Meteorologists complain about how difficult it is to actually predict the weather (so lay off already!), but astronomers will tell you that's peanuts compared to space weather. Earth is a closed system with cycles that are fairly predictable. Space is, well, space—mysterious and immeasurably vast.
But that doesn't stop space weather forecasters from trying. On Tuesday, NASA released this visualization of space weather from the first half of 2015, a stab at guessing what conditions might’ve looked like just as New Horizons swept by Pluto.
Weather, in this case, isn’t partly sunny skies or torrential downpours, even if the visualization sort of looks like a hurricane on acid. Instead, the viz is a two-dimensional slice of the solar system that illustrates the plasma that shreds off the sun and wafts its way to the edges of the solar system. Red represents temperature (the brighter it is, the hotter), green means density, and the blue areas are strong shock waves moving through the plasma, says Tom Bridgman, the programmer at NASA’s Scientific Visualization Studio who created the video. Plus, color combinations show areas with multiple traits: Those tinges of purple, for example, are low-density hot shocks.
The sun causes most space weather, at least as far as Earth is concerned. As a big fiery spinning ball of gas, the sun is constantly flinging parts of itself into space—energetic particles, plasma, solar wind and flares. All of these things constitute space weather, says Robert Steenburgh, a scientist at NOAA’s Space Weather Prediction Center. He uses a model called Enlil, which also provided the data for NASA’s visualization, to track these emanations, so space scientists know when radio blackouts will knock out their satellites.
NOAA and NASA scientists use Enlil mostly to predict how the weather will affect things on Earth, so its reach extends just past Mars. Beyond that, in the outer solar system, scientists don’t really know what weather looks like. “We don’t have data to constrain our models,” says Peter Macneice, a researcher at NASA’s Community Coordinated Modeling Center.
New Horizons, then, is a rare chance to collect data from out there. To support the mission, Macneice asked one of the developers of Enlil to extend the model out all the way to Pluto, just to see what the weather might be like there. So this visualization is a hypothesis of how the physics works, with big questions about whether it’s at all like the areas closer to the sun. One question, for instance, is how solar wind will interact with the hydrogen particles that rush in at the outskirts of the solar system.
Data from New Horizons would help. Six other groups posted their own models’ outputs, Macneice says, each showing wildly different results. Some of them use different physics, or emphasize certain factors—Enlil, unlike the others, takes into account coronal mass ejections (those large blobs of plasma), though it’s unclear how much of an effect they have in the solar system’s outer reaches. Macneice hopes that once New Horizons returns its weather data (after, of course, all the pretty close-ups of Pluto arrive), the modelers will be able to check their results, see which model did best, and recalibrate. And that will, in turn, give scientists a lot more information about how far-out space weather actually works.