the solar extreme events (2003–2005) by the monitors of the Aragats Space-Environmental Center (ASEC) illustrate the wide possibilities provided by new particle detectors measuring neutron, electron and muon fluxes with inherent correlations. We present the results of the simulation studies revealing the characteristics of the SEVAN networks' basic measuring module. We illustrate the possibilities of the hybrid particle detector to measure neutral and charged fluxes of secondary CR, to estimate the efficiency and purity of detection; corresponding median energies of the primary proton flux, the ability to distinguish between neutron and proton initiated GLEs and some other important properties of hybrid particle detectors.

Experimental feature in the primary-proton flux at energies above 10 TeV according to the results of searches for primary particles in nuclear emulsions exposed in the stratosphere (RUNJOB Experiment)

In the RUNJOB experiment, a long-term exposure of x-ray emulsion chambers in the stratosphere from 1995 to 1999 with the aim of studying the composition and spectra of primary cosmic particles in the energy range 10–1000 TeV per nucleon revealed about 50% proton tracks. The remaining events of the proton group did not feature any candidate for a track of a singly charged particle within the search region determined from measurements of the coordinates of background nuclei going close to the sought track. Methodological factors that could explain this experimental observation are considered. A possible physical reason associated with the presence of a neutral component in the flux of primary protons in the energy region above 10 TeV is also analyzed.

Experimental characterization and physical modelling of the dose distribution of scanned proton pencil beams

In this paper we present the pencil beam dose model used for treatment planning at the PSI proton gantry, the only system presently applying proton therapy with a beam scanning technique. The scope of the paper is to give a general overview on the various components of the dose model, on the related measurements and on the practical parametrization of the results. The physical model estimates from first physical principles absolute dose normalized to the number of incident protons. The proton beam flux is measured in practice by plane-parallel ionization chambers (ICs) normalized to protons via Faraday-cup measurements. It is therefore possible to predict and deliver absolute dose directly from this model without other means. The dose predicted in this way agrees very well with the results obtained with ICs calibrated in a cobalt beam. Emphasis is given in this paper to the characterization of nuclear interaction effects, which play a significant role in the model and are the major source of uncertainty in the direct estimation of the absolute dose. Nuclear interactions attenuate the primary proton flux, they modify the shape of the depth–dose curve and produce a faint beam halo of secondary dose around the primary proton pencil beam in water. A very simple beam halo model has been developed and used at PSI to eliminate the systematic dependences of the dose observed as a function of the size of the target volume. We show typical results for the relative (using a CCD system) and absolute (using calibrated ICs) dosimetry, routinely applied for the verification of patient plans. With the dose model including the nuclear beam halo we can predict quite precisely the dose directly from treatment planning without renormalization measurements, independently of the dose, shape and size of the dose fields. This applies also to the complex non-homogeneous dose distributions required for the delivery of range-intensity-modulated proton therapy, a novel therapy technique developed at PSI.

Neural network approach to obtain the primary proton flux at the knee from a hybrid-experiment of EC and AS array in Tibet

A hybrid experiment of emulsion chamber and air shower array will be started from 1996 at Yangbajing (4300 m above sea level) in Tibet, aimed at obtaining the primary proton flux around the knee energy region. In order to examine a classification power of proton induced showers from others using this apparatus, we have done an extensive Monte Carlo simulation in which the observation conditions were adequately taken into account. For this purpose, a multiple layered feed forward neural network was used as a classifier to select proton and helium induced shower events preferentially. It is shown that the separation of protons and the proton-helium group from all events can be achieved with an efficiency of 80–85%. The performance of the experiment under a two-year exposure is discussed.

Model calculation of hydrogen balmer emissions under various modes of proton precipitation

A theoretical model is developed to study the H α and H β volume emission rates in proton auroras. The H α and H β photon yields are deduced by using the recent experimental cross-sections. These photon yields are then coupled with the primary proton fluxes to get the altitude profiles of the emissions. The prediction of the altitude profiles are found in good agreement with the auroral measurements. The effects of various modes of proton precipitation on the emission intensities (IH α and IH β) are discussed and a comparison is made with the earlier theoretical models. It is also found that the intensity ratio IH α/IH β varies between 5 and 6.

An estimation of the primary proton spectrum between 1012and 1014eV

Based on measurements of the unaccompanied charged hadron flux from 1011 to 1014 eV at mountain altitudes, the authors estimate the primary proton flux using recently determined proton-proton total cross sections from new measurements of the real part of the forward scattering amplitude at ISR, and Glauber theory to calculate the proton-air inelastic cross section. The derived spectrum agrees well with extrapolation of the direct measurements below 2*1012 eV without change of slope.

