Wide Range Of Zenith Angles Research Articles

Scalar-potential mapping of the steady-state magnetosheath model

Abstract. The steady-state magnetosheath model has various applications for studying the plasma and magnetic field profile around the planetary magnetospheres. In particular, the magnetosheath model is analytically obtained by solving the Laplace equation for parabolic boundaries (bow shock and magnetopause). We address the question, how can we utilize the magnetosheath model by transforming into a more general, empirical, non-parabolic magnetosheath geometry? To achieve the goal, we develop the scalar-potential mapping method which provides a semi-analytic estimate of steady-state flow velocity and magnetic field in the empirical magnetosheath domain. The method makes use of a coordinate transformation from the empirical magnetosheath domain into the parabolic magnetosheath domain and evaluates a set of variables (shell variable and connector variable) to utilize the solutions of the Laplace equation obtained for the parabolic magnetosheath domain. Our model uses two invariants of transformation: the zenith angle within the magnetosheath with respect to the direction to the Sun and the ratio of the distance to the magnetopause and the thickness of magnetosheath along the magnetopause-normal direction. The use of magnetopause-normal direction makes a marked difference from the earlier model construction using the radial direction as reference. The plasma flow and magnetic field can be determined as a function of the upstream condition (flow velocity or magnetic field) in a wide range of zenith angles. The scalar-potential mapping method is computationally inexpensive, using analytic expressions as much as possible, and is applicable to various planetary magnetosheath domains.

The Zenith‐Angle Dependence of the Downward Radiation Dose Rate on the Martian Surface: Modeling Versus MSL/RAD Measurement

AbstractThe Radiation Assessment Detector (RAD) on board the Mars Science Laboratory's Curiosity rover has been monitoring the surface radiation environment on Mars for just over 10 years. It has been found by Wimmer‐Schweingruber et al. (2015, https://doi.org/10.1002/2015gl066664) that within the narrow view cone of RAD, the directionality of the radiation field is close to but not completely isotropic. In order to better understand the directionality of the surface radiation over a wide range of zenith angles (θ), we perform a three‐dimensional Geant4 Monte Carlo simulation to derive the θ‐dependence of the surface dose rate. The results show that galactic cosmic ray protons, coming in at θ ∼ 74° make the greatest contribution to the surface dose. For helium ions, this angle is at around 46°. This is a consequence of the increasing column depth at larger zenith angles and the complex interplay of the destruction of primary and the creation of secondary particles as the primary cosmic ray interacts with the Martian atmosphere. We also compared the simulated results with the RAD measurements and found a reasonable agreement. Our results are important for future human exploration of Mars, for instance, to estimate the effectiveness of radiation shielding of a given geometry or for optimizing the radiation shielding design of a Martian habitat.

A new gas absorption optical depth parameterisation for RTTOV version 13

Abstract. This paper describes a new gas optical depth parameterisation implemented in the most recent release, version 13, of the radiative transfer model RTTOV (Radiative Transfer for TOVS). RTTOV is a fast, one-dimensional radiative transfer model for simulating top-of-atmosphere visible, infrared, and microwave radiances observed by downward-viewing space-borne passive sensors. A key component of the model is the fast parameterisation of absorption by the various gases in the atmosphere. The existing parameterisation in RTTOV has been extended over many years to allow for additional variable gases in RTTOV simulations and to account for solar radiation and better support geostationary sensors by extending the validity to higher zenith angles. However, there are limitations inherent in the current approach which make it difficult to develop it further, for example by adding new variable gases. We describe a new parameterisation that can be applied across the whole spectrum, that allows for a wide range of zenith angles in support of solar radiation and geostationary sensors, and for which it will be easier to add new variable gases in support of user requirements. Comparisons against line-by-line radiative transfer simulations and against observations in the ECMWF operational system yield promising results, suggesting that the new parameterisation generally compares well with the old one in terms of accuracy. Further validation is planned, including testing in operational numerical weather prediction data assimilation systems.

