Propagation of the Lightning Electromagnetic Pulse Through the E- and F-region Ionosphere and the Generation of Parallel Electric Fields
Abstract
Sounding rockets launched by Mike Kelley and his group at Cornell demonstrated the existence of transient (1 ms) electric fields associated with lightning strikes at high altitudes above active thunderstorms. These electric fields had a component parallel to the Earth's magnetic field, and were unipolar and large in amplitude. They were thought to be strong enough to energize electrons and generate strong turbulence as the beams thermalized. The parallel electric fields were observed on multiple flights, but high time resolution measurements were not made within 100 km horizontal distance of lightning strokes, where the electric fields are largest. In 2000 the ``Lightning Bolt'' sounding rocket (NASA 27.143) was launched directly over an active thunderstorm to an apogee near 300 km. The sounding rocket was equipped with sensitive electric and magnetic field instruments as well as a photometer and electrostatic analyser for measuring accelerated electrons. The electric and magnetic fields were sampled at 10 million samples per second, letting us fully resolve the structure of the parallel electric field pulse up to and beyond the plasma frequency. We will present results from the Lightning Bolt mission, concentrating on the parallel electric field pulses that arrive before the lower-frequency whistler wave modes. We observe pulses with peak electric fields of a few mV/m lasting for a substantial fraction of a millisecond. Superimposed on this is high-frequency turbulence, comparable in amplitude to the pulse itself. This is the first direct observation of this structure in the parallel electric field, within 100 km horizontal distance of the lightning stroke. We will present evidence for the method of generation of these parallel fields, and discuss their probable effect on ionospheric electrons.
- Publication:
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AGU Spring Meeting Abstracts
- Pub Date:
- May 2004
- Bibcode:
- 2004AGUSMSA33A..03R
- Keywords:
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- 2411 Electric fields (2712);
- 2451 Particle acceleration;
- 2471 Plasma waves and instabilities;
- 2487 Wave propagation (6934);
- 6934 Ionospheric propagation (2487)