Browsing by Author "J. Lichtenberger"

Now showing 1 - 4 of 4

Application of matched filtering and parameter estimation technique to low latitude whistlers
(Elsevier Ltd, 1999) R.P. Singh; D.K. Singh; Ashok K. Singh; D. Hamar; J. Lichtenberger
The Matched Filtering and Parameter Estimation (MFPE) technique developed for the analysis of mid/high latitude whistlers has been extended to analyze whistlers recorded at low latitude ground station Varanasi, India (geomagnetic latitude 14° 55′ N, longitude 153° 59′ E, L=1.07). Some of the whistlers recorded at Varanasi are found to have propagated along higher L-values (L>2). It has been argued that these whistlers after exiting the ionosphere have propagated towards the equator in the Earth-ionosphere waveguide. Trace splitting is observed below the nose frequency and above 2.0 kHz, a result in agreement with mid/high latitude whistlers. The trace splitting structure revealed by MFPE demonstrates the complexities of whistler wave propagation and is quite helpful in deriving information about high resolution features of the duct structure. The banded features observed in the dynamic spectrum are clearly seen in the output of the matched filter. The observed banded features may arise due to interference between the wavelets propagating in the duct/waveguide. © Elsevier Science Ltd.
Application of matched filtering to short whistlers recorded at low latitudes
(2004) R.P. Singh; Lalmani; D. Hamar; J. Lichtenberger
The matched filtering and parameter estimation technique has been successfully used to analyze short whistlers (frequency range ∼1 kHz) recorded at low-latitude station Jammu (geom. lat.=22°16′N, L=1.17), India. The analyzed whistlers recorded on June 5, 1997 during magnetically quiet period are found to have propagated along higher L-values (L>3.5). In some cases there is no correspondence in their dispersion value and derived L-value, which shows the complexity of the propagation mechanism. Trace-splitting and fine structure present in dynamic spectra may yield additional information about the propagation mechanism. © 2004 Elsevier Ltd. All rights reserved.
Matched filtering analysis of diffused whistlers and their propagation at low latitudes
(2006) R.P. Singh; Kalpana Singh; Ashok K. Singh; D. Hamar; J. Lichtenberger
Diffused whistlers recorded at low latitude station Varanasi (geom. lat. = 14°55′N, L = 1.07) India on January 11, 1998 have been analyzed using digital matched filtering and parameter estimation technique to achieve high accuracy in the determination of whistler and medium parameters. This is the first example of the analysis of diffused whistlers using matched filtering technique from low latitudes. It is found that path of propagation of these whistlers are anomalously far from the receiving station. Further, there is no correspondence between their low dispersion value and derived high L-value. © 2005 Elsevier Ltd. All rights reserved.
Matched filtering-parameter estimation method and analysis of whistlers recorded at Varanasi
(Indian Acad Sci, 2000) R.P. Singh; R.P. Patel; Ashok K. Singh; D. Hamar; J. Lichtenberger
The matched filtering technique is based on the digital-construction of theoretical whistlers and their comparison with observed whistlers. The parameters estimated from the theoretical and experimental whistler curves are matched to have higher accuracy using digital filters. This yields a resolution ten times better in the time domain. We have tested the applicability of this technique for the analysis of whistlers recorded at Varanasi. It is found that the whistlers have propagated along L > 2 and have wave normal angles after exiting from the ionosphere such that they propagate towards equator in the earth-ionosphere wave-guide. High-resolution analysis shows the presence of fine structures present in the dynamic spectrum. An effort is made to interpret the results.