Module : The Sun’s Atmosphere
Overview:
In this lab you will study different layers in the solar atmosphere and how sunspots affect
the layers of the Sun’s atmosphere.
Sec. 1 Introduction
In this lab you will study different layers in the solar atmosphere and how sunspots affect
the layers of the Sun’s atmosphere. Sunspots are connected to the activity of the sun. This
activity can disrupt communication satellites and the power grid of cities on Earth. You
can study different layers of the sun’s atmosphere by observing it at different
wavelengths.
Sec. 2 The Solar Atmosphere
On Figure 7.1 you see a cross-section diagram of the sun. The giant hydrogen and helium
gas sphere that makes up the sun has stayed the same size and surface temperature
through the Earth’s history. For this to be the case, the core gas of the sun must be
extremely hot and dense (over 10 million Kelvin and over one hundred times that of
water) in order for the central gas pressure to balance the tremendous weight of the
overlying layers (over 300,000 times the mass of the Earth). However, the hot ~6000 K
surface of the sun is continually radiating energy into space which must be replaced if the
sun is to remain in equilibrium. Happily for us, the hot dense core conditions cause the
fusion of hydrogen atoms into helium atoms with a concurrent release of energy.
Gradually, energy released through fusion makes its way to the surface through the
radiative and convective envelopes.
Module Question 1. Going from the core toward the outside of the Sun, the weight of
the overlying layers of the Sun is less and less. For the Sun to be in equilibrium, the
density and temperature must _______ going outward.
a) decrease
b) increase
c) stay the same.
What we are interested in the three layers of the sun’s atmosphere: the photosphere, the
chromosphere, and the corona.
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Figure 1 Diagram showing the layers of the sun's atmosphere, core and convection
regions.
Sec. 2a The Photosphere
The photosphere is the visible surface of the Sun that we are most familiar with. Since the
Sun is a ball of gas, this is not a solid surface but is actually a layer about 100 km thick
(very, very, thin compared to the 700,000 km radius of the Sun). A number of visual
features can be observed in the photosphere including dark sunspots, the bright faculae,
and granules. The sunspots are clear in the Figure 7.2 image. Some faculae may be
visible near the right edge as slightly brighter white light regions on a computer screen.
The temperature decreases going upward through the photosphere as shown by the
decrease in brightness of the Figure 7.2 image toward the edge.
Sunspots appear as dark spots on the surface of the Sun. Temperatures in the dark centers
of sunspots drop to about 3700 K (compared to 5700 K for the surrounding photosphere).
They typically last for several days, although very large ones may live for several weeks.
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Figure 2 White light image of the 5700 K photosphere, the visible surface of the Sun.
Source: http://science.msfc.nasa.gov/ssl/pad/solar/surface.htm
Galileo was the first to observe sunspots in the Sun’s photosphere, making beautiful
drawings of the sun’s disk over a long sequence of days in 1613 as shown in Figure 7.13.
These are shown in movie form in a sequence at the link in the Figure 7.3 caption. Some
are given individually in larger form in Figure 7.10.
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Figure 3 Above: A drawing of sunspots by Galileo. A sequence of drawings by Galileo
made with his telescope shown as a movie on the “Galileo Project” website below.
http://galileo.rice.edu/sci/observations/sunspot_drawings.html
Under extremely good atmospheric conditions or from space, the photosphere is revealed
to not be a perfectly smooth luminous surface. Instead, it shows a mottled “granular”
appearance. These granules are small (about 1000 km across) cellular features that cover
the entire Sun except for those areas covered by sunspots. These features are the tops of
convection cells where hot fluid rises up from the interior in the bright areas, spreads out
across the surface, cools and then sinks inward along the dark lanes. Individual granules
last for only about 20 minutes.
