SOLAR RADIATION1.1.Introduction

The Sun as an average star is a typical main-sequence dwarf of spectral class G-2. Its radius is 6.960 x 108m. The mean distance between the Sun and the Earth is 1.496 x 1011m and is known as the astronomical unit (AU). Solar radiation is the electromagnetic radiation emitted by the Sun. Almost all known physical and biological cycles in the Earth system are driven by the solar radiation reaching the Earth. Solar radiation is also the cause of climate change that is truly exterior to the Earth system. 1.2. DifinitionSolar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. About half of the radiation is in the visible short-wave part of the electromagnetic spectrum.The other half is mostly in the near-infrared part, with some in the ultraviolet part of the spectrum. The portion of this ultraviolet radiation that is not absorbed by the atmosphere produces a suntan or a sunburn on people who have been in sunlight for extended periods of time.

Solar radiation is more than the light and heat that we perceive from the sun. The sun is a star and it produces energy in many forms, from perceptible heat, visible and invisible spectrums of light, radiation, and more. Life on earth would be impossible without the sun, but our atmosphere also protects us from the more dangerous aspects of solar radiation. Loosely defined, solar radiation is the total frequency spectrum of electromagnetic radiation produced by the sun.

This spectrum covers visible light and near-visible radiation, such as x-rays, ultraviolet radiation, infrared radiation, and radio waves. The visible light and heat of the sun makes life possible, and is called daylight or sunshine. The earths atmosphere deflects or filters the majority of the suns harmful radiation, and our near-perfect positioning in the solar system allows us to receive the benefits proximity to the Sun without being baked or broiled like Venus or Mercury.Solar radiation and sunlight make it possible for the Earth to house life. The negative aspects of our relationship with the sun are primarily the result of human irresponsibility: we develop skin cancer when we ignore our bodies signals to avoid sunlight, and we struggle with global warming because weve ignored the environmental concerns of our actions. When we dont give solar radiation the respect it deserves, we are literally playing with fire.The total amount of radiation received at the earth's surface depends on four (4) factors:

1. The distance of the sun. Any change in the distance the Earth and the Sun cause the variation of the acceptance of solar energy. 2. Intensitas solar radiation that is the size of the angle of incidence of sunlight at the earth's surface. The amount received is directly proportional to the magnitude of the angle of incidence angles. Beam with oblique incidence angle which gives less energy on the earth's surface caused by the energy spread wide on the surface and also because the rays have to travel further atmospheric layer than if the beam at an angle perpendicular to come.

3. The length of day (sun duration), ie the distance and duration between sunrise and sunset. 4. The influence of the atmosphere. Beam through the atmosphere will be partially adsorbed by the gases, dust and water vapor, is reflected back, and the rest is emitted forwarded to the earth's surface.

As human beings, we tend to have a love-hate relationship with the sun on one hand, sunlight keeps us warm, creates food and shelter for us via plant life, and gives us light. On the other hand, as greenhouse gases trap more heat and the ozone layer allows more dangerous UV radiation in, the suns rays can be distinctly dangerous. UV rays cause skin cancer in humans and animals, but can contrastingly improve other skin conditions like psoriasis. We need the sun biologically, as well, as it causes our bodies to produce vital vitamin D. Solar radiation that falls is usually estimated by using a sunshine recorder is by Campbell Stokes. This tool measures the length or duration of bright sunshine and consists of a solid sphere made of glass. The sun's rays will be focused or concentrated by the glass ball was on a heavy paper that is sensitive and specific. Pias scale on the clock mounted on a half-bowl shaped metal concentric with the glass balls. Sunlight is focused on PIAs will burn and leave marks on the pale. Total duration of bright sunshine during the day at get by measuring the total length of the former on the pias.

Acceptance of solar radiation at the Earth's surface varies according to place and time:1. According place;

At the macro level due to differences in the location of latitude and the state of the atmosphere (clouds).

On the micro level, the amount of radiation received by the specified by the direction of the slope.

2. According to the time, the difference of radiation received; Happen in a day (from morning to evening)

Seasonally (from day to day)

Picture 2.1. Greenhouse Effect1.3. Distance of the Sun to the EarthThe Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields. It has a diameter of about 1,392,684km (865,374mi), around 109 times that of Earth, and its mass (1.9891030 kilograms, approximately 330,000 times the mass of Earth) accounts for about 99.86% of the total mass of the Solar System. Chemically, about three quarters of the Sun's mass consists of hydrogen, while the rest is mostly helium. The remainder (1.69%, which nonetheless equals 5,600 times the mass of Earth) consists of heavier elements, including oxygen, carbon, neon and iron, among others.

The Sun formed about 4.6 billion years ago from the gravitational collapse of a region within a large molecular cloud. Most of the matter gathered in the center, while the rest flattened into an orbiting disk that would become the Solar System. The central mass became increasingly hot and dense, eventually initiating thermonuclear fusion in its core. It is thought that almost all stars form by this process. The Sun is a G-type main-sequence star (G2V) based on spectral class and it is informally designated as a yellow dwarf because its visible radiation is most intense in the yellow-green portion of the spectrum, and although it is actually white in color, from the surface of the Earth it may appear yellow because of atmospheric scattering of blue light. In the spectral class label, G2 indicates its surface temperature, of approximately 5778K (5505C), and V indicates that the Sun, like most stars, is a main-sequence star, and thus generates its energy by nuclear fusion of hydrogen nuclei into helium. In its core, the Sun fuses about 620million metric tons of hydrogen each second.

