1 Solar activity and sunspots 2 Our Sun Composed of 91.2 H 8.7 He 840000 miles in diameter weighs 4.41030 lbs More than 1 million Earths could fit inside and is 330000 times the weight of Earth Only body in our solar system large enough to have internal temperatures and pressures that allow nuclear fusion 3 Appears to be on fire because the H atoms collide undergoing nuclear fusion and fuse to become He This process creates enormous amounts of energy 4 On the surface can be seen darker spots called sunspots caused by huge magnetic storms Can be up to 12 times the size of Earth Figure 2.2 5 Sunspots occur in cycles with minimum and maximum averaging every 11 years Sunspots increase the amount of material ejected from the sun May have some effect on Earths climate 6 Solar Energy From Sun to Earth
Solar Activity and Solar Wind
Electromagnetic Spectrum of Radiant Energy
Intercepted Energy at the Top of the Atmosphere
7 In addition to light sun emits electrically charged particles that spread outward in all directions Called solar wind Particles move slower than light and extend beyond the edge of our solar system 8 Solar wind is deflected by Earths magnetic field toward the poles Very little enters the atmosphere Interaction of solar wind with Earths upper atmosphere create the auroras seen in regions near the poles During sunspot maxima auroras can be seen in areas much further south such as Texas and California 9 Apparent link between solar maxima and minima and Earths climate Wetter periods in midlatitudes solar maxima Droughts solar minima But weather patterns lag 2-3 years Is it just coincidence or not 10 Electromagnetic spectrum Energy travels from the sun to Earth in waves Visible light is only part of the spectrum of solar radiation Wavelength determines the type of energy (ex visible light infrared radio waves) 11 The Electromagnetic Spectrum
Sun radiates shortwave energy
Shorter wavelengths have higher energy
Earth radiates longwave energy
Figure 2.5 Figure 2.6 12 An object radiates energy in wavelengths related to its temperature Hotter objects emit shorter wavelengthsThe suns energy 47 visible 45 infrared and 8 shorter wavelengths Earth much cooler emits energy only in the infrared 13 Earths Energy Budget Figure 2.8 14 Solar and Terrestrial Energy Figure 2.7 15
Tropics receive more concentrated insolation (2.5x more) than the poles due to the Earths curvature
Figure 2.9 16 What is insolation The total amount of radiation (the full energy spectrum from the sun visible light and heat energy) That reaches the surface of Earth 17 What affects insolation
Latitude further from the equator means less insolation.
Clouds more clouds less insolation
18 Note that areas of highest insolation occur over low latitude deserts (because of frequent cloudless skies) Figure 4.4 19 Energy Pathways through the atmosphere
Passage of energy through atmosphere or water
Changing direction of lights movement without altering its wavelengths
20 Transmission Some wavelengths of solar radiation are absorbed by the atmosphere. 21 Scattering why is the sky blue Gas molecules dust water vapor in the atmosphere scatter incoming solar radiation. The smaller molecules scatter shorter wavelengths (blue light) better. Moonrise Earthrise 22 Rayleigh scattering Red light has longer wavelength blue light has shorter wavelength and is scattered more efficiently This is why our sky is blue during the day in full sun At sunset and sunrise sunlight passes through atmosphere at shallow angle and all the blue light is scattered away and only red and orange light is visible 23 The color of the sky - how clean is the air Clean air is made of small molecules scatter shorter wavelengths (blue) better blue sky On a hazy day there are larger molecules in the air all the wavelengths are scattered sky looks white 24 Diffuse radiation the downward component of scattered light Caused by scattering in the clouds Creates multi-directional light that casts shadowless light on the ground 25 Note the sky is not blue on all planets The sky on the moon looks black there is no atmosphere to scatter the light Venus has a much thicker atmosphere the sky always looks red or orange The sky on Mars looks pink because of all the dust particles blown into the atmosphere during huge wind storms
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