TRACKING A PERFECT STORM
Storm Signals
When a solar storm occurs, different kinds of invisible light are produced. You begin to monitor radio, ultraviolet and x-ray emissions from the Sun.
Dusty Samouce in Sula, Montana was using a Radio Jove antenna and detected these radio signals during May 27.
The first burst occurred from 15:00 UT (Universal Time) to 15:12 UT. The second one occurred between 23:50 and 23:53 UT. These plots show fairly common types of radio emissions from the Sun. The vertical axis tells us the strength of the radio signal. In the first minute of the plot the signal is low. Then the strength increases in a series of spikes. Almost 9 hours later another storm begins. Again the signal starts low and steady. Then the signal increases in strength in steps leading to a broad peak. Then the signal decreases and the event is over.
The WAVES instrument on the NASA WIND satellite also showed strong radio emissions from the Sun during the same times.
The plots from the WAVES instrument are a little different. The vertical axis is a range of frequencies. It is like the instrument is scanning many radio stations very fast and measuring the strength of the station signal. The strength of the signal is recorded as color. No signal is black. A weak signal is blue. As the signal strength increases the colors go from blue to green to yellow to orange to red and finally purple. The first plot of May 27 shows you that there were a few brief, weak radio bursts (red and yellow streaks) early in the day. Then about 15:00 UT there was a strong radio signal in all frequencies. It starts as red and quickly becomes purple in strength. This suggests a strong solar event. About 23:00 UT another strong solar event is recorded. A few hours later in the early hours of May 28 another large solar event is captured by the WIND WAVES instrument.
You check with someone who is skilled in reading these plots, and you are told that the last two events produced coronal mass ejections.
Well, you know there was a solar event, but how big was it? Will it affect Earth? To answer these questions you look at the x-ray plots from the GOES satellite (Geostationary Operational Environmental Satellite).
The GOES satellites, while primarily studying Earth and Earthly weather, monitor the Sun in x-ray and provide us with information about the solar wind and space weather.
The GOES satellites provide information about the strength of x-ray emissions from the Sun. The Sun is constantly producing x-rays, so you are looking for significant increases in the intensity of x-ray above a background. Scientists have developed a simple rating system for solar x-ray activity. They have created five levels; A, B, C, M, and X. A is the lowest level, B is 10 times more powerful than A, C is 10 times more powerful than B, M is 10 times more powerful than C, and X is 10 times stronger than M. So this makes an X event 10,000 times stronger than A. In addition, each level can be further divided from 1.0 to 9.9. This means you could have a C2.3 event, or a B7.9 or an M6.5. However, since X is the highest level, the numbers don’t stop at X9.9.
You check the GOES plots. The graph shows that normal solar activity was in the B range for May 26, 27, and 28. There were three M-class events on the 26th and 27th. While these are interesting solar events, the really big ones were X-class events late on the 27th and early on the 28th.
It is fortunate that you have so many resources observing the Sun. No one in the Radio Jove network recorded the second flare early on May 28th – probably because it was after sunset for most Radio Jove observers. But the satellites observing the Sun monitor continuously.
Sunspot 365 looked like a likely suspect for a flare. The radio wave and x-ray emissions tell you that several flares did occur and two of them were very strong, X-class flares that produced coronal mass ejections. But did these flares come from sunspot 365? Several satellites show where flares occur on the Sun. The GOES satellite took the left image on May 27. The SOHO satellite took the right image on May 28. These images show that sunspot 365 was, indeed, the location of both flares.
Considering the strength of these flares, you might predict that they would affect Earth. Experts reading the plot from the WAVES instrument tell you that there were coronal mass ejections from both eruptions. You notice that sunspot 365 is almost in the center of the Sun. That means that the material blasted out from the Sun is probably headed straight at Earth. A CME travels between 400 km/s (1 million miles per hour) and 1000 km/s (5 million miles per hour). A typical eruption can carry a billion tons of plasma, a mass equal to that of 10,000 aircraft carriers. A CME is very directional, blasting material out in a fairly narrow jet that can expand to about 30 million miles. It is very possible that these CMEs will affect Earth in 1 to 3 days! Better send out the Solar Storm alert and begin to monitor the Earth’s magnetic field!
- NASA Official: Dr. James Thieman
- Project Manager: Don Robinson-Boonstra
- Website Manager: Bryan Stephenson