Download Assignment 4

Astronomy 102
Name:
Assignment 4: The Earth’s magnetosphere
Due Thursday, April 28
1. In the lecture, I make some vague suggestions that the upper atmosphere can
bounce radio signals back toward the surface at night, and that is why the Federal
Communications Commission (FCC) orders radio stations to lower their power at
night. One division of the atmosphere is called the ionosphere. Describe how
the ionosphere is the key to understanding the “bouncing” of radio waves,
especially the mechanism (how does the ionosphere do that?). Do include a full
citation of where you found this information; to make it sporting, you cannot use
Wikipedia or other electronic encyclopedia for this citation.
2. The robotic spacecraft Dawn is on a mission to explore the asteroid belt. It is
using an ion-thrust engine. Go to the Jet Propulsion Laboratory website
(jpl.nasa.gov) and determine:
• what element is the “fuel” for the ion-thrust engine
• how that element is ionized (that is, is it a thermal process? Is it a
photoionization?)
• how are these ions used to move the spacecraft
You need not give a citation for this question.
3. In what three ways does the solar wind differ from winds on Earth? Hint:
consider composition, energy source and speed.
4. Are the Van Allen radiation belts a good thing or a bad thing for life on the
surface of the Earth? A good thing or a bad thing for interplanetary astronauts?
5. A solenoid is a device that utilizes Maxwell’s Equations. Draw one of these
devices (you can copy one off the Web or a book – please give a complete citation)
that shows the electric current and the resulting magnetic field (label stuff,
so I know what you’re trying to draw).