During the FORTE project it was observed that the most powerful intra-cloud radio emissions tend to be unpolarized, in comparison with the much weaker intracloud leader-step emissions [Jacobson and Light, 2003]. This suggestion relied on eyeballing data, rather than on applying the polarimetry method formally and systematically to a statistically meaningful dataset of intracloud-lightning VHF emissions. Thus trends could never be formally assessed. We have now addressed, and to some extent overcome, certain technical difficulties posed by mass application of VHF polarimetry. It is now possible for a large dataset of lightning VHF recordings by FORTE to be systematically analyzed for polarization state, making available further information pertinent to emission geometry. We will present preliminary findings on implications for emitter geometry, complexity, and coherence.
Acknowledgements: ARJ and RH are partially supported by the DARPA Nimbus program. X-MS participates under the auspices of the USDOE.
Jacobson, A. R., S. O. Knox, R. Franz, and D. C. Enemark (1999), FORTE observations of lightning radio-frequency signatures: Capabilities and basic results, Radio Sci., 34(2), 337-354. Jacobson, A. R., and T. E. L. Light (2003), Bimodal radiofrequency pulse distribution of intracloud-lightning signals recorded by the FORTE satellite, J. Geophys. Res., 108(D9), 4266, doi:4210.1029/2002JD002613. Shao, X.-M., and A. R. Jacobson (2001), Polarization observations of broadband VHF signals by the FORTE satellite, Radio Sci., 36(6), 1573-1589. Shao, X.-M., and A. R. Jacobson (2002), Polarization observations of lightning-produced VHF emissions by the FORTE satellite, J. Geophys. Res., 107(D20), 4430.