Solar Phenomena


                Solar activity is when transient phenomena occur in the sun .There are many types of solar phenomena that occur in the photosphere, chromosphere, and the corona. One way to quantify solar activity is called F10.7 flux. It measures radio emission from the chromosphere and corona of the sun that are at a wavelength of 10.7cm.

Granules and Supergranules

                Granules are small scale cellular regions, 400km -1000km (250 mi-620 mi), that cover the photosphere. They are the convection regions of the hot plasma that rise to the top of the convection region for about 5-20min. Once they cool, the edges turn dark and the plasma sinks back into the convective region.  Granules are capable of producing a sonic boon and generating waves on the surface of the sun.  Supergranules are simply very large granules on the scale of 35,000 km (21750mi).

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Spicules are believed to be created by sound waves on the sun and are streams of hot plasma that are roughly 50 km in diameter and travel at a speed of up to 22 km/s. Spicules can last several minutes and extend 1,000-10,000 km above the photosphere into the chromosphere.  They array themselves into networks in the chromosphere of supergranules.

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Faculae are bright structures on the suns photosphere that are hotter than their surroundings. They often occur before sunspots and can remain in place for several months after the sunspots disappear. Although sunspots are dependent on faculae, faculae do not necessarily mean a sunspot will appear. Faculae are associated with areas of higher magnetic fields but these fields are not as strong as those associated with sunspots.  

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Sunspots are dark spots on the suns photosphere that are much cooler than there surroundings. They occur in regions of the sun where strong magnetic fields are present. Sunspots appear in pairs with opposite magnetic polarity. [1] The sunspot cycle is composed of the variations in the quantity, size, relative position, and polarity of the sunspots.  It is interesting to note that the magnetic cycle is about 22 years so the maximum number of sunspots occurs every 11 years. Reliable observations of the number of sunspots have been available since 1749.

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Plages occur in the chromosphere and are bright areas surrounding sunspots. Although plages appear with sunspots they can be seen after the sunspot disappears.

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Prominences and Filaments

Prominences are loops of cooler and denser plasma that extend from the photosphere to the corona and remaining for weeks to sometimes months. They are suspended by localized magnetic fields and eventually become unstable and erupt. Depending on the angle a prominence is being viewed at it may appear to be a dark line on the surface of the sun and will then occasionally be called a filament.


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Flares are sudden and intense eruptions in the corona that sometimes accompany sunspots. [1] Flares typically last 1-2 hours and emit particles and broad spectrum radiation that can reach Earth in a few hours to several days. In the worst case the particles and radiation will cause disruptions in radio signals and power transmission. Flares can reach temperatures of 10,000,000-50,000,000 K (18,000,000°F- 90,000,000°F).

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Coronal Mass Ejections (CME)

Coronal Mass Ejections (CME’s) are when large amounts of plasma with a structured magnetic field are ejected from the sun. They are often but not always associated with solar flares. It is currently believed that effects of solar activity on the solar system is caused by CME’s rather that solar flares.

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