Observations of the coupling efficiency of VLF lightning-generated whistlers into the low-latitude plasmasphere

Abstract:

The C/NOFS satellite [de La Beaujardiere, 2004] has provided a vast archive of multi-sensor data on the low-latitude ionosphere/plasmasphere since 2008. As part of the project, the VEFI payload [Pfaff et al., 2010] has recorded the 3-D electric field from DC through 16 kHz with high fidelity. The relative calibrations track between the three E-field antennas with sufficient accuracy and stability to allow retrieval of the wave polarization for a wide range of lightning-generated whistler waves [Jacobson et al., 2014]. The wave polarization in turn allows retrieval of the wavevector (within a sign ambiguity), which in turn allows an inverse-raytrace of the whistler raypath from the satellite to the ionospheric entry point. We will compare the raytrace predictions with ground-truth from the WWLLN global lightning-monitoring system [Lay et al., 2004; Rodger et al., 2005; Rodger et al., 2004]. In addition to providing location and time of lightning strokes, WWLLN provides an estimate of the radiated radio energy in the whistler passband [Hutchins et al., 2012]. Finally, the CINDI payload [Heelis et al., 2009] on C/NOFS provides ion composition at the satellite, permitting the index of refraction to be inferred. We will compare these estimates to the Poynting fluence density observed by VEFI, thereby providing a direct test of the coupling of lightning radio energy into plasmaspheric whistlers.