NEVOD–DECOR Experiment on the Measurement of the Energy Deposit of Cosmic Ray Muon Bundles

In comparison with calculations, the excess of multimuon events found in many experiments at ultrahigh energies of extensive air showers (EASs) cannot be explained using modern models of hadron interactions. The existence of muon excess is called the muon puzzle. One of the ways to solve this problem is to study the energy characteristics of the EAS muon component. For this purpose, the energy deposit of cosmic ray muon bundles is measured in the NEVOD–DECOR experiment. Registration of muon bundles in a wide range of zenith angles allows one to explore a wide range of energies of the primary particles of cosmic rays (from 10 to 1000 PeV) within a single experiment. The results of measurements of the energy deposit of muon bundles over a long observation period are presented.

Experimental Data of Muon Hodoscope URAGAN for Investigations of Geoffective Processes in the Heliosphere

Muon hodoscope URAGAN continuously detects the angular distribution of muons in a wide range of zenith angles and allows one to obtain information about variations, both in the intensity and in angular characteristics of the muon flux, caused by active processes in the heliosphere, the magnetosphere and atmosphere of the Earth. Various parameters of the muon flux anisotropy and methods of calculation of these parameters are discussed. Real-time processing of a continuous flow of multidimensional data from the muon hodoscope URAGAN is quite a challenge. In the article, methods of formation and primary analysis of the data, their processing in real time and obtaining time series of various parameters of integral counting rate and angular anisotropy of the muon flux, which are important for the physical analysis of modulation processes of cosmic rays in the heliosphere, are presented.

Horizon-T experiment and detection of Extensive air showers with unusual structure

Horizon-T is an innovative detector system constructed to study temporary structure of Extensive Air Showers (EAS) in the energy range above ~1016 eV coming from a wide range of zenith angles (up to 80°). The system, located at Tien Shan high-altitude Science Station at approximately 3340 meters above the sea level, consists of eight charged particle detection points separated by the distance up to one kilometer. The time resolution of charged particles passage of the detector system is a few ns. This level of resolution allows conducting research of atmospheric development of individual EAS. The total of ~8500 Extensive Air Showers (EAS) with the energy above 1016 eV has been detected during the ~4000 hours of Horizon-T detectors system operations since October 24, 2016 to April 21, 2017. A notable number of events has a spatial and temporary structure that showed the pulses with several maxima (modals or modes) from several detection points of the Horizon-T at the same time as described further in this work. These modes are separated in time from each other starting from tens to thousands of ns. Some are further classified as unusual event with common structure.

Extensive air showers event reconstruction using spatial and temporary particle distribution at Horizon-T experiment

A newly completed (Oct. 2016) detector system of Extensive Air Showers (EAS) called Horizon-T (HT) is a part of Tien Shan high-altitude Science Station of Lebedev Physical Institute of the Russian Academy of Sciences, which is located 32 km from Almaty at the altitude of 3340 meters above the sea level. Horizon-T is constructed to study Extensive Air Showers in the energy range above ∼1016 eV coming from a wide range of zenith angles (0° - 85°). The system currently has eight working and two under construction charged particle detection points separated by the distance more than a kilometer. The ability to record each detector response with accuracy of 2 ns gives HT ability to study the temporary structure of EAS disk and apply the results to the event reconstruction. The reconstruction is therefore based on chronotron (< 0.5 ns), spatial and temporary distribution of charged particles within the detected EAS event. In this paper, we will show the simulated time distribution of charged particles in the EAS disk vs. distance from the axis and the correspondence to the data. A flow of the reconstruction of standard EAS events and the event display is presented as well as recent HT results.

A simulation study on few parameters of Cherenkov photons in extensive air showers of different primaries incident at various zenith angles over a high altitude observation level

