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Activity Above the Sun’s Photosphere

Activity Above the Sun’s Photosphere. One can view the portions of the Sun above the photosphere by looking at a specific emission line This photo shows the Sun taken with a filter that passes light corresponding to transitions in calcium. The bright spots are called plages

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Activity Above the Sun’s Photosphere

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  1. Activity Above the Sun’s Photosphere • One can view the portions of the Sun above the photosphere by looking at a specific emission line • This photo shows the Sun taken with a filter that passes light corresponding to transitions in calcium • The bright spots are called plages • Plages are regions of higher temperature that actually all the elements, not just the one being photographed Lecture 15

  2. Prominences • Higher in the Sun’s atmosphere we find prominences that usually originate near sunspots Lecture 15

  3. Solar Flares • Solar flares are the most violent event on the surface of the Sun • Flares seem to occur when various magnetic field lines rearrange themselves releasing huge amounts of energy Lecture 15

  4. Active Regions • Sunspots, flares and bright regions in the Sun’s chromosphere and corona tend to occur together • These phenomena appear at the same geographic location on the surface of the Sun but take place at different depths in the atmosphere of the Sun • These different phenomena can be seen with different wavelength EM radiation • All three pictures on the right were taken at the same time • Top is x-ray • Hot corona • Left is helium light • Strong chromospheric emission • Right is the magnetic field Lecture 15

  5. Variations in the Number of Sunspots • The number of sunspots varies with a period of around 11 years • There is evidence also of variance in the total number of sunspots over time • There is evidence that high energy cosmic rays are less abundant during high sunspot activity while low energy charged particles are more abundant Maunder minimum Lecture 15

  6. Solar Variability • Changes in solar activity affects the Earth’s climate • The Maunder minimum in sunspot activity corresponds with a very cold time in Earth’s history • 1645 - 1715 • Other cold times include 1400 - 1510 • Warm times include 1100 to 1250 • The Sun is 0.1% brighter (more energy) during solar maximum • Should not be enough to change the Earth’s climate • UV radiation is 1% higher • May affect the ozone layer • A 1% change in solar output would be necessary to affect the Earth’s climate and we do not see such variations • Other stars to show such variations so it seems possible that our Sun could have varied in the past although we have never seen more that 0.1% variation Lecture 16

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