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81.
Space weather research with the Pierre Auger Observatory
Miha Živec, 2019, magistrsko delo

Opis: Space weather refers to environmental conditions in the interplanetary space and Earth’s magnetosphere, ionosphere and exosphere and can influence the performance and reliability of electronics based technological systems. The major role in space weather changes plays the solar wind, a stream of charged particles (mostly electrons and protons) with energies of approximately 1 keV, that can cause geomagnetic storms and auroras. During their entry into the atmosphere, high energy cosmic rays collide with atomic nuclei of atmospheric gasses. When scattering occurs extensive air showers are created. Those cascades of secondary particles create flashes of light due to the Cherenkov effect as well as excite molecules of nitrogen gas in atmosphere, which then glow in fluorescent light. In order to observe the light created by air showers, it has to be collected with telescopes. The particles from the cascades that reach ground can be detected with surface detectors. The Pierre Auger Observatory is the largest observatory for cosmic ray measurements. It is located in Argentinian pampas covering an area of 3000 km2. It consists of 1660 surface detectors and 27 fluorescence telescopes. For cosmic rays with energies above few 1017 eV, a precise reconstruction of energy and direction of primary particle is achievable. Observatory also allows measurement of flux of incoming particles down to primary energies in ca. 10 GeV - 10 TeV interval, with a median energy ca. 80-90 GeV. This measurement capability is called "scaler" mode, since the corresponding data consist of scaler counted cascade particles with deposited energy between 15 and 100 MeV, at the average rate of 2 kHz per individual surface detector. For the purpose of this master thesis I compared the data from scaler mode measurements with measurements of neutron monitors, which are commonly used for space weather observations. With the correlation received from the comparison, I showed that scaler mode operation of Pierre Auger observatory can be used to monitor space weather events such as solar cycle and the decreases in the observed galactic cosmic ray intensity due to solar wind (Forbush decrease).
Najdeno v: ključnih besedah
Povzetek najdenega: ...entry into the atmosphere, high energy cosmic rays collide with atomic nuclei of atmospheric gasses. When...
Ključne besede: Pierre Auger Observatory, cosmic rays, space weather, Forbush decrease
Objavljeno: 17.09.2019; Ogledov: 3363; Prenosov: 145
.pdf Polno besedilo (5,21 MB)

82.
Search forγ-ray emission from dark matter particle interactions from theAndromeda and Triangulum galaxies with the Fermi Large Area Telescope
Gabrijela Zaharijas, 2019, izvirni znanstveni članek

Najdeno v: ključnih besedah
Povzetek najdenega: ...gamma rays, dark matter...
Ključne besede: gamma rays, dark matter
Objavljeno: 20.02.2020; Ogledov: 1598; Prenosov: 0
.pdf Polno besedilo (11,40 MB)

83.
Indications of Intermediate-Scale Anisotropy of Cosmic Rays with Energy Greater Than 57 EeV in the Northern Sky Measured with the Surface Detector of the Telescope Array Experiment
J. P. Lundquist, R.U. Abbasi, 2014, izvirni znanstveni članek

Opis: We have searched for intermediate-scale anisotropy in the arrival directions of ultrahigh-energy cosmic rays with energies above 57 EeV in the northern sky using data collected over a 5 year period by the surface detector of the Telescope Array experiment. We report on a cluster of events that we call the hotspot, found by oversampling using 20∘-radius circles. The hotspot has a Li-Ma statistical significance of 5.1σ, and is centered at R.A.=146.7∘, Dec.=43.2∘. The position of the hotspot is about 19∘ off of the supergalactic plane. The probability of a cluster of events of 5.1σ significance, appearing by chance in an isotropic cosmic-ray sky, is estimated to be 3.7×10−4 (3.4σ).
Najdeno v: ključnih besedah
Ključne besede: acceleration of particles, cosmic rays, large-scale structure of universe, surveys
Objavljeno: 24.04.2020; Ogledov: 1880; Prenosov: 0
.pdf Polno besedilo (529,81 KB)

