Radio emission of extensive air showers as a method for detecting ultra-high energy cosmic rays

Recording radio emission from extensive air showers (EASs) is considered now as a new promising method for detecting ultra-high energy (E ₀ > 5 × 10¹⁶ eV) cosmic rays. The results of calculation of EAS radio emission at frequencies from 40 to 80 MHz in the EAS energy range E ₀ = 10¹⁴–10¹⁷ eV are reported here, and the possibilities of determining EAS parameters from the radio emission lateral distribution are discussed.     

Radio emission from extensive air showers as a method for cosmic-ray detection

At the present time, radio emission from extensive air showers (EASs) is being considered as a new promising method for detecting cosmic rays of energy in the region E ₀ > 5 × 10¹⁶ eV. Radio emission from an EAS whose development is simulated by the Monte Carlo method is calculated here. The field of radio emission from an EAS is calculated on the basis of two representations of a shower: that as a set of individual particles and that as a continuous set of currents. The sensitivity of radio emission to EAS parameters in the frequency range 10–100 MHz is investigated. The results can be used to analyze experiments that being presently performed (CODALEMA and LOPES) and those that are being planned for the future.     

Spatial distribution of EAS radio emission at 32 MHz

The results of the reprocessing of the experimental data on radio emission from extensive air showers (EAS) earlier obtained at the EAS facility (Moscow State University) are reported. The maximum depth distribution of showers is found from analysis of the width of the spatial distribution of radio emission. The average maximum depth is X _max = 655 ± 8 g/cm² for the primary particle energy E ₀ ～ (3–4) × 10¹⁷ eV. The normalized field strength at E ₀ = 10¹⁷ eV is 3.2 ± 0.6 and 2.8 ± 0.4 μV/(m MHz) at distances of 50 and 100 m from the axis, respectively. The accuracy of E ₀ determination from the radio emission field strength at 50 m from the axis is about 20%.     

Radio signals from extensive air showers with the energies <Emphasis Type="Italic">E</Emphasis> <Subscript>0</Subscript> ≥ 10<Superscript>19</Superscript> eV according to data from the Yakutsk extensive air shower array

A radio instrument and results obtained from the measurements of the 32-MHz radio signal from particles of extensive air showers (EASs) with energies E₀ ≥ 1×10¹⁹ eV are reported in brief. The data were obtained at the Yakutsk EAS array in 1987–1989 (the first series of measurements) and in 2009–2014 (new series of measurements). The radio signal from EASs with energies above 10²⁰eV was detected at the Yakutsk EAS array for the first time, including the shower with the record energy of ~2×10²⁰ eV for the Yakutsk EAS array.     

Detection and analysis of radio pulses from extensive air showers

Radio pulses from extensive air showers (EAS) at 30, 44, and 60 MHz frequencies have been studied, using wide band broad-side arrays of half-wave dipole antenna systems. The experimental results support the theoretical prediction that the field strength of radio emission depends on the shower size. An asymmetry has been noticed in the pulse height distributions of radio pulses detected by North-South and East-West directed arrays. These observations are in agreement with the theory that the charge separation mechanism is predominant in generating radio pulses from EAS and radio emission is polarised in the East-West direction. Experimental data are compared with those of earlier workers.     

Microscopic approach to the calculation of extensive air shower radio emission

Bulletin of the Lebedev Physics Institute - Abstract—Within the kinetic theory of extensive air shower (EAS), an approach to calculating electron charge excess radio emission is formulated....     

Mass composition of 1017- to 1018-eV primary cosmic rays according to data on the lateral distribution of radio emission from extensive air showers

Experimental data obtained for the lateral distribution of radio emission from extensive air showers (EAS) at the array of Moscow State University (30?C34 MHz) and the LOPES array (40?C80 MHz) were comparedwith the results of calculations performed within amicroscopic approach based on aMonte Carlo simulation of EAS (CORSIKA code). The same experimental data were used to reconstruct the distribution of the depth of the EAS maximum at cosmic-ray energies in the range of 1017?C1018 eV. The energy dependence of the depth of the EAS maximum was constructed for the case of data from the LOPES array, and the mass composition of cosmic rays was estimated for this case. From the resulting dependences, it follows that the mass composition shows a trend toward becoming lighter in the energy range being considered     

