Modelling heliospheric current sheet drift in stochastic cosmic ray transport models

Strauss, R. D.; Potgieter, M. S.; Büsching, I.; Kopp, A.

doi:10.1007/s10509-012-1003-z

Cited by 82 publications

(90 citation statements)

References 33 publications

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“…In particular, Figure 12 shows that the HH CR flux is sensitive to TA variations even at about 60 • . The TA threshold effect could be due to the disruption of the drift process when the TA increases, as proposed by Strauss et al (2012). …”

Section: Solar Modulation Versus Drift Effectsmentioning

confidence: 94%

“…During a solar rotation, the HCS moves by changing its heliographic latitude. The average excursion, measured from the heliographic equator, is referred to as the tilt angle (TA; e.g., Hoeksema et al 1982), which can be considered as a proxy for drift effects on CRs (e.g., Jokipii & Thomas 1981;Kota & Jokipii 1983;Wibberenz et al 2001;Strauss et al 2012) and it is widely used in modeling and data interpretation (e.g., Christon & Stone 1986;Cliver & Ling 2001;El-Borie 2001;Alanko-Huotari et al 2007;Badruddin et al 2007). The modulation effects of the HCS and other drifts, the subsequent 22 yr cycle, and the corresponding charge-sign dependence in the inner heliosphere have been investigated by means of theoretical modeling (e.g., Potgieter & Ferreira 2001).…”

Section: Introductionmentioning

confidence: 99%

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Drift Effects on the Galactic Cosmic Ray Modulation

Laurenza

Vecchio

Storini

et al. 2014

ApJ

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Cosmic ray (CR) modulation is driven by both solar activity and drift effects in the heliosphere, although their role is only qualitatively understood as it is difficult to connect the CR variations to their sources. In order to address this problem, the Empirical Mode Decomposition technique has been applied to the CR intensity, recorded by three neutron monitors at different rigidities (Climax, Rome, and Huancayo-Haleakala (HH)), the sunspot area, as a proxy for solar activity, the heliospheric magnetic field magnitude, directly related to CR propagation, and the tilt angle (TA) of the heliospheric current sheet (HCS), which characterizes drift effects on CRs. A prominent periodicity at ∼six years is detected in all the analyzed CR data sets and it is found to be highly correlated with changes in the HCS inclination at the same timescale. In addition, this variation is found to be responsible for the main features of the CR modulation during periods of low solar activity, such as the flat (peaked) maximum in even (odd) solar cycles. The contribution of the drift effects to the global Galactic CR modulation has been estimated to be between 30% and 35%, depending on the CR particle energy. Nevertheless, the importance of the drift contribution is generally reduced in periods nearing the sunspot maximum. Finally, threshold values of ∼40 • , ∼45 • , and >55 • have been derived for the TA, critical for the CR modulation at the Climax, Rome, and HH rigidity thresholds, respectively.

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Section: Solar Modulation Versus Drift Effectsmentioning

confidence: 94%

Section: Introductionmentioning

confidence: 99%

Drift Effects on the Galactic Cosmic Ray Modulation

Laurenza

Vecchio

Storini

et al. 2014

ApJ

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“…This electric field causes particles to experienceÉ B drift, analogous with corotation of field lines. In the case of a wavy HCS (see, e.g., Burger 2012;Pei et al 2012;Strauss et al 2012), especially with greater heliocentric distance, an assumed radial solar wind flow will no longer be wholly in the current sheet plane, requiring more detailed analysis of possible reconnection. Observations estimate the HCS thickness to be in the region of between 5000 and 40,000 km at 1 au (see, e.g., Winterhalter et al 1994;Eastwood et al 2002).…”

Section: Hcs Modelmentioning

confidence: 99%

Solar Energetic Particle Transport Near a Heliospheric Current Sheet

Battarbee

Dalla

Marsh

2017

ApJ

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Solar energetic particles (SEPs), a major component of space weather, propagate through the interplanetary medium strongly guided by the interplanetary magnetic field (IMF). In this work, we analyze the implications that a flat Heliospheric Current Sheet (HCS) has on proton propagation from SEP release sites to the Earth. We simulate proton propagation by integrating fully 3D trajectories near an analytically defined flat current sheet, collecting comprehensive statistics into histograms, fluence maps, and virtual observer time profiles within an energy range of 1-800 MeV. We show that protons experience significant current sheet drift to distant longitudes, causing time profiles to exhibit multiple components, which are a potential source of confusing interpretations of observations. We find that variation of the current sheet thickness within a realistic parameter range has little effect on particle propagation. We show that the IMF configuration strongly affects the deceleration of protons. We show that in our model, the presence of a flat equatorial HCS in the inner heliosphere limits the crossing of protons into the opposite hemisphere.

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“…SDE-based models have been used to study the transport of pickup ions (Fichtner et al, 1996), solar energetic particles (Dröge et al, 2010), the propagation of Galactic and Jovian electrons (Strauss et al, 2011a), and other aspects of CR modulation (e.g. Pei et al 2010;Strauss et al, 2011bStrauss et al, , 2012Luo et al, 2011Luo et al, , 2013aLuo et al, , 2013b. Some historical and contemporary models are discussed by e.g.…”

Section: Introductionmentioning

confidence: 99%

The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

Raath

Potgieter

Strauss

et al. 2016

Advances in Space Research

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A numerical model for the solar modulation of cosmic rays, based on the solution of a set of stochastic differential equations, is used to illustrate the effects of modifying the heliospheric magnetic field, particularly in the polar regions of the heliosphere. To this end, the differences in the modulation brought about by each of three choices for the heliospheric magnetic field, i.e. the unmodified Parker field, the Smith-Bieber modified field, and the Jokipii-Kóta modified field, are studied. It is illustrated that both the Jokipii-Kóta and Smith-Bieber modifications are effective in modifying the Parker field in the polar regions. In addition, it is argued that the modification of Smith and Bieber is based on observational evidence and has a firm physical basis, while these motivations are lacking in the case of the Jokipii-Kóta modification. From a cosmic ray modulation point of view, we found the Smith-Bieber modification to be the most suitable choice for modifying the heliospheric magnetic field. The features and effects of these three modifications are illustrated both qualitatively and quantitatively. It is also shown how the Smith-Bieber modified field can be applied in cosmic ray modulation models to reproduce observational cosmic ray proton spectra from the PAMELA mission during the solar minimum of 2006 -2009. These results are compared with those obtained in previous studies of this unusual solar minimum activity period and found to be in good qualitative agreement.

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Modelling heliospheric current sheet drift in stochastic cosmic ray transport models

Cited by 82 publications

References 33 publications

Drift Effects on the Galactic Cosmic Ray Modulation

Drift Effects on the Galactic Cosmic Ray Modulation

Solar Energetic Particle Transport Near a Heliospheric Current Sheet

The effects of magnetic field modifications on the solar modulation of cosmic rays with a SDE-based model

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