The Sun and Solar constant

Structure of the solar atmosphere

Solar corona

Chromosphere

H = 10000 -15000 km

Photosphere, h = 100 – 300 km

T = 5000 – 6000 K

P = 100 hPa

Temperature of the Sun atmosphere decreases as the distance from its centre increases.

At the top of the photosphere temperature is believed to be 5000 -6000 K. Photosphere, as well as chromosphere, consists of partly ionized gas and the solar corona of fully ionized gas (plasma).

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Some particularities of the solar atmosphere

Solar atmosphere is non-homogeneous and very unstable.

Phenomena in the solar atmosphere

•Flares (факелы)

•Floccules-flocculi-flocculus (plasma blow out)

•Flashes (вспышки)

chromospheres flashes occur corpuscular and electromagnetic emanation are very rapid to increase

flashes duration: few minutes to a few hours. Corpuscle’s speed of about 1000 km/s.

The distance between the Sun and the Earth is about 150 000 000 km.

is the time needed for the corpuscular flux to reach the Earth and to cause magnetic storm or aurora.

1500000001000 150000 42hours

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Two successive photos of a solar flare phenomenon evolving on the sun. The solar disk was blocked in these photos for better visualization of the flare

A sunspot viewed close-up in ultraviolet light, taken by the TRACE spacecraft

http://en.wikipedia.org/wiki/File:Flare_and_after-flare_prominence.jpg

http://en.wikipedia.org/wiki/Sunspot

•Erudite question ;)

•Why Pluto is No Longer a Planet ?

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Solar spots

Some relatively	4600 K) of
irregular	are
known as
They are observed	– 35
degrees in	Duration:
from a few
The solar spots	of SOLAR
ACTIVITY (SA).
Wolfer Number (WN)
W k f 10g

K is empirical coefficient, f indicates the total number of the spots,
g denotes number of the spot groups. The WN fluctuates with the
period of 11 years (7 – 11). Minimal SA	Maximal SA
	WN 0 11	WN 40 240

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http://en.wikipedia.org/wiki/File:Solar-cycle-data.png

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Total spectrum of the solar radiation

1.	Gamma rays					5
					Visible wavelengths (μ)
				10
2.	X-rays		5				2
		Violet 0,39 – 0,455
		10		10
3.	Ultraviolet (UV)				Blue				0,455 – 0,485
				0,001				0,39
4.	Visible light				Light blue 0,485 – 0,505
				0,39 0,76
5.	Infrared (IR)				Green 0,5 5 – 0,575
				0,76 3000
6.	Radio waves				Yellow 0,575 – 0,585
				3000
	Orange 0,585 – 0,620
	Red	0,620 – 0,575
The energy emitted by the Sun is generated deep within the Sun. Like most of the stars
	the Sun is made up primary of hydrogen (71%) and helium (21%). The heavier
	elements occupy 2% only. Near the Sun centre temperature is about 16000000 K and
	the density is 150 times larger that of water. Under these conditions atoms of
	Hydrogen interact and form helium. This process generate energy in form of gamma
	radiation equal to				hydrogen bombs per second.

E 1016

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http://en.wikipedia.org/wiki/File:Atmospheric_Transmission.png

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Notion of OPTICAL WINDOW

Emittance of the Sun is close to the emittance of the a. Bb with the temperature 5800 K, max 0,4738 , and the most part of the SR

energy falls on the wavelength range 0,29 – 2,4 μ.

It has happened that the Earth’s atmosphere is the most transparent just for the same wavelength range. That is why we call this range

OPTICAL WINDOW

Wavelengths, μ	Part of SR allowed for
	passing
<0,29	1%
0,29 – 2,4	80%
>2,4	3,6%
Radio wave	100%

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Solar constant

The amount of SR (radiation flux) coming to the upper boundary of the Earth atmosphere in a unit of time to a unit of area facing the rays, at average distance between the Sun and the Earth is called

SOLAR CONSTANT		I* 1,37 kW
According to satellite measurement		0		m2
I* 1,368 1,377 kW	m2
0
Some recent measurement recorded	I0* 1,379 1,38kW		m	2

This constant includes the energy of all wavelengths coming from the

Sun. Therefore we call it Astronomic Solar Constant
For the upper part of the troposphere				I* 1,26kW	m2
(for the wavelength interval 0,346 2,4		)		0

We call it Meteorological Solar Constant.

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