Solar Bulletin May, 2002

• Sudden Ionospheric Disturbance Report
• Sudden Ionospheric Disturbances Supplement

Click image to enlarge. Fig.1.10 cm Solar Flux and Comparison of Ri (provisional) and Ra Estimates for April (r=0.970). (Ri Source: http://sidc..oma.be/index.php3) (!0cm Source: http://www.drao.nrc.ca/icarus)

Click image to enlarge. Fig.2 Maximum, Mean, and Minimum Ra Values for Each Month from January 2001 to Present.

Michael Hill, SID Analyst 114 Prospect St Marlborough, MA 01752 USA noatak@aol.com

Code Observer Station(s) monitored A29 A Clerkin NAA A50 J Winkler NAA A52 D Toldo NAA, NWC, HWU A63 J Ellerbe ICV A83 A Panzer NAA A84 W Moos FTA A87 M Hill NAA A93 G DiFillipo HWU A96 R Battaiola HWU A97 J Wallace NAA A99 M King HWU A100 P Campbell NLK

The events listed above meet at least one of the following criteria Reported in at least two observer reports Visually analyzed with definiteness rating = 5 Reported by overseas observers with high definiteness rating

Solar Events

Many thanks go to observer Andy Clerkin (A29) for finding the location of our data in the NGDC archives. It is now being updated regularly, however the location on the web has changed as well as the format of the web site and data archiving facility. To locate the data follow the directions below:

http://sgd.ngdc.noaa.gov

Goto: Part 1 - Prompt Report 2
SID Data
Select month/year to display a PDF document for that time frame.

MORE ON X-RAY TRANSIENT XRF 020427

Last month in the April issue of the SID Supplement I described how Len Anderson, A-91, in South Perth, West Australia had recorded the x-ray transient as an SID and reproduced his recording of the event. I sent a copy of that SID Supplement to Dr. Gerald J. (Jerry) Fishman, Chief Scientist for Gamma-Ray Astronomy at the NASA-Marshall Space Flight Center in Huntsville, Alabama, USA and asked him what he thought of it. He liked it very much and wrote a GCN Circular to announce what he considered an important gamma ray burst observation. GCN Circulars are issued regularly to announce important gamma ray burst (GRB) observations. GCN stands for GRB Coordinates Network and the circulars go out to about 500 professional observatories throughout the world. Here is the GCN circular Dr. Fishman posted:

Subj: [AAVSO-GRB] XRF 020427: Sudden Ionospheric Disturbance (SID)
Date: 5/24/02 8:50:17 PM GMT Daylight Time
From: grb@aavso.org
Sender: aavso-grb-list-admin@informer2.cis.McMaster.CA
To: aavso-grb-list@informer2.cis.McMaster.CA

The following is a GCN Circular circulated via the AAVSO network. For an archive and more information on circulars visit: http://lheawww.gsfc.nasa.gov/docs/gamcosray/legr/bacodine/gcn3_archive.html

TITLE: GCN GRB OBSERVATION REPORT
NUMBER: 1394
SUBJECT: XRF 020427: Sudden Ionospheric Disturbance (SID)
DATE: 02/05/24 19:16:01 GMT
FROM: Peter Woods at UAH/MSFC

G.J. Fishman, P.M.. Woods, C. Hossfield and L. Anderson report that the X-ray rich event of April 27, 2002 was detected as a Sudden Ionospheric Disturbance (SID) by Len Anderson in South Perth Australia, indicating that XRF 020427 (GCN 1383), produced a prodigious amount of ionizing x-ray flux. The disturbance is clearly seen, lasting about one minute, in a low-resolution all-day strip chart recording from a Very Low Frequency (VLF) radio receiver near Perth. Although a quantitative measure of the flux of this event could not be determined by this method, the SID magnitude (and thus the ionizing flux) is comparable to that observed from the Aug. 27, 1998 super-flare from SGR 1900+14 (Inan, et al., Geophys. Res. Lett., v.26, p.3357, 1999). A large flux of x-rays below ~15 keV was deduced from that flare (op. cit.). One intense gamma-ray burst, GRB830801, was also observed to produce a SID but at a much weaker level (Fishman and Inan, Nature v.331, p.418,1988). The strong ionizing present in this burst confirms that this is a long, x-ray rich event of unknown origin, as suggested by in't Zand et al. (GCN 1383).

