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Author: James Bourbeau Publisher: ISBN: Category : Languages : en Pages : 141
Book Description
Since the discovery of cosmic rays over one hundred years ago, many experiments have studied their properties. However, a definitive answer to the questions of where cosmic rays originate and how they are produced is still not known. Over the last several decades, a much more detailed understanding of high energy cosmic rays has begun to materialize. In particular, the cosmic-ray energy spectrum, with its transitions at 3 PeV (the "knee") and 3 EeV (the "ankle"), has been extensively investigated. Based on magnetic confinement arguments, it's generally believed that the energy range between the knee and ankle is where the transition from Galactic to extragalactic sources of cosmic rays. The ability to distinguish between high energy cosmic rays of different composition and study the relative mass abundances of cosmic rays in this transition region can provide invaluable insight in answering the open questions surrounding the origins of cosmic rays. This work focuses on measuring the composition-resolved cosmic-ray energy spectrum at and above the all-particle knee using one year of data collected by the IceCube Observatory. Sepcifically, we focus on making a two mass group spectrum measurement from 10^6.4 GeV to 10^7.8 GeV. The first mass group, referred to as the "light" mass group, is modeled using proton and helium cosmic rays, while the second, "heavy" mass group, is modeled using oxygen and iron cosmic rays. We observe a clear softening of the light spectrum near 3 PeV, while the energy spectrum for the heavy mass group follows a power-law like structure with a spectral index of ~2.7 throughout the entire energy range considered. The observed transition from a primarily light to a heavy-dominant spectrum takes place near 10^7.1 GeV. This feature is characteristic of a potential rigidity-dependent cutoff, or Peters cycle. The change in relative mass abundance could also indicate a possible transition in the source population of cosmic rays. In addition, a study to determine whether or not the light, heavy, or all-particle cosmic-ray energy spectra vary as a function of arrival direction is also presented. This marks the first time an analysis of this kind has been conducted using the IceCube Observatory. No statistically significant spectrum deviations were observed. The results from this analysis can be used to set a limit on the range of possible spectral deviations.
Author: James Bourbeau Publisher: ISBN: Category : Languages : en Pages : 141
Book Description
Since the discovery of cosmic rays over one hundred years ago, many experiments have studied their properties. However, a definitive answer to the questions of where cosmic rays originate and how they are produced is still not known. Over the last several decades, a much more detailed understanding of high energy cosmic rays has begun to materialize. In particular, the cosmic-ray energy spectrum, with its transitions at 3 PeV (the "knee") and 3 EeV (the "ankle"), has been extensively investigated. Based on magnetic confinement arguments, it's generally believed that the energy range between the knee and ankle is where the transition from Galactic to extragalactic sources of cosmic rays. The ability to distinguish between high energy cosmic rays of different composition and study the relative mass abundances of cosmic rays in this transition region can provide invaluable insight in answering the open questions surrounding the origins of cosmic rays. This work focuses on measuring the composition-resolved cosmic-ray energy spectrum at and above the all-particle knee using one year of data collected by the IceCube Observatory. Sepcifically, we focus on making a two mass group spectrum measurement from 10^6.4 GeV to 10^7.8 GeV. The first mass group, referred to as the "light" mass group, is modeled using proton and helium cosmic rays, while the second, "heavy" mass group, is modeled using oxygen and iron cosmic rays. We observe a clear softening of the light spectrum near 3 PeV, while the energy spectrum for the heavy mass group follows a power-law like structure with a spectral index of ~2.7 throughout the entire energy range considered. The observed transition from a primarily light to a heavy-dominant spectrum takes place near 10^7.1 GeV. This feature is characteristic of a potential rigidity-dependent cutoff, or Peters cycle. The change in relative mass abundance could also indicate a possible transition in the source population of cosmic rays. In addition, a study to determine whether or not the light, heavy, or all-particle cosmic-ray energy spectra vary as a function of arrival direction is also presented. This marks the first time an analysis of this kind has been conducted using the IceCube Observatory. No statistically significant spectrum deviations were observed. The results from this analysis can be used to set a limit on the range of possible spectral deviations.
