Value chain · CLM-0146
In plain terms
A 1975 Soviet theory paper calculated an exact minimum radio-wave strength - about 300 millivolts per metre in daytime, ten times less at night - below which a specific kind of upper-atmosphere plasma instability simply does not start.
The claim as recorded
Vas'kov and Gurevich (1975) give an explicit, numeric hard threshold field for the parametric instability of Langmuir/ion-acoustic waves near the F-region reflection point: Et,min about 300 mV/m by day and about 30 mV/m at night at heights of 200-250 km, rising to 3-4 times higher at the F-layer peak; below this field their kinetic-regime treatment shows the instability does not grow at all.
Scope and limits
A threshold for the PARAMETRIC instability specifically, not for the self-focusing instability itself, which the same paper treats as having no comparably sharp field threshold (an already-recorded finding). Must not be quoted as if it were a self-focusing threshold.
What it assumes
This threshold is for HF ionospheric-heater physics (ground transmitters reflecting near the F-layer), a different propagation regime from underdense GHz microwave transmission; direct numeric comparison to a GHz-band threshold formula is not warranted without further work.
Where it comes from
Vas'kov and Gurevich (1975), Sov. Phys. Usp. 17(4), p.614: "Under the conditions of the ionosphere, the field Et for an ordinary wave is smallest at heights h ~ 200-250 km: during the day, Et,min ~ 300 mV/m and omega_min ~ 3 x 10^7 Hz; at night, Et,min ~ 30 mV/m and omega_min ~ 6 x 10^6 Hz. At the height of the F-layer maximum, the field Et is 3-4 times larger than Et,min."
Basis: electric field threshold, mV/m, F-region heights ~200-300 km, HF ordinary-wave heating
Related records
- Answers question
- QST-001 not published in this release
Cite this
energyaperture.com/c/clm-0146
CLM-0146, Energy Aperture, as of 1975.
Connected records
Other published records linked to this one. A list, not a judgement.
- Also from SRC-133
- CLM-0114The Russian treatment says self-focusing is triggered by lumpiness already present in the ionosphere, not by beam power crossing a line...CLM-0115The Russian and American researchers were talking to each other from at least 1974, so they are not two fully independent traditions.CLM-0116The Russian formulas are a different shape from the 0.43 relation, so they cannot be used to check it either way.