A KINETIC ALFVEN WAVE CASCADE SUBJECT TO COLLISIONLESS DAMPING CANNOT REACH ELECTRON SCALES IN THE SOLAR WIND AT 1 AU

Journal Article · Sat Mar 20 00:00:00 EDT 2010 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/712/1/685· OSTI ID:21394230

Podesta, J J; Borovsky, J E

Turbulence in the solar wind is believed to generate an energy cascade that is supported primarily by Alfven waves or Alfvenic fluctuations at MHD scales and by kinetic Alfven waves (KAWs) at kinetic scales k{sub perpendicular}rho{sub i} {approx}> 1. Linear Landau damping of KAWs increases with increasing wavenumber and at some point the damping becomes so strong that the energy cascade is completely dissipated. A model of the energy cascade process that includes the effects of linear collisionless damping of KAWs and the associated compounding of this damping throughout the cascade process is used to determine the wavenumber where the energy cascade terminates. It is found that this wavenumber occurs approximately when |gamma/omega| {approx_equal} 0.25, where omega(k) and gamma(k) are, respectively, the real frequency and damping rate of KAWs and the ratio gamma/omega is evaluated in the limit as k{sub perpendicular} >> k{sub ||}. For plasma parameters typical of high-speed solar wind streams at 1 AU, the model suggests that the KAW cascade in the solar wind is almost completely dissipated before reaching the wavenumber k{sub perpendicular}rho{sub i} {approx_equal} 25. Consequently, an energy cascade consisting solely of KAWs cannot reach scales on the order of the electron gyro-radius, k{sub perpendicular}rho{sub e} {approx} 1. This conclusion has important ramifications for the interpretation of solar wind magnetic field measurements. It implies that power-law spectra in the regime of electron scales must be supported by wave modes other than the KAW.

• OSTI ID: 21394230
• Journal Information: Astrophysical Journal, Vol. 712, Issue 1; Other Information: DOI: 10.1088/0004-637X/712/1/685; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
ALFVEN WAVES
ELECTRONS
FLUCTUATIONS
LANDAU DAMPING
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
PLASMA
SOLAR WIND
TURBULENCE
DAMPING
ELEMENTARY PARTICLES
FERMIONS
FLUID MECHANICS
HYDRODYNAMICS
HYDROMAGNETIC WAVES
LEPTONS
MECHANICS
SOLAR ACTIVITY
STELLAR ACTIVITY
STELLAR WINDS
VARIATIONS