May 16, 2024

On Friday night 10 May and Saturday Morning 11 May, a historic geomagnetic storm impacted the Earth and caused a very rare occurrence of Aurora Australis or Southern lights, which were visible over South Africa. Storm conditions reached G5 / Extreme conditions.

This is the first time since 2003 that the Earth experienced G5 storm levels and researchers expect solar activity to increase over the next year as we move towards solar maximum in 2025. This document intends to describe the solar conditions that built-up to the geomagnetic event and the response from the South African National Space Agency’s Space Weather Centre.

Activity on the Sun

In early May 2024 two large sunspots appeared on the visible surface of the Sun, referred to as AR3663 and AR3664 (AR – Active Region). AR3664 is roughly 16 times the size of Earth and responsible for the geomagnetic storms of 10 and 11 May. These sunspots were the origin of 41 C-class flares, 66 M-class and 9 X-class solar flares between 6 May and 12 May. The African region experienced interruptions in high frequency (HF) communications due to X-class and M-class flares on Wednesday 8 and Thursday 9 May. Five categories — A, B, C, M and X — are used to rank solar flares based on their intensity. A- and B-class are the weakest/normal background flux, while X-class are the most energetic. The impacts of solar flares are immediate due to the flare traveling at the speed of light and reaching Earth within eight minutes. Solar flares cause absorption of HF radio waves in the upper atmosphere and impact on defence, policing and search & rescue operations, which rely on HF radio communications. The SANSA Space Weather Centre issued warnings at the occurrence of the flares that impacted communications over the African region during daytime. These warnings are distributed to clients.

SANSA issues a daily space weather bulletin that is published on the SANSA Space Weather website. To sign up and receive the SANSA space weather bulletin via email or sms, click here. 

SANSA has developed a HF Radio frequency prediction tool called IOCAP to assist these industries to mitigate the risks of space weather to operational communications.

Coronal mass ejections (CMEs)

Multiple coronal mass ejections or CMEs, associated with X-Class and M-Class Solar flares on 8 May from AR3664 were observed and the SANSA forecasted that it would reach Earth in the late hours of Friday 10 May and into Saturday 11 May. The geomagnetic storm scale indicates the severity of geomagnetic storms. It is denoted by a G followed by a number from 1 to 5, with 1 being a minor storm event, and 5 being an extreme storm event.  A G1 to G3 geomagnetic storm with a chance of a G4 storm was forecasted and a press release was issued on Friday afternoon 10 May. The space weather forecasters anticipated that the geomagnetic conditions would reach a G4 storm level on Saturday 11 May.

The first impact of the CMEs was observed at about 20:00 local time and geomagnetic conditions reached a G4/severe storm level. Hermanus local K-index was 6 (moderate). Other CME impacts were observed at around 23:20 local time and SANSA sent out a warning of a G5/Extreme geomagnetic storm that was in progress at the time. The global Kp-index reached 9 and the Hermanus K-index was at 8. At 07:45 on Saturday morning 11 May, SANSA issued its daily space weather bulletin and reported a G5/Extreme storm was in progress. More G5/Extreme to G4/Severe storm warnings were issued by the Space Weather Centre throughout the day on Saturday, 11 May.

SANSA issued a second press release at 11:42 on Saturday 11 May 2024.

The CMEs continued to impact the Earth throughout Saturday and into Sunday, creating G5/Extreme geomagnetic conditions, with the two sunspot areas continually launching solar flares at M and X-Class levels.

Aurora Australis

The Aurora Borealis (Northern Lights) and the Aurora Australis (Southern Lights) are a consequence of geomagnetic storms. These colourful displays are usually restricted to the polar regions; however, this solar storm created a spectacular  Aurora visible even from South Africa. There were several reports of Aurora Australis being visible over the Southern tip of Africa. Reports of Southern Lights sightings were reported from Gansbaai in the Western Cape, Kuruman in the Northern Cape and Namibia, among others.

Auroras appearing at low latitudes are very rare and the last time this occurred in South Africa was in1989, where auroras were visible from Durban. At low latitudes, the aurora tends to be diffused and unstructured, with a red colour indicating atomic oxygen emissions at an altitude of around 200-300 km. This means an observer can see the aurora over 1 000 km away before the curvature of the Earth blocks the line of sight. The best way to view auroras are in a dark location with no artificial lightning and no cloud cover for several minutes, then look towards the pole, southward from South Africa.


The researchers at SANSA will be conducting investigations with their partners and stakeholders to ascertain the impact of the G5 geomagnetic storm and what steps stakeholders can take to further strengthen risk mitigation strategies.

After any significant storm, it is important to verify the impacts: which technological systems have been affected and to what degree. Since the impacts from space weather vary regionally, it is also critical for SANSA, as the host of the regional warning centre for Africa, to learn how the African continent experienced this event and what we can learn from it. Stakeholders can get involved by reporting any technological disruptions experienced during the geomagnetic storm. Examples can include navigation and communication applications.

For the African region SANSA has confirmed High frequency radio blackouts throughout last week and the weekend. High frequency radio communications is widely used by the defence sector, policing and search & rescue sectors.

One of the confirmed impacts of the storm is from SpaceX who announced over the weekend that there was a degradation in their Starlink satellite internet service due to the solar storms. Read more here. Starlink is not licenced in South Africa, but many African countries rely on this service for internet connectivity and would have been affected by this storm.

Starlink previously lost several satellites when it launched its payload during a space weather event.

SANSA takes note of reports of precision agriculture being impacted during peak planting season in USA due to impact on satellite navigation constellations. Precision agriculture is not yet as widely accessible in South Africa, but as South Africa’s Agriculture sector transitions to precision agriculture, this is a risk to be aware of.

There are also reports of a major internet outage due to the East African subsea cable failure. This will be investigated to determine if this failure is due to the impact of the weekend’s solar storm. Although Fibre Optic cables are not vulnerable to space weather, evidence has shown an in increase in the failure rate of Internet routing equipment during past geomagnetic storms. 


This was the first G5/Extreme geomagnetic storm since the launch of the 24/7 operational Space Weather Centre in November 2022 and it provides an opportunity for SANSA to investigate the impact of a G5/extreme geomagnetic storm on the regional technological systems, thereby adding to the knowledge and expertise of country and contributing to a more resilient system. As can be seen from this debrief, much of the storm impact was felt during the night and would have limited the impact of the storm on certain technological systems that are predominantly used during daytime hours. However, stakeholders are urged to share the technological impacts experienced during this solar storm.

SANSA welcomes stakeholder engagement on space weather related topics, concerns and questions. Please contact us to make an appointment.

Categories: News