Note: SIDs have been used to study solar flares since the 1950s. In this case, the SID was observed as a major change in the propagation of a continuous VLF radio transmission at 19.8 kHz from Northwest Cape, Australia. The VLF radio receiver trace can be seen at: http://gammaray.nsstc.nasa.gov/~woods/xrf020427.html This message may be cited.

It is quite an honor for Len to have his recording of XRF 020427 sent out by NASA as a GCN Circular. It shows that NASA considers it valuable scientific data. They want us to continue to search for GRBs in our SID recordings we make to detect solar flares for NOAA. Now we have a chance to make our work valuable for NASA too. But there are valuable lessons to be learned from Len's GCN Circular. One thing Dr. Fishman mentioned is the chart recording must be for a whole day and show the sunrise and sunset patterns so scientists looking at the chart can put the SID in context and see that it is something unique that happened that day. Len's chart fulfills that requirement because it is free of interference all day and the trace is nice and clean so the GRB's SID stands out clearly. The GCN Circular compares Len's SID to that of SGR 1900+14 that was published in the peer reviewed journal, Science, and also in Sky & Telescope magazine. Unfortunately Len's SID will not make it into those prestigious publications because his time is off by one hour. Therein lies another valuable lesson. You must keep your chart time correct. If you record on a strip chart recorder as Len and many others do it is probably best to run your chart on local civil time starting and ending at midnight each day. Mark the Civil day on each chart just before the sunrise pattern. Mark local noon at 12:00 and also the Universal time of local noon each day. Also mark 0000 UT each day and the UT day that starts there. It is easy to get confused if you switch your civil time to daylight saving time. Here's how to make sure your UT time at civil noon is correct: Watch for a prominent SID and look up its time of maximum at the NOAA Web site: http://www.sel.noaa.gov/ftpmenu/indices/events.html >> Mark the UT hour immediately preceding the maximum of the SID and count forward or back to noon to make sure you are marking the correct UT of local civil noon each day. This chart will now be the correct format for a GCN Circular and the time of all events, Solar and GRB, will show the correct universal time and date. It is also important to have chart time set correct to the nearest minute. An easy way to do this is to subscribe to the free service of the US National Institute of Standards and Technology, NIST. It is available anywhere in the world. It will keep your computer clock accurate and reset it to within a few milliseconds when you click its icon on Desktop. Subscribe to it at : http://www.boulder.nist.gov/timefreq/service/its.html >> Here's how you can also use it to set your strip chart recorder time accurate to the nearest minute. Advance your chart to the next minute line and turn off the chart drive motor. In the case of a Rustrak recorder there is a time line every 15 minutes. Click on the NISTIME icon on Desktop and it will bring up a real time window where the seconds are being displayed. Watch for the time of the line your recorder has been advanced to and restart the chart drive motor on the 59th second before that time.

There is good news to report. We have a new SID observer in Hamilton, Ontario, Canada. He is Douglas Welch, A-104. Who records VLF station NAA in Cutler, Maine transmitting on 24 kHz. Doug is a long time member of the AAVSO. He became interested in astronomy at an early age and joined the AAVSO as a teenager to become a variable star observer. This deepened his interest in astronomy and lead him to choose it as his life work and become a professional astronomer. He is now a professor in the Department of Physics and Astronomy at McMaster University in Hamilton, Ontario, Canada. Find out more at: http://www.physics.mcmaster.ca/people/faculty/Welch_DL.html >> and click on his homepage. Here is a chart he made showing a nice SES on 17 May.

