The Sun; Exam

Stars including the sun, transform matter into energy in nuclear reactions. When hydroged nuclei fuse to form helium, a small amount is converted into energy. solar energy is responsible for life processes and weather as well as phenomena on Earth. These and other processes in stars have led to the formation of all the other chemical elements.

1)http://www.exploratorium.edu/sunspots/
2)http://solarscience.msfc.nasa.gov/SunspotCycle.shtml

Sunspots are dark spots (some as large as 50,000 miles) that move across the suns surface expanding and contracting.The ancient Greeks believed that the sun was the chariot of the god Helios, driven across the heavens by four horses. How did the early astronomers manage to look at the sun? One of the methods they figured out was projection. By using a telescope to project a smaller, dimmer image of the sun, they were able to study the sun at their leisure, with no risk to their eyes.

3)http://en.wikipedia.org/wiki/Solar_flare
4)http://hesperia.gsfc.nasa.gov/sftheory/flare.htm

A solar flare is a large explosion in the Sun's atmosphere. When magnetic energy builds up in the solar atmosphere, it is then suddenly released. As the magnetic energy is being released, particles, including electrons, protons, and heavy nuclei, are heated and accelerated in the solar atmosphere. The energy released during a flare is typically on the order of 1027 ergs per second. Large flares can emit up to 1032 ergs of energy. This energy is ten million times greater than the energy released from a volcanic explosion. On the other hand, it is less than one-tenth of the total energy emitted by the Sun every second. The solar wind is a stream of charged particles ejected from the upper atmosphere of the sun. The solar wind creates the heliosphere, a vast bubble in the interstellar medium surrounding the solar system.

5)http://en.wikipedia.org/wiki/Solar_wind
6)http://burro.astr.cwru.edu/stu/advanced/sun_phenomena.html

Other phenomena include geomagnetic storms that can knock out power grids on Earth, the aurorae (northern lights) and the plasma tails of comets that always point away from the sun. Geomagnetic storms are major disturbances of the magnetosphere that occur when the interplanetary magnetic field turns southward and remains southward for an prolonged period of time. Geomagnetic storms are classified as recurrent and non-recurrent. Recurrent storms occur every 27 days, corresponding to the Sun's rotation period. They are triggered by the Earth's encounters with the southward- oriented magnetic field of the high-pressure regions formed in the interplanetary medium by the interaction of low- and high-speed solar wind streams co-rotating with the Sun. the aurora energization process draws its energy from the interaction of the Earth's magnetosphere with the solar wind.The solar wind is the outermost atmosphere of our sun. The sun is so hot that it boils off its outer layers, and the result is a constant outward expanding very thin gas. This solar wind consists not of atoms and molecules but of protons and electrons (this is called a plasma). Embedded in this solar wind is the magnetic field of the sun.

Fusion reactions power the stars and produce all but the lightest elements in a process called nucleosynthesis. Although the fusion of lighter elements in stars releases energy, production of elements heavier than iron absorbs energy. The fusion of two nuclei with lower mass than iron (which, along with nickel, has the largest binding energy per nucleon) generally releases energy while the fusion of nuclei heavier than iron absorbs energy; vice-versa for the reverse process, nuclear fission. In the simplest case of hydrogen fusion, two protons have to be brought close enough for their mutual electric repulsion to be overcome by the nuclear force and the subsequent release of energy.