Why Are You So Violent, My Sun?
Our Sun provides heat and light. Life on Earth would not exist without it. From a distance, the Sun looks like a calm, glowing yellow ball. After all, it is a ball of gas like every other star. But don't get too close. The Sun seems to have an explosive temper.
Image to right: The different layers of the Sun change over time and places on the Sun. These changes are called solar activities. Credit: McREL
The different parts of the Sun have different activities. Some of the names of these activities give a clue to the Sun's violent nature: flares and coronal mass ejections. Not only that, but the Sun is also a huge thermonuclear reactor. Within the Sun’s core, it fuses hydrogen atoms into helium atoms. As is does, it takes a small amount of mass of the hydrogen atoms and violently releases large amounts of energy when they join to become helium atoms. This process is called nuclear fusion. This reaction produces temperatures in the millions of degrees. It's what gives the Sun its heat and light.
Near the seemingly calm surface of the Sun, matter rises and bubbles like a fierce, boiling cauldron. Electrically charged particles bubble from the Sun's surface. They are in the state of matter known as plasma. Plasma is like an electrified gas. These particles are known as the solar wind.
Winds, Volcanoes and Other Eruptions
The solar wind blows at speeds of around 400 kilometers per second. That is almost a million miles per hour. And, it carries a million tons of matter into space. The speed and the mass of the wind, however, do not cause problems. The particles of solar wind would barely ruffle your hair because they are so spread out. It is the energy and magnetic fields that bombard Earth's magnetosphere. And only a small amount gets through the magnetosphere -- just enough to cause a magnetic storm around Earth every once in a while. The solar wind also causes beautiful auroras.
Image to left: The Sun spits out an arch of hot gas called a prominence. Credit: NASA
Sunspots are the dark spots on the Sun. They are dark because they are much cooler than the area that surrounds them. A sunspot can be the size of Earth or larger. But beside them are the solar flares -- the bright spots. A solar flare is when the magnetic energy that is built up in the Sun's atmosphere is released in an explosion that is equal to 10 million volcanic eruptions.
The Sun's most impressive and photogenic act of violence is the prominences. These are the bright loops of hot gas that arch above its chromosphere. Some of the prominences are as wide as the Earth. Some may stretch out almost the diameter of the Sun. They may hold their shape for months before collapsing. Eruptive prominences erupt from the chromosphere as gaseous streamers.
Hurricanes and Battleships
One solar activity that has the most effect on the Earth is the coronal mass ejection (CME). It is like the Sun's version of a hurricane. A CME comes from the Sun's corona, or outer atmosphere. A CME is the eruption of a huge bubble of plasma from the corona. The strange thing about the corona is that it is 200 times hotter than the Sun's surface, or more than one million degrees Celsius.
A CME can spit more than 10 billion tons of plasma into the solar system. This mass is equal to 100,000 battleships. The average CME hurls enough electricity into the atmosphere to double the amount of power generated in the U.S. If a CME erupts on the side of Earth that is near the Sun and the Earth's orbit passes through it, the results can be bad or beautiful.
Image to right: Did you know that to match the energy of the Sun, you would have to explode 100 billion tons of dynamite every second! Credit: NASA
As violent as the Sun may be on the surface, we desperately need it. We would be nothing without it. As long as it stays where it is, we can enjoy its benefits.
Adapted from Storms from the Sun and Solar Structure -- A Closer Look