D. Grandi - Academia.edu (original) (raw)

Papers by D. Grandi

arXiv (Cornell University), Jul 19, 2013

The Cosmic Rays propagation was studied in details using the HelMod-2-D Monte Carlo code, that in... more The Cosmic Rays propagation was studied in details using the HelMod-2-D Monte Carlo code, that includes a general description of the diffusion tensor, and polar magnetic-field. The Numerical Approach used in this work is based on a set of Stochastic Differential Equations fully equivalent to the well know Parker Equation for the transport of Cosmic Rays. In our approach the Diffusion tensor in the frame of the magnetic field turbolence does not depends explicitly by Solar Latitude but varies with time using a diffusion parameter obtained by Neutron Monitors. The parameters of the Model were tuned using data during the solar Cycle 23 and Ulysses latitudinal Fast Scan in 1995. The actual parametrization is able to well reproduce the observed latitudinal gradient of protons and the southward shift of the minimum of latitudinal intensity. The description of the model is also available online at website www.helmod.org. The model was then applied on Pamela/Ulysses proton intensity from 2006 up to 2009. The model during this 4-year continous period agree well with both PAMELA (at 1 AU) and Ulysses data (at various solar distance and solar latitude). The agreement improves when considering the ratio between this data. Studies done also with particles with different charge (e.g. electrons) allow us to explain the presence (or not) of protons and electrons latitudinal gradients observed by Ulysses during the Latitudinal Fast Scan in 1995 and 2007.

The Encyclopedia of Astronomy and Astrophysics

The Astrophysical Journal Supplement Series, 2020

Composition and spectra of Galactic cosmic rays (CRs) are vital for studies of high-energy proces... more Composition and spectra of Galactic cosmic rays (CRs) are vital for studies of high-energy processes in a variety of environments and on different scales, for interpretation of γ-ray and microwave observations, disentangling possible signatures of new phenomena, and for understanding of our local Galactic neighborhood. Since its launch, AMS-02 has delivered outstanding quality measurements of the spectra ofp, e ± , and nuclei: 1 H-8 O, 10 Ne, 12 Mg, 14 Si. These measurements resulted in a number of breakthroughs, however, spectra of heavier nuclei and especially low-abundance nuclei are not expected until later in the mission. Meanwhile, a comparison of published AMS-02 results with earlier data from HEAO-3-C2 indicate that HEAO-3-C2 data may be affected by undocumented systematic errors. Utilizing such data to compensate for the lack of AMS-02 measurements could result in significant errors. In this paper we show that a fraction of HEAO-3-C2 data match available AMS-02 measurements quite well and can be used together with Voyager 1 and ACE-CRIS data to make predictions for the local interstellar spectra (LIS) of nuclei that are not yet released by AMS-02. We are also updating our already published LIS to provide a complete set from 1 H-28 Ni in the energy range from 1 MeV nucleon −1 to ∼100-500 TeV nucleon −1 thus covering 8-9 orders of magnitude in energy. Our calculations employ the GALPROP-HELMOD framework that is proved to be a reliable tool in deriving the LIS of CR p, e − , and nuclei 1 H-8 O.

Physical review letters, Jan 3, 2018

A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV... more A precision measurement of the nitrogen flux with rigidity (momentum per unit charge) from 2.2 GV to 3.3 TV based on 2.2×10^{6} events is presented. The detailed rigidity dependence of the nitrogen flux spectral index is presented for the first time. The spectral index rapidly hardens at high rigidities and becomes identical to the spectral indices of primary He, C, and O cosmic rays above ∼700 GV. We observed that the nitrogen flux Φ_{N} can be presented as the sum of its primary component Φ_{N}^{P} and secondary component Φ_{N}^{S}, Φ_{N}=Φ_{N}^{P}+Φ_{N}^{S}, and we found Φ_{N} is well described by the weighted sum of the oxygen flux Φ_{O} (primary cosmic rays) and the boron flux Φ_{B} (secondary cosmic rays), with Φ_{N}^{P}=(0.090±0.002)×Φ_{O} and Φ_{N}^{S}=(0.62±0.02)×Φ_{B} over the entire rigidity range. This corresponds to a change of the contribution of the secondary cosmic ray component in the nitrogen flux from 70% at a few GV to <30% above 1 TV.

Physical review letters, Jan 22, 2017

We report the observation of new properties of primary cosmic rays He, C, and O measured in the r... more We report the observation of new properties of primary cosmic rays He, C, and O measured in the rigidity (momentum/charge) range 2 GV to 3 TV with 90×10^{6} helium, 8.4×10^{6} carbon, and 7.0×10^{6} oxygen nuclei collected by the Alpha Magnetic Spectrometer (AMS) during the first five years of operation. Above 60 GV, these three spectra have identical rigidity dependence. They all deviate from a single power law above 200 GV and harden in an identical way.

