International Cosmic Ray Conference Research Articles

ISS-CREAM detector performance and tracking algorithms

37th International Cosmic Ray Conference (ICRC 2021) July 12th – 23rd, 2021 Online – Berlin, Germany

Analysis Results from the Cosmic Ray Energetics And Mass Instrument for the International Space Station (ISS-CREAM)

37th International Cosmic Ray Conference (ICRC 2021) July 12th – 23rd, 2021 Online – Berlin, Germany

Cosmic Ray Astrophysics using The High Altitude Water Cherenkov (HAWC) Observatory in México

The High-Altitude Water Cherenkov (HAWC) TeV gamma–ray Observatory in Mexico is ready to search and study gamma-ray emission regions, extremely high-energy cosmic-ray sources, and to identify transient phenomena. With a better Gamma/Hadron rejection method than other similar experiments, it will play a key role in triggering multi–wavelength and multi–messenger studies of active galaxies (AGN), gamma-ray bursts (GRB), supernova remnants (SNR), pulsar wind nebulae (PWN), Galactic Plane Sources, and Cosmic Ray Anisotropies. It has an instantaneous field-of-view of ∼2 str, equivalent to 15% of the whole sky and continuous operation (24 hours per day). The results obtained by HAWC–111 (111 detectors in operation) were presented on the proceedings of the International Cosmic Ray Conference 2015 and in [1]. The results obtained by HAWC–300 (full operation) are now under analysis and will be published in forthcoming papers starting in 2017 (see preliminary results on http://www.hawc-observatory.org/news/). Here we present the HAWC contributions on cosmic ray astrophysics via anisotropies studies, summarizing the HAWC detector and its upgrading by the installation of “outriggers”.

Corrigendum: A large light-mass component of cosmic rays at 1017-1017.5 electronvolts from radio observations.

Nature 531, 70–73 (2016); doi:10.1038/nature16976 In this Letter, we omitted to cite preliminary results from the low-energy extension of the Pierre Auger Observatory, as presented at the International Cosmic Ray Conference 2015 (ref. 1). Figure 1 of this Corrigendum shows measurements of the average value of Xmax for the Low Frequency Array (LOFAR), and earlier experiments using different techniques, now including the data from the Pierre Auger Observatory1, specifically the contribution of A.

The Latin American Giant Observatory: Contributions to the 34th International Cosmic Ray Conference (ICRC 2015)

The Latin American Giant Observatory (LAGO) is an extended cosmic ray observatory composed by a network of water-Cherenkov detectors spanning over different sites located at significantly different altitudes (from sea level up to more than 5000\,m a.s.l.) and latitudes across Latin America, covering a huge range of geomagnetic rigidity cut-offs and atmospheric absorption/reaction levels. This detection network is designed to measure the temporal evolution of the radiation flux at ground level with extreme detail. The LAGO project is mainly oriented to perform basic research in three branches: high energy phenomena, space weather and atmospheric radiation at ground level. LAGO is built and operated by the LAGO Collaboration, a non-centralized collaborative union of more than 30 institutions from ten countries. These are the contributions of the LAGO Collaboration to the 34th International Cosmic Ray Conference, 30 July - 6 August 2015, The Hague, The Netherlands.

Ground-Based Gamma Ray Astronomy

This paper is the write-up of a rapporteur talk given by the author at the 33rd International Cosmic Ray Conference in Rio de Janeiro, Brazil, in 2013. It attempts to summarize results and developments in ground-based gamma-ray observations and instrumentation from among the ∼300 submissions to the gamma-ray sessions of the meeting. Satellite observations and theoretical developments were covered by a companion rapporteur (Stawarz, L., 33rd ICRC, Rio de Janeiro, Brazil, Rapporteur talk: Space-based Gamma-Ray Astronomy, 2013). Any review of this nature is unavoidably subjective and incomplete. Nevertheless, the article should provide a useful status report for those seeking an overview of this exciting and fast-moving field.

