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1.
The energy reconstruction of extensive air showers measured with the LOFAR Radboud Air Shower Array (LORA) is presented in detail. LORA is a particle detector array located in the center of the LOFAR radio telescope in the Netherlands. The aim of this work is to provide an accurate and independent energy measurement for the air showers measured through their radio signal with the LOFAR antennas. The energy reconstruction is performed using a parameterized relation between the measured shower size and the cosmic-ray energy obtained from air shower simulations. In order to illustrate the capabilities of LORA, the all-particle cosmic-ray energy spectrum has been reconstructed, assuming that cosmic rays are composed only of protons or iron nuclei in the energy range between ∼2 × 1016 and 2 × 1018 eV. The results are compatible with literature values and a changing mass composition in the transition region from a Galactic to an extragalactic origin of cosmic rays.  相似文献   

2.
The GU miniarray is a ultra high energy cosmic ray (UHECR) detector consisting of eight plastic scintillators of carpet area 2 m2, each viewed by fast PMTs. It is used to detect Giant EAS by the method of time spread measurement of secondary particles produced in the atmosphere. The energies of the air showers have been reestimated using CORSIKA program. As in the original analysis the Cosmic Ray energy was determined via its relation to the ground level parameter Ns, the shower size. This relation was obtained previously through a best fit relation in agreement with QGS model and Yakutsk data. In this work we use CORSIKA code with QGSJET model of high energy hadronic interactions to simulate miniarray data leading to a modified relation between primary energy and shower size. A revised energy spectrum is reported for 1017–1019 eV primary energy.  相似文献   

3.
High energy neutrinos play a very important role for the understanding of the origin and propagation of ultra high energy cosmic rays (UHECR). They can be produced as a consequence of the hadronic interactions suffered by the cosmic rays in the acceleration regions, as by products of the propagation of the UHECR in the radiation background and as a main product of the decay of super heavy relic particles. A new era of very large exposure space observatories, of which the JEM-EUSO mission is a prime example, is on the horizon which opens the possibility of neutrino detection in the highest energy region of the spectrum. In the present work we use a combination of the PYTHIA interaction code with the CONEX shower simulation package in order to produce fast one-dimensional simulations of neutrino initiated showers in air. We make a detail study of the structure of the corresponding longitudinal profiles, but focus our physical analysis mainly on the development of showers at mid and high altitudes, where they can be an interesting target for space fluorescence observatories.  相似文献   

4.
《Astroparticle Physics》2009,32(2):89-99
Atmospheric parameters, such as pressure (P), temperature (T) and density (ρ∝P/T), affect the development of extensive air showers initiated by energetic cosmic rays. We have studied the impact of atmospheric variations on extensive air showers by means of the surface detector of the Pierre Auger Observatory. The rate of events shows a 10% seasonal modulation and 2% diurnal one. We find that the observed behaviour is explained by a model including the effects associated with the variations of P and ρ. The former affects the longitudinal development of air showers while the latter influences the Molière radius and hence the lateral distribution of the shower particles. The model is validated with full simulations of extensive air showers using atmospheric profiles measured at the site of the Pierre Auger Observatory.  相似文献   

