Observations of striation formation in a barium ion cloud

Rosenberg, N. W.

doi:10.1029/ja076i028p06856

Cited by 39 publications

(22 citation statements)

References 7 publications

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“…There are several possible explanations for flux tube splitting in barium plasmas. Most ion clouds produced by thermite barium releases at ionospheric altitude have been observed to split up into sheets that then evolved filamentary structures [Rosenberg, 1971;Davis et al, 1974]. Called striation development, the process has been ascribed by most authors to the gradient E x B instability [Linson and Workman, 1970;Vi51k and Haerendel, 1971], which is related to the differential motion of the barium ions with respect to the neutral wind.…”

Section: Discussionmentioning

confidence: 99%

TheL= 6.6 Oosik Barium Plasma Injection Experiment and magnetic storm of March 7, 1972

Wescott¹,

Stenbaek‐Nielsen²,

Davis³

et al. 1975

J. Geophys. Res.

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The high‐altitude detonation of a high‐explosive shaped charge vaporizes a hollow conical liner of barium metal and produces a fast field‐aligned jet of plasma with approximately 1 mol of ions having initial velocities distributed from 8 to 20 km/s. Such a barium plasma injection experiment was performed at 540‐km altitude over Alaska (L = 6.6) in dusk of March 7, 1972 (universal time), in an attempt to trace out and observe the dynamics of an auroral field line in the magnetosphere. With image orthicon TV systems and image intensified cameras the resulting streak rising into the magnetosphere was observed for 30 min and out to 3‐RE altitude. A 1.5‐m‐aperture photometer detected the barium streak at R (release) + 35 min at nominal look angles where the ions would be near altitudes of 5 and 2 RE from the magnetic equator. The injection occurred during a quiescent phase of a magnetic storm initiated by an ssc 10 hours prior to the experiment. Quiet auroral arcs existed over Alaska at locations more than 200 km south of the injection point. The barium flux tube drifted first eastward and then southward owing to an electric field E, with E × B/B² velocities of several hundred meters per second, while also splitting into at least seven separate flux tubes distributed along 200 km parallel to L. At R + 16 min an intense auroral activation and magnetic substorm (the Oosik substorm) began in the Alaskan sector. Subsequent poleward expansion of the aurora and formation of a classic spiral resulted in the intersection and crossing of the barium flux tubes by an auroral arc. Very rapid, almost turbulent, motions of the barium flux observed during the intersection interval resulted from local transient E fields of 200 mV/m directed inward toward the auroral arc. Observations of the distortion of the barium flux tubes on opposite sides of the aurora as compared with a field model including the superdisturbed external coefficients of Mead and Fairfield (1973) offer evidence for an upward Birkeland current sheet at the poleward edge of the auroral spiral of 8 × 10−2 A/m. The Oosik substorm was spatially limited to the dusk sector; it occurred during the decaying phase of a larger substorm observed in the midnight to dawn sector. The substorm and aurora had several unusual features. Examination of the question as to whether the plasma injection may have triggered the substorm unveiled no compelling evidence that it did; however, the unusual features of the substorm leave open that possibility.

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Section: Discussionmentioning

confidence: 99%

TheL= 6.6 Oosik Barium Plasma Injection Experiment and magnetic storm of March 7, 1972

Wescott¹,

Stenbaek‐Nielsen²,

Davis³

et al. 1975

J. Geophys. Res.

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“…This indicates that velocity shear will be more important at high altitudes (> 400 kin) in affecting the Rayleigh-Taylor instability.Artificial plasma clouds (e.g., barium releases) in the ionosphere are subject to a complex and dynamic evolution. One of the more notable characteristics is the striating of the clouds, i.e., "fingers" forming on one side of the cloud(Rosenberg, 1971;Davis et al, 1974). In many cases these striations can be explained by the E x B gradient drift instability(Linson and Workman, 1970; Zabusky et al, 1973;Scannapieco et al, 1976).…”

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Influence of velocity shear on the Rayleigh‐Taylor instability

Guzdar¹,

Satyanarayana²,

Huba³

et al. 1982

Geophysical Research Letters

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The influence of a transverse velocity shear on the Rayleigh‐Taylor instability is investigated. It is found that a sheared velocity flow can substantially reduce the growth rate of the Rayleigh‐Taylor instability in the short wavelength regime (i.e., kL > 1 where L is the scale length of the density inhomogeneity), and causes the growth rate to maximize at kL < 1.0. Applications of this result to ionospheric phenomena [equatorial spread F (ESF) and ionospheric plasma clouds] are discussed. In particular, the effect of shear could account for, at times, the 100’s of km modulation observed on the bottomside of the ESF ionosphere and the km scale size wavelengths observed in barium cloud prompt striation phenomena.

