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Abstract The powerful high‐frequency/very high frequency radio emissions that occur during lightning flashes can be used as a signal of opportunity to study the bottom side ionosphere. The lightning emission is bright, broad spectrum, and short in duration, providing an ideal signal of opportunity for making ionograms. This study continues previous work in Obenberger et al. (2018), where the direct line of sight signal from lightning can be cross correlated with megahertz frequency radio telescope observations to reveal ionogram traces created from the reflected lightning signals. This process was further developed to automate production of ionograms made from individual lightning flashes over the course of several hours, as well as create new techniques to detect the lightning signal using the all‐sky‐imaging mode. By using the Long Wavelength Array Sevilleta radio telescope as an interferometer, the point of reflection of the lightning signal for each frequency of the ionogram can be located in the ionosphere, instantaneously revealing density gradients within the ionosphere on minute time scales. We also explore the minimum size stations required for the application of this technique, which we found to be at least 32 antennas.
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Lightning Interferometry with the Long Wavelength Array
The Long Wavelength Array is a radio telescope array located at the Sevilleta National Wildlife Refuge in La Joya, New Mexico, well suited and situated for the observation of lightning. The array consists of 256 high-sensitivity dual polarization antennas arranged in a 100 m diameter. This paper demonstrates some of the capabilities that the array brings to the study of lightning. Once 32 or more antennas are used to image lightning radio sources, virtually every integration period longer than the impulse response of the array includes at least one identifiable lightning emitter, independent of the integration period used. The use of many antennas also allows multiple simultaneous lightning radio sources to be imaged at sub-microsecond timescales; for the flash examined, 51% of the images contained more than one lightning source. Finally, by using many antennas to image lightning sources, the array is capable of locating sources fainter than the galactic background radio noise level, yielding possibly the most sensitive radio maps of lightning to date. This incredible sensitivity enables, for the first time, the emissions originating from the positive leader tips of natural in-cloud lightning to be detected and located. The tip emission is distinctly different from needle emission and is most likely due to positive breakdown.
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- PAR ID:
- 10470494
- Publisher / Repository:
- remote sensing
- Date Published:
- Journal Name:
- Remote Sensing
- Volume:
- 15
- Issue:
- 14
- ISSN:
- 2072-4292
- Page Range / eLocation ID:
- 3657
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.3390/rs15143657
