Tidal signatures in sporadic E occurrence rates - migrating and nonmigrating components, and comparison with neutral wind shear

2021 ◽  
Author(s):  
Christoph Jacobi ◽  
Kanykei Kandieva ◽  
Christina Arras
Keyword(s):  
Wind Shear ◽  
Signal To Noise Ratio ◽  
Ion Concentration ◽  
Vertical Shear ◽  
Neutral Wind ◽  
High Electron ◽  
Phase Measurements ◽  
Middle Latitudes ◽  
E Region ◽  
Sporadic E

<p>In the lower ionospheric E region, shallow regions of high electron density are found, which are called sporadic E (ES) layers. ES layers consist of thin clouds of accumulated ions. They occur mainly at middle latitudes, and they are most frequently found during the summer season. ES are generally formed at heights between 90 and 120 km. At midlatitudes, their occurrence can be described through the wind shear theory. According to this theory, ES formation is due to interaction between the metallic ion concentration, the Earth’s magnetic field, and the vertical shear of the neutral wind. Here, we analyze ES occurrence rates (OR) obtained from ionospheric radio occultation measurements by the FORMOSAT-3/COSMIC constellation. To derive information on ES from RO, we use the Signal-to-Noise ratio (SNR) profiles of the GPS L1 phase measurements. If large SNR standard deviation values occur that are concentrated within a layer of less than 10 km thickness, we assume that the respective SNR profile disturbance is owing to an ES layer.</p><p>Midlatitude ES are found to be mainly connected with a migrating diurnal and semidiurnal component. Especially at high latitudes of the southern hemisphere, nonmigrating components such as a diurnal westward wave 2 and a semidiurnal westward wave 1 are also visible. Near the equator, a strong diurnal eastward wavenumber 3 component and a semidiurnal eastward wavenumber 2 component are found in summer and autumn. Terdiurnal and quarterdiurnal components are weaker than the diurnal and semidiurnal ones. We discuss seasonal and global distributions of migrating and nonmigrating components, and their relation to neutral wind shear derived from ground-based observations and numerical modeling.</p>

scholarly journals Tidal wind shear observed by meteor radar and comparison with sporadic E occurrence rates based on GPS radio occultation observations

2019 ◽  
Vol 17 ◽  
pp. 213-224
Author(s):  
Christoph Jacobi ◽  
Christina Arras
Keyword(s):  
Wind Shear ◽  
Radio Occultation ◽  
Signal To Noise Ratio ◽  
Lower Thermosphere ◽  
Horizontal Component ◽  
Meteor Radar ◽  
Good Correspondence ◽  
Gps Radio Occultation ◽  
Middle Latitudes ◽  
Sporadic E

Abstract. We analyze tidal (diurnal, semidiurnal, terdiurnal, quarterdiurnal) phases and related wind shear in the mesosphere/lower thermosphere as observed by meteor radar over Collm (51.3∘ N, 13.0∘ E). The wind shear phases are compared with those of sporadic E (Es) occurrence rates, which were derived from GPS radio occultation signal-to-noise ratio (SNR) profiles measured by the COSMIC/FORMOSAT-3 satellites. At middle latitudes Es are mainly produced by wind shear, which, in the presence of a horizontal component of the Earth's magnetic field, leads to ion convergence in the region where the wind shear is negative. Consequently, we find good correspondence between radar derived wind shear and Es phases for the semidiurnal, terdiurnal, and quarterdiurnal tidal components. The diurnal tidal wind shear, however, does not correspond to the Es diurnal signal.

scholarly journals Study of sporadic E layers based on GPS radio occultation measurements and digisonde data over the Brazilian region

2018 ◽  
Vol 36 (2) ◽  
pp. 587-593 ◽  
Author(s):  
Laysa C. A. Resende ◽  
Christina Arras ◽  
Inez S. Batista ◽  
Clezio M. Denardini ◽  
Thainá O. Bertollotto ◽  
...  
Keyword(s):  
Radio Occultation ◽  
Signal To Noise Ratio ◽  
Satellite Measurements ◽  
Low Latitude ◽  
Middle Latitudes ◽  
Sporadic E Layers ◽  
Sporadic E ◽  
Comparative Results ◽  
Layer Development ◽  
Good Agreement

