Tracking Solar Flares
Tracking Solar Flares Space Weather Monitors The Ionosphere Activity Resources Glossary

Tracking Solar Flares Activity

Step 1: What you are going to be doing in this activity is looking at real scientific data, collected by other students, to try to find evidence of solar flares that have impacted our ionosphere!

Read below about how the Sun sends high-energy rays to the Earth and how those rays affect the Earth's ionosphere (the upper atmosphere directly above your head). No, there won't be a test. But it will help you understand your data if you understand what it is measuring!
Then watch a video of the biggest flare ever recorded on the Sun!


Solar flares imaged by the TRACE satellite.
Solar flares imaged by the TRACE satellite.
Photo courtesy NASA.

The Sun spews out a constant stream of X-ray and extreme ultraviolet (EUV) radiation. This energy, along with that from cosmic rays, affects the Earth’s ionosphere, starting some 60 km above us. When solar energy or cosmic rays strike the ionosphere, electrons are stripped from their nuclei. This process is called ionizing, hence the name ionosphere. 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. The strength of the received radio signal changes according to how much ionization has occurred and from which level of the ionosphere the VLF wave has “bounced.”

The Earth’s ionosphere and reflecting of VLF radio waves.
The Earth’s ionosphere and reflecting of VLF radio waves.
Image courtesy of Morris Cohen, Stanford University

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. During the night hours the cosmic rays dominate because there is no ionization caused by the Sun (which has set below the horizon). 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. The Sun can unexpectedly erupt with a solar flare, a violent explosion in the Sun's atmosphere caused by huge magnetic activity. These sudden flares produce large amounts of X-rays and EUV energy, which travel to the Earth (and other planets) at the speed of light.

The biggest flare ever recorded on the Sun
Why is the Sun green?

When the energy from a solar flare or other disturbance reaches the Earth, the ionosphere becomes suddenly more ionized, thus changing the density and location of its layers. Hence the term “Sudden Ionospheric Disturbance” (SID) to describe the changes we are monitoring and also the nickname of our space weather monitoring instrument, SID.

Read more about how the Sun affects the Earth

Read more about our ionosphere

Watch more videos of the Sun's super flare!

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Step 2: Try our example of how to look for flares in the SID Space Weather Monitor data:

Find potential flares or other events in our SID Space Weather Monitor data
Stanford University Solar Center's Space Weather Monitors (SIDs) are scientific instruments that track changes the Sun makes to the Earth's ionosphere. SID monitors are placed in middle school, high school, and college classrooms all over the world -- and anyone can access their data! You are going to look through the SID data we've collected to see if you can find solar flares or other exciting astronomical events. Much of this data have never been looked at, so you could discover a real event!

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Step 3: Pick you own flare to search for. The example will show you how:

Write down the date and time of the flare you would like to find. If you'd like, you can start a Solar Flare Event Report for us!

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Step 4: Search for your flare in the SID database. You'll do this just as we searched for the 5 December 2006 flare in our example above.

SID Database

Solar SID data are easy to understand and somewhat similar to those from a seismograph. Look at the graph below: the horizontal axis represents time, in this case about 24 hours. The vertical axis represents strength of the VLF signal being received. (The actual measured values of this aren’t important, only the amount of change.) As you learned above, the strength of the VLF signal changes depending upon the ionization of the Earth’s ionosphere, and that depends upon what is going on on the Sun! Solar flares, and sometimes other astronomical events, show up on SID data as spikes above (or occasionally below) the normal signal strength level. Four solar flares are labeled on the data graph below.

SID data graph showing flares. Colors and labels added for clarity.
SID data graph showing flares. We added the colors and labels so you could better understand it. In the real data, your flares will not be labeled!

Finding flares in the data is the most important part of this activity. Once you find a flare, the rest is easy! Now, with the date and time of your flare written down, you can go to the SID database to see if any of the monitors picked up your flare:

Go to SID Database

If the SID data shows your flare, you can start a Flare Report Form You'll eventually send it to us, and receive a certificate acknowledging your scientific find!

If you couldn't find your flare in the SID database, it may have occurred when most of the monitors were in nighttime. Pick a different flare from the catalog and try again.

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Step 5: How strong was your flare?
To determine this, look back at the GOES graph for the flare you picked in Step 3.

