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VLF‐HF HEATING OF THE LOWER IONOSPHERE AND ELF WAVE GENERATION
Author(s) -
Taranenko Y. N.,
Inan U. S.,
Bell T. F.
Publication year - 1992
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/91gl02771
Subject(s) - ionosphere , physics , dipole , f region , geophysics , very low frequency , modulation (music) , high frequency , atmospheric sciences , computational physics , acoustics , quantum mechanics , astronomy
For incident wave power densities of 10 −6 – 10 −2 W/m 2 (at 30 km altitude), VLF heating of the D‐region (< 90 km) is found to be 2–10 times more effective (depending on power) than HF heating, resulting in comparable perturbations of subionospheric VLF probe waves in spite of up to 10 3 times larger power density utilized in HF heating and at least as efficient in ELF wave generation. In view of generally larger (100×100 km) areas of the ionosphere illuminated by VLF transmitters, ELF wave generation by modulated VLF heating is estimated to produce ELF power levels of ∼100 mW, comparable with or larger than those produced in typical HF heating experiments. ELF wave generation in a typical midlatitude ambient ionosphere occurs primarily via the modulation of Pedersen current whereas in a typical auroral ionosphere Hall current is dominant for pump wave frequencies up to ∼6 MHz. For 10–30 MHz and power densities > 10 −4 W/m 2 , Pedersen current modulation is again dominant, potentially providing up to 2–15 times higher ELF dipole moment than those found in recent experiments using 3–5 MHz heaters.