Bulletin of the American Physical Society
APS April Meeting 2017
Volume 62, Number 1
Saturday–Tuesday, January 28–31, 2017; Washington, DC
Session J4: Cosmic Ray Science Interest Group I |
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Sponsoring Units: DAP Chair: Igor Moskalenko, Stanford University Room: Virginia A |
Sunday, January 29, 2017 10:45AM - 10:57AM |
J4.00001: Voyager 1 Observations of Galactic Cosmic Rays in the Local Interstellar Medium A. C. Cummings, E. C. Stone, B. C. Heikkila, N. Lal, W. R. Webber, G. J\'{o}hannesson, I. V. Moskalenko, E. Orlando, T. A. Porter Voyager 1 crossed into the local interstellar medium in August 2012. The low-energy part of the energy spectra of Galactic cosmic rays (GCRs) was revealed for the first time, previously having been excluded from observation by the effects of solar modulation. We present the GCR energy spectra of most elements from H through Ni from $\sim$3 to a few hundred MeV nuc$^{-1}$, and also of electrons from 2.7 to 74 MeV, for a period exceeding two years. We find that the H and He spectra have the same energy dependence between 3 and 346 MeV nuc$^{-1}$, with a broad maximum in the10-50 MeV nuc$^{-1}$ range and a H/He ratio of 12.2 $\pm$ 0.9. The observed local interstellar gradient of 3--346 MeV H is $-0.009\pm0.055$ \%/AU. The energy spectrum of electrons ($e^-$ + $e^+$) is consistent with $E^{-1.30 \pm 0.05}$. Propagation model fits to the observed spectra allow estimates of the energy density of GCRs and the ionization rates of atomic H, which will be presented and discussed. The propagation model fits also provide improved estimates of the elemental abundances in the source of Galactic cosmic rays. [Preview Abstract] |
Sunday, January 29, 2017 10:57AM - 11:09AM |
J4.00002: Constraints on Galactic Cosmic-Ray Origins from Elemental Composition Measurements W.R. Binns, E.R. Christian, A.C. Cummings, G.A. deNolfo, M.H. Israel, K.A. Lave, R.A. Leske, R.A. Mewaldt, E.C. Stone, T.T. von Rosenvinge, M.E. Wiedenbeck We present measurements of the abundances of ultra-heavy (Z\textgreater 29) cosmic rays made by the CRIS instrument on NASA's Advanced Composition Explorer satellite. The data set corresponds to 6413 days of data collection between December 4, 1997 and May 31, 2016. The charge resolution that we obtain is excellent, exhibiting essentially complete separation of adjacent charges in the Z\textgreater 28 range. We detected 196 events over the charge range of Z$=$30-40. Our measured abundances show that the ordering of refractory and volatile elements with atomic mass is greatly improved when compared to a mix of massive star outflow and SN ejecta with normal ISM, rather than pure ISM. Additionally, the refractory and volatile elements have similar slopes and refractory elements are preferentially accelerated by a factor of \textasciitilde 4. The measured abundances support a model in which \textasciitilde 20{\%} of cosmic ray source material is from massive star outflow and ejecta and \textasciitilde 80{\%} is from normal ISM. Our abundances show generally good agreement with the TIGER and SuperTIGER results. [Preview Abstract] |
Sunday, January 29, 2017 11:09AM - 11:21AM |
J4.00003: Exploring Ultra-Heavy Cosmic Rays with the Trans-Iron Galactic Element Recorder (TIGER) Jason Link Elements heavier than iron are primarily synthesized by neutron capture. These elements can be accelerated as cosmic-rays and measuring their abundances at Earth can yield information about galactic cosmic-rays’ sources, the acceleration processes and the composition of the universe beyond the boundaries of our solar system. The Trans-Iron Galactic Element Recorder (TIGER) and its larger successor SuperTIGER was designed to measure the abundance of these ultra-heavy cosmic rays between Z=10 and Z=60. These detectors utilize scintillators with a wavelength shifter bar and PMT readout system as well as aerogel and acrylic Cherenkov detectors to identify the charge and energy of a particle and utilize a scintillating fiber hodoscope to provide trajectory information. In this talk I will review the results from this highly successful program, give the status for the next SuperTIGER flight planned for a December 2017 launch from Antarctica, and discuss the future direction of the program. [Preview Abstract] |
Sunday, January 29, 2017 11:21AM - 11:33AM |
J4.00004: AMS results on positrons and antiprotons in cosmic rays Andrei Kounine AMS-02 is a particle physics detector collecting data on the International Space Station since May 2011. Precision measurements of charged cosmic ray particles have been performed by AMS using a data sample of 85 billion cosmic ray events collected during the first five years of operations on the Station. The latest AMS results on the fluxes and flux ratios of the cosmic ray particles are presented with the emphasis on the measurements of positrons and antiprotons. They show unique features that require accurate theoretical interpretation as to their origin, be it from dark matter collisions or new astrophysical sources. [Preview Abstract] |