5.
The Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) gives us a chance to investigate the theoretical Neupert effect using the correlation between the thermal-energy derivative and the nonthermal energy, or the thermal energy and the integral nonthermal energy. Based on this concept, we analyze four M-class RHESSI flares on 13 November 2003, 4 November 2004, 3 and 25 August 2005. According to the evolution of the temperature [T], emission measure [EM], and thermal energy [E th], each event is divided into three phases during the nonthermal-energy input [ \frac dEnthdt\frac {\mathrm{d}E_{\mathrm{nth}}}{\mathrm{d}t} in the units of erg s−1]. Phase 1 is identified as the interval before the temperature maximum, while after the thermal-energy maximum is phase 3, between them is phase 2. We find that these four flares show the Neupert effect in phase 1, but not in phase 3. The Neupert effect still works well in the second phase, although the cooling becomes slightly important. We define the parameter μ in the relation of \fracdEthdt=m\fracdEnth(t)dt\frac{\mathrm {d}E_{\mathrm{th}}}{\mathrm{d}t}=\mu\frac{\mathrm{d}E_{\mathrm {nth}}(t)}{\mathrm{d}t} or Eth(t0)=mò0t0\fracdEnth(t)dt dtE_{\mathrm{th}}(t_{0})=\mu\int_{0}^{t_{0}}\frac{\mathrm{d}E_{\mathrm{nth}}(t)}{\mathrm{d}t}\,\mathrm{d}t when the cooling is ignored in phase 1. Considering the uncertainties in estimating the energy from the observations, it is not possible to precisely determine the fraction of the known energy in the nonthermal electrons transformed into the thermal energy of the hottest plasma observed by RHESSI. After a rough estimate of the flare volume and the assumption of the filling factor, we investigate the parameter μ in these four events. Its value ranges from 0.02 to 0.20, indicating that a small fraction (2% – 20%) of the nonthermal energy can be efficiently transformed into thermal energy, which is traced by the soft X-ray emission, and the bulk of the energy is lost possibly due to cooling.  相似文献   

6.
We present predictions for the radio pulses emitted by extensive air showers using ZHAireS, an AIRES-based Monte Carlo code that takes into account the full complexity of ultra-high energy cosmic-ray induced shower development in the atmosphere, and allows the calculation of the electric field in both the time and frequency domains. We do not presuppose any emission mechanism and our results are compatible with a superposition of geomagnetic and charge excess radio emission effects. We investigate the polarization of the electric field as well as the effects of the refractive index n and shower geometry on the radio pulses. We show that geometry, coupled to the relativistic effects that appear when using a realistic refractive index n > 1, play a prominent role on the radio emission of air showers.  相似文献   

7.
《Astroparticle Physics》2007,26(6):380-390
Ground-based arrays of imaging atmospheric Cherenkov telescopes have emerged as the most sensitive γ-ray detectors in the energy range of about 100 GeV and above. The strengths of these arrays are a very large effective collection area on the order of 105 m2, combined with excellent single photon angular and energy resolutions. The sensitivity of such detectors is limited by statistical fluctuations in the number of Cosmic-ray initiated air showers that resemble γ-ray air showers in many ways. In this paper, we study the performance of simple event reconstruction methods when applied to simulated data of the Very Energetic Radiation Imaging Telescope Array System (VERITAS) experiment. We review methods for reconstructing the arrival direction and the energy of the primary photons, and examine means to improve on their performance. For a software threshold energy of 300 GeV (100 GeV), the methods achieve point source angular and energy resolutions of σ63% = 0.1° (0.2°) and σ68% = 15% (22%), respectively. The main emphasis of the paper is the discussion of γ–hadron separation methods for the VERITAS experiment. We find that the information from several methods can be combined based on a likelihood ratio approach and the resulting algorithm achieves a γ–hadron suppression with a quality factor that is substantially higher than that achieved with the standard methods used so far.  相似文献   

