Comparison of ionosonde and incoherent scatter drift measurements at the magnetic equator

Woodman, R. F.; Chau, Jorge L.; Ilma, R. R.

doi:10.1029/2005gl023692

Cited by 35 publications

(44 citation statements)

References 13 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is clear that the "Doppler" velocity is way off and unphysical -the velocity is not even the correct direction. The results are consistent with those presented by Woodman et al (2006) which show a positive drift during this time period, peaking between 02:00-04:00 LT. The crosses are the velocity estimates using Eq.…”

Section: Extracting Velocities From Density Measurementssupporting

confidence: 82%

“…During times of high convection (e.g., near the pre-reversal enhancement) recombination is negligible and the equation reduces to the motion of a constant density contour, as discussed by Woodman et al (2006). Using Eq.…”

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

“…The digisonde drifts are deduced from the line-of-sight Doppler velocity, and such measurements have been relatively successful at high latitudes (e.g., Scali et al, 1995). Woodman et al (2006) show that the agreement is worst in the postmidnight period, and attribute this disagreement to the relative importance of recombination. There have been other studies on the role of recombination at the equator (e.g., Bittencourt and .…”

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

“…Recently, Woodman et al (2006) have compared vertical drifts deduced from digisonde measurements to Jicamarca observations of the vertical drifts. The authors find fair agreement at times when strong convection dominates, for example near the pre-reversal enhancement, but poor agreement at times when production and recombination dominate.…”

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

See 3 more Smart Citations

Observations and modeling of post-midnight uplifts near the magnetic equator

et al. 2006

View full text Add to dashboard Cite

Abstract. We report here on post-midnight uplifts near the magnetic equator. We present observational evidence from digital ionosondes in Brazil, a digisonde in Peru, and other measurements at the Jicamarca Radio Observatory that show that these uplifts occur fairly regularly in the post-midnight period, raising the ionosphere by tens of kilometers in the most mild events and by over a hundred kilometers in the most severe events. We show that in general the uplifts are not the result of a zonal electric field reversal, and demonstrate instead that the uplifts occur as the ionospheric response to a decreasing westward electric field in conjunction with sufficient recombination and plasma flux. The decreasing westward electric field may be caused by a change in the wind system related to the midnight pressure bulge, which is associated with the midnight temperature maximum. In order to agree with observations from Jicamarca and Palmas, Brazil, it is shown that there must exist sufficient horizontal plasma flux associated with the pressure bulge. In addition, we show that the uplifts may be correlated with a secondary maximum in the spread-F occurrence rate in the post-midnight period. The uplifts are strongly seasonally dependent, presumably according to the seasonal dependence of the midnight pressure bulge, which leads to the necessary small westward field in the post-midnight period during certain seasons. We also discuss the enhancement of the uplifts associated with increased geomagnetic activity, which may be related to disturbance dynamo winds. Finally, we show that it is possible using simple numerical techniques to estimate the horizontal plasma flux and the vertical drift velocity from electron density measurements in the post-midnight period.

show abstract

Section: Extracting Velocities From Density Measurementssupporting

confidence: 82%

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

Section: Extracting Velocities From Density Measurementsmentioning

confidence: 99%

See 2 more Smart Citations

Observations and modeling of post-midnight uplifts near the magnetic equator

et al. 2006

View full text Add to dashboard Cite

show abstract

“…In contrast, the topside plasma density maintains at some levels, or even increases. In daytime, production and recombination are important; an equilibrium state develops if the drift steadies for a long time [e.g., Rishbeth et al , 1978; Woodman et al , 2006]. However, around sunset, the PRE vertical drift dominates over production and recombination processes, and it changes so quickly with local time that an equilibrium state cannot be reached.…”

Section: Discussionmentioning

confidence: 99%

Solar activity dependence of the topside ionosphere at low latitudes

et al. 2009

View full text Add to dashboard Cite

[1] We investigated the solar activity dependence of the topside ionosphere with ROCSAT-1 observations. The distribution of the plasma density at 600 km altitude shows features with considerable local time, season, and solar activity differences. In the daytime, plasma density peaks around the dip equator. This peak is more distinct in equinoxes and weaker in May-July, and it enhances with solar activity in all seasons. The seasonal behavior of this peak is primarily controlled by the seasonal variations of neutral density and E Â B vertical drift. The enhancement of the peak with solar activity is related to the effect of E Â B vertical drift. Around sunset, double peaks are found in the latitudinal distribution of plasma density in solar maximum equinoxes and December solstice, which are mainly attributed to the effects of strong prereversal enhancement (PRE) vertical drift. Moreover, the plasma density at 600 km altitude strongly depends on the solar proxy P = (F 107 + F 107A )/2. At higher altitudes, e.g., 800 km, the amplification trend prevails in the solar activity variations of plasma density. In contrast, the plasma density at 600 km altitude presents three kinds of patterns (linear, amplification, and saturation), which has not been reported. Saturation effect is found at equinox sunset around the dip equator. This saturation effect is attributed to the increase in the PRE vertical drift with solar activity. Solar activity effects of ROCSAT-1 plasma density are argued to be the combined effects induced by the changes in the peak height, the scale height, and the peak electron density, respectively. Among these factors, the rise of the F 2 peak is more important for the equatorial plasma density at 600 km altitude.

show abstract

Quiet time short‐period and day‐to‐day variations in E × B drift studied using 150 km radar echoes from Gadanki

2014

View full text Add to dashboard Cite

In this paper we present short-period and day-to-day variations in E × B drift during low solar and magnetically quiet conditions, based on radar observations of daytime 150 km echoes from Gadanki, India. Short-period (<100 min) variations in E × B drift show amplitude as large as 7 m s À1 and display large day-to-day variation. Spectral analysis reveals that drift velocity fluctuations consist of several components of short periods in the range of 4-100 min. Among these periods, the most frequently occurring periods are 6-60 min. Observations also show that amplitudes of these periods increase with increasing period. Interestingly, signal-to-noise ratio (SNR) variations also show periods of 3-19 min, which have also been observed in velocity variations. In addition, amplitudes of the periodic variations in SNR tend to increase with increasing period, which is also similar to those observed in drift velocity fluctuations. No correlation between SNR and velocity variations, however, has been found. Noticeable day-to-day variations in drift velocity are found in all seasons, and the variation is as large as ±25 m s À1 . Day-to-day variations also show wave-like features with period of 2-4 days. Observed E × B drift variations of 7 m s À1 at short time scale and 25 m s À1 on a day-to-day basis indicate zonal electric field variations of 0.25 mV/m and 0.9 mV/m, respectively. We surmise that quiet time E × B drift variations with periods <100 min and 2-4 days are likely to be the manifestations of gravity wave and planetary wave wind-induced electric fields, respectively, consistent with those reported earlier.

show abstract

Comparison of ionosonde and incoherent scatter drift measurements at the magnetic equator

Cited by 35 publications

References 13 publications

Observations and modeling of post-midnight uplifts near the magnetic equator

Observations and modeling of post-midnight uplifts near the magnetic equator

Solar activity dependence of the topside ionosphere at low latitudes

Quiet time short‐period and day‐to‐day variations in E × B drift studied using 150 km radar echoes from Gadanki

Contact Info

Product

Resources

About