EXCLUSIVE FEATURE: How are experts developing space weather forecasts for geomagnetic storms?

Space weather could cause chaos on Earth unless further developments in forecasting are made, with geomagnetic storms at risk of disrupting radio signals and navigation systems and even causing blackouts. Meteorological Technology International speaks to experts in the space weather sector to find out what is being done to ensure we are well prepared for such events

The first recorded telescope observations of a solar flare, made independently by English astronomers Richard Carrington and Richard Hodgson, occurred on September 1, 1859. A coronal mass ejection (CME) reached Earth 17.6 hours later, causing a powerful geomagnetic storm with aurorae reported as far south as Cuba and Hawaii. Telegraph lines sparked, setting offices ablaze, and ghostly messages continued to travel the wires after power was disconnected due to geomagnetically induced currents.

“There’s evidence the Carrington Event flare was 5 to 10 times larger than anything seen in the Space Age,” says University of Reading postdoctoral research assistant Dr Luke Barnard. “We know a complex-looking sunspot group was seen on the sun’s photosphere and only a series of strong CMEs could plausibly have caused the following geomagnetic storms. Our dependence on technology makes us far more vulnerable to space weather than in 1859.”

Space weather is a catch-all term for phenomena emanating from the sun. Solar flares, (intense, localized spumes of electromagnetic radiation) can reach us in minutes at close to light speed. CMEs (ejections of plasma with complex magnetic fields) travel Earthward on the continuously outflowing solar wind in timescales from hours to days. Both can produce solar energized particles (SEPs), which pose a radiation hazard to astronauts and high-altitude aviators.

‘’We do well at seeing and modeling CMEs to estimate arrival times but intensity is highly uncertain”
– Shawn Dahl, Space Weather Prediction Center, NOAA

“Those external phenomena then interact with Earth’s magnetosphere,” Barnard explains. “Geomagnetic storms occur when CMEs transfer energy to Earth’s magnetic field, where charged particles become trapped. Processes are often coupled, but an extremely energetic CME driving a large SEP event and triggering geomagnetistorms would probably cause the most severe space weather,” he adds.

Observing the sun

Geomagnetic storms heat Earth’s ionosphere, causing radio interference or blackouts, disrupting satellite navigation and increasing atmospheric drag, making satellites likely to deorbit. By increasing the convection of Earth’s magnetic field lines, they induce currents in the ground that could wipe electromagnetically stored data and destroy the transformers on which electricity grids depend. “Our capability to detect solar events is pretty good,” says Juha-Pekka Luntama, head of the European Space Agency (ESA) Space Weather Office. “Ideally, we want about two days’ warning to prepare power grids by balancing or reducing loads – but that forecast capability is where we’re lacking.”

Space weather falls under an ESA Space Safety Program that also addresses planetary defense, space debris and sustainable use of space. ESA’s federated approach networks capabilities across member states. Solar events are first characterized by ESA’s solar weather group; the heliospheric weather group plots solar events’ transit across space then other groups estimate space radiation, ionospheric weather and geomagnetic impacts.

“We have limited operational monitoring capability and often rely on converted science missions to observe the sun,” explains Luntama. “One workhorse is the Solar and Heliospheric Observatory (SOHO), orbiting at the L1 Lagrange point between Earth and the sun. SOHO’s coronagraph observes the sun’s corona and UV imagers observe the solar disk. We may wait hours for data, whereas operational applications require continuous, near-to-real-time information. Like many space-based assets, SOHO is old and we fear losing it,” he adds.

When coronagraph imagery reveals outflowing CMEs, ground-based magnetographs provide observations of the sun’s magnetic field, from which solar wind speeds may be inferred and CME arrival times at Earth thus estimated. Solar flares are forecast probabilistically, with magnetographs and extreme ultraviolet (EUV) imagers used to detect energy building in complicated sunspots.

“Today, we have no means to follow a CME’s propagation after about two hours, when it leaves the field-of-view of coronagraph instruments,” says Luntama. “For 15 hours, we bite our fingernails and run simulations. Vigil [see ESA’s revolutionary Vigil spacecraft, page 10] will improve that by giving us permanent stereoscopic visibility of solar events.”

40% of experts surveyed by the University of Reading expressed doubts about the current accuracy of space weather forecasts

Addressing knowledge gaps

Space weather, like conventional meteorology, must combine observations with simulation. Besides planning missions to improve observations, ESA uses and develops heliophysics models and models of Earth’s magnetosphere and ionosphere to forecast terrestrial impacts. But space weather happens fast – and fundamental knowledge gaps preclude forecasting events in advance of observation.

“Forecasting solar eruptions is the Rosetta stone of space weather,” says Luntama. “Sunspots are magnetic anomalies emerging somewhere deep in the sun. But when and why they erupt, we don’t fully understand. The European Solar Orbiter and US Parker Solar Probe missions may help improve our understanding.”

