scholarly journals Novel Modelling Approach for Obtaining the Parameters of Low Ionosphere under Extreme Radiation in X-Spectral Range

2021 ◽  
Vol 11 (23) ◽  
pp. 11574
Author(s):  
Vladimir A. Srećković ◽  
Desanka M. Šulić ◽  
Veljko Vujčić ◽  
Zoran R. Mijić ◽  
Ljubinko M. Ignjatović
Keyword(s):  
Spectral Range ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Simple Expression ◽  
Spectral Lines ◽  
Spectral Radiation ◽  
X Ray ◽  
Reflection Height ◽  
D Region ◽  
Modelling Approach

Strong radiation from solar X-ray flares can produce increased ionization in the terrestrial D-region and change its structure. Moreover, extreme solar radiation in X-spectral range can create sudden ionospheric disturbances and can consequently affect devices on the terrain as well as signals from satellites and presumably cause numerous uncontrollable catastrophic events. One of the techniques for detection and analysis of solar flares is studying the variations in time of specific spectral lines. The aim of this work is to present our study of solar X-ray flare effects on D-region using very low-frequency radio signal measurements over a long path in parallel with the analysis of X-spectral radiation, and to obtain the atmospheric parameters (sharpness, reflection height, time delay). We introduce a novel modelling approach and give D-region coefficients needed for modelling this medium, as well as a simple expression for electron density of lower ionosphere plasmas. We provide the analysis and software on GitHub.

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 Characterization of gravity waves in the lower ionosphere using very low frequency observations at Comandante Ferraz Brazilian Antarctic Station

2020 ◽  
Vol 38 (2) ◽  
pp. 385-394
Author(s):  
Emilia Correia ◽  
Luis Tiago Medeiros Raunheitte ◽  
José Valentin Bageston ◽  
Dino Enrico D'Amico
Keyword(s):  
Low Frequency ◽  
Lower Ionosphere ◽  
Drake Passage ◽  
Wave Period ◽  
Very Low Frequency ◽  
Reflection Height ◽  
D Region ◽  
Radio Signals ◽  
Sky Conditions ◽  
The Waves

Abstract. The goal of this work is to investigate the gravity wave (GW) characteristics in the low ionosphere using very low frequency (VLF) radio signals. The spatial modulations produced by the GWs affect the conditions of the electron density at reflection height of the VLF signals, which produce fluctuations of the electrical conductivity in the D region that can be detected as variations in the amplitude and phase of VLF narrowband signals. The analysis considered the VLF signal transmitted from the US Cutler, Maine (NAA) station that was received at Comandante Ferraz Brazilian Antarctic Station (EACF, 62.1∘ S, 58.4∘ W), with its great circle path crossing the Drake Passage longitudinally. The wave periods of the GWs detected in the low ionosphere are obtained using the wavelet analysis applied to the VLF amplitude. Here the VLF technique was used as a new aspect for monitoring GW activity. It was validated comparing the wave period and duration properties of one GW event observed simultaneously with a co-located airglow all-sky imager both operating at EACF. The statistical analysis of the seasonal variation of the wave periods detected using VLF technique for 2007 showed that the GW events occurred all observed days, with the waves with a period between 5 and 10 min dominating during night hours from May to September, while during daytime hours the waves with a period between 0 and 5 min are predominant the whole year and dominate all days from November to April. These results show that VLF technique is a powerful tool to obtain the wave period and duration of GW events in the low ionosphere, with the advantage of being independent of sky conditions, and it can be used during the whole day and year-round.

scholarly journals Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: energy-reflectivity spectrum

2008 ◽  
Vol 26 (7) ◽  
pp. 1793-1803 ◽  
Author(s):  
A. R. Jacobson ◽  
R. Holzworth ◽  
X.-M. Shao
Keyword(s):  
Lightning Discharge ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Angle Of Incidence ◽  
Radio Emissions ◽  
Statistical Variation ◽  
Reflection Height ◽  
D Region ◽  
Relationship Of ◽  
The Relationship

Abstract. We analyze data on radio-reflection from the D-region of the lower ionosphere, retrieving the energy-reflection coefficient in the frequency range ~5–95 kHz. The data are the same as developed for a recent study of ionospheric-reflection height, and are based on recordings of powerful (multi-Gigawatt) radio emissions from a type of narrow (~10 μs) lightning discharge known as "Narrow Bipolar Events". The sequential appearance of first the groundwave signal, and then the ionospheric single-hop reflection signal, permits us to construct the energy-reflection ratio. We infer the energy reflection's statistical variation with solar zenith angle, angle-of-incidence, frequency, and propagation azimuth. There is also a marginally-significant response of the energy reflectivity to solar X-ray flux density. Finally, we review the relationship of our results to previous published reports.

