Stefan Lotz
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View article: Study of Evolution and Geo-effectiveness of Coronal Mass Ejection–Coronal Mass Ejection Interactions Using Magnetohydrodynamic Simulations with SWASTi Framework
Study of Evolution and Geo-effectiveness of Coronal Mass Ejection–Coronal Mass Ejection Interactions Using Magnetohydrodynamic Simulations with SWASTi Framework Open
The geo-effectiveness of coronal mass ejections (CMEs) is a critical area of study in space weather, particularly in the lesser-explored domain of CME–CME interactions and their geomagnetic consequences. This study leverages the Space Weat…
View article: Study of Evolution and Geo-effectiveness of CME-CME Interactions using MHD Simulations with SWASTi framework
Study of Evolution and Geo-effectiveness of CME-CME Interactions using MHD Simulations with SWASTi framework Open
The geo-effectiveness of Coronal Mass Ejections (CMEs) is a critical area of study in space weather, particularly in the lesser-explored domain of CME-CME interactions and their geomagnetic consequences. This study leverages the SWASTi fra…
View article: First results of the SA Agulhas II mobile mini-neutron monitor
First results of the SA Agulhas II mobile mini-neutron monitor Open
We present the first results of a new redesigned version of the mini-neutron monitor installed on the South African Research vessel, the SA Agulhas II. Measurements taken from the 2019/2020 relief voyages are presented. We show that the in…
View article: The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements
The Radial Variation of the Solar Wind Turbulence Spectra near the Kinetic Break Scale from Parker Solar Probe Measurements Open
In this study we examine the radial dependence of the inertial and dissipation range indices, as well as the spectral break separating the inertial and dissipation range in power density spectra of interplanetary magnetic field fluctuation…
View article: The effects of solar radio bursts on frequency bands utilised by the aviation industry in Sub-Saharan Africa
The effects of solar radio bursts on frequency bands utilised by the aviation industry in Sub-Saharan Africa Open
Solar radio bursts have been associated with a number of disruptions in avionic systems. The objective of this work is to develop solar radio burst interference thresholds which account for the technical specifications of aviation-related …
View article: Solar wind parameters and geomagnetic indices for severe (SYM-H < -100nT) geomagnetic storms over two solar cycles
Solar wind parameters and geomagnetic indices for severe (SYM-H < -100nT) geomagnetic storms over two solar cycles Open
Severe storms data set (1996-2019) Lotz, Grant, Davel (2022). This data set is curated from 1-minute time resolution OMNI [4] and INTERMAGNET [7] data, spanning the period 1996 - 2019. It consists of all geomagnetic storms that reached min…
View article: Solar wind parameters and geomagnetic indices for severe (SYM-H < -100nT) geomagnetic storms over two solar cycles
Solar wind parameters and geomagnetic indices for severe (SYM-H < -100nT) geomagnetic storms over two solar cycles Open
Severe storms data set (1996-2022) Lotz, Grant, Davel (2024). Changes from previous version: Previous version had errors in calculation of `HER_eh` and `ABK_eh`. The mistake is corrected in this version. This version includes storms from 1…
View article: Validating the LDi and LCi Indices in the Southern Hemisphere
Validating the LDi and LCi Indices in the Southern Hemisphere Open
The validation of the Local Disturbance index (LDi) and its first time derivative Local Current index (LCi) is performed in the Southern Hemisphere. Two South African magnetic observatories, Hermanus and Hartebeesthoek contributed data for…
View article: Data related to NAHAYO et al (2022), to appear in AGU Space Weather Journal (2022SW003092)
Data related to NAHAYO et al (2022), to appear in AGU Space Weather Journal (2022SW003092) Open
Geomagnetic data related to the publication by Nahayo, et al. (2022). The file ending in "event1.csv" is for the first event (October 2003) and the second file, filename ending "event2.csv" for the second event discussed in the paper (Marc…
View article: Data related to NAHAYO et al (2022), to appear in AGU Space Weather Journal (2022SW003092)
Data related to NAHAYO et al (2022), to appear in AGU Space Weather Journal (2022SW003092) Open
Geomagnetic data related to the publication by Nahayo, et al. (2022). The file ending in "event1.csv" is for the first event (October 2003) and the second file, filename ending "event2.csv" for the second event discussed in the paper (Marc…
View article: Space weather impacts on Geodesy
Space weather impacts on Geodesy Open
<p>Space Weather refers to events on the Sun that have an impact on terrestrial technologies and man-made satellites. The Global Navigation Satellite System (GNSS) is extensively used for Geodesy and is subject to Space Weather impac…
View article: Adaptations to a geomagnetic field interpolation method in Southern Africa
Adaptations to a geomagnetic field interpolation method in Southern Africa Open
Space weather and its impact on infrastructure presents a clear risk in the modern era, as evidenced by the adverse effects of geomagnetically induced currents (GICs) in power networks. To model GICs, ground-based geomagnetic field (B-fiel…
View article: Observing solar wind turbulence in the corona with ground-based radio telescopes
Observing solar wind turbulence in the corona with ground-based radio telescopes Open
