Premium
Electrostatic field changes and durations of narrow bipolar events
Author(s) -
Karunarathne S.,
Marshall T. C.,
Stolzenburg M.,
Karunarath.
Publication year - 2016
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2016jd024789
Subject(s) - amplitude , range (aeronautics) , physics , pulse (music) , electric field , reflectivity , astrophysics , optics , materials science , quantum mechanics , detector , composite material
Using an array of 10 sensors, electric field change measurements of 35 positive narrow bipolar events (NBEs) were obtained at close range (≤10 km). At the closest sensor all 35 NBEs had a net electrostatic change (Δ E fast ) associated with the main bipolar pulse with amplitudes of 0.4 to 16.3 V/m (not range normalized). At the closest sensor the bipolar pulse of each of the 35 NBEs was followed by a relatively long, slow electrostatic change (Δ E slow ) with amplitudes of 0.1 to 43.4 V/m and durations of 0.7 to 33.7 ms. For Δ E fast , estimated 3‐D charge moments for 10 NBEs ranged from 0.46 C km to 1.81 C km with an average and standard deviation of (1.09 ± 0.36) C km. Seven 3‐D charge moments were essentially vertically oriented, and the other three moments were tilted at 10°–20° from vertical. The 10 3‐D charge moments were overlaid on vertical radar cross sections; 6 NBEs occurred in weak reflectivity near the upper reflectivity boundary; the other 4 NBEs occurred near the top of the high‐reflectivity core of the thunderclouds. For Δ E slow , we estimated 3‐D charge moments for only three NBEs; they ranged from 1.11 C km to 2.69 C km with an average of (1.83 ± 0.80) C km. A two current transmission line model matched the bipolar pulse and the following slow change (Δ E slow ) of one NBE reasonably well. The slow change mechanism may be different from the NBE mechanism and similar to the initial E‐change before typical lightning flashes.