Browsing by Author "Burger, R.A."
Now showing items 1-20 of 24
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An ab initio approach to modelling time-dependent cosmic-ray modulation in the heliosphere
Moloto, K.D. (North-West University (South Africa), 2020)The ab initio approach to cosmic ray modulation places a strong, primary emphasis on understanding the basic causes of cosmic-ray modulation. This requires knowledge and an understanding of both the large and small-scale ... -
An ab initio approach to the heliospheric modulation of galactic cosmic rays
Minnie, Jaco (North-West University, 2006)In the present study we aim to further our understanding of charged particle transport in a magnetized medium. To this end, we perform direct numerical simulations of particle transport in a turbulent magnetic field. From ... -
An AB initio model for cosmic-ray modulation
Engelbrecht, N.E.; Burger, R.A. (IOP Publishing, 2013)A proper understanding of the effects of turbulence on the diffusion and drift of cosmic rays (CRs) is of vital importance for a better understanding of CR modulation in the heliosphere. This study presents an ab initio ... -
An AB initio model for the modulation of galactic cosmic-ray electrons
Engelbrecht, N.E.; Burger, R.A. (IOP Publishing, 2013)The modulation of galactic cosmic-ray electrons is studied using an ab initio three-dimensional steady state cosmicraymodulation code in which the effects of turbulence on both the diffusion and drift of these cosmic-rays ... -
Analysis of selected observations of magnetic turbulence in the solar wind
McKee, S.R. (North-West University, 2020)Models for the modulation of galactic cosmic rays, such as those used to study space weather (see discussion by Moloto et al., 2018), require as input a di usion tensor, which in turn depends on the magnetic turbulence ... -
Comparison of different analytic heliospheric magnetic field configurations and their significance for the particle injection at the termination shock
Scherer, K.; Burger, R.A.; Fichtner, H.; Effenberger, F.; Wiengarten, T. (EDP Sciences, 2010) -
Cosmic ray diffusion tensor throughout the heliosphere
Pei, C.; Burger, R.A.; Bieber, J.W.; Breech, B.; Clem, J. (American Geophysical Union, 2010)We calculate the cosmic ray diffusion tensor based on a recently developed model of magnetohydrodynamic (MHD) turbulence in the expanding solar wind. Parameters of this MHD model are tuned by using published observations ... -
Cosmic ray modulation with a Fisk-type heliospheric magnetic field and a latitude-dependent solar wind speed
Hitge, M.; Burger, R.A. (Elsevier, 2009)The effect of a latitude-dependent solar wind speed on a Fisk heliospheric magnetic field [Fisk, L. A. Motion of the footpoints of heliospheric magnetic field lines at the Sun: implications for recurrent energetic particle ... -
Cosmic-ray modulation: an ab initio approach
Engelbrecht, N.E.; Burger, R.A. (Springer Verlag, 2014)A better understanding of cosmic-ray modulation in the heliosphere can only be gained through a proper understanding of the effects of turbulence on the diffusion and drift of cosmic rays. We present an ab initio model ... -
The effect of a Fisk-Parker hybrid magnetic field on cosmic rays in the heliosphere
Krüger, Tjaart Petrus Jakobus (North-West University, 2005)The existence of a Fisk-type heliospheric magnetic field (HMF) is one of the most debated questions in cosmic-ray modulation. Recently, Burger and Hitge [2004] developed a divergence-free Fisk-Parker hybrid magnetic field ... -
The effect of the heliospheric current sheet on cosmic-ray modulation
Moloto, Katlego Daniel (North-West University (South Africa), Potchefstroom Campus, 2015)The heliospheric current sheet is a dominant feature of the heliosphere. As solar activity increases, the tilt angle of the current sheet increases, and so does the region swept out by this structure, to cover most of ... -
Effects of various dissipation range onset models on the 26-day variations of low-energy galactic cosmic-ray electrons
Engelbrecht, N.E.; Burger, R.A. (Elsevier, 2010)The effect of various models presented by Leamon et al. (2000) for the dissipation range cutoff wavenumber on the 26-day variations of galactic cosmic-ray electrons in a Fisk-Parker hybrid field is investigated, by means ... -
A Fisk-Parker hybrid heliospheric magnetic field with a solar-cycle dependence
Burger, R.A.; Krüger, T.P.J.; Hitge, M.; Engelbrecht, N.E. (IOP Publishing, 2008)We present a refinement of the Fisk-Parker hybrid field of Burger and Hitge which now includes a region bordering the solar rotational equator where magnetic field footpoint motion occurs only through diffusive reconnection. ... -
A general time-dependent stochastic method for solving Parker's transport equation in spherical coordinates
Pei, C.; Burger, R.A.; Bieber, J.W.; Clem, J. (American Geophysical Union, 2010) -
A generalized Fisk-type HMF: implications of spatially dependent photospheric differential rotation
Steyn, P.J.; Burger, R.A. (IOP Publishing, 2020)The existence of a Fisk-type heliospheric magnetic field (HMF) has been debated ever since Fisk proposed an alternative to the traditional view of the HMF first proposed by Parker. Several modifications of the original ... -
An investigation into a generalized Fisk-type heliospheric magnetic field
Steyn, Petrus Johannes (North-West University (South Africa), Potchefstroom Campus, 2016)The existence of a Fisk-type heliospheric magnetic field (HMF) has been contested since the Fisk field [Fisk, 1996] challenged the traditional view of the HMF first proposed by Parker [1958]. Several modifications of the ... -
Long-term variation in cosmic-ray modulation
Mosotho, Moshe Godfrey (North-West University (South Africa), 2017)The transport of cosmic rays inside the heliosphere can be described b the Parker equation (Parker, 1965). Since there are no full analytica solutions to the Parker equation, two first-order approximate solutions o the ... -
Modeling drift along the heliospheric wavy neutral sheet
Burger, R.A. (IOP Publishing, 2012)Drift along the wavy heliospheric neutral sheet is believed to play an important role in cosmic-ray modulation and can explain the peaked versus flat intensity profiles during consecutive solar magnetic epochs. Modulation ... -
On the heliospheric diffusion tensor and its effect on 26-day recurrent cosmic-ray variations
Engelbrecht, Nicholas Eugéne (North-West University, 2008)A first attempt at an ab initio steady-state three-dimensional modulation model for galactic cosmic ray electrons, utilizing expressions adapted from the work of Teufel and Schlickeiser [2003] and Shalchi et al. [2004a] ... -
Possible evidence for a Fisk-type heliospheric magnetic field. 1. Analyzing Ulysses/Ket electron observations
Sternal, O.; Engelbrecht, N.E.; Burger, R.A.; Ferreira, S.E.S.; Potgieter, M.S.; Kopp, A. (IOP Publishing, 2011)The propagation of energetic charged particles in the heliospheric magnetic field is one of the fundamental problems in heliophysics. In particular, the structure of the heliospheric magnetic field remains an unsolved ...