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“…The results obtained are in qualitative agreement with field experiments. 8 We now investigate the linear stability of a twodimensional model of an idealized cloud, namely a piecewise-constant distribution of ions:where D is a simply connected, bounded region in i? 2 with boundary r. The contour, r, deforms with a velocity V d = E. x B/|B| 2 , where EL is the self-consistent electric field on the inside of r and § = B 0 e z is Earth's magnetic field, assumed to be constant.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

“…Note that the induction of a dipole field in the first-order solution causes a downshift by one between the Fourier coefficients of the potential B m a) and the boundary perturbation, a m+1 (1) . To calculate the time evolution of a m (1) we write (7) in polar coordinates in the translating frame of reference If Q = 0 and a(0) = 6 m t mr^ d t R=-R-\dy$_ + R'd r $_)+V d [coS(p+(R'/R)sin<p]-v[R 2^where R'= dR/d<p. Substituting(8) in(12), we ob-, tain, to zeroth order,…”

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Stability and Nonlinear Evolution of Plasma Clouds via Regularized Contour Dynamics

Overman

Zabusky

1980

Phys. Rev. Lett.

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A model is introduced of an ionospheric plasma cloud (deformable dielectric) with a piecewise-constant ion density and a diffusive ^regularized boundary. The linear stability of a single-contour circular cloud is studied and a new evolution equation for modal amplitudes is obtained which has the property that the wave number of maximum amplitude decreases with time (downward cascade). Analytic expressions show that large clouds evolve more slowly and appear more dissipative. PACS numbers: 52.35.Py, 02.70.+d, 41.10.Dq, Ionospheric, collision-dominated, low-jS plasma clouds, driven by ambient, uniform electric fields or winds are being studied for two main reasons. First, they are probes of properties of the natural and disturbed ionosphere. Second, they evolve nonlinearly and yield magnetic field-aligned finescale structures (irregularities or striations) that can degrade radio-wave propagation. 1 Past analytic studies of the evolution of ion densities have been almost entirely confined to the linear stability of one-dimensional (ID) stationary states. Linson and Workman, 2 Shiau and Simon, 3 and Volk and Haerendel 4 attributed the cause of striations to the EXB gradient-drift instability. 5 Presently there are no 2D stationary states of continuous density variation and no 2D stability analyses exist.In recent computational studies, finite-difference algorithms were used to study the evolution of ID and 2D ion density clouds with small-amplitude 2D perturbations. 6 ' 7 It has been found that the growth of sinusoidal perturbations on ID clouds agrees with linear theories. 6 These perturbations evolve into fingerlike striations that emanate from the cloud's "backside" (the direction opposite to the drift velocity EXB"/|.£| 2 ). The results obtained are in qualitative agreement with field experiments. 8 We now investigate the linear stability of a twodimensional model of an idealized cloud, namely a piecewise-constant distribution of ions:where D is a simply connected, bounded region in i? 2 with boundary r. The contour, r, deforms with a velocity V d = E. x B/|B| 2 , where EL is the self-consistent electric field on the inside of r and § = B 0 e z is Earth's magnetic field, assumed to be constant. In the rest of this paper we set .B 0 = l. Our contributions are twofold: (1) We in-troduce a contour dynamical model of the piecewise-constant cloud which generalizes the "waterbag" method. The evolution equations include a physically motivated diffusive regularization procedure 9 which inhibits the formation of contour singularities and makes the system well posed.(2) We analyze the linear stability of a circular region and demonstrate a new linear phenomenon, "downward cascade," namely, the wave number of maximum amplitude decreases with time. Our work is a combined analytical-numerical study.We also use our results to validate a numerical algorithm which solves the nonlinear contour evolution model. The equations of motion of the continuum ionospheric plasma system of Fig. 1 (inset) have been given as 6 V-(iVV$) = 0,...

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Observations of striation formation in a barium ion cloud

Cited by 39 publications

References 7 publications

TheL= 6.6 Oosik Barium Plasma Injection Experiment and magnetic storm of March 7, 1972

TheL= 6.6 Oosik Barium Plasma Injection Experiment and magnetic storm of March 7, 1972

Influence of velocity shear on the Rayleigh‐Taylor instability

Stability and Nonlinear Evolution of Plasma Clouds via Regularized Contour Dynamics

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