An Alternative Approach to Understanding the Observed Positron Fraction

Space-based observations by PAMELA (Adriani et al., Nature 458, 607, 2009), Fermi-LAT (Ackerman et al., Phys. Rev. Lett. 105, 01103, 2012), and AMS (Aguilar et al., Phys. Rev. Lett. 110, 141102, 2013) have demonstrated that the positron fraction (e+/total-e) increases with increasing energy above about 10 GeV. According to the propagation model for Galactic cosmic rays in widespread use (Moskalenko & Strong, Astrophys. J. 493, 693, 1998), the production of secondary positrons from interaction of cosmic-ray protons and heavier nuclei with the interstellar medium gives a generally falling positron fraction between 10 and 100 GeV, with secondary positrons accounting for only ∼20 % of the observed positron fraction at 100 GeV; so some other physical phenomena have been proposed to explain the data. An alternative approach to interpreting the positron observations is to consider these data as presenting an opportunity for re-examining models of Galactic cosmic-ray propagation. Following release of the PAMELA data, three groups published propagation models (Shaviv, et al., Phys. Rev. Lett. 103, 111302, 2009, Cowsik and Burch, Phys. Rev. D. 82, 023009, 2010, Katz et al., Mon. Not. R. Aston. Soc. 405, 1458 2010) in which the observed positron fraction is explained entirely by secondary positrons produced in the interstellar medium. In May of this year, stimulated by the AMS extension of the positron data to higher energy with excellent statistics, two of those groups presented further development of their calculations (Cowsik et al. 2013, Blum et al. 2013), again concluding that the observed positrons can be understood as secondaries. None of the authors of these five papers was registered for the 33rd International Cosmic Ray Conference (ICRC). Although I am not an author of any of these papers, I have some close familiarity with one of these recent papers, so the conference organizers invited me to bring this alternative approach to the attention of the conference. The present paper is a summary of the material I presented, along with a brief comment about reaction at the conference to this approach.

Recent Highlights from IceCube

The $\sim$1 km$^3$ IceCube neutrino observatory was completed in December, 2010 and is taking data on cosmic-ray muons and neutrinos, extra-terrestrial neutrinos, and setting limits on a variety of exotic phenomena. This proceeding will cover recent IceCube results, with an emphasis on cosmic-rays and on searches for extra-terrestrial neutrinos, with a stress on results that were presented at the 2013 International Cosmic Ray Conference.

High-energy neutrino astronomy: a glimpse of the promised land

In 2012, physicists and astronomers celebrated the hundredth anniversary of the detection of cosmic rays by Viktor Hess. A year later, in 2013, the first evidence of extraterrestrial high-energy neutrinos emerged, promising fundamental insight into the origin of cosmic rays. The evidence was obtained from the data from the IceCube neutrino telescope at the South Pole. When the idea of this telescope was first discussed at the 1973 International Cosmic Ray Conference, it was beyond anyone's imagination that it would take a biblical forty years before the first discoveries would be made and the promised land of the high energy neutrino would first be glimpsed. This paper sketches the development towards highly sensitive detectors, describes the latest results from the IceCube and ANTARES neutrino telescopes, and takes a look into the future.

Cosmic ray modulation with a Fisk-type heliospheric magnetic field and a latitude-dependent solar wind speed

The effect of a latitude-dependent solar wind speed on a Fisk heliospheric magnetic field [Fisk, L. A. Motion of the footpoints of heliospheric magnetic field lines at the Sun: implications for recurrent energetic particle events at high heliographic latitudes. J. Geophys. Res. 101, 15547–15553, 1996] was first discussed by Schwadron and Schwadron and McComas [Schwadron, N.A. An explanation for strongly underwound magnetic field in co-rotating rarefaction regions and its relationship to footpoint motion on the the sun. Geophys. Res. Lett. 29, 1–8, 2002. and Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41–1, 2003]. Burger and Sello [Burger, R.A., Sello, P.C. The effect on cosmic ray modulation of a Parker field modified by a latitudinal-dependent solar wind speed. Adv. Space Res. 35, 643–646, 2005] found a significant effect for a simplified 2D version of a latitude-dependent Fisk-type field while Miyake and Yanagita [Miyake, S., Yanagita, S. The effect of a modified Parker field on the modulation of the galactic cosmic rays. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, 445–448, 2007] found a smaller effect. The current report improves on a previous attempt Hitge and Burger [Hitge, M., Burger, R.A. The effect of a latitude-dependent solar wind speed on cosmic-ray modulation in a Fisk-type heliospheric magnetic field. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, pp. 449–450, 2007] where the global change in the solar wind speed and not the local speed gradient was emphasized. The sheared Fisk field of Schwadron and McComas [Schwadron, N.A., McComas, D.J. Heliospheric “FALTS”: Favored acceleration locations at the termination shock. Geophys. Res. Lett. 30, 41–1, 2003.) is similar to the current Schwadron–Parker hybrid field. Little difference is found between the effects of a Parker field and a Schwadron–Parker hybrid field on cosmic-ray modulation, in contrast to the results of Burger and Sello and Miyake and Yanagita [Burger, R.A., Sello, P.C. The effect on cosmic ray modulation of a Parker field modified by a latitudinal-dependent solar wind speed. Adv. Space Res. 35, 643–646, 2005 and Miyake, S., Yanagita, S. The effect of a modified Parker field on the modulation of the galactic cosmic rays. In: Proceedings of 30th International Cosmic Ray Conference. Merida, Mexico, vol. 1, pp. 445–448, 2007]. The two-dimensional approximation used by these authors is therefore inadequate to model the complexities of the actual three-dimensional field. We also show that a Fisk-type field with a latitude-dependent solar wind speed (Schwadron–Parker hybrid field) decreases both the relative amplitude of recurrent cosmic ray intensity variations and latitude gradients and yields similar constants of proportionality for these quantities as for the constant solar wind speed case.