The Sun is currently traveling through the Local Interstellar Cloud (near to the G-cloud) in the Local Bubble zone, within the inner rim of the Orion Arm of the Milky Way. Of the 50 nearest stellar systems within 17 light-years from Earth (the closest being a red dwarf named Proxima Centauri at approximately 4.2 light-years away), the Sun ranks fourth in mass. The Sun orbits the center of the Milky Way at a distance of approximately 2400026000 light-years from the galactic center, completing one clockwise orbit, as viewed from the galactic north pole, in about 225250million years. Since the Milky Way is moving with respect to the cosmic microwave background radiation (CMB) in the direction of the constellation Hydra with a speed of 550km/s, the Sun's resultant velocity with respect to the CMB is about 370km/s in the direction of Crater or Leo.

The mean distance of the Sun from the Earth is approximately 1 astronomical unit (150,000,000km; 93,000,000mi), though the distance varies as the Earth moves from perihelion in January to aphelion in July. At this average distance, light travels from the Sun to Earth in about 8 minutes and 19 seconds. The energy of this sunlight supports almost all life[b] on Earth by photosynthesis, and drives Earth's climate and weather. The enormous effect of the Sun on the Earth has been recognized since prehistoric times, and the Sun has been regarded by some cultures as a deity. An accurate scientific understanding of the Sun developed slowly, and as recently as the 19th century prominent scientists had little knowledge of the Sun's physical composition and source of energy. This understanding is still developing; there are a number of present day anomalies in the Sun's behavior that remain unexplained.

The sun rotates on its axis for about 27 days to reach one round. This rotational movement was first noticed through observation of sunspots change position. The sun's rotation axis tilted as far as 7.25 from the axis of Earth's orbit so that the north pole of the Sun will be visible in September while the south pole of the Sun is more visible in March. The sun is not a solid ball, but a ball of gas, so the sun does not rotate with a uniform velocity. Astronomers suggested that the rotation of the interior of the Sun is not the same as the surface. The core and the radiative zone rotates simultaneously, while the convective zone and photosphere also rotate together but at different speeds. Equatorial part (middle) rotation takes about 24 days while the poles rotate for about 31 days. Source of the Sun's rotation period difference was observed. The sun and the entire solar system moving in its orbit around the Milky Way. The sun is as far as 28,000 light-years from the galactic center of the Milky Way. The average speed of this movement is 828.000 km / h so it is expected to take 230 million years to reach a perfect lap around the galaxy.

Picture 1.2. Solar Rdiation

Table 1.1. Characteristics Solar

Mean distancefrom Earth1.496108km8min 19s at light speed

Visual brightness (V)26.74

Absolute magnitude4.83

Spectral classificationG2V

MetallicityZ = 0.0122

Angular size31.632.7

AdjectivesSolar

Orbital characteristics

Mean distancefrom Milky Way core2.71017km27200light-years

Galactic period(2.252.50)108 a (years)

Velocity220km/s (orbit around the center of the Galaxy)20km/s (relative to average velocity of other stars in stellar neighborhood)370km/s (relative to the cosmic microwave background)

Physical characteristics

Mean diameter1392684km

Equatorial radius696342km109 Earth

Equatorial circumference4.379106km109 Earth

Flattening9106

Surface area6.08771012km211990 Earth

Volume1.4121018km31300000 Earth

Mass1.98911030kg333000 Earth

Average density1.408103kg/m30.255 Earth

DensityCenter (model): 1.622105kg/m3Lower photosphere: 2104kg/m3Lower chromosphere: 5106kg/m3Corona (avg): 11012kg/m3

Equatorial surface gravity274.0m/s2

27.94g27542.29cgs28 Earth

Escape velocity(from the surface)617.7km/s55 Earth

TemperatureCenter (modeled): 1.57107KPhotosphere (effective): 5778KCorona: 5106K

Luminosity (Lsol)3.8461026W3.751028lm98lm/W efficacy

Mean intensity(Isol)2.009107Wm2sr1

Age4.6 billion years

Rotation characteristics

Obliquity7.25(to the ecliptic)67.23(to the galactic plane)

Right ascensionof North pole[11]286.1319 h 4 min 30 s

Declinationof North pole+63.8763 52' North

Sidereal rotation period(at equator)25.05 days

(at 16 latitude)25.38 days25 d 9 h 7 min 12 s

(at poles)34.4 days

Rotation velocity(at equator)7.189103km/h

Photospheric composition (by mass)

