Source: University of Michigan site at:
http://geo.lsa.umich.edu/~crlb/COURSES/140/Lec5/Lec5.html

It is is important to note here that these numbers do not equal relative elemental abundance in the Earth’s crust. When only the crust is considered, 74% of the mass comes from oxygen and silicon (46% O and 28% Si). But the core of the Earth is known to be predominately iron and nickel. When the core, mantle, and crust are all considered we see the percentages of O and Si decrease.

The relative abundance of the elements found in the Sun are shown in the following table.

Source: University of Tennessee site at:
http://csep10.phys.utk.edu/astr162/lect/sun/composition.html

There are two main nuclear fusion cycles that occur in stars to produce energy and new elements.
Our Sun is a medium sized star with temperatures in its interior reaching 10 million degrees. In stars of this type the proton-proton (PP) cycle is the dominant fusion process. Production of the larger elements occurs in stars which are five to ten times larger than our Sun. The heavier elements up through iron and nickel are produced in stars of this size. Their dominant fusion process is the carbon-nitrogen-oxygen (CNO) cycle. Elements heavier than iron and nickel are thought to be produced when stars explode into a supernova.

As scientists conduct studies about elemental abundances in space one of the tools available to them is data from the Advanced Composition Explorer (ACE). The ACE spacecraft was launched in August of 1997 to make observations that are being used to test current theories on the creation and evolution of the galaxy and to monitor the composition of the solar wind. ACE specializes in detecting cosmic ray particles. They are atomic nuclei and electrons that possess exceedingly high energies. The nine instruments on ACE are capable of measuring a variety of characteristics of the cosmic ray particles. Some of these characteristics are: energy, charge, velocity, and mass.

A comprehensive site entitled Atomic Alchemy: Nuclear Processes, provides additional background for this investigation as well as animations of some of the processes. It can be can be accessed at: http://hyperion.advanced.org/17940/index.html

Procedure: Embedded in the procedure you will find questions that require a response. If this investigation is being done for a grade, you will need to keep a neat copy of your responses numbered according to the procedure step where the question is found.

PART ONE
1. Access the ACE Project Page at http://helios.gsfc.nasa.gov/ace/ace.html

2. Click the Online Data button.

3. Click the Browse button in the section for Online Data.

4. At this point you have a choice of which ACE data sets you want to access. Under the Flexible Browse Data Interface you will find a window which can be used to choose which days you want to access. To familiarize you with how to select the data sets we will look initially at some data showing all of the ACE data . In the window select the Browse Data All category and then click GO.

5. In the next window click on ACE Browse Daily Averages.

6. In the next window you will have options available regarding which ACE instruments you want to select, which particle you want to select, what energy ranges you want to select, and whether you want to observe logarithmic or linear plots. To begin we will look for correlation between ACE data and two well documented events that occurred on the Sun. The day corresponding to the first event was November 6, 1997. Click in the box to the right of SIS corresponding with Z > 9 9-21. This means that you will view data from the SIS instrument on ACE and will see a plot of particles detected that had an atomic number greater than 9 (heavier than fluorine) and had energies from 9-21 MeV (million electron volts) per nucleon (proton or neutron). Next to the Y-axis Scaling choose Linear. Now you are ready to plot the data set which you have selected. Under Choose Data Format click on the Retrieve data button.

7. Since the ACE data time axis is shown in terms of DOY (day of year) you will need to know that November 6, 1997 was day 310 of that year. Each block of time on the x-axis represents 25.6 days. Do you see a peak in the SIS data at a place on the graph matching day 310?

8. Close the window which shows the plot and click Reset Form.

9. Again select SIS data for Z > 9 9-21 but this time select Logarithmic rather than Linear and click on the Retrieve data button.

10. How does the logarithmic graph differ from the linear graph? Does this graph peak on day 310? What is the actual reading for the number of particles/cm²/sec? HINT : The y-axis is shown as a logarithmic plot. The 10^-8 at the bottom of the y-axis corresponds with a particle flux (rate of particle flow) of 1 X 10^-8 . The next small line (going up the) axis corresponds with 2 X 10^-8, then 3 X 10^-8, and so on. When you get to the line labeled 10^-7, the particle flux has now increased to 1 X 10 ^-7. A particle flux corresponding to this line is ten times higher than a flux corresponding with the 1 X 10^-8 found at the bottom of the chart. Each increase on the chart of one power of ten is said to be an increase in magnitude of one. For example, a flux of 10^-1 is said to be five orders of magnitude above a flux of 10^-6. (For a more complete explanation of logarithmic plots access the following link.)
http://mentor.lscf.ucsb.edu/mcdb108a/tw-lig/logarithmic-algebra.htm

11. Another solar event on record occurred during a two day period in early May of 1998 corresponding with DOY 121-122 of 1998. Use the procedure learned above to determine if the ACE data shows this event in both the linear and logarithmic graphs. What is the actual reading for the number of particles/cm²/sec for that portion of the logarithmic graph? Did this event produce a larger or smaller particle flux than the November 1997 event?

