Search results for " UHECR"
showing 4 items of 4 documents
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
2010
Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, 6 x 10(19) eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1 degrees from the position of an active galactic nucleus within 75 Mpc (using the Veron-Cetty and Veron 12th catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating…
I raggi cosmici: cosa sono, da dove provengono, che messaggio portano.
2009
Una pioggia continua di oltre 100 particelle al secondo ci colpisce e ci attraversa, in ogni luogo della Terra, in ogni istante della nostra vita. Si tratta dei raggi cosmici che pervadono l’universo e colpiscono la Terra in modo isotropo (senza alcuna direzione privilegiata) proveniendo dal cosmo, e verosimilmente sia dall’interno che dall’esterno della nostra Galassia. La loro energia è estremamente variabile, ma più è grande, meno frequenti essi sono. Essi contengono dei messaggi la cui interpretazione ci consentirebbe di conoscere una grande messe di informazioni sui fenomeni che avvengono nello spazio e che coinvolgono la nascita, la formazione e la morte delle stelle e degli altri cor…
Atmospheric effects on extensive air showers observed with the Surface Detector of the Pierre Auger Observatory
2009
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 val…
Multi Parametric Advanced Research tool for meteo satellite data interfacing with space observation of Ultra High Energy Cosmic Rays.
2006
To approach the study of the cosmic rays in the energy range E > 10 20 eV, the upper end of the spectrum observed to date, with a large statistical significance (103 events/year), and hence address the solution of several astrophysical and cosmological problems related to their existence and behaviour, a new generation of experiments will probably have to be conceived and realised. They will be based on the observation and measurements of cosmic rays from space. The extremely low rate of these events (∼ 1 event/(century × km2 × sr)) imposes a very large effective area to be monitored, of the order of 105km2, as an observational requirement to meet the target statistics. The Extreme Universe…