Abstract
In the standard picture of Galactic cosmic rays, a diffuse flux of high-energy gamma rays and neutrinos is produced from inelastic collisions of cosmic-ray nuclei with the interstellar gas. ...The neutrino flux is a guaranteed signal for high-energy neutrino observatories such as IceCube but has not been found yet. Experimental searches for this flux constitute an important test of the standard picture of Galactic cosmic rays. Both observation and nonobservation would allow important implications for the physics of cosmic-ray acceleration and transport. We present
CRINGE
, a new model of Galactic diffuse high-energy gamma rays and neutrinos, fitted to recent cosmic-ray data from AMS-02, DAMPE, IceTop, as well as KASCADE. We quantify the uncertainties for the predicted emission from the cosmic-ray model but also from the choice of source distribution, gas maps, and cross sections. We consider the possibility of a contribution from unresolved sources. Our model predictions exhibit significant deviations from older models. Our fiducial model is available at
https://doi.org/10.5281/zenodo.7859442
.
ABSTRACT We report abundances of elements from 26Fe to 40Zr in the cosmic radiation measured by the SuperTIGER (Trans-Iron Galactic Element Recorder) instrument during 55 days of exposure on a ...long-duration balloon flight over Antarctica. These observations resolve elemental abundances in this charge range with single-element resolution and good statistics. These results support a model of cosmic ray origin in which the source material consists of a mixture of % material from massive stars and ∼81% normal interstellar medium material with solar system abundances. The results also show a preferential acceleration of refractory elements (found in interstellar dust grains) by a factor of ∼4 over volatile elements (found in interstellar gas) ordered by atomic mass (A). Both the refractory and volatile elements show a mass-dependent enhancement with similar slopes.
Abstract
Galactic cosmic rays (GCRs), the highly energetic particles that may raise critical health issues for astronauts in space, are modulated by solar activity, with their intensity lagging ...behind the variation in sunspot number (SSN) by about one year. Previously, this lag has been attributed to the combined effect of outward convecting solar wind and inward propagating GCRs. However, the lag’s amplitude and its solar-cycle dependence are still not fully understood. By investigating the solar surface magnetic field, we find that the source of heliospheric magnetic field—the open magnetic flux on the Sun—already lags behind SSN before it convects into the heliosphere along with the solar wind. The delay during odd cycles is longer than that during sequential even cycles. Thus, we propose that the GCR lag is primarily due to the very late opening of the solar magnetic field with respect to SSN, though solar wind convection and particle transport in the heliosphere also matter. We further investigate the origin of the open flux from different latitudes of the Sun and find that the total open flux is significantly contributed by that from low latitudes, where coronal mass ejections frequently occur and also show an odd–even cyclic pattern. Our findings challenge existing theories, and may serve as the physical basis of long-term forecasts of radiation dose estimates for manned deep-space exploration missions.
Abstract
Energetic charged particles are pervasive throughout the heliosphere with contributions from solar energetic particle events, stream and corotating interaction regions, galactic cosmic rays, ...anomalous cosmic rays, and suprathermal ions. The Integrated Science Investigation of the Sun (IS⊙IS) on board the Parker Solar Probe is a suite of energetic particle detectors covering the energy range ∼20 keV–200 MeV nuc
−1
. IS⊙IS measures energetic particles closer to the Sun than any instrument suite in history, providing a singular view of the energetic particle population in a previously unexplored region. To enable the global research community to efficiently use IS⊙IS data, we have developed an online living catalog of energetic particle enhancements observed by the IS⊙IS instruments. Event identification methodology, information on accessing the catalog, highlights of several events, and a summary of the overall trends are presented. Also included is a summary Event Catalog showing many of the key event parameters for IS⊙IS events to the time of writing.