84.
A Northern Sky Survey for Point-Like Sources of EeV Neutral Particles with the Telescope Array Experiment
J. P. Lundquist, R.U. Abbasi, 2015, izvirni znanstveni članek

Opis: We report on the search for steady point-like sources of neutral particles around 1018 eV between 2008 and 2013 May with the scintillator SD of the Telescope Array experiment. We found overall no significant point-like excess above 0.5 EeV in the northern sky. Subsequently, we also searched for coincidence with the Fermi bright Galactic sources. No significant coincidence was found within the statistical uncertainty. Hence, we set an upper limit on the neutron flux that corresponds to an averaged flux of 0.07 km−2 yr−1 for E > 1EeV in the northern sky at the 95% confidence level. This is the most stringent flux upper limit in a northern sky survey assuming point-like sources. The upper limit at the 95% confidence level on the neutron flux from Cygnus X-3 is also set to 0.2 km−2 yr−1 for E > 0.5 EeV. This is an order of magnitude lower than previous flux measurements.
Najdeno v: ključnih besedah
Povzetek najdenega: ...acceleration of particles, cosmic rays, surveys...
Ključne besede: acceleration of particles, cosmic rays, surveys
Objavljeno: 24.04.2020; Ogledov: 2459; Prenosov: 0
.pdf Polno besedilo (1,63 MB)

85.
Radar Sensing of Ultra-High Energy Cosmic Ray Showers
J. P. Lundquist, diplomsko delo

Opis: The intent of this paper is to review the history and potential importance of the use of radar techniques in detecting the ionization columns of ultra-high energy cosmic ray showers and give a short overview of a currently planned radar experiment at the Telescope Array. There is much activity in cosmic ray research to study the composition and source locations of this phenomena. Radar would be an important addition to fluorescence and scintillation detection as it theoretically could attain greater volume coverage and nearly the accuracy of fluorescence systems with less infrastructure and much longer running times. The currently estimated mean echo lifetime is on the order of 50 µs for a cosmic ray of energy 10^19 eV. It is shown that a continuous wave bi-directional radar system transmitting in the low-VHF with a large obstruction between receiver and transmitter (such as a mountain or earth curvature), which assures direct transmission is reduced, is the nominal configuration and the planned radar experiment at the Telescope Array satisfies these requirements.
Najdeno v: ključnih besedah
Povzetek najdenega: ...cosmic rays, radar...
Ključne besede: cosmic rays, radar
Objavljeno: 24.04.2020; Ogledov: 1768; Prenosov: 0
.pdf Polno besedilo (4,71 MB)

86.
Eenergy Anisotropies of Proton-like Ultra-High Energy Cosmic Rays
Jon Paul Lundquist, doktorska disertacija

Opis: Evidence of a number of interrelated energy dependent intermediate-scale anisotropies have been found in the arrival directions of proton-like ultra-high energy cosmic rays (UHECR) using 7 years of Telescope Array (TA) data. These are found using analysis techniques that have been developed for this dissertation. Using surface detector (SD) data the reported TA “Hotspot” excess, E≥10^19.75 eV, is found to correspond to a deficit, or “Coldspot,” of events for 10^19.1≤E<10^19.75 eV at 142◦R.A., 40◦ Dec. The global post-trial significance of this Hot/Coldspot event density asymmetry is found to be 5.1σ (p = 1.56 × 10−7). This Hot/Coldspot feature is the combination, at the same location, of an energy spectrum anisotropy with a 3.74σ significance for energies E≥10^19.2 eV and an energy-distance correlation with a 3.34σ significance for energies E≥1019.3 eV. The UHECR Hotspot alone is analyzed using a new kernel density estimation (KDE) anisotropy method and found to have a 3.65σ significance (E≥1019.75 eV). These features suggest energy dependent magnetic deflection of UHECR. The composition of UHECR primary particles is also studied using a new “Quality Factor Analysis” pattern recognition event selection for fluorescence detectors (FD). This minimizes the energy dependence of the resolution of extensive air shower (EAS) Xmax depth. Also, a new statistical method making use of all higher moments than the mean shower depth distribution is developed – as there is large disagreement in between all EAS simulation models. There is also an uncertainty, just as large, for any particular model, given uncertainties in particle interaction parameters extrapolated to much higher energies from Large Hadron Collider (LHC) data. The TA hybrid FD/SD data is found to be statistically compatible with a pure proton composition, though not incompatible with a light mixed composition, for all models of EAS above E≥10^18.4 eV. There is also no statistically significant evidence of the composition getting heavier at the highest energies. The combined information of a proton-like light composition, and anisotropy evidence suggestive of energy dependent magnetic deflection of UHECR, should be useful for informing future source searches and models of intergalactic propagation through magnetic fields.
Najdeno v: ključnih besedah
Ključne besede: cosmic rays, UHECR, composition, anisotropy
Objavljeno: 24.04.2020; Ogledov: 1809; Prenosov: 0
.pdf Polno besedilo (10,26 MB)