Abstract. This work presents new results about sporadic E-layers (Es layers) using GPS (global positioning system) radio occultation (RO) measurements obtained from the FORMOSAT-3/COSMIC satellites and digisonde data. The RO profiles are used to study the Es layer occurrence as well as its intensity of the signal-to-noise ratio (SNR) of the 50 Hz GPS L1 signal. The methodology was applied to identify the Es layer on RO measurements over Cachoeira Paulista, a low-latitude station in the Brazilian region, in which the Es layer development is not driven tidal winds only as it is at middle latitudes. The coincident events were analyzed using the RO technique and ionosonde observations during the year 2014 to 2016. We used the electron density obtained using the blanketing frequency parameter (fbEs) and the Es layer height (h'Es) acquired from the ionograms to validate the satellite measurements. The comparative results show that the Es layer characteristics extracted from the RO measurements are in good agreement with the Es layer parameters from the digisonde. Keywords. Ionosphere (ionosphere–atmosphere interactions)

Global distribution of neutral wind shear associated with sporadic E layers derived from GAIA

2017 ◽  
Vol 122 (4) ◽  
pp. 4450-4465 ◽  
Author(s):  
H. Shinagawa ◽  
Y. Miyoshi ◽  
H. Jin ◽  
H. Fujiwara
Keyword(s):  
Wind Shear ◽  
Global Distribution ◽  
Neutral Wind ◽  
Sporadic E Layers ◽  
Sporadic E

scholarly journals Mid-latitude <i>E</i>-region bulk motions inferred from digital ionosonde and HF radar measurements

2004 ◽  
Vol 22 (11) ◽  
pp. 3789-3798 ◽  
Author(s):  
G. C. Hussey ◽  
C. Haldoupis ◽  
A. Bourdillon ◽  
J. Delloue ◽  
J. T. Wiensz
Keyword(s):  
Hf Radar ◽  
Neutral Wind ◽  
Angle Of Arrival ◽  
Neutral Winds ◽  
Sporadic E Layers ◽  
E Region ◽  
Radar Measurements ◽  
Sporadic E ◽  
Coherent Radar ◽  
Coherent Backscatter

Abstract. In the mid-latitude E-region there is now evidence suggesting that neutral winds play a significant role in driving the local plasma instabilities and electrodynamics inside sporadicE layers. Neutral winds can be inferred from coherent radar backscatter measurements of the range-/azimuth-time-intensity (RTI/ATI) striations of quasi-periodic (QP) echoes, or from radar interferometer/imaging observations. In addition, neutral winds in the E-region can be estimated from angle-of-arrival ionosonde measurements of sporadic-E layers. In the present paper we analyse concurrent ionosonde and HF coherent backscatter observations obtained when a Canadian Advanced Digital Ionosonde (CADI) was operated under a portion of the field-of-view of the Valensole high frequency (HF) radar. The Valensole radar, a mid-latitude radar located in the south of France with a large azimuthal scanning capability of 82° (24° E to 58° W), was used to deduce zonal bulk motions of QP echoing regions using ATI analysis. The CADI was used to measure angle-of-arrival information in two orthogonal horizontal directions and thus derive the motion of sporadic-E patches drifting with the neutral wind. This paper compares the neutral wind drifts of the unstable sporadic-E patches as determined by the two instruments. The CADI measurements show a predominantly westward aligned motion, but the measured zonal drifts are underestimated relative to those observed with the Valensole radar.

scholarly journals A Case Study of Polar Cap Sporadic-E Layer Associated with TEC Variations

2021 ◽  
Vol 13 (7) ◽  
pp. 1324
Author(s):  
Yong Wang ◽  
Periyadan T. Jayachandran ◽  
David R. Themens ◽  
Anthony M. McCaffrey ◽  
Qing-He Zhang ◽  
...  
Keyword(s):  
Electron Content ◽  
High Electron ◽  
Gps Receiver ◽  
Polar Cap ◽  
Total Electron ◽  
Multiple Measurements ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E

The Sporadic-E (Es) layer is an often-observed phenomenon at high latitudes; however, our understanding of the polar cap Es layer is severely limited due to the scarce number of measurements. Here, the first comprehensive study of the polar cap Es layer associated with Global Positioning System (GPS) Total Electron Content (TEC) variations and scintillations is presented with multiple measurements at Resolute, Canada (Canadian Advanced Digital Ionosonde (CADI), Northward-looking face of Resolute Incoherent-Scatter Radar (RISR-N), and GPS receiver). According to the joint observations, the polar cap Es layer is a thin patch structure with variously high electron density, which gradually develops into the lower E region (~100 km) and horizontally extends >200 km. Moreover, the TEC variations produced by the polar cap Es layer are pulse-like enhancements with a general amplitude of ~0.5 TECu and are followed by smaller but rapid TEC perturbations. Furthermore, the possible scintillation effects likely associated with the polar cap Es layer are also discussed. As a consequence, the results widely expand our understanding on the polar cap Es layer, in particular on TEC variations.

scholarly journals Quarterdiurnal signature in sporadic E occurrence rates and comparison with neutral wind shear

2019 ◽  
Vol 37 (3) ◽  
pp. 273-288 ◽  
Author(s):  
Christoph Jacobi ◽  
Christina Arras ◽  
Christoph Geißler ◽  
Friederike Lilienthal
Keyword(s):  
Zonal Wind ◽  
Wind Shear ◽  
Lower Thermosphere ◽  
Vertical Wind Shear ◽  
Global Scale ◽  
Vertical Shear ◽  
Maximum Deviation ◽  
Driving Mechanism ◽  
Sporadic E ◽  
Wind Shears

Abstract. The GPS radio occultation (RO) technique is used to study sporadic E (Es) layer plasma irregularities of the Earth's ionosphere on a global scale using GPS signal-to-noise ratio (SNR) profiles from the COSMIC/FORMOSAT-3 satellite. The maximum deviation from the mean SNR can be attributed to the height of the Es layer. Es are generally accepted to be produced by ion convergence due to vertical wind shear in the presence of a horizontal component of the Earth's magnetic field, while the wind shear is provided mainly by the solar tides. Here we present analyses of quarterdiurnal tide (QDT) signatures in Es occurrence rates. From a local comparison with mesosphere/lower thermosphere wind shear obtained with a meteor radar at Collm (51.3∘ N, 13.0∘ E), we find that the phases of the QDT in Es agree well with those of negative vertical shear of the zonal wind for all seasons except for summer, when the QDT amplitudes are small. We also compare the global QDT Es signal with numerical model results. The global distribution of the Es occurrence rates qualitatively agrees with the modeled zonal wind shears. The results indicate that zonal wind shear is indeed an important driving mechanism for the QDT seen in Es.

scholarly journals Electric field measurements of DC and long wavelength structures associated with sporadic-<i>E</i> layers and QP radar echoes

2005 ◽  
Vol 23 (7) ◽  
pp. 2319-2334 ◽  
Author(s):  
R. Pfaff ◽  
H. Freudenreich ◽  
T. Yokoyama ◽  
M. Yamamoto ◽  
S. Fukao ◽  
...  
Keyword(s):  
Electric Field ◽  
Electric Fields ◽  
Plasma Density ◽  
Sounding Rocket ◽  
Neutral Wind ◽  
Short Scale ◽  
Radar Echoes ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E

Abstract. Electric field and plasma density data gathered on a sounding rocket launched from Uchinoura Space Center, Japan, reveal a complex electrodynamics associated with sporadic-E layers and simultaneous observations of quasi-periodic radar echoes. The electrodynamics are characterized by spatial and temporal variations that differed considerably between the rocket's upleg and downleg traversals of the lower ionosphere. Within the main sporadic-E layer (95–110 km) on the upleg, the electric fields were variable, with amplitudes of 2–4 mV/m that changed considerably within altitude intervals of 1–3 km. The identification of polarization electric fields coinciding with plasma density enhancements and/or depletions is not readily apparent. Within this region on the downleg, however, the direction of the electric field revealed a marked change that coincided precisely with the peak of a single, narrow sporadic-E plasma density layer near 102.5 km. This shear was presumably associated with the neutral wind shear responsible for the layer formation. The electric field data above the sporadic-E layer on the upleg, from 110 km to the rocket apogee of 152 km, revealed a continuous train of distinct, large scale, quasi-periodic structures with wavelengths of 10–15 km and wavevectors oriented between the NE-SW quadrants. The electric field structures had typical amplitudes of 3–5 mV/m with one excursion to 9 mV/m, and in a very general sense, were associated with perturbations in the plasma density. The electric field waveforms showed evidence for steepening and/or convergence effects and presumably had mapped upwards along the magnetic field from the sporadic-E region below. Candidate mechanisms to explain the origin of these structures include the Kelvin-Helmholtz instability and the Es-layer instability. In both cases, the same shear that formed the sporadic-E layer would provide the energy to generate the km-scale structures. Other possibilities include gravity waves or a combination of these processes. The data suggest that these structures were associated with the lower altitude density striations that were the seat of the QP radar echoes observed simultaneously. They also appear to have been associated with the mechanism responsible for a well-defined pattern of "whorls" in the neutral wind data that were revealed in a chemical trail released by a second sounding rocket launched 15min later. Short scale (<100 m) electric field irregularities were also observed and were strongest in the sporadic-E region below 110km. The irregularities were organized into 2–3 layers on the upleg, where the plasma density also displayed multiple layers, yet were confined to a single layer on the downleg where the plasma density showed a single, well-defined sporadic-E peak. The linear gradient drift instability involving the DC electric field and the vertical plasma gradient is shown to be incapable of driving the observed waves on the upleg, but may have contributed to the growth of short scale waves on the topside of the narrow unstable density gradient observed on the downleg. The data suggest that other sources of free energy may have been important factors for the growth of the short scale irregularities. Keywords. Ionosphere (Mid-latitude ionosphere; Electric fields and currents; Ionospheric irregularities)

scholarly journals Sporadic E morphology based on COSMIC radio occultation data and its relationship with wind shear theory

2021 ◽  
Vol 73 (1) ◽  
Author(s):  
Jia Luo ◽  
Haifeng Liu ◽  
Xiaohua Xu
Keyword(s):  
Magnetic Field ◽  
Wind Shear ◽  
Radio Occultation ◽  
Field Model ◽  
Global Distribution ◽  
Cosmic Radio ◽  
Neutral Wind ◽  
Earth’S Magnetic Field ◽  
Low Altitude ◽  
Sporadic E

AbstractThe S4max data retrieved from the Constellation Observing System for the Meteorology, Ionosphere, and Climate (COSMIC) radio occultation (RO) measurements during 2007 to 2015 is adopted to investigate the global distribution and seasonal variation of the sporadic E (Es) layers in the present work. The long-term and short-term global Es occurrence maps are presented and the spatial and temporal distributions of Es occurrence rates (ORs) are further confirmed and studied. The International Geomagnetic Reference Field model (IGRF12) is used to calculate the horizontal intensity and inclination of the Earth’s magnetic field. The analysis shows that the Earth’s magnetic field is one of the fundamental reasons for the global distribution of the Es layers. In addition, the Horizontal Wind Field model HWM14 and the IGRF12 model were employed to calculate the vertical ion convergence (VIC) to examine the role of neutral wind shear in the global distribution of the Es ORs. The results reveal that the middle latitude distribution of simulated vertical concentration of Fe+ is similar to that of Es ORs, which indicates that the VIC induced by the neutral wind shear is an important factor in determining the geographical distribution, summer maximum (or winter minimum) and diurnal characteristics of Es ORs in middle latitudes. The new findings mainly include the following two aspects: (1) in summer over mid-latitudes, VIC peaks in the morning and afternoon to evening, which explains the semidiurnal behavior of Es ORs; (2) VIC reaches its minimum value in low-altitude (100 km) areas, which is the reason for the significant decrease in Es ORs in low-altitude areas. The disagreements between the VIC and Es ORs indicate that other processes, such as the meteor influx rate, the ionospheric electric fields and atmospheric tides, should also be considered as they may have an important impact on the variation of Es layers. Graphical Abstract

scholarly journals Equatorial E Region Electric Fields and Sporadic E Layer Responses to the Recovery Phase of the November 2004 Geomagnetic Storm

2017 ◽  
Vol 122 (12) ◽  
pp. 12,517-12,533 ◽  
Author(s):  
J. Moro ◽  
L. C. A. Resende ◽  
C. M. Denardini ◽  
J. Xu ◽  
I. S. Batista ◽  
...  
Keyword(s):  
Geomagnetic Storm ◽  
Electric Fields ◽  
Recovery Phase ◽  
E Region ◽  
Sporadic E Layer ◽  
Sporadic E
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