Traits of sub-kilometre F-region irregularities as seen with the Swarm satellites

Abstract. During the night, in the F-region, equatorial ionospheric irregularities manifest as plasma depletions observed by satellites, and they may cause radio signals to fluctuate. In this study, the distribution characteristics of ionospheric F-region irregularities in the low latitudes were investigated using 16 Hz electron density observations made by a faceplate which is a component of the electric field instrument (EFI) onboard Swarm satellites of the European Space Agency (ESA). The study covers the period from October 2014 to October 2018 when the 16 Hz electron density data were available. For comparison, both the absolute (dNe) and relative (dNe∕Ne) density perturbations were used to quantify the level of ionospheric irregularities. The two methods generally reproduced the local-time (LT), seasonal and longitudinal distribution of equatorial ionospheric irregularities as shown in earlier studies, demonstrating the ability of Swarm 16 Hz electron density data. A difference between the two methods was observed based on the latitudinal distribution of ionospheric irregularities where (dNe) showed a symmetrical distribution about the magnetic equator, while dNe∕Ne showed a magnetic-equator-centred Gaussian distribution. High values of dNe and dNe∕Ne were observed in spatial bins with steep gradients of electron density from a longitudinal and seasonal perspective. The response of ionospheric irregularities to geomagnetic and solar activities was also investigated using Kp index and solar radio flux index (F10.7), respectively. The reliance of dNe∕Ne on solar and magnetic activity showed little distinction in the correlation between equatorial and off-equatorial latitudes, whereas dNe showed significant differences. With regard to seasonal and longitudinal distribution, high dNe and dNe∕Ne values were often found during quiet magnetic periods compared to magnetically disturbed periods. The dNe increased approximately linearly from low to moderate solar activity. Using the high-resolution faceplate data, we were able to identify ionospheric irregularities on the scale of only a few hundred of metres.

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Traits of sub-kilometer F-region irregularities as seen with the Swarm satellites

10.5194/angeo-2019-50 ◽

2019 ◽

Author(s):

Sharon Aol ◽

Stephan Buchert ◽

Edward Jurua

Keyword(s):

Electron Density ◽

European Space Agency ◽

Ionospheric Irregularities ◽

Magnetic Equator ◽

Longitudinal Distribution ◽

Density Data ◽

Positive Correlation ◽

F Region ◽

Weak Positive Correlation ◽

Swarm Satellites

Abstract. During the night, in the F-region, equatorial ionospheric irregularities manifest as plasma depletions observed by satellites and may cause radio signals to fluctuate. In this study, the distribution characteristics of ionospheric F-region irregularities in the low latitudes were investigated using 16 Hz electron density observations made by the faceplate on board Swarm satellites of the European Space Agency (ESA). The study covers the period from October 2014 to October 2018 when the 16 Hz electron density data were available. For comparison, both the absolute (ΔNe) and relative (ΔNe/Ne) density perturbations were used to quantify the level of ionospheric irregularities. The two methods generally reproduced the local time, seasonal and longitudinal distribution of equatorial ionospheric irregularities as shown in earlier studies, demonstrating the ability of Swarm 16 Hz electron density data. A difference between the two methods was observed based on the latitudinal distribution of ionospheric irregularities where ΔNe showed a symmetrical distribution about the magnetic equator, whereas ΔNe/Ne showed a magnetic equator centered Gaussian distribution. High values of ΔNe and ΔNe/Ne were observed in spatial bins with steep gradients of electron density from a longitudinal and seasonal perspective. The response of ionospheric irregularities to geomagnetic and solar activities was also investigated using Kp index and solar radio flux index (F10.7), respectively. A weak positive correlation was obtained between the occurrence of ionospheric irregularities and Kp index, irrespective of the method adopted to quantify the irregularities. In general, both ΔNe and ΔNe/Ne showed a weak positive correlation with F10.7. However, a higher positive correlation was obtained between ΔNe and F10.7 compared to ΔNe/Ne. Using the high-resolution faceplate data, we were able to identify ionospheric irregularities of scales of only a few hundreds of meters.

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Study of mid-latitude nighttime enhancement in F-region electron density using tomographic images over the UK

Annales Geophysicae ◽

10.5194/angeo-21-2323-2003 ◽

2003 ◽

Vol 21 (12) ◽

pp. 2323-2328 ◽

Cited By ~ 15

Author(s):

R. S. Dabas ◽

L. Kersley

Keyword(s):

