Articles written in Journal of Earth System Science
Volume 96 Issue 1 March 1987 pp 15-23
At trenches a few earthquake swarms of low magnitude have been observed before the medium size earthquake swarms. The first swarm was designated as precursory swarm and the second as mainshocks. Seismicity fluctuations before six such mainshocks events of medium size earthquakes of magnitudes ranging from 5.3 to 6.1 occurring in the east belt of Taiwan region have been discussed. A precursory gap between the precursory swarm and mainshock events has been observed. The duration of the gaps increases with magnitudes of the mainshocks suggesting a causal relationship between the two. Regression equations between the largest magnitude in the precursory swarms, the largest mainshock magnitude and the precusory gaps have been given.
Volume 117 Issue 3 June 2008 pp 219-225
In this paper,we report observations of unusual whistlers recorded at Jammu (geomag.lat.= 22° 26′N; 𝐿 =1.17), India on March 8, 1999 during the daytime. They are interpreted as one-hop ducted whistlers having propagated along higher 𝐿 -values in closely spaced narrow ducts from the opposite hemispheres. After leakage from the duct, the waves might have propagated in the earthionosphere waveguide towards the equator in surface mode.Tentative explanation of the dynamic spectra of these events is brieﬂy presented.
Volume 118 Issue 3 June 2009 pp 209-216
This paper reports quasi-periodic pulsing hiss emissions recorded during daytime in the frequency range of 50 Hz –15 kHz at low latitude station Jammu (geomag.lat.=22° 26′N; 𝐿 =1.17). It is noted that pulsing VLF emissions are a rare phenomena at low latitudes.The various spectrograms of pulsing VLF hiss emissions presented in this paper clearly show band limited spectrums regularly pulsing with almost equal period of the order of few seconds in the frequency range of ∼3-8 kHz. Generation and propagation mechanism of these emissions are brieﬂy discussed.