subionospheric vlf propagation modelling during solar flare
TRANSCRIPT
![Page 1: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/1.jpg)
Akel, A. F. ;Raulin,J. -P
[1] CRAAM, Centro de Radio astronomia e Astrofísica
Mackenzie, Universidade Presbiteriana Mackenzie
Subionospheric VLF Propagation Modelling During Solar Flare
São Paulo, 03 de Outubro de 2014
![Page 2: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/2.jpg)
Outline � Overview � Quiescente VLF simulations � Estimate of ionospheric parameters � Results � Conclusions
![Page 3: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/3.jpg)
D layer
E layer
For VLF waves , frequencies between 3 – 30 kHz, the ionospheric D region (day) and the Earth’s surface are good electrical conductors and reflecting media.
ωων
ω rp iiN Ω−=−= 11
22 rΩ Conductivity parameter (Wait & Spies, 1964)
)( '
~ Hzr e −Ω β Conductivity gradient β [km-1] (sharpness)
Reference height H′ [km]
![Page 4: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/4.jpg)
Propagation Model LWPC(Long-Wavelength Propagation Capability) � Geographic position of Transmitter and Receiver � Frequency and power of Transmitter � Date � Ionospheric conductivity profile
Day 𝜒< 90↑𝑜 𝛽=0.3 𝑘𝑚↑−1 ℎ↑′ =74 𝑘𝑚
Noite 𝜒> 99↑𝑜 𝛽=0.5 𝑘𝑚↑−1 ℎ↑′ =87 𝑘𝑚
(Exponential Wait model)
![Page 5: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/5.jpg)
Quiescente VLF simulations To calculate the diurnal variation of signal, we use polynomial functions dependent on the zenith angle for beta and h’ described by McRae and Thomson (2000). We use this polynomial to develop new functions most appropriate geometry of the path.
![Page 6: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/6.jpg)
![Page 7: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/7.jpg)
Solar transients Increases of incoming X-ray fluxes during flares and increasing particle precipitations during geomagnetic storms produce ionization excesses and change of the electrical properties of the lower ionosphere D region. Then changing: β [km-1] H′ [km]. Excesses of ionization can be monitored using the phase of long distance VLF propagating waves
+ 3.7 dB
+ 93º
![Page 8: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/8.jpg)
How to estimate the variation of parameters during solar flare ?
∆∅= 93.↑𝑜 →∆ℎ′−5.9 ±0.1 𝑘𝑚
Using the relationship propuse by Muraoka, Murato e Sato (1977)
∆∅=360 𝑑/𝜆↓𝑜 (1/2𝑅 + 𝜆↓𝑜↑ /16ℎ↓𝑜 )Δℎ′
∆𝜷 ?????
![Page 9: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/9.jpg)
Extraction of Ionospheric parameters
In left hand panel contour plot of amplitude vs. Δℎ ’ and ∆𝛽 and the right-hand panel contour plot of phase amplitude vs. Δℎ ’
and ∆𝛽.
![Page 10: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/10.jpg)
![Page 11: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/11.jpg)
Results
![Page 12: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/12.jpg)
Results
![Page 13: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/13.jpg)
Results
![Page 14: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/14.jpg)
Conclusions Using the simple model for lower ionosphere was possible fitted the VLF amplitude and phase. This work The quiescent model we calculated the parameters for solar flare. The height reference variation estimated was -6.6 km (decrese) and the sharpnessa as 0.1 km-1 (increase). This variations was responsable by increase of electron density in 20 times, at “diunal altitude” (70 km). The next step is find the parameters for other Solar flares allowing evaluate the general effects the increase os ionization by diferentes levels of solar X-ray flux.
![Page 15: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/15.jpg)
Acknowledgments
![Page 16: Subionospheric VLF Propagation Modelling During Solar Flare](https://reader030.vdocuments.site/reader030/viewer/2022012605/619a4c4c099b5767182a186b/html5/thumbnails/16.jpg)
Obrigado pela atenção
Obrigado pela atenção