Universal lateral distribution of energy deposit in air showers and its application to shower reconstruction

The light intensity distribution in a shower image and its implications to the primary energy reconstructed by the fluorescence technique are studied. Based on detailed CORSIKA energy deposit simulations, a universal analytical formula is derived for the lateral distribution of light in the shower image and a correction factor is obtained to account for the fraction of shower light falling into outlying pixels in the detector. The expected light profiles and the corresponding correction of the primary shower energy are illustrated for several typical event geometries. This correction of the shower energy can exceed 10%, depending on shower geometry.     

Application of CORSIKA Simulation Code to Study Lateral and Longitudinal Distribution of Fluorescence Light in Cosmic Ray Extensive Air Showers

In this paper, we used CORSIKA code to understand the characteristics of cosmic ray induced showers at extremely high energy as a function of energy, detector distance to shower axis, number, and density of secondary charged particles and the nature particle producing the shower. Based on the standard properties of the atmosphere, lateral and longitudinal development of the shower for photons and electrons has been investigated. Fluorescent light has been collected by the detector for protons, helium, oxygen, silicon, calcium and iron primary cosmic rays in different energies. So we have obtained a number of electrons per unit area, distance to the shower axis, shape function of particles density, percentage of fluorescent light, lateral distribution of energy dissipated in the atmosphere and visual field angle of detector as well as size of the shower image. We have also shown that location of highest percentage of fluorescence light is directly proportional to atomic number of elements. Also we have shown when the distance from shower axis increases and the shape function of particles density decreases severely. At the first stages of development, shower axis distance from detector is high and visual field angle is small; then with shower moving toward the Earth, angle increases. Overall, in higher energies, the fluorescent light method has more efficiency. The paper provides standard calibration lines for high energy showers which can be used to determine the nature of the particles.     

One-dimensional hybrid approach to extensive air shower simulation

An efficient scheme for one-dimensional extensive air shower simulation and its implementation in the program conex are presented. Explicit Monte Carlo simulation of the high-energy part of hadronic and electro-magnetic cascades in the atmosphere is combined with a numeric solution of cascade equations for smaller energy sub-showers to obtain accurate shower predictions. The developed scheme allows us to calculate not only observables related to the number of particles (shower size) but also ionization energy deposit profiles which are needed for the interpretation of data of experiments employing the fluorescence light technique. We discuss in detail the basic algorithms developed and illustrate the power of the method. It is shown that Monte Carlo, numerical, and hybrid air shower calculations give consistent results which agree very well with those obtained within the corsika program.     

Simulations of a giant hybrid air shower detector

We have used Monte Carlo simulations to investigate the capabilities of a giant air shower observatory designed to detect showers initiated by cosmic rays with energies exceeding 10¹⁹ eV. The observatory is to consist of an array of detectors that will characterise the air shower at ground level, and optical detectors to measure the fluorescence light emitted by the shower in the atmosphere. Using these detectors together in a ‘hybrid’ configuration, we find that precise geometrical reconstruction of the shower axis is possible, leading to excellent resolution in energy. The technique is also shown to provide very good reconstruction below 10¹⁹ eV, at energies where the ground array is not fully efficient.     

Geminid Meteor shower activity 2003–2005 as observed by Gadanki radar

The distribution of meteor signals reflected from a backscatter radar is considered according to their duration. This duration time (T) is used to classify the meteor echoes and to calculate the mass index (S) of different meteoroids of shower plus sporadic background. Observational data on particle size distribution of the Geminid meteor shower are very scarce, particularly at low latitudes. In this paper the observational data from Gadanki radar (13.46°N, 79.18°E) have been used to determine the particle size distribution and the number density of meteoroids inside the stream of the Geminid meteor shower. The mean variation of meteor number density across the stream has been determined for three echo duration classes, T<0.4, T=0.4–1 and T>1 s. We are more interested in the appearance of echoes of various durations and therefore meteors of various masses in order to understand more on the filamentary structure of the stream. It is observed that the faint particle flux peaks earlier than the larger particles. We found a decreasing trend in the mass index values from the day of peak activity to the next observation days. The mass index profile was found to be U-shaped with a minimum value near the time of peak activity. The observed minimum s values are 1.64±0.05 and 1.65±0.04 in the years 2003 and 2005, respectively. The activity of the shower indicates the mass segregation of meteoroids inside the stream. Our results are best comparable with the “scissors” structure model of the meteoroid stream formation of Ryabova [2007. Mathematical modeling of the Geminid meteoroid stream. Mon. Not. R. Astron. Soc. 375, 1371–1380] by considering the asteroid 3200 Phaethon as an extinct comet.     

