scholarly journals A comparative study of measured amplitude and phase perturbations of VLF and LF radio signals induced by solar flares

2014 ◽  
pp. 45-54 ◽  
Author(s):  
D.M. Sulic ◽  
V.A. Sreckovic
Keyword(s):  
Solar Flares ◽  
Low Frequency ◽  
Geographic Location ◽  
Electron Density Profile ◽  
Great Circle ◽  
Direct Result ◽  
Ionospheric Disturbances ◽  
X Ray ◽  
Radio Signals ◽  
Middle Europe

Very Low Frequency (VLF) and Low Frequency (LF) signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver?s geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe.

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 Low Ionosphere under Influence of Strong Solar Radiation: Diagnostics and Modeling

2021 ◽  
Vol 11 (16) ◽  
pp. 7194
Author(s):  
Vladimir A. Srećković ◽  
Desanka M. Šulić ◽  
Ljubinko Ignjatović ◽  
Veljko Vujčić
Keyword(s):  
Solar Radiation ◽  
Solar Flares ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
D Region ◽  
Radio Signals ◽  
The Impact ◽  
First Time ◽  
Region Plasma ◽  
Intense Radiation

Solar flares (SFs) and intense radiation can generate additional ionization in the Earth’s atmosphere and affect its structure. These types of solar radiation and activity create sudden ionospheric disturbances (SIDs), affect electronic equipment on the ground along with signals from space, and potentially induce various natural disasters. Focus of this work is on the study of SIDs induced by X-ray SFs using very low frequency (VLF) radio signals in order to predict the impact of SFs on Earth and analyze ionosphere plasmas and its parameters. All data are recorded by VLF BEL stations and the model computation is used to obtain the daytime atmosphere parameters induced by this extreme radiation. The obtained ionospheric parameters are compared with results of other authors. For the first time we analyzed physics of the D-region—during consecutive huge SFs which continuously perturbed this layer for a few hours—in detail. We have developed an empirical model of the D-region plasma density and gave a simple approximative formula for electron density.

scholarly journals X-Ray Solar Flares Observed and Detected by The New Very-Low-Frequency Receiver in Nasiriyah City, South of Iraq

2021 ◽  
Vol 32 (2) ◽  
pp. 58
Author(s):  
Habeeb Allawi ◽  
Moataz Jasim ◽  
Kareem Abdulameer Difar
Keyword(s):  
Solar Flares ◽  
Ionospheric Disturbance ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
Very Low Frequency ◽  
Radio Signals ◽  
South Of Iraq ◽  
Set Up ◽  
June July ◽  
To Receive

A receiver station was installed at Nasiriyah (Dhi Qar University - Faculty of Sciences) to receive very low frequency (VLF) radio signals from transmitters around the world. VLF waves are excellent probes of the sudden ionospheric disturbance (SID); they detect varying properties of the D layer presented as a lower region of the ionosphere when these waves propagate through the Earth-Ionosphere Waveguide. This study describes the set-up of our station system and it demonstrates its ability to detect sudden ionospheric disturbances caused by solar flares in May, June, July, August, and September 2017. We found out that the monitoring station is working successfully to receive FLV signals, and to detect sudden ionospheric disturbances. We detected 17 events resulting from solar flare C-class, 8 events from M-class, and 3 events from X-class that caused an increase in the received FLV amplitude.

Observation and Analysis of Solar Flares that Cause Large-area Short-wave Communication Interruption

2021 ◽  
Author(s):  
Zhou Kangpo ◽  
Niu youtian ◽  
Liu weina ◽  
Wang zhaodi ◽  
Guo songhao ◽  
...  
Keyword(s):  
Solar Flares ◽  
Ionospheric Disturbance ◽  
Low Frequency ◽  
High Energy ◽  
Short Wave ◽  
Absorption Capacity ◽  
X Rays ◽  
Large Area ◽  
Radio Signals ◽  
Shortwave Communication

Abstract When a solar flare erupts, the sun emits a flood of X-rays and high-energy particles that reach Earth at the speed of light, causing a sudden ionospheric disturbance event (SID event). The D layer of the ionosphere absorbs high-frequency radio signals. With the increase of flare intensity, the D layer's absorption capacity becomes stronger, which leads to the decline of shortwave communication quality and even the interruption of shortwave communication. In this paper, solar flares, which caused large area short-wave communication interruption in recent years, are observed and analyzed by very low frequency (VLF) method, and the influence of solar flares on short-wave communication is summarized. Finally, several methods to deal with the short-wave communication interruption caused by solar flares are proposed.

scholarly journals Development of a Radio Telescope for Very Low Frequency Observations

2020 ◽  
Vol 240 ◽  
pp. 07004
Author(s):  
Arpit Gupta ◽  
Seow Kit Hint ◽  
Cao Shangyu ◽  
Hoe Teck Tan
Keyword(s):  
Data Collection ◽  
Solar Flare ◽  
Radio Telescope ◽  
Background Noise ◽  
Ionospheric Disturbance ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
X Ray ◽  
Very Low Frequency ◽  
Solar Storm

Sudden ionospheric disturbances are transient changes in the ionosphere caused by enhancement in X-ray and EUV fluxes during solar flare events. The Solar Storm Radio Telescope is developed to detect Very Low Frequency (VLF) signals with frequency between 3-30 kHz transmitted from various VLF stations around the Globe. We will also be investigating different methods to reduce the background noise in the data collection. This will help to ensure an accurate hit when there is a sudden ionospheric disturbance.

