Spatial variability in the ionosphere measured with GNSS networks

Emardson, Ragne; Jarlemark, Per; Johansson, Jan M.; Schäfer, Sebastian

doi:10.1002/2013rs005152

Cited by 8 publications

(5 citation statements)

References 18 publications

(21 reference statements)

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“…The morphology of MSTIDs varies with local time, season, and magnetic longitude. Their propagation shows irregular patterns that vary on a caseby-case basis, although they commonly seem to propagate mainly equatorward during winter daytime and westward during summer night-time (Saito & Fukao, 1998;Hernández-Pajares et al, 2006, 2012Tsugawa et al, 2007;Emardson et al, 2013). Smaller-scale ionisation gradients, likely associated with the Perkins instability (Kelley, 2009(Kelley, , 2011, can then form as a consequence of the presence of MSTIDs, potentially leading to scintillation at LOFAR frequencies.…”

Section: Introductionmentioning

confidence: 99%

A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

Fallows

Forte

Astin

et al. 2020

J. Space Weather Space Clim.

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This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source Cassiopeia A, taken overnight on 18–19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10–80 MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A cross-correlation analysis of data received by the dense array of stations in the LOFAR “core” reveals two different velocities in the scintillation pattern: a primary velocity of ~20–40 ms−1 with a north-west to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ~110 ms−1 with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller-scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported.

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Section: Introductionmentioning

confidence: 99%

A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

Fallows

Forte

Astin

et al. 2020

J. Space Weather Space Clim.

View full text Add to dashboard Cite

show abstract

“…The morphology of MSTIDs varies with local time, season, and magnetic longitude. Their propagation shows irregular patterns that vary on a case-by-case basis, although they commonly seem to propagate mainly equatorward during winter daytime and westward during summer night-time (Hernández-Pajares et al, 2006, 2012Tsugawa et al, 2007;Saito and Fukao, 1998;Emardson et al, 2013). Smaller-scale ionisation gradients, likely associated with the Perkins instability (Kelley, 2009(Kelley, , 2011, can then form as a consequence of the presence of MSTIDs, potentially leading to scintillation at LOFAR frequencies.…”

Section: Introductionmentioning

confidence: 99%

A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances

Fallows¹,

Forte²,

Astin³

et al. 2020

Preprint

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This paper presents the results from one of the first observations of ionospheric scintillation taken using the Low-Frequency Array (LOFAR). The observation was of the strong natural radio source 2 Fallows et al.: LOFAR Ionospheric ScintillationCassiopeia A, taken overnight on 18-19 August 2013, and exhibited moderately strong scattering effects in dynamic spectra of intensity received across an observing bandwidth of 10-80 MHz. Delay-Doppler spectra (the 2-D FFT of the dynamic spectrum) from the first hour of observation showed two discrete parabolic arcs, one with a steep curvature and the other shallow, which can be used to provide estimates of the distance to, and velocity of, the scattering plasma. A crosscorrelation analysis of data received by the dense array of stations in the LOFAR "core" reveals two different velocities in the scintillation pattern: a primary velocity of ∼20-40 m s −1 with a northwest to south-east direction, associated with the steep parabolic arc and a scattering altitude in the F-region or higher, and a secondary velocity of ∼110 m s −1 with a north-east to south-west direction, associated with the shallow arc and a scattering altitude in the D-region. Geomagnetic activity was low in the mid-latitudes at the time, but a weak sub-storm at high latitudes reached its peak at the start of the observation. An analysis of Global Navigation Satellite Systems (GNSS) and ionosonde data from the time reveals a larger-scale travelling ionospheric disturbance (TID), possibly the result of the high-latitude activity, travelling in the north-west to south-east direction, and, simultaneously, a smaller-scale TID travelling in a north-east to south-west direction, which could be associated with atmospheric gravity wave activity. The LOFAR observation shows scattering from both TIDs, at different altitudes and propagating in different directions. To the best of our knowledge this is the first time that such a phenomenon has been reported.

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“…Global, high‐latitude response of TEC is the result of numerous complex geospatial processes, each with unique spatial and temporal scales [ Mendillo , ; Shim , ; Emardson et al , ]. Therefore, TEC data are rich with information about the Earth's space environment.…”

Section: Introductionmentioning

confidence: 99%

“…We present a new approach to the analysis of high-latitude, hemispheric-specific, TEC data known as network analysis. Network analysis [Boccaletti et al, 2006] has been a valuable tool in many fields of research, originating in the social sciences [Milgram, 1967] and finding more recent application in biological, engineering, and geophysical systems [Tsonis et al, 2006;Donges et al, 2009;Steinhaeuser et al, 2012;Malik et al, 2012;Dods et al, 2015Dods et al, , 2017. However, this methodology has never before been applied to TEC data.…”

Section: Introductionmentioning

confidence: 99%

Finding multiscale connectivity in our geospace observational system: Network analysis of total electron content

et al. 2017

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We present the first complex network theory‐based analysis of high‐latitude total electron content (TEC) data, including dependencies on interplanetary magnetic field (IMF) clock angle and hemisphere. We examine several network measures to quantify the spatiotemporal correlation patterns in the TEC data for winter and summer months in 2016. We find that significant structure exists in the correlation patterns, distinguishing the dayside and nightside ionosphere, and specific features in the high latitudes such as the polar cap and auroral oval, including the cusp and ionospheric foot points of magnetospheric boundary layers. These features vary with the IMF, exhibiting a strong dependence on the north‐south direction and generally larger variations during the winter months in both hemispheres. Our exploratory results suggest that network analysis of TEC data can be used to study characteristic ionospheric spatial scales at high latitudes, thereby extending the utility of these data. We explore mesoscale and large scale (greater than tens of kilometers and greater than hundreds of kilometers, respectively) as a function of winter/summer season, hemisphere, and IMF direction and conclude that the relative importance of different ionospheric scales is not a constant relationship. Together with an identification of important areas of future work, our findings provide a foundation for the application of network analysis techniques to ionospheric TEC. Our results suggest that network analysis can reveal new physical connections in the ionospheric system.

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Spatial variability in the ionosphere measured with GNSS networks

Cited by 8 publications

References 18 publications

A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

A LOFAR observation of ionospheric scintillation from two simultaneous travelling ionospheric disturbances

A LOFAR Observation of Ionospheric Scintillation from Two Simultaneous Travelling Ionospheric Disturbances

Finding multiscale connectivity in our geospace observational system: Network analysis of total electron content

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