New Person Question: Difference Images

[ThisIsJohnnyT]

Long time lurker, first time posting. I love the sun and regularly look at and post about solar activity on my various social media accounts. Primarily I work with SDO AIA and HMI image data. But over the last few months, I have become really interested in the science of solar activity and how that data translates in what we see picture wise. One thing I notice when looking around is the "difference" channels (such as the black and white LASCO images). Can someone explain to me what these are designed to show? My initial thinking was that it was similar to the HMI Magnetogram images (white is earth facing, black is sun facing) but I'm obviously incorrect on that. I would like to learn more about what this is intended to showcase.

 

Thank you!

[Sam Warfel]

Welcome to (posting on) the forums! Glad to have you!  I think the “difference” here means when something changes fast on the sun, it’s “different” than the previous imagery, and so it shows up as darker black and white. For example, a strong flare would be easy to spot as it would be black/white instead of gray. 
This imagery is useful for spotting some of the fainter effects that are hard to see in full color, like the “shockwaves” or “solar tsunamis”, that can race across the solar disk after a strong flare, and are a good indicator of eruptiveness. This imagery helps us spot those. 

On coronagraphs like LASCO C2 and C3, the difference imagery shows CMEs very well, making them easier to spot and analyze than in the normal imagery. 

Edited February 25, 2023 by Sam Warfel

[ThisIsJohnnyT]

11 minutes ago, Sam Warfel said:

Welcome to (posting on) the forums! Glad to have you!  I think the “difference” here means when something changes fast on the sun, it’s “different” than the previous imagery, and so it shows up as darker black and white. For example, a strong flare would be easy to spot as it would be black/white instead of gray. 
This imagery is useful for spotting some of the fainter effects that are hard to see in full color, like the “shockwaves” or “solar tsunamis”, that can race across the solar disk after a strong flare, and are a good indicator of eruptiveness. This imagery helps us spot those. 

On coronagraphs like LASCO C2 and C3, the difference imagery shows CMEs very well, making them easier to spot and analyze than in the normal imagery. 

Thank you! As a photographer, it's hard for me to see the science first before the image. But the word "texture" comes to mind with the differences, especially when looking at LASCO or AIA channels. I combined a video of both the normal AIA images and then the difference, and layering them gives it a whole new dynamic that you don't see in the plain imagery alone. And you're explanation makes perfect sense on how these become so valuable. Thanks again!