Author: Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Anisotropy in the cosmic-ray arrival direction distribution has been well documented over a large energy range, but its origin remains largely a mystery. In the TeV to PeV energy range, the galactic magnetic field thoroughly scatters cosmic rays, but anisotropy at the part-per-mille level and smaller persists, potentially carrying information about nearby cosmic-ray accelerators and the galactic magnetic field. The IceCube Neutrino Observatory was the first detector to observe anisotropy at these energies in the Southern sky. This work uses 318 billion cosmic-ray induced muon events, collected between May 2009 and May 2015 from both the in-ice component of IceCube as well as the surface component, IceTop. The observed global anisotropy features large regions of relative excess and deficit, with amplitudes on the order of $10^{-3}$. While a decomposition of the arrival direction distribution into spherical harmonics shows that most of the power is contained in the low-multipole ($\ell \leq 4$) moments, higher-multipole components are found to be statistically significant down to an angular scale of less than $10^{\circ}$, approaching the angular resolution of the detector. Above 100\,TeV, a change in the topology of the arrival direction distribution is observed, and the anisotropy is characterized by a wide relative deficit whose amplitude increases with primary energy up to at least 5\,PeV, the highest energies currently accessible to IceCube with sufficient event statistics. No time dependence of the large- and small-scale structures is observed in the six-year period covered by this analysis within statistical and systematic uncertainties. Analysis of the energy spectrum and composition in the PeV energy range as a function of sky position is performed with IceTop data over a five-year period using a likelihood-based reconstruction. Both the energy spectrum and the composition distribution are found to be consistent with a single source population over declination bands. This work represents an early attempt at understanding the anisotropy through the study of the spectrum and composition. The high-statistics data set reveals more details on the properties of the anisotropy, potentially able to shed light on the various physical processes responsible for the complex angular structure and energy evolution.
Author: Zigfried Hampel-Arias Publisher: ISBN: Category : Languages : en Pages : 346
Book Description
Over the past two decades, a more detailed understanding of TeV-scale cosmic rays has emerged which appears to deviate from the isotropic, single power law description of the cosmic ray flux. This may be the result of the distribution of sources within the Galaxy, changes in source spectra, effects from the propagation of cosmic rays from their sources to Earth, or a combination of the three. Supernova remnants are thought to be the most likely source of Galactic cosmic rays, providing a natural power law source spectrum with sufficient power to generate the observed cosmic ray energy density. Yet, recent results from balloon-borne experiments hint at a possible change in the spectral index between 20−50 TeV. These direct detection apparatuses provide the most precise measurements of the cosmic ray flux up to ~30 TeV, beyond which they are limited by the combined effects of their physical dimensions, runtime durations, and a rapidly decreasing flux. Above ~100 TeV, the spectrum has been measured by ground based air shower arrays, with typical systematic uncertainties of order 10%. Despite having the combined measurements from various experimental techniques, their different energy scales and systematics imply that identifying finer structure between 10−100 TeV requires a single experimental method to span the entire range. Furthermore, as the nearest potential source is hundreds of parsecs away and the Larmor radius of TeV scale charged cosmic rays in the Galaxy is of order 10−3 parsecs, the previously observed anisotropy in arrival directions of cosmic rays is unexpected. In order to attain the statistical power necessary to observe TeV cosmic ray anisotropy at the 10−3 level and below, the long data taking periods required are only attainable by air shower arrays. This thesis presents a measurement of the cosmic ray energy spectrum and the energy dependence of the anisotropy on small scales O(10°) using data from the High Altitude Water Cherenkov (HAWC) Observatory, an air-shower array located near Puebla, Mexico that is sensitive to gamma rays and cosmic rays at TeV energies. The analyses in this work comprise data taking periods of order 1 yr containing ~1010 events. An analysis of the cosmic ray Moon shadow is first presented as a verification of the angular resolution and energy scale of the detector. Next, a measurement of the all-particle cosmic ray energy spectrum from 10−500 TeV is shown, with an indication of structure deviating from a single power law. The final results presented in this work show an improved spectral measurement of a particular region of cosmic ray excess at the 10−4 level, previously observed both in HAWC and in other experiments.