Figure 4 White light image of the sun showing granulation. Note that cells are about
1000 km in size or about 500 miles. SOURCE:
http://science.msfc.nasa.gov/ssl/pad/solar/images/granules.jpg
Module Question 2. The granulation in the sun’s photosphere represents
a) areas where nuclear fusion occurs
b) sunspots
c) top of convection layer
Sec. 2b The Chromosphere
The chromosphere is an irregular layer above the photosphere where the temperature
rises from the low of 4500 Kelvin reached at the top of the photosphere. At these higher
temperatures hydrogen emits light that gives off a reddish color (Hydrogen-alpha
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emission). This colorful emission can be seen in prominences that project above the limb
of the sun during total solar eclipses as shown in Figure 7.5a. This is what gives the
chromosphere its name (color-sphere). Earlier we described how the sun has an
absorption line spectrum created when thin gas above the photosphere absorbs light at
certain wavelengths. This thin gas re-emits the light at the same wavelengths but in
random directions, resulting in a great decrease in the sunlight intensity upward. During
the eclipse, we see the thin gas above the photosphere against the dark background of
space. The pink glow of the prominences represents the pink line we saw earlier in our
emission line tube experiments. Figure 7.5b shows the eclipse but with a grating in front
of the camera lens. We see multiple images of the chromosphere ring with each
corresponding to major absorption lines of the solar photosphere spectrum.
Figure 5a Total solar eclipse revealing the chromosphere peeking out from the edge of
the Moon. Also note pink prominences stretching beyond edge of the Moon.
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Figure 5b Total solar eclipse revealing the chromosphere peeking out from the edge of
the Moon. The eclipse is photographed through a grating like our diffraction grating
glasses. The emission line spectrum of the chromosphere against the dark background of
space is seen.
When the Sun is viewed through a spectrograph or a filter that isolates the Hydrogenalpha (H-alpha) emission, a wealth of new features can be seen as shown in Figure 7.6a
and 7.6b. This filter reveals the randomly re-emitted light from the chromosphere above
the photosphere. The most important of these are the plages and filaments. Filaments
are dark, thread-like features seen in the red light of hydrogen (H-alpha). These are
dense, somewhat cooler, clouds of material that are suspended above the solar surface by
loops of magnetic field. Plages (PLAH-zh), the French word for beach, are bright patches
surrounding sunspots that are best seen in Hydrogen-alpha. Plages are also associated
with concentrations of magnetic fields and form a part of the network of bright emissions
that characterize the chromosphere. Similar filter photos can be made at calcium
wavelengths. Figure 7.6b shows a pair of images taken at the same time. The left is of
the photosphere at white light wavelengths. The right is a black and white display of an
H-alpha filter photo. The filaments are clearer in the B&W photo. When seen against
the dark background of space near the edge, the filaments are bright.
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Figure 6a Emission line filter photo of the sun. H-alpha.
http://science.msfc.nasa.gov/ssl/pad/solar/chromos.htm
Figure 6b White light photograph of sun compared to H-alpha photo.
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Module Question 3. In a white light photo of the sun, sunspots look _____ than the rest
of the photosphere. In an H-alpha filter photo taken at the same time, the general regions
of the sunspots appear ______.
a) light; light
b) dark; dark
c) dark; light
Sec. 2c The Corona
The corona is the sun's outer atmosphere. As shown in Figure 7.7, it is visible during total
eclipses of the Sun as a pearly white crown surrounding the sun. The true nature of the
corona remained a mystery until the 1930s. when emission lines in the spectrum were
found to match iron and other elements with many electrons torn away i.e. highly
ionized. The spectrum of the corona is shown in Figure 7.8. The high degrees of
ionization indicated an extremely high temperature. It was determined that the coronal
gases are super-heated to temperatures greater than 1,000,000ºC (1,800,000ºF). The
exact process of this paradoxical increase of heat with height is still under study.
Figure 7. The corona in visible light. An artificial eclipse is created by obscuring the sun
by a disk.
SOURCE: http://science.msfc.nasa.gov/ssl/pad/solar/corona.htm
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Figure 8 The UV emission line spectrum of the sun showing lines for iron with nine
electrons removed (FeX).. The pearly glow of the corona is seen as the faint continuous
spectrum plus the emission lines. Above a photo of the spectrum is shown. Note the
637.4 nm (6374 Angstrom) line of high ionized iron (Fe X).
As shown in the visual Figure 7 and the x-ray Figure 9, the corona displays a variety of
features including streamers, plumes, and loops. Coronal loops are found around
sunspots and in active regions. These structures are associated with the closed magnetic
field lines that connect magnetic regions on the solar surface. Streamers project outward
from the Sun's north and south poles. We often find bright areas at the base of these
features that are associated with small magnetic regions on the solar surface.
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Figure 9 The corona in x rays. The dark disk added beneath the x-ray image is the size
of the photosphere.