Sunday, January 29, 2017 11:33AM - 11:45AM |
J4.00005: Measuring the Cosmic Particle Radiation from electrons to actinides - CALET John Mitchell CALET (Calorimetric Electron Telescope) was installed on the Exposed Facility of the Japanese Experiment Module (Kibo) on for 24 August 2015. CALET measures the high-energy spectra of electrons, nuclei, and gamma-rays. CALET will extend direct measurements of the total electron spectrum into the trans-TeV energy range for the first time. In this paper, we well present the science and current status of CALET and initial observations from its first 1.5 years in orbit. [Preview Abstract] |
Sunday, January 29, 2017 11:45AM - 11:57AM |
J4.00006: Status of the HELIX Experiment Scott Wakely HELIX, the High-Energy Light Isotope eXperiment, is a new balloon-borne superconducting magnet spectrometer designed to make detailed measurements of cosmic-ray chemical and isotopic abundances. Measurements of this kind, in particular of the ratio of radioactive 10Be to 9Be at energies to ~3 GeV/nuc, can provide profound insights into cosmic-ray propagation processes and confinement timescales. HELIX is scheduled to make its first flight during the 2019/2020 Antarctic campaign. In this talk, we will discuss the goals and design of the instrument and describe the status of the program. [Preview Abstract] |
Sunday, January 29, 2017 11:57AM - 12:09PM |
J4.00007: A new measurement of cosmic-ray electrons and positrons with the Large Area Telescope Alberto Manfreda We present an updated measurement of the cosmic-ray electron and positron spectrum between 7~GeV and 2~TeV, based on 7 years of data collected with the Fermi Large Area Telescope (LAT). The LAT is the first space-based instrument to directly explore the region above 1~TeV. At such high energies, the shape of the spectrum can provide useful information about the origin and propagation of cosmic-ray electrons in the nearby Galactic space. The best fit to the spectrum that we measure is given by a broken power-law, with the break located at 53 $\pm$8~GeV. Such break, however, is not significant when all the systematic uncertainties are taken into account. Above 50 GeV our data are well described by a single power law with a spectral index of 3.07 $\pm$ 0.02 (stat + syst) $\pm$ 0.06 (energy scale). An exponential cut-off lower than 1.7~TeV is excluded at 95\% CL. [Preview Abstract] |
Sunday, January 29, 2017 12:09PM - 12:21PM |
J4.00008: CALET On-orbit Calibration and Performance Yosui Akaike The CALorimetric Electron Telescope (CALET) was installed on the International Space Station (ISS) in August 2015, and has been accumulating high-statistics data to perform high-precision measurements of cosmic ray electrons, nuclei and gamma-rays. CALET has an imaging and a fully active calorimeter, with a total thickness of 30 radiation lengths and 1.3 proton interaction lengths, that allow measurements well into the TeV energy region with excellent energy resolution, 2{\%} for electrons above 100 GeV, and powerful particle identification. CALET's performance has been confirmed by Monte Carlo simulations and beam tests. In order to maximize the detector performance and keep the high resolution for long observation on the ISS, it is required to perform the precise calibration of each detector component. We have therefore evaluated the detector response and monitored it by using penetrating cosmic ray events such as protons and helium nuclei. In this paper, we will present the on-orbit calibration and detector performance of CALET on the ISS. [Preview Abstract] |
Sunday, January 29, 2017 12:21PM - 12:33PM |
J4.00009: Measurement of the cosmic-ray proton spectrum with the Fermi Large Area Telescope David Green We present the measurement of the cosmic-ray proton spectrum between 54 GeV and 9.5 TeV using 7 years of Pass 8 flight data from the Fermi Large Area Telescope (LAT). We developed a dedicated proton event selection with an acceptance of 0.25 m$^2$ sr. Our analysis yields a large dataset with low statistical uncertainty and low residual contamination for a spectral measurement. The systematic errors associated with the acceptance, energy measurement, GEANT4 Monte-Carlo simulations are an order of magnitude larger than the statistical uncertainty. The event selection and spectral measurement of the proton analysis create the opportunity for additional proton analyses with the LAT, such as a dedicated proton anisotropy search. [Preview Abstract] |
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