On the vector plasma drift measurements over Equatorial Ionosphere using HF Doppler radar – A brief review

Abstract. Measurements with a HF Doppler sounder at Kodaikanal (10.2°N, 77.5°E, geomagnetic latitude 0.8°N) showed conspicuous quasi-periodic fluctuations (period 25-35 min) in F region vertical plasma drift, Vz in the interval 0047-0210 IST on the night of 23/24 December, 1991 (Ap = 14, Kp < 4-). The fluctuations in F region vertical drift are found to be coherent with variations in Bz (north-south) component of interplanetary magnetic field (IMF), in geomagnetic H/X components at high-mid latitude locations both in the sunlit and dark hemispheres and near the dayside dip equator, suggestive of DP2 origin. But the polarity of the electric field fluctuations at the midnight dip equator (eastward) is the same as the dayside equator inferred from magnetic variations, contrary to what is expected of equatorial DP2. The origin of the coherent occurrence of equatorial electric field fluctuations in the DP2 range of the same sign in the day and night hemispheres is unclear and merits further investigations.Key words: Ionosphere (electric fields and currents; equatorial ionosphere; ionosphere-magnetosphere interactions)

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Electrodynamics of the equatorial F-region ionosphere during pre-sunrise period

Annales Geophysicae ◽

10.5194/angeo-27-107-2009 ◽

2009 ◽

Vol 27 (1) ◽

pp. 107-111 ◽

Cited By ~ 15

Author(s):

S. R. Prabhakaran Nayar ◽

T. J. Mathew ◽

C. V. Sreehari ◽

S. G. Sumod ◽

C. V. Devasia ◽

...

Keyword(s):

Electric Field ◽

Doppler Radar ◽

Striking Feature ◽

Plasma Drift ◽

F Region ◽

Vertical Drift

Abstract. The electrodynamics of the pre-sunrise equatorial F-region is investigated using HF Doppler radar and digital ionosonde. The observations are limited to those days for which the radar probing frequency is below the foF2 value. The ionosphere observation using HF Doppler radar exhibit interesting features during pre-sunrise period similar to the post sunset pre-reversal enhancement. The most striking feature observed during pre-sunrise period is the sudden downward excursion in the vertical drift around local sunrise followed by an upward turning. Pre-sunrise observations of vertical plasma drift and the sunrise downward excursion followed by an upward turning after the ground sunrise related to the zonal electric field at the equatorial F-region are the most significant results not reported earlier.

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Observations of GPS ionospheric scintillations over Wuhan during geomagnetic storms

Annales Geophysicae ◽

10.5194/angeo-24-1581-2006 ◽

2006 ◽

Vol 24 (6) ◽

pp. 1581-1590 ◽

Cited By ~ 14

Author(s):

G. Li ◽

B. Ning ◽

W. Wan ◽

B. Zhao

Keyword(s):

Geomagnetic Storms ◽

Equatorial Ionosphere ◽

The Other ◽

Small Scale ◽

Plasma Drift ◽

Equatorial Ionization Anomaly ◽

Spread F ◽

Ionospheric Scintillations ◽

Sporadic E Layer ◽

Sporadic E

Abstract. During the two geomagnetic storms which occurred on 1 October 2002 and 22 January 2004, the strong ionospheric scintillations of the GPS L1 band were observed at Wuhan station (30.6° N, 114.4° E, 45.8° Dip), which is situated near the northern crest of the equatorial ionosphere anomaly. We found that the intense scintillations were associated with the main phases of the storms and were co-located with the enhancement of the equatorial ionization anomaly (EIA); the co-existence of large- and small-scale irregularities at post-midnight was also found. The results may be relevant regarding the influence of the equatorial ionospheric eastward electric field during geomagnetic storms. On the other hand, GPS L1 band scintillations were not observed during the other two similar storms on 16 July 2003 and 20 November 2003. One of the reasons is probably that the sporadic E layer observed at the storms inhibited the generation of spread F by changing the Pedersen conductivity and suppressing the upward plasma drift.

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