Physical review letters, Jan 20, 2015

Knowledge of the precise rigidity dependence of the helium flux is important in understanding the... more Knowledge of the precise rigidity dependence of the helium flux is important in understanding the origin, acceleration, and propagation of cosmic rays. A precise measurement of the helium flux in primary cosmic rays with rigidity (momentum/charge) from 1.9 GV to 3 TV based on 50 million events is presented and compared to the proton flux. The detailed variation with rigidity of the helium flux spectral index is presented for the first time. The spectral index progressively hardens at rigidities larger than 100 GV. The rigidity dependence of the helium flux spectral index is similar to that of the proton spectral index though the magnitudes are different. Remarkably, the spectral index of the proton to helium flux ratio increases with rigidity up to 45 GV and then becomes constant; the flux ratio above 45 GV is well described by a single power law.

Physical review letters, 2015

A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) f... more A precise measurement of the proton flux in primary cosmic rays with rigidity (momentum/charge) from 1 GV to 1.8 TV is presented based on 300 million events. Knowledge of the rigidity dependence of the proton flux is important in understanding the origin, acceleration, and propagation of cosmic rays. We present the detailed variation with rigidity of the flux spectral index for the first time. The spectral index progressively hardens at high rigidities.

Cosmic Rays for Particle and Astroparticle Physics - Proceedings of the 12th ICATPP Conference ICATPP, 2011

Spectra of Galactic Cosmic Rays (GCRs) measured at the Earth are the combination of several proce... more Spectra of Galactic Cosmic Rays (GCRs) measured at the Earth are the combination of several processes: sources production and acceleration, propagation in the interstellar medium and propagation in the heliosphere. Inside the solar cavity the intensity of GCRs is reduced due to the solar modulation, the interaction which they have with the interplanetary medium. We realized a 2D stochastic simulation of solar modulation to reproduce CR spectra at the Earth, and evaluated the importance in our results of the Local Interstellar Spectrum (LIS) model and its agreement with data at high energy. We show a good agreement between our model and the data taken by AMS-01 and BESS experiments during periods with different solar activity conditions. Furthermore we made a prediction for the differential intensity which will be measured by AMS-02 experiment.

Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications - Proceedings of the 8th Conference, 2004

... P. BOBIK, M. BOSCHINI£, M. GERVASIÝ, D. GRANDI, E. MICELOTTA AND PG RANCOITA INFN, Sezione di... more ... P. BOBIK, M. BOSCHINI£, M. GERVASIÝ, D. GRANDI, E. MICELOTTA AND PG RANCOITA INFN, Sezione di Milano, c/o Dip. di Fisica, Piazza della Scienza 3, 20126 Milano, Italy E-mail:elisabetta.micelotta@mib.infn.it ... CILEA' Via R. Sanzio 4'20090 Segrate (Milano)' Italy. ...

Astroparticle, Particle and Space Physics, Detectors and Medical Physics Applications, 2006

ABSTRACT We realized a dimensional (radius and latitude) stochastic MonteCarlo for modelling the ... more ABSTRACT We realized a dimensional (radius and latitude) stochastic MonteCarlo for modelling the Galactic Cosmic Ray (GCR) propagation in the Heliosphere. The model solves numerically the transport equation of particles in the heliosphere, including major processes affecting the heliospheric particle transport: diffusion, convection, adiabatic energy losses and drift of particles. We estimated the cosmic rays spectrum at 1AU using this model formalism: our method allows the study of modulation behaviour in dependence on energy of interstellar particles and heliosphere parameters as Solar wind speed and the tilt angle alpha of the neutral sheet. We compared our simulations with the Primary CR proton spectra measured by AMS and we realized a fine tuning of our parameters in order to match real data. This work, done for the A > 0 period, can be done also for A < 0, where the best value found for the diffusion coefficient is different.

$Research paper thumbnail of Precision Measurement of the (e^{+}+e^{-}) Flux in Primary Cosmic Rays from 0.5 GeV to 1 TeV with the Alpha Magnetic Spectrometer on the International Space Station$

Physical review letters, Jan 28, 2014

We present a measurement of the cosmic ray (e^{+}+e^{-}) flux in the range 0.5 GeV to 1 TeV based... more We present a measurement of the cosmic ray (e^{+}+e^{-}) flux in the range 0.5 GeV to 1 TeV based on the analysis of 10.6 million (e^{+}+e^{-}) events collected by AMS. The statistics and the resolution of AMS provide a precision measurement of the flux. The flux is smooth and reveals new and distinct information. Above 30.2 GeV, the flux can be described by a single power law with a spectral index γ=-3.170±0.008(stat+syst)±0.008(energy scale).