Author: Emily Dvorak Publisher: ISBN: Category : Black hole Languages : en Pages : 372
Book Description
The IceCube is the world largest neutrino observatory located at the geographic South Pole. It consists of two components, the 1 km2 surface array IceTop, and 1 km3 InIce array. The main focus of the IceCube is neutrino astronomy and studying the physics of the neutrinos. IceCube also measures the direction, energy and mass composition of cosmic ray particles in the energy range between several hundred TeV (~1014 eV) and a few EeV (~1018 eV), the most enigmatic Galactic-to-extragalactic transition region. One unique advantage of the cosmic ray study with IceCube data comes from the fact that IceCube measures both the surface particles (with IceTop) and high energy muons (with the InIce array) in extensive air showers produced by cosmic rays. Previous cosmic ray studies are mainly done with the data from IceTop only, which are limited by the quality of cosmic ray reconstruction, and the number of high energy events. This work aims to improve the cosmic ray reconstructions in two ways. The first is to investigate and solve the angular resolution problem that occurred in the reconstruction of cosmic rays at high energies. The second is to develop a new cosmic ray reconstruction that uses data from both the IceTop and InIce arrays simultaneously. The first work significantly improves the direction reconstruction of cosmic rays. The second achieves, for the first time, a three-dimensional reconstruction of cosmic ray events in IceCube. It not only increases the number of events for physics study at high energies but also provides new parameters that may improve the accuracy of the measurement of cosmic ray primary energy and composition. The new reconstruction was also applied to data for a test analysis that uses machine learning techniques, which provides insights into future science analyses.
Author: Publisher: ISBN: Category : Languages : en Pages : 314
Book Description
Over the past two decades, ground-based measurements of the arrival directions of TeV cosmic rays have revealed an unexpected anisotropy. Multiple detectors have recorded fluxes above all-sky averages to high statistical significance for features at large (about 180°) and small (about 5°) angular sizes. Likely sources of high-energy cosmic rays are no closer than about 100 pc, about 100,000 Larmor radii for a TeV proton in typical interstellar magnetic fields of order several microGauss. This thesis outlines methods to search for signals in cosmic-ray arrival directions on data from the High-Altitude Water Cherenkov (HAWC) Observatory -- an extended air shower detector array in Puebla, Mexico, sensitive to gamma rays and cosmic rays at TeV energies. The detector is currently under construction, but data acquisition with the partially deployed detector started in 2013. An analysis of the cosmic-ray arrival direction distribution based on 86 billion events recorded between June 2013 and July 2014 shows anisotropy at the 10^(-4) level on angular scales of about 10°. The HAWC cosmic-ray sky map exhibits three regions of significantly enhanced cosmic-ray flux; two of these regions were first reported by the Milagro experiment. A third region coincides with an excess recently reported by the ARGO-YBJ experiment. An angular power spectrum analysis of the sky shows that all terms up to l=15 contribute significantly to the excesses. Large angular scales (>60°) are also considered, but the results are still preliminary as they are contaminated with non-sidereal signals which cancel for integer years of continuous data. An analysis of the cosmic-ray Moon shadow is shown to demonstrate the angular resolution and energy scale of the data set and to evaluate part of the analysis technique.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
We report the first observation of an anisotropy in the arrival direction of cosmic rays with energies in the multi TeV region in the Southern sky using data from the IceCube detector. Between June 2007 and March 2008, the partially-deployed IceCube detector was operated in a configuration with 1320 digital optical sensors distributed over 22 strings at depths between 1450 and 2450 meters inside the Antarctic ice. IceCube is a neutrino detector, but the data are dominated by a large background of cosmic ray muons. Therefore, the background data are suitable for high-statistics studies of cosmic rays in the Southern sky. The data include 4.3 billion muons produced by downgoing cosmic ray interactions in the atmosphere; these events were reconstructed with a median angular resolution of 3 degrees and a median energy of ~;; 20 TeV. Their arrival direction distribution exhibits an anisotropy in right ascension with a first harmonic amplitude of (6.4 +- 0.2 stat. +- 0.8 syst.) x 10-4.
