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|Title:||Study on kinetic Alfven wave in inertial regime|
Tiwari, M S
|Keywords:||Inertial Alfven wave;Auroral region;Acceleration;Growth length|
|Abstract:||The effect of electron inertia on kinetic Alfven wave (KAW) has been studied. The inertial Alfven waves propagating in regions of auroral electron acceleration are reported from the FAST spacecraft over its entire altitude range (350-4180), (e.g., Chaston et al., Physics Scripta, T84, (2000) 64). The Vlasov-kinetic theory has been adopted to evaluate the dispersion relation, damping rate and growth length, with respect to the normalized perpendicular wave number (k⊥c/ ωpe) with different plasma density. It is observed that inertial Alfven wave frequency ( ω) is decreasing with (k⊥c/ ωpe) and plasma density. The growth rate and growth length are evaluated for different (me/ βmi), where β is the ratio of electron pressure to the magnetic field pressure, mi,e are the mass of ion and electron, respectively as β = me/ βmi represent boundary between the kinetic and inertial regimes. The effects of electron density on the wave frequency, growth rate and growth length are also given as the wave propagates towards higher density side of the lower ionospheric region. Although, the wave is highly damped, it requires longer distance of propagation as predicted by growth length. Thus, some another mechanism should also be operative to dissipate kinetic Alfven wave energy as the Landau damping mechanism alone is not sufficient due to higher growth length. The results show the scenario of auroral pattern in northern and southern hemisphere (Swift D W, J Geophys Res, 112 (2007) A12207). The significance of the investigation for the auroral acceleration region is also presented.|
|Appears in Collections:||IJPAP Vol.47(05) [May 2009]|
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