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The fact that the solar corona has a temperature of a few million
degrees has puzzled solar physicists for a long time, considering the comparatively low temperature of about 6000 K at the sun's apparent surface (the photosphere). Clearly, the laws of thermodynamics seem to rule out that a cool gas volume (the photosphere) should be able to heat another gas volume (the corona) to a temperature of almost 1000 times it's own. Various elaborate plasma processes have been proposed that would enable charged particles in the photosphere to be accelerated to such high temperatures, but all these can still not explain how unordered thermal energy of many particles should be transformed into ordered high energy of a few particles. However, in the course of the 'coronal heating' discussion it has apparently not been recognized that a temperature of several million degrees is in fact the 'natural' temperature of the solar plasma (as determined by the gravitational energy), whereas the photospheric temperature is the 'abnormal' one. The further discussion involves a number of mathematical formulae as well as illustrative figures (see my page http://www.plasmaphysics.org.uk/research/sun.htm for this). |
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Thomas Smid wrote:
Various elaborate plasma processes have been proposed that would enable charged particles in the photosphere to be accelerated to such high temperatures, but all these can still not explain how unordered thermal energy of many particles should be transformed into ordered high energy of a few particles. That's because they don't *say* that, silly. The coronal heating in these theories is from energy that is initially not thermalized (magnetic energy, macroscopic fluid kinetic energy.) Paul |
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Thomas Smid wrote:
Various elaborate plasma processes have been proposed that would enable charged particles in the photosphere to be accelerated to such high temperatures, but all these can still not explain how unordered thermal energy of many particles should be transformed into ordered high energy of a few particles. That's because they don't *say* that, silly. The coronal heating in these theories is from energy that is initially not thermalized (magnetic energy, macroscopic fluid kinetic energy.) Paul |
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Thomas Smid wrote:
a temperature of several million degrees is in fact the 'natural' temperature of the solar plasma (as determined by the gravitational energy) Well I wouldn't say one temperature is "natural" and the other "abnormal", but the Corona has a temperature higher than its binding energy, so it escapes as the solar wind. The photosphere does not. , whereas the photospheric temperature is the 'abnormal' one. You are asking why the photosphere, with hotter layers above and below, stays cool? The corona is sparse and transparent, so the photosphere can radiate heat into space. In other words, the Sun shines! I don't think this fact has *completely* escaped the attention of solar physicists. Ralph Hartley |
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Thomas Smid wrote:
a temperature of several million degrees is in fact the 'natural' temperature of the solar plasma (as determined by the gravitational energy) Well I wouldn't say one temperature is "natural" and the other "abnormal", but the Corona has a temperature higher than its binding energy, so it escapes as the solar wind. The photosphere does not. , whereas the photospheric temperature is the 'abnormal' one. You are asking why the photosphere, with hotter layers above and below, stays cool? The corona is sparse and transparent, so the photosphere can radiate heat into space. In other words, the Sun shines! I don't think this fact has *completely* escaped the attention of solar physicists. Ralph Hartley |
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(Gordon D. Pusch) wrote in message ...
(Thomas Smid) writes: ^^^^^^^^^^^^^^^^^^^^^ However, in the course of the 'coronal heating' discussion it has apparently not been recognized that a temperature of several million degrees is in fact the 'natural' temperature of the solar plasma (as determined by the gravitational energy), whereas the photospheric temperature is the 'abnormal' one. Only for particles falling in from "infinity." Since we infact observe many orders of magnitude more particles _LEAVING_ the Sun than falling into it, unless you are going to postulate some sort of "invisible" incoming particle flux, your hypothesis clearly stands falsified by observational data, unless you intend to postulate some sort of in flux of "invisible" particles heating the corona. -- Gordon D. Pusch I am afraid according to the virial theorem it is completely irrelevant where the particles come from. The fact that the kinetic energy has to be -1/2 of the potential gravitational energy merely requires a steady state (read my page http://www.plasmaphysics.org.uk/research/sun.htm for more details). |
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In message , Thomas Smid
writes Are you questioning that the sun is a self-gravitating body? (now *that* would be a case for crank.net). The virial theorem applies to the sun like for any other structure held together by gravitation. Even the corona is bound to the sun as you can calculate for yourself from its temperature and the solar gravitation. Only some high energy particles escape as the solar wind. Isn't the solar wind just part of the corona? And what's the average speed of a hydrogen ion at 10^6K? -- Save the Hubble Space Telescope! |
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