What is the NJAA SID Project.
Dear Reader, below is an article that I have written for our astronomy club, The New Jersey Astronomical Association. This should help fill you in as to what the NJAA SID Project is all about. Please don't hesitate to visit our club's website at NJAA.ORG

Lets Bring SID home

By

William Anthony

 

No Sid is not my long lost brother. SID stands for Sudden Ionosphere Disturbance, which are usually caused by solar flares.  Members of the American Association of Variable Star Observers (AAVSO) SID program use inexpensive radio equipment to detect and record these quick changes of the ionosphere.  Members then send in reports at the end of the month listing SIDs they have recorded.   Their reports typically contain the time a SID starts, peaks, and ends. The ability to detect solar flares with radio immediately caught my attention. Thoughts soon went through my head of joining the AAVSO SID program. The theory behind the program is not difficult to understand. But constructing the equipment for the SID monitoring station was a little over my head.  So it appeared best to drop the idea. Then it became apparent that a SID monitoring station could be constructed with the help of NJAA research members.  Also the station could be located at the observatory and be used by members wishing to get a taste of amateur research.

So lets first look at the workings of a Sudden Ionosphere Disturbance.

 The ionosphere is an area high above the earth containing a high concentration of ions. It is important to understand the relationship between radio waves and the ionosphere to realize how these disturbances can be observed. Radio waves with long wavelengths can use the ionosphere as a type of mirror.

High Frequency (HF) radio waves and Very Long Frequency (VLF) radio waves typically bounce off the ionosphere and the earth. Hence these radio signals can literally travel great distances by bouncing from the earth to the ionosphere many times.In brief, a VLF or HF signal transmitted in Europe can be received without difficulty in America. (Note* Typical FM radio signals do not use the ionosphere in such a way, hence we do not hear FM radio stations from very distant transmitters). Many countries, including the U.S., use VLF signals to communicate with their submarines. This is due to the VLF signals excellent ability to travel the earth. Our receiver will most likely use NAA, a US Naval VLF radio station in Maine. NAA is located at 24.0kHZ and puts out a continuous signal.

During a solar flare, an interesting thing happens to the ionosphere.  Eight minutes after a solar flares occurrence on the sun, the x-ray energy from the flare will reach the earth and quickly ionize the lower D-layer of the ionosphere. .(During the day, the lower D layer is usually weak and not very ionized.)   This changes the ionosphere in such a way that HF signals will fade out (or be absorbed), while VLF signals will actually grow stronger.   When the ionosphere is no longer receiving X-ray energy it will quickly return to its previous state.   Then the VLF signal should return to normal while the HF signal will reappear. To sum up, by looking at these changes, we can indirectly detect when a solar flare starts and ends. So now that we know the basics let us look at the equipment of a SID monitoring station. 

The SID monitoring station consists of an antenna, VLF receiver, A/D Datalogger, and computer. Except for the computer, the equipment used is of special design.  A person cannot go to Wal-Mart and purchase a SID monitoring station.   But plans for the equipment are on the Internet at AAVSO.Org.and the parts for the equipment are not expensive.  A receiver and an antenna can be built for about $30-$35 dollars each.  A kit for the A/D datalogger can also be purchased from AAVSO somewhere in the area of $50-$30.So granted that the computer is available, it should not cost you over $150 to build a station.

The VLF receiver with the antenna is tuned to a specific VLF signal. But this generates an analog signal, which our computer can’t monitor. Hence the receiver is then connected to the A/D Datalogger, which converts the analog signal from the receiver to a digital signal our computer can understand.  The A/D Datalogger then connects to the computer (through the parallel port).  The computer then runs a program, which will track the signal strength of the VLF station over time.  At the end of a week, we can graph our data and look for quick VLF signal increases.  These should correlate nicely to any solar flares that occurred during the week.  (Please note, that the quick increase of our VLF signal is called a Sudden Enhancement of Signal or S.E.S.) While monitoring for SIDs may help us detect disturbances in our local solar system, there is also a slight possibility of monitoring explosions from the far reaches of the universe.  The Gamma Ray Burst (GRB) is now the most energetic explosion known in the universe. The amount of energy released during a GRB is so great that they make supernovas look like tiny firecrackers.  But interestingly enough these explosions are quick.  At this time GRBs are still much of a mystery.

