In the last years, Cosmic Ray Physics has profited from the rise in space research and space-based experiments are currently providing direct measurements with unprecedented precision. In particular, the measurement of the anisotropy may provide complementary information to the features observed in the spectra of
several cosmic ray species.
In this talk, an overview of the latest results on...
Important observational results have been recently reported on the angular distributions of cosmic rays at ultra-high energies, calling into question their perception a decade ago. The extragalactic origin of the particles has been determined observationally. While no discrete source of ultrahigh-energy cosmic rays has been identified so far, the noose is tightening around nearby extragalactic...
We present the joint analysis of the arrival direction distribution of Galactic cosmic rays by the High-Altitude Water Cherenkov and IceCube Neutrino observatories at the same median primary particle energy of 10 TeV. The combined sky map and angular power spectrum largely eliminate biases that result from partial sky coverage. The trajectories and observed distribution of particles are...
The latest results of anisotropy searches with the Telescope Array will be presented, including the current status of the hot spot, spectrum declination dependence, search for energy-ordered clusters, correlation with supergalactic plane.
The Pierre Auger Observatory, thanks to its hybrid detection technique, provides information about the energy, the mass composition and the arrival direction of ultra-high energy cosmic rays (UHECRs). Starting from a simple astrophysical scenario for origin and propagation of cosmic rays, it is possible to perform a combined fit to both the energy spectrum and the mass composition data.
We...
The DArk Matter Particle Explorer (DAMPE) is a satellite-borne experiment successfully launched in December 2015. The main scientific goal of the mission is to perform high precision measurements of the High Energy Cosmic Ray (HECR) sky looking also for Dark Matter signals. After more than three years of data taking, DAMPE has collected over 5.6 billion events.
In recent years the anisotropy...
The cosmic electrons and positrons have been measured with unprecedented
statistics up to several hundreds GeV, thus permitting to explore the role that close single
sources can have in shaping the flux at different energies.
The Fermi-LAT Collaboration has provided a new
energy spectrum for the upper bounds on the e+ + e- dipole anisotropy. This observable
can bring information on the...
Under the effect of magnetic turbulence Cosmic Rays (CRs) adopt a random walk during their journey from their sources to the Earth. The talk addresses the interplay between the turbulence and Cosmic Rays. At first we will examine the effect of turbulence over Cosmic Ray transport through the derivation of diffusion coefficients. We will discuss the impact of the turbulence injected at large...
Understanding the transport of charged particles in the Galaxy is fundamental to solve the mystery of the origin of Galactic cosmic rays (CR) and to asses their role in several Galactic processes. Recent results from direct experiments, especially AMS-02 and PAMELA, are revealing a fine structure in the CR spectrum which is difficult to explain in the standard picture of Galactic propagation....
The Tibet air shower array is located at 4,300 m above sea level, Tibet, China.
In 2014, an array of underground muon detectors is added under the surface
air shower array. We would like to present recent results from the Tibet
ASgamma experiment on cosmic ray anisotropy, Sun shadow, and gamma-ray observation, together with some related topics.
Diffusive shock acceleration has been successful in describing many aspects of particle acceleration at strong shocks. In the standard description, thermal particles are energized as they cross a shock and complete cycles of Fermi acceleration. Additionally, it has been proposed that non—thermal particles placed upstream of a shock can also be energized. This process, already discussed in Bell...
We propose a machine-learning-based method to test various
hypotheses about possible sources of ultra-high-energy cosmic rays (UHECR)
using their arrival directions. We test the discriminating power of
the method on the recently proposed realistic UHECR origin scenario [1], assuming several particular nearby active galaxies as source candidates.
[1] Phys.Rev. D96 (2017) no.8, 083006
In this work, muon bundles detected at the ground level are used as a tool for high energy cosmic ray anisotropy search. Due to their penetrating ability, muons with a good accuracy retain the direction of a primary particle. Long-term muon bundle registration from 2012 to 2019 was performed with the coordinate-tracking detector DECOR, which is a part of the Unique Scientific Facility...
I will present some thoughts about the possible relation between the acceleration site of Galactic cosmic rays and the "anomalies" observed in their bulk source composition (like the Ne22/Ne20 excess and the recently detected abundance of radioactive Fe60).
Voyagers 1 and 2 are now both in the interstellar medium. Voyager 1 crossed the heliopause on 25 August 2012 and Voyager 2 recently crossed on 5 November 2018. We find that the energy spectra of H, He, and electrons, which for the first time are being measured unaffected by the effects of solar modulation, are essentially identical at the two spacecraft. This implies that there are no...
We present the results of our investigation of the solar wind (SW) interaction with the local interstellar medium (LISM). The model is based on MHD treatment of ions and takes into account their charge exchange with neutral atoms. We focus on the structures that affect the Galactic cosmic ray (GCR) transport: magnetic barriers in the heliosheath, instability of the heliopause, heliospheric...
