Theoretical study of lower ionospheric response to solar flares: sluggishness of D-region and peak time delay

2014 ◽  
Vol 356 (1) ◽  
pp. 19-28 ◽  
Author(s):  
Sourav Palit ◽  
Tamal Basak ◽  
Sujay Pal ◽  
Sandip K. Chakrabarti
Keyword(s):  
Time Delay ◽  
Solar Flares ◽  
Theoretical Study ◽  
Peak Time ◽  
Ionospheric Response ◽  
D Region

scholarly journals Survey of electron density changes in the daytime ionosphere over the Arecibo observatory due to lightning and solar flares

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Caitano L. da Silva ◽  
Sophia D. Salazar ◽  
Christiano G. M. Brum ◽  
Pedrina Terra
Keyword(s):  
Electron Density ◽  
Solar Flares ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Weather Conditions ◽  
Optical Observations ◽  
Radio Waves ◽  
D Region ◽  
E Region ◽  
Arecibo Observatory

AbstractOptical observations of transient luminous events and remote-sensing of the lower ionosphere with low-frequency radio waves have demonstrated that thunderstorms and lightning can have substantial impacts in the nighttime ionospheric D region. However, it remains a challenge to quantify such effects in the daytime lower ionosphere. The wealth of electron density data acquired over the years by the Arecibo Observatory incoherent scatter radar (ISR) with high vertical spatial resolution (300-m in the present study), combined with its tropical location in a region of high lightning activity, indicate a potentially transformative pathway to address this issue. Through a systematic survey, we show that daytime sudden electron density changes registered by Arecibo’s ISR during thunderstorm times are on average different than the ones happening during fair weather conditions (driven by other external factors). These changes typically correspond to electron density depletions in the D and E region. The survey also shows that these disturbances are different than the ones associated with solar flares, which tend to have longer duration and most often correspond to an increase in the local electron density content.

Time delay between H? and hard X-ray emissions during impulsive solar flares

Solar Physics ◽  
1985 ◽  
Vol 97 (1) ◽  
pp. 107-112
Author(s):  
V. K. Verma ◽  
M. C. Pande
Keyword(s):  
Time Delay ◽  
Solar Flares ◽  
X Ray

Theoretical Study on Time Delay of Slow Light by Remodeling SBS Gain and Absorption Spectrum

2012 ◽  
Vol 10 (6) ◽  
Author(s):  
Qiliang Li ◽  
Yong Zhang ◽  
Ziyang Wang ◽  
Ran Zeng ◽  
Tianshu Wang ◽  
...  
Keyword(s):  
Absorption Spectrum ◽  
Time Delay ◽  
Slow Light ◽  
Theoretical Study

Theoretical Study of the Spatially Resolved Soft X‐Ray versus Hard X‐Ray Relationship in Solar Flares

1997 ◽  
Vol 491 (1) ◽  
pp. 395-401 ◽  
Author(s):  
Peng Li ◽  
James M. McTiernan ◽  
A. Gordon Emslie
Keyword(s):  
Solar Flares ◽  
Theoretical Study ◽  
X Ray ◽  
Spatially Resolved

Studying the ionospheric absorption during large solar flare events in September 2017

2020 ◽  
Author(s):  
Attila Buzas ◽  
Veronika Barta ◽  
Daniel Kouba
Keyword(s):  
Solar Flare ◽  
Solar Flares ◽  
Radio Waves ◽  
Absorption Data ◽  
Ionospheric Response ◽  
Enhanced Absorption ◽  
Radio Wave Absorption ◽  
Cycle 24 ◽  
Low Latitude Ionosphere ◽  
University Of Massachusetts

<p>The most intense external force affecting the ionosphere from above is related to large solar flare events, therefore it is of particular importance to study their impact on the ionosphere. During solar flares, the suddenly increased radiation causes increased ionization and enhanced absorption of radio waves leading to partial or even total radio fade-out lasting for hours in some cases (e. g. [1] [2]).</p><p> </p><p>The ionospheric response to large solar flares have been investigated using the ionosonde data measured at Pruhonice (PQ052, 50°, 14.5°) in September 2017, the most active solar period of Solar Cycle 24. A novel method [3] to calculate and investigate the absorption of radio waves propagating in the ionosphere is used to determine the absorption during large solar flare events (M and X class). Subsequently, the absorption data are compared with the indicators derived from the f<sub>min</sub> method (f<sub>min</sub>, the minimum frequency is considered as a qualitative proxy for the “nondeviative” radio wave absorption occurring in the D-layer). Total and partial radio fade-out and increased values (with 2-5 MHz) of the f<sub>min</sub> parameter were experienced during and after the intense solar flares (> M3). The combination of these two methods may prove to be an efficient approach to monitor the ionospheric response to solar flares.</p><p> </p><p>[1] Sripathi, S., Balachandran, N., Veenadhari, B., Singh, R., and Emperumal, K.: Response of the equatorial and low-latitude ionosphere to an intense X-class solar flare (X7/2B) as observed on 09 August 2011, J. Geophys. Res.-Space, 118, 2648–2659, 2013.</p><p>[2] Barta, V., Sátori, G., Berényi, K. A., Kis, Á., and Williams, E. (2019). Effects of solar flares on the ionosphere as shown by the dynamics of ionograms recorded in Europe and South Africa. Annales Geophysicae, Vol. 37, No. 4, pp. 747-761</p><p>[3] Sales, G. S., 2009, HF absorption measurements using routine digisonde data, Conference material, XII. International Digisonde Forum, University of Massachusetts</p>

scholarly journals Flipped parameter technique applied on source localization in energy constraint sensor arrays

2009 ◽  
Vol 7 (1) ◽  
pp. 7-22
Author(s):  
Vlastimir Pavlovic ◽  
Zoran Velickovic
Keyword(s):  
Time Delay ◽  
Source Localization ◽  
Cross Correlation ◽  
Sensor Arrays ◽  
Time Delay Estimation ◽  
Peak Time ◽  
Coherent Signals ◽  
Distributed Sensor ◽  
Passive Source Localization ◽  
Single Sensor

In this paper novel flipped parameter technique (FPT) for time delay estimation (TDE) in source localization problem is described. We propose passive source localization technique based on the development of an energy efficient algorithm that can reduce intersensor and interarray communication. We propose a flipped parameter (FP) which can be defined for any sensor in distributed sensor subarrays during the observation period. Unlike classical TDE methods that evaluate cross-correlation function, FPT requires evaluation based upon single sensor signal. The computed cross correlation between a signal and its analytic 'flipped' pair (flipped correlation) is a smooth function which peak (time delay) can be accurately detected. Flipped parameters are sufficient to determine all differential delays of the signals related to the same source. The flipped parameter technique can be used successfully in two-step methods of passive source localization with significantly less energy in comparison to the classic cross correlation. The use of FPT method is especially significant for the energy constrain distributed sensor subarrays. Using synthetic seismic signals, we illustrate the error of the source localization for classical and proposed method in the presence of noise. We demonstrate the performance improvement in noise environment of the proposed technique in comparison to the classic methods that use real signals. The proposed technique gives accurate results for both coherent and non-coherent signals.

scholarly journals Ionospheric Sluggishness: A Characteristic Time‐Lag of the Ionospheric Response to Solar Flares

2021 ◽  
Author(s):  
S. Chakraborty ◽  
J. M. Ruohoniemi ◽  
J. B. H. Baker ◽  
R. A. D. Fiori ◽  
S. M. Bailey ◽  
...  
Keyword(s):  
Solar Flares ◽  
Characteristic Time ◽  
Time Lag ◽  
Ionospheric Response
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