Sudden Ionospheric Disturbances Supplement

SEARCHING FOR THE SIGNATURE OF GAMMA RAY BURSTS AS SUDDEN IONOSPHERIC DISTURBANCES, SIDs, is now very easy to do. The new HETE gamma ray burst satellite started its operational phase Monday, 26 March 01, by reporting two GRBs that day. Other prompt reports of GRBs are expected to follow. Log into ... http://space.mit.edu/HETE/Bursts ... to see these announcements. Also log into .... http://space.mit.edu/HETE ... to learn more about HETE. As of 8 April no further busts had been added to the two that were announced on 26 March. Presumably the HETE site is having problems getting its operational phase going. All we can do is keep checking to see when announcements start again.

The big news in April was a huge magnetic storm that started about 0100 UT on the 31st It produced an aurora that was seen as far south as Maryland in the eastern United States. Len Anderson, A-91, reported it was seen in the southern hemisphere as far north as South Perth, West Australia where he lives. Below are magnetograms of this big storm. The first is by Jim Mandaville, A-90, in Arizona, USA. Jim calibrated his magnetometer right after the storm with a Helmholtz coil to check the accuracy of his measurements so the relative field strength in nanoTeslas shown is accurate. Jim had this to say: "The very big (and nearly instantaneous) spike at the beginning of the event near 0100 UT is most striking, and I guess it may mark arrival of the plasma shock front. I think it's the biggest I've ever recorded with total amplitude approaching 600 nT (!)". At about 0600 UT the magnetogram shows a dwell with fluctuations at its lowest point. The fine structure in these fluctuations is shown in the second magnetogram below which was made at a much faster sampling rate and chart speed that spreads the dwell out horizontally to show the fine detail. This second magnetogram was made by amateur seismologest, Meredith Lamb in Denveer Colorado, USA on his diamagnetic seismograph. For a picture of his seismometer log into his web site … http://www.geocities.com/meredithlamb/ … and click on "A diamagnetic seismometer experiment". Here, in his own words, is a description of Meredith's diamagnetic seismograph and how it works:

The seismometer/tiltmeter/magnetometer measures position so its output is a DC signal. The amplifier used here is capable of either a straight DC signal or a "AC" signal, but for normal seismic operation use, the "AC" portion of the amplifier is used, with its bleeder resistors and capacitors controlling the frequency of the output signal and a circuit null. The "mass" on this instrument is a diamagnetically levitated neodymium magnet, which also has a plastic extension with another much smaller neodymium magnet. The actual movement is sensed with a Hall sensor which is adjusted to be over the North-South junctions of the small magnet for maximum sensitivity. This diamagnetically levitated mass being a magnet, it does respond to both seismic waves, tilt, and magnetic outside influences, including large bus's, and the stronger geomagnetic disturbances caused by solar flares/shocks. In the physical sense its a directional "hanging pendulum" and has a limit as to magnetic influences, and can not sustain a displacement from that kind of signal indefinitely, as their is the earth's gravity also competing with any signal upon the magnet. The sensing orientation of the instrument is in a North-South direction. Because the geomagnetic changes are only a side note, there has not been any effort to go further with that; however their is also another web page, with a few samples of some of the latest solar influenced magnetic storms and graphs, and that is at: http://diamagnetic.users2.50megs.com/page061.html

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The chart below is the magnetogram made by Meredith Lamb with his seismograph in which the mass is a bar magnet diamagnetically levitated. The bar magnet lies along a north-south axis so it senses the earth's magnetic field and is displaced along that axis by an amount that depends on the strength of the earth's magnetic field. When the strength of that field changes the bar magnet changes its displacement accordingly moving along the north-south axis. A small sensing magnet is attached by an outrigger to the large levitated bar magnet. The amount of the displacement is detected by a Hall Effect sensor in the magnetic field of the small magnet on the outrigger. The output of the Hall sensor is amplified and recorded as a voltage on a computer to produce a DAT file. An earthquake would produce a very similar DAT file by responding to similar displacement of the bar magnet by the earthquake. In the case of the earthquake, however, it is the Hall sensor that moves in relation to the small magnet on the outrigger rather than the other way around. This happens because the seismic mass stands still while the earth shakes, due to the mass's inertia as a long period pendulum. The amount of shaking is very small from a distant earthquake so a lot of amplification of the Hall sensor's voltage output is needed to make the DAT file. Enough amplification is used to detect a magnitude 5.0 earthquake 4000 to 5000 km away or a magnitude 6.0 anywhere in the world. It is this high magnification that produced the fine detail in the chart below. The actual displacements recorded here probably represents distances measured in micrometers. The DAT file of this small section of the magnetic storm was plotted in "Winquake" which is plotting software used by seismologist to plot earthquakes. The distance between the vertical lines on the recording is thirteen and one half minutes so the chart shows about an hour and a half of activity. The chart is centered on about 06 hours universal time. If you compare this chart to 06 hours on Jim Mandaville's chart on the previous page you can see that it corresponds to the lowest part of Jim's chart at around 0600 UT. If you look close you can also see that the broad outline of both charts are similar at around 0600 UT Both start off going down, then up and then down again. Both charts confirm the same small changes due to the storm but Meredith's chart shows it in much finer detail due to his recording being made at a much faster sampling rate (3.3 sps) and faster chart speed plus considerably more amplification.

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Charts below, on the next page, show more magnetograms made by other observers during March. The first was made by Dr. Walter Moos, A-84, in Switzerland. It is a recording of the same 31March magnetic storm that is shown above and on the previous page.

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Len Anderson, A-91, in South Perth, West Australia, made the SES recording below using NWC at Northwest Cape, West Australia, on 19.8 kHz as his signal source. NWC is about 1000 km due North of South Perth which accounts for the very sharp and short duration sunrise drop at ~2300 UT on 29 March. Time advances from right to left on this chart and later the next UT day, 30 March, a nice SES starts at ~1000 UT but soon gets lost in the sunset drop which starts about one half hour later at ~1030 UT and drops to its lowest level by ~1100 UT. The sunset pattern is broader than the sunrise pattern taking about 1½ hours compared to ~1/2 hour for the sunrise pattern.

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Two multiplexed charts below were made by Jerry Winkler, A-50, on 7 and 9 March. The three signals are 24 kHz, 25.2 kHz and 21.4 kHz in Maine North Dakota and Hawaii respectively. The uppermost signal which is NAA on 24 kHz is the most sensitive and shows multiple SESs both days. Notice how the events are confirmed by showing on more than one trace. A multiplexed chart records SESs with much higher definiteness than a recording of a single signal. This is why A-52's multiplexed recording of gamma ray burst 010222 was seen as a definite recording of the GRB as discussed last month in the February Solar Bulletin.

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Two charts below were made by Casper Hossfield, A-5, on 27 and 28 March, made in Orlando, Florida recording NAA in Maine on 24 kHz. The first chart, 27 March, shows an SES with an unusually sudden rise lasting less than two minutes and starting at exactly 1630 UT so much of the rise is on the time line and hard to see. For such a large SES to last only 30 minutes is also unusual. The 29 March chart shows a more normal SES rising in ~6 minutes and lasting 45 minutes.

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