Sun’s North Pole Coronal Hole Equals 50 Earths, Vivifies Arctic Lights

Summary: Imaged Oct. 10 by Solar Dynamics Observatory, the sun's north pole coronal hole equals 50 Earths and vivifies Arctic lights with expanded visibility.

NASA SDO image of coronal hole on Oct. 10, 2015: NASA/SDO, Public Domain, via NASA

On Saturday, Oct. 10, 2015, NASA’s orbiting Solar Dynamics Observatory (SDO) imaged a colossal coronal hole darkening the sun’s north pole.

With the positive polarity coronal hole continuing to progress westward across the sun, Space Weather Prediction Center (SWPC) forecasters at the National Oceanic and Atmospheric Administration (NOAA) issued a G1-Minor watch for increased geomagnetic storming for Wednesday, Oct. 14, through Friday, Oct. 16. The coronal hole’s sprawling size equates to 50 side-by-side Earth equatorial widths (50 x 7,926 miles/12,756 kilometers), or 396,300 miles (637,800 kilometers).

The bronze palette of SDO’s capture of Saturday’s sprawling coronal hole typifies colorization for the image’s wavelength in the extreme ultraviolet light spectrum, which ranges far beyond the narrow light spectrum visible to humans. With information about the sun’s atmosphere and surface conveyed through different wavelengths, the coronal hole’s wavelength, measured at a length of 193 Angstroms, highlights slightly hotter coronal regions.

Not actually a hole, a coronal hole represents a region of the sun’s corona, or outermost layer, where the sun’s magnetic field spews coronal material as high-speed solar wind out into interplanetary space instead of looping back down to the solar surface. Apart from coronal hole regions, solar winds stream away from the surface for dispersion throughout the solar system at typical speeds of 250 miles (400 kilometers) per second. Contrastingly, coronal hole winds attain speeds of nearly 500 miles (800 kilometers) per second.

The collision of accelerated coronal hole winds with the Earth’s magnetic field effects a transfer of energy that creates disturbances in the Earth’s magnetosphere. The geomagnetic storm whipped up by the charged transfer may dramatize auroral displays in the Northern and Southern hemispheres, disrupt high-altitude radio transmissions and satellite communications, and even skewer navigational capabilities of migratory animals.

First spotted in photographs taken during NASA’s Skylab space station orbit of Earth from 1973 to 1979, coronal holes have cooler, less dense atmospheres than their environs because of the rapid flow of coronal material released by their opened magnetic fields. Coronal holes range in shifting shapes across the sun but especially hug solar poles at less active points in the approximately 11-year cycle of solar magnetic activity.

Oct. 14th’s coronal hole takes place in a quiet stretch of solar cycle 24, which began on Jan. 4, 2008. The coronal hole owes its supersizing to formation from three smaller holes responsible for outstanding aurora borealis displays splashing in altitudinous dances of light well south of the Arctic Circle.

The shape-shifting journey of October’s colossal coronal hole westward across the sun may last for weeks or even months. Although safe solar viewing apparatuses are available for some solar events, coronal holes are not directly visible to the human eye. Image capture via the extreme ultraviolet light spectrum serves as the only way to track the coronal hole’s progress.

Or lucky observers within the expanded auroral viewing latitudes occasioned by the plentiful flurry of coronal atoms may take out time to appreciate the coronal hole’s extraordinary, expressive reach.

An earlier coronal hole, also with an estimated size of 50 Earths, spreads over sun's upper left quadrant in image taken by NASA's Solar Dynamics Observatory on June 18, 2013; the hole's blueness, representing light in the 171 Angstrom wavelength, is an area of cool, less dense materials in the sun's atmosphere: NASA/SDO, via NASA

Acknowledgment

My special thanks to talented artists and photographers/concerned organizations who make their fine images available on the internet.

Image credits:

coronal hole image taken by NASA’s Solar Dynamics Observatory in wavelengths of 193 Angstroms on Oct. 10, 2015: NASA/SDO, via NASA @ https://www.nasa.gov/image-feature/goddard/coronal-hole-front-and-center/

An earlier coronal hole, also with an estimated size of 50 Earths, spreads over sun's upper left quadrant in image taken by NASA's Solar Dynamics Observatory on June 18, 2013; the hole's blueness, representing light in the 171 Angstrom wavelength, is an area of cool, less dense materials in the sun's atmosphere: NASA/SDO, via NASA @ https://www.nasa.gov/mission_pages/sunearth/news/gallery/20130618-coronalhole.html#.WYooGVGGO70

For further information:

“Coronal Hole Front and Center.” NASA > Missions > SDO. Oct. 14, 2015.
Available @ https://www.nasa.gov/image-feature/goddard/coronal-hole-front-and-center

“G1 (Minor) Geomagnetic Storms Likely Again from 14-16 Oct 2015.” NOAA Space Weather Prediction Center > Current Space Weather Conditions. Friday, Oct. 16, 2015.
Available @ http://www.swpc.noaa.gov/news/g1-minor-geomagnetic-storms-likely-again-14-16-oct-2015