Atlas_GLossary

A dark irregular elongated feature seen against the solar disk-cool gas column supported by magnetic field -especially visible in H-alpha. These are good markers of field transition from one magnetic polarity to another.

A highly concentrated explosive release of energy and consequent enhancement of brightness in the solar atmosphere as seen throughout the electromagnetic spectrum. Energies of the order of 10³³ ergs (10²⁶ W) can be released in large flares. The source of this energy is the magnetic field in active region.

One of the outermost layers of the Sun; it is a gaseous shell having a temperature of around 5780K. As the layers above it are highly transparent in visible light, the photosphere is the surface which we actually observe.

Mass of glowing gases above the Sun's surface. A filament which appears dark against the disk appears bright against the dark sky. These occur only in the regions of horizontal magnetic field supporting them against solar gravity and extending to tens of thousands of kilometres above the solar surface.

The forest of hairy spikes embedded in a homogeneous atmosphere of the chromosphere. These thin jets extend upto 10,000 km in the corona.

Active Region :	A localized region comprising of sunspots, plage, filaments and organized patterns of fine structures associated with strong magnetic fields.
Chromosphere :	The transparent tenuous layer of gas in the Sun's atmosphere lying just above the reversing layer and extending to about 3000-5000 km above the photosphere. It is a thermal buffer zone between the low temperature of the top of the photosphere (4400 K) and the high temperature of the corona (1 or 2 x 10⁶ K). The chromosphere can be seen only by blocking the bright photosphere as in an eclipse, or observing in special wavelengths where photosphere does not emit and the corona is too feeble.
Corona :	The outer, more rarefied high temperature atmosphere above the chromosphere extending to several solar radii. This is essentially a high temperature plasma in which immersed are the planets. The intensity of the corona is so weak that, it can be photographed from space in visible light only during a total solar eclipse. However, it can be photographed in EUV and X-ray ranges since only hot coronal gases can emit radiations at these wavelengths.
Filament :	A dark irregular elongated feature seen against the solar disk-cool gas column supported by magnetic field -especially visible in H-alpha. These are good markers of field transition from one magnetic polarity to another.
H-alpha (H-α ) :	6563 A° wavelength emission/absorption line of hydrogen atoms (The Balmer line produced by the transition from n=3 to n=2 level and vice-versa). The chromosphere is no more transparent when seen at this wavelength.
Flare :	A highly concentrated explosive release of energy and consequent enhancement of brightness in the solar atmosphere as seen throughout the electromagnetic spectrum. Energies of the order of 10³³ ergs (10²⁶ W) can be released in large flares. The source of this energy is the magnetic field in active region.
Limb :	The edge of the visible disk.
Photosphere :	One of the outermost layers of the Sun; it is a gaseous shell having a temperature of around 5780K. As the layers above it are highly transparent in visible light, the photosphere is the surface which we actually observe.
Plage :	Regions of enhanced brightness in solar chromosphere (French: Plage-Beach). Plages are associated with active regions.
Prominence :	Mass of glowing gases above the Sun's surface. A filament which appears dark against the disk appears bright against the dark sky. These occur only in the regions of horizontal magnetic field supporting them against solar gravity and extending to tens of thousands of kilometres above the solar surface.
Reversing Layer :	The lower part of the Sun's atmosphere, lying immediately above the photosphere, in which most of the absorption lines originate.
Spicules :	The forest of hairy spikes embedded in a homogeneous atmosphere of the chromosphere. These thin jets extend upto 10,000 km in the corona.
Sunspot :	A dark area in the photosphere of the Sun caused by lowered surface temperature. These are regions of intense magnetic fields. The sizes and numbers of the sunspots vary in 11 year sunspot cycle.