Turbulence and intermittency of electron density fluctuations in the inner heliosphere: Solar Orbiter first data.

2021 ◽  
Author(s):  
Luca Sorriso-Valvo ◽  
Francesco Carbone ◽  
Yuri Yuri Khotyaintsev ◽  
Daniel Graham ◽  
Konrad Steinvall ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Electron Density ◽  
Density Fluctuations ◽  
General Context ◽  
Frequency Wave ◽  
Mode Decomposition ◽  
Spacecraft Potential ◽  
Electron Density Fluctuations ◽  
Inner Heliosphere

<p>The recently released spacecraft potential measured by the RPW instrument onboard Solar Orbiter has been used to estimate the solar wind electron density in the inner heliosphere. Selected intervals have been extracted to study and quantify the properties of turbulence. Empirical Mode Decomposition was used to obtain the generalized marginal Hilbert spectrum, equivalent to the structure functions analysis, additionally reducing issues typical of nonstationary time series. Results show the presence of a well defined inertial range with Kolmogorov scaling. However, the turbulence shows intermittency only in part of the samples, while other intervals have homogeneous scale-dependent fluctuations. These are observed predominantly during intervals of ion-frequency wave activity. Comparisons with compressible magnetic field intermittency (from the MAG instrument) and with an estimate of the solar wind velocity (using electric and magnetic field) are also provided to provide general context and help determine the cause for the absence of intermittency.</p>

Sub-ion scale measurements of compressible turbulence in the solar wind MMS Observations

2020 ◽  
Author(s):  
Owen Roberts ◽  
Rumi Nakamura ◽  
Yasuhito Narita ◽  
Justin Holmes ◽  
Zoltan Voros ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Power Spectrum ◽  
Electron Density ◽  
Field Measurements ◽  
Small Region ◽  
Density Fluctuations ◽  
Compressible Turbulence ◽  
Density Spectrum ◽  
Spacecraft Potential

<p>Compressible plasma turbulence is investigated at sub ion scales using both the Fast Plasma Investigation instrument on the Magnetospheric MultiScale mission as well as using calibrated spacecraft potential. The data from FPI allow inertial and a small region of sub-ion scales to be investigated before the instrumental noise becomes significant near 3Hz. In this work we give a detailed description of the spacecraft potential and how it is calibrated such that it can be used the measure the electron density. The key advantage of using the calibrated spacecraft potential is that a much higher time resolution is possible when compared to the direct measurement. This allows a measurement down to 40Hz for a measurement of the electron density. This is an improvement of an additional decade in scale. Using a one hour interval of solar wind burst mode data the power spectrum of the density fluctuations is measured from the inertial range to the sub ion range. At inertial scales the density spectrum shows similarities with the magnetic field power spectrum with a characteristic Kolmogorov like power law. In between the ion inertial and kinetic scales there is a brief flattening in the spectra before steepening in the sub ion range to a spectral index comparable to the trace magnetic field fluctuations. The morphology if the density spectra can be explained by either a cascade of Alfv\'en waves and slow waves at large scales and kinetic Alfv\'en waves at sub ion scales, or by the presence of the hall effect. Using electric field measurements the two hypotheses are tested.</p>

scholarly journals Interplanetary Type III Bursts and Electron Density Fluctuations in the Solar Wind

2018 ◽  
Vol 857 (2) ◽  
pp. 82 ◽  
Author(s):  
V. Krupar ◽  
M. Maksimovic ◽  
E. P. Kontar ◽  
A. Zaslavsky ◽  
O. Santolik ◽  
...  
Keyword(s):  
Solar Wind ◽  
Electron Density ◽  
Density Fluctuations ◽  
Type Iii ◽  
Electron Density Fluctuations

scholarly journals Rapid density fluctuations in the solar wind

2005 ◽  
Vol 23 (12) ◽  
pp. 3765-3773 ◽  
Author(s):  
P. J. Kellogg ◽  
T. S. Horbury
Keyword(s):  
Solar Wind ◽  
Electron Density ◽  
Acoustic Waves ◽  
Density Fluctuations ◽  
Magnetic Fluctuations ◽  
Pressure Balance ◽  
Ion Acoustic Waves ◽  
Ion Density ◽  
Ion Acoustic ◽  
Electron Density Fluctuations

Abstract. Electron density fluctuations (up to 2.5 Hz) in the solar wind have been studied, using the EFW experiment on the Cluster spacecraft, which measures density through measurements of the biased probe potentials relative to the spacecraft. The density fluctuation spectra obtained from the EFW probe potential variations are compared to earlier, OGO 5, measurements of ion density fluctuations and ISEE measurements of electron density fluctuations, and are consistent with them. The electric fields corresponding to the electron density fluctuations are extremely small compared with what would be obtained if the electron fluctuations were not cancelled out by nearly equal ion density fluctuations. This is consistent with the nature of ion acoustic waves. In agreement with ISEE work, the fluctuations are proportional to the ambient density. Correlation with magnetic fluctuations is weak, essentially nonexistent during part of the period studied. This might be expected as magnetic fluctuations are known to be nearly incompressible, but even the correlation with fluctuations in the magnitude of B is very small. However, many structures which apparently are pressure balance structures are found. Pressure balance structures are the nearly perpendicular propagation limit of ion acoustic waves. As ion acoustic waves are strongly damped in plasmas like the solar wind at least if the plasma is taken as Maxwellian, it has always been a puzzle as to why they are found there. We speculate that these waves are created by mode conversion from magnetic fluctuations, and may represent part of the dissipation process for these.

scholarly journals Looking for a proxy of the ionospheric turbulence with Swarm data

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Paola De Michelis ◽  
Giuseppe Consolini ◽  
Alessio Pignalberi ◽  
Roberta Tozzi ◽  
Igino Coco ◽  
...  
Keyword(s):  
Electron Density ◽  
Geomagnetic Activity ◽  
Density Fluctuations ◽  
Rate Of Change ◽  
Topside Ionosphere ◽  
Joint Probability Distribution ◽  
Activity Levels ◽  
Scaling Exponents ◽  
Electron Density Fluctuations ◽  
Scaling Features

AbstractThe present work focuses on the analysis of the scaling features of electron density fluctuations in the mid- and high-latitude topside ionosphere under different conditions of geomagnetic activity. The aim is to understand whether it is possible to identify a proxy that may provide information on the properties of electron density fluctuations and on the possible physical mechanisms at their origin, as for instance, turbulence phenomena. So, we selected about 4 years (April 2014–February 2018) of 1 Hz electron density measurements recorded on-board ESA Swarm A satellite. Using the Auroral Electrojet (AE) index, we identified two different geomagnetic conditions: quiet (AE < 50 nT) and active (AE > 300 nT). For both datasets, we evaluated the first- and second-order scaling exponents and an intermittency coefficient associated with the electron density fluctuations. Then, the joint probability distribution between each of these quantities and the rate of change of electron density index was also evaluated. We identified two families of plasma density fluctuations characterized by different mean values of both the scaling exponents and the considered ionospheric index, suggesting that different mechanisms (instabilities/turbulent processes) can be responsible for the observed scaling features. Furthermore, a clear different localization of the two families in the magnetic latitude—magnetic local time plane is found and its dependence on geomagnetic activity levels is analyzed. These results may well have a bearing about the capability of recognizing the turbulent character of irregularities using a typical ionospheric plasma irregularity index as a proxy.

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