scholarly journals Some unusual discrete VLF emissions observed at a low-latitude ground station at Agra

1997 ◽  
Vol 15 (8) ◽  
pp. 1005-1008 ◽  
Author(s):  
B. Singh
Keyword(s):  
Time Delay ◽  
Time Delays ◽  
Geomagnetic Latitude ◽  
Propagation Time ◽  
Equatorial Anomaly ◽  
Low Latitude ◽  
Time Intervals ◽  
Ground Station ◽  
Unusual Occurrence ◽  
Vlf Emissions

Abstract. A detailed analysis of the VLF emissions data obtained during occasional whistler campaigns at the low-latitude ground station Agra (geomagnetic latitude 17°1' N, L = 1.15) has yielded some unusual discrete VLF emissions of the rising type. These include (1) emissions occurring at time intervals increasing in ge ommetrical progression, (2) emissions occuring simulta neously in different frequency ranges and (3) emissions observed during daytime. In the present study, the observed characteristics of these emissions are described and interpreted. It is shown that the increasing time delay between different components of the emissions match closely with the propagation time delays between different hops of a whistler of dispersion 19 s1/2, the unusual occurrence of the emissions in two different frequency ranges approximately at the same time may possibly be linked with their generation at two different locations, and the occurrence of emissions during daytime may be due to propagation under the influence of equatorial anomaly.

scholarly journals Quasi-periodic VLF emissions observed during daytime at a low latitude Indian ground station Jammu

2009 ◽  
Vol 118 (3) ◽  
pp. 209-216 ◽  
Author(s):  
K. K. Singh ◽  
J. Singh ◽  
R. P. Patel ◽  
A. K. Singh ◽  
R. P. Singh ◽  
...  
Keyword(s):  
Low Latitude ◽  
Ground Station ◽  
Vlf Emissions

scholarly journals WHISTLER-TRIGGERED VLF EMISSIONS RECORDED AT JAMMU DURING DAY TIME

2021 ◽  
Vol 8 (1) ◽  
Author(s):  
Krishna Kumar Singh ◽  
Krishna Kumar Singh
Keyword(s):  
Geomagnetic Latitude ◽  
Longitudinal Mode ◽  
Magnetic Activity ◽  
Relative Amplitude ◽  
Low Latitude ◽  
Time Period ◽  
Recorded Data ◽  
Field Lines ◽  
Vlf Emissions ◽  
Vlf Waves

Whistler-triggered VLF emissions recorded at low latitude station Jammu (Geomagnetic latitude = 220 26/ N; L = 1.17) during day time period on 19th February 1999 at 14:35 hrs. IST. The recorded data have been analyzed. Based on whistler-triggered VLF emissions spectrum, the VLF waves propagate along the path with L – values lying between L = 4.4 and 4.38. During the observation period, magnetic activity was very high. Mostly these types of emissions recorded at mid latitudes. These whistler-triggered emission waves propagate along the geomagnetic field lines either in a ducted mode or in a pro-longitudinal mode. Relative amplitude of whistlers waves is almost equal to relative amplitude of triggered emissions. The proposed generation mechanism explains through the dynamic spectra of the whistler-triggered emissions.

scholarly journals Two types of ELF hiss observed at Varanasi, India

1999 ◽  
Vol 17 (10) ◽  
pp. 1260-1267 ◽  
Author(s):  
D. K. Singh ◽  
Ashok K. Singh ◽  
R. P. Patel ◽  
R. P. Singh ◽  
A. K. Singh
Keyword(s):  
Particle Interaction ◽  
Geomagnetic Latitude ◽  
Middle Latitude ◽  
Particle Interactions ◽  
Low Latitude ◽  
Geomagnetic Field Line ◽  
Wave Amplification ◽  
Ground Station ◽  
Radiated Power ◽  
The Earth

Abstract. The morphology of ELF hiss events observed at low-latitude ground station Varanasi (L = 1.07, geomagnetic latitude 14°55'N) are reported, which consist of two types: (1) events which propagated in ducted mode along the geomagnetic field line corresponding to observing station Varanasi and (2) events which propagated in ducted mode along higher L-values (L = 4–6), after reaching the lower edge of ionosphere excite the Earth-ionosphere wave guide and propagate towards equator to be received at Varanasi. To understand the generation mechanism of ELF hiss, incoherent Cerenkov radiated power from the low latitude and middle latitude plasmasphere are evaluated. Considering this estimated power as an input for wave amplification through wave-particle interaction, the growth rate and amplification factor is evaluated which is too small to explain the observed wave intensity. It is suggested that some non-linear mechanism is responsible for the generation of ELF hiss.Key words. Ionosphere (equatorial ionosphere; ionosphere · magnetosphere interactions; wave · particle interactions)

Drifting ELF/VLF Emissions Observed at Low Latitude Ground Station During Geomagnetic Storm

2010 ◽  
Vol 106 (2-4) ◽  
pp. 119-132
Author(s):  
A. K. Singh ◽  
Shubha Singh ◽  
R. P. Singh
Keyword(s):  
Geomagnetic Storm ◽  
Low Latitude ◽  
Ground Station ◽  
Vlf Emissions

Observation of discrete VLF emissions at Indian low-latitude ground station Srinagar (L = 1.28)

2015 ◽  
Vol 89 (10) ◽  
pp. 989-995
Author(s):  
S. B. Singh ◽  
M. U. D. Rather ◽  
P. A. Ganai ◽  
A. K. Singh
Keyword(s):  
Low Latitude ◽  
Ground Station ◽  
Vlf Emissions

scholarly journals Delay-Dependent Robust Stabilization for Nonlinear Large Systems via Decentralized Fuzzy Control

