Geomagnetic storm shows need for space weather forecasts

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Northern lights
Luke Stackpoole/ Unspalsh

One of the largest geomagnetic storms in several decades has caused a spectacular light show in skies around the world and highlighted the importance of forecasts of potentially disruptive space weather events - one of the agenda items on WMO forthcoming Executive Council.

From 10-13 May, aurorae (typically seen at the polar areas) could be seen at unusually low latitudes. Spectacular sightings of aurorae borealis (the northern hemisphere) were observed from e.g. Florida, Italy and Spain and aurorae australis (the southern hemisphere) were reported as far north as Queensland in Australia.

This was the result of an extreme (the highest category) geomagnetic storm from a series of coronal mass ejections (CME's) - clouds of plasma material that are expelled from the Sun with high velocity into the interplanetary space. These plasma clouds carry magnetic field which interacts with the Earth's magnetic field when it finds our planet on its path through interplanetary space.

While aurorae are a delightful spectacle, geomagnetic storms also have potentially disrupting impacts such as the stress they can impose on the power grid due to induced currents in power lines, and possible impacts on communication and satellite operations.

The latest geomagnetic storm followed earlier elevated solar activity. So called active regions, concentrations of magnetic flux on the solar surface, have over the past week released several top-category X class flares, bursts of electromagnetic wave emission. These flares impact the Earths ionosphere causing (high frequency) radio blackouts on the sunlit side of the Earth, and they can also result in perturbations or interruptions of satellite navigation services.

"Such solar events happen regularly, with their occurrence rate following an eleven year cycle associated with the inversion of the overall Solar magnetic field each eleven years," says Jesse Andries, scientific officer with WMO's Space Programme. "We are currently nearing the maximum of the present cycle with Solar events occurring most frequently. While Solar events appear regularly, this recent geomagnetic storm is certainly one of the largest in several decades," he says.

Fortunately, space weather monitoring and prediction is more and more becoming an operational practice just as terrestrial weather is. The latest event was accurately forecast.

Space weather forecasters around the world monitor the sun closely. They report each day on the evolution of active regions on the solar surface and they estimate the probability for large flares to occur.

They furthermore record the properties of the onset of coronal mass ejections which they feed to models which then allow them to estimate the expected time of arrival at Earth. Based on these analyses, critical sectors and the general public are notified in advance of upcoming events, so they can take protective measures, such as deviating flight routes away from the poles.

WMO has been making efforts to integrate Space Weather within its activities for over a decade and has embraced it as a related environmental service in its Strategic Plan.

The WMO Executive Council meeting in June is due to adopt a new Four-year Plan for WMO Activities related to Space Weather (2024-2027). This was recently approved by the WMO Commission for Observation, Infrastructure and Information systems (INFCOM).

The plan addresses the three main pillars of the WMO Infrastructure: observing infrastructure, modelling and prediction, and data exchange. Furthermore, it seeks to advance the capabilities of WMO Members to provide valuable services to various economic sectors that are prone to threats from Solar eruptions and consequent Space Weather phenomena.

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