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 - Článek v odborném periodiku
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
Grant CEP: GA MŠMT ME09107; GA ČR GA205/09/1253
Grant ostatní: AV ČR(CZ) M100420902; AV ČR(CZ) M100420903
Program: M
Výzkumný záměr: CEZ:AV0Z30420517
Klíčová slova: DEMETER * midlatitude ionosphere * spectrograms
Kód oboru RIV: BL - Fyzika plazmatu a výboje v plynech
Impakt faktor: 3.303, rok: 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.
Trvalý link: http://hdl.handle.net/11104/0185825