A new paper has found that the impact of space weather events, such as solar storms, could be underestimated under current measurements.
“Regression to the mean can explain saturation of geomagnetic storms” reports on a study led by Dr Nithin Sivadas of NASA’s Goddard Space Flight Center and co-authored by Dr Maria Walach from Lancaster University.
Published in Nature, the team analysed over a million solar wind measurements taken by Earth-orbiting NASA spacecraft to examine a potential relationship between the strength of the solar wind and the currents in the upper atmosphere.
Space weather refers to magnetic disturbances in the atmosphere
Fluctuating electric fields in Earth’s magnetic field and upper atmosphere can affect technologies in orbit and on the surface.
For example, extreme geomagnetic storms which disturb the plasma and magnetic field around our planet have been observed disrupting global satellite communications, power outages and radiation exposure to astronauts and even pilots.
Dr Walach said: “Our planet’s magnetic field does a really great job of protecting us against many space weather effects and so they often just show up as glitches or beautiful aurora. There are however extreme cases, where satellites unexpectedly fall back to Earth, or we lose communication and GPS signals.”
Scientists previously believed there was an upper limit to space weather’s impact
Electric currents in the Earth’s upper atmosphere are commonly thought to reach an upper limit with increasing solar wind strength.
Solar wind is a continuous stream of hot gases flowing from the Sun, which grows during solar eruptions. Electric currents in the Earth’s upper atmosphere have been observed to increase in response, but level off after a certain point.
However, the researchers suggest that this apparent limit is in fact due to uncertainties in the solar wind measurements, as the averages obscure the true value.
Most solar wind measurements during extreme events are taken by spacecraft at Lagrange point one, which is a million miles closer to our Sun than Earth is. Solar winds that make it to Earth are likely weaker due to regression to the mean effect, and averaging data from several events will repeat the false assumption that strong solar winds do not produce equally strong currents.
Examining over a million solar wind measurements taken by closer, Earth-orbiting spacecraft instead showed a direct relationship between the strength of the solar wind and the currents in the upper atmosphere.
This implies that there is no upper limit to the responsive electric currents, and as such, damage to technology could increase as well.
The limit does not exist
Dr Walach said: “If there is no upper limit to our planet’s response to the solar wind, modelling for extreme cases needs to take this into account and we should be vigilant of space weather effects. Fortunately, these very extreme cases are rare, but this also means we have limited data to work with and only time will tell what happens at the very extreme one-in-a-thousand-year kind of event.”
The lead author Dr Sivadas said: “We usually assume the truth may be around its measurement. But probability theory says it leans one way. That’s why space weather risks appear underestimated.”
