Solar Active Region Spotter

What's the corona?

The corona is the Sun's atmosphere. Like the rest of the Sun, it’s composed of gas so hot that some of the electrons have escaped from the atoms, making a hot, charged mess of particles a plasma. The intricate structures and the light and dark regions that are visible in AIA imagery are created by two factors: the magnetic field and coronal heating. Since the plasma is made up of charged particles, they the magnetic field lines, and then these loops of plasma are heated and cooled by the (still unknown) mechanism of heating.

For more definitions of heliophysics terms, see the list of terms on our Research page.

What's an active region?

Active regions are large knots of the Sun's magnetic field which bubble up through the surface and into the corona, appearing in magnetograms as strong bipolar areas and in extreme ultraviolet (EUV) imagery as clusters of bright loops.

Why are active regions important?

These regions are sources of very strong magnetic fields, which grow and shrink and can interact with each other or other nearby features. When that happens, solar flares or prominence eruptions can occur, both of which are not only fascinating but can spawn coronal mass ejections (CMEs). When directed at Earth, CMEs can trigger the aurora or cause detrimental electromagnetic effects on spacecraft and the power grid.

What are the NOAA numbers?

NOAA numbers and tracks active regions as they appear on the Sun. Their numbering convention works sequentially, so an active region that rotates into view on the Sun is not treated any differently from an active region that begins emerging while facing Earth. This becomes problematic when researchers want to follow an active region across multiple rotations. This project is a way to link NOAA numbers that actually belong to the same active region!

What are the grayscale images?

These are called magnetograms; they are very precise measurements of light coming from the Sun to determine the magnetic field direction along the line of sight to the observer. This is measured using a fascinating phenomenon of light, called the Zeeman effect. Energetic atoms emit light at very specific wavelengths. If that light passes through a magnetic field, the light will get split into two very slightly different groups; the "distance" between the two groups (how strongly they're split) tells you how strong the field was that did the splitting! Since active regions are really big knots of strong magnetic field, it's important to look at their magnetic "footprint" in order to study them.

What are the color images?

These are false-color extreme ultraviolet (EUV) data, with each color (red-green-blue) associated with one of the data channels from the Solar Dynamics Observatory. Each channel is sensitive to plasma from a different temperature range; we have selected the channels that best highlight the loops and structure of ARs.