Ultra high-energy cosmic ray observations

The year 2007 has furnished us with outstanding results about the origin of the most energetic cosmic rays: a flux suppression as expected from the GZK-effect has been observed in the data of the HiRes and Auger experiments and correlations between the positions of nearby AGN and the arrival directions of trans-GZK events have been observed by the Pierre Auger Observatory. The latter finding marks the beginning of ultra high-energy cosmic ray astronomy and is considered a major breakthrough starting to shed first light onto the sources of the most extreme particles in nature. This report summarizes those observations and includes other major advances of the field, mostly presented at the 30th International Cosmic Ray Conference held in Mérida, Mexico, in July 2007. With increasing statistics becoming available from current and even terminated experiments, systematic differences amongst different experiments and techniques can be studied in detail which is hoped to improve our understanding of experimental techniques and their limitations.

Observations of ultra-high energy cosmic rays

The status of measurements of the arrival directions, mass composition and energy spectrum of cosmic rays above 3 × 1018 eV (3 EeV) is reviewed using reports presented at the 29th International Cosmic Ray Conference held in Pune, India, in August 2005.

The giant awakes

The Pierre Auger Observatory takes the lead in the quest for the origin of the highest energy cosmic rays. Still growing, it is already the largest experiment and has equalled the exposure of all previous experiments. First promising results were presented at the International Cosmic Ray Conference, Pune, India, in August 2005.

Modeling spectra of cosmic rays influencing on the ionospheres of the earth and outer planets during solar maximum and minimum

The galactic (GCRs) and anomalous (ACRs) cosmic rays form the lower parts of the planetary ionospheres. For this purpose analytical and numerical spectra for cosmic particles are necessary. The spectra of GCRs and ACRs observed in the Solar system are modulated by the Sun. Our knowledge of GCR modulation in the solar system was greatly enhanced thanks to the heliospheric missions, Voyager 1 and 2 that covered the outer Solar system up to ∼75 AU radial distance from the Sun. In this paper, a new model for the calculation of the GCR and ACR differential spectra D( E) on the basis of satellite and balloon measurements is created. This computed analytical model gives a practical possibility for investigation of experimental data from measurements of galactic cosmic rays and their anomalous component. The integral spectra D(> E) are computed and also obtained. The average radial gradient of GCR is accepted 4%/AU [F. Mcdonald, Z. Fujii, et al. The cosmic ray radial and latitudinal intensity gradient in the inner and outer heliosphere, in: Proceedings of 27th International Cosmic Ray Conference, Copernicus Gesellschaft, p. 3906, 2001]. The contribution of GCRs and ACRs to the ionization of the ionospheres of outer planets will be increased with increase of the planetary distances from the Sun.

Comment on “Determining energy spectra for separate mass groups from EAS: the quest is still on”

In a recent publication Schatz [Astropart. Phys. (2003), this issue] argues that unambiguous results about energy distributions of primary cosmic-ray mass groups can only be obtained from measured air shower observables if their mutual correlations are explicitly taken into account. This statement is used to challenge preliminary results presented by the KASCADE Collaboration at the International Cosmic Ray Conference in Hamburg, 2001 [KASCADE Collaboration, 27th ICRC, Hamburg, 2001, p. 97; KASCADE Collaboration, Invited Rapporteur and Highlight Papers of ICRC 2001, p. 240]. In this comment it is argued that the criticism of Schatz does not apply to the aforementioned analysis of KASCADE data.

Researchers discuss role of flares and shocks in solar energetic particle events

Sixty participants gathered at a workshop last 5–7 August in Lüneburg, Germany just prior to the 27th (Hamburg) International Cosmic Ray Conference to discuss the relative importance of flares and shocks as sources of solar energetic particle (SEP) events. In the current two‐class paradigm for SEP events [Reames, 1999], the flare process accounts for acceleration in “impulsive” events, while Coronal Mass Ejection (CME)‐driven coronal and interplanetary shock acceleration dominates “gradual” events. (For more on SEP terminology see Cliver and Cane [2002].)

