Observing The Sun in Calcium [Ca]

Many amateur astronomers get their first glimpses of our nearest star in white light using relatively inexpensive solar film.

Image by Alan Friedman Description from Observing the sun in Ca II K

The wealth of information about the features seen in this wavelength (photosphere) is widely shared and easily available.

As the cost of exclusive narrowband filters has decreased over the past few years, viewing the sun in the Hydrogen alpha and Ca II K line has become more common.

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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Granules on the Sun’s Surface

Granules on the photosphere of the Sun are caused by convection currents (thermal columns, Bénard cells) of plasma within the Sun’s convective zone. The grainy appearance of the solar photosphere is produced by the tops of these convective cells and is called granulation.

The rising part of the granules is located in the center where the plasma is hotter. The outer edge of the granules is darker due to the cooler descending plasma. In addition to the visible appearance, which would be explained by convective motion, Doppler shift measurements of the light from individual granules provides evidence for the convective nature of the granules.

A typical granule has a diameter on the order of 1,000 kilometers and lasts 8 to 20 minutes before dissipating. At any one time, the Sun’s surface is covered by about 4 million granules. Below the photosphere is a layer of “supergranules" up to 30,000 kilometers in diameter with lifespans of up to 24 hours.

Pages 4–5 of the ‘Ace Combat 3 Electrosphere Portfolio Photosphere’. Introduction here.

Mission statement for General Resource LTD. Part of me cringes a bit at the justification of the text, but mostly I love the tenacity of it – it’s just so cool. The whole spread does well to establish GR’s character – expressionless, rigid, monolithic, mysterious.

On a side note, this is where my blog name comes from. Data Swallow is a General Resources OS used to upload stuff to the Electrosphere, where it is visualised and made accessible to anyone with a connection.