(See image) At what distance does the temperature of the Corona decline?

In summary, the temperature of the Sun's Corona increases from 4,500 K to over 1 million K at 20,000 km above the photosphere and then drops quickly with distance. There is no mechanism to decelerate the speed of ions in corona gas, so the temperature remains high. The solar wind, which originates from the corona, has a much higher temperature. However, the temperature of interplanetary space in our solar system is not over 1 million K as the corona is very tenuous and the majority of heat transfer is through radiative means. The temperature in the shadow of a planet or moon in space is around 2.73 K.
  • #1
smithpa9
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My astronomy textbook includes this graph of the temperature of the Sun's Corona versus the distance above the photosphere. It appears to go up from 4,500 K to over 1 million K at 20,000 km above the photosphere. But at what point does it come back down? Or does it not? Does that mean the temperature of the interplanetary space in our solar system is really over 1 million degrees K? (Source: Astronomy Today, 9th edition, by Chiasson and McMillan. Pearson Publishing, 2017).
 

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I, a layman of astronomy, think there seems no mechanism to decelerate speed of ions in corona gas, so temperature is maintained. I read in Wiki Solar Wind that solar wind originated from corona gas I think, has much higher temperature. There should be mechanism of accelerating solar gas by magnetic field.
 
  • #3
smithpa9 said:
But at what point does it come back down?

it drops again quickly with distance from the sun

smithpa9 said:
Does that mean the temperature of the interplanetary space in our solar system is really over 1 million degrees K?

Of course not, else everything in interplanetary space would be toasted to a crisp, including everything in orbit around the Earth.
Even in the near proximity of the Sun, the Corona is very tenuous, (thin) it's about 0.0000000001 times that of the Earth's sea-level
atmosphere, says one report from NASA (https://imagine.gsfc.nasa.gov/science/objects/sun1.html)

The temperature of an object in space in sunlight is 394 K. Keep in mind that the majority of "heat" transferred from the Sun
is radiative, that is IR radiation. The solar wind is just too thin to transfer heat by conduction or convection.

The temperature in space in the shadow of a planet/moon is approx. 2.73 K (-270.42 Celsius), just above abs. zero. That being the
temperature of the CMB ( Cosmic Microwave Background).Dave
 

1. What is the Corona?

The Corona is the outermost layer of the Sun's atmosphere. It is made up of extremely hot gases and is visible during a total solar eclipse.

2. Why does the temperature of the Corona decline?

The temperature of the Corona declines because the gases in this layer are further away from the Sun's surface, which is the source of its heat. As the distance increases, the gases become cooler.

3. What is the distance between the Sun's surface and the Corona?

The distance between the Sun's surface and the Corona can vary, but on average it is around 1 to 3 million kilometers.

4. How does the temperature of the Corona compare to the Sun's surface?

The temperature of the Corona is significantly higher than the Sun's surface. While the surface of the Sun has a temperature of about 5,500 degrees Celsius, the Corona can reach temperatures of up to 2 million degrees Celsius.

5. How does the distance affect the temperature of the Corona?

The distance does have an effect on the temperature of the Corona. As the distance increases, the temperature decreases. This is because the gases in the Corona are further away from the Sun's intense heat source.

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