A toxic amino acid, 2(S)3(R)-2-amino-3-hydroxypent-4-ynoic acid from the fungus Sclerotium rolfsii

Potgieter, H. C.; Vermeulen, Nicolaas M. J.; Potgieter, D.J.J.; Strauss, Heinrich F.

doi:10.1016/0031-9422(71)85083-5

Cited by 17 publications

(10 citation statements)

References 17 publications

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“…This improves our understanding of basic galactic propagation effects, as well as serving the purpose of establishing a reliable input spectrum for galactic electrons in the energy range of 1 MeV to 100 GeV for solar modulation studies. (For a review on the importance of the LIS for solar modulation studies, see Potgieter 2013. ) It is a rather fortuitous coincidence that 100 yr after the discovery of cosmic rays at Earth, Voyager 1 started to observe the LIS for the first time.…”

Section: Introductionmentioning

confidence: 99%

IMPLICATIONS OFVOYAGER 1OBSERVATIONS BEYOND THE HELIOPAUSE FOR THE LOCAL INTERSTELLAR ELECTRON SPECTRUM

Bisschoff

Potgieter

2014

ApJ

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Cosmic-ray observations made by the Voyager 1 spacecraft outside the dominant modulating influence of the heliosphere finally allow the comparison of computed galactic spectra with experimental data at lower energies. These computed spectra, based on galactic propagation models, can now be compared with observations at low energies by Voyager 1 and at high energies by the PAMELA space detector at Earth. This improves understanding of basic propagation effects and also provides solar modulation studies with reliable input spectra from 1 MeV to 100 GeV. We set out to reproduce the Voyager 1 electron observations in the energy range of 6-60 MeV, as well as the PAMELA electron spectrum above 10 GeV, using the GALPROP code. By varying the source spectrum and galactic diffusion parameters, specifically the rigidity dependence of spatial diffusion, we find local interstellar spectra that agree with both power-law spectra observed by Voyager 1 beyond the heliopause. The local interstellar spectrum between ∼1 MeV and 100 GeV indicates that it is the combination of two power laws, with E −(1.45±0.15) below ∼100 MeV and E −(3.15±0.05) above ∼100 MeV. A gradual turn in the spectral shape matching the power laws is found, between 2.0 ± 0.5) GeV and (100 ± 10) MeV. According to our simplified modeling, this transition is caused primarily by galactic propagation effects. We find that the intensity beyond the heliopause at 10 MeV is (350 ± 50) electrons m −2 s −1 sr −1 MeV −1 , decreasing to (50 ± 5) electrons m −2 s −1 sr −1 MeV −1 at 100 MeV.

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Section: Introductionmentioning

confidence: 99%

IMPLICATIONS OFVOYAGER 1OBSERVATIONS BEYOND THE HELIOPAUSE FOR THE LOCAL INTERSTELLAR ELECTRON SPECTRUM

Bisschoff

Potgieter

2014

ApJ

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“…All these physical processes play an important role in modulating GCR particles, but their relative importance and dominance vary according to the solar activity cycle and depend also on the solar magnetic polarity cycle, and of course on the GCR species. Potgieter et al (2014Potgieter et al ( , 2015 and Aslam et al (2019a) described the 3D numerical modulation model used for this study in detail, and the reviews from Potgieter (2013Potgieter ( , 2014bPotgieter ( , 2017) also explain the underlying theory for the global modulation of GCRs, especially during a relatively quiet heliosphere as has been observed for the past two solar cycles.…”

Section: Numerical Simulations Of Galactic Electron and Positron Spectramentioning

confidence: 95%

“…(iv) Spatial diffusion caused by scattering off random magnetic field irregularities. In this context, see reviews by Heber (2013), Kóta (2013) and Potgieter (1998Potgieter ( , 2013Potgieter ( , 2017. All these physical processes are considered important in modulating GCRs, although their relative importance and how this changes with solar activity and with reversals of the HMF polarity (e.g.…”

Section: Introductionmentioning

confidence: 99%

Time and Charge-Sign Dependence of the Heliospheric Modulation of Cosmic Rays

Aslam,

Bisschoff,

Ngobeni

et al. 2020

Preprint

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Simultaneous and continuous observations of galactic cosmic-ray electrons (e − ) and positrons (e + ) from the PAMELA and AMS 02 space experiments are most suitable for numerical modeling studies of the heliospheric modulation of these particles below 50 GeV. A well-established comprehensive three-dimensional (3D) modulation model is applied to compute full spectra for e − and e + with the purpose of reproducing the observed ratio e + /e − for a period which covers the previous long and unusual deep solar minimum activity and the recent maximum activity phase including the polarity reversal of the solar magnetic field. For this purpose the very local interstellar spectra for these particles were established first. Our study is focused on how the main modulation processes, including particle drifts, and other parameters such as the three major diffusion coefficients, had evolved, and how the corresponding charge-sign dependent modulation had occurred subsequently. The end result of our effort is the detailed reproduction of e + /e − from 2006 to 2015, displaying both qualitative and quantitative agreement with the main observed features. Particularly, we determine how much particle drifts is needed to explain the time dependence exhibited by the observed e + /e − during each solar activity phase, especially during the polarity reversal phase when no well-defined magnetic polarity was found.

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“…An overview of the reasons why the reduction of particle drift is required in the heliosphere was given by [9]. As illustrated above, it can be done explicitly by simply assuming…”

Section: P mentioning

confidence: 99%

The effects of particle drifts on the modulation of galactic electrons in the global heliosphere

Nndanganeni¹,

Potgieter²

2016

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

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A toxic amino acid, 2(S)3(R)-2-amino-3-hydroxypent-4-ynoic acid from the fungus Sclerotium rolfsii

Cited by 17 publications

References 17 publications

IMPLICATIONS OFVOYAGER 1OBSERVATIONS BEYOND THE HELIOPAUSE FOR THE LOCAL INTERSTELLAR ELECTRON SPECTRUM

IMPLICATIONS OFVOYAGER 1OBSERVATIONS BEYOND THE HELIOPAUSE FOR THE LOCAL INTERSTELLAR ELECTRON SPECTRUM

Time and Charge-Sign Dependence of the Heliospheric Modulation of Cosmic Rays

The effects of particle drifts on the modulation of galactic electrons in the global heliosphere

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