SOURCE: http://science.msfc.nasa.gov/ssl/pad/solar/images/Yohkoh_920508.jpg
Module Question 4. For the view of the corona shown by an x-ray telescope, is the
photosphere bright or dark in x-rays? It is _____. The 6000 K photosphere ___(is; is not)
hot enough to emit x-rays.
a) bright in x-rays; is not hot enough to emit x-rays
b) dark in x-rays; is not hot enough to emit x-rays
c) bright in x-rays; is hot enough to emit x-rays
d) dark in x-rays; is hot enough to emit x-rays
Examining Figure 7 , “The solar corona in visible light,” there are prominences at
about 2 o’clock, 5 o’clock and 9 o’clock.around the edge of the sun as a “clock face.”
Note the coronal streamers extending from these areas (which also are commonly sunspot
sites). The remaining major streamer from 11 o’clock may have come from a sunspot
region beyond the edge of the disk.
Now that we have discussed the three major layers of the sun’s atmosphere, see if you
can answer the following three questions. Pick the best answer.
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Module Question 5. The photosphere has a temperature of about _____ and shows
________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements.
Module Question 6. The chromosphere has a temperature of about _____ and shows
bright ________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements
Module Question 7. The corona has a temperature of about _____ and shows ________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements.
.
Sec. 3 Sunspots
We can use sunspots to calculate the rotational period of the sun. Think of them as
markers on a wheel to see how fast it is turning. One way is to count how many days it
takes for a sunspot group to go from one side of the sun to the middle, and then multiply
this number by four. The results confirm ideas about the interior of the sun and even give
basic information about how the planets and the sun may have formed.
As you can see in Galileo’s observations, Figure 3 earlier and in Figure 7.10 below,
sunspots appear to move across the disk from the upper left to the lower right showing
the sun’s rotation. Galileo timed the motion to get the rotation period of the Sun. For
example, spot A appears on the upper left edge on July 1 and reaches the middle on July
7 From the edge to the middle is ¼ of a rotation period, July 7 - July 1 = 6 days. The
total rotation period is thus about 4x 6 days or 24 days.
Figure 10 Below: A partial sequence of drawings by Galileo made with his telescope.
Dates and marked spots are given below each drawing. From Galileo project website.
http://galileo.rice.edu/sci/observations/sunspot_drawings.html
Go to this site in your browser or “control click” on this text. Click on the animate links
to see the Sun’s rotation, the tilted orientation of the Sun’s equator and the spot
distribution relative to the equator.
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July 1 B approaching middle and A just appearing at edge.
July 2 B at middle and A just away from upper left edge.
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July 3. B past the middle and A between upper edge and middle.
July 5 A approaching middle and B well past
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July 7 A at middle and B very near edge.
July 8 B at edge. A past middle.
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Figure 10 Above: A sequence of drawings by Galileo made with his telescope. From
Galileo project website. http://galileo.rice.edu/sci/observations/sunspot_drawings.html
Now do your own rotation calculation in the following module question.
Module Question 8. On July 2, 1613, a sunspot Galileo designated as “spot B” reached
the middle of the disk. On July 8, 1613 it reached the lower right edge. Which answer
below gives the proper dates and calculation of the rotation period of the sun?
a) (1613-1613)x (1/4) = 0 for the sun’s rotation period
b) (July 8 –July 2)x(1/4) = 1.5 days for the sun’s rotation period
c) (July 8 – July 2)x 4 = 24 days for the sun’s rotation period
d) July 8 –July 2 = 6 day rotation period
The Sun's rotation axis is tilted by about 7.25 degrees from the axis of the Earth's orbit so
we see more of the Sun's north pole in September of each year and more of its south pole
in March. Galileo’s observations were made in June/July so the pole is in the sky plane
of the paper, neither tilted toward or away from Earth.
As shown in the upper half of Figure 11 following this paragraph, Earth rotates eastward
or directly. As seen in Figure 11 lower right, you can represent this by holding your right
hand in a fist with the upward pointing thumb representing the Earth’s north pole and the
curled fingers the “direct” direction of rotation. As shown in the lower left side, your left
hand and the upward thumb pointing north would be the opposite “retrograde” direction
of rotation. Going back to the lower right, if we again let our thumb represent north, then
the right hand fingers also curve in the direction of the Earth’s orbital motion around the
sun. So, it is interesting that the very tiny Earth turns in the same way as its 10,000 times
larger orbit.
