Temp increase of sun from photosphere to corona

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Discussion Overview

The discussion centers around the temperature gradient from the photosphere to the corona of the Sun, exploring why temperatures increase as one moves away from the core. Participants are examining the implications of these temperature differences and the mechanisms behind them, including ionization and energy sources.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants state the temperatures of the photosphere, chromosphere, and corona, noting discrepancies in these values.
  • One participant suggests that the corona's high temperature is due to ionization caused by energy from the photosphere and chromosphere, influenced by solar activity and magnetic fluctuations.
  • Another participant questions the relationship between temperature and ionization, asking whether ionization is a result of high temperatures or if high temperatures are achieved due to ionization energy.
  • It is noted that the chromosphere is hotter than the photosphere due to electromagnetic radiation, magnetic disturbances, and acoustic excitation.
  • Participants mention that the mechanisms of coronal heating were historically unclear, but several mechanisms are now recognized, involving complex plasma physics.

Areas of Agreement / Disagreement

Participants express differing views on the specific temperatures of the solar layers and the mechanisms behind the heating of the corona. There is no consensus on the cause-and-effect relationship between temperature and ionization.

Contextual Notes

Participants reference various energy sources and mechanisms without resolving the complexities of the interactions involved. The discussion highlights the need for further exploration of the physics underlying these phenomena.

nautica
The photosphere is 4500 K
The chromosphere is 10000 K
The corona is 1,000,000 K

The temperature increases as the distance from the core increases. This makes no sense to me.

Any ideas?

Thanks
Nautica
 
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nautica said:
The photosphere is 4500 K
The chromosphere is 10000 K
The corona is 1,000,000 K

The temperature increases as the distance from the core increases. This makes no sense to me.

Any ideas?

Thanks
Nautica
Those temps are a bit off:
-The photosphere is ~5700-5800 K.
-The chromosphere is 10000 K to ~500,000 K, mean of ~100,000K.
(and only about 2000-3000 Km thick)
-The corona is 1 million K to >3 million K.

The corona is hot because it is ionized with electrons removed from the atoms by radiation from the photosphere and chromosphere "below". The amount of energy provided to coronal material depends on the current state of solar activity, CME's and magnetic fluctuations. At very high temperatures, iron atoms can have 9 to 13 electrons ejected. Nine-times ionized iron is only produced at temperatures of 1.3 million K and 13-times ionized iron means the temperature gets up to 2.3 million K. During strong solar activity, the temperature can reach 3.6 million K from 14-times ionized calcium.
 
Is the the ionization the result of the 2.3 million K or does the temp reach 2.3 million K b/c of the ionization energy.?

Cause or Effect?

Nautica
 
^^^^^^^^^^^^^^ :confused:
 
nautica said:
Is the the ionization the result of the 2.3 million K or does the temp reach 2.3 million K b/c of the ionization energy.?

Cause or Effect?

Nautica
The chromosphere is hotter than the photosphere from (1) photosphere EM radiation (whole spectrum) (2) strong magnetic disturbances (fluctuations from the photosphere and below) and (3) acoustic excitation.

Add all of this to the energy from CME's, which originate from the chromosphere, not photosphere, and the additave energy of all sources excites (ionizes) the elements already existing in the corona. Therefore, the coronal elements are "heated" by these sources causing the ionization. Otherwise, there would be no source of energy to cause the strong ionization of iron, calcium, etc.
 
For quite a long time the mechanism by which the corona is heated was very much a mystery. As Labguy said, there are several mechanisms now recognised. In developing a detailed understanding of the photosphere/chromosphere/corona, a good deal of pretty hairy physics was done, esp plasma physics. Perhaps a PF member can recommend a good review book or paper?
 

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