Credit: Solar Dynamics Observatory; NASA
Approaching Peak Solar Activity
The solar atmosphere is somewhat unusual in that, unexpectedly, temperature increases the more you move away from the solar core, the source of all solar power. This heating comes about because of instabilities in the Sun's magnetic field, which can cause the explosive release of huge amounts of electromagnetic energy, producing sunspots and solar flares and other types of solar activity. Large solar flares provide some of the energy input, along with frequent, small flaring events ("nanoflares") which are also thought to be a significant component in heating the solar atmosphere. This activity dumps enormous amounts of energy into the upper layers of the solar atmosphere, heating the chromosphere and corona to extraordinary temperatures. The image above shows today's state of the solar atmosphere as a composite low-energy X-ray image of the Sun obtained by the Atmospheric Imaging Assembly imager on the Solar Dynamics Observatory. Colors indicate temperatures ranging from about 100,000 degrees Celsius (red) to 200,000 degrees Celsius (blue). By contrast, the Sun's surface, the photosphere, which is relatively cool (only about 5,000 degrees), appears dark in this image. The Sun is approaching its maximum state of cyclical magnetic activity, when the number of solar storms and solar flares reaches its peak. Each solar cycle lasts 11 years peak to peak, and the last peak occurred in January 2014. At solar maximum, which may (somewhat prematurely) be reached by then end of this year or shortly thereafter, the solar corona is very extensive, and powerful ejections of matter from the corona can frequently occur. Some of these coronal mass ejections may collide with earth and produce beautiful and harmless aurorae for denizens of earth, but can pose a significant danger to machines and humans in space. The solar corona, usually too faint to be seen from earth, can be seen during total solar eclipses. The next total solar eclipse occurs on April 8, 2024, and the band of totality stretches across the US, from the southwest to the northeast. If you're in the band, you have the chance to see the solar corona in what should be a spectacularly expansive state.
Published: July 24, 2023
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Page Author: Dr. Michael F. Corcoran
Last modified Tuesday, 27-Feb-2024 10:08:17 EST