scholarly journals On the Origin of High–Frequency Magnetic Fluctuations in the Interplanetary Medium: A Brownian–like Approach

2021 ◽  
Vol 9 ◽  
Author(s):  
Vincenzo Carbone ◽  
Fabio Lepreti ◽  
Antonio Vecchio ◽  
Tommaso Alberti ◽  
Federica Chiappetta
Keyword(s):  
High Frequency ◽  
Interplanetary Medium ◽  
Interplanetary Space ◽  
Plasma Heating ◽  
Low Frequency ◽  
Solar Wind Plasma ◽  
Magnetic Fluctuations ◽  
Fluctuation Dissipation ◽  
Frequency Fluctuations ◽  
Collisionless Dissipation

Low–frequency fluctuations in the interplanetary medium have been extensively investigated and described in the framework of turbulence, and the observed universal scaling behavior represents a clear signature of the underlying energy cascade. On the contrary, the interpretation of observations of plasma fluctuations at high frequencies, where wave–wave coupling, collisionless dissipation, and anomalous plasma heating play a key role, still represents a challenge for theoretical modeling. In this paper the high frequency fluctuations occurring in the interplanetary space are described through a Brownian–like approach, where the plasma dynamics at small scales is described through a stochastic process. It is shown that a simple model based on this framework is able to successfully reproduce the main features of the spectrum of the observed magnetic fluctuations. Moreover, the Fluctuation-Dissipation Relation, derived by our model, leads to a power law between dissipation rate and temperature, which is compatible with the occurrence of Landau damping, interpreted thus as the main mechanism of dissipation in the solar wind plasma.

scholarly journals High-frequency Magnetic Fluctuations in Space Plasmas and the Role of Electron Landau Damping

2022 ◽  
Vol 924 (2) ◽  
pp. L26
Author(s):  
Vincenzo Carbone ◽  
Daniele Telloni ◽  
Fabio Lepreti ◽  
Antonio Vecchio
Keyword(s):  
High Frequency ◽  
Interplanetary Space ◽  
Magnetic Energy ◽  
Low Frequency ◽  
Theoretical Models ◽  
Landau Damping ◽  
Magnetic Fluctuations ◽  
Frequency Plasma ◽  
New Framework

Abstract While low-frequency plasma fluctuations in the interplanetary space have been successfully described in the framework of classical turbulence, high-frequency fluctuations still represent a challenge for theoretical models. At these scales, kinetic plasma processes are at work, but although some of them have been identified in spacecraft measurements, their global effects on observable quantities are sometimes not fully understood. In this paper we present a new framework to the aim of describing the observed magnetic energy spectrum and directly identify in the data the presence of Landau damping as the main collisionless dissipative process in the solar wind.

Evolution of the MHD turbulence properties in the inner heliosphere with the PSP/SolO alignment data

2021 ◽  
Author(s):  
Daniele Telloni ◽  
Keyword(s):  
Solar Wind ◽  
High Frequency ◽  
Interplanetary Space ◽  
Solar Wind Plasma ◽  
Radial Dependence ◽  
Physical Processes ◽  
Temperature Anisotropy ◽  
Mhd Turbulence ◽  
Radial Evolution ◽  
Inner Heliosphere

<p>Radial alignments between pairs of spacecraft is the only way to observationally investigate the turbulent evolution of the solar wind as it expands throughout interplanetary space. On September 2020 Parker Solar Probe (PSP) and Solar Orbiter (SolO) were nearly perfectly radially aligned, with PSP orbiting around its perihelion at 0.1 au (and crossing the nominal Alfvén point) and SolO at 1 au. PSP/SolO joint observations of the same solar wind plasma allow the extraordinary and unprecedented opportunity to study how the turbulence properties of the solar wind evolve in the inner heliosphere over the wide distance of 0.9 au. The radial evolution of (i) the MHD properties (such as radial dependence of low- and high-frequency breaks, compressibility, Alfvénic content of the fluctuations), (ii) the polarization status, (iii) the presence of wave modes at kinetic scale as well as their distribution in the plasma instability-temperature anisotropy plane are just few instances of what can be addressed. Of furthest interest is the study of whether and how the cascade transfer and dissipation rates evolve with the solar distance, since this has great impact on the fundamental plasma physical processes related to the heating of the solar wind. In this talk I will present some of the results obtained by exploiting the PSP/SolO alignment data.</p>

scholarly journals IPS Observations at Beijing Astronomical Observatory

2002 ◽  
Vol 12 ◽  
pp. 398
Author(s):  
X.Z. Zhang ◽  
J.H. Wu
Keyword(s):  
Solar Wind ◽  
Radio Wave ◽  
High Frequency ◽  
Interplanetary Space ◽  
Solar Wind Speed ◽  
Solar Wind Plasma ◽  
Astronomical Observatory ◽  
Wind Speeds ◽  
Irregular Structures ◽  
Good Agreement