<p>When point-like galactic and extragalactic radio sources are observed through the solar corona by ground-based radio telescopes, plasma density fluctuations in the turbulent solar wind scatter these photons, leading to an observed…
View article: Pairwise networks for feature ranking of a geomagnetic storm model
Pairwise networks for feature ranking of a geomagnetic storm model Open
Feedforward neural networks provide the basis for complex regression models that produce accurate predictions in a variety of applications. However, they generally do not explicitly provide any information about the utility of each of the …
View article: Geomagnetic Pulsations Driving Geomagnetically Induced Currents
Geomagnetic Pulsations Driving Geomagnetically Induced Currents Open
Geomagnetically induced currents (GICs) are driven by the geoelectric field induced by fluctuations of Earth's magnetic field. Drivers of intense GICs are often associated with large impulsive events such as coronal mass ejections. To a le…
View article: Machine Learning Techniques to Detect and Characterise Whistler Radio Waves
Machine Learning Techniques to Detect and Characterise Whistler Radio Waves Open
Lightning strokes create powerful electromagnetic pulses that routinely cause very low frequency (VLF) waves to propagate across hemispheres along geomagnetic field lines. VLF antenna receivers can be used to detect these whistler waves ge…
View article: Ensemble Estimation of Network Parameters: A Tool to Improve the Real-time Estimation of GICs in the South African Power Network
Ensemble Estimation of Network Parameters: A Tool to Improve the Real-time Estimation of GICs in the South African Power Network Open
It has long been known that large grounded conducting networks on the surface of Earth are affected by solar activity and geomagnetic storms. Power networks are such extensive grounded conductors and are susceptible to geomagnetically indu…
View article: dSECS: Including Variometers in Geomagnetic Field Interpolation
dSECS: Including Variometers in Geomagnetic Field Interpolation Open
One of the best tools we have in geophysical modelling is the ability to interpolate the horizontal geomagnetic field at the surface of the Earth. This is especially useful in regions, such as southern Africa, where there is a sparse array…
View article: Solar flare prediction with temporal convolutional networks
Solar flare prediction with temporal convolutional networks Open
Sequences are typically modelled with recurrent architectures, but growing research is finding convolutional architectures to also work well for sequence modelling [1]. We explore the performance of Temporal Convolutional Networks (TCNs) w…
View article: A neural network based method for input parameter selection
A neural network based method for input parameter selection Open
NNs yield predictions, without aiding understanding of input-output relationship
\nFully connected networks mix signal from all inputs as information flows through the network
\nInput parameter selection usually done
View article: Demonstrating the Use of a Class of Min‐Max Smoothers for <i>D</i> Region Event Detection in Narrow Band VLF Phase
Demonstrating the Use of a Class of Min‐Max Smoothers for <i>D</i> Region Event Detection in Narrow Band VLF Phase Open
This paper describes the use of a class of nonlinear smoothers for the identification of interesting phenomena in narrow band very low frequency (VLF) transmission phase caused by perturbation events in the D region of the ionosphere. The …
View article: Observations from SANSA’s geomagnetic network during the Saint Patrick’s Day storm of 17–18 March 2015
Observations from SANSA’s geomagnetic network during the Saint Patrick’s Day storm of 17–18 March 2015 Open
Geomagnetic storms are space weather events that result in a temporary disturbance of the earth’s magnetosphere caused by a solar wind that interacts with the earth’s magnetic field. We examined more closely how some southern African magne…
View article: The source regions of whistlers
The source regions of whistlers Open
We present a new method for identifying the source regions of lightning generated whistlers observed at a fixed location. In addition to the spatial distribution of causative lightning discharges, we calculate the transmission ratio of lig…
View article: Influences of various magnetospheric and ionospheric current systems on geomagnetically induced currents around the world
Influences of various magnetospheric and ionospheric current systems on geomagnetically induced currents around the world Open
Ground‐based observations of geomagnetic field ( B field) are usually a superposition of signatures from different source current systems in the magnetosphere and ionosphere. Fluctuating B fields generate geoelectric fields ( E fields), wh…
View article: Analysis of geomagnetic hourly ranges
Analysis of geomagnetic hourly ranges Open
In an attempt to develop better forecasts of geomagnetic activity, hourly ranges of geomagnetic data are analyzed with a focus on how the data are distributed. A lognormal distribution is found to be able to characterize the magnetic data …
View article: A solar-wind-driven empirical model of Pc3 wave activity at a mid-latitude location
A solar-wind-driven empirical model of Pc3 wave activity at a mid-latitude location Open
In this paper we describe the development of two empirical models of Pc3 wave activity observed at a ground station. The models are tasked to predict pulsation intensity at Tihany, Hungary, from the OMNI solar wind data set at 5 min time r…