We have studied the distribution patterns of lateral density, arrival time and angular position of Cherenkov photons generated in Extensive Air Showers (EASs) initiated by γ-ray, proton and iron primaries incident with various energies and at various zenith angles. This study is the extension of our earlier work [1] to cover a wide energy range of ground based γ-ray astronomy with a wide range of zenith angles (≤40°) of primary particles, as well as the extension to study the angular distribution patterns of Cherenkov photons in EASs. This type of study is important for distinguishing the γ-ray initiated showers from the hadronic showers in the ground based γ-ray astronomy, where Atmospheric Cherenkov Technique (ACT) is being used. Importantly, such study gives an insight on the nature of γ-ray and hadronic showers in general. In this work, the CORSIKA 6.990 simulation code is used for generation of EASs. Similarly to the case of Ref. [1], this study also revealed that, the lateral density and arrival time distributions of Cherenkov photons vary almost in accordance with the functions: ρch(r)=ρ0e−βr and tch(r)=t0eΓ/rλ respectively by taking different values of the parameters of functions for the type, energy and zenith angle of the primary particle. The distribution of Cherenkov photon’s angular positions with respect to shower axis shows distinctive features depending on the primary type, its energy and the zenith angle. As a whole this distribution pattern for the iron primary is noticeably different from those for γ-ray and proton primaries. The value of the angular position at which the maximum number of Cherenkov photons are concentrated, increases with increase in energy of vertically incident primary, but for inclined primary it lies within a small value (≤1°) for almost all energies and primary types. No significant difference in the results obtained by using the high energy hadronic interaction models, viz., QGSJETII and EPOS has been observed.

Energy characteristics of multi-muon events in a wide range of zenith angles

Change of the energy characteristics of muon bundles with an increase of the primary cosmic ray particles energy can be a key to solving the problem of muon excess in the extensive air showers (EAS) observed in a number of experiments. In this work the data on the energy deposit of multi-muon events in a wide range of zenith angles (and as a consequence in a wide range of primary particles energies) obtained with NEVOD-DECOR setup over a long time period are presented. The experimental data are compared with the results of simulations of EAS muon component performed using CORSIKA code.

Horizon-T experiment status

Horizon-T is an innovative detector system constructed to study Extensive Air Showers (EAS) in the energy range above 1016 eV coming from a wide range of zenith angles (0°–85°). The system is located at the Tien Shan High-altitude Science Station of the Lebedev Physical Institute of the Russian Academy of Sciences at ∼ 3340 meters above sea level. It consists of eight charged particle detection points separated by distances up to one kilometer as well as an optical detector subsystem to measure the Vavilov-Cherenkov light from the EAS. The time resolution of charged particles and Vavilov-Cherenkov light photons passage of the detector system is a few ns. This level of resolution allows conducting a research of the atmospheric development of individual EAS. This report focuses on a general description of the detector system and the individual sub-systems providing an overview of the operations and latest results.

Horizon-T experiment status

Horizon-T is an innovative detector system constructed to study Extensive Air Showers (EAS) in the energy range above 10 16 eV coming from a wide range of zenith angles (0 ° –85 ° ). The system is located at the Tien Shan High-altitude Science Station of the Lebedev Physical Institute of the Russian Academy of Sciences at ∼ 3340 meters above sea level. It consists of eight charged particle detection points separated by distances up to one kilometer as well as an optical detector subsystem to measure the Vavilov-Cherenkov light from the EAS. The time resolution of charged particles and Vavilov-Cherenkov light photons passage of the detector system is a few ns. This level of resolution allows conducting a research of the atmospheric development of individual EAS. This report focuses on a general description of the detector system and the individual sub-systems providing an overview of the operations and latest results.

Search of predictors of geoeffective heliospheric events by means of muon hodoscope URAGAN

The flux of charged primary cosmic rays (PCR) is modulated by changes of interplanetary magnetic field which depend on various heliospheric processes. After interaction of PCR with nuclei of atoms of the Earth's atmosphere, these modulations are transferred to a flux of secondary muons. Muon hodoscope URAGAN allows to trace changes not only of intensity of the muon flux, but also its angular distribution in a wide range of zenith angles (0-80°). Some results of searching of predictors of geoeffective heliospheric events by means of muon hodoscope URAGAN are presented.

Measurements of the energy deposit of inclined muon bundles in the CWD NEVOD

First results of investigations of the energy deposits of inclined muon bundles in the ground-based Cherenkov water detector NEVOD are presented. As a measure of the muon bundle energy deposit, the total number of photoelectrons detected by PMTs of the Cherenkov calorimeter is used. For each event, the local muon density at the observation point and the muon bundle arrival direction are estimated from the data of the coordinate-tracking detector DECOR. Registration of the bundles in a wide range of zenith angles allows to explore the interval of primary particle energies from ∼ 1016 to ∼ 1018 eV. Measurement results are compared with CORSIKA based simulations of EAS muon component. It is found that the mean energy of muons detected in the bundles rapidly increases with the zenith angle and reaches about 500 GeV near the horizon.

