Measurement of three‐dimensional plasma velocities at the Arecibo Observatory

Hagfors, T.; Behnke, R. A.

doi:10.1029/rs009i002p00089

Cited by 41 publications

(31 citation statements)

References 4 publications

(1 reference statement)

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“…[28] Concerning the correlation of random errors in the beam-swinging experiment, Hagfors and Behnke [1974] pointed out that one must be careful in not assigning any geophysical interpretation to this effect. Thus it is important to be able to distinguish between the signature of nonphysical correlations introduced by random noise and the actual motion of the ionosphere.…”

Section: Correlation Of Errors and Horizontal Motionmentioning

confidence: 99%

“…Perpendicular east first row, perpendicular north second row and parallel third row. components were originally computed by Hagfors and Behnke [1974] for different azimuth rotation schemes (e.g., 0 -360°, 0-180°) using the LSF method. In addition, these authors looked at the correlation between random fluctuations of the different components and found that for a rotation scheme 0 -360°, the perpendicular-north and parallel components are almost anticorrelated (hV par V pn i = À0.9).…”

Section: Correlation Of Errors and Horizontal Motionmentioning

confidence: 99%

“…[3] For more than 3 decades, the Arecibo ISR has provided measurements of ion vector velocities by using the technique developed by Hagfors and Behnke [1974]. This method takes advantage of the azimuth steering capabilities of Arecibo so that incoherent scatter (IS) autocorrelation functions are measured while rotating the line feed antenna continuously in azimuth at 15 degrees off zenith.…”

Section: Introductionmentioning

confidence: 99%

“…[5] Following the upgrade of the IS spectral measurements, Burnside et al [1987] modified the method of Hagfors and Behnke [1974] to allow for the possibility of constant horizontal gradients. Their study found mostly negligible gradients in the horizontal plane (h dv x dx i % 0, h dv y dy i % 0) but a small horizontal gradient in the vertical velocity dv z dx , which can reach 0.1 m/s/km and lead to a significant error of about 30 m/s in v x if not taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Application of linear regularization methods to Arecibo vector velocities

2005

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[1] Estimates of the three-dimensional ion velocity field can be difficult to make with monostatic radars because there are three unknown components for each independent line of sight velocity measurement. To cope with this problem, one or more assumptions about the vector field must be made to arrive at a solution. At Arecibo, one can measure the ion vector velocities by continuously rotating the antenna beam back and forth 360 degrees in azimuth at 15 degrees off zenith to sample the horizontal components. Until recently, the line of sight velocities obtained from this experiment were typically converted into vector velocities by assuming that the vector field remains constant during one rotation and that horizontal gradients are negligible. In this paper we show how to apply the linear regularization inversion method to the problem of computing ion vector velocities. This technique improves the accuracy of the vector velocities obtained from the measured F region line of sight velocities and also provides a convenient way to do the computations for dual-beam experiments. The technique could improve the vector velocities at other monostatic incoherent scatter radar facilities.

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Section: Correlation Of Errors and Horizontal Motionmentioning

confidence: 99%

Section: Correlation Of Errors and Horizontal Motionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Application of linear regularization methods to Arecibo vector velocities

2005

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“…Inversion methods have also been used to improve zero lag accuracy of multipulse experiments (Lehtinen and Huuskonen, 1986). Another inversion based analysis method is also being developed using data from Arecibo (Nikoukar et al, 2008 1 ), where linear inversion methods are also used for measuring vector velocities (Hagfors and Behnke, 1974;Sulzer et al, 2005). We apply lag profile inversion to data obtained from standard alternating code experiments.…”

Section: Introductionmentioning

confidence: 99%

Lag profile inversion method for EISCAT data analysis

Virtanen

Lehtinen²,

Nygrén

et al. 2008

Ann. Geophys.

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Abstract. The present standard EISCAT incoherent scatter experiments are based on alternating codes that are decoded in power domain by simple summation and subtraction operations. The signal is first digitised and then different lagged products are calculated and decoded in real time. Only the decoded lagged products are saved for further analysis so that both the original data samples and the undecoded lagged products are lost. A fit of plasma parameters can be later performed using the recorded lagged products. In this paper we describe a different analysis method, which makes use of statistical inversion in removing range ambiguities from the lag profiles. An analysis program carrying out both the lag profile inversion and the fit of the plasma parameters has been constructed. Because recording the received signal itself instead of the lagged products allows very flexible data analysis, the program is constructed to use raw data, i.e. IQsampled signal recorded from an IF stage of the radar. The program is now capable of analysing standard alternatingcoded EISCAT experiments as well as experiments with any other kind of radar modulation if raw data is available. The program calculates the ambiguous lag profiles and is capable of inverting them as such but, for analysis in real time, time integration is needed before inversion. We demonstrate the method using alternating code experiments in the EISCAT UHF radar and specific hardware connected to the second IF stage of the receiver. This method produces a data stream of complex samples, which are stored for later processing. The raw data is analysed with lag profile inversion and the results are compared to those given by the standard method.

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The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle

Dandenault

Richards

2015

JGR Space Physics

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This paper investigates the causes of the sudden descent (midnight collapse) of the ionosphere at Townsville, Australia, during the equinox periods of years between 1970 and 1980. The collapse of hmF2 at midnight is found to occur on 89% of the 330 equinox nights that are investigated, and the mean magnitude of the midnight collapse is 84 km in the March equinox periods and 99 km in the September equinox periods. Observations of hmF2 are used to determine equivalent meridional neutral winds using a first principles physics model. Harmonic analysis of these derived winds reveals the existence of significant diurnal (24 h), semidiurnal (12 h), and terdiurnal (8 h) tidal components. The contribution of wind harmonics to the midnight collapse is determined by band‐pass filtering the winds to only allow certain tides and then modeling their effect on hmF2 near midnight. The results indicate that the diurnal, semidiurnal, and terdiurnal components of the meridional neutral wind all play a significant role at various times, but the effect of the 6 h wind component is minimal. The spectral analysis also reveals that the terdiurnal wind component becomes dominant during solar maximum. Electric fields do not appear to be responsible for the midnight hmF2 collapse because it is seldom seen at the near‐conjugate station of Akita, Japan.

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Measurement of three‐dimensional plasma velocities at the Arecibo Observatory

Cited by 41 publications

References 4 publications

Application of linear regularization methods to Arecibo vector velocities

Application of linear regularization methods to Arecibo vector velocities

Lag profile inversion method for EISCAT data analysis

The collapse of the midnight ionosphere and behavior of meridional neutral winds at Townsville over a full solar cycle

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