Approximately nine days from now, a solar wind stream will hit Earth. That's a long-range forecast made possible for the first time by NASA's Stereo-B spacecraft. The stream is flowing from a coronal hole photographed this morning by the spacecraft's extreme ultraviolet telescope:
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In years past, the longest-range forecasts of solar wind streams amounted to six or seven days. Stereo-B has extended the range to eight or nine days. It does this trick by looking over the sun's eastern horizon to find coronal holes before they can be seen from Earth. The orbit of Stereo-B is similar to Earth's, yet it lags 38o behind our planet, giving it an "around-the-bend" view of the sun.

Arctic sky watchers should be alert for auroras at the end of the month. A Halloween storm could be brewing.