Detection of Sudden Ionospheric Disturbances due to Solar flares by monitoring the Very Low Frequency signal at Malda

2010 ◽  
Author(s):  
Nilmadhab Nandy ◽  
Achintya K. Chatterjee ◽  
Md. Washimul Bari ◽  
Asit K. Choudhury ◽  
Sandip K. Chakrabarti
Keyword(s):  
Solar Flares ◽  
Low Frequency ◽  
Ionospheric Disturbances ◽  
Frequency Signal ◽  
Very Low Frequency

scholarly journals Strong influence of solar X-ray flares on low-frequency electromagnetic signals in middle latitudes

2019 ◽  
Author(s):  
Alexandr Rozhnoi ◽  
Mariya Solovieva ◽  
Viktor Fedun ◽  
Peter Gallagher ◽  
Joseph McCauley ◽  
...  
Keyword(s):  
Solar Flares ◽  
Low Frequency ◽  
Signal Frequency ◽  
Frequency Range ◽  
Effective Height ◽  
X Ray ◽  
Middle Latitudes ◽  
Burst Data ◽  
Path Lengths ◽  
Electromagnetic Signals

Abstract. In this paper we analysed Sudden Phase Anomalies (SPAs) of VLF/LF signals recorded at Graz (Austria), Birr (Ireland) and Moscow (Russia) stations during two strong solar flares in September 2017. The first X-class 9.3 flare occurred on 6 September at 12:02 UT and the second X-class 8.2 flare was observed on 10 September 2017 at 16:06 UT. Data from seven transmitters in a frequency range between 20–45 kHz are used for the analysis. The SPAs were observed in all middle-latitudes paths (differently orientated) with path lengths from 350 km to 7000 km. Solar X-ray burst data were taken from GOES satellite observations in the wavelength band of 0.05–0.4 nm. If was found that (i) the amplitude of SPAs in different paths varies from 10 to 282 degrees, and (ii) the correlation between the amplitudes of SPAs, the lengths of paths and the signal frequency is weak. The change in effective height of reflection due to lowering of the reflecting layer during the flares was found to be about 12 km for the first event and about 9 km for the second event. Spectral analysis of the X-ray and LF data, filtered in the range between 5 s and 16 min, showed that the LF signal spectra are very similar to X-ray spectra. Maxima of both X-ray and LF spectra are in 2–16 min interval.

scholarly journals The corona of GJ 1151 in the context of star–planet interaction

2020 ◽  
Vol 497 (1) ◽  
pp. 1015-1019
Author(s):  
G Foster ◽  
K Poppenhaeger ◽  
J D Alvarado-Gómez ◽  
J H M M Schmitt
Keyword(s):  
Radio Emission ◽  
Low Frequency ◽  
Mass Star ◽  
Coronal Temperature ◽  
X Ray ◽  
Upper Limit ◽  
Radio Signals ◽  
Low Mass ◽  
Time Periods

ABSTRACT The low-mass star GJ 1151 has been reported to display variable low-frequency radio emission, which has been interpreted as a signpost of coronal star–planet interactions with an unseen exoplanet. Here we report the first X-ray detection of GJ 1151’s corona based on the XMM–Newton data. We find that the star displays a small flare during the X-ray observation. Averaged over the observation, we detect the star with a low coronal temperature of 1.6 MK and an X-ray luminosity of LX = 5.5 × 1026 erg s−1. During the quiescent time periods excluding the flare, the star remains undetected with an upper limit of $L_{\mathrm{ X},\, \mathrm{ qui}} \le 3.7\times 10^{26}$ erg s−1. This is compatible with the coronal assumptions used in a recently published model for a star–planet interaction origin of the observed radio signals from this star.

scholarly journals Strong influence of solar X-ray flares on low-frequency electromagnetic signals in middle latitudes

2019 ◽  
Vol 37 (5) ◽  
pp. 843-850
Author(s):  
Alexander Rozhnoi ◽  
Maria Solovieva ◽  
Viktor Fedun ◽  
Peter Gallagher ◽  
Joseph McCauley ◽  
...  
Keyword(s):  
Solar Flares ◽  
Low Frequency ◽  
Middle Latitude ◽  
Signal Frequency ◽  
Effective Height ◽  
X Ray ◽  
Middle Latitudes ◽  
Burst Data ◽  
Path Lengths ◽  
Electromagnetic Signals

Abstract. In this paper we analysed sudden phase anomalies (SPAs) of VLF–LF signals recorded at Graz (Austria), Birr (Ireland) and Moscow (Russia) stations during two strong solar flares in September 2017. The first X-class 9.3 flare occurred on 6 September at 12:02 UT, and the second X-class 8.2 flare was observed on 10 September 2017 at 16:06 UT. Data from seven transmitters in a frequency range between 20 and 45 kHz are used for the analysis. The SPAs were observed in all middle-latitude paths (differently orientated) with path lengths from 350 to 7000 km. Solar X-ray burst data were taken from GOES satellite observations in the wavelength band of 0.05–0.4 nm. It was found that (i) the amplitude of SPAs in different paths varies from 10 to 282∘, and (ii) the correlation between the amplitudes of SPAs, the lengths of paths and the signal frequency is weak. The change in effective height of reflection due to lowering of the reflecting layer during the flares was found to be about 12 km for the first event and about 9 km for the second event. Spectral analysis of the X-ray and LF data, filtered in the range between 5 s and 16 min, showed that the LF signal spectra are very similar to X-ray spectra. Maxima of both X-ray and LF spectra are in 2–16 min interval.

The occurrence of single hard x-ray sources in solar flares

2003 ◽  
Vol 32 (12) ◽  
pp. 2483-2488
Author(s):  
C GOFF ◽  
S MATTHEWS ◽  
L HARRA
Keyword(s):  
Solar Flares ◽  
X Ray
Sign in / Sign up

Export Citation Format

Share Document