8.
A54 Cosmic Ray Acceleration in Galactic Wind Shocks A71 Detection of Ultra‐High Energy Cosmic Rays and Neutrinos with LOFAR A80 Status of the gravitational‐wave detector GEO600 A87 Recent Results and Future of the MAGIC gamma‐ray telescope A92 Cosmic ray detection with the radio technique A93 Cosmic Ray Physics with IceCube A94 The resonance‐like gamma‐ray absorption processes for use in astrophysics A97 Geometry reconstruction of air shower fluorescence detectors revisited A102 Supermassive Binary Black Holes & Radio Jets A108 Muonic Component of Air Showers Measured by KASCADE‐Grande A110 Towards new frontiers: observation of photons with energies above 1018 eV A112 The IceCube Neutrino Telescope A114 The ground‐based gamma‐ray observatory CTA A116 IceCube: Recent Results and Prospects A117 Particle Physics with AMANDA and IceCube A118 Altitude dependence of fluorescence light emission by extensive air showers A120 Neutrino‐induced cascades in AMANDA & IceCube A122 Enhancement Telescopes for the Pierre Auger Southern Observatory in Argentina A123 Proton spectra from relativistic shock environments in AGN and GRBs A124 The Baikal Neutrino Telescope – Physics Results A127 Searches for point‐like sources of cosmic neutrinos with IceCube A128 The MAGIC/IceCube Target of Opportunity Programtest run A131 Supernova detection with IceCube: from low to high energy neutrinos A132 Measurement of the UHECR energy spectrum from hybrid data of the Pierre Auger Observatory A133 Extension of IceCube at Lower Energy: the Use of AMANDA as Nested Array and the Future Prospectives A135 Searching for neutrinos with the Pierre Auger Observatory A138 Search for Transient Emission of Neutrinos in IceCube A140 Acoustic Neutrino Detection in Antarctic Ice A159 AMANDA limits on the diffuse muon‐neutrino flux: physics implications A164 Investigation of the Radio Emission of Cosmic Ray Air Showers with LOPES A168 The Northern Site of the Pierre Auger Observatory A170 Shower reconstruction and size spectra with KASCADE‐Grande data A171 Neutrinos from Gamma Ray Bursts: predictions and limits from AMANDA‐II data A172 Simulation study of shower profiles from ultra‐high energy cosmic rays A174 Upper limit to the photon fraction in cosmic rays above 1019 eV from the Pierre Auger Observatory A176 Astrophysics at MeV energies A180 Study of the Cosmic Ray Composition above 0.4 EeV using the Longitudinal Profiles of Showers observed at the Pierre Auger Observatory A185 Backgrounds for UHE horizontal neutrino showers A186 The Front‐End Cards of the Pierre Auger Surface Detectors: Test Results and Performance in the Field A187 Monte Carlo Studies for MAGIC‐II A194 Measuring the proton‐air cross section from logitudinal air shower profiles A195 The UHECR energy spectrummeasured at the Pierre Auger Observatory A203 Highlights of Observations of Galactic Sources with the MAGIC telescope A207 Adesign study for a 12.5 m ∅︁ Imaging Air Cherenkov Telescope for ground‐based γ ‐ray astronomy A210 The Future of Long‐Wavelengths Radio‐Astronomy in Germany: LOFAR and GLOW A211 Online Monitoring of the Pierre Auger Observatory A216 OPTIMA‐Burst – Catching GRB Afterglows (and other Transients) with High Time Resolution A227 JEM‐EUSO mission A232 Rapid Variations in AGN: Clues on Particle Accelerators A235 Systematic search forVHEgamma‐ray emission from X‐ray bright high‐frequency peaked BL Lac objects A237 Prospects for GeV Astronomy in the Era of GLAST A241 Improvements of the energy reconstruction for the MAGIC telescope by means of analysis and Monte Carlo techniques A265 Discovery of VHE γ ‐rays from BL Lacertae with the MAGIC telescope A266 Results of two observation cycles of LS I+61°303 with the MAGIC telescope A267 Wide Range Multifrequency Observations of Northern TeV Blazars A269 Diffusive and convective cosmic ray transport in elliptical galaxies  相似文献   

9.
《Astroparticle Physics》2004,20(6):641-652
The cosmic ray primary composition in the energy range between 1015 and 1016 eV, i.e., around the “knee” of the primary spectrum, has been studied through the combined measurements of the EAS-TOP air shower array (2005 m a.s.l., 105 m2 collecting area) and the MACRO underground detector (963 m a.s.l., 3100 m w.e. of minimum rock overburden, 920 m2 effective area) at the National Gran Sasso Laboratories. The used observables are the air shower size (Ne) measured by EAS-TOP and the muon number (Nμ) recorded by MACRO. The two detectors are separated on average by 1200 m of rock, and located at a respective zenith angle of about 30°. The energy threshold at the surface for muons reaching the MACRO depth is approximately 1.3 TeV. Such muons are produced in the early stages of the shower development and in a kinematic region quite different from the one relevant for the usual Nμ−Ne studies. The measurement leads to a primary composition becoming heavier at the knee of the primary spectrum, the knee itself resulting from the steepening of the spectrum of a primary light component (p, He) of Δγ=0.7±0.4 at E04×1015 eV. The result confirms the ones reported from the observation of the low energy muons at the surface (typically in the GeV energy range), showing that the conclusions do not depend on the production region kinematics. Thus, the hadronic interaction model used (CORSIKA/QGSJET) provides consistent composition results from data related to secondaries produced in a rapidity region exceeding the central one. Such an evolution of the composition in the knee region supports the “standard” galactic acceleration/propagation models that imply rigidity dependent breaks of the different components, and therefore breaks occurring at lower energies in the spectra of the light nuclei.  相似文献   

