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The effect of solar activity on radio propagation

The effect of solar activity on radio propagation

Introduction: (Initial Observation)

The effect of sun on the earth atmosphere has been a base for many interesting studies by scientists around the world. Many atmospheric conditions are contributed to the solar activities. After all it is not just the sunlight gets to the earth. Our planet is also being affected by electromagnetic waves, gravitational forces and other radiations from the sun. Scientists have tried to find a relation between solar activities and atmospheric events on the earth.

Earthquake, volcano, aurora, sudden changes in temperature are among the events that are being studied for their relation with solar activities.

Electromagnetic nature of radio waves make them susceptible to many weather phenomena including the electromagnetic activities of the sun. In this project we plan to find out how do solar activities affect the propagation of radio waves.

This project guide contains information that you need in order to start your project. If you have any questions or need more support about this project, click on the “Ask Question” button on the top of this page to send me a message.

If you are new in doing science project, click on “How to Start” in the main page. There you will find helpful links that describe different types of science projects, scientific method, variables, hypothesis, graph, abstract and all other general basics that you need to know.

Project advisor

Information Gathering:

Find out about solar activities such as solar winds and storms. Read books, magazines or ask professionals who might know in order to learn about the effect of solar activities on earth atmosphere. Many information about solar activities are available online by organizations such as NOAA and DXLC who monitor and study space weather conditions. Keep track of where you got your information from.
Following are samples of information that you may find:

The Earth is constantly bombarded with a stream of accelerated particles arriving not only from the Sun, but also from interstellar and galactic sources. Study of these energetic particles will contribute to our understanding of the formation and evolution of the solar system as well as the astrophysical processes involved. The Advanced Composition Explorer (ACE) spacecraft carrying six high-resolution sensors and three monitoring instruments samples low-energy particles of solar origin and high-energy galactic particles.

ACE provides near-real-time solar wind information over short time periods. When reporting space weather ACE can provide an advance warning (about one hour) of geomagnetic storms that can overload power grids, disrupt communications on Earth, and present a hazard to astronauts.

ACE orbits the Libration Point L1 which is a point of Earth-Sun gravitational equilibrium about 1.5 million km from Earth and 148.5 million km from the Sun. With a semi-major axis of approximately 200,000 km the elliptical orbit affords ACE a prime view of the Sun and the galactic regions beyond.

The Thermosphere (the highest layer of atmosphere)
The atmosphere is divided into five layers. It is thickest near the surface and thins out with height until it eventually merges with space.
1) The troposphere is the first layer above the surface and contains half of the Earth’s atmosphere. Weather occurs in this layer.
2) Many jet aircrafts fly in the stratosphere because it is very stable. And the ozone layer absorbs harmful rays from the Sun here.
3) Meteors burn up in the mesosphere .
4) The thermosphere is a layer with auroras. It is also where the space shuttle orbits.
5) The atmosphere merges into space in the extremely thin exosphere. This is the upper limit of our atmosphere.

The transition from the mesosphere to the final thermosphere layer begins at a height of approximately 50 miles (81km). The thermosphere receives its name from the return to increasing temperature which can reach a staggering 3,600deg.F (1982deg.C). These extreme temperatures are caused by the absorption of the sun’s short wave ultraviolet radiation. This radiation penetrates the upper atmosphere, stripping atoms of their electrons and giving them a positive charge. Electrically charged atoms build up to form a series of layers within the thermosphere. These charged layers are often referred to as the ionosphere, which deflects some radio signals. Before the modern use of satellites, this deflection by the ionosphere was essential for long distance radio communication. Today, radio frequencies which pass through the ionosphere unaffected are chosen for satellite communication.

Beautiful auroras, also known as the Northern and Southern lights, occur in the thermosphere when solar flares from the sun create magnetic storms near the poles. These magnetic storms strip atoms of their electrons. Brilliant green and red light is emitted when the electrons rejoin the atom, returning the atoms to their original state. Even higher — above the auroras and the ionosphere — the gases of this final atmospheric layer begin to dissipate, until finally, several hundred miles above the earth, they fade off into the depths of space.

AM = Amplitude modulation
FM = Frequency modulation
SW = Short Wave

Question/ Purpose:

What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to determine how do solar activities affect the propagation of radio waves.