Launched in 2010, NASA’s Solar Dynamics Observatory (SDO) performs imaging experiments on small temporal and spatial scales and many simultaneous wavelengths, designed to enable understanding and prediction of solar variability.

“We predict CME arrival times quite well,” says Barnard. “But a CME’s magnetic field structure determines how effectively it couples with Earth’s magnetic field to drive geomagnetic storms. Because we have little detail on that, we have limited skill in forecasting intensity.”

NOAA’s Space Weather Prediction Center (SWPC) is in Boulder, Colorado. While many nations have lately established space weather offices to support space operations, SWPC has worked with NASA since the Apollo era. It collaborates closely with the US Air Force and, space weather being a planetary issue, compares forecasts with UK and Australian colleagues and coordinates with China and Russia in providing advice to global aviation.

“We’re the nation’s official source for space weather alerts, watches and warnings,” comments SWPC senior forecaster Shawn Dahl. “Like most meteorological offices, we staff forecast operations 24/7 – except we’re trying to forecast if and how events 93 miles [150km] away will impact Earth,” he continues.

SWPC relies on operational satellites and NASA science missions to inform forecasts. NOAA’s GOES-R series geostationary weather satellites have instruments including a solar ultraviolet imager (SUVI) to observe the sun at different wavelengths, an extreme ultraviolet sensor (EUVS) and an x-ray sensor (XRS), which is useful in monitoring flares. NOAA’s Deep Space Climate Observatory (DSCOVR) monitors solar wind at the L1 point of gravitational equilibrium on the sun-Earth line.

“We also rely on research satellites,” Dahl continues. “NASA’s ACE (Advanced Composition Explorer) also orbits at L1. DSCOVR has problems with elements of the solar wind, so we use ACE to fill those gaps. SOHO provides our only observations of the sun’s corona but that imagery is subject to latency and delays. The good news is that GOES-U will have a compact coronagraph to provide much quicker vigilance and should be operational by fall 2024.”

Data collected a million miles away reaches SWPC’s server room within five minutes. It is combined with observations from sources including Air Force optical and radio telescopes to feed models which are not yet so well developed as those used in meteorology. SWPC three-day forecasts, issued at 00:30 UTC and 12:30 UTC each day, are used to inform satellite, communication, infrastructure and aviation operations.

“We really need a side view of the sun at Lagrange point L5,” says Dahl. “We do well at seeing and modeling CMEs to estimate arrival times but intensity is highly uncertain. We only know if the CME’s magnetic field orientation will connect solidly with Earth’s magnetic field and cause geomagnetic activity when it passes those L1 spacecraft 1,000,000 miles [1,600,000km] out.”

Data assimilation

While the Carrington Event is widely considered a one-in-a-hundred-year worst-case scenario, the possible severity of a one-in-a-thousand-year event is hard to extrapolate from 60 years of reliable observations. A University of Reading study surveyed 144 experts, 52% of whom believe future geomagnetic storms could surpass even Carrington-like magnitudes.

“Space-based observations only started in 1961,” says Barnard. “We have some geomagnetic observations back to the 1880s. Beyond that, we can make informed judgments from our knowledge of physical processes. Recorded observations from cosmogenic isotopes Carbon-14 and Beryllium-10, found in trees and ice cores respectively, show historic spikes most plausibly attributable to an extreme SEP event.”

In the University of Reading study, 40% of experts surveyed lacked confidence in current forecasts, while many saw deploying small-satellite constellations close to the sun as the most promising means to improve them. Barnard underlines the promise of Vigil to provide continuous, threedimensional visibility of CMEs and advance notice of structures forming on the side of the sun rotating round to face us. He expects models to rapidly evolve.

“Data assimilation revolutionized meteorological forecasts and is now being applied to space weather,” says Barnard. “Combining model estimates with observations of a system state could reduce the uncertainties in CME arrival-time forecasts from 12 to 6 hours. Ensemble modeling will allow us to simultaneously run many forecasts, initialized with different conditions reflecting uncertainties in CME or ambient solar wind structures.”

Besides more observations, there may be new types of observation. Barnard himself uses a heliospheric imager, which resembles a baffle camera and observes the solar wind by isolating one part in 1,014 of solar white light. NASA’s PUNCH (Polarimeter to Unify the Corona and Heliosphere) mission, using a polarizing heliospheric imager to record structures transitioning from the corona to the solar wind, may advance our ability to locate Earth-bound CMEs.

Luntama emphasizes a need to formalize the availability of current measurements. “Ground-based instruments that monitor space weather worldwide are based on proposals for academic research, so their future is always uncertain,” he says. “We work with member states to ensure the safety of systems critical to protecting our infrastructure, which should in future be operationalized.”

