To us, the Sun seems like a constant source of heat and light. Compared to many other stars, that’s pretty much true. Since accurate, space-based measurements have been recorded, the total irradiance of the Sun has varied by less than 0.2%.
However, for at least several centuries, the Sun has displayed an 11-year long oscillation of increased and decreased activity that we call the solar cycle. The current solar cycle peaked between 2011 and 2014. Since then, the numbers of sunspots, which mark solar magnetic storms, and the frequency of solar eruptions, like solar flares and coronal mass ejections, have dropped off to a very low level.
Astronomers predict that the low point of the current solar cycle, called solar minimum, will occur in 2019. As solar minimum nears, the Sun’s outer atmosphere, called the corona, becomes elongated parallel to the Sun’s equator. Those who travel to the path of totality for the August 21, 2017 solar eclipse may get to see this coronal elongation for themselves during the short period when the Moon completely covers the Sun.
With solar minimum comes both good news and bad news. The bad news is that people who like to study sunspots will have less to see. And colorful aurora, created by the interaction of solar storms with Earth’s atmosphere, will be infrequent and mostly limited to high latitudes. The good news is that during solar minimum, we on Earth are less likely to experience disruptions in radio communications and GPS reception due to solar storms. Also, potentially devastating electrical power outages due to solar storms are less likely to occur, and satellite operators and astronauts may have fewer problems.
Western Slope Skies is produced by members of the Black Canyon Astronomical Society. This episode was written and recorded by Art Trevena.
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