Identify Variables:

When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
Independent variable (also known as manipulated variable) is the time of day. Time also represents the presence or exposure to solar activities. For example solar activities in your area start at sunrise; get to a peak at noon time, and tends to end at sunset. You will observe the lowest effect of solar activities at midnight.

Dependent variable (also known as responding variable) is the propagation of radio signals. That can be expressed as your average physical distance from the farthest radio stations that you can listen to or the number of radio stations that can be listened between certain wave lengths.

Constants are the instruments (radio) and experiment method.


Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis.
This is a sample hypothesis:

Radio signals can propagate easier at night when no solar activities are present between the broadcasting station and the receiver. My hypothesis is based on my observation of a crystal radio that would work best at nights.

Experiment Design:

Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”

Experiment 1:

Does sunlight affect the propagation of radio waves?

Introduction: Radio waves naturally travel in straight lines, so you would naturally expect (because of the curvature of the earth) that no radio station would transmit farther than 30 or 40 miles. Certain radio stations, however, especially in the short-wave (SW) and AM bands, can travel much farther. Short-wave can circle the globe, and AM stations transmit hundreds of miles. It seems that short waves are reflected by the atmosphere and that make it possible for the waves to travel around the globe. In this experiment we intend to find out if sun and sunlight affect the ability of the atmosphere to reflect radio waves.

In this experiment we will examine the transmission distance and signal strength of radio waves at day hours (sun is present) and night hours (sun is in the other side of the earth).


Use a short wave radio to find radio stations out of your local area. All radio stations announce their wavelength and their location a few times each hour. For each radio station that you identify, record the wavelength, quality of the reception, their estimated distance from you and the time. Estimated distance may be found using a scale map or globe.

Repeat your search and recording in 3 different night hours and 3 different day hours for 5 nights and 5 days. Try to revisit the stations in different hours so you can compare the strength of radio waves at different hours.

Record your results in a table like this:


Station name

Day Hours Night Hours
Morning Noon Afternoon one hour after dark Mid night one hour before morning light

For the quality of reception use the words none, low, medium, good and very good. Alternatively you may use the numbers 0, 25, 50, 75, 100.

Make one results table for each day of your experiment. At the end combine the results by taking the average reception quality for each station. Your final results table will look like the above table; however, it will contain the average reception.

Use your final results table to draw a conclusion. Does sunlight reduce or improve the propagation of radio signals?

Alternate Procedure:

Use a short wave radio to find radio stations in a specific wavelength range. For example you may try to locate the stations that broadcast between 200 KHz and 300 KHz.

In different hours of the day (Every 3 hours for example) scan the selected range and count the number of radio stations that you can find.

Record your results in a table like this:

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Time Number of stations found
12:00 p.m. (Noon time)
3:00 p.m.
6:00 p.m.
9:00 p.m.
12:00 a.m. (Midnight)
3:00 a.m.
6:00 a.m.
9:00 a.m.

Note that depending on the type of radio that you have, you may need to select a different range of broadcast frequencies.

Make a graph:

Use the above to make a bar graph and visually present your results. Make one vertical bar for each Time you have tested. Write the time under each bar.

The height of each bar will be the Number of stations found at that time. (For example you may use 1 inch for each 10 stations)

Materials and Equipment:

Following is a sample list of material that you may need for your experiments:

  1. A short-wave radio receiver
  2. A computer with Internet access
  3. World map or a globe

Results of Experiment (Observation):

Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.


If you do any calculations, write your calculations in this part of your report.

Summary of Results:

Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.

It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.


Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Some of the information that may be included in your conclusion are:

This extended transmission of radio waves is possible because of the ionosphere — one of the layers of the atmosphere. It is called the ionosphere because when the sun’s rays hit this layer, many of the atoms there lose electrons and turn into ions.

As it turns out, the ionosphere reflects certain frequencies of radio waves. So the waves bounce between the ground and the ionosphere and make their way around the planet. The composition of the ionosphere at night is different than during the day because of the presence or absence of the sun. You can pick up some radio stations better at night because the reflection characteristics of the ionosphere are better at night.

Related Questions & Answers:

What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.

Possible Errors:

If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.

If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.


Visit your local library and find books related to radio broadcast, wavelengths and distances. In addition to such books, you may list this website and the following links as your references or bibliography.




Planetary Geomagnetic activities