• Two balls have the same displacement and travel for the same length of time.
– Which ball traveled a greater distance?
– Which ball traveled at a greater speed?
– How far did the ball on the right travel?
– How fast did the balls travel if they took 5 seconds?
1m
1m
1m
1

Part I
• Read and Discuss background articles: o
Lab Details o
SuperSID Users Manual o
Radio Waves and Communications Distance (Read Sections: Sky Waves through Skip
Distances and Skip Zones)
• Consider the following questions while reading the articles o
Are there pictures that can aid in drawing the diagram? o
What are the important concepts, theories, and laws that can be used to write the introduction? o
Are any relationships or equations expressed? o
What are the independent and dependent variables?
•
Peer Reviewer: After reading, determine which group you will review and sit in on their discussion.
Part II
• Review the grading check list
• Begin drafting page one
• o
You may want to do draft work on a separate sheet of paper
Peer Reviewer: Rejoin your group and report insights from the other group.
In this laboratory exercise you will be conducting research on the propegation of radio waves. This lab is an exercise and does not represent any actual experiment that has been conducted. The data used in this lab is fictional, no instruments were used or measurements taken. The data was calculated by using approximate mathematical models for the propegation of radio waves. In no way should the data presented in this lab be used as a basis for scientific research. The only legitimate use of the data is to conduct a laboratory exercise with in the confines of an introductory science course for the investigation of radio wave propegation.
Radio waves, like visible light, are electromagnetic waves. All electromagnetic waves travel at the speed of light—approximately 300,000 km/s in a vacuum. Although the average speed of light through a material might be slightly less depending on the properties of the material. In a single material, or medium, the speed of light does not change, it remains constant. Therefore the distance a radio wave moves along its propegation path can be calculated with the constant velocity equation d = vt. In this lab you will develop a method for determining the speed of light through air using radio waves.
Experiment Details
A 10MHz radio signal was transmitted from a floating barge in the Pacific Ocean. A portable radio receiver was used to take signal strength measurements along a straight path at 50km increments. The signal included a time code to determine the travel time over the distance from the transmitter to the receiver. The distance was determined by GPS to a minimum accuracy of 10m. All measurements were taken on a clear night to provide some limited control for ionospheric conditions. It is assumed that the signal was reflected off the ionosphere at a height of 200km.

S
I
D
Society of Amateur Radio
Astronomers
http://Radio-astronomy.org
A participating project of the United
Nations International Heliophysical Year
and the International Space Weather Initia tive
Version 1.0 Latest change: 6 January 2010 DKS

SuperSID Chapter 1 - Intro
Stanford University's Solar Center has developed inexpensive space weather monitors that students can install and use at their local high schools. The instruments detect changes to the Earth’s ionosphere caused by solar flares and other disturbances.
Students "buy in" to the project by building their own antenna, a simple structure costing little and taking a few hours to assemble. Data collection and analysis is handled by a local
PC, which need not be fast or elaborat e.
Stanford provides a centralized data repository where students can exchange and discuss data. Considerable accompanying educational guides are provided with the monitors.
Two versions of the monitor exist – the original SID Monitor, distributed throughout the world for the International Heliophysical Year
1
, and SuperSID, a lower-cost, more powerful upgraded instrument being distributed through the International Space Weather
Initiative
2
. This manual describes the upgraded, SuperSID monitor.
What is a Space Weather Monitor?
Our space weather monitors measure the effects on
Earth of solar flares by tracking changes in very low frequency (VLF) radio transmissions as they bounce off Earth’s ionosphere. The VLF radio waves come from transmitters set up by various nations to communicate with their submarines. Signal strength of these VLF waves changes as the Sun affects
Earth’s ionosphere, adds ionization, and thus alters where the waves bounce. Our monitors track these changes in signal strength.
The Sun affects the Earth through two mechanisms. The first is energy. Whenever the Sun erupts with a flare, it is usually in the form of X-ray or extreme ultraviolet (EUV) energy. These X-ray and EUV waves travel at the speed of light, taking only 8 minutes to reach us here at Earth, and dramatically affect the Earth’s ionosphere.
Solar flares, seen in X-ray, as captured by the Hinode spacecraft.
Image from NASA/JAXA
1
2
United Nation’s sponsored IHY: http://ihy2007.org/ , UNBSSI program: http://ihy2007.org/ ) http://www2.nict.go.jp/y/y223/sept/ISWI/090615_SWIs.pdf
7

SuperSID Chapter 1 - Intro
The second mechanism of affecting Earth is through the impact of matter from the Sun.
Plasma, or matter in a state where electrons have been separated from the nuclei of their atoms, can also be ejected from the Sun during a flare. This “bundle of matter” is called a
Coronal Mass Ejection (CME). CMEs flow from the Sun at over 2 million kilometers per hour. Thus it would take a CME 72 hours or so to reach us. These CMEs primarily affect the
Earth’s magnetosphere and one would need a magnetometer to track changes.
CME ejection. Image from NASA/ESA SOHO
Both energy and matter emissions from the Sun affect the Earth. Our space weather monitors track only the energy form of solar activity.
What is the Ionosphere?
Energy from the Sun constantly affects the Earth’s ionosphere, the highest level of
Earth’s atmosphere, starting some 60 km above us. When solar energy strikes the ionosphere it strips off electrons from their nuclei. This process is called ionizing -- hence the name ionosphere.
T he Earth’s ionosphere begins about 60 km above the Earth’s surface.
8

