Comparison of the tidal signatures in sporadic E and vertical ion convergence rate, using FORMOSAT-3/COSMIC radio occultation observations and GAIA model

Sobhkhiz-Miandehi, Sahar; Yamazaki, Yosuke; Arras, Christina; Miyoshi, Y.; Shinagawa, Hiroyuki

doi:10.1186/s40623-022-01637-y

Cited by 15 publications

(11 citation statements)

References 49 publications

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“…The variation of the phase with altitude leads to a vertical shear of the winds. The vertical shear of the zonal wind induced by tidal waves is known to be an important cause of Es layers at mid latitudes (Arras et al., 2009; Sobhkhiz‐Miandehi et al., 2022). Figure 2 also depicts considerable day‐to‐day variability in the wind velocities.…”

Section: Resultsmentioning

confidence: 99%

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

Qiu,

Yamazaki,

et al. 2023

JGR Space Physics

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In previous studies, various physical parameters, such as vertical wind shear null, vertical ion velocity null (IVN), and maximum gradient of vertical ion velocity, have been used as an indicator of Es layer height in light of the wind shear theory. Using a numerical Es layer model, we investigated which parameter represents the height of Es layer over Wuhan (114.4°E, 30.5°N) most precisely. The simulation results show that the height of Es layer above 110 km depends most strongly on the height of vertical IVN. However, below 110 km, the height of vertical IVN does not always agree with the height of Es layer. The analysis of simulation results suggests that the vertical gradient of the ratio of the ion‐neutral collision frequency (νi) to the ion gyrofrequency (ωi) affects the Es layer formation at lower altitudes (below 110 km). We also examined the effect of electric fields on the height and intensity of Es layers over Wuhan. It is found that eastward/upward electric fields can lift the Es layer height and reduce the Es layer intensity.

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Section: Resultsmentioning

confidence: 99%

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

Qiu,

Yamazaki,

et al. 2023

JGR Space Physics

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“…The wind shear theory [16,17] is widely accepted as describing the principal mechanism behind mid-latitude Es-layer formation, by which vertical gradients in the zonal wind concentrate the metal ions into narrow height ranges [5,18] through Lorentz forces. Observations that directly support this theory have recently come from a number of GNSS radio occultation and ionosonde studies e.g., [19,20]. For a more comprehensive overview of the characteristics of sporadic-E, see our earlier article [21], Section II and references therein.…”

Section: Introductionmentioning

confidence: 95%

“…Lorentz forces. Observations that directly support this theory have recently come from a number of GNSS radio occultation and ionosonde studies e.g., [19,20]. For a more comprehensive overview of the characteristics of sporadic-E, see our earlier article [21], Section II and references therein.…”

Section: Introductionmentioning

confidence: 95%

Evidence for the Magnetoionic Nature of Oblique VHF Reflections from Midlatitude Sporadic-E Layers

et al. 2022

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Mid-latitude sporadic-E (Es) is an intermittent phenomenon of the lower E region of the ionosphere. Es clouds are thin, transient, and patchy layers of intense ionization, with ionization densities which can be much higher than in the background ionosphere. Oblique reflection of radio signals in the very high frequency (VHF) range is regularly supported, but the mechanism for it has never been clearly established—specular reflection, scattering, and magnetoionic double refraction have all been suggested. This article proposes using the polarization behaviour of signals reflected from intense midlatitude sporadic-E clouds as an indicator of the true reflection mechanism. Results are presented from a measurement campaign in the summer of 2018, which gathered a large amount of data at a receiving station in the UK using 50 MHz amateur radio beacons as signal sources. In all cases the signals received were elliptically polarized, despite being transmitted with linear polarization; there were also indications that polarization behaviour varied systematically with the orientation of the path to the geomagnetic field. This represents, for all the examples recorded, clear evidence that signals were reflected from midlatitude Es by magnetoionic double refraction.

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“…The layer‐forming process is also affected by atmospheric tides forced by solar radiation (Haldoupis, 2011). The diurnal, semidiurnal (Arras et al., 2009; Haldoupis, 2004), terdiurnal, and quarterdiurnal (Fytterer et al., 2014; Jacobi et al., 2019; Sobhkhiz‐Miandehi et al., 2022) tidal components of the Es layer occurrence rate have been revealed by observations.…”

Section: Introductionmentioning

confidence: 97%

Numerical Simulations of Metallic Ion Density Perturbations in Sporadic E Layers Caused by Gravity Waves

Qiu,

Yamazaki,

et al. 2023

Earth and Space Science

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Tidal signatures in sporadic E (Es) layer have been confirmed by observations and simulations. However, the effect of gravity waves (GWs) on the Es layer formation process has not yet been fully understood. In this paper, the modulation of Es layers by GWs is examined through numerical simulations, in which a physics‐based model of Es layer is forced by neutral winds from the High Altitude Mechanistic General Circulation Model that can resolve GWs with horizontal wavelengths longer than 156 km (λh > 156 km). Comparison of the simulation results with and without the GWs (1,350 km > λh > 156 km) forcing reveals that the inclusion of GWs leads to short‐period (1.2–3 hr) density perturbations in Es layers, which are also seen in ground‐based ionosonde observations. At a given time, the metallic ion density at altitudes between 120 and 150 km can either increase (by up to ∼+600%) or reduce (by up to −90%) in response to GW forcing. The relative density perturbations are smaller (by up to 60%) between 90 and 120 km altitude. It is also found that the GW effect on the metallic ion density relates to the longitude, which is mostly explained by the geographical distribution of GWs activity in the mesosphere and lower thermosphere region. The longitudinal variation of the background geomagnetic field plays only a secondary role.

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Comparison of the tidal signatures in sporadic E and vertical ion convergence rate, using FORMOSAT-3/COSMIC radio occultation observations and GAIA model

Cited by 15 publications

References 49 publications

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

Numerical Investigation on the Height and Intensity Variations of Sporadic E Layers at Mid‐Latitude

Evidence for the Magnetoionic Nature of Oblique VHF Reflections from Midlatitude Sporadic-E Layers

Numerical Simulations of Metallic Ion Density Perturbations in Sporadic E Layers Caused by Gravity Waves

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