Journal notes, Comparing to USGS plots, Geomagnetic Indices
GELLER Labs "Backyard Science"
Thoughts on a proton precession magnetometer design - a Proton Magnetometer Project. Build an Earth's field magnetometer.
The FDM MAGNETOMETER1 project is a low cost high performance proton magnetometer (a digital magnetometer) kit under development for amateur scientists to be able to accurately measure and monitor changes in the Earth's total magnetic F field and to observe geomagnetic storms. Magnetic storms can cause large excursions in the field and are of concern to interests ranging from electrical power grids, radio communications, and satellite operations, to aurora watchers and amateur radio operators.
1 Filter Diagonalization Method "FDM" (harmonic inversion), see Jan 21 and Jan 23 entries, based on: Vladimir A. Mandelshtam, Howard S. Taylor, Harmonic inversion of time signals and its applications, Journal of Chemical Physics (1997), Volume 107, Issue 17, 1997, Pages 6756-6769
(be sure to hit refresh to pick up our latest changes and entries)
Friday, June 18, 2010
Overnight: PDF, TXT, USGS PDF. The local geomagnetic field has been relatively quiet overnight and this morning.
More project documentation: Here is a flow chart of our polarization and digitization timing: PDF (showing the time delay values presently in use). Recall from our earlier discussion that an important aspect of our relatively simple low cost approach is that we are able to use a high quality small signal relay by closing or opening the relay only under zero-current conditions (no contact arcing). Also, we power the dump resistor while powering the one powered coil of the counter-wound pair, so no additional switching is needed to fast-discharge the coil once the polarization FET is turned off, since the coil naturally dumps its remaining energy into the dump resistor via the RLC elements of the cable, the switching circuit, and the dump R. The relay with its ~1 picofarad of coupling capacitance between contacts, is highly desirable in this application to isolate the polarization circuit from the ultra-high gain analog amplifier. Also, with the high isolation offered by a small signal relay, active shorting of the amplifier input during a polarization cycle is not needed.
Saturday, June 19, 2010
Fortunately, we see relatively few relatively large offsets caused by vehicles within about 100 ft to 300 ft (very roughly within an outer range of about 100 meters). However, there are busier times as seen in this PDF. The multi close-in vehicle problem can cause one ultimately to lose the absolute baseline. Here, one vehicle arrived before the displayed plot, and there were three relatively large excursions. Also, there was probably a distant fourth departure and arrival between 10 am and 12 pm. An amateur observer in a neighborhood with very small lots and/or with dense on street parking should expect some challenges. On the other hand, our daily presentation typically uses a relatively sensitive scale of 5 nT / vertical division, so it would still be easy to identify disturbances on the order of K=5 or a geomagnetic storm of G1 or greater.
Sunday, June 20, 2010
Overnight: PDF, TXT, USGS PDF, relatively quiet overnight and this morning, nice view of a morning diurnal cycle.
evening: while still a quiet couple of days, another series of relatively small disturbances were seen nationwide this evening. Interesting that our plots here in upstate, NY are more closely following the more distant Stennis, MS BSL station than the closer FRD Corbin, VA site: PDF, USGS PDF. Some of the apparent differences (FRD/BSL) might be due to the different vertical scales between the two station plots.
Monday, June 21, 2010
Overnight: PDF, TXT, USGS PDF, another series of small disturbances at around 3 am EST. As before, we have compressed our vertical axis PDF for a visual comparison with the USGS data, and our horizontal axis is somewhat shorter with out portrait page orientation. This time out local field activity seems a bit closer to that of the FRD station. Also the short negative spike at the end of the first pulse seems slightly different than most other observations. I suppose it could have been a passing vehicle, although that would have been quite a coincidence. Our TXT files now include only plotted points without the failed auto-retry measurements.
Interesting how fast the field goes from quiet to slightly active, then back to quiet again ... PDF, USGS PDF.
Tuesday, June 22, 2010
Overnight: PDF, TXT, USGS PDF.
Saturday, June 26, 2010
Overnight: PDF, TXT, USGS PDF. 20 nT / vertical division seems good for visual comparison to the USGS plots (we are UTC -4 hours (US Eastern Daylight Savings Time)). The FDM magentometer resolves to better than 0.1 nT, we often run at 5 nT / vertical division, but those graphs have so much detail, it is difficult to visually compare them the to the USGS plots.
Here is a very helpful table of the Geomagnetic K index, which discusses the K-index, the relationship between K, Kp, and estimated Kp, the relationship between K and A, and the relationship between the NOAA G-scale and Kp.
I can never remember where the K index table is; it can be found from the NOAA Boulder Magnetometer webpage, which is linked to the NOAA / Space Weather Prediction Center Space Weather Alerts, Geomagnetic K-indices web page.
Alerts are at the NOAA / Space Weather Prediction Center,Space Weather Alerts page. Also, check the Costello Geomagnetic Activity Index prediction.
Project Documentation (very early stages)
QUESTIONS/COMMENTS/notice of typos, etc. send email to joegeller @ gellerlabs dot com
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