Electron Density ◽

Magnetic Activity ◽

Electron Content ◽

Equatorial Anomaly ◽

Tomographic Images ◽

F Region ◽

Electron Density Gradient ◽

Modeling And Forecasting ◽

Ionospheric Electron Content ◽

The Uk

Abstract. Nighttime enhancements in ionospheric electron content (IEC)/peak electron density (NmF2) have been studied by various workers in the equatorial anomaly and mid-latitude regions. Such studies give an idea about their enhancement over that location only. In the present study tomographic images over the UK, which give a latitudinal versus height distributions of ionospheric electron density in a much wider area, have been used to study the anomalous increases in nighttime F-region electron density at mid-latitudes. From the analysis of four seasonal representative months (November 1997, March, June and October 1998) data it was noted that the majority of the cases of nighttime enhancements were observed after local midnight, with a maximum between 03:00–04:00 LT in the month of November 1997. Enhancements were observed mostly between 45–50° N latitudes, and their positions are not affected by magnetic activity (Kp ) variations, whereas the separation between the mid-latitude trough and enhancement decreases with increases in magnetic activity. This finding shows that only the trough moves equatorward with the increase in magnetic activity. It is also noted that the electron density gradient from the trough to the enhancement increases with an increase in Kp. Results are discussed in terms of downward plasma transport from the protonosphere to the ionosphere and the nighttime neutral winds.Key words. Ionosphere (mid-latitude ionosphere; modeling and forecasting; instruments and techniques)

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Magnetic Field and Electron Density Data Analysis from Swarm Satellites Searching for Ionospheric Effects by Great Earthquakes: 12 Case Studies from 2014 to 2016

Atmosphere ◽

10.3390/atmos10070371 ◽

2019 ◽

Vol 10 (7) ◽

pp. 371 ◽

Cited By ~ 7

Author(s):

Angelo De Santis ◽

Dedalo Marchetti ◽

Luca Spogli ◽

Gianfranco Cianchini ◽

F. Javier Pavón-Carrasco ◽

...

Keyword(s):

Magnetic Field ◽

Electron Density ◽

Geomagnetic Latitude ◽

Statistical Correlation ◽

Satellite Mission ◽

Strong Earthquakes ◽

Density Data ◽

Ionospheric Effects ◽

Swarm Satellites ◽

Swarm Satellite

We analyse Swarm satellite magnetic field and electron density data one month before and one month after 12 strong earthquakes that have occurred in the first 2.5 years of Swarm satellite mission lifetime in the Mediterranean region (magnitude M6.1+) or in the rest of the world (M6.7+). The search for anomalies was limited to the area centred at each earthquake epicentre and bounded by a circle that scales with magnitude according to the Dobrovolsky’s radius. We define the magnetic and electron density anomalies statistically in terms of specific thresholds with respect to the same statistical quantity along the whole residual satellite track (|geomagnetic latitude| ≤ 50°, quiet geomagnetic conditions). Once normalized by the analysed satellite tracks, the anomalies associated to all earthquakes resemble a linear dependence with earthquake magnitude, so supporting the statistical correlation with earthquakes and excluding a relationship by chance.

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AIM-E auroral ionosphere model adjustment for the regular E layer

Solar-Terrestrial Physics ◽

10.12737/stp-71202106 ◽

2021 ◽

Vol 7 (1) ◽

pp. 41-46

Author(s):

Vera Nikolaeva ◽

Evgeniy Gordeev ◽

Denis Rogov ◽

Aleksandr Nikolaev

Keyword(s):

Electron Density ◽

Input Parameter ◽

Magnetic Activity ◽

Auroral Zone ◽

Auroral Ionosphere ◽

Solar Radio Flux ◽

Ionosphere Model ◽

E Region ◽

Ap Index ◽

Euv Spectrum

The E-Region Auroral Ionosphere Model (AIM-E) was developed to determine the chemical composition and electron density in the auroral zone at E-layer heights (90–150 km). Solar and magnetic activity input parameters for AIM-E are the three-hour Ap index and the daily solar radio flux at a wavelength of 10.7 cm (index F10.7). In this paper, we compare AIM-E calculations of the electron density for the daytime with EUV radiation spectrum specified in two different ways: 1) the EUV spectrum theoretically calculated using the F10.7 index as an input parameter; 2) using TIMED satellite direct measurements of the EUV spectrum. We have corrected the EUVAC EUV radiation model to specify a photoionization source in AIM-E. Calculations of regular E-region critical frequencies show good agreement with the vertical sounding data from Russian high-latitude stations. Results we obtained make it possible to do a quick on-line assessment of the regular E layer, using the daily index F10.7 as an input parameter.

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F-Region nightglow emissions of atomic oxygen: 2. Analysis of 6300 A and electron density data

Journal of Geophysical Research Atmospheres ◽

10.1029/jz071i009p02267 ◽

1966 ◽

Vol 71 (9) ◽

pp. 2267-2277 ◽

Cited By ~ 21

Author(s):

Vern L. Peterson ◽

Walter R. Steiger

Keyword(s):

Electron Density ◽

Atomic Oxygen ◽

Density Data ◽

F Region

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AIM-E auroral ionosphere model adjustment for the regular E layer

Solnechno-Zemnaya Fizika ◽

10.12737/szf-71202106 ◽

2021 ◽

Vol 7 (1) ◽

pp. 51-58

Author(s):

Vera Nikolaeva ◽

Evgeniy Gordeev ◽

Denis Rogov ◽

Aleksandr Nikolaev

Keyword(s):

Electron Density ◽

Input Parameter ◽

Magnetic Activity ◽

Auroral Zone ◽

Auroral Ionosphere ◽

Solar Radio Flux ◽

Ionosphere Model ◽

E Region ◽

Ap Index ◽

Euv Spectrum

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Ionospheric irregularities and scintillations: a direct comparison of in situ density observations with ground-based L-band receivers

