Student Worksheet Name: ____________________________________
Date: ________________________ Period: ______
Coronal Mass Ejections: Satellites in Peril
Background:
For nearly 30 years it was thought that all solar energetic particles (SEPs) were accelerated in solar flares and that they could somehow diffuse across magnetic field lines to distant longitudes by a mysterious mechanism known only as "coronal diffusion." During recent years, 1975 to present, a new class of observations has revealed two distinct populations of SEPs, with completely different origins. It has become clear that the largest and most energetic particle events on Earth are associated with shock waves driven into interplanetary space by coronal mass ejections (CMEs).
Scientists believe that CMEs erupt from the Sun’s outer corona as a huge bubble of plasma. The energy supply needed to produce the violent explosion of a CME is believed to come from the Sun’s complicated magnetic fields that burst from its interior. The larger and higher magnetic fields are believed to hold down the newer, smaller fields emerging from the surface, restraining the plasma and the magnetic fields trying to rise to the corona. Tremendous energy builds up and as heat is added to the bubble, it begins to accelerate, soon escaping the Sun’s gravitational field.
A CME speeds across space at great velocities, carrying a ten billion ton bubble of plasma into the solar system.The energy in this bubble of plasma is comparable to the energy combined in one hundred hurricanes.
As the CME plows through space, it creates a shock wave that accelerates particles to dangerously high speeds, bombarding planets, asteroids, and other objects with radiation and plasma. If the CME erupts on the side of the Sun facing the Earth, and our orbit intersects the path of the plasma cloud, the results can be both spectacular (auroras) and dangerous to some of our modern technologies.
Part One: Throughout the procedure there are URLs for specific sites on the Internet that contain the information you need to complete each set of questions.
When a CME dumps 1500 Gigawatts of electricity (double the electric generating power of the entire United States) into the atmosphere, big changes occur which can wreck havoc on satellites. As a society we have come to depend on satellites, electrical power, and radio communication- all of which are affected by these electric and magnetic forces. Since so much information is relayed by satellites- from ATM machines and broadcast signals to disaster warning systems- CMEs pose a technological hazard to our civilization.
Procedures:
Step 1. Visit Basic Facts About Space to complete the questions:
•Click on Sun-Earth System
•Select #5- Mass Ejections
Describe a mass coronal ejection. Approximately how fast does it move through space? How much energy is stored in a CME? Should a CME be a concern for us here on Earth? Why or why not?
Step 2. Visit How Storms Build in Space to complete the questions:
•Click on Solar Wind Disturbances
About how long does it take for a solar wind disturbance to affect the Earth? Name the two largest space weather disturbances that affect the Earth. From which area of the Sun do CMEs come?
List the effects they have on the Earth. Revisit the last 2 questions in Step 1. Is your answer the same?
Step 3. Visit the Effects at Earth of Space Weather Events to complete the questions:
•List the effects of space weather events on Earth
•Click on Satellite Damage and Difficulties
•Select Major Types of Satellites, Orbits and Uses
Identify the different types of satellite orbits. List at least three uses of satellites in each type of orbit. Name two examples of satellites in each orbit. What is the advantage(s) and/or disadvantage(s) of having a satellite in a particular orbit?
Step 4. Visit Satellites in Orbit to complete the questions:
Satellites in orbit are described as falling with the Earth. If this is true, how can they stay up there in the atmosphere?
Step 5. Visit Atmospheric Drag to complete the questions:
Describe an effect that the Sun’s increased activity has on the Earth’s atmosphere?
How does the additional particles, pushed ahead of the arrival of a CME, affect satellites in orbit below 2000 km in the Earth’s atmosphere? What does the red color on the Earth represent?
Step 6. Visit Atmospheric Drag and Lost Objects in Orbit to complete the questions:
You read about the effect of atmospheric drag on satellites in the previous lesson. In March 1989, a series of solar flares and CMEs produced a severe magnetic storm.
Describe the effect a magnetic storm has on atmospheric drag and satellites.
Examine the graph closely. Briefly explain the data represented on the graph. What conclusions can you make about CMEs and their effects on satellites based on the data?
Step 7. Visit Satellite Orbit to complete the questions:
Now you will visit a site that demonstrates what happened to the orbits of four satellites during a CME event which occurred from 18 May 1996 to 22 May 1996. Scroll down halfway so that you can see both images at the same time. How does the effect of this CME on these satellites compare to the conclusions you made in Step 6?
Part Two: In part one you investigated the effects of CMEs and other forces on satellite orbits. In part two of this investigation you will use NIH Image to take measurements for calculating the velocity of a CME. Once you have calculated the average velocity, you will determine the day that an observed CME may reach the Earth’s orbit.
In order to process your newly acquired images, you need to convert the images from JPG or GIF to TIFF. To do this, you must download an image format converter program. You can get programs for either the MAC or PC platform from the Internet. Your teacher will provide the URL for this web site.