10.
《Astroparticle Physics》2011,34(5-6):335-340
We revisit the radar echo technique as an approach to detect ultra-high energy cosmic rays (UHECR). The UHECR extensive air showers generate disk-like ionization fronts propagating with a relativistic velocity and creating fast decaying plasma. We study the reflection of a radio wave, such as the one from a radar transmitter or commercial radio and TV station, from the relativistic ionization front. The reflected wave will be frequency upshifted due to the relativistic Doppler effect and propagate almost normally to the front due to relativistic aberration. The amplitude of the reflected wave depends strongly on the front velocity and parameters (density, collision frequency) of the plasma behind the front. We develop a theory that allows one to find the reflected wave. Using this theory and typical parameters of extensive air showers, we discuss the feasibility of UHECR detection.  相似文献   

11.
We describe a method of observation for PeV–EeV τ neutrinos using Cherenkov light from the air showers of decayed τs produced by τ neutrino interactions in the Earth. Aiming for the realization of neutrino astronomy utilizing the Earth-skimming τ neutrino detection technique, highly precise determination of arrival direction is key due to the following issues: (1) clear identification of neutrinos by identifying those vertices originating within the Earth’s surface and (2) identification of very high energy neutrino sources. The Ashra detector uses newly developed light collectors which realize both a 42°-diameter field-of-view and arcminute resolution. Therefore, it has superior angular resolution for imaging Cherenkov air showers. In this paper, we estimate the sensitivity of and cosmic-ray background resulting from application of the Ashra-1 Cherenkov τ shower observation method. Both data from a commissioning run and a long-term observation (with fully equipped trigger system and one light collector) are presented. Our estimates are based on a detailed Monte Carlo simulation which describes all relevant shower processes from neutrino interaction to Cherenkov photon detection produced by τ air showers. In addition, the potential to determine the arrival direction of Cherenkov showers is evaluated by using the maximum likelihood method. We conclude that the Ashra-1 detector is a unique probe into detection of very high energy neutrinos and their accelerators.  相似文献   

12.
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13.
The Astroneu Extensive Air Shower (EAS) array comprises autonomous detection stations; each station consisting of 3 large scintillator detectors and one or more Radio Frequency (RF) antennas. The scintillator detectors of a station are able to detect showers with a low energy threshold of 20−30 TeV, at a rate of 10−20 showers per hour depending on the station geometrical layout. The RF antennas are used to detect very high energy EAS (E > 1017eV) through their radio wave emission. This work focuses in reconstructing and studying showers that have been detected synchronously by the scintillator detectors of two distant Astroneu stations. The performance of the array to detect and reconstruct the direction of such high energy (E > 5 · 1015eV) showers is evaluated by comparing the experimental measurements to the predictions of a detail Monte Carlo (MC) simulation.  相似文献   

14.
The lateral distribution of cascade particles in extensive air showers from cosmic rays with energy E0 ? 1017 eV has been studied at the Yakutsk array by the ground scintillation detectors over the period of continuous observations 1977–2017. The experimental data are compared with those computed with various models for the development of extensive air showers from the CORSIKA software package. The best agreement between the theory and experiment is observed for the QGSjet-01-d model. In the energy range (1?20)× 1017 eV there is a change in the cosmic-raymass composition from 〈lnA〉 ≈ 2.5 to the proton one.  相似文献   