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Figure 11 above: The sun’s rotation sense (black arrow) relative to Earth’s orbit
sense (red arrows) and Earth rotation sense. (lavender arrows)
Now what about the sun’s rotation relative to Earth’s rotation and also Earth’s orbital
motion? Referring to the bottom of Figure 11, go through this procedure below to answer
the module question below. North is toward the upper right in Galileo’s sketches and the
rotational motion of the spots is from the upper left to the lower right. Hold out your left
and right fists with the thumbs pointing to upper right. The fingers of which hand best
represent the direction of the sun spot rotational motion (from upper left to lower right)?
______(choose either left hand retrograde or right hand direct). The direction of the
sun’s rotation is thus _____ (choose either retrograde or left hand; direct or right hand)..
Module Question 9. The rotation of the sun is in the ________sense as Earth’s direct
rotation and in the _________sense as Earth’s direct orbital motion.
a) same; same
b) same; opposite
c) opposite; same
d) opposite; opposite
The comparative senses of Earth’s rotation and its orbital motion along with the sun’s
rotation support the solar nebula idea for the formation of our solar system. We do not
have time to go into details here but we refer the student to the ay101 lecture course
module on the Solar System.
Galileo’s drawings give a good representation of the distribution of sunspots over the
disk of the sun. Running the Figure 7.3 movie of his drawings and a more modern
sunspot images Figure 7.10. Figure 7.11 and Figure 7.12, you can see how sunspots are
distributed over the sun’s disk to answer the following question.
Module Question 10. On the sun’s disk as seen on the sky, sunspots are distributed
a) randomly over the disk
b) only near the poles
c) exactly on the equator only
d) in bands on each side of the equator
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• Figures 7.11 and 7.12Differential roation, origin of sunspot pairs
Figure
12 cycle.
Differential rotation, origin of sunspot pairs and cycle
and
As shown in Figure 12 upper left, lower latitudes of the sun rotate faster than the higher
ones (this is called differential rotation). The gases of the sun are somewhat ionized so
that magnetic fields and the gas must move together and the gas preferentially flows
along field lines. In the next section, we will discuss magnetic fields and the sunspot
cycle. It will be helpful to refer back to Figure 7.12 while reading this section.
Sec. 3b The Sunspot Cycle.
Every few years the sun undergoes a period of activity called the "solar maximum",
followed by a period of quiet called the "solar minimum". During the solar maximum
there are many sunspots, solar flares, and coronal mass ejections, CME’s7.3 c Sunspots
and Magnetic Fields on the Sun. On this web page you will find the current and past
behavior of the sun. spaceweather.com.
In this section, we will see how the magnetic fields of the sun are related to sunspots. .
The sunspot cycle also affects the orientation of the magnetic fields in the sun. To study
this we use magnetograms, images of the magnetic fields. Sunspots typically come in
pairs: one with a positive magnetic pole (white) and another with a negative pole (black).
The orientation of these sunspots in one hemisphere might be positive in the west and
negative in the east. However, for the other hemisphere it might be negative in the west
and positive in the east. What happens to these orientations over the course of a solar
cycle?
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Figure 13 below shows the number of sunspots from the invention of the telescope to
2007. Estimate the length of years in a sunspot cycle by counting the number of number
peaks over a long interval of time (say 1900 through 2000) and dividing this into the time
interval.
Module Question 11. Which approximate number below is closest to the number of
years in the sunspot cycle.
a) 1000 yr
b) 100 yr
c) 10 yr
d) 1 yr
In Figure 13,examine the years 1650 to 1720 and note the number of sunspots during that
time. There is evidence that the number during that time correlates with unusually cold
weather in Europe during the same period. The possibility of a connection between
weather and sunspots is intriguing.
Module Question 12. During what period of time since the invention of the telescope
were there hardly any sunspots at all?
a) 1850-1900
b) 1750-1800
c) 1650-1700
d)Wrong! Spots were frequent during the whole time.
Figure 13 Graph of sunspot number from invention of the telescope to 2007.
Figure 14 shows the most recent part of the sunspot cycle in detail. We can see that we
are just passing a minimum number with exciting sunspot times ahead
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Figure 14 shows the most recent part of the sunspot cycle in detail.
