Remote Sensing of TLEs by Satellite ELF/VLF Wave Measurements
Résumé
First recordings of satellite ELF/VLF waveform data associated with TLE observations are reported from the Summer 2005 campaign coordinated by Stanford University and LPCE. TLEs are optically observed from the US Langmuir Laboratory, while ELF/VLF waveform data are simultaneously recorded on-board the CNES microsatellite DEMETER and on the ground at Langmuir. Analyses of ELF/VLF measurements associated with two sprite events observed on July 28 2005 around 05:02:45 UT are presented. Conditions to trace back the wave emissions from the satellite to the entry point within the ionosphere are discussed. The main results concern: (i) the identification from a low Earth orbit satellite of the 0+ whistler signatures of the causative lightning, (ii) the identification of the propagation characteristics of proton whistlers triggered by the 0+ whistlers of the causative lightning, and the potential use of those characteristics to identify longitudinal or quasi-longitudinal 0+ whistlers, (iii) the difficulty to observe sprite-produced ELF bursts in the presence of proton-whistlers, (iv) an optimum transfer of energy from the atmosphere to the ionosphere for waves with wave normals anti-parallel to the Earth magnetic field direction at the altitude of the X= fpe2/f2 =1 plasma cut- off, with fpe the local plasma frequency.