Latitudinal and radial gradients of galactic cosmic ray protons in the inner heliosphere – PAMELA and Ulysses observations

Simone, N. De; Felice, V. Di; Gieseler, J.; Boezio, M.; Casolino, M.; Picozza, P.; Heber, B.

doi:10.5194/astra-7-425-2011

Cited by 61 publications

(49 citation statements)

References 24 publications

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“…This is broadly consistent with the observation (De Simone et al 2011) that the density gradient lengthscale is only weakly dependent on rigidity. For a given rigidity, we also need the value A139, page 4 of 11 of L all the way from the Sun to the Earth.…”

Section: Cme-only Modelsupporting

confidence: 92%

High-rigidity Forbush decreases: due to CMEs or shocks?

Arunbabu

Antia

Dugad

et al. 2013

A&A

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Aims. We seek to identify the primary agents causing Forbush decreases (FDs) in high-rigidity cosmic rays observed from the Earth. In particular, we ask if these FDs are caused mainly by coronal mass ejections (CMEs) from the Sun that are directed towards the Earth, or by their associated shocks. Methods. We used the muon data at cutoff rigidities ranging from 14 to 24 GV from the GRAPES-3 tracking muon telescope to identify FD events. We selected those FD events that have a reasonably clean profile, and can be reasonably well associated with an Earth-directed CME and its associated shock. We employed two models: one that considers the CME as the sole cause of the FD (the CME-only model) and one that considers the shock as the only agent causing the FD (the shock-only model). We used an extensive set of observationally determined parameters for both models. The only free parameter in these models is the level of MHD turbulence in the sheath region, which mediates cosmic ray diffusion (into the CME for the CME-only model, and across the shock sheath for the shock-only model). Results. We find that good fits to the GRAPES-3 multi-rigidity data using the CME-only model require turbulence levels in the CME sheath region that are only slightly higher than those estimated for the quiescent solar wind. On the other hand, reasonable model fits with the shock-only model require turbulence levels in the sheath region that are an order of magnitude higher than those in the quiet solar wind. Conclusions. This observation naturally leads to the conclusion that the Earth-directed CMEs are the primary contributors to FDs observed in high-rigidity cosmic rays.

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Section: Cme-only Modelsupporting

confidence: 92%

High-rigidity Forbush decreases: due to CMEs or shocks?

Arunbabu

Antia

Dugad

et al. 2013

A&A

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“…The derived radial gradients of 2.8 ± 0.2%/AU for 1.9 GV protons (De Simone et al 2011;Gieseler & Heber 2016) were similar to those found in previous studies (Cummings et al 1987;McKibben 1975;Heber et al 1996). The measured latitudinal gradient was found to be slightly negative, −0.06 ± 0.01%/…”

Section: Outside the Ecliptic Planesupporting

confidence: 90%

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

Boschini

Torre

Gervasi

et al. 2017

ApJ

149

181

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Local interstellar spectra (LIS) for protons, helium and antiprotons are built using the most recent experimental results combined with the 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 that provides modulated spectra for specific time periods of selected experiments to compare with the data; the HelMod parameters 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 1997-2015. 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.

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“…It is shown that the radial gradients are always positive while the latitudinal gradients are always negative as expected but with less magnitude than that predicted by earlier works (Potgieter et al 2001). Following de Simone et al (2011) and Gieseler & Heber (2016), Vos & Potgieter (2016) also used a numerical model to compute the spatial gradients of protons from 2006 to 2009. They concluded that although the drift effects were weaker than the predictions from those drift-dominated works due to the suppression by the excess diffusion, they still played an important role due to the significant decrease of HMF magnitude until the end of 2009.…”

Section: Introductionmentioning

confidence: 72%

Modulation of Galactic Cosmic Rays in the Inner Heliosphere, Comparing with PAMELA Measurements

Qin

Shen

2017

ApJ

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We develop a numerical model to study the time-dependent modulation of galactic cosmic rays (GCRs) in the inner heliosphere. In the model a time-delayed modified Parker heliospheric magnetic field (HMF) and a new diffusion coefficient model, NLGCE-F, from , are adopted. In addition, the latitudinal dependence of magnetic turbulence magnitude is assumed as ∼ (1 + sin 2 θ)/2 from the observations of Ulysses, and the radial dependence is assumed as ∼ r S , where we choose an expression of S as a function of the heliospheric current sheet (HCS) tilt angle. We show that the analytical expression used to describe the spatial variation of HMF turbulence magnitude agrees well with the Ulysses, Voyager 1, and Voyager 2 observations. By numerically calculating the modulation code we get the proton energy spectra as a function of time during the recent solar minimum, it is shown that the modulation results are consistent with the PAMELA measurements.

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Latitudinal and radial gradients of galactic cosmic ray protons in the inner heliosphere – PAMELA and Ulysses observations

Cited by 61 publications

References 24 publications

High-rigidity Forbush decreases: due to CMEs or shocks?

High-rigidity Forbush decreases: due to CMEs or shocks?

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

Modulation of Galactic Cosmic Rays in the Inner Heliosphere, Comparing with PAMELA Measurements

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