After you have downloaded the installer (follow the instructions given), you can convert images by starting the graphic conversion program. Select OPEN from the FILE pull-down menu. Select SAVE AS from the EDIT pull-down menu and change the file type of any graphic. Remember that you need to use GIF or JPG when viewing a graphic with a WWW browser -- use TIFF when you want to view an image using an image processing program.
Procedure:
Part A - Downloading, Saving, and Converting Images from the Internet
Any image that you find on the Internet's World-Wide-Web (WWW) using Netscape or MS Internet Explorer can be saved on your hard drive or in a folder on your desktop for analysis.
Step 1.Start your WWW browser (Netscape or MS Internet Explorer, for example) and click here for the 15 January 1996 CME.
Step 2.To save an image to your hard drive or desktop folder, position the mouse over the image and hold down the button for a couple of seconds (use the right button if you have more than one button on your mouse).
Step 3. From the pop-up menu, select SAVE THIS IMAGE AS. This will give you an option about what to call the image and where to save it. Choose a different name and location if you like.
Step 4.The image is now saved and you can open it with your WWW browser or with an image conversion program. With these programs, you can alter the image's size, color, or even add text to the image.
Step 5. Start your graphics conversion program by double clicking on its icon. From the FILE menu, select OPEN. Find the image that you downloaded and open it using this converter program.
Step 6. From the FILE menu, select SAVE AS. Click and hold on the FORMAT BOX. A pop-up menu will appear. Select "TIFF". Then click SAVE. Close your graphics converter program. You are now ready to begin image processing.
Part B - Using Image Processing Software for Scaling and Measurement
Step 1. Start your image processing software program. Using the FILE pull-down menu, select OPEN. Select and open the TIFF image that you converted in Part A.
Step 2.Your first task is to calibrate the image (tell the computer the scale of the image). As you are looking at the first image in the CME sequence, you will notice the white colored ring of the coronagraph. This white ring represents the approximate size and location of the sun. The black disc is the part of the coronagraph that blocks the Sun’s surface and inner corona.
Step 3. Using the segment tool/select line tool (fifth from the top on the right), draw a line across the diameter of the white ring since it represents the diameter of the Sun.
Step 4. Under the ANALYZE menu, select SET SCALE. Note that the computer has already recorded the number of pixels (picture elements) along the line you drew. First, change the UNITS to KILOMETERS. Second, enter in the known diameter, 1.4e6 (1.4 million km). Click OK. Your image is now calibrated and you are ready to measure CMEs.
Step 5. Click on the magnifying glass in the upper left of the tool bar. Use it to focus on the CME by clicking on it. The software will remember the scale of the image so you can get as close as you need to make a good measurement. To un-zoom, double click the magnifying icon in the tool box.
Step 6. Move the segment tool (select lines) to the edge of the black disc and carefully draw a from the edge of the disk to the edge of the CME. From the ANALYZE menu, select MEASURE.
Step 7. From the ANALYZE menu, select SHOW RESULTS. ( Note: If you’re using NIH Image to process your image, the window in the lower left corner of your computer screen will have the results of your measurements.)
| Universal Time |
Time Interval in seconds |
Position in kilometers |
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Step 8. Record the universal time (listed on each image in the sequence), of each image in the chart below. Then write in the time interval and the measurement of the CME in kilometers. (The times given are universal time or UT and written as military time. For example, 06:00 is 6:00 AM, 15:00 is 3:00 PM, and 18:23 is 6:23 PM. Eastern standard time (EST) is five hours earlier than UT.)
Step 9. Open the next image in the CME sequence and repeat Steps 5 through 8.
Step 10. Now that you have the distance from the Sun and the time, you can calculate the instantaneous velocity for a given time. On the graph, plot the UT on the x-axis and the position in kilometers on the y-axis. (Graph on next page)
Step 11. Is there a linear relationship between the UT and the position of the CME? Cite evidence in the graph to support your response.
Step 12. Choose a point on the graph; preferably not the first point. Draw a straight line that is tangent to the curve at that point. Draw the line long enough so that it intercepts the graph at two points; one point before the point on the curve, the other point after the point on the curve.
Step 13. Now find the slope of that line. The slope of the tangent is called the instantaneous velocity at that point.
Use the formula: slope = rise = Æd; Æd is the difference between the distances
- runÆt Æt is the difference in time in seconds
Record your answer: ____________ km/sec
Step 14. Choose two other points, one point near the middle of the curve and one point near the end. Repeat Step 13 for each of the two additional points. Find the slope of each line and record your answers: ________________ km/sec; __________________ km/sec
Step 15. Now find the average for the three instantaneous velocities. Record your answer:
__________________ km/sec
Step 16. What is the date at which the CME erupted from the Sun’s corona? Using your calculated velocity, determine the expected date when the CME is likely to reach the Earth’s atmosphere.
