Three Vast 'Holes' Just Appeared on the Sun—and They're Bombarding Earth with Geomagnetic Storms

Three vast "holes" have opened up on the Sun over the past week, according to NASA's Solar Dynamics Observatory (SDO), allowing high-speed solar winds to escape into space and bombard the Earth.

These so-called coronal holes are gaps in the star's outermost atmosphere, which are less dense and cooler than their surroundings. Magnetic field images released by the SDO show huge dark patches on the Sun's surface, indicating their location.

The holes spew out charged particles which can affect animals and electronic systems on Earth, and cause auroras to appear at lower latitudes than normal if they interact with the magnetosphere—the region around our planet dominated by its magnetic field.

"A stream of high-speed solar wind is buffeting Earth's magnetic field, and this is causing G1-class geomagnetic storms around the poles, reported on April 11. "Auroras have been sighted in the USA as far south as the Dakotas. The gaseous material is flowing from a wide hole in the sun's atmosphere—so wide that the stream could influence Earth for another two to three days."

For April 12, the National Oceanic and Atmospheric Administration's (NOAA) Space Weather Prediction Center have issued an alert saying there is a 50 percent chance of a minor G1-class geomagnetic storm.

A G1-class storm is the lowest on the NOAA's space weather scale, but these events still have the potential to cause minor disruption to power grids, satellite operations and migratory animals. But on the plus side, sky watchers in the northern United States, such as northern Montana, Minnesota, Michigan, North Dakota and Maine, will have a higher chance of witnessing an aurora.

For much of this week the sun featured three substantial coronal holes (Apr. 3-6, 2018). Coronal holes appear as large dark areas which are identified with arrows in the still image. Solar Dynamics Observatory, NASA.

Coronal holes can develop at any time and location on the Sun but are more common and persistent during the years around solar minimum (the next one minimum is expected between 2019 and 2020). Solar minimum is the period of least activity in the 11-year cycle of the Sun, when the number of sunspots and solar flares diminishes. These stand in contrast to the solar maximum, during which time hundreds of sunspots may appear.