Abstract
We present high-pass-filtered continuum images of the inner 3.°5 × 2.°5 of the Galactic center at 20 cm with 6.″4 resolution. These mosaic images are taken with MeerKAT and reveal a large ...number of narrow filaments, roughly an order of magnitude increase in their numbers compared to past measurements. For the first time, we carry out population studies of the spectral index and magnetic field of the entire region. The mean spectral indices of the filaments are steeper than supernova remnants (SNRs) (−0.62) with a value of
α
∼ −0.83. The variation in
α
is much larger than for the SNRs, suggesting that these characteristics have a different origin. A large-scale cosmic-ray-driven wind has recently been proposed to explain the origin of filaments and the large-scale 430 pc bipolar radio and X-ray structure. This favors the possibility that the large-scale bipolar radio/X-ray structure is produced by past activity of Sgr A* rather than a coordinated burst of supernovae. A trend of steeper indices is also noted with increasing distance from the Galactic plane. This could be explained either by synchrotron cooling or weak shocks accelerating cosmic-ray particles in the context of the cosmic-ray-driven wind. The mean magnetic field strengths along the filaments range from ∼100 to 400
μ
G depending on the assumed ratio of cosmic-ray protons to electrons. Given that there is a high cosmic-ray pressure in the Galactic center, the large equipartition magnetic field implies that the magnetic filed is weak in most of the interstellar volume of the Galactic center.
Abstract
The origin and mass composition of ultrahigh-energy cosmic rays is one of the big open questions of modern physics. Estimating the mass of ultrahigh-energy cosmic rays always involves the ...comparison of data with simulations using hadronic interaction models. The state-of-the-art hadronic interaction models, however, fail to agree with each other on the expected depths of the shower maxima, and on the average number of muons produced in air showers initiated by the same primary particles. Thus the interpretation of data in terms of the primary masses of cosmic rays differs depending on which hadronic interaction model is considered as a reference. Good agreement, however, can be found in the implications from hadronic interaction models in the prediction of the change of the average depth of the shower maximum and in the relative change in the number of produced muons as a function of the nuclear mass of the primary cosmic ray. Considering these, a model-independent estimation of the primary mass of ultrahigh-energy cosmic rays can be given in relative terms. In this work we propose a method to estimate the primary mass of ultrahigh-energy cosmic rays from the depth of the shower maximum and the number of muons produced in the shower, utilizing the similarities of modern hadronic interaction models. We discuss a geometric approach that combines the depth of the shower maximum and the number of muons produced in a shower to estimate the mass of the primary particle.
Abstract
Galactic cosmic rays (CRs) are accelerated at the forward shocks of supernova remnants (SNRs) via diffusive shock acceleration (DSA), an efficient acceleration mechanism that predicts ...power-law energy distributions of CRs. However, observations of nonthermal SNR emission imply CR energy distributions that are generally steeper than
E
−2
, the standard DSA prediction. Recent results from kinetic hybrid simulations suggest that such steep spectra may arise from the drift of magnetic structures with respect to the thermal plasma downstream of the shock. Using a semi-analytic model of nonlinear DSA, we investigate the implications that these results have on the phenomenology of a wide range of SNRs. By accounting for the motion of magnetic structures in the downstream, we produce CR energy distributions that are substantially steeper than
E
−2
and consistent with observations. Our formalism reproduces both modestly steep spectra of Galactic SNRs (∝
E
−2.2
) and the very steep spectra of young radio supernovae (∝
E
−3
).
Napoli, Italy, September 12 - 16, 2022The 12th Cosmic Ray International Seminar (CRIS 2022) was held in Napoli, Italy, from September 12th to 16th, 2022. The meeting was focused on fundamental topics ...in astroparticle physics.CRIS 2022, following the experience of previous editions, aimed to present overviews of existing data and reports from the present and future experiments. Talks covered both theoretical/phenomenological and experimental/observational aspects, in order to give an exhaustive overview of this complex field. The discussion about the present status and future plans was achieved involving theorists and experimentalists. The progress in astroparticle physics achieved through space and ground-based detectors played a major role in the scientific program of CRIS 2022.As in the past, the CRIS 2022 Conference was addressed to scientists in the field as well as to PhD and graduate students. We encouraged lively and informal discussions among participants. We take advantage of this preface to thank all the participants for their high quality contributions and for the fruitful discussions that came up during the conference.List of The CRIS 2022 Local Organizing Committee (LOC), The CRIS 2022 Scientific Organizing Committee (IAC) are available in this pdf.
PDF
