![]() ![]() This effect deals with the abundances of elements in the Corona. But since the ozone layer blocks UV and X rays (thankfully, otherwise we would not exist as we do now!), Coronal studies began only with advent of the space age and satellites in the 1960s.Īnother phenomenon that is related and similarly astonishing to the ‘Coronal Heating Problem’ that occurs in the transition region and the Corona is called as the First Ionization Potential (FIP) Effect. This means that telescopes on the Earth are enough to observe and study the Photosphere. As we have seen, since the Corona is at a million degree kelvin temperature, it emits mainly in the high energy part of the spectrum, that is, in UV and X-rays, while the Photosphere emits mainly in optical wavelengths that we can perceive with our naked eyes. The innermost regions of the fire will be bluish compared to the outer parts, which will be red, orange and yellow. You can see this in daily life in the flames of a stove. This is because the hotter a material is, the light coming from it will be of higher energy. The Corona is mainly visible in UV and X rays. You can read more about this in the article: Using machine learning to infer Solar Coronal heating The reason for this temperature increase in the solar atmosphere is one of the long standing problems of solar physics referred to as the Coronal Heating Problem. More mystifyingly, things get extremely hot (literally) as we move into the next layer, the transition region, which is just a 100 km in height but the temperature drastically increases from a few thousand kelvin to a few million kelvin! Temperature stays at a million degree kelvin in the Corona (which extends throughout the solar system) as well, which is the uppermost atmospheric layer of the Sun. ![]() As the numbers show, in the Chromosphere, as we move upwards it gets hotter and not cooler as common sense suggests! The temperature in the Chromosphere varies between about 4000 K at the bottom and 8000 K at the top. The next layer is the Chromosphere, that is in between a height of about 400 - 2100 km. This is expected because as we move away from a source of energy and heat, the temperature drops. The temperature here decreases from 6000K, at the bottom of the layer, to 4500K at the top of the layer. The visible orange-yellow surface of the Sun that we can see even with the naked eye is called the Photosphere. ![]() This article explains how these measurements were made. By studying the XSM spectra for the days when the Sun was very quiet, researchers have found that the abundances of all Mg, Al, Si is around two times higher than its abundances in the photosphere! They also calculated the temperature of the quiet Sun corona to be around 2 MK. XSM onboard Chandrayaan-2 observed the Sun during the deepest solar minimum of the past century from in 2019-2020. ![]()
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