2011 ◽  
Vol 2011 ◽  
pp. 1-20 ◽  
Author(s):  
Chun-xia Dou ◽  
Zhi-sheng Duan ◽  
Xing-bei Jia ◽  
Xiao-gang Li ◽  
Jin-zhao Yang ◽  
...  
Keyword(s):  
Time Delay ◽  
Fuzzy Control ◽  
Upper Bound ◽  
Time Delays ◽  
Sufficient Conditions ◽  
Large System ◽  
Disturbance Attenuation ◽  
Robust Controller ◽  
Large Systems ◽  
Delay Dependent

A delay-dependent robust fuzzy control approach is developed for a class of nonlinear uncertain interconnected time delay large systems in this paper. First, an equivalent T–S fuzzy model is extended in order to accurately represent nonlinear dynamics of the large system. Then, a decentralized state feedback robust controller is proposed to guarantee system stabilization with a prescribedH∞disturbance attenuation level. Furthermore, taking into account the time delays in large system, based on a less conservative delay-dependent Lyapunov function approach combining with linear matrix inequalities (LMI) technique, some sufficient conditions for the existence ofH∞robust controller are presented in terms of LMI dependent on the upper bound of time delays. The upper bound of time-delay and minimizedH∞performance index can be obtained by using convex optimization such that the system can be stabilized and for all time delays whose sizes are not larger than the bound. Finally, the effectiveness of the proposed controller is demonstrated through simulation example.

scholarly journals Statistical study of medium-scale traveling ionospheric disturbances in low-latitude ionosphere using an automatic algorithm

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Pin-Hsuan Cheng ◽  
Charles Lin ◽  
Yuichi Otsuka ◽  
Hanli Liu ◽  
Panthalingal Krishanunni Rajesh ◽  
...  
Keyword(s):  
Climate Model ◽  
Geomagnetic Latitude ◽  
Detection Algorithm ◽  
Support Vector ◽  
Electron Content ◽  
Ionospheric Disturbances ◽  
Low Latitude ◽  
Total Electron ◽  
Medium Scale ◽  
Traveling Ionospheric Disturbances

AbstractThis study investigates the medium-scale traveling ionospheric disturbances (MSTIDs) statistically at the low-latitude equatorial ionization anomaly (EIA) region in the northern hemisphere. We apply the automatic detection algorithm including the three-dimensional fast Fourier transform (3-D FFT) and support vector machine (SVM) on total electron content (TEC) observations, derived from a network of ground-based global navigation satellite system (GNSS) receivers in Taiwan (14.5° N geomagnetic latitude; 32.5° inclination), to identify MSTID from other waves or irregularity features. The obtained results are analyzed statistically to examine the behavior of low-latitude MSTIDs. Statistical results indicate the following characteristics. First, the southward (equatorward) MSTIDs are observed almost every day during 0800–2100 LT in Spring and Winter. At midnight, southward MSTIDs are more discernible in Summer and majority of them are propagating from Japan to Taiwan. Second, northward (poleward) MSTIDs are more frequently detected during 1200–2100 LT in Spring and Summer with the secondary peak of occurrence between day of year (DOY) 100–140 during 0000–0300 LT. The characteristics of the MSTIDs are interpreted with additional observations from radio occultation (RO) soundings of FORMOSAT-3/COSMIC as well as modeled atmospheric waves from the high-resolution Whole Atmosphere Community Climate Model (WACCM) suggesting that the nighttime MSTIDs in Summer is likely connected to the atmospheric gravity waves (AGWs).

scholarly journals Methods for broadband signals mutual time delays estimating enhancement

2019 ◽  
Vol 30 ◽  
pp. 03012
Author(s):  
Ilya Grin ◽  
Oleg Morozov
Keyword(s):  
Time Delay ◽  
Computational Efficiency ◽  
Radiation Source ◽  
Time Delays ◽  
Time Delay Estimation ◽  
Ambiguity Function ◽  
Delay Estimation ◽  
Reliability Criterion ◽  
Optimal Processing ◽  
Narrowband Channels

This paper considers methods for estimating the mutual time delay of broadband signals recorded by satellites based multi-position systems for determining the location of a radiation source. All methods considered are based on modified algorithms for calculating the ambiguity function. The presented algorithms are based on the extraction of narrowband channels from the studied signals and their further optimal processing. The reliability criterion for mutual time delay estimation by the presented methods was evaluated. Based on the results and analysis of computational efficiency, viability of methods considered and their modifications was determined.

Time-Intensity Trade for Speech: A Temporal Speech-Stenger Effect

1976 ◽  
Vol 19 (4) ◽  
pp. 749-766 ◽  
Author(s):  
Michael J.M. Raffin ◽  
David J. Lilly ◽  
Aaron R. Thornton
Keyword(s):  
Time Delay ◽  
Clinical Application ◽  
Time Delays ◽  
Multiple Images ◽  
Potential Clinical Application ◽  
Interaural Time Delay ◽  
Lateralization Effect

Time-intensity trade for selected spondaically stressed words was investigated using a centering method for interaural time delays of 0.00, 1.00, 2.00, 2.25, 2.50, and 2.75 msec at five levels of presentation: 0-, 25-, 40-, 55-, and 70-dB HL (ANSI, 1969). Lateralization effects increased with level of presentation, with a maximum lateralization effect of between 22 and 30 dB occuring with an interaural time delay of 2.25 msec. Multiple images were perceived by all subjects with an interaural time delay of 2.75 msec and by some subjects with an interaural time delay of 2.50 msec at high levels of presentation. No “ear effect” was observed for any of the listeners. A potential clinical application is discussed for this temporal speech-Stenger effect.

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