Washington, Oct 19 (PTI): NASA's orbiting Solar Dynamics Observatory has mapped an enormous coronal hole - a gap in the Sun's outer layer and magnetic field - which is the size of 50 Earths and is releasing an extra-fast solar wind in Earth's direction.

The new image was taken on October 10 at an ultraviolet wavelength unseen by the human eye.

The gap in the Sun's magnetic field lets out a stream of particles travelling at up to 800 kilometres per second, kindling a days-long geomagnetic storm upon hitting Earth.

Coronal holes normally form over the Sun's poles and lower latitudes, more often when the Sun is at a less active point in its 11-year cycle.

They are areas within the Sun's outermost layer, called its corona, which are lower-density and cooler - that, plus the weakened magnetic field, lets the plasma and charged particles that make up the corona stream out more easily in a solar wind, 'Space.com' reported.

If aimed toward Earth, it could result in a geomagnetic storm, a phenomenon that can affect power and navigation for satellites orbiting the Earth as well as radio communication.

Another side effect of a geomagnetic storm is enhanced northern lights.

As the coronal hole continues its slow march westward on the Sun's surface (to the right, from Earth's perspective), solar winds will stay strong, National Oceanic and Atmospheric Administration's (NOAA) officials said.