Plages are phenomena of stellar activity.
Where can I find openly-accessible data of plage regions of the Sun with other parameters such as faculae region, magnetic field, etc?
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1$\begingroup$ This question might be better suited for Astronomy. $\endgroup$– Michael SeifertCommented Oct 30, 2021 at 13:47
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$\begingroup$ Yes, I am going to post it there. $\endgroup$– AutodidactCommented Oct 31, 2021 at 7:33
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$\begingroup$ Have you gone to sdo.gsfc.nasa.gov and clicked on the Data dropdown tab? $\endgroup$– honeste_vivereCommented Dec 6, 2021 at 14:35
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2 Answers
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All of these are related. The important concept is that regions of high magnetic field (sunspots) are colder. The reason is roughly that the high magnetic fields there exert a pressure of $B^2/2\mu_0$, which in sunspots is almost as large as the pressure from the gas, $n k_B T$. The pressure is roughly in equilibrium across the star, so the high $B$ regions must have correspondingly lower temperature. This factor the sunspot temperature is $\approx 2/3$ that of other regions.
The reason why we can visibly see such a difference, which leads to us defining Plage regions, etc. is that the luminosity, L, famously goes as $T^4$, resulting in sunspots that are several times less bright than other regions.
As far as Ca and K go, I'm not an expert, but the idea I believe is that the $B$ field causes a splitting in the energy levels of these atoms through the Zeeman effect. If you look at the wavelength that corresponds to the difference between two energy levels, you'd find less absorption than normal in high $B$ regions (sunspots) because the actual absorption lines are pushed away.
Edit: Note the question has completely changed (and been closed) since this answer is posted.
answered Oct 27, 2021 at 14:38
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$\begingroup$ No problem! Please accept it if you think it is sufficient. $\endgroup$ Commented Oct 27, 2021 at 14:51
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$\begingroup$ Your answer is good but is not sufficient for a complete answer of my question, I am in search of much more detailed answer with graphical interpretation as well. $\endgroup$ Commented Oct 27, 2021 at 19:06
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On the following site Plage Area (1892-2019) developed by Dr Natalie Krivova ( Minerva group "Solar Variability and Climate", Group Leader) we can find out the data for Plage regions of the Sun.