On the forward‐backward‐in‐time approach for Monte Carlo solution of Parker's transport equation: One‐dimensional case

Bobík, P.; Boschini, M.; Torre, S. Della; Gervasi, M.; Grandi, D.; Vacca, G. La; Pensotti, S.; Putiš, M.; Rancoita, P.G.; Rozza, D.; Tacconi, M.; Zannoni, M.

doi:10.1002/2015ja022237

Cited by 45 publications

(43 citation statements)

References 51 publications

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“…HelMod integrates the transport equation (Parker 1958) using a Monte Carlo approach that involves stochastic differential equations. More details on HelMod are provided in Bobik et al (2016) and Boschini et al (2017a), while on the joint implementation of HelMod with Galprop in Boschini et al (2017b), where a MCMC procedure was used to determine the propagation parameters. The best-fit CRs injection and propagation parameters from that work are used to build our model with diffusion, reacceleration and convection.…”

Section: Cr Propagation Modelsmentioning

confidence: 99%

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Orlando

2017

Monthly Notices of the Royal Astronomical Society

102

147

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Ever since the discovery of Cosmic Rays (CRs), significant advancements have been made in modeling their propagation in the Galaxy and in the Heliosphere. However, propagation models suffer from degeneracy of many parameters. To complicate the picture the precision of recent data have started challenging existing models.To tackle these issues we use available multifrequency observations of the interstellar emission from radio to gamma rays, together with direct CR measurements, to study local interstellar spectra (LIS) and propagation models. As a result, the electron LIS is characterized without any assumption on solar modulation, and favorite propagation models are put forward. More precisely, our analysis leads to the following main conclusions: (1) the electron injection spectrum needs at least a break below a few GeV; (2) even though consistent with direct CR measurements, propagation models producing a LIS with large all-electron density from a few hundreds of MeV to a few GeV are disfavored by both radio and gamma-ray observations; (3) the usual assumption that direct CR measurements, after accounting for solar modulation, are representative of the proton LIS in our ∼1 kpc region is challenged by the observed local gamma-ray HI emissivity. We provide the resulting proton LIS, all-electron LIS, and propagation parameters, based on synchrotron, gamma-ray, and direct CR data. A plain diffusion model and a tentative diffusive-reacceleration model are put forward. The various models are investigated in the inner-Galaxy region in X-rays and gamma rays. Predictions of the interstellar emission for future gamma-ray instruments (e-ASTROGAM and AMEGO) are derived.

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Section: Cr Propagation Modelsmentioning

confidence: 99%

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Orlando

2017

Monthly Notices of the Royal Astronomical Society

102

147

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“…In this work, the particle transport within the heliosphere, from the Termination Shock (TS) down to Earth orbit, is described using the HELMOD code 11 (Boschini et al 2017a, and reference therein). The HELMOD code integrates the Parker (1965) transport equation using a Monte Carlo approach involving stochastic differential equations (see a discussion in, e.g., Bobik et al 2012Bobik et al , 2016.…”

Section: Helmodmentioning

confidence: 99%

Deciphering the Local Interstellar Spectra of Primary Cosmic-Ray Species with HelMod

Boschini

Torre

Gervasi

et al. 2018

ApJ

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Local interstellar spectra (LIS) of primary cosmic ray (CR) nuclei, such as helium, oxygen, and mostly primary carbon are derived for the rigidity range from 10 MV to ∼200 TV using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HELMOD, are combined into a single framework that is used to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. The developed iterative maximum-likelihood method uses GALPROP-predicted LIS as input to HELMOD, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The interstellar and heliospheric propagation parameters derived in this study are consistent with our prior analyses using the same methodology for propagation of CR protons, helium, antiprotons, and electrons. The resulting LIS accommodate a variety of measurements made in the local interstellar space (Voyager 1) and deep inside the heliosphere at low (ACE/CRIS, HEAO-3) and high energies (PAMELA, AMS-02).that is mapping the all-sky diffuse γ-ray emission produced by CR interactions in the interstellar medium (ISM) and in the vicinity of CR accelerators.Primary nuclei, such as helium, oxygen, and mostly primary carbon, are the most abundant species in CRs after hydrogen and are the priority targets for CR missions. They are also the most abundant in the Universe, thanks to the primordial nucleosynthesis of helium and stellar nucleosynthesis that provides the heavier species. Their fragmentation in CRs produces the majority of lighter nuclides and is the main source of lithium, beryllium, and boron, which are termed "secondary." The ratios of secondary-to-primary species in CRs can be used to study properties of CR propagation in the Galaxy and provide a basis for other related studies, such as processes of particle acceleration, CR sources, properties of the ISM, search for signatures of new physics, and many others. Therefore, the LIS of helium, carbon, and oxygen are of considerable interest for astrophysics and particle physics.Recently we demonstrated that by combining two packages, GALPROP for interstellar propagation, and HELMOD for heliospheric propagation, into a single framework we were able to reproduce the direct measurements of CR protons, helium, antiprotons, and electrons (Boschini et al. 2017b(Boschini et al. , 2018 made by Voyager 1, BESS, PAMELA, AMS-01, and AMS-02 at different modulation levels, and at both polarities of the solar magnetic field. The employed iterative method uses GALPROP-predicted LIS as input to HELMOD, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The derived LIS of CR species can be used to facilitate significantly studies of CR propagation in the Galaxy and in the heliosphere by disentangling these two massive tasks and will lead to further progress in under...

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“…The particle transport within the heliosphere, from the Termination Shock (TS) to Earth's orbit, is treated in this paper using the HELMOD code. HELMOD integrates the Parker (1965) transport equation using a Monte Carlo approach involving stochastic differential equations (for further details of the method and code see Bobik et al 2012Bobik et al , 2016.…”

Section: Helmod Code For Heliospheric Cr Transportmentioning

confidence: 99%

HelMod in the Works: From Direct Observations to the Local Interstellar Spectrum of Cosmic-Ray Electrons

Boschini

Torre

Gervasi

et al. 2018

ApJ

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The local interstellar spectrum (LIS) of cosmic-ray (CR) electrons for the energy range 1 MeV to 1 TeV is derived using the most recent experimental results combined with the state-of-the-art models for CR propagation in the Galaxy and in the heliosphere. Two propagation packages, GALPROP and HELMOD, are combined to provide a single framework that is run to reproduce direct measurements of CR species at different modulation levels, and at both polarities of the solar magnetic field. An iterative maximum-likelihood method is developed that uses GALPROP-predicted LIS as input to HELMOD, which provides the modulated spectra for specific time periods of the selected experiments for model-data comparison. The optimized HelMod parameters are then used to adjust GALPROP parameters to predict a refined LIS with the procedure repeated subject to a convergence criterion. The parameter optimization uses an extensive data set of proton spectra from 1997 to 2015. The proposed CR electron LIS accommodates both the low-energy interstellar spectra measured by Voyager 1 as well as the high-energy observations by PAMELA and AMS-02 that are made deep in the heliosphere; it also accounts for Ulysses counting rate features measured out of the ecliptic plane. The interstellar and heliospheric propagation parameters derived in this study agree well with our earlier results for CR protons, helium nuclei, and anti-protons propagation and LIS obtained in the same framework.

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On the forward‐backward‐in‐time approach for Monte Carlo solution of Parker's transport equation: One‐dimensional case

Cited by 45 publications

References 51 publications

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Imprints of cosmic rays in multifrequency observations of the interstellar emission

Deciphering the Local Interstellar Spectra of Primary Cosmic-Ray Species with HelMod

HelMod in the Works: From Direct Observations to the Local Interstellar Spectrum of Cosmic-Ray Electrons

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