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  • 1
    Electronic Resource
    Electronic Resource
    Shear flow instabilities in the Earth’s magnetotail (1996)
    Springer
    Annales geophysicae 14 (1996), S. 786-793 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Shear flow instability is studied in the Earth’s magnetotail by treating plasma as compressible. A dispersion relation is derived from the linearized MHD equations using the oscillating boundary conditions at the inner central plasma sheet/outer central plasma sheet (OCPS) interface and OCPS/plasma-sheet boundary layer (PSBL) interface, whereas the surface-mode boundary condition is used at the PSBL/lobe interface. The growth rates and the real frequencies are obtained numerically for near-Earth (\midX\mid\sim10-15 RE) and far-Earth (\midX\mid\sim100 RE) magnetotail parameters. The periods and wavelengths of excited modes depend sensitively on the value of plasma-sheet half thickness, L, which is taken as L=5 RE for quiet time and L=1 RE for disturbed time. The plasma-sheet region is found to be stable for constant plasma flows unless MA3〉1.25, where MA3 is the Alfvén Mach number in PSBL. For near-Earth magnetotail, the excited oscillations have periods of 2–20 min (quiet time) and 0.5-4 min (disturbed time) with typical transverse wavelengths of 2–30 RE and 0.5-6.5 RE, respectively; whereas for distant magnetotail, the analysis predicts the oscillation periods of \sim8-80 min for quiet periods and 2–16 min for disturbed periods.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-996-0786-z
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  • 2
    Electronic Resource
    Electronic Resource
    Shear flow instabilities in the earth’s plasma sheet region (1994)
    Springer
    Annales geophysicae 12 (1994), S. 25-32 
    Details
    ISSN: 0992-7689
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Shear flow instability arising from the velocity shear between the inner and the outer central plasma sheet regions is studied by treating the plasma as compressible. Based on the linearized MHD equations, dispersion relations for the surface wave modes occurring at the boundary of the inner central plasma sheet (ICPS) and the outer central plasma sheet (OCPS) are derived. The growth rates and the eigenmode frequencies are obtained numerically. Three data sets consisting of parameters relevant to the earth’s magnetotail are considered. The plasma sheet region is found to be stable for constant plasma flows unless MA〉9.6, where MA is the Alfvén Mach number in the ICPS. However, for a continuously varying flow velocity profile in the ICPS, the instability is excited for MA\geq1.4. The excited modes have oscillation periods of 2–10 min and 1.5–6 s, and typical transverse wavelengths of 30–100 RE and 0.5–6 RE for data sets 1 and 2 (i.e., case of no neutral sheet) respectively. For the data set 3, which corresponds to a neutral sheet at the center of the plasma sheet, the excited oscillations have periods of 2 s-1 min with transverse wavelengths of 0.02–1 RE.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s00585-994-0025-4
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  • 3
    Electronic Resource
    Electronic Resource
    Low-frequency electric field fluctuations excited by ring current protons (1996)
    Springer
    Earth, moon and planets 74 (1996), S. 231-242 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Energetic protons haying ring type distributions are shown to generate low-frequency electrostatic waves, propagating nearly transverse to the geomagnetic field lines, in the ring current region by exciting Mode 1 arid Mode 2 nonresonant instabilities and a resonant instability. Mode 1 nonresonant instability has frequencies around ~4 Hz with transverse wavelengths of ~(8–80) km, and it is likely to occur in the region L = (7–8). Mode 2 nonresonant instability can generate frequencies ~(850–1450) Hz with transverse wavelengths ~(2–20) km. The typical frequencies and transverse wavelengths associated with the resonant instability are (950–1250) Hz and (30–65) km. Both the Mode 2 nonresonant instability and the resonant instability can occur in the ring current region with L = (4–6). The low-frequency modes driven by energetic protons could attain maximum saturation electric field amplitude varying from 0.8 mV/m to 70 mV/m. It is suggested that the turbulence produced by the low-frequency modes may cause pitch angle scattering of ring current protons in the region outside the plasmapause resulting in the ring current decay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00055189
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  • 4
    Electronic Resource
    Electronic Resource
    Shear flow instability near the cusp resonance in magnetopause boundary layer (1994)
    Springer
    Earth, moon and planets 64 (1994), S. 107-115 
    Details
    ISSN: 1573-0794
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Shear flow instability is studied in the planar magnetopause boundary layer region by treating the plasma as compressible. A necessary criterion for instability near the cusp resonance is obtained analytically. The criterion depends on plasmaβ, Alfvén Mach numberM A and the ratio of the scale lengths of the gradients in the flow and Alfvén velocities. The instability at the cusp resonance layer can be excited rather easily for the lowβ plasma and for shear flow scale length smaller than the typical scale length over which Alfvén velocity varies. The growth rate for instability is obtained for anyβ from a cubic equation. The unstable modes may contribute to the ULF wave activity at the magnetopause.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00604481
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  • 5
    Electronic Resource
    Electronic Resource
    Instability near proton-cyclotron harmonics due to anti-loss cone proton distributions (1980)
    Springer
