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| Titel |
VLF sferics associated with TGFs |
| VerfasserIn |
Andrew Mezentsev, Nikolai Østgaard, Thomas Gjesteland, Alexander Skeltved, Steven Cummer |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108997
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| Publikation (Nr.) |
 EGU/EGU2015-8847.pdf |
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| Zusammenfassung |
| Terrestrial gamma ray flashes (TGFs) are produced by the runaway electron beams inside the
thunderclouds by bremsstrahlung. Numerous satellite observations of the TGFs cannot
provide a definite answer about the details of the generation processes of TGFs. There exist
two TGF production models. According to one a TGF is produced during the upward
negative IC leader propagation. Another one supposes that relativistic runaway electron
avalanches (RREAs) producing TGFs can develop in strong thundercloud electric fields
without involving a leader discharge mechanism. One of the most promising observation
instruments to investigate the TGF production is LF radio waves emitted by the RREAs or
RREA generated secondary currents. Detection and analyses of the radio waveforms from
these currents provide new possibilities to better understanding of TGF generation
mechanisms.
In this work we analyze RHESSI TGF data detected between 2004 and 2011 in
association with the VLF waveforms recorded by the VLF magnetic field receiver deployed at
the Duke University. Pairs of associated TGF-VLF events identified in combination with the
World Wide Lightning Location Network (WWLLN) catalogue which provides
independent lightning locations and timings. Selection criteria retrieved only the pairs with
WWLLN-RHESSI nadir distances less than 500 km and time difference between the TGF
start time and VLF sferic start time (recalculated to a WWLLN provided location) less than
150 μs, which is based on the RHESSI-WWLLN-Duke combined timing accuracy. In total 15
events within these limits were identified. These events support the possibility of
detection of VLF radio waveforms produced by RREAs or RREA associated secondary
currents.
Further search in the RHESSI data and Duke recordings without having WWLLN
confirmed locations revealed about a hundred TGF-VLF associated pairs. These are also
simultaneous within 150 μs and less than 500 km from nadir point. In this work we compare
the distribution of WWLLN-RHESSI-Duke events with the distribution of RHESSI-Duke
events. This comparison supports that the radio signals are simultaneous with the TGF
production. |
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