In Brief

The Spectroscopy Society of Pittsburgh has announced that Alan G. Marshall will receive the 2002 Pittsburgh Spectroscopy Award at the society’s annual conference in New Orleans, Louisiana, next March. Marshall is being recognized for his “co-invention (with Melvin Comisarow) of the Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) technique and other advancements he has stimulated in mass spectrometry.” He is the Kasha Professor of Chemistry at Florida State University and director of the ion cyclotron resonance program at the National High Magnetic Field Laboratory in Tallahassee, Florida.At its annual meeting held this month in Atlantic City, New Jersey, the Eastern Analytical Symposium presented the 2001 EAS awards to seven individuals, two of whom conduct physics-related work. Ray Freeman received the EAS Award for Achievements in Magnetic Resonance. He retired in 1999 as the Plummer Professor of Magnetic Resonance in the chemistry department at the University of Cambridge in the UK and is currently writing an introductory book on magnetic resonance. The EAS Award for Achievements in Near-Infrared Spectroscopy was given to Yukihiro Ozaki, a professor of chemistry at Kwansei-Gakuin University in Nishinomiya, Japan.The Commission on Cosmic Rays of the International Union of Pure and Applied Physics handed out its awards for 2001 in August at the International Cosmic Ray Conference in Hamburg, Germany. The Shakti P. Duggal Award went to Teresa Montaruli in recognition of “significant contributions to cosmic-ray physics by a young scientist of outstanding ability.” Montaruli is an associate researcher with a joint appointment at Bari University and the National Institute of Nuclear Physics (INFN), both in Italy. Vitaly Lazarevich Ginzburg received the O’Ceallaigh Medal for “outstanding contributions to cosmic-ray physics.” He is a scientific adviser at the Lebedev Physical Institute in Moscow and a professor at the Moscow Physics and Technology Institute. Reuven Ramaty was acknowledged with the Yodh Prize for “significant and outstanding contributions to the field of cosmic-ray astrophysics.” A senior scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, he was informed of this honor shortly before his death this past April.This past July, Gordon E. Pike was appointed editor-in-chief of the Journal of Materials Research. He is concurrently working as a senior manager at Sandia National Laboratories in Albuquerque, New Mexico. He replaces Robert P. Frankenthal, who retired from the journal after three years as its editor-in-chief. Frankenthal continues to work as a consultant, primarily to Bell Labs, Lucent Technologies, in Murray Hill, New Jersey. Royce Zia won an Alexander von Humboldt Research Award this year from the Alexander von Humboldt Foundation in Bonn, Germany. He is a professor of physics and codirector of the Center for Stochastic Processes in Science and Engineering at Virginia Tech in Blacksburg, Virginia. The foundation acknowledged Zia for his “seminal contributions to the theory of critical and interfacial phenomena,” adding that he “has played a pioneering role in recent years in advancing our understanding of the statistical mechanics of nonequilibrium systems, in particular, driven diffusive systems.” The award recognizes past accomplishments of winners, who are invited to carry out research projects of their choice in Germany. Zia will conduct his research at the University of Essen with Hans Werner Diehl. Beverly Karplus Hartline joined Argonne National Laboratory last April as deputy director. She previously was the acting deputy associate laboratory director of the strategic and supporting research directorate at Los Alamos National Laboratory.The International Centre for Diffraction Data, located in Newtown Square, Pennsylvania, presented the 2001 J. D. Hanawalt Award in August to Raymond P. Goehner and Joseph R. Michael, both of Sandia National Laboratories in Albuquerque, New Mexico, for “excellence in the field of x-ray powder diffraction.” After receiving the award, Goehner, manager in the materials characterization department, and Michael, distinguished member of the technical staff, both presented the Hanawalt Award Lecture entitled “Phase Identification Using Electron Backscatter Diffraction in the SEM [Scanning Electron Microscope]: A Powerful Tool for Materials Science” at the annual Denver x-ray conference in Steamboat Springs, Colorado.Earlier this year, Lyle Schwartz became the new director of the Air Force Office of Scientific Research, headquartered in Arlington, Virginia. Schwartz, previously the director of the aerospace and materials sciences directorate at that office, replaced Joseph F. Janni, who retired in March after five years as director. Janni plans to work as a research consultant in the science community.© 2001 American Institute of Physics.

Cosmic-ray modulation ground-based observations

This rapporteur paper discusses some achievements in the understanding of cosmic-ray solar modulation with ground-based observations presented at the XXIV International Cosmic Ray Conference.

High-energy interactions

This paper, based on the rapporteur talk given at the XXIV International Cosmic-Ray Conference (Roma, 28 August–8 September 1995), concerns the sessions HE1, HE2, HE6. Multihadron production in cosmic rays, models, emulsion chamber measurements, simulation of electromagnetic and hadronic cascades, new particles and processes are summarized in the frame of the special phenomenology adapted to the collisions of ultrahigh-energy particles in the atmosphere.

Solar cosmic rays

This report is a brief overview of the energetic-particle phenomena related to solar activity discussed at the XXIV International Cosmic-Ray Conference. In the rapporteur's opinion, the most significant results to be highlighted are: 1) the new higher-energy measurements of the solar energetic ion charge state which seem to be consistent with the older measurements at ∼1 MeV/nucleon, and 2) the many reports of extended gamma-ray production during solar flares with multiple episodes of emission implying multiple episodes of particle acceleration.