Monday, November 24, 2008

Coronal holes

Coronal holes are variable solar features that can previous for weeks to months. They are big, dark areas when the Sun is viewed in x-ray wavelengths, sometimes as large as a district of the Sun’s surface. These holes are entrenched in large cells of unipolar magnetic fields on the Sun’s surface; their field lines make bigger far out into the solar system. These open field lines allow an incessant outflow of high-speed solar wind. Coronal holes have a long-term cycle, but the cycle doesn’t correspond precisely to the sunspot cycle; the holes tend to be most many in the years following sunspot maximum. At some stages of the solar cycle, these holes are incessantly visible at the solar north and south poles.

Tuesday, November 11, 2008

Longleaf pine (Pinus palustris) state tree of ALABAMA, NORTH CAROLINA

This pine is a tall, stately native of the southern United States coastal plain, from southeast Texas to southern Virginia. It is one of several pines which characterize the southern pine savannahs. Longleaf pine thrives in areas with long, hot summer conditions and poor acidic soils that are low in organic matter. Like most savannah species, longleaf pine depends on fire to maintain its habitat. Its seeds germinate best on land recently burned. It is a slow-growing tree that may live 200 to 300 years. This pine produces valuable lumber and is also used to produce turpentine, rosin, and tar. The wood is used for posts, structural beams, and flooring. In colonial times, large areas of longleaf pine were cut down for use in shipbuilding. Logging and conversion of the land for other uses has eliminated 97 percent of the longleaf pine forests that existed in pre-colonial times. Old hollow trees are a favorite home for the rare red-cockaded woodpecker. Alabama’s state tree was listed as the “Southern pine” in 1949. But many pines are native to the South, and this name was not specific to a species. It was not until 1997 that Pinus palustris was officially designated as Alabama’s state tree.