GOES Graphs

On the website above, set the date and time to cover the day of your flare just as you did when you picked that flare. Then hit the GO GOES button. Our example shows 5 December 2006, the date of the flare we used.

Click for larger imnage

Find your flare on the graph and the list. The page shows that the X-ray flare on 5 December was an X.9.0, a really big one!!!

Click for larger imnage

Write down your flare's strength on the Flare Report Form. Also write down the number of the "Active Region", that's the number in the AR# rightmost column. In our example above, the AR# is 930. The number for your flare will be different. You'll need this number for the next step.

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Step 6: With the number you just collected in the AR# column, you can figure out where on the Sun your flare came from!
To see the Sun's active regions right now!

To look for a similar image for your flare.

Learn how to use these websites below.

Trace your flare back to the Sun

Active regions are places on the visible surface of the Sun containing strong magnetic fields in complex configurations and usually in a constant state of change and flux. Active regions are often associated with sunspots. They are most often the source of the solar flares you have detected.

Solar active regions
Solar active regions

Active regions are given consecutive numbers by scientists as they appear on the Sun's disk. If you have detected a flare and want to know where on the Sun it came from, you'dd need to use the AR# number you got from Step #5 above. With the time and region number of a flare, you can see a picture of the active region on the Sun itself!

Go to The current day’s solar active regions will be shown there. If the disk is blank, there are no active regions for that day. Since you will need to check for previous days’ images for your flare, hit the “List of all available daily images” near the bottom of that page. It will take you to

Scan down the list for the date closest to the date of your flare. Click on that hotlink and you should see a picture of the Sun's active regions for that time. Below is an example.

Example of a picture of the Sun with active regions labeled.
Example of a picture of the Sun with active regions labeled.
Image courtesy MDI instrument on SOHO spacecraft.

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Step 7: Did your flare's active region come from the backside of the Sun?
Farside Images

Learn how to do this by reading below.

Learning the history of your flare’s active region

Starting at the website above that showed your flare's Active Region, you can trace the history of your active region. Click on different images to work your way back in time until your find the region just appearing on the left-hand side if the Sun. Sometimes you will see the region forming while you search back. However, if it appears from over the Sun’s eastern (left side) limb, then you can look for it on the farside, or back side, of the Sun. You’ve find images at:

It will take you a little while to understand how to read these images, but the webpage gives you some help. And it’s worth the effort when you discover your active region first appearing on the far side of the Sun!

Below is a farside image of the Sun, showing both the side facing Earth ("Earthside") and the side away from Earth ("Farside"). The red and yellow "blotch" in the "Farside" section indicates a sunspot, or active region, on the back side of the Sun!

Image of the Sun, including side facing Earth and side away from Earth.

If this map confuses you, here's an equivalent picture of the Earth. Click on the image to watch a movie of how day and night change on the Earth. The farside images work the same way, although the back side of the Sun is not dark like the backside of the Earth!

Mercatur projection of Earth showing day and night
Click to see video

Earth image courtesy US Navy. Video and farside images courtesy of Philip Scherrer, Stanford University.

If you find your Active Region appearing in a farside image, write down the date of that image on your Flare Report Form. If you can't find the region appearing, don't worry. Sometimes they do not show up on the maps.

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Step 7: Submit your Solar Flare Report Form
If you think you've found a solar flare or some other interesting event in the SID data,
Send us a report!

Everyone who sends us a report (and a valid email address) will receive a certificate acknowledging your flare discovery during World Space Week!


Missing flares?

Sometimes a flare will show up in the GOES data graphs but not the catalog. The GOES data is reduced by hand, and often flares are "missed" being added, or they are determined for some reason not to be included in the catalog. If you find flare signatures in your SID data, and if those flares also appear on the GOES graphs, but they are not listed in the catalog, then you may have found flares overlooked or ignored by the GOES cataloger. We would LOVE to hear about that! Please submit a Flare Report Form tell us in the comments section that your flare did not appear in the GOES catalog.

Remember that the GOES satellites are detecting solar flares as they are emitted from the Sun. Your SID monitor is detecting changes to the Earth’s ionosphere caused by those same flares. So while your monitor and the satellites are tracking different effects, they are based on the same phenomena.

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