photosphere

Composite Image of the Sun

The four images of the Sun (Dec. 7, 2011), taken by NASA at almost the same time, showing various wavelengths in various temperatures and layers of the Sun. The first section shows the photosphere that displays the various sunspots on the “surface” of the Sun. Then it transitions into the region between the chromosphere and the corona where, in extreme UV light, the active regions appear lighter. Next is a composite of three different wavelengths showing temperatures up to 2 million degrees C. The last image is an overlay of a science-based estimation of the complex magnetic field lines extending from and connecting the active regions before going back to the sunspot image. Who says the Sun is boring?

Field of Fiery Grass a.k.a. Solar Spicules

Solar activity in the chromosphere takes many forms, the most common feature is the presence of spicules. Spicules are long thin jets of superheated gas, called plasma which appear like the blades of a huge field of fiery grass growing upwards from the photosphere below. On the disc of the Sun, spicules are called chromospheric mottles, there are also horizontal wisps of gas called fibrils, which last about twice as long as spicules.

According to a theory the spicules are caused by sound waves, slight pulsations of the Sun’s visible surface. Seismic waves (similar to those in an earthquake) in the Sun’s interior create giant sound waves called p-modes. The p-modes are normally trapped near the photosphere, but some of the sound waves leak out, developing shock waves that propel matter upward to generate spicules and push them into the corona.

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Credit: NASA/JAXA/GSFC/SVS

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The upper atmosphere of the Sun is dominated by plasma filled magnetic loops (coronal loops) whose temperature and pressure vary over a wide range. The appearance of coronal loops follows the emergence of magnetic flux, which is generated by dynamo processes inside the Sun. Emerging flux regions (EFRs) appear when magnetic flux bundles emerge from the solar interior through the photosphere and into the upper atmosphere (chromosphere and the corona). The characteristic feature of EFR is the -shaped loops (created by the magnetic buoyancy/Parker instability), they appear as developing bipolar sunspots in magnetograms, and as arch filament systems in . EFRs interact with pre-existing magnetic fields in the corona and produce small flares (plasma heating) and collimated plasma jets. The GIFs above show multiple energetic jets in three different wavelengths. The light has been colorized in red, green and blue, corresponding to three coronal temperature regimes ranging from ~0.8Mk to 2MK. 

Image Credit: SDO/U. Aberystwyth