Abstract
The present work aims to develop a better understanding of wave and turbulence processes in the planetary magnetosheath region. We study the plasma conditions (temperature, flow velocity, and magnetic field), the low-frequency wave properties, and the energy spectra for magnetic field fluctuations in the Venus magnetosheath. We use the magnetic field data of 101 magnetosheath flank crossings from the Venus Express magnetometer experiment in the years 2006 and 2008. The statistical investigation of the plasma conditions shows that the mean magnetic field amplitude is about 10 nT, the average proton temperature of the order of MK, and the super-Alfvenic, subsonic bulk plasma flow. Below 0.07 Hz, the angle of propagation is about 80° for the most of the cases, and it varies from 10° to 90° above the frequency 0.07 Hz. The compressibility shows similar distribution at low (below 0.07 Hz) and high frequencies (above 0.07 Hz). The energy spectra in the spacecraft frequency frame reveal the power-law behaviors which give physical insight on the energy transfer from larger to smaller scales due to wave–wave interaction. A spectral break (sudden change in slope) is observed at 0.25 Hz, above which the spectral curve becomes steeper with spectral indices between −4 and −1.5 (close to the Kolmogorov slope, −5/3). The low-frequency part (below 0.07 Hz) having a spectral index close to −1 indicates the energy cascades due to mirror mode waves, and the steepen spectra at high frequencies (above 0.07 Hz) with spectral indices between −4 and −0.5 are interpreted as the energy accumulation due to mirror mode and proton cyclotron waves.
Highlights
The plasma environment around Venus serves as a natural laboratory to study wave activity and turbulence caused by the solar wind interaction with the nonmagnetized planetary body
We investigate the spectral features of the magnetic field fluctuations in magnetosheath and we find that the magnetic field fluctuations are about to evolve into turbulence
The prominent peak appears at a spectral index close to −1 for the majority of the cases, and the secondary peaks exist with smaller spectral indices
Summary
The plasma environment around Venus serves as a natural laboratory to study wave activity and turbulence caused by the solar wind interaction with the nonmagnetized planetary body. Venus does not have its own intrinsic magnetic field. The supersonic solar wind bears a magnetic field and electric field. This electric field plays a crucial role in the removal of the planetary atmosphere from an unmagnetized planet. The ultraviolet radiations coming from the sun ionizes the upper atmosphere of the planet creating an ionosphere. The ionosphere hinders the solar wind when the thermal pressure of the Dwivedi et al Earth, Planets and Space (2015) 67:137 called the ionopause, and the magnetotail.
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