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Decay of Solar Wind Turbulence behind Interplanetary Shocks

2017; IOP Publishing; Volume: 844; Issue: 1 Linguagem: Inglês

10.3847/1538-4357/aa7bef

1538-4357

Alexander Pitňa, Jana Šafránková, Zdeněk Němeček, Luca Franci,

Geomagnetism and Paleomagnetism Studies

Abstract We investigate the decay of magnetic and kinetic energies behind IP shocks with motivation to find a relaxation time when downstream turbulence reaches a usual solar wind value. We start with a case study that introduces computation techniques and quantifies a contribution of kinetic fluctuations to the general energy balance. This part of the study is based on high-time (31 ms) resolution plasma data provided by the Spektr-R spacecraft. On the other hand, a statistical part is based on 92 s Wind plasma and magnetic data and its results confirm theoretically established decay laws for kinetic and magnetic energies. We observe the power-law behavior of the energy decay profiles and we estimated the power-law exponents of both kinetic and magnetic energy decay rates as −1.2. We found that the decay of MHD turbulence does not start immediately after the IP shock ramp and we suggest that the proper decay of turbulence begins when a contribution of the kinetic processes becomes negligible. We support this suggestion with a detailed analysis of the decay of turbulence at the kinetic scale.