Earth Planets and Space ◽

10.1186/s40623-020-01294-z ◽

2020 ◽

Vol 72 (1) ◽

Author(s):

Sharon Aol ◽

Stephan Buchert ◽

Edward Jurua

Keyword(s):

Electron Density ◽

Satellite Communication ◽

Density Fluctuations ◽

Ionospheric Irregularities ◽

Langmuir Probes ◽

Amplitude Scintillation ◽

Swarm Satellites ◽

L Band ◽

Electron Density Fluctuations

Abstract Ionospheric irregularities can affect satellite communication and navigation by causing scintillations of radio signals. The scintillations are routinely measured using ground-based networks of receivers. This study presents observations of ionospheric irregularities by Langmuir probes on the Swarm satellites. They are compared with amplitude scintillation events recorded by the Global Positioning System-Scintillation Network and Decision Aid (GPS-SCINDA) receiver installed in Mbarara (Lat: $$0.6^{\circ }\hbox {S}$$ 0 . 6 ∘ S , Lon: $$30.8^{\circ }\hbox {E}$$ 30 . 8 ∘ E , Mag. lat: $$10.2^{\circ }\hbox {S}$$ 10 . 2 ∘ S ). The study covers the years from 2014 to 2018 when both data sets were available. It was found that the ground-based amplitude scintillations were enhanced when Swarm registered ionospheric irregularities for a large number of passes. The number of matching observations was greater for Swarm A and C which orbited at lower altitudes compared to Swarm B. However, some counterexamples, i.e., cases when in situ electron density fluctuations were not associated with any observed L-band amplitude scintillation and vice versa, were also found. Therefore, mismatches between observed irregularity structures and scintillations can occur just over a few minutes and within distances of a few tens of kilometers. The amplitude scintillation strength, characterized by the S4 index was estimated from the electron density data using the well-known phase screen model for weak scattering. The derived amplitude scintillation was on average lower for Swarm B than for A and C and less in accordance with the observed range. Irregularities at an altitude of about 450 km contribute strongly to scintillations in the L-band, while irregularities at about 510-km altitude contribute significantly less. We infer that in situ density fluctuations observed on passes over or near Mbarara may be used to indicate the risk that ionospheric radio wave scintillations occur at that site.

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Total electron content and F-region electron density distribution near the magnetic equator in India

Journal of Atmospheric and Terrestrial Physics ◽

10.1016/0021-9169(79)90053-9 ◽

1979 ◽

Vol 41 (6) ◽

pp. 561-564 ◽

Cited By ~ 16

Author(s):

R.G Rastogi ◽

G Sethia ◽

H Chandra ◽

M.R Deshpande ◽

K Davies ◽

...

Keyword(s):

Density Distribution ◽

Electron Density ◽

Total Electron Content ◽

Electron Density Distribution ◽

Magnetic Equator ◽

Electron Content ◽

Total Electron ◽

F Region

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A study of atmospheric gravity waves and travelling ionospheric disturbances at equatorial latitudes

Annales Geophysicae ◽

10.1007/s00585-997-1048-4 ◽

1997 ◽

Vol 15 (8) ◽

pp. 1048-1056 ◽

Cited By ~ 41

Author(s):

R. L. Balthazor ◽

R. J. Moffett

Keyword(s):

Gravity Waves ◽

Large Scale ◽

Ionospheric Disturbance ◽

Magnetic Equator ◽

Ionospheric Disturbances ◽

Atmospheric Gravity Waves ◽

Opposite Hemisphere ◽

Travelling Ionospheric Disturbances ◽

F Region ◽

Atmospheric Gravity

Abstract. A global coupled thermosphere-ionosphere-plasmasphere model is used to simulate a family of large-scale imperfectly ducted atmospheric gravity waves (AGWs) and associated travelling ionospheric disturbances (TIDs) originating at conjugate magnetic latitudes in the north and south auroral zones and subsequently propagating meridionally to equatorial latitudes. A 'fast' dominant mode and two slower modes are identified. We find that, at the magnetic equator, all the clearly identified modes of AGW interfere constructively and pass through to the opposite hemisphere with unchanged velocity. At F-region altitudes the 'fast' AGW has the largest amplitude, and when northward propagating and southward propagating modes interfere at the equator, the TID (as parameterised by the fractional change in the electron density at the F2 peak) increases in magnitude at the equator. The amplitude of the TID at the magnetic equator is increased compared to mid-latitudes in both upper and lower F-regions with a larger increase in the upper F-region. The ionospheric disturbance at the equator persists in the upper F-region for about 1 hour and in the lower F-region for 2.5 hours after the AGWs first interfere, and it is suggested that this is due to enhancements of the TID by slower AGW modes arriving later at the magnetic equator. The complex effects of the interplays of the TIDs generated in the equatorial plasmasphere are analysed by examining neutral and ion winds predicted by the model, and are demonstrated to be consequences of the forcing of the plasmasphere along the magnetic field lines by the neutral air pressure wave.

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