It is easy to look at pictures of features like sunspots and think of them as just on the
scale of the photograph. It also easy to think of them as simply darker, cooler regions on
the sun. The more general term, active region, conveys the idea of a range of
manifestations. The largest sunspot group of the past ten years crossed the surface of the
Sun late March of 2001 (Figure 7.15). The group was designated Active Region 9393.
Note the change in appearance going from visual to UV to x ray.
The Earth is about 15,000 km in diameter or 1/100 the 1,500,000 km diameter of the sun.
Use the top frame of Figure 15 above to estimate the size of the largest spot in the March
29, 2001 Active region 9393 compared to the earth. Use the km scale on the figure to
estimate the spot size in km. Then divide this size by the earth’s diameter to get the size
in terms of the Earth’s size. Now you should be able to answer the following module
question;
Module Question 13 The largest sunspots in groups such as the one we examined in
Module 7 are about six times the size of_____
a) The University of Alabama football stadium
b) Texas
c) North America
d) the Earth
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e) the sun.
Figure 15. Top frame: A visual photosphere image of the largest sunspot group of the
past ten years in March 29 of 2001. The group (designated Active Region 9393) is in the
center of all frames. extreme ultraviolet, and x-ray light. All were taken on March 29,
The middle panel is in ultraviolet (highest level of chromosphere). Bottom panel is in Xrays (corona).
Sunspots typically come in magnetic pairs. The active region’s magnetic field structure
is shown in Figure 16. Sunspots with positive polarity (white) are next to sunspots of
negative polarity (black). The meaning of Figure 7.16 is shown in Figure 17 which
shows a three dimensional view of magnetic fields in a sunspot pair. The left side of
Figure 17 is a filter image of the chromosphere immediately above a sunspot pair. The
gas is partially ionized and follows the field lines like iron filings dropped near a magnet.
The lines indicate the pair of spots have opposite N and S poles. A schematic magnet is
shown below the photosphere to get this point across.
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Figure 16 A magnetograph of the same region 9393. Areas that are strongly white or
strongly black correspond to strong magnetic fields. Grey areas correspond to weak
magnetic fields. Note the opposite polarities of leading (right) and trailing members of
sunspot pairs.
Figure 17. Three dimensional view of magnetic fields of a sunspot pair. Left is a filter
image of the chromosphere immediately above a sunspot pair. The pair of spots have
opposite N and S poles. A schematic magnet is shown below the photosphere to get this
point across..
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The magnetic polarities of pairs change with the cycle and the hemisphere.
Figure 18 shows magnetograms of July 18, 1990 and July 18, 2000, at one
number maximum then the next cycle’s number maximum.
Compare the 1990 top hemisphere magnetic polarities to the polarities in the
1990 lower southern hemisphere. Sunspots with positive polarity (white) are
next to sunspots of negative polarity (black). The leading (right hand pair
members are of opposite polarity to the trailing members). This leading
trailing polarity is opposite for sunspots in the southern hemisphere of the sun
compared to sunspots in the northern hemisphere.
Examining the northern hemisphere of 1990 to the top northern hemisphere of
2000, we see that going from one cycle to the next, the leading trailing
polarities are opposite.
Figure 18 Magnetograms of July 18, 1990 & July 18, 2000, Black & white
indicate opposite magnetic polarities. Note that the pair magnetic polarities
are reversed in upper north hemisphere after one sunspot number cycle.
Module Question 14. The time for repetition of sunspot number maximum and
pair magnetic polarities to repeat is ___ years. Pick the best answer.
a) 11 years
b) 22 years
c) 33 years.
d) 44 years.
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Sec. 4 An Incident on the Sun
Earth's magnetic field senses the solar wind, streams of ionized electrons and atomic
nuclei from the sun. Some major terrestrial results of solar variations are the aurora and
geomagnetic storms. The aurora is a dynamic and visually delicate manifestation of
solar-induced geomagnetic storms. The solar wind energizes electrons and ions in the
magnetosphere. These particles usually enter Earth's upper atmosphere near the polar
regions. When the particles strike the molecules and atoms of the thin, high atmosphere,
some of them start to glow in different colors.
