Response of the Earth’s Lower Ionosphere to Solar Flares and Lightning-Induced Electron Precipitation Events by Analysis of VLF Signals: Similarities and Differences

The lower ionosphere influences the propagation of electromagnetic (EM) waves, satellite and also terrestrial (anthropic) signals at the time of intense perturbations and disturbances. Therefore, data and modelling of the perturbed lower ionosphere are crucial in various technological areas. An analysis of the lower ionospheric response induced by sudden events during daytime-solar flares and during night-time-lightning-induced electron precipitation was carried out. A case study of the solar flare event recorded on 7 September 2017 and lightning-induced electron precipitation event recorded on 16 November 2004 were used in this work. Sudden events induced changes in the ionosphere and, consequently, the electron density height profile. All data are recorded by Belgrade (BEL) radio station system and the model computation is used to obtain the ionospheric parameters induced by these sudden events. According to perturbed conditions, variation of estimated parameters, sharpness and reflection height differ for analysed cases. Data and results are useful for Earth observation, telecommunication and other applications in modern society.

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

Annales Geophysicae ◽

10.5194/angeo-26-1731-2008 ◽

2008 ◽

Vol 26 (7) ◽

pp. 1731-1740 ◽

Cited By ~ 46

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.

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Night-time F-region and daytime E-region ionospheric drifts measured at Udaipur during solar flares

Annales Geophysicae ◽

10.5194/angeo-20-1837-2002 ◽

2002 ◽

Vol 20 (11) ◽

pp. 1837-1842 ◽

Cited By ~ 1

Author(s):

B. M. Vyas ◽

R. Pandey

Keyword(s):

Electric Fields ◽

Solar Flares ◽

Night Time ◽

Low Latitude ◽

F Region ◽

Reflection Height ◽

E Region ◽

Electric Fields And Currents ◽

East West ◽

Ionospheric Drifts

Abstract. Ionospheric drifts measured at a low latitude station, Udaipur (Geomag. Lat. 14.5° N), in the night-time F-region and daytime E-region during solar flares have been studied. The night-time observations, which correspond to the F-region drifts, were carried out on five different nights. The daytime observation corresponding to the E-region drifts is only for one day. It is found that the apparent drift during the solar flare period is reduced considerably, in the daytime E-region as well as in the night-time F-region. The East-West and North-South components of the apparent drift speed are also similarly affected. For the daytime E-region drifts during a flare, increased ionization and subsequent reduction of reflection height is proposed to be the cause of reduced drift speeds. For the night-time F-region drifts, a reduced electric field at the F-region heights resulting from coupling of sunlit and dark hemispheres has been proposed to be the possible cause.Key words. Ionosphere (electric fields and currents; ionospheric disturbances)

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

Scientific Reports ◽

10.1038/s41598-021-89662-x ◽

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.

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The effect of energetic electron precipitation on middle mesospheric night-time ozone during and after a moderate geomagnetic storm

Geophysical Research Letters ◽

10.1029/2012gl053787 ◽

2012 ◽

Vol 39 (21) ◽

pp. n/a-n/a ◽

Cited By ~ 27

Author(s):

M. Daae ◽

P. Espy ◽

H. Nesse Tyssøy ◽

D. Newnham ◽

J. Stadsnes ◽

...

Keyword(s):

Geomagnetic Storm ◽

Energetic Electron ◽

Electron Precipitation ◽

Night Time

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Energy spectra measured during a relativistic electron precipitation event on 2 February 1969

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/0021-9169(74)90199-8 ◽

1974 ◽

Vol 36 (10) ◽

pp. 1613-1622 ◽

Cited By ~ 24

Author(s):

T.R. Larsen ◽

G.R. Thomas

Keyword(s):

Relativistic Electron ◽

Electron Precipitation ◽

Energy Spectra ◽

Precipitation Event

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Relativistic electron dropouts by pitch angle scattering in the geomagnetic tail

Annales Geophysicae ◽

10.5194/angeo-24-3151-2006 ◽

2006 ◽

Vol 24 (11) ◽

pp. 3151-3159 ◽

Cited By ~ 9

Author(s):

J. J. Lee ◽

G. K. Parks ◽

K. W. Min ◽

M. P. McCarthy ◽

E. S. Lee ◽

...

Keyword(s):

Magnetic Field ◽

Relativistic Electron ◽

Magnetic Moment ◽

Pitch Angle ◽

Electron Flux ◽

Electron Precipitation ◽

Precipitation Event ◽

Real Field ◽

Geomagnetic Tail ◽

Angle Scattering

Abstract. Relativistic electron dropout (RED) events are characterized by fast electron flux decrease at the geostationary orbit. It is known that the main loss process is non adiabatic and more effective for the high energy particles. RED events generally start to occur at midnight sector and propagate to noon sector and are correlated with magnetic field stretching. In this paper, we discuss this kind of event can be caused from pitch angle diffusion induced when the gyro radius of the electrons is comparable to the radius of curvature of the magnetic field and the magnetic moment is not conserved any more. While this process has been studied theoretically, the question is whether electron precipitation could be explained with this process for the real field configuration. This paper will show that this process can successfully explain the precipitation that occurred on 14 June 2004 observed by the low-altitude (680 km) polar orbiting Korean satellite, STSAT-1. In this precipitation event, the energy dispersion showed higher energy electron precipitation occurred at lower L values. This feature is a good indicator that precipitation was caused by the magnetic moment scattering in the geomagnetic tail. This interpretation is supported by the geosynchronous satellite GOES observations that showed significant magnetic field distortion occurred on the night side accompanying the electron flux depletion. Tsyganenko-01 model also shows the magnetic moment scattering could occur under the geomagnetic conditions existing at that time. We suggest the pitch angle scattering by field curvature violating the first adiabatic invariant as a possible candidate for loss mechanism of relativistic electrons in radiation belt.

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