lecture16_08 - AST210 Announcements Term Test 2 is on...

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AST210 Announcements Term Test 2 is on Wednesday 12 th November. Help sessions: Thurs. 3-4 MP 203, Tues. 3-4, MP103 Final Exam: Tuesday 16 December 9-11 am (in EX100 & EX200) Public viewing night: this Thursday, McLennan Labs 16 th floor.
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Lecture 16 Sunspots, magnetic fields The Sunspot Cycle Effects on Earth's Climate. Solar flares, mass ejections.
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Sunspots and the Solar Activity Cycle (11-6) 1. Dark spots on the Sun were first reported by the Chinese in the 5 th century B.C. Galileo and Thomas Harriott were the first Europeans to report sunspots in the early 17 th century. Sunspots are temporary phenomena lasting from a few hours to a few months. 2. Sunspots are about 1,500 K cooler than the surrounding photosphere. Thus they are about 3 times less bright than their surrounding region. They are not “black”.
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NSO/AURA/NSF
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3. The explanation for sunspots involves the Sun’s magnetic field. The strength of this field can be measured using the Zeeman effect (the splitting of spectral lines by a strong magnetic field). 4. Sunspots often appear in pairs, aligned in an east-west direction, and have opposite magnetic polarities, one being north and the other south.
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A Sunspot pair: magnetic fields extending into the corona.
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Sunspot magnetic fields
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5. The magnetic field in a sunspot is about 1,000 times that of the surrounding photosphere. This suppresses the underlying convection, hence less energy gets to the surface, hence sunspots are cooler than the surrounding photosphere. 6. In 1851, Schwabe discovered the sunspot cycle, which lasts about 11 years. 7. The Sun went through a period of inactivity
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This note was uploaded on 04/22/2009 for the course AST 210 taught by Professor Prof.stefanmochnacki during the Fall '08 term at University of Toronto- Toronto.

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lecture16_08 - AST210 Announcements Term Test 2 is on...

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