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Title: Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species

Abstract

Local interstellar spectra (LIS) for protons, helium, and antiprotons are built using the most recent experimental results combined with state-of-the-art models for propagation in the Galaxy and heliosphere. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of cosmic-ray (CR) species at different modulation levels and at both polarities of the solar magnetic field. To do so in a self-consistent way, an iterative procedure was developed, where the GALPROP LIS output is fed into HelMod, providing modulated spectra for specific time periods of selected experiments to compare with the data; the HelMod parameter optimization is performed at this stage and looped back to adjust the LIS using the new GALPROP run. The parameters were tuned with the maximum likelihood procedure using an extensive data set of proton spectra from 1997 to 2015. The proposed LIS accommodate both the low-energy interstellar CR spectra measured by Voyager 1 and the high-energy observations by BESS, Pamela, AMS-01, and AMS-02 made from the balloons and near-Earth payloads; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The found solution is in a good agreement with proton, helium, andmore » antiproton data by AMS-02, BESS, and PAMELA in the whole energy range.« less

Authors:
; ; ; ; ; ; ; ;  [1];  [2];  [3]; ;  [4]; ; ;  [5];  [6]
  1. INFN, Milano-Bicocca, Milano (Italy)
  2. Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik (Iceland)
  3. Institutt for fysikk, NTNU, NO-7491 Trondheim (Norway)
  4. INFN, Bologna (Italy)
  5. Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 (United States)
  6. Frankfurt Institute of Advanced Studies, Frankfurt (Germany)
Publication Date:
OSTI Identifier:
22663607
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 840; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ANTIPROTONS; COMPARATIVE EVALUATIONS; COSMIC RADIATION; COUNTING RATES; DIFFUSION; GALAXIES; HELIOSPHERE; HELIUM; INTERSTELLAR SPACE; ITERATIVE METHODS; MAGNETIC FIELDS; PROTON SPECTRA; SUN; VOYAGER SPACE PROBES