Evidence for Heavy-Particle Production Processes at Energies above 2×1011eV

Cosmic-ray flux measurements in the energy region ${10}^{10}$-${10}^{14}$ eV obtained by calorimeters on the satellites Proton I and II have shown results that are at variance with previous data. While a single power law provides an approximate fit to the all-particle spectrum, the primary proton flux falls sharply at energies above \ensuremath{\sim}5\ifmmode\times\else\texttimes\fi{}${10}^{11}$ eV, indicating that at high energies protons become progressively scarcer in the primary flux. The cross section for particle production by protons on carbon is found to rise by 20% in the interval between 2\ifmmode\times\else\texttimes\fi{}${10}^{10}$ and ${10}^{12}$ eV. Assuming that, in the energy region of interest, (1) the real proton flux is given by a single power law, and (2) the nuclear composition remains constant, we show that the satellite flux measurements can be explained by an energy-loss mechanism in the calorimeter, the loss being a function of the energy per nucleon rather than the total energy. Furthermore, this process has a cross section of the right magnitude to account for the $p$-carbon cross-section measurements. The $X$ process could be described in terms of particle production or dissociation of the primary protons.

Effect of the interplanetary magnetic field on solar neutron-decay protons

Upper bounds are placed on both steady-state and pulse (flare) outflow of neutrons above 1 Mev from the sun. The bounds are obtained by assuming that the neutrondecay protons diffuse in the interplanetary magnetic field, in order to calculate the resultant proton fluxes from simple diffusion theory, and then comparing the theoretical fluxes with recent proton observations. Using the Imp 1 proton spectrum (20–75 Mev) it is shown that there could have been no significant contribution to the inner-belt proton population in that energy range by steady neutron outflow in the first half of 1964, and perhaps as far back as 1961. For the same period and energy range it is concluded that there could have been no higher steady outflow from the sun than ∼1022 neutrons sec−1 Mev−1. As opposed to the meaningful upper bounds obtained for steady neutron outflow, it is found that neutron-decay protons are insensitive indicators of the presence of neutrons in solar flares. For instance, on the order of 10% of flare particles at energies 1 to 100 Mev could be neutrons and yet their decay protons would cause only marginally observable modifications of the primary proton flux during the times of diffusion behavior at 1 AU. The same is true at 0.5 and 1.5 AU.

A measurement of the primary proton flux from 10 to 130 million electron volts

A counter telescope, composed of nine AuSi solid-state detectors for measuring the energy loss and range of vertically incident particles, was carried into a polar orbit by an oriented satellite on December 12, 1961. The choice of detectors and absorbers allowed separation of protons and α particles with energies between 10 and 250 Mev/nucleon. Although the quantity of data was limited by the failure of the vehicle transmitter, both the observed 85- to 130-Mev proton flux and the α-particle flux are consistent with other 1961 observations. In addition, a proton flux of ∼1 m−2 sec−1 ster−1 Mev−1 was measured in the energy range 10–85 Mev, indicating that the quiet time spectrum was much ‘flatter’ than the E−2 spectrum that others have observed at higher energies.

On an attempt of detection of primary cosmic photons of very high energy

In relation to the primary proton flux of very high energy ((1015÷1016) eV), the possible photon flux of equal energy created by the p-p collisions of protons with the diffused matter of the Universe, is evaluated taking into account the multiple production of the π0-mesons and their decay. If a trace of very high energy photons exists among the primary flux, two types of EAS must be produced in the air: 1) ordinary EAS; 2) pure photon-electron cascades. Taking advantage of the difference between the number of electrons produced at sea level by a protonic and by a photonic EAS of equal energy (therefore resulting in an amplification factor of the observable effect by at least ten times) it is shown that it is possible to separate these two types by studying the penetrating component with the help of a large detection area and to disclose a real limit rate as small as 10−4. Considering current cosmological estimates, it gives some possibility of observing a significant rate. This method therefore may give new experimental information on the origin of cosmic rays and on individual interaction at very high energy.

Particle Energies and Magnetic Energy in the Crab Nebula.

view Abstract Citations (34) References (14) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Particle Energies and Magnetic Energy in the Crab Nebula. Burbidge, G. R. Abstract Some difficulties associated with the estimates of the probable values of the particle and magnetic energies in the model of the Crab proposed by Oort and Walraven are discussed. To overcome these, a model is described in which the high-energy electrons and positrons necessary to explain the synchrotron emission are secondary particles which are produced following nuclear collisions of a primary proton flux. It is found that the total energy in this proton flux must amount to 5 X 1050 ergs, while the continuously replenished flux of electrons and positrons, which have mean lives of only about 1-5 years, amounts to 1-5 X 1048 ergs. The magnetic field in the nebula is then 3 - 1 X 10-2 gauss. Though the total energy is much greater than that proposed in the Oort-Walraven model, the difficulties of acceleration and continuous replenishment of the electron-positron flux are thereby overcome. It is pointed out that the current radioactive energy input of the Crab is probably negligible in comparison with this total energy, which must have been derived from the initial explosion of the supernova. Publication: The Astrophysical Journal Pub Date: January 1958 DOI: 10.1086/146437 Bibcode: 1958ApJ...127...48B full text sources ADS |