ELF

Extremely Low Frequency, сокр. ELF [elf]
крайне низкая частота, КНЧ
1. Диапазон частот в пределах 0,3 – 3 кГц.
♦ Extremely low frequency (ELF) is the ITU designation for electromagnetic radiation (radio waves) with frequencies from 3 to 30 Hz, and corresponding wavelengths of 100,000 to 10,000 kilometers, respectively.
2. Диапазон частот в пределах 3 Гц – 3 кГц.
♦ In atmospheric science, an alternative definition is usually given, from 3 Hz to 3 kHz.
extremely low-frequency waves — декамегаметровые волны (Синонимы decamegametric waves)
3. Диапазон частот в пределах до 3 Гц.
♦ In the related magnetosphere science, the lower frequency electromagnetic oscillations (pulsations occurring below ~3 Hz) are considered to lie in the ULF range, which is thus also defined differently from the ITU radio bands.
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— Игорь Мостицкий (обсуждение) 13:51, 9 января 2026 (MSK)