Click image to enlarge

Doug's receiver is the hexagonal loop antenna receiver described in the April SID Supplement of the Solar Bulletin. He wound the loop with # 14 wire and it is in his basement and picks up little if any interference. The vertical scale is enhanced which required me to reduce the size of the whole chart to make it fit on this page. Doug had trouble tuning to 24 kHz and made a tuner to make it easier. The problem is you can compute the capacity you need but when you make this from readily available capacitors their 5% inaccuracy can tune the loop too far from where you intended. A tuner will allow you to tune exactly to the stations frequency with 5% accuracy capacitors. I tuned my 1.5 meter loop with 24-turns of # 14 wire with a precision decade capacitor bank made by Cornell-Dubilier to determine the actual capacities needed . Here are accurate values for the capacitors needed to tune to some popular VLF stations.

TABLE 1 60 kHz, WWVB Fort Collins, Colorado, USA…….0.002 mfd
25.2 kHz (no call letters) La Mourie, North Dakota, USA…0.0175 mfd
NAA 24 kHz Cutler, Maine, USA ……0.0185 mfd
37.5 kHz, NRK Grindavik Iceland ..….0.008 mfd
24.8 kHz , Jim Creek, WA, USA ……..0.0178 mfd
21.4 kHz, NPM Hawaii, USA…….….0.023 mfd

You can make a tuner to find these stations from two Radio Shack 8-position DIP switches. These consist of eight little single-pole, single-throw switches side by side that mount on a printed circuit board. Radio Shack only carries the capacitors you need for this tuner in ceramic dielectric so you should use their ceramic capacitors. Below are the capacities for the sixteen capacitors you will need. Mount each switch on a little circuit board and connect one capacitor to each switch so when all 8 switches are in the on position all eight capacitors are connected in parallel. Leave the leads long when you solder them into the tuner so later when you have determined the combination of capacitors that tune to the station of your choice you can unsolder them with long enough leads to span the distance between the ends of your loop.

TABLE 2

Switch Number One:
Position # 1…..100 pfd 5…..100 pfd
2…..100 pfd 6…..470 pfd
3…..100 pfd 7…..470 pfd
4…..100 pfd 8…0.001mfd

Switch Number Two:
Position # 1…0.001 mfd 5…0.0047 mfd
2…0.001 mfd 6….0.01 mfd
3…0.001 mfd 7….0.01 mfd
4…0.0047 mfd 8….0.01 mfd

These two tuners should make it possible to find your station without an oscilloscope and signal generator. Connect them temporarily with Alligator clip leads across your Loop. It will take some patience but you can choose a combinations that add up to the values given in Table 1 to get close. Then tune up and down in 100 pfd increments until you peak on a strong signal. Use a multimeter or your recorder to measure signal strength. Record the strong signal you have found for a few days to make sure it shows sunrise and sunset patterns. If it shows these patterns you have successfully tuned your receiver to a suitable signal and it should record solar flares as SESs. Unsolder the selected capacitors from the tuners and solder them across the ends of your loop. There is no need to protect them from the weather. I have left loop tuning capacitors exposed to all kinds of weather for years with no problems so long as the connections are soldered.

Experience so far has shown that because the loop antenna receiver's amplifier is connected directly to the loop antenna it can be easily damaged by nearby lightning unless you protect it with a lightning arrestor. An automotive spark plug makes a good lightning arrestor. Shorten its gap to about 0.2 mm or 0.008 thousandths of an inch and connect it across the ends of the loop. If your receiver produces strange results it might be a good idea to add the spark plug lightning arrestor and replace the TL082 op amp. If lightning strikes very nearby it will probably Zap the TL082 completely. My experience has been that nearby lightning damaged the TL082 so that it produced a distorted sine wave signal and produced an unsteady trace. Before it was damaged the signal was a pure sine wave and the trace was steady. On another occasion the signal disappeared completely but had returned by the next day as a distorted sine wave as viewed on my oscilloscope.

The chart below was made by Werner Scharlach, A-9, in Tucson, Arizona, USA who records NAA in Cutler, Maine, USA transmitting on 24 kHz. It shows the same 17 May SID as is shown above on the previous page with the difference that this chart was made with a Rustrak strip chart recorder and the vertical scale is not enhanced.

Click image to enlarge

Return to the Solar Division home page