12. If you close the window which shows the plot and then click back twice on your browser you can again select which ACE data sets you want to access (as you did in step 4). For this part of the investigation go to the window under the Flexible Browse Data Interface and choose a smaller range of days to access. Click GO.

13. Take time to investigate a variety of instruments and a variety of particle types. Construct a data table which includes the following:
a. A list of days which you believe must have had energetic solar events based on peaks found in your research.

b. A list of ions or elements which seem to be unaffected by the solar energetic events (if any).

c. A list of the elements that are measured by ACE and are also found in the equations for the PP, and CNO cycles found in the accompanying Educational Brief: Fusion & Nucleosynthesis.



Extension: To access a site which has movies of solar activity go to:
http://lasco-www.nrl.navy.mil
You will need MoviePlayer with QuickTime or Sparkle software so you can view the movies.

PART TWO
1. Access the ACE Project Page at http://helios.gsfc.nasa.gov/ace/ace.html

2. Click the Online Data button.

3. Click the Browse button in the section for Online Data.

4. In the Flexible Browse Data window select the Browse Data All category and then click GO.

5. In the next window click on ACE Browse Daily Averages.

6. In the next window click in the box to the right of SWEPAM corresponding with Helium ratio. Next to the Y-axis Scaling choose Logarithmic. Now you are ready to plot the data set which you have selected. Under Choose Data Format click on the Retrieve data button.

7. This graph provides data showing the DOY vs the ratio of He⁺⁺ to H⁺ ions as measured in the solar wind. Analyze the plot and make a data table which contains the following columns: DOY, year, numerical value of the ratio, and the order of magnitude.
HINT: The order of magnitude is the exponent on the base 10 number for a given measurement. For example the number 1 X 10^-3 has an order of magnitude of -3 and is said to be five orders of magnitude above 1 X 10 ^-8_.

Include in your data table information for the three highest and the three lowest ratios that you observe. Does the number of helium and hydrogen ions seem to remain constant ? If not, what is the difference in the order of magnitudes for the high and low values?

8. Do the days with the highest ratios match up with any of the solar events which you investigated in Part One of this investigation? Justify your answer.

9. Does the helium ratio correspond with the fluxes of any of the particles measured on other ACE instruments? To determine your answer, close the window that shows the plot and then click Reset Form, and then select the following: EPAM e- 38-53, SIS H E > 10, and SWEPAM corresponding with Helium ratio. Under Choose Data Format click on the Retrieve data button. Now you have a graph which superimposes the three sets of data to be analyzed.

10. Access the data table containing information on ELEMENTAL ABUNDANCE IN THE SUN found in the Background for this investigation. Use the column labeled % by NUMBER and write down the % for helium and the % for hydrogen as shown in the table. Calculate the ratio of He to H and write down that value. Compare your calculated ratio to the ratios listed in your data table from number 7 above. Where does your calculated solar ratio fit in relation to the high and low ratios found in the ACE data for the solar wind?


Coding:

Maryland Core Learning Goals (Science): 2.1.2, 2.2.1, 4.6
National Standards (Science): Grades 9-12: B.1, D.4
National Standards (Geography): 8.2
National Standards (Mathematics): 4.3, 10.3
Technology Standards (Technology): 3a

Use information provided in the Background, the accompanying Educational Brief: Fusion & Nucleosynthesis, and information learned while doing the investigation to answer the following questions.

1. For the elements H, He, O, and Fe, compare the relative abundance (% by mass) of each as found in the Earth and in the Sun and in the solar wind. List the five most abundant elements found in each. What might account for the values which you observe?

2. Access ACE News article #27 at:
http://www.srl.caltech.edu/ACE/ACENews/ACENews27.html
a. Which element abundances (measured by the ACE/CRIS instrument) are being compared to their abundance in the solar system?

b. According to the news article are these element abundances more or less abundant than iron in the cosmic rays? Support your answer with specific numerical comparisons.

c. According to the news article how do these element abundances compare with all other elements with atomic numbers (Z) greater than 30? Support your answer with numerical comparisons.

2. As compared with the Sun and the solar wind, does the Earth seem to be representative of the matter found through the rest of the universe? Support your answer with numerical comparisons.

Feedback:
Click here to pilot this investigation.

Credits:

Daniel Hortert GESSEP Program

Bennett Seidenstein GESSEP Program

Dr. Eric R. Christian ACE Deputy Project
Scientist

Beth Jacob ACE Outreach Specialist