The SunThe Sun is a giant thermonuclear furnace with an internal temperature estimated to be 15 million degrees Celsius. Hydrogen nuclei collide at such an extremely high speed they fuse to form helium nuclei generating enormous amounts of heat in the core. The heat works its way to the luminous outer surface called the photosphere. Here temperatures fall to about 6000oC generating a maximum wavelength of emission in the visible end of the electromagnetic spectrum. Sun spots are dark, cooler regions of strong magnetic fields on the photosphere. The number of sun spots vary through an eleven year cycle. Solar flares occur in the region of sun spots, sending energized, charged particles at great speeds toward Earth. Above the photosphere lies the chromosphere and the corona. The chromosphere acts as a boundary between the cooler photosphere and hotter outermost layer the corona. The Solar Wind and AurorasA continuous flow of charged particles (ions and
electrons) is discharged as a solar
wind. At the extremely high temperatures,
violent collisions of gases strip them of electrons acquiring enough
speed to escape the gravitational pull of the sun. When this solar wind
comes close to the Earth they interact with Earth's magnetic field.
When the solar wind strikes the Earth's magnetic field it deforms it
into a tear-drop shaped cavity called the magnetosphere.
Inside the magnetosphere are ionized gases from the solar wind and the
upper most part of the Earth's atmosphere. Figure ER.7 Aurora borealis near
Anchorage, Alaska During periods of high solar activity, the solar wind is more dense, travels faster, and possesses more energy. Reaching the Earth' magnetic field they set off auroral displays by exciting atmospheric gases resulting in the emission of visible light. In the Northern Hemisphere the spectacular light show is the aurora borealis or northern lights. In the Southern Hemisphere they are called the aurora australis, or southern lights. |
