arXiv subjects

Du Toit Strauss

Publications and source records attributed to Du Toit Strauss.

6 recordsLinked to original sources

arXiv2026

Probing the Solar Corona and the Solar Wind Using Angular Broadening Observations with the SKA

Angular broadening observations of compact radio sources provide a powerful method for probing the solar corona and solar wind. Such observations enable studies of the phase structure function, turbulence amplitude, intermediate-scale density fluctuations, solar-wind heating rates, and dissipation scales. When a compact radio source is observed through coronal or solar-wind plasma, several observable effects can arise: (1) the apparent source size increases because of scattering by turbulent plasma, producing angular broadening; (2) the source flux density decreases because of scattering and absorption; (3) the observed angular broadening can be anisotropic, reflecting anisotropic turbulence in the corona and solar wind; and (4) the position angle of the anisotropy, measured from north through east, can help infer the orientation of the coronal magnetic field. These effects provide insights into the physical processes governing the solar wind and its interaction with electromagnetic waves, and they offer constraints on coronal turbulence and magnetic-field structure. At present, angular broadening studies remain limited and have mostly focused on very bright radio sources such as Tau A. The unprecedented sensitivity and angular resolution of the Square Kilometre Array are expected to greatly expand the number of suitable background sources, opening a new window on the solar corona, solar wind, and heliosphere.

astro-ph.SR↗

arXiv2025

Type II and Type III Solar Radio Burst Classification Using Transfer Learning

The Sun periodically emits intense bursts of radio emission known as solar radio bursts (SRBs). These bursts can disrupt radio communications and be indicative of large solar events that can disrupt technological infrastructure on Earth and in space. The risks posed by these events highlight the need for automated SRB classification, providing the potential to improve event detection and real-time monitoring. This would advance the techniques used to study space weather and related phenomena. A dataset containing images of radio spectra was created using data recorded by the Compound Astronomical Low frequency Low cost Instrument for Spectroscopy and Transportable Observatory (e-Callisto) network. This dataset comprises three categories: empty spectrograms; spectrograms containing Type II SRBs; and spectrograms containing Type III SRBs. These images were used to fine-tune several popular pre-trained deep learning models for classifying Type II and Type III SRBs. The evaluated models included VGGnet-19, MobileNet, ResNet-152, DenseNet-201, and YOLOv8. Testing the models on the test set produced F1 scores ranging from 87\% to 92\%. YOLOv8 emerged as the best-performing model among them, demonstrating that using pre-trained models for event classification can provide an automated solution for SRB classification. This approach provides a practical solution to the limited number of data samples available for Type II SRBs.

astro-ph.SR↗

arXiv2022

Galactic Cosmic Rays and Solar Energetic Particles in Cis-Lunar Space: Need for contextual energetic particle measurements at Earth and supporting distributed observations

The particle and radiation environment in cis-lunar space is becoming increasingly important as more hardware and human assets occupy various orbits around the Earth and space exploration efforts turn to the Moon and beyond. Since 2020, the total number of satellites in orbit has approximately doubled, highlighting the growing dependence on space-based resources. Through NASA's upcoming Artemis missions, humans will spend more time in cis-lunar space than ever before supported by the expansive infrastructure required for extended missions to the Moon, including a surface habitat, a communications network, and the Lunar Gateway. This paper focuses on galactic cosmic rays (GCRs) and solar energetic particles (SEPs) that create a dynamic and varying radiation environment within these regions. GCRs are particles of hundreds of MeV/nucleon (MeV/n) and above generated in highly energetic astrophysical environments in the Milky Way Galaxy, such as supernovae and pulsars, and beyond. These particles impinge isotropically on the heliosphere and are filtered down to 1 AU, experiencing modulation in energy and intensity on multiple timescales, from hours to decades, due to the solar magnetic cycle and other transient phenomena. SEPs are particles with energies up to thousands of MeV/n that are accelerated in eruptive events on the Sun and flood the inner heliosphere causing sudden and drastic increases in the particle environment on timescales of minutes to days. This paper highlights a current and prospective future gap in energetic particle measurements in the hundreds of MeV/n. We recommend key observations near Earth to act as a baseline as well as distributed measurements in the heliosphere, magnetosphere, and lunar surface to improve the scientific understanding of these particle populations and sources.

astro-ph.IM↗

arXiv2021

High-altitude polar NM with the new DAQ system as a tool to study details of the cosmic-ray induced nucleonic cascade

A neutron monitor (NM) is, since the 1950s, a standard ground-based detector whose count rate reflects cosmic-ray variability. The worldwide network of NMs forms a rough spectrometer for cosmic rays. Recently, a brand-new data acquisition (DAQ) system has been installed on the DOMC and DOMB NMs, located at the Concordia research station on the Central Antarctic plateau. The new DAQ system digitizes, at a 2-MHz sampling rate, and records all individual pulses corresponding to secondary particles in the detector. An analysis of the pulse characteristics (viz. shape, magnitude, duration, waiting time) has been performed, and several clearly distinguishable branches were identified: (A) corresponding to signal from individual secondary neutrons; (B) representing the detector's noise; (C) double pulses corresponding to the {shortly separated nucleons of the same} atmospheric cascades; (D) very-high multiple pulses which are likely caused by atmospheric muons; and (E) double pulses potentially caused by contamination of the neighbouring detector. An analysis of the waiting time distributions has revealed two clearly distinguishable peaks: peak (I) at about 1 msec being related to the intra-cascade diffusion and thermalisation of secondary atmospheric neutrons; and peak (II) at 30--1000 msec corresponding to individual atmospheric cascades. This opens a new possibility to study spectra of cosmic-ray particles in a single location as well as details of the cosmic-ray induced atmospheric cascades, using the same dataset.

astro-ph.IM↗

arXiv2020

The mini-neutron monitor: A new approach in neutron monitor design

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 for, e.g., air and space-travel, it is essential to continue operating the existing NM stations, while expanding this crucial network. In this paper, we discuss a smaller and cost-effective version of the traditional NM, the mini-NM. These monitors can be deployed with ease, even to extremely remote locations, where they operate in a semi-autonomous fashion. We believe that the mini-NM, therefore, offers the opportunity to increase the sensitivity and expand the coverage of the existing NM network, making this network more suitable to near-real-time monitoring for space weather applications. In this paper, we present the technical details of the mini-NM's design and operation, and present a summary of the initial tests and science results.

physics.ins-det↗

arXiv2017

Towards a greater understanding of the reduction of drift coefficients in the presence of turbulence

Drift effects play a significant role in the transport of charged particles in the heliosphere. A turbulent magnetic field is also known to reduce the effects of particle drifts. The exact nature of this reduction, however, is not clear. This study aims to provide some insight into this reduction, and proposes a relatively simple, tractable means of modelling it that provides results in reasonable agreement with numerical simulations of the drift coefficient in a turbulent magnetic field.

physics.space-ph↗