Questions: The Sun: Structure, Sunspots, and Solar Activity
4 questions to test your understanding
Score: 0 / 4
Question 1 Multiple Choice
Why do sunspots appear dark?
AThey are holes through which we see the cold interior of the Sun
BThey are regions of strong magnetic field that slow convection, so they are cooler and less bright than the surrounding photosphere
CThey are clouds of dust floating above the surface
DThey are shadows cast by planets passing in front of the Sun
Strong magnetic fields in sunspots inhibit the convective flow that carries heat to the surface. The spot cools to roughly 4,000 K, compared with about 5,800 K for the normal photosphere, and appears dark by contrast. On its own, a sunspot would glow brightly.
Question 2 Short Answer
About how long is the sunspot cycle, and what happens to the Sun's magnetic field over each cycle?
Think about your answer, then reveal below.
Model answer: The sunspot cycle lasts about 11 years from one minimum to the next. During each cycle the Sun's overall magnetic polarity reverses, so it takes about 22 years for the field to return to its original orientation.
The 22-year magnetic cycle is called the Hale cycle. The number of sunspots, flares, and coronal mass ejections all rise toward solar maximum and fall toward solar minimum.
Question 3 True / False
Energy produced in the Sun's core reaches the surface in a few seconds because light travels so fast.
TTrue
FFalse
Answer: False
In the dense radiative zone, light is absorbed and re-emitted countless times, taking a random path. Estimates for the time energy takes to pass through it range from tens of thousands to hundreds of thousands of years. After leaving the photosphere, light reaches Earth in about 8 minutes.
Question 4 Multiple Choice
A large coronal mass ejection is aimed at Earth. Which effect is most likely one to three days later?
AA rise in Earth's average surface temperature of several degrees
BA geomagnetic storm with bright auroras at lower latitudes than usual and possible disruption of satellites and power grids
CA total solar eclipse
DA sharp increase in ocean tides
A CME carries a huge cloud of magnetized plasma. When it strikes Earth's magnetosphere, it can cause a geomagnetic storm. In March 1989, such a storm caused a blackout across the Hydro-Québec power grid in Canada.