@Article{FrancoFräEchBolZha:2020:VEOb,
author = "Franco, Adriane Marques de Souza and Fr{\"a}nz, M. and Echer,
Ezequiel and Bolzan, M. J. A. and Zhang, T. L.",
affiliation = "{Instituto Nacional de Pesquisas Espaciais (INPE)} and {Max Planck
Institute for Solar System Research} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and {Universidade Federal de
Jata{\'{\i}}} and {Space Research Institute of the Austrian
Academy of Sciences}",
title = "The correlation length of ULF waves around Venus: VEX
observations",
journal = "Planetary and Space Science",
year = "2020",
volume = "180",
pages = "e104761",
month = "jan.",
keywords = "Venus induced magnetosphere, ULF waves, Correlation length.",
abstract = "A study of the correlation length of ultra-low frequency (ULF)
waves around Venus was developed using electron density and
magnetic field data obtained from the Analyzer of Space Plasmas
and Energetic Atoms (ASPERA-4) and magnetometer (MAG),
respectively, on board of the mission Venus Express (VEX). The
analysis was conducted using the whole interval of the mission
(2006-2014). The correlation scales have been calculated by the
correlation length parameter that is a characteristic distance
over which fluctuations in a variable are correlated. We limited
the study to the frequency range from 8 to 50 mHz because previous
studies have shown that ULF waves produced in the foreshock have
the highest power in this range. In this study the correlation
length was calculated by an exponential fit employed to the
auto-correlation curve. The auto-correlation function was
calculated lagged by a time between 0 and 60 s and sliding a
window with 120s across the data. This analysis has been also
extended to correlation length determinations in spatial scale. In
order to obtain the correlation length in a spatial domain, the
temporal correlation length must be multiplied by the solar wind
velocity. Here, the ASPERA-4/IMA (Ion Mass Analyzer) velocity data
was used. It was found that the dominant correlation length in
temporal scale varies from 9 to 14 s in electron density and
between 7.5 and 11 s in the magnetic field. In spatial scale,
correlation length varies between 2.8 x 10(3) and 5 x 10(3) km in
electron density data, and between 1.7 x 10(3) -4X10(3) km for the
total magnetic field data value in this frequency window.
Fluctuations in the magnetosheath and in the MPB may be correlated
with fluctuations at the ionosphere, since correlation lengths in
those regions are larger than the size of these regions,
indicating that local resonant effect of wave trains at the
ionopause may enhance the atmospheric ion escape at Venus. Our
results also show that pickup heavy ions can interact with
discontinuities in the magnetosheath of Venus and can destroy ULF
wave trains during periods of low solar wind pressure. The results
obtained here are compared with a similar previous analysis in the
Mars environment.",
doi = "10.1016/j.pss.2019.104761",
url = "http://dx.doi.org/10.1016/j.pss.2019.104761",
issn = "0032-0633",
language = "en",
targetfile = "franco_correlation.pdf",
urlaccessdate = "2024, Apr. 19"
}