On the origin of lower- and upper-frequency cutoffs on wedge-like spectrograms observed by DEMETER in the midlatitude ionosphere

0343319 - ÚFA 2011 RIV US eng J - Journal Article
Shklyar, D. R. - Parrot, M. - Chum, Jaroslav - Santolík, Ondřej - Titova, E. E.
On the origin of lower- and upper-frequency cutoffs on wedge-like spectrograms observed by DEMETER in the midlatitude ionosphere.
Journal of Geophysical Research. Roč. 115, - (2010), A05203/1-A05203/12. ISSN 0148-0227
R&D Projects: GA MŠMT ME09107; GA ČR GA205/09/1253
Grant - others:AV ČR(CZ) M100420902; AV ČR(CZ) M100420903
Program: M
Institutional research plan: CEZ:AV0Z30420517
Keywords : DEMETER * midlatitude ionosphere * spectrograms
Subject RIV: BL - Plasma and Gas Discharge Physics
Impact factor: 3.303, year: 2010

We report observations of unusual lower and upper cutoff frequencies on VLF spectrograms recorded by the DEMETER satellite orbiting at 700 km. The upper cutoff frequencies vary approximately in proportion to L-3. The lower cutoff frequencies in the spectrograms are almost constant. Between these cutoffs, which form a wedge, intense whistlers are observed, whereas only 0+ whistlers, and probably, ducted whistlers are present outside the cutoffs. We explain the observed spectrograms on the basis of the features of whistler-mode wave propagation in the inner magnetosphere. The upper cutoff frequency is determined by the limiting trajectories that confine the waves of a given frequency propagating obliquely from a source located in the opposite hemisphere. The lower frequency cutoff is determined by the LHR maximum, since quasiresonant waves with lower frequencies originating in the opposite hemisphere do not reach the satellite due to the LHR reflection above it.
Permanent Link: http://hdl.handle.net/11104/0185825