Author: Andres Alberto Medina Publisher: ISBN: Category : Astrophysics Languages : en Pages : 144
Book Description
The origin of cosmic rays has been an open problem for over a century. By measuring and modeling the energy spectrum and mass composition we can provide information towards solving this problem. The energy spectrum in particular has several features that hold key information to the propagation and sources of cosmic rays. The energy spectrum, which spans over several decades, can be described as a power-law with the slope defined by a value called the spectral index which ranges from values of 2.5 -- 3.3. Deviations of the spectral index mark key features of the energy spectrum such as the knee ($\approx$ $10^{15}$ eV), the second knee ($\approx$ $10^{17}$), the ankle ($\approx$ $10^{18.5}$) and a sharp drop off that occurs at the highest energies ($\approx$ $10^{19.5}$). We develop a hybrid model of a neural network to reconstruct the maximum atmospheric depth (Xmax) and a decision tree to reconstruct the energy for an extensive air shower that is detected by the IceCube Neutrino Observatory. The resolution of our models are about 41.6 $\rm{g/cm^2}$ for Xmax and 5.64\% for log10(E/GeV). Each of these is comparable with direct optical measurements of the shower. With these reconstructions we can construct kernels, using Monte Carlo simulations, that are capable of reproducing the probability density function of real data through a weighted sum of the kernels for a showers predicted Xmax binned by the showers predicted energy. We use weights (species fractions) predicted by models, such as H3A and H4A, and use the resulting fits to determine how well those models represent the propagation and production of cosmic rays. The H3A and H4A in particular use a physical phenomenon called a Peters cycle where rigidity is expected to be the governing variable for confinement and acceleration of cosmic rays.
Author: Andreas Shalchi Publisher: Springer Science & Business Media ISBN: 3642003095 Category : Science Languages : en Pages : 210
Book Description
If charged particles move through the interplanetary or interstellar medium, they interact with a large-scale magnetic ?eld such as the magnetic ?eld of the Sun or the Galactic magnetic ?eld. As these background ?elds are usually nearly constant in time and space, they can be approximated by a homogeneous ?eld. If there are no additional ?elds, the particle trajectory is a perfect helix along which the par- cle moves at a constant speed. In reality, however, there are turbulent electric and magnetic?elds dueto the interstellaror solar wind plasma. These ?elds lead to sc- tering of the cosmic rays parallel and perpendicular to the background ?eld. These scattering effects, which usually are of diffusive nature, can be described by s- tial diffusion coef?cients or, alternatively, by mean free paths. The knowledge of these parameters is essential for describing cosmic ray propagation as well as d- fusive shock acceleration. The latter process is responsible for the high cosmic ray energies that have been observed. The layout of this book is as follows. In Chap. 1, the general physical scenario is presented. We discuss fundamental processes such as cosmic ray propagation and acceleration in different systems such as the solar system or the interst- lar space. These processes are a consequence of the interaction between charged cosmic particles and an astrophysical plasma (turbulence). The properties of such plasmas are therefore the subject of Chap. 2.
Author: Alexander Lazarian Publisher: Springer ISBN: 3662446251 Category : Science Languages : en Pages : 627
Book Description
This volume presents the current knowledge of magnetic fields in diffuse astrophysical media. Starting with an overview of 21st century instrumentation to observe astrophysical magnetic fields, the chapters cover observational techniques, origin of magnetic fields, magnetic turbulence, basic processes in magnetized fluids, the role of magnetic fields for cosmic rays, in the interstellar medium and for star formation. Written by a group of leading experts the book represents an excellent overview of the field. Nonspecialists will find sufficient background to enter the field and be able to appreciate the state of the art.
Author: Todor Stanev Publisher: Springer Science & Business Media ISBN: 3540851488 Category : Science Languages : en Pages : 334
Book Description
Offers an accessible text and reference (a cosmic-ray manual) for graduate students entering the field and high-energy astrophysicists will find this an accessible cosmic-ray manual Easy to read for the general astronomer, the first part describes the standard model of cosmic rays based on our understanding of modern particle physics. Presents the acceleration scenario in some detail in supernovae explosions as well as in the passage of cosmic rays through the Galaxy. Compares experimental data in the atmosphere as well as underground are compared with theoretical models
Author: James Bourbeau
Author: James Bourbeau
Author: 
Author: Zigfried Hampel-Arias
Author: Emily Dvorak
Author: 
Author: 
Author: Andres Alberto Medina
Author: Andreas Shalchi
Author: Alexander Lazarian
Author: Todor Stanev