Real-time data of muon hodoscope URAGAN

Muon hodoscope URAGAN continuously detects the angular distribution of muons in a wide range of zenith angles and allows to obtain information about the variations both in the intensity and angular characteristics of the muon flux related with active processes in the heliosphere, the magnetosphere and atmosphere of the Earth. This paper describes the procedure of organizing of real-time URAGAN data presented in the Internet.

Real-time data of the URAGAN muon hodoscope

Data from detectors deployed on space satellites and on the surface of the Earth are used to monitor space weather. One such detector is the URAGAN muon hodoscope, which registers the angular distribution of the muon flux in a wide range of zenith angles. The results from processing data in the real-time mode are time series of characteristics of angular distributions. Images of the current plots of time series and matrices of variations of angular distributions can be seen at the NEVOD experimental complex’s website on the Internet.

Corrections for temperature effect for ground-based muon hodoscopes

Influence of atmospheric temperature on muon flux at sea level is considered. Results of calculations of muon spectrum for normal atmospheric conditions, differential temperature coefficients (DTC) for muons at different zenith angles and threshold energies are presented. In calculations, a six-layer stationary spherical model of atmosphere is used, contributions of both pions and kaons as well as dependence of muon energy loss on muon energy are taken into account. Comparison of muon spectrum calculations and experimental data in a wide range of zenith angles and momentums shows a good agreement. Comparison of results of DTC calculations with results of earlier works exhibits only qualitative agreement; possible sources of differences are analyzed. Some practical questions of the use of DTC for muon hodoscope data analysis are discussed.

A new approach to EAS investigations in the energy region 1015–1019 eV

A new method of extensive air shower (EAS) investigations based on a new phenomenological variable—local muon density at the observation point—is discussed. It is shown that local muon density spectra are sensitive to primary spectrum shape, primary composition and hadronic interaction model. Ground level measurements of muon density spectra in a wide range of zenith angles provide the possibility to study EAS spectrum in very wide energy interval by means of a single, relatively small-size setup. New data on muon bundles obtained with Russian-Italian coordinate-tracking detector DECOR are compared with simulation results for different spectrum and interaction models.

Investigation of cosmic rays above the knee by means of muon bundles detected in a wide range of zenith angles

The results of investigation of muon bundles at the Earth’s surface in a wide range of zenith angles on the basis of the new phenomenological characteristic of extensive air showers—spectra of local muon density—have been investigated. Features of the local-density spectra are considered within a simple analytical model. The expected distributions of muon density in a wide range of zenith angles and primary energies, calculated on the basis of the CORSIKA code, are compared with the experimental data.

Muon bundles produced by UHE cosmic rays at large zenith angles

The first experimental results on a new EAS observable, the local muon density spectra measured with a large area coordinate detector DECOR in a wide range of zenith angles, are presented. These data correspond to the interval of primary particle energies from 1015 to 1018 eV. Some features of local muon density phenomenology are considered on the basis of an analytical model. Expected distributions of the events in the muon density have been calculated by means of the CORSIKA code and compared with experimental data.

Parametric resonance of neutrino oscillations and passage of solar and atmospheric neutrinos through the earth

We present an exact analytic solution to the neutrino evolution equation in matter with a periodic step-function density profile and discuss in detail parametric resonance of neutrino oscillations that can occur in such a system. Solar and atmospheric neutrinos traversing the earth pass through layers of alternating density and can therefore experience parametric resonance of their oscillations. Atmospheric neutrinos can undergo parametrically enhanced oscillations in the earth when their trajectories deviate from the vertical by about 26–32. Solar neutrinos traversing the earth can experience a strong parametric resonance of their oscillations in a wide range of zenith angles. If the small mixing angle MSW effect is the solution of the solar neutrino problem, the oscillations of solar neutrinos crossing the core of the earth must undergo strong parametric resonance; this phenomenon should facilitate significantly the observation of the day-night effect in oscillations of solar neutrinos. If observed, the enhanced day-night effect for core crossing neutrinos would therefore confirm both the MSW solution of the solar neutrino problem and parametric resonance of neutrino oscillations.