The Interstellar Boundary Explorer (IBEX) observes enhanced Energetic Neutral Atom emission from a narrow “ribbon” centered on the local interstellar medium (LISM) magnetic field direction. IBEX has improved knowledge of the local interstellar velocity based on interstellar atom measurements and provides global views of the structure of the evolving heliosphere.
These determinations are...
The Earth resides deep in the heliosphere. The trajectories of CRs measured in air shower experiments are affected by the electromagnetic fields of the heliosphere and disturbed LISM surrounding it. This may severely distort anisotropy maps. To study the properties of interstellar CRs, we should first remove the heliospheric influence. Recent advances in the heliospheric modeling based on...
I will present a quick summary of the current state of knowledge of interstellar magnetic fields in the Milky Way. I will focus on their turbulent component, which plays a decisive role in the acceleration, propagation and confinement of cosmic rays. I will discuss some recent observational breakthroughs, describe the theoretical tools that were developed to interpret radio observations, and...
Cosmic rays propagate through the galaxy and in doing so, magnetic fields can generate chaotic behavior in their trajectories. Occasionally, these particles can get temporarily trapped in magnetic bottles, which affect the overall description of their propagation. As a result, anisotropy in the arrival distribution at Earth can emerge. In this work, we will show how the chaotic behavior of...
After entering the Galactic cosmic rays (CRs) into the heliosphere, their intensities decrease during their propagation toward the Earth. This effect is subjected to a variety of physical processes through their propagation which referred to as CR solar modulation. The key ingredients in the study of this phenomenon are the knowledge of the local interstellar spectrum (LIS) of Galactic cosmic...
We present the results of a search for diffuse photons with energies higher than 1 EeV based on Telescope Array surface detector data and a novel neural network event analysis technique. The results of a search for point sources of photons for all directions in the Northern hemisphere and a search for several target source classes are also presented.
The arrival directions of Galactic cosmic rays are highly isotropic. This is expected from the presence of turbulent magnetic fields in our Galactic environment that repeatedly scatter charged particles during propagation. However, various cosmic ray observatories have identified weak anisotropies of various angular sizes and with relative intensities of up to a level of 1 part in 1,000....
The paradigm for wave-particle interactions in cosmic ray physics, quasi-linear theory, cannot describe the small-scale anisotropies observed with high-precision observatories like IceCube and HAWC. This can be traced back to the loss of two-particle correlations when only the ensemble-averaged phase-space density is modelled.
After a brief review of standard quasi-linear theory, we consider...
We calculate the shape of the anisotropy of TeV-PeV cosmic-rays (CR) in different models of the interstellar turbulence. In general, the large-scale CR anisotropy (CRA) is not a dipole, and its shape can be used as a probe of the turbulence and CR transport properties. The 400 TeV and 2 PeV data sets of IceTop can be fitted with Goldreich-Sridhar turbulence and a broad resonance function, but...
The interpretation of cosmic-ray (CR) data still represents a major challenge that experiments have to face: a coherent interpretation of the measured CR spectra is hampered by our incomplete knowledge about both the acceleration mechanisms and the transport properties across the Galaxy. The main challenge in this context is to identify a unified picture that includes all the available...
An international group of scientists is mapping the configuration of
the very local interstellar magnetic field (ISMF) utilizing
high-sensitivity measurements of starlight that becomes linearly
polarized while traversing a medium containing magnetically aligned
interstellar dust grains. High-sensitivity polarization data for over
500 nearby stars reveal that the local interstellar medium...
The discovery of a diffuse flux of astrophysical neutrinos by IceCube has opened up new possibilities for the search of cosmic-ray sources. The sources that accelerate cosmic rays to extreme energies are most-likely also high-energy neutrino emitters. To find such sources one can look for correlations in arrival directions between astrophysical neutrinos and ultra-high-energy cosmic rays...
The energy spectrum of cosmic rays is one of the central measurements in cosmic ray physics. Mostly following a power law relation, it contains small breaks at the higher end of the energy range. Of particular importance are the so-called "knee" at around 5 PeV, where the spectrum softens, the "ankle" at around 5 EeV, where it hardens again, and a high-energy cut-off at around 50 EeV. The...
Although their astrophysical sources remain a mystery, new measurements brought by experiments such as the Pierre Auger Observatory and Telescope Array have radically improved our knowledge of the ultra-high energy cosmic-rays (UHECRs). I will present new results on the interpretation of the first significant UHECR anisotropy: a ~7% dipole, recently reported by Auger for cosmic rays above 8 EeV.
The contribution of a single source to the observed cosmic ray (CR) dipole anisotropy depends only on the fraction the source contributes to the total CR intensity, its age and its distance, but not on the energy. Therefore the observation of a constant dipole anisotropy indicates that importance of single, local sources. I review some source types suggested as, e.g., Vela, a 2 Myr old...
PeV gamma rays experience strong attenuation due to interaction with
the cosmic microwave background, thus allowing access only up to
Galactic distances. However, their hadronic origin implies that a
measurement of the diffuse PeV emission from the Galactic plane can
inform on the cosmic-ray propagation mechanisms as well as cosmic-ray
spectrum elsewhere within the Galaxy. Moreover, a...
