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Sunspots are relatively cool areas on the surfaceof the sun, formed by changes in the sun's magneticfield. The sun's surface is very hot, approximately10,000°F, while the center of a sunspot is compara-05tively cool at about 6,000°F. Scientists do not knowexactly what causes sunspots, but the magneticfield within a sunspot is about 100 times strongerthan it is on the rest of the sun's surface. Normally,hot gases flow from the interior of the sun to the10surface, maintaining the high temperature. Withina sunspot, however, the concentrated magnetic fieldinhibits the movement of the gases, causing thesurface of the sunspot to cool.Galileo and other astronomers started recording15the sunspots they viewed through telescopes in theearly 1600s, although sunspots had been observedand recorded without telescopes for over 2,000 years.When another astronomer, Samuel Schwabe,plotted the number of sunspots recorded each year,20he found that the number increased and decreasedin a cyclic pattern. Approximately every 11 years,the number of sunspots reaches a maximum. Agraph of sunspots over the years has a fairly regularpattern of peaks and valleys, with about 11 years25between peaks. Most recently, the sunspot cyclepeaked around the middle of 2013, and it will reachits nadir around 2020.Scientists use the 11-year cycle to predict solarflares, which cause changes in Earth's atmosphere.30When two or more sunspots having magneticfields with opposite directions are near each other,the magnetic fields can interact with plasma onthe surface between the sunspots. The interactionbetween the fields sends a burst of plasma away35from the surface, forming the solar flare. Theflares quickly heat to several million degreesand release as much energy as several hundredmillion atomic bombs. Strong magnetic fields andx-rays travel from the flares to Earth, resulting in40geomagnetic storms. If these storms are strongenough, they have the potential to disrupt powerand radio communications on Earth. Satellitesare particularly susceptible to disruption by solarflares, thus causing interference with GPS, weather45prediction, and mobile phone communication. Apositive effect of these storms is that the increasedenergy and plasma particles interact with Earth'satmosphere, enhancing the auroras, also known asthe Northern (and Southern) Lights.50Sunspots do not always follow the 11-year solarcycle; there was almost no sunspot activity betweenaround 1645 and 1715. This minimum, which wasnamed the Maunder Minimum after the husbandand wife team who discovered patterns in the55location of sunspots during the 11-year solar cycle,occurred during a period of lower-than-normalglobal temperatures known as the Little Ice Age.Scientists mostly agree that the lack of sunspotactivity did not contribute very much, if at all, to60the lowered temperatures.Sunspot activity has been decreasing during thelast few cycles, and it is possible we will see anotherminimum in the next 20 years. The strength ofthe magnetic field in the sunspots also seems to65be diminishing, which could be another sign ofa minimum in our future. If we do experience aminimum, scientists will be able to learn moreabout the effect of sunspots on Earth's climate, inaddition to learning more about the sun, its surface,70and its magnetic fields.
1. The central idea of this passage is primarily concerned with
2. Which choice provides the best evidence for the answer to the previous question?
3. The author refers to the enhanced auroras resulting from solar flares mostly to
4. Which choice best describes what scientists currently understand about how solar flare activity affects the Earth?
5. Which of the following pieces of evidence would most strengthen the author's line of reasoning?
6. As used in line 34, "burst" most nearly means
7. The passage most strongly suggests that which of the following statements is accurate?
8. Which choice provides the best evidence for the answer to the previous question?
9. As used in line 48, "enhancing" most nearly means
10. Which lines from the passage are supported by the evidence in the graphic?
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