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

What you are going to be doing in this activity is looking at real scientific data, both collected by other students and by scientists, to try to find evidence of solar flares that have impacted our ionosphere! Everyone who successfully completes this activity (and sends us a valid email address) will receive a certificate noting your accomplishments!

Step 1: What you have to know to do this activity

Solar flares imaged by the TRACE satellite
Solar flares imaged by the TRACE satellite.
Photo courtesy NASA.
Our 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, the highest portion of our atmosphere, 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 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.

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

In addition to the daily fluctuations, activity on the Sun can cause dramatic and 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. Watch a video of the largest flare every recorded on the Sun: X-Flare!

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 Monitors. You will be looking through the SID monitor data to find flares from the Sun!

Going Farther:


Step 2: Find a flare that appeared on the Sun

NOAA, The National Oceanic and Atmospheric Administration (i.e. the national weather service), has satellites (GOES) that track solar flares. These GOES satellites are circling the Earth all the time and NOAA keeps lists of the solar flares they find. We call these the GOES catalogs.

Flares are labeled by their strength, just as earthquakes are. Flare classes have names: A (the weakest), B, C, M, and X (the strongest). Each category has nine subdivisions, e.g., C1 to C9, M1 to M9, and X1 to X9. These are logarithmic scales, much like the seismic Richter scale. So an M flare is 10 times as strong as a C flare. You'll be looking for M-class or X-class flares, which are big. Our SID monitors don't always pick up flares weaker than M-class.

2.1 Looking for Flares

Go to the NOAA list of solar flares: GOES Catalogs. You should see something like this:

example flare list showing the flare's name, size, and date modified

Scroll down to the bottom of the page and click on a recent year. For this example, we'll pick: goes-xrs-report_2015.

Note: It can take several weeks for the GOES scientists to get their flare data into the catalog. If you want to look for a recent flare and the date doesn't appear yet in the GOES catalog, you can attempt to find it here: Space Weather Prediction Center warehouse. (Click on the current year, then on the yyyy_events link, then on the yyyymmddevents.txt link.)

Now you'll see a screen that looks similar to this: We highlighted a particular line, which we'll describe later.

list of data showing various columns of humbers, type of flare, etc.

Don't worry about all the numbers. You only need to check a few!

Each line in the file represents a solar flare. Now, let's look at the line we highlighted. The first column includes the date. For example, in our highlighted line, 31777150113. Ignore the 31777. So the date for the highlighted data item is 2015 January 13.

Columns 2,3, and 4 tell you the time when the flare started, when it ended, and when it had its highest peak. In our example, the flare started at 04:13 UT, ended at 04:38 UT, and was strongest at 04:24 UT. Universal Time (UT) is a time standard based on the Earth's rotation and used by international agreement. So, 00:00 UT is midnight at the prime meridian, which passes through Greenwich, England. 12:00 UT is noon, and 23:59 UT is 1 minute before midnight at Greenwich, England.

The items in columns 6 and 7 tell you the strength of the flare. In our example, the flare strength is M 56, that translates to M5.6, a strong flare. (Remember, SID Monitors primarily pick up flares labeled "M" or "X", the strongest ones.)

Now you get to use the information in the 10th column. Note that the number "12257" appears in the 10th column in our example. This means that the solar flare we picked originated from an Active Region on the Sun that has been labeled 12257. An Active Region is a location on the Sun where strong magnetic fields are appearing at the surface and moving around violently. These are where flares usually occur.

So, in our example, we found an M5.6 flare that occurred on 13 January 2015, and originated from the active region #12257 on the Sun.

2.2 Now YOU pick a flare to look for!

Now it is your turn to go through this procedure again and pick a flare you would like to track. Use one of these links: You'll need to look through various dates in the Current Flare List and look for X-class or M-class flares. You might want to see if any flares occurred on your last birthday, for instance. If a date isn't listed in the catalog, it means there were no flares on that date.

Since the Sun has a cycle of 11 years, going from almost no flares to lots of flares, and back, there are some years where you won't find any X and only a few M flares. Other years, you may find a lot of them! The last solar maxmum was in 2013, so in the years after that there will be fewer and fewer flares.

Once you find a flare, make sure you write down:


Step 3: Find evidence that your flare struck the Earth

You'll find out if your flare impacted the Earth's ionosphere by looking at the SID Space Weather Monitor data. Stanford University's Solar Center has developed Space Weather Monitors (SIDs). These are scientific instruments that track changes solar flares make to the Earth's ionosphere. They do that by "listening" to very low frequency (VLF) radio signals being transmitted around the world. The VLF signals "bounce" off the Earth's ionosphere. As the ionosphere changes, the strength of the VLF radio signals changes as well.

Over 900 SID monitors have been placed in 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. Much of this data have never been looked at, so you could discover a real event!

