A Holographic Array for Ionospheric Lightning (HAIL) Research
STANFORD UNIV CA DEPT OF ELECTRICAL ENGINEERING
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Recently, VLF remote sensing has emerged as a powerful tool for imaging of ionospheric disturbances. In particular, the strip holography technique e.g., Chen et al., Radio Science, vol. 31, p.335, 1996 is a method by which the relative amplitude and phase changes at a series of VLF receivers are combined to yield a volumetric profile of the scattering region. Previous studies have been done for certain cases where a storm happened to pass through the junction between two transmitter-receiver paths, but the strip holography simulation demonstrated that an array of appropriately spaced receivers would be able to image disturbances over a wider range of land area. With this array now operating in the field, these past techniques and models will be applied towards the new data in the hope of improving the understanding of the occurrence distribution and characteristics of ionospheric disturbances. Interpretation of VLF remotely sensed disturbances has been greatly enhanced through parallel optical recordings of transient heating and ionization events, in particular those named sprites and elves. Understanding the processes behind these events is crucial to interpreting their distribution and importance for VLF communication, electrical and chemical processes in the lower ionosphere, and the nature of the global electrical cycle. Optical measurements, coupled with VLF broadband recordings, are an integral part of the HAIL campaigns and of a full interpretation of the coupling between lightning and the environmental factors affecting VLF propagation.
- Atmospheric Physics
- Radiofrequency Wave Propagation