87.
Evidence of Intermediate-scale Energy Spectrum Anisotropy of Cosmic Rays E ≥ 10^19.2 eV with the Telescope Array Surface Detector
J. P. Lundquist, R.U. Abbasi, 2018, izvirni znanstveni članek

Opis: Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 10^19.2 eV in the northern hemisphere using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 10^19.2 ≤ E < 10^19.75 eV and an excess for E ≥ 10^19.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74σ global).
Najdeno v: ključnih besedah
Ključne besede: astroparticle physics, cosmic rays, anisotropy, large-scale structure of universe
Objavljeno: 24.04.2020; Ogledov: 1856; Prenosov: 80
.pdf Polno besedilo (1,43 MB)

88.
Study of Ultra-High Energy Cosmic Ray composition using Telescope Array’s Middle Drum detector and surface array in hybrid mode
Jon Paul Lundquist, R.U. Abbasi, 2015, izvirni znanstveni članek

Opis: Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.
Najdeno v: ključnih besedah
Povzetek najdenega: ...of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s...
Ključne besede: Ultra-High Energy Cosmic Rays, Cosmic ray composition, Atmospheric fluorescence, Extensive air shower array, Hybrid, Telescope Array
Objavljeno: 24.04.2020; Ogledov: 1874; Prenosov: 0
.pdf Polno besedilo (3,45 MB)

89.
On-orbit performance of the top and bottom counting detectors for the ISS-CREAM experiment on the international space station
J. P. Lundquist, S.C. Kang, 2019, izvirni znanstveni članek

Opis: The Cosmic Ray Energetics And Mass (CREAM) instrument on the International Space Station (ISS) is an experiment to study origin, propagation, acceleration and elemental composition of cosmic rays. The Top Counting Detector (TCD) and Bottom Counting Detector (BCD) are parts of the detector suite of the ISS-CREAM experiment and are designed to separate electrons and protons for studying electron and gamma-ray physics. In addition, the TCD/BCD provide a redundant trigger to that of the calorimeter and a low energy trigger to the ISS-CREAM instrument. After launching, the TCD/BCD trigger was found to be working well. Also, the TCD/BCD have been stable and their hit positions were confirmed to be well matched with other detectors on board. We present the performance and status of the TCD/BCD in flight.
Najdeno v: ključnih besedah
Povzetek najdenega: ...propagation, acceleration and elemental composition of cosmic rays. The Top Counting Detector (TCD) and Bottom...
Ključne besede: ISS-CREAM, CREAM, Cosmic rays, TCD/BCD
Objavljeno: 27.04.2020; Ogledov: 1630; Prenosov: 82
.pdf Polno besedilo (2,00 MB)

90.
Full-sky searches for anisotropies in UHECR arrival directions with the Pierre Auger Observatory and the Telescope Array
J. P. Lundquist, A. di Matteo, 2020, objavljeni znanstveni prispevek na konferenci

Najdeno v: ključnih besedah
Povzetek najdenega: ...UHECR, Cosmic Rays, Anisotropy...
Ključne besede: UHECR, Cosmic Rays, Anisotropy
Objavljeno: 27.04.2020; Ogledov: 1526; Prenosov: 0
.pdf Polno besedilo (6,28 MB)

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