Note how these different types of activity all occur above a sunspot region with a strong magnetic field. Solar Active Region Observed at Different Heights in the Sun’s Atmosphere: These four images of a solar flare on October 22, 2012, show from the left: light from the Sun at a wavelength of 171 angstroms, which shows the structure of loops of solar material in the corona ultraviolet at 304 angstroms, which shows light from the region of the Sun’s atmosphere where flares originate light at 335 angstroms, which highlights radiation from active regions in the corona a magnetogram, which shows magnetically active regions on the Sun. Such a coronal mass ejection (CME) can affect Earth in a number of ways (which we will discuss in the section on space weather).įigure 6. In some cases, immense quantities of coronal material-mainly protons and electrons-may also be ejected at high speeds (500–1000 kilometers per second) into interplanetary space. What is different about flares is that their magnetic interactions cover a large volume in the solar corona and release a tremendous amount of electromagnetic radiation. At such high temperatures, a flood of X-ray and ultraviolet radiation is emitted.įlares seem to occur when magnetic fields pointing in opposite directions release energy by interacting with and destroying each other-much as a stretched rubber band releases energy when it breaks. At the moment of the explosion, the matter associated with the flare is heated to temperatures as high as 10 million K. ![]() Near sunspot maximum, small flares occur several times per day, and major ones may occur every few weeks.įlares, like the one shown in, are often observed in the red light of hydrogen, but the visible emission is only a tiny fraction of the energy released when a solar flare explodes. The largest flares last for several hours and emit enough energy to power the entire United States at its current rate of electrical consumption for 100,000 years. A typical flare lasts for 5 to 10 minutes and releases a total amount of energy equivalent to that of perhaps a million hydrogen bombs. The most violent event on the surface of the Sun is a rapid eruption called a solar flare (Figure 3). Solar Flare: The bright white area seen on the right side of the Sun in this image from the Solar Dynamics Observer spacecraft is a solar flare that was observed on June 25, 2015. Some eruptive prominences have reached heights of more than 1 million kilometers above the photosphere Earth would be completely lost inside one of those awesome displays (Figure 2).įigure 3. The relatively rare eruptive prominences appear to send matter upward into the corona at high speeds, and the most active surge prominences may move as fast as 1300 kilometers per second (almost 3 million miles per hour). Some, the quiescent prominences, are graceful loops of plasma (ionized gas) that can remain nearly stable for many hours or even days. Eclipse observers often see prominences as red features rising above the eclipsed Sun and reaching high into the corona. Moving higher into the Sun’s atmosphere, we come to the spectacular phenomena called prominences (Figure 2) which usually originate near sunspots. It just happens that the spectral lines of hydrogen and calcium produced by these clouds are bright and easy to observe. The plages actually contain all of the elements in the Sun, not just hydrogen and calcium. These are regions within the chromosphere that have higher temperature and density than their surroundings. Pictures taken through these special filters show bright “clouds” in the chromosphere around sunspots these bright regions are known as plages (Figure 1). ![]() Astronomers routinely photograph the Sun through filters that transmit light only at the wavelengths that correspond to these emission lines. (credit: modification of work by NASA)Īs we saw, emission lines of hydrogen and calcium are produced in the hot gases of the chromosphere. The bright cloud-like regions are the plages. ![]() Plages on the Sun: This image of the Sun was taken with a filter that transmits only the light of the spectral line produced by singly ionized calcium.
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