Journal notes, August, 2010 G2 Geomagnetic Storm
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 universities and 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)
Project Documentation (very early stages)
Journal Notes:
Tuesday, August 3, 2010
G2 GEOMAGNETIC STORM - The Costello Geomagnetic Activity Index showed an increase in activity PDF. The NOAA Space Weather page ratcheted up all day from a warning through K4 to G1 PDF. The NOAA K indices page PDF (based on several hour averages?) is beginning to light up as well.
Afternoon/evening: PDF, NRCan OTT The first event, apparently an "impulse" was felt as a just over 10 nT pulse here in upstate, NY, followed by a relatively large positive excursion in the field of almost 100 nT. Another large relatively fast excursion PDF, NRCan OTT PDF, USGS PDF. Still more fast changes follow PDF. This G1 geomagnetic storm appears to be winding down now (10 pm) PDF. Now being called a G2 geomagnetic storm PDF. Three more pulses, but nothing like the large excursions seen last evening from about 5 pm to 9 pm PDF.
Wednesday, August 4 , 2010
Overnight: PDF, TXT, another fast transition after 6 am EST, otherwise the geomagnetic field is still somewhat active, but nothing like last evening that early am period (see August 3 entry). It continues to be the case that our data PDF is in close agreement with the NRCan OTT observatory PDF, and less so with the more distant USGS observatories PDF. Comparing yesterday to today in one magnetogram (it is still somewhat active) PDF.
PART II of our series of articles is now available! As always, comments and corrections are welcome joegeller at gellerlabs dot com.
Thursday, August 5 , 2010
Overnight: PDF, TXT. The geomagnetic field was very quiet overnight here in upstate, NY.
I have not had a chance to try out the NI Application Builder which would allow our FDM magnetometer to run on machines -without- needing an installed copy of the LabView development system. Upgraded to LabView 2010 last evening under our annual NI software support contract, all seems well. We used a lot of NI tech support time last year and earlier this year, and LabView 2009 has been invaluable to this R&D effort. Also I need to add I/O FDM to the executable module for users to be able to configure it for a particular location (e.g. for setting the intended 300 Hz window for a given geographic location).
Next short term job is to mount the analog PCB in a much smaller Hammond cast aluminum box (1590BB). Then it's on to laying out the digital control board for the zero current FET-Relay hybrid switching scheme (presently running on a handwired prototype).
New pictures of the prototype - working FDM magnetometer prototype: JPG1, JPG2
Friday, August 6 , 2010
Overnight: PDF, TXT, all was quiet overnight.
Some months back, we chose Prestone De-Icer (or RainX De-Icer) windshield washer fluid as our working proton magnetometer fluid following an evaluation of a number of organic fluids for fall time (related to tau 2, the NMR transverse or spin-spin relaxation time) and FID amplitude (See our November 25, 2009 entry on fluid testing). In fact, just about every liquid that we tried produced a usable FID. While that finding would likely seem unremarkable to a chemist or NMR/MRI specialist, we had previously been under the impression that only the most pure distilled water or solvent (e.g. alcohol) or fuel (e.g. kerosene, benzene, charcoal lighter fluid, etc) would work in a proton magnetometer.
Prestone De-Icer provides a good comprise of duration of the FID (free induction decay) signal and amplitude as well as an ability to survive our upstate NY winter without freezing in temperatures as low as -20F to -30F. Freezing is mostly problematic in terms of undesired expansion and container breakage, however we have also not yet explored solid state NMR and how much signal is available in the solid state (another text book on the list for summer reading).
As we came out of winter through spring and now into summer, long term readers will also recall that I have been commenting from time to time on how we see higher amplitude FID signals on cooler days. Since the Larmor gyromagetic ratio does not vary with temperature, there is no error in the field calculation. Also, since we updated our FDM module to choose the highest spectral component, absolute amplitude is no longer much of a concern as long we do not saturate the digitizer (with resulting distortion) or fall down too far in the dynamic range of the digitizer scale where we would loose effective bits.
This evening a relatively fast run was done over some tens of minutes with a measurement cycle of about nine seconds. First we ran on the existing sample that has been at the sensor for some many months now. That bottle was at at temperature of about 30 C (inside the polarization coil of the counter-wound coil pair). Then, about half way through the run, we changed out the sample with another 125 mL bottle of Prestone De-Icer from the same source bottle that had been pre-cooled to about -10 C. Here is the raw data, all TXT, selected for the plot TXT (as meeting our plotting criterion, see the auto-retry flow chart from the docs page) PDF. The large excursion is from me using the IR thermometer near the sensor (the sensor package was at about 19C to 21C).
There were clearly changes in the precession waveform filtered envelope (higher amplitude, faster fall times) PDF1, PDF2. Also, there was a distinct increase in the average amplitude of the FID signal PDF. The zeros mark where the 30 C sample was replaced by the -10 C sample. Less clear, was whether there was any significant change in the average FOM (figure of merit) PDF. These changes with temperature remain a curiosity, however appear to have little or no affect on the overall operation of the FDM magnetometer. Since the polarization power supply was running in a cross-over mode (to constant current during the polarization pulse), it is unlikely that changes in coil temperature, caused by the relatively cold sample bottle, caused the change in FID amplitude. (Afternote: I am told that the temperature dependence of tau 2 is well described by fundamental NMR equations. More reading for another day.)
Project Documentation (very early stages)
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