    Astrophysics and space science 68 (1980), S. 175-182 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Waves with frequencies near the harmonics of the proton-cyclotron frequency, and propagating almost transverse to the ambient magnetic field, can become unstable by hot protons having an anti-loss cone (ALC) distribution function. The maximum growth rates increase with an increase in anti-loss cone index, ratio of the temperatures of trapped to missing protons, and with a decrease inβ H (β H being the ratio of transverse thermal pressure of protons to magnetic field pressure). The growth rates are typically in the range 0.01–1.0 Ω, where Ω is the proton-cyclotron frequency. This instability may be relevant to the observations of EHC waves on auroral field lines (Kintner, 1979), ULF waves in the day-side magnetosphere (Perrautet al., 1978) and the lowfrequency part of the electric field spectrum (from 5 Hz to 20 Hz) in the region upstream of the bow-shock (Gurnettet al., 1979).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00641653
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  • 6
    Electronic Resource
    Electronic Resource
    Electromagnetic lower hybrid instability driven by solar wind heat flux (1979)
    Springer
    Astrophysics and space science 63 (1979), S. 511-516 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Under a fully electromagnetic treatment, the threshold for excitation of the lower hybrid instability driven by solar wind electron heat flux is found to be much higher than that predicted by electrostatic approximation. For average solar wind conditions at 1 AU, the fully electromagnetic lower hybrid instability is excited when the core electron drift speed is about 8V A, whereV A is the Alfvén speed. The region between the Sun and 1 AU is expected to be more favourable than 1 AU for this instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00638919
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  • 7
    Electronic Resource
    Electronic Resource
    Tearing modes in the magnetopause current sheet (1983)
    Springer
    Astrophysics and space science 97 (1983), S. 421-426 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simple method is proposed to investigate the stability of a charge neutral magnetopause current sheet with respect to the tearing-mode instability. This method may serve as a useful tool in understanding the processes of local opening of the closed magnetosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00653497
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  • 8
    Electronic Resource
    Electronic Resource
    Proton-cyclotron instabilities in non-uniform loss-cone magnetospheric plasma (1980)
    Springer
    Astrophysics and space science 70 (1980), S. 467-481 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The waves, propagating nearly transverse to the ambient magnetic field, with frequencies near the harmonics of the proton-cyclotron frequency are studied in an inhomogeneous plasma with protons having loss-cone distributions. Three types of drift cyclotron instabilities have been studied: (i) non-flute instability; (ii) ∇B-resonant instability; and (iii) non-resonant instability. Increases of loss-cone and density gradient increase the growth rates of all three instabilities. Increases in the positive temperature gradient and βt (ratio of thermal pressure of trapped protons to magnetic field pressure) have a stabilizing effect on the non-flute and non-resonant instabilities and a destabilizing effect on the ∇B-resonant instability. The non-resonant instability has an interesting feature: a particular harmonic can be excited in two separate bands of unstable wave numbers. These instabilities can play an important role in the dynamics of the ring current and the inner edge of the plasma sheet region of the magnetosphere. The discrete turbulence generated by them would give rise to precipitation of protons on the auroral field lines, which may contribute to the excitation of diffuse aurora. These instabilities may be relevant to the observation of harmonic waves at 6R E by Perrautet al. (1978).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639571
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  • 9
    Electronic Resource
    Electronic Resource
    Collisionless tearing modes in the presence of shear flow (1983)
    Springer
    Astrophysics and space science 89 (1983), S. 293-300 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Tearing modes in a plane collisionless current sheet with shear bulk flow are studied. An analytic expression for the growth rate is obtained for the case $$M^2 = (1 - \varepsilon {\text{ sech}}^m \bar z)$$ , whereM is the Mach number,m the shear flow index, ε a positive constant less than unity, and $$\bar z$$ the (normalized) co-ordinate normal to the current sheet. The growth rates are large and the unstable wave number domain is increased as compared to the case without flow. The relevance of these results to time-dependent reconnection processes in the Earth's magnetosphere is discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00655982
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  • 10
    Electronic Resource
    Electronic Resource
    Oblique solitary Alfvén modes in relativistic electron-positron plasmas (1996)
    Springer
    Astrophysics and space science 240 (1996), S. 215-224 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract In electron-positron plasmas the charge-to-mass ratio is the same for both species. This leads for different waves to the vanishing of certain coefficients in the dispersion laws and nonlinear evolution equations, and also to the decoupling of some of the plasma modes. In particular, there is a low-frequency mode which exists at all angles of propagation with respect to the static magnetic field, corresponding at parallel propagation to a degenerate case of circularly polarized waves, and at perpendicular propagation to part of the extraordinary mode. The nonlinear evolution of this generalizedX-mode is governed by a Korteweg-de Vries equation, valid at all angles of propagation except strictly parallel propagation, for which a different approach had been given already. The nonlinearity is strongest at perpendicular propagation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00639586
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