SRC-104

Ionospheric interactions with high-power microwave beams, ESA/University of Leicester review

Commissioned by European Space Agency. Who paid for a study is recorded because it bears on how its conclusions should be read, not because it makes them wrong.

Published claims resting on this source

• CLM-0042 The 230 watts per square metre figure applies to one frequency and one design lineage. Japanese designs at a higher frequency allow up to about eight times as much.
• CLM-0057 There is a formula for the instability threshold. It depends on electron density cubed, electron temperature to the fourth power, and frequency cubed, and it has no single value because it assumes how far the beam travels while the instability grows.
• CLM-0059 The two fields were largely the same people from the 1970s, and papers linking them were still appearing after 1991.
• CLM-0075 When ESA revisited the question in 2004 it used the 1978 theory and did not cite the 1979-81 Platteville tests or NASA's 1981 revision of the figure.
• CLM-0079 The 1978 paper modelled both a ground facility and a satellite case, and its 500 watts per square metre figure is a power flux for a given temperature rise, not a power rating.
• CLM-0083 The formula is the right type but nobody has said how far it can be pushed, and at space solar power frequencies the wave is about 200 times the plasma frequency. The field's own 2007 review says the case is unclear.
• CLM-0108 A 2004 ESA review found that during the October 2003 solar storm, just under 20 per cent of a space solar power beam would have been absorbed before reaching the ground. In quiet conditions the loss is under 0.3 per cent.
• CLM-0109 In normal conditions the ionosphere takes essentially none of the beam. In a severe solar storm it could take a little under a fifth of it.
• CLM-0130 The quiet-condition absorption figures from four sources do not disagree. One of them states an upper bound and the others sit inside it.
• CLM-0131 Even the most extreme kind of sudden, lightning-caused heating of the upper atmosphere considered in this 2004 study would only block about 3% of a space solar power beam, at most.
• CLM-0137 In four major space solar power studies from 1978 to 2007, none put a number on how much of the beam's energy would be lost if the beam sets up fine stripes of uneven density in the upper atmosphere; they mention the concern but do not measure or calculate it.
• CLM-0158 Neither of the two sources read at the page, a 2004 review by Robinson and others and Gurevich (2007), states the range of conditions under which this 1981 low-frequency theory is valid at the much higher microwave frequencies space solar power plans to use; the 2004 review applies a similar formula at 2.48 and 5.8 gigahertz without stating one.
• CLM-0161 Satellite-link observations show that natural disturbances in the upper atmosphere can make a 2.48 GHz radio signal's strength swing by close to 100%; these disturbances are worst near the equator and the poles, and Western Europe is less affected except in rare severe conditions.
• CLM-0401 A 2004 review calculated that, under some of the most extreme conditions measured during a large solar storm in October 2003, only just over four fifths of a microwave power beam would get through the ionosphere and atmosphere to the ground, against more than 99.7 per cent normally. The storm lasted more than a day, but conditions varied, so a loss that large probably (our inference) did not last throughout. The standard 1978 efficiency figures include no allowance for it.

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