Here comes the Sun

Solar storms: Predicting the threat of a chaotic sun just got better

Coronal mass ejections have the potential to wreck serious havoc on Earth. Solar Stormwatch is on the case

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Everyone talks about the weather, the saying goes, but nobody does anything about it. A group of 7,500 citizen scientists and a team researchers at the University of Reading in England decided to change that, as long as one extends the nature of weather into space — specifically, the Sun.

The first major result of their labor is documented in a study published Friday in the journal AGU Advances.

Coronal mass ejections (CMEs) aren’t part of Earth’s weather — they're a result of powerful solar storms — but they can affect us and our space-dwelling satellites all the same. Ejecting billions of tons of coronal material from the Sun with their own embedded magnetic field, they grow in size as they escape the Sun’s gravity. The largest one can take up almost one-fourth of the space between Earth and the Sun by the time they reach the planet.

Along the way, CMEs can be cosmic blobs of destruction. They can, at their worst, wreak havoc on the electronics within satellites, pose a threat to astronauts with their radiation, and can disrupt power grids on Earth enough to black-out a city. Some scientists believe that a solar storm could have interfered with navigation on the Titanic the night it sank, and a CME trigged the detonations of mines during the Vietnam War.

In 1859, a CME now known as the Carrington Event knocked out telegraph systems all over the planet. Witnesses at the time also described it as “a scene of almost unspeakable beauty” and “the greatest aurora recorded.”

An aurora from a geomagnetic storm that was most likely caused by a coronal mass ejection, observed from the International Space Station.


Unspeakable beauty or no, they pose a risk. That’s why in 2010, the Solar Stormwatch Project was founded.

The University of Reading partnered with data from NASA’s STEREO mission to create Solar Stormwatch, a volunteer project designed to help gather data points on CMEs through simple mouse clicks. At the time, NASA scientists said that “the more people looking at our data, the more discoveries we will make.”

Ten years and 192,224 classifications later, the discoveries are being made. In the paper, the team reports that thanks to information gained about the size and shape of CMEs from volunteers, forecasts were 20 percent more accurate, and uncertainty was reduced by 15 percent.

Not all CMEs hit Earth, which makes understanding their potential trajectory crucial. Dr. Luke Barnard, a space weather researcher at the University of Reading's Department of Meteorology, said that volunteers were able to “present a second stage of observations at a point when the CME was more established, which gave a better idea of its shape and trajectory.”

Better forecasts allow for better management of satellites and space voyages. Knowing a CME of a certain size is coming toward Earth also enables a necessary level of preparedness — like turning off a power grid rather than letting it malfunction.

A coronal mass ejection captured in 2002, showing over a billion tons of matter being sent out into space.


The Solar Spacewatch data has been put to use by running it through a new solar wind model that can ramp up the number of complex simulations it can run by a factor of 10. Where the older model could run 20 simulations at once, the newer model, developed by Reading Professor Mathew Owens can hit 200.

CMEs vary in speed, the slowest ones move around 559,234 MPH (250 kilometers per second) while the quickest can travel at approximately 6,710,809 MPH ( 3000 km/s.) While the slowpokes take weeks to reach Earth, the fastest and most potentially harmful CMES can reach the planet in just 15 to 18 hours.

For over a century, the Carrington Event was the touchstone event of astronomers discussing the potential damage of a CME. But all that changed in 2012, when an equally powerful, if not greater, solar storm barely missed Earth.

The near-miss caused scientists in 2014 to calculate the chances of a Carrington-level event hitting the Earth in the next ten years, and found the risk was at a surprisingly high 12 percent. If such a threat ever does emerge, humanity might have a head start that to the volunteers of Solar Stormwatch.

Abstract: Predicting the arrival of coronal mass ejections (CMEs) is one key objective of space weather forecasting. In operational space weather forecasting, solar wind numerical models are used for this task and ensemble techniques are being increasingly explored as a means to improve these forecasts. Currently, these forecasts are not constrained by the available in situ and remote sensing observations, such as those from the heliospheric imagers (HIs) on the National Aeronautics and Space Administration's (NASA's) STEREO spacecraft, which record white‐light images of solar wind and CMEs. We report case studies of four CMEs and show how HI observations can be used to improve the skill and reduce the uncertainty of ensemble hindcasts of these events. Using a computationally efficient solar wind model, we produce 200‐member ensemble hindcasts, perturbing the modeled CME parameters within uniform distributions about the best estimates. By comparing the trajectory of the modeled CME flanks with HI observations, we compute a weight for each ensemble member. Weighting the ensemble distribution of CME arrival times improves the skill and reduces the hindcast uncertainty of each event. For these four events, the weighted ensembles show a mean reduction in arrival time error of 20.1 ± 4.1%, and a mean reduction in arrival time uncertainty of 15.0 ± 7.2%, relative to the unweighted ensembles. This technique could be applied in operational space weather forecasting, if real‐time HI observations were available. Therefore, as NASA and the European Space Agency are currently planning the next space weather monitoring missions, our proof‐of‐concept study provides some evidence of the potential value of including HIs on these missions.

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