15.
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16.
CODALEMA is one of the pioneer experiments dedicated to the radio detection of ultra high energy cosmic rays (UHECR), located at the radio observatory of Nançay (France). The CODALEMA experiment uses both a particle detector array and a radio antenna array. Data from both detection systems have been used to determine the ground coordinates of the core of extensive air showers (EAS). We discuss the observed systematic shift of the core positions determined with these two detection techniques. We show that this shift is due to the charge-excess contribution to the total radio emission of air showers, using the simulation code SELFAS. The dependences of the radio core shift to the primary cosmic ray characteristics are studied in details. The observation of this systematic shift can be considered as an experimental signature of the charge excess contribution.  相似文献   

17.
Cherenkov telescopes have the capability of detecting high energy tau neutrinos in the energy range of 1–1000 PeV by searching for very inclined showers. If a tau lepton, produced by a tau neutrino, escapes from the Earth or a mountain, it will decay and initiate a shower in the air which can be detected by an air shower fluorescence or Cherenkov telescope. In this paper, we present detailed Monte Carlo simulations of corresponding event rates for the VERITAS and two proposed Cherenkov Telescope Array sites: Meteor Crater and Yavapai Ranch, which use representative AGN neutrino flux models and take into account topographic conditions of the detector sites. The calculated neutrino sensitivities depend on the observation time and the shape of the energy spectrum, but in some cases are comparable or even better than corresponding neutrino sensitivities of the IceCube detector. For VERITAS and the considered Cherenkov Telescope Array sites the expected neutrino sensitivities are up to factor 3 higher than for the MAGIC site because of the presence of surrounding mountains.  相似文献   

18.
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19.
The Cherenkov radio pulse emitted by hadronic showers of energies in the EeV range in ice is calculated for the first time using full three dimensional simulations of both shower development and the coherent radio pulse emitted as the excess charge develops in the shower. A Monte Carlo, ZHAireS, has been developed for this purpose combining the high energy hadronic interaction capabilities of AIRES, and the dense media propagation capabilities of TIERRAS, with the precise low energy tracking and specific algorithms developed to calculate the radio emission in ZHS. A thinning technique is implemented to allow the simulation of radio pulses induced by showers up to 10 EeV in ice. The code is validated comparing the results for electromagnetic and hadronic showers to those obtained with GEANT4 and ZHS codes. The contribution to the pulse of other shower particles in addition to electrons and positrons, mainly protons, pions and muons, is found to be below 3% for 10 PeV and above proton induced showers. The characteristics of hadronic showers and the corresponding Cherenkov frequency spectra are compared with those from purely electromagnetic showers. The dependence of the spectra on shower energy and high-energy hadronic model is addressed and parameterizations for the radio emission in hadronic showers in ice are given for practical applications.  相似文献   

20.
We investigate the radiative and conductive cooling in the solar flare observed by RHESSI on 2005 September 13. The radiative and conductive loss energies are estimated from the observations after the flare onset. Consistent with previous findings, the cooling is increased with time, especially the radiation becomes remarkable on the later phase of flare. According our method, about half of thermal energy is traced by RHESSI soft X-rays, while the other half is lost by the radiative (∼38%) and conductive (∼9%) cooling at end of the hard X-rays in this event. The nonthermal energy input of P nth (inferred from RHESSI hard X-ray spectrum) is not well correlated with the derivative of thermal energy of \fracdEthdt\frac{\mathrm{d}E_{\mathrm{th}}}{\mathrm{d}t} (required to radiate the RHESSI soft X-ray flux and spectrum) alone. However, after consideration the radiation and conduction, a high correlation is obtained between the derivative of total thermal energy ( \fracdEth+Erad+Econddt\frac{\mathrm{d}E_{\mathrm{th}}+E_{\mathrm{rad}}+E_{\mathrm{cond}}}{\mathrm{d}t}) and nonthermal energy input (P nth) from the flare start to end, indicating the relative importance of conductive and direct radiative losses during the solar flare development. Ignoring the uncertainties to estimate the energy from the observations, we find that about ∼12% fraction of the known energy is transferred into the thermal energy for the 2005 September 13 flare.  相似文献   

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