Time-Dependent Modulation of Cosmic Rays in the Heliosphere

Manuel, Rex; Ferreira, S. E. S.; Potgieter, M. S.

doi:10.1007/s11207-013-0445-y

Cited by 65 publications

(53 citation statements)

References 64 publications

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“…Following this approach, the HMF's propagation time calculates to ∼10 months. In addition to these solar activity variables, the position of the TS also varies with time due to the dynamic nature of the heliosphere (e.g., Richardson & Wang 2011), which affects modulation intensities even at Earth (see, e.g., Manuel et al 2014). All of these parameters have been accounted for in the model and are summarized in Table 1.…”

Section: Calculating the Intrinsic Parametersmentioning

confidence: 99%

New Modeling of Galactic Proton Modulation During the Minimum of Solar Cycle 23/24

Vos

Potgieter

2015

ApJ

162

156

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During the recent prolonged solar minimum of cycle 23/24, the PAMELA detector measured 27-day averaged Galactic proton energy spectra over the energy range that is important for solar modulation. By comparing these spectra to computed spectra from a three-dimensional model that contains all of the important heliospheric modulation processes, the recent minimum can be studied in detail from a modulation perspective. This was done by setting up a realistic heliosphere in the model, and reproducing a representative selection of seven intermittent PAMELA spectra, separated by approximately six months, from 2006 July to 2009 December. Additionally, a new very local interstellar proton spectrum was constructed using measurements below 600 MeV from Voyager 1, taken beyond the heliopause, combined with PAMELA and AMS-02 measurements above 30 GeV at the Earth. As a result of the extreme minimum modulation conditions that governed the recent solar minimum, the highest ever Galactic cosmic ray spectrum at Earth was observed by PAMELA at the end of 2009. It was found that, apart from the self-consistent changes in the heliospheric current sheet and the heliospheric magnetic field over time, additional increases in the mean free paths during this period were required below~4 GV in order to reproduce the intensities observed by PAMELA.

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Section: Calculating the Intrinsic Parametersmentioning

confidence: 99%

New Modeling of Galactic Proton Modulation During the Minimum of Solar Cycle 23/24

Vos

Potgieter

2015

ApJ

162

156

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“…Above the energy range where cosmic rays are directly affected by inner heliospheric processes (see, e.g., Florinski et al 2013;Manuel et al 2014;Florinski et al 2015), a statistically significant anisotropy has been observed by a variety of experiments, sensitive to different energy ranges (from tens of GeV to a few PeV), located on or below the Earth's surface in the northern hemisphere (Nagashima et al 1998;Hall et al 1999;Amenomori et al 2005Amenomori et al , 2006Guillian et al 2007;Abdo et al 2009;Aglietta et al 2009;Zhang et al 2009;Munakata et al 2010;Amenomori et al 2011;de Jong et al 2011;Cui et al 2011;Bartoli et al 2015) and in the southern hemisphere (Abbasi et al 2010a(Abbasi et al , 2011a(Abbasi et al , 2012bAartsen et al 2013b).…”

Section: Introductionmentioning

confidence: 99%

Cosmic-Ray Small-Scale Anisotropies and Local Turbulent Magnetic Fields

López-Barquero

Farber

Desiati

et al. 2016

ApJ

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Cosmic-ray anisotropy has been observed in a wide energy range and at different angular scales by a variety of experiments over the past decade. However, no comprehensive or satisfactory explanation has been put forth to date. The arrival distribution of cosmicrays at Earth is the convolution of the distribution of their sources and of the effects of geometry and properties of the magnetic field through which particles propagate. It is generally believed that the anisotropy topology at the largest angular scale is adiabatically shaped by diffusion in the structured interstellar magnetic field. On the contrary, the medium-and small-scale angular structure could be an effect of nondiffusive propagation of cosmicrays in perturbed magnetic fields. In particular, a possible explanation forthe observed small-scale anisotropy observed at theTeV energy scalemay be the effect of particle propagation in turbulent magnetized plasmas. We perform numerical integration of test particle trajectories in low-β compressible magnetohydrodynamic turbulence to study how the cosmicrays' arrival direction distribution is perturbed when they stream along the local turbulent magnetic field. We utilize Liouville's theorem for obtaining the anisotropy at Earth and provide the theoretical framework for the application of the theorem in the specific case of cosmic-ray arrival distribution. In this work, we discuss the effects on the anisotropy arising from propagation in this inhomogeneous and turbulent interstellar magnetic field.

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“…In [18] it was shown that for the GCR intensity near the Earth the same was true for all other phases of solar cycle except the years near solar maxima. So the conclusion was made that in the models used, similar to [10,28,24], the drift contribution was large for both polarities and it was emphasizes that particle drifts result in the significant part of the 11-year variation of the GCR intensity in the whole heliosphere.…”

Section: Pos(icrc2015)176mentioning

confidence: 99%

“…Already the first full drift calculations [10,28] showed that drift tended to reduce modulation by significant factor for both polarity cases and now it is a common knowledge for the modeling community (see [16,24]). Recently in [12], first, the parameters of the models were chosen in such a way that the calculations basically described the latitude, radial and energy dependencies of the observations for the HMF polarities, respectively, in 1987 and 1997 solar minima.…”

Section: Pos(icrc2015)176mentioning

confidence: 99%

On the causes and mechanisms of the long-term variations in the GCR characteristics

Крайнев¹,

Kóta²,

Potgieter³

2016

Proceedings of the 34th International Cosmic Ray Conference — PoS(ICRC2015)

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We argue that the degree of understanding the causes and mechanisms of the long-term variations (11-year and 22-year) in the galactic cosmic rays (GCR) characteristics is still insufficient and to improve it we need new approaches and methods. For the time being there is a long-lasting controversy on how these long-term variations, observed for more than 50 years in the inner heliosphere, are formed. It is widely believed that the 11-year variation is due entirely to the toroidal branch of solar activity (the area and number of sunspots, the strength of the heliospheric magnetic field etc) because of the diffusion, convection and adiabatic energy loss, while the much smaller 22-year variation is caused by the particle drifts connected with the poloidal branch of solar activity (the high-latitude solar magnetic fields). At the same time, both past and more recent numerical simulations indicate that the contribution of particle drifts could be significant for both 22-and 11-year variations in the GCR intensities. However, even those who agree on the significant influence of drifts appear to have different perceptions on the mechanisms of this influence. In this paper, we present an analysis of the possible causes of the first point of view (small role of drifts in the 11-year GCR variation) and the reasons why one can expect the significant contribution of the processes connected with the poloidal branch of solar activity in both types of the long-term variations of the GCR characteristics. Then we briefly discuss some numerical methods suggested in the past and recently and the approaches and perspectives for the sought-for methods are considered.

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Time-Dependent Modulation of Cosmic Rays in the Heliosphere

Cited by 65 publications

References 64 publications

New Modeling of Galactic Proton Modulation During the Minimum of Solar Cycle 23/24

New Modeling of Galactic Proton Modulation During the Minimum of Solar Cycle 23/24

Cosmic-Ray Small-Scale Anisotropies and Local Turbulent Magnetic Fields

On the causes and mechanisms of the long-term variations in the GCR characteristics

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