Growth of plasma waves of scales longer than 10 km by gradient-drift instability in the E-region of equatorial ionosphere

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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Non-magnetic aspect sensitive auroral echoes from the lower E region observed at 50 MHz

Annales Geophysicae ◽

10.1007/s00585-999-1284-x ◽

1999 ◽

Vol 17 (10) ◽

pp. 1284-1292 ◽

Cited By ~ 4

Author(s):

R. Rüster ◽

K. Schlegel

Keyword(s):

Magnetic Field ◽

Electric Fields ◽

Middle Atmosphere ◽

Magnetic Field Direction ◽

Ionosphere Plasma ◽

E Region ◽

Strong Electric Fields ◽

Gradient Drift ◽

Drift Instability ◽

The Magnetic Field

Abstract. Backscatter from E-region irregularities was observed at aspect angles close to 90° (almost parallel to the direction of the magnetic field) using the ALOMAR SOUSY radar at Andoya/Norway. Strong electric fields and increased E-region electron temperatures simultaneously measured with the incoherent scatter facility EISCAT proved that the Farley-Buneman plasma instability was excited. In addition, strong particle precipitation was present as inferred from EISCAT electron densities indicating that the gradient drift instability may have been active, too. Backscatter at such large aspect angles was not expected and has not been observed before. The characteristics of the observed echoes, however, are in many aspects completely different from usual auroral radar results: the Doppler velocities are only of the order of 10 m/s, the half-width of the spectra is around 5 m/s, the echoes originate at altitudes well below 100 km, and they seem to be not aspect-sensitive with respect to the magnetic field direction. We, therefore, conclude that the corresponding irregularities are not caused by the mentioned instabilities and that other mechanism have to be invoked.Key words. Ionosphere (plasma waves and instabilities; ionosphere irregularities; particle precipitaion) · Meteorology and atmospheric dynamics (middle atmosphere dynamics)

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Neutral wind-driven gradient drift instability in the low-latitude daytime E region

Journal of Geophysical Research Atmospheres ◽

10.1029/2010ja016166 ◽

2011 ◽

Vol 116 (A3) ◽

Cited By ~ 4

Author(s):

Zhijin Li ◽

Libo Liu ◽

Weixing Wan ◽

Baiqi Ning

Keyword(s):

Neutral Wind ◽

Low Latitude ◽

E Region ◽

Gradient Drift ◽

Drift Instability

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A nonlocal theory of the gradient-drift instability in the ionospheric E-region plasma at mid-latitudes

Journal of Atmospheric and Solar-Terrestrial Physics ◽

10.1016/j.jastp.2004.07.011 ◽

2004 ◽

Vol 66 (17) ◽

pp. 1627-1637 ◽

Cited By ~ 12

Author(s):

Charles E. Seyler ◽

José M. Rosado-Román ◽

Donald T. Farley

Keyword(s):

Nonlocal Theory ◽

E Region ◽

Gradient Drift ◽

Drift Instability ◽

Region Plasma

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Bottom-type scattering layers and equatorial spread <i>F</i>

Annales Geophysicae ◽

10.5194/angeo-22-4061-2004 ◽

2004 ◽

Vol 22 (12) ◽

pp. 4061-4069 ◽

Cited By ~ 30

Author(s):

D. L. Hysell ◽

J. Chun ◽

J. L. Chau

Keyword(s):

Large Scale ◽

Coherent Scattering ◽

Plasma Waves ◽

Equatorial Ionosphere ◽

Bottom Type ◽

Radar Images ◽

F Region ◽

Type Layer ◽

Spread F ◽

Gradient Drift

Abstract. Jicamarca radar observations of bottom-type coherent scattering layers in the post-sunset bottomside F-region ionosphere are presented and analyzed. The morphology of the primary waves seen in radar images of the layers supports the hypothesis of kudeki+bhattacharyya-1999 that wind-driven gradient drift instabilities are operating. In one layer event when topside spread F did not occur, irregularities were distributed uniformly in space throughout the layers. In another event when topside spread F did eventually occur, the irregularities within the pre-existing bottom-type layers were horizontally clustered, with clusters separated by about 30km. The same horizontal periodicity was evident in the radar plumes and large-scale irregularities that emerged later in the event. We surmise that horizontal periodicity in bottom-type layer irregularity distribution is indicative of large-scale horizontal waves in the bottomside F-region that may serve as seed waves for large-scale Rayleigh Taylor instabilities. Key words. Ionosphere (equatorial ionosphere; ionospheric irregularties; plasma waves and instabilities)

