NASA has observed a giant plasma cloud colliding with our planet from space, a historic first. What might this mean for space-weather forecasting?
It took three years, but NASA scientists have created a better way to predict space weather.
Take a look at the video below. It depicts an eruption and subsequent coronal mass ejection from the Sun in late 2008. The scene was recorded by STEREO-A, one of two NASA spacecraft orbiting the solar system's life-sustaining star. The CME, a huge cloud of electrically charged particles that can cause power grids and communications systems to glitch, is shown as the white, vaporous mass that moves like a ghost leftward toward Earth.
Never before have scientists been able to observe a CME's 93 million-mile journey from emission to arrival (as far as humans are concerned). The problem was that these things, while brightly visible at the moment they tear away from the sun, dim on their journey to become indistinguishable from the surround space. Says NASA:
By the time a typical CME crosses the orbit of Venus, it is a billion times fainter than the surface of the full Moon, and more than a thousand times fainter than the Milky Way. CMEs that reach Earth are almost as gossamer as vacuum itself and correspondingly transparent.
But in the past few years solar scientists have developed an enhancement technique that brings a wandering CME into focus. The impact on space-weather prediction could be significant: Rather than estimating the arrival of the plasma blob from its speed when leaving the Sun, a strategy that can have a margin of error of 4 hours, spacecraft now observe them in real time. Plus, STEREO-A can sense the density of these sometimes one-and-a-half-trillion-ton space clouds, which will drop clues to how much trouble the CME could cause on Earth.
This technique – NASA doesn't get into details on what it involves – has revealed that a CME doesn't just glide unperturbed through space once it departs the solar body, like an Amtrak Acela on a boring journey to New York. Rather, to continue the metaphor, the "train" encounters all sorts of snow drifts and random trash that've been thrown over the tracks. Explains NASA of the 2008 event:
When the CME first left the sun, it was cavernous, with walls of magnetism encircling a cloud of low-density gas. As the CME crossed the Sun-Earth divide, however, its shape changed. The CME "snow-plowed" through the solar wind, scooping up material to form a towering wall of plasma. By the time the CME reached Earth, its forward wall was sagging inward under the weight of accumulated gas.