Evidence of intermediate layer characteristics in the Gadanki radar observations of the upper E region 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.

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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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Extension of MF radar tidal measurements to E-region heights (95-125 km): Saskatoon (52°N, 107°W), Canada

Annales Geophysicae ◽

10.1007/s00585-994-0333-8 ◽

1994 ◽

Vol 12 (4) ◽

pp. 333-341

Author(s):

S. P. Namboothiri ◽

A. H. Manson ◽

C. E. Meek

Keyword(s):

Radar Observations ◽

Tidal Propagation ◽

Radar Echoes ◽

Tidal Data ◽

E Region ◽

Future Work ◽

Mf Radar

Abstract. Efforts have been made to extend the MF radar tidal profiles to E-region heights. The totally reflected MF radar echoes from E-region heights during daytime are known to be group-retarded and the corresponding wind and tidal data will have associated height discrepancies. The estimation of the E-region real heights (Namboothiri et al., 1993), and the elimination of the data for which the group retardation is significant, are selected as the basic criteria to extend the tidal profiles to 100-125 km. The analysis of the quiet (Ap<19) days of the winter and summer seasons of 1988/89 shows that the tidal propagation continues to higher altitudes with some changes in their pattern, e.g. longer wavelengths, compared to that in the lower altitudes. Comparison with the model profiles shows some resemblance and some disagreements. The reliability of the MF radar tidal measurements of E-region heights and the propagation of tides in this region have been discussed in the light of existing theories and other experimental observations. It is concluded that, based on the initial studies with UHF and MF systems and within the limits of the available theories, the information on tides presented here for the 100-125 km region using the MF radar observations is useful. Suggestions for future work in this direction are also given.

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MU Radar observations of kilometer-scale waves in the midlatitude lower E-region

Geophysical Research Letters ◽

10.1029/2000gl003820 ◽

2000 ◽

Vol 27 (22) ◽

pp. 3667-3670 ◽

Cited By ~ 9

Author(s):

P. B. Rao ◽

M. Yamamoto ◽

A. Uchida ◽

I. Hassenpflug ◽

S. Fukao

Keyword(s):

Radar Observations ◽

Mu Radar ◽

E Region

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Evidence of kilometer-scale waves in the lower E region from high resolution VHF radar observations over Gadanki

Geophysical Research Letters ◽

10.1029/2001gl013340 ◽

2002 ◽

Vol 29 (10) ◽

pp. 137-1-137-4 ◽

Cited By ~ 16

Author(s):

A. K. Patra ◽

S. Sripathi ◽

V. Siva Kumar ◽

P. B. Rao

Keyword(s):

High Resolution ◽

Vhf Radar ◽

Radar Observations ◽

E Region

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Seasonal variation of low-latitude E-region plasma irregularities studied using Gadanki radar and ionosonde

Annales Geophysicae ◽

10.5194/angeo-26-1865-2008 ◽

2008 ◽

Vol 26 (7) ◽

pp. 1865-1876 ◽

Cited By ~ 7

Author(s):

D. V. Phanikumar ◽

A. K. Patra ◽

C. V. Devasia ◽

G. Yellaiah

Keyword(s):

Seasonal Variation ◽

Seasonal Variations ◽

Low Latitude ◽

Plasma Irregularities ◽

Daytime Activity ◽

Significant Difference ◽

E Region ◽

Region Plasma ◽

Present Understanding ◽

Field Aligned Irregularities

Abstract. In this paper, we present seasonal variation of E region field-aligned irregularities (FAIs) observed using the Gadanki radar and compare them with the seasonal variation of Es observed from a nearby location SHAR. During daytime, FAIs occur maximum in summer and throughout the day, as compared to other seasons. During nighttime, FAIs occur equally in both summer and winter, and relatively less in equinoxes. Seasonal variations of Es (i.e. ftEs and fbEs) show that the daytime activity is maximum in summer and the nighttime activity is maximum in equinoxes. No relation is found between FAIs occurrence/SNR and ftEs/fbEs. FAIs occurrence, however, is found to be related well with (ftEs−fbEs). This aspect is discussed in the light of the present understanding of the mid-latitude Es-FAIs relationship. The seasonal variations of FAIs observed at Gadanki are compared in detail with those of Piura, which show a significant difference in the daytime observations. The observed difference has been discussed considering the factors governing the generation of FAIs.

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