scholarly journals Characterization of gravity waves in the lower ionosphere using VLF observations at Comandante Ferraz Brazilian Antarctic Station

2019 ◽  
Author(s):  
Emilia Correia ◽  
Luis Tiago Medeiros Raunheitte ◽  
José Valentin Bageston ◽  
Dino Enrico D'Amico
Keyword(s):  
Gravity Waves ◽  
Low Frequency ◽  
Lower Ionosphere ◽  
Drake Passage ◽  
Wave Period ◽  
Reflection Height ◽  
D Region ◽  
Radio Signals ◽  
Almost All ◽  
Sky Conditions

Abstract. The goal of this work is to investigate the gravity waves (GWs) characteristics in the low ionosphere using very low frequency (VLF) radio signals. The spatial modulations produced by the GWs affect the conditions of the electron density at reflection height of the VLF signals, which produce fluctuations of the electrical conductivity in the D-region that can be detected as variations in the amplitude and phase of VLF narrowband signals. The analysis considered the VLF signal transmitted from the US Cutler/Marine (NAA) station that was received at Comandante Ferraz Brazilian Antarctic Station (EACF, 62.1° S, 58.4° W), which is a great circle path crossing longitudinally the Drake Passage. The wave periods of the GWs detected in the low ionosphere are obtained using the wavelet analysis applied to the VLF amplitude. The use of the VLF technique was validated comparing the wave period and duration properties of one GW event observed simultaneously with a co-located airglow all-sky imager both operating at EACF. The statistical analysis of the wave periods detected using VLF technique for 2007 showed that the GW events occur almost all nights, with a higher frequency per month from March to October. The predominant wave periods are more frequent between 10 and 15 min occurring preferentially during the equinoxes, but there are some events with periods higher than 60 min appearing only in the solstices (January and July). These results show that VLF technique is a powerful tool to obtain the wave period and duration of GW events in the low ionosphere, with the advantage to be independent of sky conditions, and can be used during daytime and year-round.

scholarly journals Low-frequency ionospheric sounding with Narrow Bipolar Event lightning radio emissions: regular variabilities and solar-X-ray responses

2007 ◽  
Vol 25 (10) ◽  
pp. 2175-2184 ◽  
Author(s):  
A. R. Jacobson ◽  
R. Holzworth ◽  
E. Lay ◽  
M. Heavner ◽  
D. A. Smith
Keyword(s):  
Noise Level ◽  
Radio Pulse ◽  
Low Frequency ◽  
Radio Propagation ◽  
Occurrence Rate ◽  
Radio Emissions ◽  
X Ray ◽  
Height Determination ◽  
Reflection Height ◽  
D Region

Abstract. We present refinements of a method of ionospheric D-region sounding that makes opportunistic use of powerful (109–1011 W) broadband lightning radio emissions in the low-frequency (LF; 30–300 kHz) band. Such emissions are from "Narrow Bipolar Event" (NBE) lightning, and they are characterized by a narrow (10-μs), simple emission waveform. These pulses can be used to perform time-delay reflectometry (or "sounding") of the D-region underside, at an effective LF radiated power exceeding by orders-of-magnitude that from man-made sounders. We use this opportunistic sounder to retrieve instantaneous LF ionospheric-reflection height whenever a suitable lightning radio pulse from a located NBE is recorded. We show how to correct for three sources of "regular" variability, namely solar zenith angle, radio-propagation range, and radio-propagation azimuth. The residual median magnitude of the noise in reflection height, after applying the regression corrections for the three regular variabilities, is on the order of 1 km. This noise level allows us to retrieve the D-region-reflector-height variation with solar X-ray flux density for intensity levels at and above an M-1 flare. The instantaneous time response is limited by the occurrence rate of NBEs, and the noise level in the height determination is typically in the range ±1 km.

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 Simulation of Gravity Wave D-region disturbance and its effect on the LWPC simulated VLF signal

2021 ◽  
Author(s):  
Abdellatif Benchafaa ◽  
Samir Nait Amor ◽  
Ghazali Mebarki
Keyword(s):  
Gravity Wave ◽  
Electron Density ◽  
Gravity Waves ◽  
Low Frequency ◽  
Ionization Rate ◽  
Neutral Atmosphere ◽  
Long Wave ◽  
Reflection Height ◽  
D Region ◽  
Atmosphere Density

Abstract. In this work we show the result of the numerical simulation of the gravity waves (GWs) D region disturbance. Effectively, using the Glukhov-Pasko-Inan (GPI) model of the electron density in the D region we were figured out the response of the electron density due to gravity wave neutral atmosphere oscillation. As a consequence to the D region disturbance, the electron density sometimes increases when the neutral atmosphere density decreases and vice versa. This behavior was interpreted by the decreases or increases of ionization rate by chemical loss process. In a second simulation work, we used the Long Wave Propagation Capability (LWPC) code to simulate the Very Low Frequency (VLF) signal when the gravity wave disturbance crossed the VLF path. The effect of the disturbance is to decrease the VLF signal reflection height below the ambient altitude (87 km) when the electron density increases. On the other hand and when the electron density drops, the VLF reflection altitude increased higher than 87 km.

