On the Origin of Ionospheric Hiss: A Conjugate Observation




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Amer Geophysical Union



We present a conjugate observation on whistler mode electromagnetic hiss from the low Earth orbit satellite Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions (DEMETER) and the high-altitude elliptical orbit spacecraft Time History of Events and Macroscale Interactions during Substorms (THEMIS). The conjugate observation was performed at 14:51:10 to 15:12:00 UT on 15 June 2010, when DEMETER was flying across the L shell region from ~1.39 to 2.80 at an altitude of ~660 km; meanwhile, THEMIS probes were passing through the L shell region from ~1.64 to 1.91 at altitudes from ~1.6 to 2.0 R_E. The conjugated observations demonstrate similar time-frequency structures between the ionospheric hiss (~350 to 800 Hz) captured by DEMETER and the plasmaspheric hiss (~350 to 900 Hz) recorded by THEMIS probes, including similar peak frequencies (~500 to 600 Hz), similar lower cutoff frequencies (~350 to 400 Hz), and upper cutoff frequencies (~730 to 800 Hz). The wave vector analyses show that the ionospheric hiss propagates obliquely downward to the Earth and slightly equatorward with right-handed polarization, suggesting that its source comes from higher altitudes. Ray tracing simulations with the constraint of observations verify that the connection between ionospheric and plasmaspheric hiss is physically possible through wave propagation. This study provides direct observational evidence to support the mechanism that high-altitude plasmaspheric hiss is responsible for the generation of low-altitude ionospheric hiss.



Ionosphere--Hiss (Radio meteorology), Radiation, Plasmasphere--Hiss (Radio meterorology, Magnetic fields, Electrons


"This work was supported by the NSFC grants 41574139, 41204136, and 41674164; ISTCP 2014DFR21280, the APSCO‐SP/PM‐EARTHQUAKE Project and ISSI‐BJ project, and the Fundamental Research Funds for earthquake research 2014IES010203. Lunjin Chen acknowledges the support of NSF grant AGS 1405041."


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