Halo Observations from the Ground and from Space: Further Checks on the Sprite Polarity Paradox
Abstract
In continuing efforts to verify the hypothesis that halos produced by negative polarity ground flashes provide a resolution to the ‘sprite polarity paradox’ and are caused by the fast initial charge transfer in the lightning return stroke, additional halo observations are considered from the ground and from space. The ground-based observations include standard frame-rate video cameras, a high-time resolution (40 microsec)) photometer (called PIPER), the National Lightning Detection Network (NLDN), and ELF charge moment observations from Nagycenk Observatory in Hungary. The space-based observations are measurements from the limb-viewing ISUAL satellite. The observations in support of the hypothesis are: (1) charge moments of the same magnitude required for sprites are evident for ‘negative’ halos, (2) negative halos outnumber positive halos in both ISUAL and PIPER observations, (3) short (<10 msec) continuing currents are abundant in negative ground flashes and scarce in positive ground flashes, and (4) halo brightnesses are (weakly) correlated with ELF charge moment (ISUAL brightnesses) and with NLDN peak current (PIPER brightnesses). The consistently dimmer negative halos in ground-based observations (PIPER) are consistent with claims that they are systematically missed in observations with conventional frame-rate cameras. Inconsistencies and problems with the working hypothesis are (1) ISUAL peak lightning brightnesses are no larger for negative than for positive halo-parent lightning flashes, (2) NLDN peak currents for brighter ‘positive’ halos are not notably larger than for dimmer ‘negative’ flashes, and (3) ELF measurements of charge moments for negative flashes tend to be greater than for positive flashes. An additional similarity between ground- and space-based observations is the tendency for halos to be produced by single-stroke negative flashes, a distinct departure from the statistics of stroke multiplicity for all negative flashes with large peak current. The reason for the polarity asymmetry in the parent lightning flash, at the origin of the sprite polarity asymmetry, remains an open question.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2009
- Bibcode:
- 2009AGUFMAE33A0289W
- Keywords:
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- 0342 ATMOSPHERIC COMPOSITION AND STRUCTURE / Middle atmosphere: energy deposition;
- 0654 ELECTROMAGNETICS / Plasmas;
- 3304 ATMOSPHERIC PROCESSES / Atmospheric electricity;
- 6929 RADIO SCIENCE / Ionospheric physics