There was a reassuring idea in space-weather research that Earth’s response to a solar storm eventually hit a ceiling. Stronger solar wind would still be unpleasant, but electrical currents in the upper atmosphere appeared to level off. A new NASA-led analysis suggests that ceiling may have been an artefact of where we were measuring from.
NASA’s summary of the solar-storm study explains that many solar-wind measurements are taken roughly a million miles closer to the Sun than Earth. By the time that wind reaches our magnetic shield it is often weaker, making the relationship between the original measurement and Earth’s response look as though it saturates.
The researchers instead analysed more than a million measurements from spacecraft much closer to Earth, including MMS and THEMIS. Those data showed atmospheric electrical currents continuing to increase with the strength of the arriving solar wind. That matters because the currents can interfere with satellites, communications, and navigation signals, so a missing upper limit changes how extreme events need to be modelled.
It is not proof that there is literally no physical limit; NASA says more observations of powerful solar wind are needed. I find the measurement lesson just as interesting as the result. Sometimes the comforting boundary is not a property of nature at all. It is a property of where we left the instrument.
