This Atmospheric Imaging Assembly (AIA) Composite image of the Sun was recorded by Solar Dynamics Observatory in the extreme ultraviolet region (211/193/171 Å) on 2014-10-23 at 23:42:59 UTC. It combines three images with different, but similar, temperatures. The colours are assigned differently than in the single images. Here AIA 211 is red, AIA 193 is green, and AIA 171 is blue. Each highlights a different part of the corona of the Sun. The dark blue areas ‒ called coronal holes ‒ are large regions in the corona that are less dense and cooler than surrounding areas. Coronal holes are where the Sun's magnetic field does not loop back down to the surface; it is open into interplanetary space. They are places where very little radiation is emitted, yet are the main source of solar wind particles. The open structure of their magnetic field allows a constant flow of high-density plasma to stream out of the holes.

As shown in this image, a recurrent trans equatorial coronal hole (CH640) was in an Earth facing position on October 19−22.

The geomagnetic field is expected to be quiet to unsettled on October 24−25 due to effects from CH640 and quiet on October 26.

 

 

Credit: SDO(NASA) / AIA consortium