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

2005 ◽  
Vol 23 (3) ◽  
pp. 773-779 ◽  
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.

scholarly journals First simultaneous lidar observations of sodium layers and VHF radar observations of E-region field-aligned irregularities at the low-latitude station Gadanki

2009 ◽  
Vol 27 (9) ◽  
pp. 3411-3419 ◽  
Author(s):  
S. Sridharan ◽  
A. K. Patra ◽  
N. Venkateswara Rao ◽  
G. Ramkumar
Keyword(s):  
Lower Thermosphere ◽  
Low Latitude ◽  
Vhf Radar ◽  
Neutral Winds ◽  
Zonal Winds ◽  
Tidal Phase ◽  
E Region ◽  
The Relationship ◽  
Lidar Observations ◽  
Field Aligned Irregularities

Abstract. Simultaneous observations of atmospheric sodium (Na) made by a resonance lidar and E-region field-aligned-irregularities (FAI) made by the Indian MST radar, both located at Gadanki (13.5° N, 79.2° E) and horizontal winds acquired by a SKiYMET meteor radar at Trivandrum (8.5° N, 77° E) are used to investigate the relationship among sodium layer, FAI and neutral winds in the mesosphere and lower thermosphere region. The altitudes and descent rates of higher altitude (~95 km) Na layer and FAI agree quite well. The descending structures of the higher altitude Na layer and FAI are found to be closely related to the diurnal tidal phase structure in zonal winds observed over Trivandrum. At lower altitudes, the descent rate of FAI is larger than that of Na layer and zonal tidal phase. These observations support the hypothesis that the metallic ion layers are formed by the zonal wind shear associated with tidal winds and subsequently get neutralized to manifest in the form of descending Na layers. The descending FAI echoing layers are manifestation of the instabilities setting in on the ionization layer. In the present observations, the altitudes of occurrence of Na layer and FAI echoes being low, we surmise that it is quite possible that the FAI echoes are due to the descent of already formed irregularities at higher altitudes.

scholarly journals E-Region Field-Aligned Irregularities in the Middle of a Solar Eclipse Observed by a Bistatic Radar

2022 ◽  
Vol 14 (2) ◽  
pp. 392
Author(s):  
Lei Qiao ◽  
Gang Chen ◽  
Wanlin Gong ◽  
Xuesi Cai ◽  
Erxiao Liu ◽  
...  
Keyword(s):  
Solar Eclipse ◽  
Recovery Phase ◽  
Bistatic Radar ◽  
Doppler Shifts ◽  
Propagation Parameters ◽  
E Region ◽  
Gradient Drift ◽  
Drift Instability ◽  
Wave Induced ◽  
Field Aligned Irregularities

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.

scholarly journals Morphological study of the field-aligned E-layer irregularities observed by the Gadanki VHF radar

2004 ◽  
Vol 22 (11) ◽  
pp. 3799-3804 ◽  
Author(s):  
C. J. Pan ◽  
P. B. Rao
Keyword(s):  
Geomagnetic Latitude ◽  
Spectral Width ◽  
Statistical Characteristics ◽  
Low Latitude ◽  
Vhf Radar ◽  
Lower Altitude ◽  
Radar Echoes ◽  
E Region ◽  
Sporadic E ◽  
Total Observation

Abstract. We report on the field-aligned irregularities observed in the low-latitude sporadic E-layer (Es) with the Gadanki (13.5° N, 79.2° E; geomagnetic latitude 6.3° N) VHF radar. The radar was operated intermittently for 15 days during the summer months in 1998 and 1999, for both daytime and nighttime observation. The total observation periods are 161h for the nighttime and 68h for the daytime. The observations were used to study the percentage of occurrence of the E-region echoes for both daytime and nighttime. The statistical characteristics of the mean radial velocity and spectral width are presented for three cases based on the echo occurrence characteristics and the altitude of observations (from 90 to 140km ranges), namely, the lower E-region daytime (90-110km), the lower E-region nighttime (90-105km) and the upper E-region nighttime (105-140km) echoes. The results are compared with that of Piura, a low-latitude station located at about the same geomagnetic latitude, but to the south of the equator. By comparing the behaviors of the lower E-region radar echoes of the summer months between Gadanki and Piura, we find that the lower altitude echoes below about 100km are rarely reported in Piura but commonly seen in Gadanki. Features of the nighttime echoes observed by these two radars are quite similar but daytime FAI echoes are again seldom detected by Piura.

scholarly journals Low-latitude field-aligned irregularities observed in theEregion with the Piura VHF radar: First results

Radio Science ◽  
1999 ◽  
Vol 34 (4) ◽  
pp. 983-990 ◽  
Author(s):  
Ronald F. Woodman ◽  
Jorge L. Chau ◽  
Fredy Aquino ◽  
Rodolfo R. Rodriguez ◽  
Luis A. Flores
Keyword(s):  
Low Latitude ◽  
Vhf Radar ◽  
First Results ◽  
Field Aligned Irregularities

scholarly journals Investigation of the relationship between optical auroral forms and HF radar E region backscatter

2000 ◽  
Vol 18 (6) ◽  
pp. 608-617 ◽  
Author(s):  
S. E. Milan ◽  
M. Lester ◽  
N. Sato ◽  
H. Takizawa ◽  
J.-P. Villain
Keyword(s):  
Spectral Characteristics ◽  
Hf Radar ◽  
Vhf Radar ◽  
The Past ◽  
Optical Signature ◽  
E Region ◽  
Coherent Backscatter ◽  
First Time ◽  
The Relationship ◽  
East West

Abstract. The SuperDARN HF radars have been employed in the past to investigate the spectral characteristics of coherent backscatter from L-shell aligned features in the auroral E region. The present study employs all-sky camera observations of the aurora from Husafell, Iceland, and the two SuperDARN radars located on Iceland, Þykkvibær and Stokkseyri, to determine the optical signature of such backscatter features. It is shown that, especially during quiet geomagnetic conditions, the backscatter region is closely associated with east-west aligned diffuse auroral features, and that the two move in tandem with each other. This association between optical and radar aurora has repercussions for the instability mechanisms responsible for generating the E region irregularities from which radars scatter. This is discussed and compared with previous studies investigating the relationship between optical and VHF radar aurora. In addition, although it is known that E region backscatter is commonly observed by SuperDARN radars, the present study demonstrates for the first time that multiple radars can observe the same feature to extend over at least 3 h of magnetic local time, allowing precipitation features to be mapped over large portions of the auroral zone.Key words: Ionosphere (particle precipitation; plasma waves and instabilities)

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