Space privatization

Demand for space weather information continues evolving, notably through the privatization of space. In February 2022, 40 Starlink satellites deorbited and were lost shortly after launch because a minor geomagnetic storm heating the upper atmosphere caused additional drag. “They weren’t paying attention to space weather,” says Dahl. “Space tourism will soon be a thing, if billionaires’ visions hold true. We can educate private enterprises and support them indirectly with our models and forecasts.”

Dahl and Barnard counsel against alarmism engendered by sensationalist headlines, as space weather poses no direct physical threat at ground level and SWPC provides US citizens with information from a trusted source. Yet Dahl, who liaises with federal emergency planners, acknowledges the unpredictable social consequences of a latter-day Carrington Event.

“If people living off-grid suddenly see the aurora, what do they think?” he asks. “We’re talking no water, heating or power, traffic lights and ports not working, billions lost in commerce. We all love buying frozen items from the grocery store, which these events could inhibit.”

Luntama notes that for two decades, Earth has seen so little space weather that his role has almost seemed boring. But the risks remain real, as does the vulnerability inherent in the technological dependence we have chosen. “We’re overdue a Carrington event,” says Dahl. “In 2023, a CME at Carrington-like speeds on the sun’s far side was strong enough to cross all the magnetic field lines necessary to cause radiation storms on Earth. We haven’t not seen them – we’ve just had some near misses.”

The potential of the Eutelsat OneWeb constellation

Space weather forecasting is inhibited by limited observations, but low- Earth-orbiting satellite constellations promise new means to monitor solar events. Dr Martin Archer, Stephen Hawking Fellow at Imperial College London, is exploring the potential of the Eutelsat OneWeb constellation to capture space weather information.

“Recent years have seen an increase in distributed telecommunications satellites covering the entire globe,” comments Archer. “OneWeb, the second-largest of these megaconstellations, is expected to have 643 satellites in orbit by 2025.”

These will employ anisotropic magnetoresistive (AMR) sensors, which are chip-type magnetometers that determine the satellite’s orientation based on resistivity caused by Earth’s magnetic field. Potentially, these could also detect the magnetic signals emitted from space weather.

“We’ve worked with those sensors for 10 years at Imperial,” says Archer. “We’ve demonstrated that the tech can measure field-aligned currents due to space weather on 10 x 10 x 30cm CubeSats. The next leap is seeing whether we can take similar data from a subsystem of 643 satellites already in orbit.”

A UKRI Future Leaders Fellowship will fund Archer’s work at Imperial College London for seven years. This matters, because ambitious science requires stable funding, and the technical challenges are complex.

“We need to calibrate the sensors to subtract all the contamination caused by currents used to operate the satellite, leaving only the signals from Earth’s magnetic field and space weather,” Archer explains. “If we have enough distributed measurement points, we could use fitting techniques to fill any blanks.”

OneWeb measurements downloaded to ground stations in real time could provide a new and global picture of space weather. “Space weather is a global hazard,” says Archer. “We have only a few space-based observation points. There’s better ground-based coverage but half the ground is water. A global scientific data set may allow better understanding of physical processes to trickle through and improve space weather forecasting.”

ESA’S revolutionary vigil spacecraft

The Lagrange points are points in space where the sun and Earth exert a balanced gravitational influence on small-mass objects. While L1, L2 and L3 occur on a line transecting the two bodies, L4 and L5 each form the third vertex of an equilateral triangle relative to our planet and star.

In development and scheduled for launch later this decade, ESA’s Vigil spacecraft is destined for orbit at L5, 60° from the sun-Earth line, to provide transformative sideways solar observation capability. “For the first time in history, we will have permanent stereoscopic visibility of solar events,” says ESA’s Juha-Pekka Luntama. “We currently lose sight of CMEs about two hours from onset. But Vigil will allow us to follow the plasma cloud traveling toward Earth, see whether it slows or merges with another plasma cloud, and thereby better predict arrival times and impacts.”

Vigil’s comprehensive payload will include a coronagraph to observe CMEs, a heliospheric imager to follow their propagation toward Earth and a magnetograph to measure the solar disk’s magnetic field and enable models of background solar wind. NASA will provide an extreme UV imaging instrument.

“Typically, L1 missions split the instruments between the L1 satellite, Earth-orbiting satellites and even ground-based observations,” says Luntama. “Because L5 has no planet behind, we have to put all the instruments on the spacecraft.”

Vigil will also provide in-situ measurements of the solar wind and its magnetic field at L5. This will enable forecasting of high-speed solar wind streams hitting Earth and help forewarn satellite operators of conditions conducive to problems like surface charging of satellites.

This article originally appeared in the April 2024 issue of Meteorological Technology International. To view the magazine in full, click here.