While the results are slightly inconclusive, it appears that strong GRBs can actually produce a SID. GRB’s release an incredible amount of energy in the X-ray spectrum.  While it is very rare, SIDs have been recorded which appears to be GRB related.  Just as the x-ray energy from the Sun can create a SID, so can that from a GRB. Last month a large GRB created a SID event for at least one of the AAVSO SID members recording during that time period. The AAVSO has been showing the results to the professional community and now urges SID members to look for such events.  This is amateur research on the edge, because professionals were not even sure whether it was possible for these events to be monitored via the SID method.  Please note that AAVSO has setup a group of observers to monitor and image GRBs via CCD.  Observers are informed via email as soon as GRBs are detected via satellite. AAVSO SID members have been asked to subscribe to these e-mails in order to look for SID-related GRBs in their data as soon as possible.  After looking at the amateur’s recording of the GRB related SID, I realized that it was recorded just a little after morning.  This would mean that earth based optical telescopes could not have imaged this GRB because it was located too close to the Sun.  But the SID monitoring station still gives us a way of observing the GRB.  For more information please see the February AAVSO Solar Bulletin at aavso.org)

The Advantages and Disadvantages of SID Monitoring

It cannot be said that SID monitoring is not with out its problems for recording solar flares. The biggest problem is that not all solar flares can be recorded via SID recording.   Only solar flares that occur during the daytime for a SID station can be recorded.   Furthermore SIDs can become localized at times where say one person in NJ will record a SID while an observer in Florida may not.This happens when a small area of the ionosphere has been affected, yet the signals path to the person is Florida does not travel via the disturbed area.   In addition to this the solar flare must be large enough to cause a SID. But don’t get your hopes down because even with these difficulties the majority of large solar flares can easily be recorded. One last difficulty for those wanting to report their data to AAVSO is that the data must be accurate within one minute per day.  Unfortunately computer clocks do wander a bit, but we have thought of many ways to deal with this problem.

SID monitoring does offer many benefits that may be of interest to amateur astronomers. As mentioned before this method can be used to monitor solar flares, with the small possibility of monitoring a GRB. The SID method can also be used to record radio outburst from the sun that usually foretell a solar flare with in an hour or so. In addition, if the computer can be set up to graph the data it is receiving, then an observer can become aware of a SID event the instant it takes place.

This alone harbors some very interesting possibilities.    Rarely do solar flares release energy in the white light spectrum. But a solar flare does release energy that is visible in the H-alpa spectrum. Therefore an observer viewing the Sun with a telescope and H-alpa filter (they are not cheap, but NJAA does have one.) should be able to visually observe or photograph the solar flare. Also, as brought to my attention by solar observer Maria Hansen, solar flares sometimes occur within a few hours of each. Therefore if the SID monitoring station records a solar flare during the morning, an observer has a good chance of witnessing another solar flare before the end of the day.   It is important to note that we can measure our station’s success using the Internet.  Professional astronomers use satellites to keep tabs on solar flares and GRBs.  Their websites usually include such information as to when a solar flare occurred in universal time and its size.  Information such as this can help us determine if our station is working properly and what it is detecting.

 

 

NJAA SID Project’s present status.

 

  Without a doubt the project has been moving forward very rapidly.  I made a presentation about the possibility of constructing a SID monitoring station at NJAA two months ago.  The NJAA Board graciously allotted $150 (my proposed estimate) for the project.  Over the next month research member Herb Johnson and I worked on some of the equipment issues.  Herbs knowledge in electronics was instrumental in helping the project move forth.   After contacting AAVSO SID members, and discussions with Herb, we started to get a better picture of how to construct our station. 

  At the next research meeting, four members came forth who were willing to join the project.  Over the next month Steve Smith designed and produced, the boards needed for the A/D Datalogger and VLF Receiver.  Mean while Joe Marshalek agreed to build the antenna for the receiver.   On March 26 we met at NJAA to discuss the construction of the station.  Steve brought two receiver boards along with parts to build one receiver.  This was a happy surprise. Steve had produced his own PC boards for the Receiver and A/D Datalogger, which he says, can cost around 8$ dollars to make. (This greatly interested members of the group)  This also frees us from relying on outside sources for the boards.   That night after discussing construction issues, Garrett Smith (Steve’s son) cleaned up one of the boards to which Gabriela Levit preceded to solder the parts to.  

 

NJAA SID Project’s Future

     As of now, I believe our station will be operating within a month. Plans are in the works to use two VLF receivers plugged into one A/D Datalogger.  The datalogger will then connect to a computer.  This will allow us to monitor two radio stations at once. Monitoring two stations will increase our ability to detect SIDs.  As mentioned before, these events can sometimes be localized.  Receiving signals from two directions will help cut down on this problem.  Once the SID station is up and running we plan to join the AAVSO SID Program.   This consists of sending in monthly reports, which are analyzed by AAVSO.  Then AAVSO in turn sends a report to NOAA.

    Members who are interested can join the project.   There are many areas where members can help out.  The computer used for the station may need to have its computer clock resynchronized weekly.  Also, the data produced by the station will need to be analyzed.  In turn this data can be used to fill out monthly reports to be sent to AAVSO.

    I have been working on my own website over the past few weeks at www.astromodel.50megs.com.  This site will also include a webpage for the NJAA SID project.  On this page I plan to display pictures, recent data, and relevant links.  The NJAA website will also include a page about the project displaying a synopsis and results.

 

  If you are interested in joining the project, please e-mail me (William Anthony) at bill518@hotmail.com .  Members of the group regularly meet at the NJAA research meeting held the second Friday of every month. 

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