Interferometric measurement of ionization in a grassfire

Mphale, Kgakgamatso Marvel, Heron, M., Ketlhwaafetse, R., Letsholathebe, D., and Casey, R. (2010) Interferometric measurement of ionization in a grassfire. Meteorology and Atmospheric Physics, 106 (3-4). pp. 191-203.

[img]
Preview
PDF (Published Version) - Published Version
Download (2MB)
View at Publisher Website: http://dx.doi.org/10.1007/s00703-010-006...
 
5
125


Abstract

Grassfire plumes are weakly ionized gas. The ionization in the fire plume is due to thermal and chemi-ionization of incumbent species, which may include graphitic carbon, alkalis and thermally excited radicals, e.g., methyl. The presence of alkalis (e.g., potassium and sodium) in the fires makes thermal ionization a predominant electron producing mechanism in the combustion zone. Alkalis have low dissociation and ionization potentials and therefore require little energy to thermally decompose and give electrons. Assuming a Maxwellian velocity distribution of flame particles and electron-neutral collision frequency much higher than plasma frequency, the propagation of radio waves through a grassfire is predicted to have attenuation and phase shift. Radio wave propagation measurements were performed in a moderate intensity (554 kW m^−1) controlled grassfire at 30- and 151-MHz frequencies on a 44 m path using a radio wave interferometer. The maximum temperature measured in the controlled burn was 1071 K and the observed fire depth was 0.9 m. The radio wave interferometer measured attenuation coefficients of 0.033 and 0.054 dB m^−1 for 30- and 151-MHz, respectively. At collision frequency of 1.0 × 10^11 s^−1, maximum electron density was determined to be 5.061 × 10^15 m^−3.

Item ID: 11792
Item Type: Article (Research - C1)
ISSN: 1436-5065
Date Deposited: 20 Aug 2010 01:09
FoR Codes: 04 EARTH SCIENCES > 0401 Atmospheric Sciences > 040199 Atmospheric Sciences not elsewhere classified @ 100%
SEO Codes: 97 EXPANDING KNOWLEDGE > 970104 Expanding Knowledge in the Earth Sciences @ 100%
Downloads: Total: 125
Last 12 Months: 19
More Statistics

Actions (Repository Staff Only)

Item Control Page Item Control Page