Citation Formats

Boschini, M. J., Torre, S. Della, Gervasi, M., Grandi, D., Vacca, G. La, Pensotti, S., Rancoita, P. G., Rozza, D., Tacconi, M., Jóhannesson, G., Kachelriess, M., Masi, N., Quadrani, L., Moskalenko, I. V., Orlando, E., Porter, T. A., and Ostapchenko, S. S.. Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species. United States: N. p., 2017. Web. doi:10.3847/1538-4357/AA6E4F.
Boschini, M. J., Torre, S. Della, Gervasi, M., Grandi, D., Vacca, G. La, Pensotti, S., Rancoita, P. G., Rozza, D., Tacconi, M., Jóhannesson, G., Kachelriess, M., Masi, N., Quadrani, L., Moskalenko, I. V., Orlando, E., Porter, T. A., & Ostapchenko, S. S.. Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species. United States. doi:10.3847/1538-4357/AA6E4F.
Boschini, M. J., Torre, S. Della, Gervasi, M., Grandi, D., Vacca, G. La, Pensotti, S., Rancoita, P. G., Rozza, D., Tacconi, M., Jóhannesson, G., Kachelriess, M., Masi, N., Quadrani, L., Moskalenko, I. V., Orlando, E., Porter, T. A., and Ostapchenko, S. S.. Wed . "Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species". United States. doi:10.3847/1538-4357/AA6E4F.
@article{osti_22663607,
title = {Solution of Heliospheric Propagation: Unveiling the Local Interstellar Spectra of Cosmic-ray Species},
author = {Boschini, M. J. and Torre, S. Della and Gervasi, M. and Grandi, D. and Vacca, G. La and Pensotti, S. and Rancoita, P. G. and Rozza, D. and Tacconi, M. and Jóhannesson, G. and Kachelriess, M. and Masi, N. and Quadrani, L. and Moskalenko, I. V. and Orlando, E. and Porter, T. A. and Ostapchenko, S. S.},
abstractNote = {Local interstellar spectra (LIS) for protons, helium, and antiprotons are built using the most recent experimental results combined with state-of-the-art models for propagation in the Galaxy and heliosphere. Two propagation packages, GALPROP and HelMod, are combined to provide a single framework that is run to reproduce direct measurements of cosmic-ray (CR) species at different modulation levels and at both polarities of the solar magnetic field. To do so in a self-consistent way, an iterative procedure was developed, where the GALPROP LIS output is fed into HelMod, providing modulated spectra for specific time periods of selected experiments to compare with the data; the HelMod parameter optimization is performed at this stage and looped back to adjust the LIS using the new GALPROP run. The parameters were tuned with the maximum likelihood procedure using an extensive data set of proton spectra from 1997 to 2015. The proposed LIS accommodate both the low-energy interstellar CR spectra measured by Voyager 1 and the high-energy observations by BESS, Pamela, AMS-01, and AMS-02 made from the balloons and near-Earth payloads; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The found solution is in a good agreement with proton, helium, and antiproton data by AMS-02, BESS, and PAMELA in the whole energy range.},
doi = {10.3847/1538-4357/AA6E4F},
journal = {Astrophysical Journal},
number = 2,
volume = 840,
place = {United States},
year = {Wed May 10 00:00:00 EDT 2017},
month = {Wed May 10 00:00:00 EDT 2017}
}
  • The period in and near the 1987 solar minimum of modulation is a unique interval in the 11-year solar cycle modulation for determining whether both the heliospheric current sheet and charged particle gradient drift contribute significantly to the modulation of galactic cosmic rays and the anomalous components. The investigation of this period is based on measurements from neutron monitors and the IMP 8 satellite at 1 AU and the Pioneer 10, Pioneer 11, Voyager 1, and Voyager 2 spacecraft distributed throughout the heliosphere to {approximately}46AU. Three observations essential for the analysis are as follows: (1) the brief time-intensity profile formore » cosmic ray minimum could be traced relatively unchanged from 1 AU to {approximately}41 AU at the average solar wind velocity, (2) the onset of enhanced modulation in the new solar cycle at 1 AU began at the highest magnetic rigidity and progressed in time over a period of months to particles of low magnetic rigidity, and (3) the average tilt angle of the neutral current sheet was available from Hoeksema (1989) as a function of time for the period centered on the 1987 solar minimum at 1 AU. To account for the observations the authors propose a model for the onset of the new modulation cycle which includes a change in the average tilt angle of the current sheet as it propagates outward through the heliosphere at the solar wind velocity. Calculations based on the model with an inwardly directed north solar polar magnetic field include diffusion, convection, adiabatic deceleration, and drift for the inward propagation of cosmic ray protons in the energy range from 20 to 1500 MeV and reproduced the rigidity phase lag effect observed in the 1987 data.« less
  • Some implications of a model for the solar wind-local-interstellar-medium (LISM) interaction, comprising a bow shock and a heliospheric shock with a contact interface in between, are compared against the Voyager probe data. A fit can be achieved if the LISM electron density is somewhat higher than indicated by pulsar dispersion measurements. The theory is compatible with the hydrogen densities inferred from Copernicus and from the scattering solar L-alpha radiation. 14 references.
  • We report the first direct measurement of the Ne/O abundance ratio of the interstellar neutral gas flowing into the inner heliosphere. From the first year of Interstellar Boundary Explorer IBEX data collected in spring 2009, we derive the fluxes of interstellar neutral oxygen and neon. Using the flux ratio at the location of IBEX at 1 AU at the time of the observations, and using the ionization rates of neon and oxygen prevailing in the heliosphere during the period of solar minimum, we estimate the neon/oxygen ratios at the heliospheric termination shock and in the gas phase of the inflowingmore » local interstellar medium. Our estimate is (Ne/O){sub gas,ISM} = 0.27 {+-} 0.10, which is-within the large given uncertainties-consistent with earlier measurements from pickup ions. Our value is larger than the solar abundance ratio, possibly indicating that a significant fraction of oxygen in the local interstellar medium is hidden in grains and/or ices.« less
  • We study the energy dependence of {approx}0.5-6 keV energetic neutral atom (ENA) spectra in the southern heliospheric polar region obtained during five six-month sky maps measured by IBEX-Hi. We calculate the spectral slopes in the south pole in four different energy bands, namely, {approx}0.7-1.1 keV, {approx}1.1-1.7 keV, {approx}1.7-2.7 keV, and {approx}2.7-4.3 keV. We show (1) a persistent flattening of the ENA spectrum between {approx}1 and 2 keV, (2) significantly different modes (2.31, 1.58, 0.97, and 1.44) for the distributions of the slopes in the four different energy bands, and (3) a general decrease with increasing energy in the widths (FWHM)more » and mode fluctuations (their spread) of the slope distributions. We also compare the averaged ENA spectra measured at the south pole and at mid-latitudes. We conclude that the flattening between {approx}1 and 2 keV in the polar spectrum (spectral break) is produced by an enhancement of ENAs created by charge exchange between interstellar neutrals and pick-up ions in the fast solar wind.« less