The HILAT program

Fremouw, E. J.; Rino, C. L.; Vickrey, J. F.; Hardy, D. A.; Huffmnan, R. E.; Rich, F. J.; Meng, C.‐I.; Potocki, K.; Potemra, T. A.; Hanson, W. B.; Heelis, R. A.; Wittwer, Leon A.

doi:10.1029/eo064i018p00163

Cited by 15 publications

(3 citation statements)

References 16 publications

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“…Indeed, in one such case study involving rocket probe, scintillation, and incoherent scatter radar observations of irregularities in the auroral ionosphere, phase spectral slopes varying from -1 to -4 were obtained . The HILAT satellite, which combines various in situ measurements and a multifrequency beacon [Fremouw et al, 1983], should provide a unique opportunity of studying scintillation spectra and determining the auroral conditions associated with such spectra. In particular, the multifrequency beacon should provide an opportunity of determining the variation of scintillation magnitude with frequency, a variation which is expected to be small in large flow regions with shallow spectral slopes.…”

Section: Earlier Studies By Kelley and Carlson [1977] And Kintrier [1mentioning

confidence: 99%

F region electron density irregularity spectra near auroral acceleration and shear regions

Basu¹,

MacKenzie²,

Coley³

et al. 1984

J. Geophys. Res.

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Spectral characteristics of auroral F region irregularities were studied by the use of high‐resolution (∼35 m) density measurements made by the retarding potential analyzer (RPA) on board the Atmosphere Explorer D (AE‐D) satellite during two orbits when the satellite was traversing the high‐latitude ionosphere in the evening sector. Coordinated DMSP passes provided synoptic coverage of auroral activity. The auroral energy input was estimated by intergrating the low‐energy electron (LEE) data on AE‐D. It was found that the one‐dimensional in situ spectral index (p1) of the irregularities at scale lengths of <1 km showed considerable steepening in regions of large auroral acceleration events with p1 values of ∼ −3. This is interpreted as resulting from the effects of E region conductivity on the F region irregularity structure. The regions in between the precipitation structures, where presumably the E region conductivity was small, were generally associated with large shears in the horizontal E‐W drifts and large velocities, as measured by the ion drift meter on board AE‐D. The maximum drifts measured were ∼2 km s−1, corresponding to an electric field of 100 mV m−1. The large‐velocity regions were also associated with substantial ion heating and electron density depletions. The largest shear magnitudes observed were ∼80 m s−1 km−1, and the shear gradient scale lengths were ∼10 km, which was approximately the resolution of the ion drift meter data set used. The spectral characteristics of irregularities in the large, variable flow regions were very different, with p1 being ∼−1. Since these regions were also associated with the largest irregularity amplitudes, it seemed probable that either the velocity shears or, alternatively, the large velocities provided a source of irregularities in the auroral F region ionosphere. Current work on plasma instabilities related to velocity shears and two‐dimensional fluid turbulence is briefly summarized and critically compared to the findings of the present study.

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Section: Earlier Studies By Kelley and Carlson [1977] And Kintrier [1mentioning

confidence: 99%

F region electron density irregularity spectra near auroral acceleration and shear regions

Basu¹,

MacKenzie²,

Coley³

et al. 1984

J. Geophys. Res.

Self Cite

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“…The current convective instability has recently been suggested as a mechanism to generate density irregularities in the auroral ionosphere Viekrey et al, 1980;Chaturvedi and Ossakow, 1981;Ossakow, 1982, 1983]. These irregularities can cause the scintillation phenomena observed by the Defense Nuclear Agency (DNA) wideband satellite during periods of diffuse aurora [Fremouw et al, 1977;Rino et al, 1978] and will be an important area of study of the DNA HILAT satellite mission [Fremouw et al, 1983]. The current convective instability can become unstable in a plasma that supports a density gradient (perpendicular to the ambient magnetic field) and a current that flows parallel to the ambient B field; a situation which can occur in the diffuse auroral zone.…”

Section: Introductionmentioning

confidence: 99%

Long wavelength limit of the current convective instability

Huba¹

1984

J. Geophys. Res.

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A linear theory is presented of the current convective instability in the long wavelength limit, i.e., kL << 1 where k is the wave number and L is the scale length of the density inhomogeneity. A relatively simple dispersion equation is derived that describes the modes in this limit. Analytical solutions are presented in both the collisional (vin >> to) and inertial (vin <• to) limits where to is the wave frequency and v• is the ion-neutral collision frequency. It is shown that the growth rate scales as k in the collisional limit and as k 2/3 in the inertial limit. The analytical solutions are compared to exact numerical solutions, and very good agreement is found. Applications to the auroral ionosphere are discussed.

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“…HILAT returned a number of images in 1983 with a 30A spectral resolution and 5 x 20 km spatial resolution at nadir. The AIM instrumentation aboard HILAT has been described in several references [3], [5]- [7]. In late 1986, GL, now named Geophysics Directorate of Phillips Laboratory, conducted a second satellite experiment aboard the Polar BEAR satellite [SI, [9].…”

Section: Introductionmentioning

confidence: 99%

Far ultraviolet remote sensing of ionospheric emissions by Polar BEAR

Oznovich

Ravitz

Tur

et al. 1993

IEEE Trans. Geosci. Remote Sensing

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A few thousands of far ultraviolet images of the ionosphere were obtained since December 1986 by the Atmospheric/Ionospheric Remote Sensor (AIRS) aboard the Polar BEAR satellite. Fast algorithms for applying automated satelliteattitude, geometric, and photometric corrections to these images were developed, and the first results are discussed. A software package that is based on these algorithms was implemented and tested by us. Since no attitude data is available at night (one of the two gauges is a sun sensor), an algorithm was devised to extrapolate daytime attitude corrections to nighttime. An additional method is offered to correct satellite roll from the measured or extrapolated one based on the dayglow limbs observed at the edges of the image. Geometric rectifications include transformations to the image from the satellite coordinate system to a reference system, and from the reference system to the geographic coordinate system. Radiometric corrections include image enhancement, background airglow subtraction, and off-nadir normalization of auroral emissions. The latter two are based on theoretical calculations of column emission rates, derived by radiative transfer integrations of volume emission rates along the look direction. Results include mapping of auroral arcs in the corrected geomagnetic system, the one most applicable to auroral studies.

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The HILAT program

Cited by 15 publications

References 16 publications

F region electron density irregularity spectra near auroral acceleration and shear regions

F region electron density irregularity spectra near auroral acceleration and shear regions

Long wavelength limit of the current convective instability

Far ultraviolet remote sensing of ionospheric emissions by Polar BEAR

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