The Sun

Description of Sol

Property	Value
Mass	$1 M_{⊙} = 1.989 \times 10^{30} kg$
Radius (photosphere)	$1 R_{⊙} = 696, 000 km$
Mean density	$1410 {kg m}^{- 3}$
Irradiance (at Earth)	$1.368 {kW m}^{- 2}$
Luminosity	$3.85 \times 10^{23} kW$
Surface gravity	$274 {m s}^{- 2}$
Effective temperature	$5778 K$
Age	$4.6 \times 10^{9} years = 4.6 Gyr$
Mean distance from Earth	$1 AU = 149, 600, 000 km = 1 / 206265 parsec$
Rotation period	$\sim 25 days (equator), \sim 35 days (poles)$
Rotation speed (equator)	$2 {km s}^{- 1}$
Magnetic field strength (typical values)	General solar $\sim 10^{- 4} T$ Sunspot $\sim 0.4 T$ Chromospheric plage $\sim 0.02 T$ Prominence $\sim 0.001 - 0.01 T$
Solar wind velocity	$300 - 700 {km s}^{- 1}$
Solar wind mass loss	$5 \times 10^{16} kg/year = 2.5 \times 10^{- 14} M_{⊙} / year$
Spectral type	G2V
Absolute visual magnitude, $M_{v}$	$+ 4.83$
Relative visual magnitude, $m_{v}$	$- 26.74$
The density is in the same range as water.

Structure

The solar interior
- Dense core
  - Temp.: 15 million °C
  - Nuclear fusion occurs
- Radiation Zone
  - Energy travels from the core outwards as light. Because the material is very dense, a photon can get bounced around a lot and can take up to 100'000 years to traverse this layer.
- Convection Zone
  - Slightly cooler plasma that is less dense. Energy is moved via convective currents.
The solar atmosphere
- Photosphere
  - This is the "surface" of the Sun that we see from earth. It isn't solid, but rather a layer of gas. This is where sunspots appear.
- Chromosphere
  - A thin, reddish layer sitting above the photosphere. It is usually invisible to the naked eye because the photosphere is so bright, but can be seen during a total solar eclipse.
- Corona
  - The outermost part of the atmosphere, extending millions of kilometers into space. It is incredibly thin but mysteriously much hotter than the surface of the Sun.
  - The Earth sits in the corona

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The Energy Source in the core

In the core, there is nuclear fusion through the proton-proton chain.

Photosphere

On the Surface there is a structure, these are convective cells.

Rotation and magnetic field

The sun does not rotate the same on the surface. This differential Rotation acts on the magnetic field of the sun.

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Sun cycle

The cycle has a duration of 22 years and a magnetic field inversion every 11 years.
In the cycle Solar activity changes with also the amount of Sunspots. A maximum also coincides with Solar flares and Coronal mass ejections. We are probably at the end of the modern maximum.

The cycle of the sun coincides with magnetic flips.
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Sunspots

Are the places where the magnetic field lines break through the surface of the sun. The regions of the sunspots are also one of the hottest regions.

Solar Wind

Originate from coronal holes with a open magnetic field (400-800 km/s)
Slow wind originates from active near-equatorial regions assosiated with clodes magneic structures (250-400 km/s)

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