Absolute photometric calibration of large aperture optical systems

A method of absolute calibration for the air shower fluorescence detectors of the Pierre Auger Observatory is presented, along with preliminary results from prototype equipment. A 2.5 m diameter light source uniformly illuminated by ultra-violet light emitting diodes is calibrated and mounted at the detector aperture. The resulting end-to-end measurement provides a 7% absolute photon calibration at a wavelength of 375 nm.     

Comet Tempel-Tuttle and the Leonid meteors

The distribution of dust surrounding periodic comet Tempel-Tuttle has been mapped by analyzing the associated Leonid meteor shower data over the 902–1969 interval. The majority of dust ejected from the parent comet evolves to a position lagging the comet and outside the comet's orbit. The outgassing and dust ejection required to explain the parent comet's deviation from pure gravitational motion would preferentially place dust in a position leading the comet and inside the comet's orbit. Hence it appears that radiation pressure and planetary perturbations, rather than ejection processes, control the dynamic evolution of the Leonid particles. Significant Leonid meteor showers are possible roughly 2500 days before or after the parent comet reaches perihelion but only if the comet passes closer than 0.025 AU inside or 0.010 AU outside the Earth's orbit. Although the conditions in 1998–1999 are optimum for a significant Leonid meteor shower, the event is not certain because the dust particle distribution near the comet is far from uniform. As a by-product of this study, the orbit of comet Tempel-Tuttle has been redetermined for the 1366–1966 observed interval.     

A parameterization for the radio emission of air showers as predicted by CoREAS simulations and applied to LOFAR measurements

Measuring radio emission from air showers provides excellent opportunities to directly measure all air shower properties, including the shower development. To exploit this in large-scale experiments, a simple and analytic parameterization of the distribution of the radio signal at ground level is needed. Data taken with the Low-Frequency Array (LOFAR) show a complex two-dimensional pattern of pulse powers, which is sensitive to the shower geometry. Earlier parameterizations of the lateral signal distribution have proven insufficient to describe these data. In this article, we present a parameterization derived from air-shower simulations. We are able to fit the two-dimensional distribution with a double Gaussian, requiring five fit parameters. All parameters show strong correlations with air shower properties, such as the energy of the shower, the arrival direction, and the shower maximum. We successfully apply the parameterization to data taken with LOFAR and discuss implications for air shower experiments.     

Possible Detection of GEMINID 2007 Meteor Shower During Day-Time from VLF Radiation Spectra

The results of day-time detection of GEMINID 2007 meteor shower from dynamic VLF radiation spectra in Tripura (23.50° N, 91.25° E), India, is presented here. The field experiments were performed during 12–17th December, 2007 inside Tripura University campus located at a hilly place in the North-Eastern part of India. A well calibrated software VLF receiver was used to perform the field experiments. Analyses of data reveal an hourly average rate of the shower around 50. The VLF emissions lie in the range from 8 kHz to 13 kHz which is 10 to 15 times higher than previous reports. The mean duration of each VLF emission calculated from dynamic spectra is found to be 6 s and the mean bandwidth is 3.6 kHz. The temporal variation of VLF emission duration and bandwidth of VLF radiation is also studied. The results strongly support the fact that VLF electromagnetic waves are produced during the passage of meteors in the atmosphere. The experiment also makes the study of dynamic VLF spectra as a strong tool to detect low intensity meteor shower during daytime.     

