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Welcome to...

Let's begin with some basic information... At some 92,960,000 miles from Earth, our nearest "star" can put on quite a show! One of the best ways that we can learn about the Sun is to observe for ourselves, and when reporting, or reading reports, the terminology can sometimes be intimidating.

You will find below only a small sampling of solar terms and what they mean, but these are ones that you will find the most useful:


photosphere - the visible surface of the sun. a soild shell of gas approximately 250 miles thick with an average temperature of 11,000 degrees farenheit.

limb darkening - the edge of the photosphere. this effect occurs because at the center of the disc we see deeper into the Sun where the temperatures are higher and the gas shines more brightly. at the limb, we are seeing cooler gas at higher elevations, therefore it appears darker.

granules - at magnification, individual cells of gas contained within the photosphere form ~ these are called granules. each granule may last from several minutes up to a half an hour.

granulation - term used to describe the overall pattern of invididual cells observable at the limb.

faculae - large, irregular patches on the photosphere. once again, observable near the limb, faculae appear as "cracks" or "veins" within the granulation pattern.

prominence - a "loop" of hot gas sometimes observable with a standard H-alpha filter, but requires a narrow band H/al to see filamentation.

flare - a brilliant explosion of pent-up magnetic energy and radiation. narrow band filters are capable of revealing them, but only "white light" flares can be detected in a standard filter.

sunspots - a dark, highly magnetic "patch" on the solar surface where the mean temperatures are about 3,600 degees cooler. here is where the sun's magnetic field has emerged through the photosphere and stopped the rising energy from reaching the surface.

umbra - the darkest, coolest portion of a visible sunspot. these black areas vary greatly in size, shape, and magnetic field polarization.

penumbra - a striated, lighter colored halo surrounding the central umbra. also varies greatl in size and shape.

dispersion field - a term used to describe the umbra/penumbra region of a sunspot group.

plage - a visible perimeter that usually accompanies a sunspot group.

sunspot area - the area of a sunspot measured in millionths of the Sun's visible hemisphere.

sunspot groups - sunspots usually appear in groups. normally it is fairly easy to count the number of groups as they are spread out across the disk and in both hemispheres, but difficulties can occur when sunspots appear close together, so often it is wise to check SOHO information as to their given numerical designation.

the "Wilson Effect" - term coined by Scottish solar astronomer, Alexander Wilson to described the indented, dimpled appearance of highly magnitized sunspots when seen near the solar limb.


OK... Now we have some of the "basic" terminology down, let's talk about what we can see!

Even using standard solar projection techniques, it is very easy to follow the Sun's activity. Umbral and penumbral regions show quite clearly, and solar rotation and the number of spots can be followed quite easily!

By using the average solar filter, the Sun comes alive!! Limb darkening, granulation, faculae, sunpots in incredible detail and the "Wilson Effect" are all readily apparent. After having observed the solar surface for four years, I am continually delighted by the ever-changing face of our nearest star! There have been times when I have seen solar prominences, and white flares. The white flares are simply incredible... For they look as if a great chunk of the Sun flings itself into space!

Practice at solar observance is very rewarding. By combining "at the scope" experience with data readily available from the Solar and Heliospheric Observatory, it's not difficult to learn to predict areas where activity may occur... And now we're getting into a whole new ballgame!

Shall we carry on? Then let's move to our next lesson at:

Solar Observing: 202

--the astronomer