Journal of Geophysical Research: Space Physics, 2016

The cosmic rays propagation inside the heliosphere is well described by a transport equation intr... more The cosmic rays propagation inside the heliosphere is well described by a transport equation introduced by Parker in 1965. To solve this equation, several approaches were followed in the past. Recently, a Monte Carlo approach became widely used in force of its advantages with respect to other numerical methods. In this approach the transport equation is associated to a fully equivalent set of stochastic differential equations (SDE). This set is used to describe the stochastic path of quasi-particle from a source, e.g., the interstellar space, to a specific target, e.g., a detector at Earth. We present a comparison of forward-in-time and backward-in-time methods to solve the cosmic rays transport equation in the heliosphere. The Parker equation and the related set of SDE in the several formulations are treated in this paper. For the sake of clarity, this work is focused on the one-dimensional solutions. Results were compared with an alternative numerical solution, namely, Crank-Nicolson method, specifically developed for the case under study. The methods presented are fully consistent each others for energy greater than 400 MeV. The comparison between stochastic integrations and Crank-Nicolson allows us to estimate the systematic uncertainties of Monte Carlo methods. The forward-in-time stochastic integrations method showed a systematic uncertainty <5%, while backward-in-time stochastic integrations method showed a systematic uncertainty <1% in the studied energy range.

The Astrophysical Journal

Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality m... more Since its launch, the Alpha Magnetic Spectrometer-02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species, p ¯ , e ±, and nuclei (H–Si, Fe), which resulted in a number of breakthroughs. The most recent AMS-02 result is the measurement of the spectra of CR sodium and aluminum up to ∼2 TV. Given their low solar system abundances, a significant fraction of each element is produced in fragmentations of heavier species, predominantly Ne, Mg, and Si. In this paper, we use precise measurements of the sodium and aluminum spectra by AMS-02 together with ACE-CRIS and Voyager 1 data to test their origin. We show that the sodium spectrum agrees well with the predictions made with the GalProp-HelMod framework, while the aluminum spectrum shows a significant excess in the rigidity range from 2–7 GV. In this context, we discuss the origin of other low-energy excesses in Li, F, and Fe found earlier. The observed excesses in Li, F, and Al appear to be con...

Proceedings of 37th International Cosmic Ray Conference — PoS(ICRC2021), 2021

Physics Department, University of Bologna, Via Irnerio, 46, Bologna, Italy INFN, Bologna, Italy I... more Physics Department, University of Bologna, Via Irnerio, 46, Bologna, Italy INFN, Bologna, Italy INFN, Milano-Bicocca, Milano, Italy CINECA, Segrate, Milano, Italy Physics Department, University of Milano-Bicocca, Milano, Italy f Science Institute, University of Iceland, Dunhaga 3, IS-107 Reykjavik, Iceland NORDITA, Roslagstullsbacken 23, 106 91 Stockholm, Sweden Hansen Experimental Physics Laboratory, Stanford University, Stanford, CA 94305 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 E-mail: masin@bo.infn.it

Physical Review Letters, 2021

The Astrophysical Journal, 2021

Since its launch, the Alpha Magnetic Spectrometer—02 (AMS-02) has delivered outstanding quality m... more Since its launch, the Alpha Magnetic Spectrometer—02 (AMS-02) has delivered outstanding quality measurements of the spectra of cosmic-ray (CR) species ( , e ±, and nuclei, 1H–8O, 10Ne, 12Mg, 14Si) which resulted in a number of breakthroughs. One of the latest long-awaited surprises is the spectrum of 26Fe just published by AMS-02. Because of the large fragmentation cross section and large ionization energy losses, most of CR iron at low energies is local and may harbor some features associated with relatively recent supernova (SN) activity in the solar neighborhood. Our analysis of the new AMS-02 results, together with Voyager 1 and ACE-CRIS data, reveals an unexpected bump in the iron spectrum and in the Fe/He, Fe/O, and Fe/Si ratios at 1–2 GV, while a similar feature in the spectra of He, O, and Si and in their ratios is absent, hinting at a local source of low-energy CRs. The found excess extends the recent discoveries of radioactive 60Fe deposits in terrestrial and lunar samples...

Physical Review Letters, 2020

The Astrophysical Journal, 2017

Local interstellar spectra (LIS) for protons, helium, and antiprotons are built using the most re... more 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.

Viene presentato lo sviluppo di un cluster ad architettura PC Linux per calcolo ad alte prestazio... more Viene presentato lo sviluppo di un cluster ad architettura PC Linux per calcolo ad alte prestazioni nell'ambito del progetto AMS.