Strongly Beamed,Polarized Radio Emission from CU Virginis

We propose the plasma mechanism of generation of the strongly beamed, fully polarized radio emission from a chemically peculiar star CU Vir observed with VLA at 1.4 GHz in June 2, 6, and 9, 1998. The radio emission arises from the Rayleigh scattering of longitudinal waves excited near the upper-hybrid resonance due to the loss-cone instability on suprathermal electrons in the magnetosphere of CU Vir. It is shown that the nonlinear stimulated scattering of upper-hybrid waves and the regular refraction of radiowaves in the stellar corona are the main factors forming the angular pattern of the radio emission. As the result, the angular pattern of the radiation of CU Vir narrows to 3^°-10^°.     

Simulations of radio emission from ultrahigh-energy extensive air showers

The radio emission from extensive air showers with energies up to 10¹⁷ eV has been calculated. The calculated lateral distribution of the radio emission is in good agreement with the LOPES-10 experimental data.     

Low-frequency radio emission induced by the coherent magneto-bremsstrahlung of charged particles of an extensive air shower

A previously unknown coherent low-frequency (0<ν<50 kHz) component of radio emission of an extensive air shower in the geomagnetic field is reported. This type of emission induces a high-intensity field (∼200 μV/m MHz at a distance of 100 km from the shower axis). This emission mechanism is believed to be responsible for the previously observed high-intensity radio emission of the shower at low frequencies. The possibility of radio detection of ultrahigh-energy (W ₀>10²¹ eV) cosmic rays is considered.     

Is it possible to determine the chemical composition of cosmic rays in the “LORD” lunar experiment?

The results of the simulation of cascade radio emission from ultrahigh-energy cosmic rays in the LORD lunar experiment using circularly polarized antennas are presented. It is shown that based on the characteristics of radio emission caused by cascades from protons and iron nuclei in lunar regolith and escaped into vacuum it is impossible to distinguish these cascades in the primary energy region above 10²⁰ eV.     

BL Lac天体的γ射线和射电辐射的统计特性

给出了一个带有射电5.0GHz,8.4GHz 和γ射线辐射流量密度的22个γ噪BL Lac天体的样本,研究了它们在1GeV处的γ射线辐射流量密度最大值、平均值及最小值与射电5.0GHz,8.4GHz辐射流量之间的可能关系.结果表明：1）射电5.0GHz,8.4GHz辐射与γ射线辐射在低态时没有相关,但在高态和平均态时都存在较强的相关,最大相关系数r=0.85,置信度均好于10^-4;2）γ射线谱指数和射电谱指数之间也有一个弱相关关系存在.因此,认为γ射线的辐射主要是同步自康普顿辐射. 关键词： BL Lac天体 γ射线 射电辐射 谱指数     

Evidences for strangelet presence in Primary Cosmic Rays

The recent results of experiment “Hadron” which was carried out at Tien-Shan Station in 1985–91 are discussed. The combining of extensive air shower array and large emulsion chamber has permitted to receive new experimental data on sharp scaling violation at energies ≥10¹⁵ eV (1 PeV). Data show strong hardness of hadron energy spectra in EAS cores for primary energies ≥3 PeV. The EAS electron lateral distribution function also exhibits the same energy dependence in interval 1–10 PeV. The EAS muon component also shows changing of energy dependence at 10 PeV. These data permit to discuss a model in which sharp scaling violation is connected with EAS spectrum “knee”. A hypothesis of strangelet presence in PCR is discussed. The flow of strangelet component is estimated to be about 1 m^?2 · year^?1.     

Methodological Issues of Gamma-Ray and Neutrino Searches at the Yakutsk Array

The method used to perform searches for extensive air showers (EAS) generated by neutral particles, such as high-energy gamma rays and astrophysical neutrinos, and the results of such searches are presented. A comprehensive analysis of relevant data, including those on EAS electrons, muons, and Cherenkov light and their time responses in scintillation and Cherenkov detectors, is performed for this purpose. An upper limit on the gamma-ray flux at the energies of 3 × 10¹⁸, 10¹⁹, and 3 × 10¹⁹ eV is set. A multivariate analysis of EAS properties of neutrino-induced air showers does not reveal neutrino-induced showers.     

