Automatic Whistler Detector and Analyzer system: Automatic Whistler Detector

Abstract

[1] A new, unique system has been developed for the automatic detection and analysis of whistlers. The Automatic Whistler Detector and Analyzer (AWDA) system has two purposes: (1) to automatically provide plasmaspheric electron densities extracted from whistlers and (2) to collect statistical data for the investigation of whistler generation and propagation. This paper presents the details of and the first results obtained by the automatic detector segment. The detector algorithm is based on image correlation where the target image is a preprocessed spectrogram of raw VLF signals and the pattern is a model whistler. The first AWDA system has been working in Tihany, Hungary (L = 1.8), and has collected 100,000 whistler traces per year. The overall detection efficiency using a parameter set optimized for purpose 2 is 90% for misdetection and 50-80% for false detection. The statistical analysis over the period February 2002 to February 2008 including 600,000 whistler traces shows high diurnal variations; whistler were mainly, but not only, detected when both the source and receiver regions were unlit. The seasonal occurrence is high during austral summer and low during austral winter. Comparison with Tarcsai et al. 's (1988) statistical study on Tihany whistlers shows differences in both diurnal and seasonal variations, but the latter study was made on 1388 manually identified whistlers only. The L value distributions of both data sets are similar. A global network of AWDA systems (AWDAnet) has been set up to overcome the time and space limitations of a single station; the network consists of 13 nodes, and another 6 are envisaged for the near future.

Remote sensing of D-region ionosphere using multimode tweeks

“…Time measurement in the computer was synchronized with the pulse per second (PPS) signal of a global positioning system (GPS) receiver. The PPS timing accuracy was better than 1 ls, which had been smaller than the data sampling period (*22 ls) [33]. The operational system could independently sample from the data streams provided from the both NS and EW loops.…”

“…The arrival times (t 1 and t 2 ) of sferics of frequencies (f 1 and f 2 ) could be read from spectrograms as well to determine propagation distance (d) of the tweeks. The details of AWD software and the MATLAB program for AWD analysis could be obtained from [33,34].…”

Ionosphere Waves Service (IWS) – a problem-oriented tool in ionosphere and Space Weather research produced by POPDAT project

“…As it is known from earlier works (Lichtenberger et al 2008) the automatic detection of pre-defined UWB (transient and whistler-like signals) signals in a record containing other strong signals, noise, is a complex task, however, it is solved in the case of ground-based records and this software system is running effectively in the AWDANet system around the globe. However, the structure of the satellite records differ from the ground-based ones.…”

“…However, the structure of the satellite records differ from the ground-based ones. The summary of the original AWD software for ground-based applications is given above in Section 5.1.1 and the details of this method can be found in the cited (Lichtenberger et al 2008) paper. The main differences between the ground-based and (ionospheric) satellite VLF records are demonstrated in Figures 11 and 12.…”

“…The procedure detects and optionally analyzes real time in VLF recordings the lightning generated whistlers, propagating in terrestrial plasma environment (Lichtenberger et al 2008). Automatic whistler detection is based on 2D correlation technique, carried out in dynamic spectra of high resolution ELF/VLF recordings.…”