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Auroral <i>E</i>-region electron density gradients measured

Annales Geophysicae ◽

10.1007/s00585-000-1172-x ◽

2000 ◽

Vol 18 (9) ◽

pp. 1172-1181 ◽

Cited By ~ 11

Author(s):

C. Haldoupis ◽

K. Schlegel ◽

G. Hussey

Keyword(s):

Electric Field ◽

Density Gradient ◽

Electron Density ◽

Electric Fields ◽

Plasma Waves ◽

Density Gradients ◽

Electron Density Gradient ◽

E Region ◽

Gradient Drift ◽

Region Plasma

Abstract. In the theory of E-region plasma instabilities, the ambient electric field and electron density gradient are both included in the same dispersion relation as the key parameters that provide the energy for the generation and growth of electrostatic plasma waves. While there exist numerous measurements of ionospheric electric fields, there are very few measurements and limited knowledge about the ambient electron density gradients, ∇Ne, in the E-region plasma. In this work, we took advantage of the EISCAT CP1 data base and studied statistically the vertical electron density gradient length, Lz=Ne/(dNe/dz), at auroral E-region heights during both eastward and westward electrojet conditions and different ambient electric field levels. Overall, the prevailing electron density gradients, with Lz ranging from 4 to 7 km, are found to be located below 100 km, but to move steadily up in altitude as the electric field level increases. The steepest density gradients, with Lz possibly less than 3 km, occur near 110 km mostly in the eastward electrojet during times of strong electric fields. The results and their implications are examined and discussed in the frame of the linear gradient drift instability theory. Finally, it would be interesting to test the implications of the present results with a vertical radar interferometer.Key words: Ionosphere (auroral ionosphere; ionospheric irregularities; plasma waves and instabilities)

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Investigation of the gradient drift instability as a cause of density irregularities in subauroral polarization streams

Journal of Geophysical Research Space Physics ◽

10.1029/2020ja029027 ◽

2021 ◽

Author(s):

C. Rathod ◽

B. Srinivasan ◽

W. Scales ◽

B. Kunduri

Keyword(s):

Gradient Drift ◽

Drift Instability

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Effects of solar eclipse on the electrodynamical processes of the equatorial ionosphere: a case study during 11 August 1999 dusk time total solar eclipse over India

Annales Geophysicae ◽

10.5194/angeo-20-1977-2002 ◽

2002 ◽

Vol 20 (12) ◽

pp. 1977-1985 ◽

Cited By ~ 26

Author(s):

R. Sridharan ◽

C. V. Devasia ◽

N. Jyoti ◽

Diwakar Tiwari ◽

K. S. Viswanathan ◽

...

Keyword(s):

Electric Fields ◽

Solar Eclipse ◽

Equatorial Ionosphere ◽

Hf Radar ◽

F Region ◽

Large Enhancement ◽

Temporal Structures ◽

E Region ◽

Field Lines ◽

Electric Fields And Currents

Abstract. The effects on the electrodynamics of the equatorial E- and F-regions of the ionosphere, due to the occurrence of the solar eclipse during sunset hours on 11 August 1999, were investigated in a unique observational campaign involving ground based ionosondes, VHF and HF radars from the equatorial location of Trivandrum (8.5° N; 77° E; dip lat. 0.5° N), India. The study revealed the nature of changes brought about by the eclipse in the evening time E- and F-regions in terms of (i) the sudden intensification of a weak blanketing ES-layer and the associated large enhancement of the VHF backscattered returns, (ii) significant increase in h' F immediately following the eclipse and (iii) distinctly different spatial and temporal structures in the spread-F irregularity drift velocities as observed by the HF radar. The significantly large enhancement of the backscattered returns from the E-region coincident with the onset of the eclipse is attributed to the generation of steep electron density gradients associated with the blanketing ES , possibly triggered by the eclipse phenomena. The increase in F-region base height immediately after the eclipse is explained as due to the reduction in the conductivity of the conjugate E-region in the path of totality connected to the F-region over the equator along the magnetic field lines, and this, with the peculiar local and regional conditions, seems to have reduced the E-region loading of the F-region dynamo, resulting in a larger post sunset F-region height (h' F) rise. These aspects of E-and F-region behaviour on the eclipse day are discussed in relation to those observed on the control day.Key words. Ionosphere (electric fields and currents; equatorial ionosphere; ionospheric irregularities)

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