scholarly journals Modeling of the Very Low Frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

2013 ◽  
Vol 13 (3) ◽  
pp. 6007-6033 ◽  
Author(s):  
S. Palit ◽  
T. Basak ◽  
S. K. Mondal ◽  
S. Pal ◽  
S. K. Chakrabarti
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Radio Wave ◽  
Electron Density ◽  
Solar Flares ◽  
Time Variation ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Very Low Frequency ◽  
Geant4 Monte Carlo Simulation

Abstract. X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~ 60 to 100 km) in excess of what is expected from a quiet sun. Very Low Frequency (VLF) radio wave signals reflected from the D region are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the lower ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the VLF signal change. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

scholarly journals Modeling of very low frequency (VLF) radio wave signal profile due to solar flares using the GEANT4 Monte Carlo simulation coupled with ionospheric chemistry

2013 ◽  
Vol 13 (18) ◽  
pp. 9159-9168 ◽  
Author(s):  
S. Palit ◽  
T. Basak ◽  
S. K. Mondal ◽  
S. Pal ◽  
S. K. Chakrabarti
Keyword(s):  
Monte Carlo Simulation ◽  
Monte Carlo ◽  
Radio Wave ◽  
Solar Flares ◽  
Time Variation ◽  
Low Frequency ◽  
Very Low Frequency ◽  
D Region ◽  
Geant4 Monte Carlo Simulation ◽  
Class Flare

Abstract. X-ray photons emitted during solar flares cause ionization in the lower ionosphere (~60 to 100 km) in excess of what is expected to occur due to a quiet sun. Very low frequency (VLF) radio wave signals reflected from the D-region of the ionosphere are affected by this excess ionization. In this paper, we reproduce the deviation in VLF signal strength during solar flares by numerical modeling. We use GEANT4 Monte Carlo simulation code to compute the rate of ionization due to a M-class flare and a X-class flare. The output of the simulation is then used in a simplified ionospheric chemistry model to calculate the time variation of electron density at different altitudes in the D-region of the ionosphere. The resulting electron density variation profile is then self-consistently used in the LWPC code to obtain the time variation of the change in VLF signal. We did the modeling of the VLF signal along the NWC (Australia) to IERC/ICSP (India) propagation path and compared the results with observations. The agreement is found to be very satisfactory.

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.

scholarly journals Classification of X-ray solar flares regarding their effects on the lower ionosphere electron density profile

2008 ◽  
Vol 26 (7) ◽  
pp. 1731-1740 ◽  
Author(s):  
D. P. Grubor ◽  
D. M. Šulić ◽  
V. Žigman
Keyword(s):  
Electron Density ◽  
Solar Flares ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Electron Density Profile ◽  
Height Range ◽  
X Ray ◽  
Reflection Height ◽  
Single Trace

Abstract. The classification of X-ray solar flares is performed regarding their effects on the Very Low Frequency (VLF) wave propagation along the Earth-ionosphere waveguide. The changes in propagation are detected from an observed VLF signal phase and amplitude perturbations, taking place during X-ray solar flares. All flare effects chosen for the analysis are recorded by the Absolute Phase and Amplitude Logger (AbsPal), during the summer months of 2004–2007, on the single trace, Skelton (54.72 N, 2.88 W) to Belgrade (44.85 N, 20.38 E) with a distance along the Great Circle Path (GCP) D≈2000 km in length. The observed VLF amplitude and phase perturbations are simulated by the computer program Long-Wavelength Propagation Capability (LWPC), using Wait's model of the lower ionosphere, as determined by two parameters: the sharpness (β in 1/km) and reflection height (H' in km). By varying the values of β and H' so as to match the observed amplitude and phase perturbations, the variation of the D-region electron density height profile Ne(z) was reconstructed, throughout flare duration. The procedure is illustrated as applied to a series of flares, from class C to M5 (5×10−5 W/m2 at 0.1–0.8 nm), each giving rise to a different time development of signal perturbation. The corresponding change in electron density from the unperturbed value at the unperturbed reflection height, i.e. Ne(74 km)=2.16×108 m−3 to the value induced by an M5 class flare, up to Ne(74 km)=4×1010 m−3 is obtained. The β parameter is found to range from 0.30–0.49 1/km and the reflection height H' to vary from 74–63 km. The changes in Ne(z) during the flares, within height range z=60 to 90 km are determined, as well.

