Browsing by Author "13065440 - Strauss, Roelf Du Toit"
Now showing items 1-20 of 48
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Acceleration of galactic electrons at the solar wind termination shock and Voyager 1 observations
Potgieter, Marius S.; Prinsloo, P. Lourens; Strauss, R. Du Toit (PoS, 2017)Diffusive shock acceleration (DSA) , as an acceleration process for G alactic electrons at the solar wind termination shock (TS) , is investigated with a comprehensive numerical model which ... -
Acceleration of solar wind particles by traveling interplanetary shocks
Prinsloo, P.L.; Strauss, R.D.; Le Roux, J.A. (IOP Publishing, 2019)The acceleration of thermal solar wind (SW) protons at spherical interplanetary shocks driven by coronal mass ejections is investigated. The SW velocity distribution is represented using κ-functions, which are transformed ... -
Comparison of astrospheres around cool and hot stars
Scherer, K.; Ferreira, S.E.S.; Strauss, R.D.; Bomans, D.J.; Fichtner, H. (IOP Publishing, 2016)Simulations of astrospheres around hot and cool stars have recently move into the focus of scientific research. We describe here the differences between the astrospheres around hot and cool stars. While those around the ... -
Cosmic ray flux anisotropies caused by astrospheres
Scherer, K.; Strauss, R.D.; Ferreira, S.E.S.; Fichtner, H. (Elsevier, 2016)Huge astrospheres or stellar wind bubbles influence the propagation of cosmic rays at energies up to the TeV range and can act as small-scale sinks decreasing the cosmic ray flux. We model such a sink (in 2D) by a sphere ... -
Cosmic ray modulation beyond the heliopause: a hybrid modeling approach
Strauss, R.D.; Potgieter, M.S.; Ferreira, S.E.S.; Fichtner, H.; Scherer, K. (IOP Publishing, 2013)Results from a newly developed hybrid cosmic ray (CR) modulation model are presented. In this approach, the transport of CRs is computed by incorporating the plasma flow from a magnetohydrodynamic model for the heliospheric ... -
Cosmic rays in astrospheres
Scherer, K.; Van der Schyff, A.; Ferreira, S.E.S.; Strauss, R.D.; Bomans, D.J. (EDP Sciences, 2015)Context: Cosmic rays passing through large astrospheres can be efficiently cooled inside these “cavities” in the interstellar medium. Moreover, the energy spectra of these energetic particles are already modulated in front ... -
A detailed calculation of neutral hydrogen ionization frequencies used in turbulence transport models in the heliosphere
Engelbrecht, N.E.; Strauss, R.D. (EDP Sciences, 2015)It is generally accepted that the solar wind is significantly heated beyond ~10 AU by the turbulent decay of pickup ion generated Alfvénic fluctuations. Here, we present a detailed and general calculation of the pickup ion ... -
Energy spectra of carbon and oxygen with HELIOS E6: radial gradients of anomalous cosmic ray oxygen within 1 AU
Marquardt, J.; Potgieter, M.S.; Strauss, R.D.; Heber, B. (EDP Sciences, 2018)Context. Anomalous cosmic rays (ACRs) are well-suited to probe the transport conditions of cosmic rays in the inner heliosphere.We revisit the HELIOS data not only in view of the upcoming Solar Orbiter experiment but also ... -
Extracting the February 1956 ground level enhancement event from legacy cosmic ray recordings
Mattana, V.W.F.; Drevin, G.R.; Strauss, R.D. (Springer, 2018)Early continuous recordings of cosmic rays, as measured with Carnegie Type C Ionization Chambers, were made on rolls of photographic paper. This paper describes the extraction of the ionization data of the February 1956 ... -
Extracting the ground level enhancement event of February 1956 from Legacy cosmic ray recordings
Mattana, Vincent; Drevin, Günther; Strauss, Du Toit (IEEE, 2018)Early continuous recordings of cosmic rays, as measured with Carnegie Type C Ionization Chambers, were made on rolls of photographic paper. This paper describes the extraction of the ionization data of a ground level ... -
