A new measurement and modeling tool could give more than 24 hours’ notice of coronal mass ejections that could be harmful to systems on Earth.
New tool could predict powerful solar storms more a day in advance. Image credit: SDO / NASA.
Coronal mass ejections (CMEs), often called solar or space storms, are massive clouds of solar plasma threaded with magnetic field lines that are ejected from the Sun over the course of several hours.
Although the Sun’s corona has been observed during total eclipses of the Sun for thousands of years, the existence of CMEs was unrealized until the space age. The earliest evidence of these events came from observations made in 1971.
CMEs are often associated with solar flares and prominence eruptions but they can also occur in the absence of either of these processes. The frequency of CMEs varies with the sunspot cycle.
CMEs produce disturbances that strike the Earth with sometimes catastrophic results. They can cause problems with GPS technology – used by all kinds of vehicles, from cars to oil tankers to tractors. For example, they can affect the ability of aircraft systems to judge precisely a plane’s distance from the ground for landing, leading to planes being unable to land for up to an hour.
However, not every CME that travels past our planet causes this much disturbance – the power depends on the orientation of magnetic fields within the mass ejection.
Currently, satellites can only tell the orientation of a mass ejection’s magnetic field with any certainty when it is relatively close to the Earth, giving just 30-60 minutes’ notice.
“What we have now is effectively only a 30 to 60 minute heads up of a CME’s configuration before it hits Earth’s magnetosphere. We don’t have a real time method for measuring or modeling this magnetic field more than an hour before a space weather impact,” said Dr Neel Savani of NASA’s Goddard Space Flight Center in Greenbelt, Maryland.
Dr Savani and his colleagues described a new model to measure the magnetic field configuration significantly further ahead of time in a paper published online in the journal Space Weather.
“As we become more entwined with technology, disruption from large space weather events affects our daily lives more and more. Breaking through that 24 hour barrier to prediction is crucial for dealing efficiently with any potential problems before they arise,” Dr Savani said.
The orientations of magnetic fields within CMEs depend on two things: their initial form as they are erupted from the Sun, and their evolution as they travel towards Earth. CMEs originate from two points on the Sun’s surface, forming a croissant-shaped cloud in between that discharges into space.
This cloud is full of twisted magnetic fields that shift as they travel. If one of these magnetic fields meets the Earth’s magnetic field at a certain orientation, the two will connect, ‘opening a door’ that allows material to enter and cause a geomagnetic storm.
Previously, predictions had relied on measuring the initial CME eruption, but were not efficient modeling what happened between this and the cloud’s arrival at Earth.
The new tool takes a closer look at where CMEs originate from on the Sun and makes use of a range of observatories, including NASA’s Solar Terrestrial Relations Observatory (STEREO) and the NASA/ESA Solar and Heliospheric Observatory (SOHO), to track and model the evolution of the cloud.
So far Dr Savani and co-authors tested their method on eight different CME events (between 2010 and 2014) to show that their model’s predictions corresponded with what actually happened.
The initial results show great promise at improving the current forecasting system for large Earth-directed solar storms. If further testing at NASA supports these results, the tool could soon be used by NOAA in the US and the Met Office in the UK for geomagnetic storm predictions.
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N.P. Savani et al. Predicting the magnetic vectors within coronal mass ejections arriving at Earth: 1. Initial architecture. Space Weather, published online June 09, 2015; doi: 10.1002/2015SW001171
