Study of Neptune dayside magnetosheath fluctuations during Voyager-2 flyby

Turbulence in the outer planetary magnetospheres has been relatively less studied than in the Earth's magnetosphere, especially for the ice giants which have been visited only by the Voyager-2 spacecraft so far. The aim of this work is to study the turbulence in Nep-tune's dayside magnetosheath. Voyager-2 magnetometer 3-s averaged magnetic field data were analyzed with several data analysis tech-niques. It was found that most of the magnetosheath magnetic field is aligned in the BT direction. The BR-component spectrum showed the predominance of short-period (5 minutes) oscillations, while the BT- and BN- components showed the occurrence of longer-period (20-50 minutes) oscillations. The Fourier spectrum of the magnetic field showed a breakpoint near 0.00165 Hz. The lower frequency por-tion showed index (absolute values) smaller than 1.0. The higher frequency portion showed a much steeper spectrum, with power law values varying from about 2.0 to 2.4. The statistical kurtosis parameters for BR and BN are higher than 3 in almost all scales, while the BT component (main field direction) has a more Gaussian or sub-Gaussian behavior, specially in scales higher than 20 minutes. The kurtosis is very high at the low frequency spectral power of 40 minutes for the BN-component, indicating asymmetric or non -Gaussian magnetic field distribution in the magnetosheath. The multifractal spectrum is well spread in the magnetosheath revealing a rich and dynamic activity in this region. Overall, the Neptune's magnetosheath is found to have a strong turbulence activity that is com-parable to that of other planetary magnetosheaths.(c) 2022 COSPAR. Published by Elsevier B.V. All rights reserved.

Automated summary

The aim of this study is to investigate the turbulence in Neptune's dayside magnetosheath. Analysis of Voyager-2 magnetometer data revealed that most of the magnetosheath magnetic field is aligned in the BT direction. The Fourier spectrum of the magnetic field showed a breakpoint near 0.00165 Hz, with the lower frequency portion having index values smaller than 1.0 and the higher frequency portion having a steeper power law.