Coronal mass ejections (or CMEs) are huge bubbles of gas threaded with magnetic field
lines that are ejected from the Sun over the course of several hours. CMEs are best
observed with a coronagraph which produces an artificial eclipse of the Sun by placing an
"occulting disk" over the image of the Sun. CMEs disrupt the flow of the solar wind and
produce disturbances on the Earth.
The web site below has movies at various wavelengths of a spectacular October 25, 2002
CME. Click on each of the images to see the movie. This CME was pointed sideways to
the direction of the Earth enhancing visibility of the processes in the ejection. You can
see in the image 3 movie that the CME starts off as a magnetic field arch between two
sunspots like Figure 7.17 above. The arch suddenly expands and is ejected from the sun.
The descriptive text in this website gives a good description of CMEs.
Figure 19. October 25, 2002 CME. H-alpha filter view. This CME was pointed sideways
to the direction of the Earth enhancing visibility of the processes in the ejection. Movies
and other images are at http://www.gsfc.nasa.gov/topstory/20021030solar.html
•
When a CME cloud of solar material and magnetic fields is ejected toward Earth,
we may have a geomagnetic storm. These storms can disrupt power grids. As an
example, on July 20th 2002, a powerful solar flare erupted from a location just
behind the Sun's southeastern limb. The explosion caused a radio blackout across
North America and the Pacific Ocean.
http://www.gsfc.nasa.gov/topstory/2002/20020724grandslam.html
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Sun’s Atmosphere Questions
1. Going from the core toward the outside of the Sun, the weight of the overlying layers
of the Sun is less and less. For the Sun to be in equilibrium, the density and temperature
must _______ going outward.
a)decrease
b)increase
c)stay the same.
2. The granulation in the sun’s photosphere represents
a)areas where nuclear fusion occurs
b)sunspots
c)top of convection layer
3. In a white light photo of the sun, sunspots look _____ than the rest of the photosphere.
In an H-alpha filter photo taken at the same time, the general regions of the sunspots
appear ______.
a)light; light
b)dark; dark
c)dark; light
4. For the view of the corona shown by an x-ray telescope, is the photosphere bright or
dark in x-rays? It is _____. The 6000 K photosphere _____ hot enough to emit x-rays.
a)bright in x-rays; is not hot enough to emit x-rays
b)dark in x-rays; is not hot enough to emit x-rays
c)bright in x-rays; is hot enough to emit x-rays
d)dark in x-rays; is hot enough to emit x-rays
5. The photosphere has a temperature of about _____ and shows ________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements.
6. The chromosphere has a temperature of about _____ and shows ________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements
7. The corona has a temperature of about _____ and shows ________
a) 500 K; sunspots
b) 5000 K; sunspots
c) 5000 K; plages
d) 1,000,000K; emission lines of highly ionized elements.
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8. On July 2, 1613, a sunspot Galileo designated as “spot B” reached the middle of the
disk. On July 8, 1613 it reached the lower right edge. Which answer below gives the
proper dates and calculation of the rotation period of the sun?
a) (1613-1613)x (1/4) = 0 for the sun’s rotation period
b) (July 8 –July 2)x(1/4) = 1.5 days for the sun’s rotation period
c) (July 8 – July 2)x 4 = 24 days for the sun’s rotation period
d) July 8 –July 2 = 6 day rotation period
9. The rotation of the sun is in the ________sense as Earth’s direct rotation and in the
_________sense as Earth’s direct orbital motion.
a) same; same
b) same; opposite
c) opposite; same
d) opposite; opposite
10. On the sun’s disk as seen on the sky, sunspots are distributed
a) randomly over the disk
b) only near the poles
c) exactly on the equator only
d) in bands on each side of the equator
11. Which number below is closest to the number of years in the sunspot cycle.
a) 1000 yr
b) 100 yr
c) 10 yr
d) 1 yr
12. During what period since the invention of the telescope were there hardly any
sunspots?
a) 1850-1900
b) 1750-1800
c) 1650-1700
d)Wrong! Spots were frequent during the whole time.
13 The largest sunspots are a size about six times the size of_____
a) The University of Alabama football stadium
b) Texas
c) North America
d) the Earth
e) the sun.
14. The time for repetition of sunspot number maximum and pair magnetic polarities to
repeat is ___ years. Pick the best answer.
a) 11 years
b) 22 years
c) 33 years.
d) 44 years.
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