Amplification and nonlinear modification of runaway breakdown

The astonishing natural phenomenon of narrow bipolar pulses (NBP) is an isolated discharges in thunderstorms at tropopause heights (10–20 km) that generates enormously powerful radio emission but lasts only a few microseconds. The theory of this phenomenon based on runaway breakdown is elaborated. At such high heights extensive atmospheric shower (EAS) become well developed only if the energetic cosmic ray particle momentum is directed close to the horizon. For these conditions the runaway breakdown–extensive atmospheric shower (RB–EAS) discharge amplified strongly what lead to the effective diminishing of thundercloud electric field and results in nonlinear saturation of the discharge current. A reasonable agreement of the theory with NBP observations is demonstrated.     

A Method for Estimation of the Parameters of the Primary Particle of an Extensive Air Shower by a High-Altitude Detector

A method for estimation of the parameters of the primary particle of an extensive air shower (EAS) by a high-altitude detector complex is described. This method was developed as part of the Pamir-XXI project. The results may be useful for other high-altitude projects and the EAS method in general. The specific configurations of optical detectors for Cherenkov EAS radiation and charged-particle detectors, the methods for data processing, and the attainable accuracy of reconstruction of parameters of primary particles (energy, direction, mass/type) are presented. The results primarily cover optical detectors that are suitable for studying EASs from primary nuclei in the range of energies E⁰ = 100 TeV–100 PeV and showers from primary γ-quanta with energies of E_γ ≥ 30 TeV. Grids of charged-particle detectors designed to determine the EAS direction and energy in the E⁰ = 1 PeV–1 EeV range are also considered. The obtained accuracy estimates are the upper limits of the actual experimental accuracies.     

The Renaissance of Radio Detection of Cosmic Rays

Nearly 50 years ago, the first radio signals from cosmic ray air showers were detected. After many successful studies, however, research ceased not even 10 years later. Only a decade ago, the field was revived with the application of powerful digital signal processing techniques. Since then, the detection technique has matured, and we are now in a phase of transition from small-scale experiments accessing energies below 10 ¹⁸ eV to experiments with a reach for energies beyond 10 ¹⁹ eV. We have demonstrated that air shower radio signals carry information on both the energy and the mass of the primary particle, and current experiments are in the process of quantifying the precision with which this information can be accessed. All of this rests on solid understanding of the radio emission processes which can be interpreted as a coherent superposition of geomagnetic emission, Askaryan charge-excess radiation, and Cherenkov-like coherence effects arising in the density gradient of the atmosphere. In this article, I highlight the “state of the art” of radio detection of cosmic rays and briefly discuss its perspectives for the next few years.     

Testing calculation results of Cherenkov radiation flux from extensive air showers using CORSIKA

This paper presents computational results of the spatiotemporal characteristics of Cherenkov light from particles of extensive air showers (EASs) induced by ultra-high-energy cosmic rays (UHECR). These results were obtained by simulating EAS events with the CORSIKA software package. Events were induced by UHECR particles, i.e., protons and iron nuclei with energies of 10¹⁵ and 10¹⁶ eV. The computational results were compared with experimental data obtained at the Yakutsk EAS array; possible causes of the discrepancy between them are discussed.     

Extragalactic electromagnetic cascades as a possible instrument for the study of background radio emission

We analyzed the diffuse gamma-ray emission generated in the interactions between cosmic rays of ultrahigh energies and the background radiation in extragalactic space. The intensity of gamma-ray emission was calculated within a simplified model for energies E ≈ 10¹⁴ eV in different assumptions concerning the cosmic ray sources with the use of different estimates of nonthermal background radiation. It was shown that the gamma-ray radiation intensity in this energy range depends on the background radio emission and that under different assumptions concerning the radio background it can differ tens of times. It was concluded that gamma-ray emission can serve as a test for the models of background radio-frequency radiation.     

Radio-frequency component of transient radiation of an extensive air shower

The mechanism of radio emission induced by the transient radiation of oppositely charged particles from an extensive air shower in the geomagnetic field was studied for the first time. For showers with an energy of ∼10²² eV, the electric field strength at a distance of 500 km from the shower axis was found to be 60 μV/mMHz. Such showers attain their maximum at sea level. The spectral intensity of emission is maximum at frequencies of about 1 MHz (at these frequencies, the intensity of atmospheric disturbances is minimum). These specific features of radio emission can be used in experiments for radio detection of high-energy cosmic rays. An experimental setup of such detection is suggested.