A generalized diffusion tensor for fully anisotropic diffusion of energetic particles in the heliospheric magnetic field
Effenberger, F.; Strauss, R.D.; Fichtner, H.; Scherer, K.; Barra, S.; Kleimann, J. (IOP Publishing, 2012)The spatial diffusion of cosmic rays in turbulent magnetic fields can, in the most general case, be fully anisotropic, i.e., one has to distinguish three diffusion axes in a local, field-aligned frame. We reexamine the ... -
Heliosheath processes and the structure of the heliopause: modeling energetic particles, cosmic rays, and magnetic fields
Pogorelov, N.V.; Potgieter, M.S.; Strauss, R.D.; Fichtner, H.; Czechowski, A. (Springer, 2017)This paper summarizes the results obtained by the team “Heliosheath Processes and the Structure of the Heliopause: Modeling Energetic Particles, Cosmic Rays, and Magnetic Fields” supported by the International Space Science ... -
The heliospheric transport and modulation of multiple charged anomalous oxygen revisited
Strauss, R.D.; Potgieter, M.S.; Ferreira, S.E.S. (EDP Sciences, 2010)Context. Since the crossings of the solar wind termination shock by the Voyager 1 and 2 spacecraft, much speculation has surrounded the acceleration mechanism and region where the anomalous cosmic ray component is accelerated. ... -
A hitch-hiker’s guide to stochastic differential equations: solution methods for energetic particle transport in space physics and astrophysics
Strauss, R. Du Toit; Effenberger, Frederic (Springer, 2017)In this review, an overview of the recent history of stochastic differential equations (SDEs) in application to particle transport problems in space physics and astrophysics is given. The aim is to present a helpful working ... -
Is the highest cosmic-ray flux yet to come?
Strauss, R.D.; Potgieter, M.S. (Springer, 2014)The recent 2009 solar-minimum period was characterized by a record-setting high Galactic cosmic-ray flux observed at Earth. This, along with the unexpected low heliospheric magnetic-field magnitude, caused this period ... -
Jovian electrons in the inner heliosphere: proposing a new source spectrum based on 30 years of measurements
Vogt, A.; Kopp, A.; Potgieter, M.S.; Strauss, R.D.; Heber, B. (EDP Sciences, 2018)Context. Since the Pioneer 10 flyby of Jupiter it has become well known that electrons of Jovian origin dominate the lower MeV range of charged energetic particles in the inner heliosphere. Aims. Because the Jovian source ... -
The mini-neutron monitor: a new approach in neutron monitor design
Strauss, Du Toit; Van der Merwe, Cobus; Kruger, Hendrik; Diedericks, Corrie; Kruger, Helena; Moloto, Katlego (EDP, 2020)The near-Earth cosmic ray flux has been monitored for more than 70 years by a network of ground-based neutron monitors (NMs). With the ever-increasing importance of quantifying the radiation risk and effects of cosmic rays ... -
Modeling anomalous cosmic ray oxygen gradients over successive solar cycles
Strauss, R.D.; Potgieter, M.S. (American Geophysical Union, 2010)Cosmic ray drift directions depend both on the charge of the particle population under consideration, as well as the heliospheric magnetic field polarity which oscillates within a ∼22 year cycle. The differences in the ... -
Modeling ground and space based cosmic ray observations
Strauss, R.D.; Potgieter, M.S.; Ferreira, S.E.S. (Elsevier, 2012)After entering our local astrosphere (called the heliosphere), galactic cosmic rays, as charged particles, are affected by the Sun’s turbulent magnetic field. This causes their intensities to decrease towards the inner ... -
Modeling the acceleration and modulation of anomalous cosmic ray oxygen
Strauss, R.D.; Potgieter, M.S.; Ferreira, S.E.S. (Elsevier, 2011)After the solar wind termination shock crossings of the Voyager spacecraft, the acceleration of anomalous cosmic rays has become a very contentious subject. In this paper we examine several topics pertinent to anomalous ...