Download Testing

Dr Dash will be on travel for the
next two weeks (off to Africa).
We will have a guest lecturer and
Justin will be available to answer
questions.
Homework 9 and 10 will become
due during this time period.
Sunspots …
Regions with strong
magnetic fields
Cooler than other
parts of the Sun’s
surface (4,000 K) and
thus not as bright as
their surroundings.
Recall: Cooler objects
emit less radiation per
surface area.
Loops of bright gas often connect sunspot
pairs, leading one spot to have one magnetic
polarity and the other the opposite polarity.
Magnetically Linked Spots
solar flare: a
violent explosion
in the sun’s
atmosphere
Magnetic activity
causes solar
flares that send
bursts of X-rays
and charged
particles into
space.
An active region on the Sun that produced a powerful flare shown over a period of about four
hours. The glowing gas flowing around the relatively stable magnetic field loops above the Sun's
photosphere has a temperature of over ten million degrees Celsius. These flows occurred after
violently unstable magnetic reconnection events above the Sun produced the flare.
Magnetic activity
also causes
solar
prominences
that erupt high
above the Sun’s
surface.
The corona
appears bright in
X-ray photos in
places where
magnetic fields
trap hot gas.
Active Sun: Coronal Loops
• Coronal loops are
tracing magnetic field
lines in the corona
• Coronal loops are
rooted in the
photosphere, one end
with positive polarity,
and the other end
negative polarity
Coronal mass
ejections send
bursts of
energetic
charged
particles out
through the solar
system.
How does solar activity affect humans?
An active region on the Sun that produced a powerful flare shown over a period of about four
hours. The glowing gas flowing around the relatively stable magnetic field loops above the Sun's
photosphere has a temperature of over ten million degrees Celsius. These flows occurred after
violently unstable magnetic reconnection events above the Sun produced the flare.
Charged particles streaming from the Sun can disrupt electrical
power grids, disable communications satellites, and cause
aurora (“northern and southern lights”).
How does solar activity vary with
time?
The number of sunspots rises and falls in 11-year cycles.
The sun rotates faster at its equator than away from the
equator.
The sunspot cycle arises from the winding and twisting of the
Sun’s magnetic field produced by this differential rotation.
Moving outward from
the Sun, we come to…
The Terrestrial Planets
Mercury
Venus
Earth
Mars
Mercury
• Made of metal and rock; large iron core
• Desolate, cratered; long, tall, steep cliffs
• Very hot and very cold: 425°C (day), –170°C (night)
Venus
• Nearly identical in size to Earth; surface hidden by clouds
• Hellish conditions due to an extreme greenhouse effect:
• Even hotter than Mercury: 470°C, day and night
Earth
Earth and
Moon to scale
• An oasis of life
• The only surface liquid water in the solar system
• A surprisingly large moon
Mars
• Looks almost Earth-like, but don’t go without a spacesuit!
• Giant volcanoes, a huge canyon, polar caps, more…
• Water flowed in the distant past; could there have been life?