Science and Space

space and astronomy articles.

Solar Flares

Solar flares are tremendous explosions on the surface of the Sun. A solar flare occurs when magnetic energy that has built up in the solar atmosphere is suddenly released. Radiation is emitted across virtually the entire electromagnetic spectrum, from radio waves at the long wavelength end, through optical emission to x-rays and gamma rays at the short wavelength end. The amount of energy released is the equivalent of millions of 100-megaton hydrogen bombs exploding at the same time! The first solar flare recorded in astronomical literature was on September 1, 1859. Two scientists, Richard C. Carrington and Richard Hodgson, were independently observing sunspots at the time, when they viewed a large flare in white light.

In a matter of just a few minutes solar flares heat material to many millions of degrees and release as much energy as a billion megatons of TNT. They occur near sunspots, usually along the dividing line (neutral line) between areas of oppositely directed magnetic fields.

Flares release energy in many forms - electro-magnetic (Gamma rays and X-rays), energetic particles (protons and electrons), and mass flows. Flares are characterized by their brightness in X-rays (X-Ray flux).

Solar flares extend out to the layer of the Sun called the corona. The corona is the outermost atmosphere of the Sun, consisting of highly rarefied gas. This gas normally has a temperature of a few million degrees Kelvin. Inside a flare, the temperature typically reaches 10 or 20 million degrees Kelvin, and can be as high as 100 million degrees Kelvin. The corona is visible in soft x-rays, as in the above image. Notice that the corona is not uniformly bright, but is concentrated around the solar equator in loop-shaped features. These bright loops are located within and connect areas of strong magnetic field called active regions. Sunspots are located within these active regions. Solar flares occur in active regions.

The frequency of flares coincides with the Sun’s eleven year cycle. When the solar cycle is at a minimum, active regions are small and rare and few solar flares are detected. These increase in number as the Sun approaches the maximum part of its cycle.

The key to understanding and predicting solar flares is the structure of the magnetic field around sunspots. If this structure becomes twisted and sheared then magnetic field lines can cross and reconnect with the explosive release of energy. In the image to the left the blue lines represent the neutral lines between areas of oppositely directed magnetic fields. Normally the magnetic field would loop directly across these lines from positive (outward pointing magnetic field) to negative (inward pointing magnetic field ) regions. The small line segments show the strength and direction of the magnetic field.

A person cannot view a solar flare by simply staring at the Sun. Flares are in fact difficult to see against the bright emission from the photosphere. Instead, specialized scientific instruments are used to detect the radiation signatures emitted during a flare. The radio and optical emissions from flares can be observed with telescopes on the Earth. Energetic emissions such as x-rays and gamma rays require telescopes located in space, since these emissions do not penetrate the Earth’s atmosphere.

Why stydy solar flares?

Solar flares have a direct effect on the Earth’s atmosphere.

• The intense radiation from a solar flare travels to Earth in eight minutes. As a result
• The Earth’s upper atmosphere becomes more ionized and expands.
• Long distance radio signals can be disrupted by the resulting change in the Earth’s ionosphere.
• A satellite’s orbit around the Earth can be disturbed by the enhanced drag on the satellite from the expanded atmosphere.
• Satellites’ electronic components can be damaged.
• Energetic particles accelerated in solar flares that escape into interplanetary space are dangerous to astronauts and to electronic instruments in space.
• Solar flares provide an opportunity to study physical processes in nature that are similar to those that occur in laboratory devices designed for the purpose of achieving controlled thermonuclear fusion.

posted by: kyawoo at 22:24 | link | comments |
sun

Comments: