Estimation of beam broadening spectrum of radar returns from field-aligned irregularities in ionospheric sporadic E region

The Wuhan Ionospheric Oblique Backscatter Sounding System (WIOBSS) was applied as a bistatic radar to record the ionospheric E-region responses to a solar eclipse on 22 July 2009. The transmitter was located in Wuhan and the receiver was located in Huaian. The receiver observed anomalous echoes with larger Doppler shifts at the farther ranges compared with the echoes reflected by Es. According to the simulated ray propagation paths of the reflected and scattered waves, we considered that the anomalous echoes were scattered by E-region field-aligned irregularities (FAIs). The locations of the FAIs recorded by the WIOBSS were estimated with the International Geomagnetic Reference Field (IGRF) and the observed propagation parameters. These irregularities occurred at around the eclipse maximum and lasted for ~20–40 min. The steep plasma density gradient induced by the fast drop photo ionization under the lunar shadow was beneficial to the occurrence of gradient drift instability to generate the FAIs. They were different from the gravity wave-induced irregularities occurring in the recovery phase of the solar eclipse.

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Energetics and structure of the lower E region associated with sporadic E layer

Annales Geophysicae ◽

10.5194/angeo-26-2929-2008 ◽

2008 ◽

Vol 26 (9) ◽

pp. 2929-2936 ◽

Cited By ~ 1

Author(s):

K.-I. Oyama ◽

K. Hibino ◽

T. Abe ◽

R. Pfaff ◽

T. Yokoyama ◽

...

Keyword(s):

Electric Field ◽

Field Data ◽

Magnetic Line ◽

Height Range ◽

Sounding Rockets ◽

Main Structure ◽

Irregular Structures ◽

E Region ◽

Sporadic E Layer ◽

Sporadic E

Abstract. The electron temperature (Te), electron density (Ne), and two components of the electric field were measured from the height of 90 km to 150 km by one of the sounding rockets launched during the SEEK-2 campaign. The rocket went through sporadic E layer (Es) at the height of 102 km–109 km during ascent and 99 km–108 km during decent, respectively. The energy density of thermal electrons calculated from Ne and Te shows the broad maximum in the height range of 100–110 km, and it decreases towards the lower and higher altitudes, which implies that a heat source exists in the height region of 100 km–110 km. A 3-D picture of Es, that was drawn by using Te, Ne, and the electric field data, corresponded to the computer simulation; the main structure of Es is projected to a higher altitude along the magnetic line of force, thus producing irregular structures of Te, Ne and electric field in higher altitude.

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Investigation on the role of E-F region coupling processes on the generation of nighttime MSTIDs: Case studies over northern Germany

10.5194/egusphere-egu21-12929 ◽

2021 ◽

Author(s):

Mani Sivakandan ◽

Jorge L Chau ◽

Carlos Martinis ◽

Yuichi Otsuka ◽

Jens Mielich ◽

...

Keyword(s):

Gps Tec ◽

F Region ◽

Perkins Instability ◽

Sporadic E Layers ◽

Spread F ◽

E Region ◽

Sporadic E ◽

Low Latitude Ionosphere ◽

Atmospheric Gravity

Northwest to southeast phase fronts with southwestward moving features are commonly observed in the nighttime midlatitude ionosphere during the solstice months at low solar activity. These features are identified as nighttime MSTIDs (medium scale traveling ionospheric disturbances). Initially, they were considered to be a manifestation of neutral atmospheric gravity waves. Later on, investigations showed that the nighttime MSTIDs are electrified in nature and mostly confined to the mid and low latitude ionosphere. Although the overall characteristics of the nighttime MSTIDs are mostly well understood, the causative mechanisms are not well known. Perkins instability mechanism was believed to be the cause of nighttime MSTIDs, however, the growth rate of the instability is too small to explain the perturbations observed. Recently, model simulations and observational studies suggest that coupling between sporadic-E layers and other type of E-region instabilities, and the F region may be relevant to explain the generation of the MSTIDs.In the present study simultaneous observation from OI 630 nm all-sky airglow imager, GPS-TEC, ionosonde and Meteor radars, are used to investigate the role of E and F region coupling on the generation of MSTIDs .Nighttime MSTIDs observed on three nights (14 March 2020, 23 March 2020 and 28 May 2020) in the OI 630 nm airglow images over Kuehlungsborn (54&#176;07'N; 11&#176;46'E, 53.79N&#160; mag latitude), Germany, are presented. Simultaneous detrended GPS-TEC measurements also shows presence of MSTIDs on these nights. In addition, simultaneous ionosonde observations over Juliusruh (54&#176;37.7'N 13&#176;22.5'E) show spread-F in the ionograms as well as sporadic-E layer occurrence.&#160; Furthermore, we also investigate the MLT region wind variations during these nights. The role of Es-layers and the interplay between the winds and Es-layers role on the generation of the MSTIDs will be discussed in detail in this presentation.&#160;

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Simultaneous VHF radar backscatter and ionosonde observations of low-latitude E region

Annales Geophysicae ◽

10.5194/angeo-23-773-2005 ◽

2005 ◽

Vol 23 (3) ◽

pp. 773-779 ◽

Cited By ~ 8

Author(s):

A. K. Patra ◽

S. Sripathi ◽

P. B. Rao ◽

K. S. V. Subbarao

Keyword(s):

Low Latitude ◽

Vhf Radar ◽

Radar Echoes ◽

First Results ◽

E Region ◽

Gradient Drift ◽

Drift Instability ◽

Relationship Of ◽

The Relationship ◽

Field Aligned Irregularities

Abstract. The first results of simultaneous observations made on the low-latitude field-aligned irregularities (FAI) using the MST radar located at Gadanki (13.5° N, 79.2° E, dip 12.5°) and the Es parameters using an ionosonde at a nearby station Sriharikota (13.7° N, 80.1° E, dip 12.6°) are presented. The observations show that while the height of the most intense radar echoes is below the virtual height of Es (h'Es) during daytime, it is found to be either below or above during nighttime. The strength of the FAI is better correlated with the top penetration frequency (ftEs) and the blanketing frequency (fbEs) during the night (r=0.4 in both cases) as compared to the day (r=0.35 and -0.04, respectively). Furthermore, the signal strength of FAI is reasonably correlated with (ftEs-fbEs) during daytime (r=0.59) while very poorly correlated during nighttime (r=0.18). While the radar observations in general appear to have characteristics close to that of mid-latitudes, the relationship of these with the Es parameters are poorer than that of mid-latitudes. The observations reported here, nevertheless, are quite consistent with the expectations based on the gradient drift instability mechanism.

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