Value chain · CLM-1012
In plain terms
In the DOE's 1980 summary the Platteville heating tests showed no effect on the navigation and broadcast radio it listed at the beam's equivalent strength (a separate 1980 report on the trials records cross-modulation on time-signal stations and one AM station), warmed the lower ionosphere by roughly the amount theory predicted, but did not produce the density change the same theory predicted. The programme concluded 23 was safe for these systems and said bigger facilities were needed to find the ceiling.
The claim as recorded
The DOE 1980 summary reports that Platteville at 5 MHz delivered SPS-comparable ohmic heating to a lower-ionosphere region 30 km across at 75 km and 40 km at 100 km, three to four times the SPS beam footprint; that about 40 hr of OMEGA VLF, 19 plus 13 hr of Fallon and 35 hr of Dana LORAN-C LF, and 11 AM MF stations showed no change attributable to heating - of which 8 were local stations whose groundwave swamped any skywave, so the usable skywave null is the 3 remote paths; that diagnostics showed electron temperature raised "from a background level of 200 K to between 300 K and 500 K", matching theory for a 23 mW/cm2 beam, but that the same theory's predicted "increases in electron density of 10-15%" were not seen; and concludes that the SPS "as currently configured with a peak power density of 23 mW/cm2, would not adversely affect the performance of these telecommunication systems" while "additional experiments with more-powerful facilities are required to establish the maximum".
Evidence behind this: T3-programme summary of measured telecommunications and diagnostic results at Platteville.
Scope and limits
About 107 hours of recording in total across three bands, during a period the source says included solar flares that "far exceeded any possible changes induced by intentional ionospheric heating". A null result at SPS-equivalent density says nothing about density above it, which the source says explicitly. A separate 1980 report on the same trials (SRC-110, CLM-0102) records cross-modulation on WWVB, WWV and a civil AM station. The D-region theory-data mismatch is the source's "seem to indicate", not a measurement of density.
What it assumes
The 1/f^2 ohmic scaling from 5 MHz to 2.45 GHz (DRAFT-XC03-G).
Where it comes from
p.94 / 84: "SPS-comparable power density at 5 MHz to an area of the lower ionosphere that is 30 km in diameter at an altitude of 75 km and 40 km in diameter at 100 km. This area is three to four times larger than that anticipated for the SPS microwave beam". p.95 / 85: "Approximately 40 hr of recordings ... there were no observable changes in the OMEGA"; "Approximately 19 hr of relative phase data and 13 hr of relative phase and amplitude recordings ... About 35 hr ... from the Indiana station." p.96 / 86, render read: "The electron temperature above Platteville can be raised from a background level of 200 K to between 300 K and 500 K ... corresponds very closely to recent theoretical calculations of changes in D-region electron temperatures due to the passage of a 23-mW/cm2 SPS power beam. The same studies show, however, that increases in electron density of 10-15% should accompany the electron temperature increases." "Both the diagnostic and telecommunications data seem to indicate that electron density in the lower ionosphere was not changed appreciably". p.101 / 91: "the SPS, as currently configured with a peak power density of 23 mW/cm2, would not adversely affect the performance of these telecommunication systems. Continued theoretical work and additional experiments with more-powerful facilities are required to establish the maximum microwave power density".
Basis: hours of recording; K electron temperature; per cent electron density
Related records
- Answers question
- QST-009 not published in this release
Cite this
energyaperture.com/c/clm-1012
CLM-1012, Energy Aperture, as of 1980-08.
Connected records
Other published records linked to this one. A list, not a judgement.
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- Also from SRC-529
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