Premium
Propagation properties of quasiperiodic VLF emissions observed by the DEMETER spacecraft
Author(s) -
Hayosh Mykhaylo,
Němec František,
Santolík Ondřej,
Parrot Michel
Publication year - 2016
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 - 10.1002/2015gl067373
Subject(s) - quasiperiodic function , earth's magnetic field , geophysics , magnetosphere , ionosphere , atmospheric sciences , middle latitudes , geomagnetic latitude , physics , equator , latitude , very low frequency , geology , magnetic field , geodesy , astronomy , quantum mechanics , condensed matter physics
Quasiperiodic (QP) emissions are electromagnetic waves in the frequency range of about 0.5–4 kHz observed in the inner magnetosphere that exhibit a periodic time modulation of the wave intensity, with modulation periods from a few seconds up to 10 min. We present results of a detailed wave analysis of nearly 200 events measured by the low‐altitude Detection of Electro‐Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) spacecraft. Upper frequency range of studied emissions was limited to 1 kHz due to the sampling rate of the analyzed data. It is found that QP emissions propagate nearly field aligned at larger geomagnetic latitudes; they become more oblique at midlatitudes and eventually perpendicular to the ambient magnetic field at the geomagnetic equator and thus perpendicular to the Earth's surface, allowing their downward propagation through the ionosphere. The observed propagation pattern is consistent with the source of emissions located in the equatorial region at larger radial distances.