AST- 105 1st EditionLecture 10Outline of Last LectureI. The Structure of the SunOutline of Current Lecture I. SunspotsII. Solar Wind and EarthCurrent Lecture I. Sunspotsa. Sunspots- cooler regions (4500 K) in photosphere; regions of strong magnetic field which block heat flow.i. Emit less light than surrounding areasii. Typically are equivalent to the size of Earth (approx. 10,000 km) or largeriii. Appear in groupsiv. Last approximately two months.b. Galileo discovered that the rotation period of the Sun is about 4 weeks by following trends and patterns in sunspots.c. Sunspot Cycle- average number of spots varies with a period of approximately 11 years.i. A sunspot cycle is caused by interaction between the Sun’s rotation and magnetic field.ii. Sunspot maximum- last occurred in late 20001. Current cycle appears to have reaches a maximum in mid-2013, about 2 years late.d. Causes of a Solar Cyclei. Sun rotates faster at equator than near the poles.1. This is seen by observing the sunspots.ii. Magnetic field surrounding the Sun gets twisted up and amplifiediii. The Sun becomes more active as the field strengthens1. Field finally breaks down and reforms every 11 years.e. Active Regionsi. Prominence- looping region of hot gas extending into corona1. Supported by magnetic field loop that pops out through sunspotsii. Flare- violent release of energy and particles from a small region in solar atmosphere1. Results from instability in the Magnetic FieldII. Solar Wind and Eartha. Solar Wind- stream of mostly protons and electrons escaping from coronai. Flow out through solar systemii. Reach Earth in a few daysiii. Some particles are trapped by Earth’s magnetic field. b. Effect of Solar Storms on Earthi. Aurora- northern and southern lights near Earth’s polesii. Causes changes in Earth’s
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