Tracking Solar Flares Space Weather Monitors The Ionosphere Activity Resources Glossary

Tracking your Flare's Source (Active Region) to the Farside of the Sun

Learning the history of your flare’s active region

You can trace the history of your active region. The Sun rotates, as does the Earth. It takes about 27 days for the equator of the Sun to rotate around (other latitudes rotate at different rates). Often, the active region that caused your flare started out on the backside of the Sun and rotated into view.

You should have an image that looks something like this:
Image of the Sun, including side facing Earth and side away from Earth

What you see is an image of the Sun showing both the side facing Earth ("Earthside") and the side away from Earth ("Farside"). The dark blotches indicates a sunspot, or active region on the Sun!

If this map confuses you, here's an equivalent picture of the Earth. Click on the image to watch a movie of how day and night change on the Earth. The farside images work the same way, although the back side of the Sun is not dark like the night side of the Earth!

Mercatur projection of Earth showing day and night
Click to see video

Earth image courtesy US Navy. Video and farside images courtesy of Philip Scherrer, Stanford University.

You should see the active region that produced your flare as a dark blob on the "Earthside" part of the image (but it won't be numbered, so you'll have to compare it with the image you got previously). Go back to the list of days you started with, e.g. 201607. Then, click on the day before your flare, and then on one of the images. Your flare's dark blob should have moved a bit to the left of where you saw it before!

Continue to go "back in time" to follow that dark blob to see when it emerged onto the front side of the Sun by clicking on different images to work your way back in time until you find the region just starting to appear. In our example, it appears that the active region could be seen on the farside as late as July 8, 2016 .

Image of the Sun, including side facing Earth and side away from Earth

How far back in time can you trace your active region? If you find your Active Region appearing in a farside image, write down the date of that image on your Flare Report Form. If you can't find the region appearing, don't worry. Sometimes the active regions form on the front disc of the Sun.