超高能宇宙线大气簇射平均纵向发展曲线的测量（英文）

利用HiRes宇宙线实验的观测数据,通过扣除测量信号中的切仑科夫光成份,测量了广延大气簇射的纵向发展曲线。把所有的纵向发展曲线归一并且平均,获得平均纵向发展曲线。根据所得曲线,检验了3个簇射模型,它们都能较好地描述纵向发展曲线。如果利用高斯函数来描述簇射的纵向发展曲线,发现纵向发展曲线的宽度（σ）与簇射发展最大的深度有一定的关联,而且该参量从1017eV到1020 eV能量范围内几乎保持不变。另外还对平均纵向发展曲线的不确定性进行了讨论。     

Do comets have chondrules and CAIs? Evidence from the Leonid meteors

Abstract— Chondrules, silicate spheres typically 0.1 to 1 mm in diameter, are the most abundant constituents in the most common meteorites falling on Earth, the ordinary chondrites. In addition, many primitive meteorites have calcium‐aluminum‐rich inclusions (CAIs). The question of whether comets have chondrules or CAIs is relevant to understanding what the interior of a comet is like and what a cometary meteorite might be like. In addition, one prominent model for forming chondrules and CAIs, the X‐wind model, predicts their presence in comets, while most other models do not. At present, the best way to search for chondrules and CAIs in comets is through meteor showers derived from comets, in particular, the Leonid meteor shower. Evidence potentially could be found in the overall mass distribution of the shower, in chemical analyses of meteors, or in light curves. There is no evidence for a chondrule abundance in the Leonid meteors similar to that found in chondritic meteorites. There is intriguing evidence for chondrule‐ or CAI‐sized objects in a small fraction of the light curves, but further work is required to generate a definitive test.     

Comparison of simulated longitudinal profiles of hadronic air showers with MASS2 balloon data

The KASKADE and CORSIKA air shower generators are compared to the data collected by MASS2 balloon experiment in 1991. The test of longitudinal profile for proton, helium and muon flux production provide good constraints on these air shower generators. KASKADE and CORSIKA especially with the new simulator UrQMD for low energies are found to fit these data well. This study is limited to a comparison of longitudinal profiles and therefore does not provide constraints on the overall shower development.     

Interpretation of the time structure of the EAS disc measured by the GREX/COVER_PLASTEX experiment

Simulation results for the time structure of the extensive air shower disc are presented and compared with data from the GREX/COVER_PLASTEX experiment. The distribution of the arrival times at various distances from the shower core and the contributions from the secondary particles to the shape of the distribution are described. The main parameters of the distribution, the mean time of arrival τ and the standard deviation σ, reflect the shower disc profile and thickness. The dependence of the shower profile and thickness on the energy and mass of the primary particle initiating the shower as well as on its inclination angle is discussed. The influence of the experimental conditions on the disc profile and thickness measured by the GREX/COVER_PLASTEX experiment is analysed and a parametrization of the average profile and thickness is given.     

Activities of Parent Comets and Related Meteor Showers

The activity of a meteor shower is thought to be proportional to the activities through time of the parent comet. Recent applications of the dust trail theory provide us not only with a new method to forecast the occurrences and intensities of shower activities, but it is also offers a new approach to explore the history of past activities of the parent comet by retro-tracking its associated meteor showers. We introduce the result of an effort for relating meteor shower activities to the parent comet activities for which we chose the October Draconids and comet 21P/Giacobini-Zinner in this paper.     

Arietid Meteor Orbits Measurements

The Arietid meteor shower is one of the strongest of the year. The origin of this daytime shower is unknown; the orbit is therefore of great interest, since an accurate orbit distribution is needed to integrate the shower backward in time to test associations with comets or asteroids. The orbital parameters of the Arietid shower as a function of time, with errors, have been generated using 415 radar orbits gathered at the CMOR facility in Tavistock, Canada.     

Time structure of the extensive air shower front

The GREX/COVER_PLASTEX experiment has measured the temporal and spatial fine structure of the EAS disc at sea level in a new and original way, using resistive plate counter detectors for direct measurements of the arrival time of each particle crossing the detector. Data were taken at EAS core distances up to 100 m for shower size N > 10⁵ (PeV energy range). Arrival times of shower particles were measured with nanosecond accuracy. More than 450000 air shower events have been included in this analysis.     

Cherenkov τ shower earth-skimming method for PeV–EeV ντ observation with Ashra

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.