SuperSID Chapter 1 - Intro
It is the free electrons in the ionosphere that have a strong influence on the propagation of radio signals. Radio frequencies of very long wavelength (very low frequency or “VLF”)
“bounce” or reflect off these free electrons in the ionosphere thus, conveniently for us, allowing radio communication over the horizon and around our curved Earth.
Radio waves bounce off the ionosphere
The ionosphere has several layers created at different altitudes and made up of different densities of ionization. Each layer has its own properties, and the existence and number of layers change daily under the influence of the Sun. During the day, the ionosphere is heavily ionized by the Sun, creating the (arbitrarily-named) D, E, and F layers. During the night hours there is no ionization caused by the Sun since it has set. However, there is some small ionization caused by cosmic rays, which creates only the higher, F layer.
Thus there is a daily cycle associated with the ionizations.
In addition to the daily fluctuations, activity on the Sun can cause dramatic sudden changes to the ionosphere. When energy from a solar flare reaches the Earth, the ionosphere becomes suddenly more ionized, thus changing the density and location of layers. With the increased ionization, the VLF signals now bounce from the lower, D layer. Hence the term “ Sudden Ionospheric Disturbance ” to describe the changes we are monitoring.
The strength of the received radio signal changes according to how much ionization has occurred, at what level of the ionosphere the VLF wave “bounces” from, and how much additional ionization the wave must penetrate on its way to or from a bounce.
9

• Read as a group the lab details from activity 1
• Review the grading check list
• Develop the experimental method o
How is the independent variable changed and measured? o
How is the dependent variable measured? o
How will the lab be controlled? o
Is there enough information for another group to repeat the lab?
• Questions to consider for this lab o
How does a radio wave interact with the ground and ionosphere? o
What is the shape of the radio wave’s path?
• What calculations must be preformed?
• Peer Reviewer: Review and grade the same group from the previous activity.
• Look over the data from the table below o
Show a sample calculation on the backside of the page o
Are there any additional calculations required to find how far the signal traveled?
Hint: what geometric shape do you think represents the radio wave’s propegation path?
• In this lab the independent variable is the distance the signal traveled while dependent variable is the time the signal takes to travel that distance. Travel times are shown below. o
Record measurements in the data table. o
Fill in the independent and dependent variable column in the data table.
Straight line Distance Between
Transmitter and Receiver (km) Travel Time (s) Signal Strength
0
50
------
------ strong weak
100
150
200
250
300
350
400
450
500
------
0.0016
------
------
0.0031
------
------
0.0038
------ none maximum none none maximum weak none maximum none
550
600
650
700
750
800
850
900
950
1000
------
0.0053
------
------
0.0083
------
------
0.0079 weak maximum none weak maximum weak weak weak maximum weak weak

• Shows the data as points on a graph
• Full range of values evenly distributed on on each axis
– Independent variable on X-axis
– Dependent variable on
Y-axis
60
50
40
30
20
10
0
0
Independent vs. Dependent
5 10 15 20
Independent Variable (Units)
25
• Make an oval around the data
• Draw a line through data that divides the oval into equal areas
• Also called
– Linear regression
– Trend line
60
50
40
30
20
10
0
0
Independent vs. Dependent
?
5 10 15
Independent Variable
20 25
1

• Outlier data points do not fall into the general grouping of data
• Excluding outliers from analysis must be justified in the conclusion with specific evidence
60
50
40
30
20
10
0
0
Independent vs. Dependent
5 10 15
Independent Variable
20 25
• A linear relationship shows a proportional change in the dependent variable for each change in the independent variable
• The proportional change is the slope
• y = mx + b slope(m)
60
50
40
30
20
10
0
0
Independent vs. Dependent
5 10 15
Independent Variable
20 25
2

• Select to points on the line
– (x
1
, y
1
) and (x
2
, y
2
)
– NOT DATA POINTS
60
50
40
30
20
10
0
0
Independent vs. Dependent
5 10 15
Independent Variable
20 25
60
50
40
30
20
10
0
0
Independent vs. Dependent
5 10 15
Independent Variable
20 25
3

• Read the grading check list
• Lab Questions
– How does a radio wave interact with the ground and ionosphere?
– What was the shape of the radio waves path?
• Calculate the percent error and percent difference
• Write the conclusion and abstract for the first page
• Grade the other groups lab
– Use the grading checklist
– Record grades at the bottom of each page
– Reviewer’s grade depends on how well their evaluation matches the teachers evaluation
• Finish the lab activity by facilitating a fish bowl discussion with the peer reviewers
– How did your group’s method, data and conclusion compare to those use by the group you review?
– What were the challenges of the lab?
– What were the challenges of the report?
– How were differences between group members resolved?
– Was the work evenly shared?