scholarly journals The very low-frequency transmitter radio wave anomalies related to the 2010 Ms 7.1 Yushu earthquake observed by the DEMETER satellite and the possible mechanism

2020 ◽  
Vol 38 (5) ◽  
pp. 969-981
Author(s):  
Shufan Zhao ◽  
XuHui Shen ◽  
Zeren Zhima ◽  
Chen Zhou
Keyword(s):  
Electric Field ◽  
Electron Density ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Satellite Observation ◽  
Low Earth Orbit ◽  
Electron Content ◽  
Yushu Earthquake ◽  
Total Electron ◽  
Very Low Frequency

Abstract. Earthquakes may disturb the lower ionosphere through various coupling mechanisms during the seismogenic and coseismic periods. The VLF (very low-frequency) signal radiated from ground-based transmitters will be affected when it penetrates the disturbed ionosphere above the epicenter area, and this anomaly can be recorded by low-Earth orbit satellites under certain conditions. In this paper, the temporal and spatial variation of the signal-to-noise ratio (SNR) of the VLF transmitter signal in the ionosphere over the epicenter of 2010 Yushu Ms 7.1 earthquake in China is analyzed using DEMETER (Detection of Electro-Magnetic Emission Transmitted from Earthquake Regions) satellite observation. The results show that SNR over the epicenter of the Yushu earthquake especially in the southwestern region decreased (or dropped) before the main shock, and a GPS–TEC (Global Positioning System; total electron content) anomaly accompanied, which implies that the decrease in SNR might be caused by the enhancement of TEC. A full-wave method is used to study the mechanism of the change in SNR before the earthquake. The simulated results show SNR does not always decrease before an earthquake. When the electron density in the lower ionosphere increases by 3 times, the electric field will decrease about 2 dB, indicating that the disturbed-electric-field decrease of 20 % compared with the original electric field and vice versa. It can be concluded that the variation of electron density before earthquakes may be one of the important factors influencing the variation of SNR.

scholarly journals Strange VLF bursts in northern Scandinavia: case study of the afternoon "mushroom-like" hiss on 8 December 2013

2015 ◽  
Vol 33 (8) ◽  
pp. 991-995 ◽  
Author(s):  
J. Manninen ◽  
N. G. Kleimenova ◽  
A. Kozlovsky ◽  
I. A. Kornilov ◽  
L. I. Gromova ◽  
...  
Keyword(s):  
Low Frequency ◽  
Mutual Effect ◽  
Time History ◽  
Lower Ionosphere ◽  
Wave Interaction ◽  
Recovery Phase ◽  
Frequency Wave ◽  
Left Hand ◽  
Very Low Frequency ◽  
The Right

Abstract. We investigate a non-typical very low frequency (VLF) 1–4 kHz hiss representing a sequence of separated noise bursts with a strange "mushroom-like" shape in the frequency–time domain, each one lasting several minutes. These strange afternoon VLF emissions were recorded at Kannuslehto (KAN, ϕ = 67.74° N, λ = 26.27° E; L ∼ 5.5) in northern Finland during the late recovery phase of the small magnetic storm on 8 December 2013. The left-hand (LH) polarized 2–3 kHz "mushroom caps" were clearly separated from the right-hand (RH) polarized "mushroom stems" at the frequency of about 1.8–1.9 kHz, which could match the lower ionosphere waveguide cutoff (the first transverse resonance of the Earth–ionosphere cavity). We hypothesize that this VLF burst sequence could be a result of the modulation of the VLF hiss electron–cyclotron instability from the strong Pc5 geomagnetic pulsations observed simultaneously at ground-based stations as well as in the inner magnetosphere by the Time History of Events and Macroscale Interactions during Substorms mission probe (THEMIS-E; ThE). This assumption is confirmed by a similar modulation of the intensity of the energetic (1–10 keV) electrons simultaneously observed by the same ThE spacecraft. In addition, the data of the European Incoherent Scatter Scientific Association (EISCAT) radar at Tromsø show a similar quasi-periodicity in the ratio of the Hall-to-Pedersen conductance, which may be used as a proxy for the energetic particle precipitation enhancement. Our findings suggest that this strange mushroom-like shape of the considered VLF hiss could be a combined mutual effect of the magnetospheric ULF–VLF (ultra low frequency–very low frequency) wave interaction and the ionosphere waveguide propagation.

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