The Space Physics Group carries out research in order to add to the present understanding of plasma behaviour in the Earth's ionosphere and magnetosphere and its impact on Earth. Research methods include theoretical, modelling, and data analysis studies, the results of which are presented at conferences and published in ISI indexed journals.  Researchers in the group collaborate with researchers at universities and research institutes, both locally and internationally. 

The current research fields and collaborations include the following:

1- Theoretical studies of waves in dusty plasmas 
The study of plasmas with massive negatively charged dust grains has become the focus of research in the past decade due to the widespread occurrence of such plasmas in space and astrophysical environments. The theoretical prediction of the existence of the low phase velocity (in comparison with ion and electron thermal speeds) dust acoustic wave (DAW) has been the starting point of many theoretical studies. The existence of the DAW has been experimentally confirmed in a number of laboratory experiments. The linear theory is valid only when the wave amplitude is small. However there are processes by which unstable modes can saturate and attain large amplitudes and nonlinearities can no longer be ignored. Both linear and nonlinear properties of the DAW are being theoretically studied. This research is being carried out in collaboration with researchers at the University of KwaZulu–Natal and the Indian Institute of Geomagnetism (IIG) in Mumbai, India.

2- Studies of ULF waves using ground-based and satellite data
The objective of this research is to gain a better understanding of the magneto-hydrodynamic (MHD) wave modes responsible for the propagation of ultra low frequency (ULF) geomagnetic pulsations within the Earth’s magnetosphere. In particular, uncertainty exists about the manner in which Pi2 geomagnetic pulsations propagate from the source region in the near Earth plasmasheet to the low latitude ground. Consequently, a specific objective is to shed light on this problem by making comparative studies of Pi2 pulsations observed above and below the ionosphere. Data from the CHAMP fluxgate magnetometer is used to observe pulsation signatures in the region above the ionosphere, while data from the Hermanus Magnetic Observatory and other ground stations provides information on the signatures below the ionosphere. Studies of magnetospheric substorms and their related space weather effects are currently regarded as an essential aspect of magnetospheric physics research. Low latitude Pi2 geomagnetic pulsations play an important role in this research, since they are considered to be one of the most reliable and accurate indicators of substorm onsets. This research is being carried out in collaboration with researchers at the GeoForschungsZentrum, Potsdam, Germany. For further details see Geomagnetic Pulsations.

3- Pc5 field line resonant pulsation observations using the SuperDARN HF-radars
The Super Dual Auroral Radar Network (SuperDARN) is an international collaborative network of HF radars that monitors ionospheric plasma convection over the majority of the northern and southern polar regions. SuperDARN currently is comprised of 9 radars in the northern hemisphere and 5 radars in the southern hemisphere. South Africa’s involvement in SuperDARN is made through the Southern Hemisphere Auroral Radar Experiment (SHARE). SHARE is a collaboration involving the University of KwaZulu-Natal (UKZN) in Durban, the North-West University (NWU) in Potchefstroom, the British Antarctic Survey (BAS) in Cambridge, UK, the Johns Hopkins University Applied Physics Laboratory (APL) in Baltimore, USA and recently also the HMO. The main objective of SuperDARN is to measure ionospheric plasma convection with relatively high spatial and temporal resolution on a global scale. The overlapping fields of view of the radar pairs provide independent plasma drift measurements in two directions. Each of the radars in a SuperDARN pair has a 16-beam field of view, so the radar pair has, in principle, 256 beam intersection cells. Each beam measures the projection of the full velocity vector onto the beam, and from the two overlapping velocity measurements the full vector can be reconstructed, or "merged." One of the remarkable results of the velocity data was the radar’s ability to measure and characterise Pc5 field-line resonant pulsations. Although the structure and characterisation of these events is well known, the cause and propagation mechanism is still the topic of much debate.  A co-ordinated investigation involving HF-radar, magnetometer and satellite data is being carried out in order to better understand these dynamics.

4- Ionospheric characterisation using dual frequency GPS observations
The phase delay in global positioning system (GPS) satellite radio signals can be used to determine certain parameters of the ionosphere.  Recent research at the HMO has focused on the use of GPS signals received by the ground-based network of South African dual frequency GPS receivers to provide a denser and more timely characterisation of the total electron content of the ionosphere than is currently available using only ionosonde data.  This work is being expanded to determine profiles of ionospheric electron density using the technique of ionospheric tomography through the integration of GPS data, ionosonde data, and occultation data from low earth orbit (LEO) satellites using GPS signals.  Besides the purely scientific interests, the ionospheric soundings using GPS signals are of practical application for the provision of HF predictions for radio communications and radio direction finding.  The results of this research will also be important for characterising the ionosphere in the planning for and operation of the SKA project.  This research is being carried out in collaboration with researchers at the Department of Electronic and Electrical Engineering, University of Bath, UK and at the Institute of Radio engineering and Electronics (IRE) of the Russian Academy of Science (RAS). For further details see Ionospheric characterisation using dual frequency GPS observations.

5- Ionospheric data and modelling using neural networks
During 2004, the HMO took over the management of the Hermann Ohlthaver Institute for Aeronomy (HOIA), based within the Department of Physics and Electronics at Rhodes University in Grahamstown. The key function of HOIA was to manage and quality control the South African ionospheric data. Data from the 3 South African ionosondes are archived and distributed to the scientific community. This function is continuing in its previous form but now forms one of the services the HMO provides.

In addition, researchers at HOIA pioneered the technique of neural networks (NNs) for ionospheric modelling. From this research a South African Bottomside Ionospheric Model, called the SABIM model, has been developed and is currently being implemented in the Direction Finding Systems in industry. The SABIM model predicts the complete electron density profile of the bottomside ionosphere (90 km to about 350 km) for a latitude range within South Africa. NNs are used to predict the parameters needed to construct an electron density profile for the given inputs. These parameters include the coefficients of a Chebyshev polynomial. The inputs to this NN based model are geographical latitude and longitude, year, day number, and hour. The year input may be substituted for a measure of solar activity and a measure of magnetic activity. From these given inputs the NN input space is determined and the NNs are interrogated for the parameters required to construct the profile that corresponds to the given inputs. A powerful feature of the SABIM model includes its ability to predict the probability of existence of an F1 layer and apply corrective measures to ensure a realistic result.

Recently, another NN based model called IMAZ (Ionospheric Model for the Auroral Zone) was developed in a joint South African-Austrian effort to provide a reliable prediction tool for the electron density profile at the altitudes below 150 km and at high latitudes. A combination of data obtained from the European Incoherent Scatter Radar (EISCAT) and measurements from rocket bourne wave propagation experiments provided enough high latitude data to cover one solar cycle. The inputs to this model are local magnetic time, total absorption, local magnetic activity, solar zenith angle, and the F10.7 cm solar flux value. The pressure surface, which combines the effects of the seasonal variation (day number) and the altitude, is also included as an input parameter. The output is the electron density at the given input pressure (i.e. altitude). The research for the IMAZ model is being undertaken in collaboration with the Graz University of Technology in Austria.

Other modelling projects include the NN based global model for the peak electron density parameters as well as an investigation into the modelling of the F1 layer. Our aim is to provide continuous good quality bottomside ionospheric data as well as significant contributions to the field of ionospheric modelling within the Southern Hemisphere. This group is a member of the International Reference Ionosphere (IRI) working group, a group of international scientists who work together to continually update and improve the commonly used global ionospheric model. The ionospheric modelling efforts will continue under the umbrella of the HMO.