3.1 What you need to know

3.2 How to read SID data

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 radio 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. Two solar flares are labeled in red on the data graph below, an X2.1 flare and an M1.0 flare.

Note the solar flares can only be picked up during the daytime (why?). Remember that the times along the bottom represent UT time, not necessarily the site's local time. To help read the data, we have included arrows that indicate sunrise and sunset both at the local site and at the transmitter that the site is listening too. The blue arrows show sunrise and sunset at the SID Monitor site. The black hours show sunrise and sunset at the transmitter site. At least one of these must be in daylight for a solar flare to be picked up. Most of the spikes and "noise" you see in the nighttime data are from lightning strikes and thunderstorms.

SID data graph showing flares. Labels added for clarity.
SID data graph showing flares.
We added labels so you could better understand it.

3.3 Ready, Set, Find Your Flare!

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. The data browser actually makes it easy for you by labeling known flares at the top of each graph.

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.

Go to the SID Database and follow our instructions below!

You can click on any image below to see it larger.
1. Here's what you see first:

screen shot of SID data page
The opening screen shows you data for the last day. But you will want to search for a a particular date. So you will need to push the View Data by Date hotlink (pointed to by gold arrow).

2. Look for your date:

screen shot of SID date page

The new screen will list dates. Find the one you want. For example, let's use July 23, 2016. Hit that hotlink (pointed to by gold arrow).
3. Here's the screen for July 23, 2016:

screen shot of SID data page

Use the scrollbar on the right to see all the graphs.

Notice that the first graph on the image above is not very good data. We have found a way to help you tell good data from poor (noisy or badly calibrated) data. Look at the arrow labeled #1. It points to a place you can check to Show estimated data quality. If you check that box, and then hit the Update Graph button pointed to by arrow #2, then each graph will be analzyed for quality. Good quality data will have very low numbers, like 1, 2, 3, etc.

4. This screen shot shows the listing of quality data for several graphs.
example of bad quality data
This graph has very noisy data. The quality label is 53, meaning very poor data, and no flares are visible.

example of good quality data
This graph has very good data, with a quality rating of 10. Note that the M6.7 flare we are looking for clearly shows up (orange box).

example of good data

This graph also has very good data, with a quality rating of 8. Note that the M6.7 flare we are looking for also clearly shows up.

5. Now, using the scroll bar down the right side, look at all the graphs to see if you notice a peak (or dip) in other data around 05:16:00 GMT.

Not all sites will have picked it up because it might have been nighttime at their site, or their monitors were turned off, or not tuned properly.

Sometimes flares are hard to tell from noise and electrical interence. Here are some examples to help distinguish flares in the data

6. Write down the names of the sites and transmitters that appeared to have picked up the flare.

When you find one that shows the flare, use the bottom scrollbar to move over to see the name of the site and transmitter. Look at the examples in Step 4 (the orange boxes to the right). The two good graphs we showed in Step 4 are "CQD AGO 9190" and "HWU AGO 9190". The first 3 characters are the names of the transmitters. You can find the location of transmitters. CQD is locating in Skelton, United Kingdom. And HWU is located in Rosnay, France.

In both our good examples, the site was "AGO" and the monitor ID was 9190. Unfortunatley, we do not have a way for you to determine where the sites are (yet).

Did you find other sites that picked up the flare?


Step 4: 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.

Active regions are given consecutive numbers by scientists as they appear on the Sun's disc. If you have detected a flare and want to know where on the Sun it came from, you'd need to use the Active Region number you got from Step #2. With the time and region number of a flare, you can see a picture of the active region on the Sun itself.

Solar active regions
Solar active regions

Go to The current day’s solar active regions will be shown there. If the disc 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 It will look something like this:

Example of the active region catalog
The date is hidden in the link name. For example, the last link shown is "sunspots_1024_20060122.jpg". So the date is January 22, 2006. 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.

Now, with the Active Region number you previously collected, you can figure out where on the Sun your flare came from! Use this site to look for a similar image for your flare. (Remember to scroll down toward the bottom to find your date.)


Extra Credit: Find your Active Region on the backside (farside) of the Sun

The Sun rotates (it takes about 27 days at the equator). So your Active Region might have evolved on the back side of the Sun before it rotated into view. The HMI instrument, on NASA's Solar Dynamics Observatory spacecraft can actually "take pictures" of the backside (scientists call it the farside) of the Sun. If you would like to find out if your Active Region initially appeared on the farside of the Sun, try this:

* Seeing the Farside of the Sun *


Step 5: Submit your Solar Flare Report Form

If you were successful at finding a solar flare event in the SID data:

* Send us a report! *

Everyone who sends us an accurate report (and a valid email address) will receive a certificate acknowledging your flare discovery!

Remember that the GOES satellites are detecting solar flares as they are emitted from the Sun. The SID monitors are 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.