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Title: The double-gradient magnetic instability: Stabilizing effect of the guide field

The role of the dawn-dusk magnetic field component in stabilizing of the magnetotail flapping oscillations is investigated in the double-gradient model framework (Erkaev et al., Phys. Rev. Lett. 99, 235003 (2007)), extended for the magnetotail-like configurations with non-zero guide field B{sub y}. Contribution of the guide field is examined both analytically and by means of linearized 2-dimensional (2D) and non-linear 3-dimensional (3D) MHD modeling. All three approaches demonstrate the same properties of the instability: stabilization of current sheet oscillations for short wavelength modes, appearing of the typical (fastest growing) wavelength λ{sub peak} of the order of the current sheet width, decrease of the peak growth rate with increasing B{sub y} value, and total decay of the mode for B{sub y}∼0.5 in the lobe magnetic field units. Analytical solution and 2D numerical simulations claim also the shift of λ{sub peak} toward the longer wavelengths with increasing guide field. This result is barely visible in 3D simulations. It may be accounted for the specific background magnetic configuration, the pattern of tail-like equilibrium provided by approximated solution of the conventional Grad-Shafranov equation. The configuration demonstrates drastically changing radius of curvature of magnetic field lines, R{sub c}. This, in turn, favors the “double-gradient” modemore » (λ > R{sub c}) in one part of the sheet and classical “ballooning” instability (λ < R{sub c}) in another part, which may result in generation of a “combined” unstable mode.« less
Authors:
; ;  [1] ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [1] ;  [4] ;  [6] ;  [7] ;  [8] ;  [9]
  1. Saint Petersburg State University, 198504, Ulyanovskaya 1, Petrodvoretz (Russian Federation)
  2. (Sweden)
  3. Institute of Computational Modelling, Russian Academy of Sciences, Siberian Branch, 660036 Krasnoyarsk (Russian Federation)
  4. (Russian Federation)
  5. Space Research Institute RAS, Profsoyuznaya 84/32, Moscow 117997 (Russian Federation)
  6. Centrum voor Plasma-Astrofysica, Departement Wiskunde, Katholieke Universiteit Leuven, B-3001 Leuven (Belgium)
  7. PDC Center for High Performance Computing, KTH Royal Institute of Technology, SE-100 44 Stockholm (Sweden)
  8. Space Research Institute, Austrian Academy of Sciences, 8042 Graz (Austria)
  9. (Austria)
Publication Date:
OSTI Identifier:
22408010
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; ANALYTICAL SOLUTION; APPROXIMATIONS; BALLOONING INSTABILITY; COMPUTERIZED SIMULATION; GRAD-SHAFRANOV EQUATION; MAGNETIC FIELDS; MAGNETOHYDRODYNAMICS; MAGNETOTAIL; OSCILLATIONS; THREE-DIMENSIONAL CALCULATIONS; TWO-DIMENSIONAL CALCULATIONS; WAVELENGTHS