Mechanism of inverted-chirp infrasonic radiation from sprites
Article first published online: 18 DEC 2010
Copyright 2010 by the American Geophysical Union.
Geophysical Research Letters
Volume 37, Issue 24, December 2010
How to Cite
2010), Mechanism of inverted-chirp infrasonic radiation from sprites, Geophys. Res. Lett., 37, L24803, doi:10.1029/2010GL045304., and (
- Issue published online: 18 DEC 2010
- Article first published online: 18 DEC 2010
- Manuscript Accepted: 4 OCT 2010
- Manuscript Revised: 29 SEP 2010
- Manuscript Received: 30 AUG 2010
 Farges and Blanc (2010) reported inverted-chirp infrasonic signals with high frequencies arriving before low frequencies, possibly emitted by sprite discharges and observed on the ground at close range (<100 km) from the source. In the present work a parallel version of a 2-D FDTD model of infrasound propagation in a realistic atmosphere is applied to demonstrate that the observed morphology of infrasound signals is consistent with general scaling of diameters of sprite streamers inversely proportionally to the air density. The smaller structures at lower altitudes radiate higher infrasonic frequencies that arrive first at the observational point on the ground, while the low frequency components are delayed because they originate at lower air densities at higher altitudes. The results demonstrate that strong absorption of high frequency infrasonic components at high altitudes (i.e., ∼0.2 dB/km for 8 Hz at 70 km) may also contribute to formation of inverted-chirp signals observed on the ground at close range.