scholarly journals Variations in ionospheric D-region recombination properties during increase of its X-ray heating induced by solar X-ray flare

2019 ◽  
Vol 23 (6 Part B) ◽  
pp. 4043-4053
Author(s):  
Aleksandra Nina ◽  
Vladimir Cadez ◽  
Masa Lakićević ◽  
Milan Radovanović ◽  
Aleksandra Kolarski ◽  
...  
Keyword(s):  
Loss Rate ◽  
Radiation Flux ◽  
Low Frequency ◽  
Recombination Coefficient ◽  
Electron Loss ◽  
Radio Waves ◽  
X Ray ◽  
Time Period ◽  
Recombination Processes ◽  
D Region

In this paper we present an analysis of parameters describing the effective recombination processes in the upper ionospheric D-region in the period of its additional heating by the X-radiation emitted during a solar X-ray flare. We present a procedure for calculation of the effective recombination coefficient and electron loss rate in the period when the X-radiation flux detected by the GOES satellite in the wavelength domain between 0.1 and 0.8 nm increases. The developed procedure is based on observational data obtained in the low ionospheric monitoring by the very low/low frequency radio waves and it is related to the considered area and time period. The obtained expressions are applied to data for the very low frequency signal emitted in Germany and recorded in Serbia during the solar X-ray flare detected by the GOES-14 satellite on May 5, 2010.

Diagnostics of the Solar X-Flare Impact on Lower Ionosphere through the VLF-NAA Signal Recordings

2011 ◽  
Vol 20 (4) ◽  
Author(s):  
Aleksandra Kolarski ◽  
Davorka Grubor ◽  
Desanka Šulić
Keyword(s):  
Wave Propagation ◽  
Solar Flare ◽  
Lower Ionosphere ◽  
Signal Amplitude ◽  
Lower Edge ◽  
X Ray ◽  
The Earth ◽  
Reflection Height ◽  
Propagation Parameters ◽  
Delay Variations

AbstractAn analysis of four solar flare X-ray irradiance effects on VLF signal amplitude and phase delay variations on the NAA/24.0 kHz signal trace during the period from 2005 September to 2006 December was carried out. Solar flare data were taken from the GOES12 satellite one-minute listings. For the VLF data, recordings at the Institute of Physics, Belgrade were used. It was found that solar flare events affect VLF wave propagation in the Earth-ionosphere waveguide lowering the changes of the ionosphere electron density height profiles. This follows from the variation during the solar flare events of the following propagation parameters: the sharpness of the lower edge of the ionosphere and the reflection height.

scholarly journals Modelling of the Electron Density and Total Electron Content in the Quiet and Solar X-ray Flare Perturbed Ionospheric D-Region Based on Remote Sensing by VLF/LF Signals

2021 ◽  
Vol 14 (1) ◽  
pp. 54
Author(s):  
Aleksandra Nina
Keyword(s):  
Remote Sensing ◽  
Electron Density ◽  
Total Electron Content ◽  
Low Frequency ◽  
Electron Content ◽  
Total Electron ◽  
X Ray ◽  
Causes Of Errors ◽  
D Region ◽  
The Times

Many analyses of the perturbed ionospheric D-region and its influence on the propagation of ground-based and satellite signals are based on data obtained in ionospheric remote sensing by very low/low frequency (VLF/LF) signals. One of the most significant causes of errors in these analyses is the lack of data related to the analysed area and time period preceding the considered perturbation. In this paper, we examine the influence of the estimation of the quiet ionosphere parameters on the determination of the electron density (Ne) and total electron content in the D-region (TECD) during the influence of a solar X-ray flare. We present a new procedure in which parameters describing the quiet ionosphere are calculated based on observations of the analysed area by a VLF/LF signal at the observed time. The developed procedure is an upgrade of the quiet ionospheric D-region (QIonDR) model that allows for a more precise analysis of the D-region intensively perturbed by a solar X-ray flare. The presented procedure is applied to data obtained in ionospheric remote sensing by the DHO signal emitted in Germany and received in Serbia during 30 solar X-ray flares. We give analytical expressions for the dependencies of the analysed parameters on the X-ray flux maximum at the times of the X-ray flux maximum and the most intense D-region perturbation. The results show that the obtained Ne and TECD are larger than in the cases when the usual constant values of the quiet ionosphere parameters are used.

Sign in / Sign up

Export Citation Format

Share Document