Hydrogen73.46%

Helium24.85%

Oxygen0.77%

Carbon0.29%

Iron0.16%

Neon0.12%

Nitrogen0.09%

Silicon0.07%

Magnesium0.05%

Sulfur0.04%

1.4. Characteristics Solar Radiation1.4.1. Wavelength Solar Radiation

The electromagnetic spectrum consists of all ranges of frequency and wavelength. Electromagnetic waves can propagate in vacuum or no vacuum. Under vacuum conditions, the nature of the wave is more prominent. Meanwhile, when the waves interact with atoms or molecules, then the wave behaves like a beam korpuskul (small particles) are called photons (photon) or light quanta (quanta) (Jones 1986, Bueche 1989). Set the type of energy the electromagnetic spectrum by wavelength and frequency. Peak wavelength (m, in nm) radiation emitted from an object is too dependent on the temperature of the object in accordance with the laws of the states of the shift Wien shift law where, "the wavelength of maximum intensity decreases with increasing temperature"

Picture 1.2. Peak wavelength calculation1.4.2. Types of Solar RadiationSolar radiation is the radiation released by the Sun . Approximately 99.9 percent of energy in the form of electromagnetic radiation with wavelengths between 0.15 s / d 4.0 microns with the highest percentage of the intensity of the 0.4 s / d 0.7 microns in the form of light . The rest of electromagnetic energy in the form of infrared and ultraviolet ( UV ) . Solar radiation which penetrates the lowest layer of the atmosphere can also be divided into several classes , namely :a) Direct solar radiation is the solar radiation coming from the sun disc rounded corners .b) Global solar radiation that the solar radiation received by a horizontal surface in the form of direct solar radiation and radiation scattered downwards while passing through a layer of the atmosphere .c) Sky radiation is solar radiation scattered downward by atmospheric layer (the second part of the global radiation) .d) that the reflected solar radiation Solar radiation reflected upward by the earth's surface and scattered by atmospheric layer between the earth's surface and the observation point .1.4.3. Solar Radiation at Earth's SurfaceAcceptance of solar radiation at the earth's surface varies greatly depending on :1. Place , ie the location and circumstances latitude clouds.2. Time , which is a day ( morning - afternoon ) and seasonal ( day -to-day )Various matahri spectrum : ( micro meters ) Cosmic rays (10-10-10-6 )

Gamma rays ( 10-6 -10-2 )

Ultra violet ( 10-2 - 101 )

Visible light

Infra red ( 101 -103 )

The radio waves (103 - 1010)

1.4.4. Factors Affecting Acceptance of Solar Radiation at Earth's SurfaceThe distance from the Sun to Earth. Earth around the Sun ( revolution ) with elliptical trajectory , distance changes cause variations in solar radiation receipt.

Perihelion: Maximum Radiation 2:01 ly.min - 1 ( January 3 closest distance )Aphelion : 1.88 Minimum Radiation ly.min -1 ( longest distance 4 July )The length of day and the angle of incidence. In addition to the atmosphere caused by solar radiation acceptance angle of fall . Beam fell on his side , giving less radiation energy as the layer becomes thicker atmosphere and reflected light stout . Angle of incidence of sunlight depending on the location of latitude and season , length of day caused by latitude location ( latitude ) , occurs as a result of differences in the period of receipt of solar radiation.

The effect of Earth's atmosphere The atmosphere as a protection from solar radiation destructive , solar energy will experience penguragan energy by atmospheric molecules .Atmospheric ingredients that play a role in the absorption of solar radiation atomic oxygen in the air above the lap absorb the extreme ultraviolet ( 0:12 to 0:18 lm ) ozone , ultraviolet absorbing 0:22 to 0:33 lm , and partly with wavelengths 0.44-0.76 lm

Water vapor absorbs infrared P. Gel 0.93 , 1:13 , 1:42 and 1:47 lm Carbon dioxide , absorbing spectrum of 2.7 lm ( near infra red ). Diffuse Radiation : a mix between light scattering ( solar radiation ) and light reflection . Global Radiation : Radiation scattering and reflection of radiation .1.5. Surface Energy Balance on Earth

Energy balance, according to which energy cannot be created or destroyed, only modified in form. Surface Energy Balance on Earth calculation:

Q n = Q s + Q l- Q s Q l Q n: netto radiation (Wm-2) Q s

Q s: coming in and out solar radiation (Wm-2) Q l Q l: coming in and out longwave radiation (Wm-2).

Picture 1.3. Global Energu Flows

1.6. Campbell Stokes

Solar radiation that falls is usually estimated by using a sunshine recorder is by Campbell Stokes. This tool measures the length or duration of bright sunshine and consists of a solid sphere made of glass. The sun's rays will be focused or concentrated by the glass ball was on a heavy paper that is sensitive and specific. Pias scale on the clock mounted on a half-bowl shaped metal concentric with the glass balls. Sunlight is focused on pias will burn and leave marks on the pale. Total duration of bright sunshine during the day at get by measuring the total length of the former on the pias.

Picture 1.4. Campbell Stokes1.7. ConclutionThe radiation coming directly from the Sun received at the Earths surface is called direct solar radiation. The amount of scattered radiation coming from all other directions is called diffuse solar radiation. The sum of both components as received on a horizontal surface is called global solar radiation.