Plasmaspheric parameters as determined from whistler spectrograms: a review

Whistlers detected and analyzed by Automatic Whistler Detector (AWD) at low latitude Indian stations

“…Kumar and Singh (2009) using GPS based measurements showed that Varanasi is situated at the edge to equatorial ionization anomaly region. We have also checked our GPS scintillation data for any possibility of observation of some ionospheric irregularities or plasma bubbles and found that some weak ionospheric irregularities were present at the time The ionospheric and other parameters derived from whistler measurements compare well with direct rocket and satellite measurements (Park et al, 1978;Singh et al, 1998;Chauhan and Singh, 2010;Kumar et al, 2012). The study of the latitudinal and longitudinal distribution of ionospheric parameters and its long term variations using rockets and satellites is financially and technically challenging, whereas these can be studied very readily by the whistler technique at a number of stations spread in latitude and longitude.…”

“…The analysis of whistlers from a ground-based station has long been regarded as inexpensive and effective tools for ionosphere/plasmasphere diagnostics (Park, 1972;Sazhin et al, 1992;Singh et al, 1998;Carpenter, 2007). For longitudinal propagation the whistler mode dispersion relation is given as (Helliwell, 1965) For our low latitude Indian stations whole propagation path of whistlers lies in the ionosphere.…”

“…VLF waves, which are generated by lightning return stroke currents (sferics, whistlers) travel between hemispheres along ionization ducts before entering the Earth-ionosphere wave-guide (Storey, 1953). Continuous monitoring and analysis of these waves (such as: radio atmospheric, tweeks, whistlers, VLF emissions) yield information about the height of the waveguide, equatorial electron density profiles (Tarcsai et al, 1988), electron/ion temperature (Sazhin et al, 1990), convective electric fields in the magnetosphere (Carpenter et al, 1972), duct width, duct lifetime (Singh et al, 1998), irregularities in the electron density (in the magnetosphere as well as lower ionosphere), lightning induced electron precipitation (LEP) (Inan et al, 2010), etc. (Siingh et al, 2008 and references therein).…”

“…The analysis of a whistler usually consists of the searching of whistlers in raw VLF data to obtain whistler spectrogram and applying a model using the scaled f-t pairs to calculate plasma and propagation parameters (Helliwell, 1965;Singh et al, 1998). However, it is not practical to manually search continuously recorded VLF data for whistler events as a source of regularly measured plasmaspheric parameters.…”

Remote sensing of D-region ionosphere using multimode tweeks

“…The tweek waveforms are better resolved and suffer less attenuation at night (typically \0.5 dB Mm -1 as compared to 5 dB Mm -1 during daytime) due to sharper D-region electron density profiles [4]. Dispersion analysis of tweeks yields information about the state of the D-region ionosphere along the path of propagation [5][6][7][8][9][10].…”