The radio wave from distant radio sources will be scattered by the irregular structures of the solar wind plasma when propagating through the interplanetary space, resulting into a randomly fluctuating pattern of the radio wave in observation. This pattern is called interplanetary scintillation (IPS). Observation on IPS can give information of the solar wind speed and irregular structures in solar wind plasma. The IPS observations began at Miyun Station, Beijing Astronomical Observatory from the late half of 1999. The properties of the telescope and description of the data analysis can be found in the papers of Wang (1987) and Wu, Zhang and Zheng (2000) respectively.Table 1 summarizes some observational results using IPS source 3C48 in April and May 2000. The Fresnel knees and the first minima in the IPS spectra were used to estimate solar wind speeds. Comparisons of our results with the unpublished data of Hiraiso Solar Terrestrial Research Center obtained from their web site, have been done and good agreement between the two systems was found. Since the collecting area of Miyun telescope is limited, the system noise is relatively high and dominates the high-frequency parts of the spectra. The Miyun IPS observation and data reduction procedures are still under developing and will soon be completed.

scholarly journals Spontaneous Magnetic Fluctuations and Collisionless Regulation of Turbulence in the Earth’s Magnetotail

2022 ◽  
Vol 924 (1) ◽  
pp. 8
Author(s):  
C. M. Espinoza ◽  
P. S. Moya ◽  
M. Stepanova ◽  
J. A. Valdivia ◽  
R. E. Navarro
Keyword(s):  
Solar Wind ◽  
Solar Wind Plasma ◽  
Relaxation Processes ◽  
Magnetic Fluctuations ◽  
Temperature Anisotropy ◽  
Satellite Mission ◽  
Astrophysical Plasmas ◽  
Fluctuation Dissipation ◽  
Collisionless Plasmas ◽  
Kinetic Instability

Abstract Among the fundamental and most challenging problems of laboratory, space, and astrophysical plasma physics is to understand the relaxation processes of nearly collisionless plasmas toward quasi-stationary states and the resultant states of electromagnetic plasma turbulence. Recently, it has been argued that solar wind plasma β and temperature anisotropy observations may be regulated by kinetic instabilities such as the ion cyclotron, mirror, electron cyclotron, and firehose instabilities; and it has been argued that magnetic fluctuation observations are consistent with the predictions of the fluctuation–dissipation theorem, even far below the kinetic instability thresholds. Here, using in situ magnetic field and plasma measurements by the THEMIS satellite mission, we show that such regulation seems to occur also in the Earth’s magnetotail plasma sheet at the ion and electron scales. Regardless of the clear differences between the solar wind and the magnetotail environments, our results indicate that spontaneous fluctuations and their collisionless regulation are fundamental features of space and astrophysical plasmas, thereby suggesting the processes is universal.

Assessment of autonomic function in humans by heart rate spectral analysis

1985 ◽  
Vol 248 (1) ◽  
pp. H151-H153 ◽  
Author(s):  
B. Pomeranz ◽  
R. J. Macaulay ◽  
M. A. Caudill ◽  
I. Kutz ◽  
D. Adam ◽  
...  
Keyword(s):  
Heart Rate ◽  
Nervous System ◽  
Spectral Analysis ◽  
High Frequency ◽  
Autonomic Function ◽  
Parasympathetic Nervous System ◽  
Low Frequency ◽  
Parasympathetic System ◽  
Heart Rate Fluctuations ◽  
Frequency Fluctuations

Spectral analysis of spontaneous heart rate fluctuations were assessed by use of autonomic blocking agents and changes in posture. Low-frequency fluctuations (below 0.12 Hz) in the supine position are mediated entirely by the parasympathetic nervous system. On standing, the low-frequency fluctuations increase and are jointly mediated by the sympathetic and parasympathetic nervous systems. High-frequency fluctuations, at the respiratory frequency, are decreased by standing and are mediated solely by the parasympathetic system. Heart rate spectral analysis is a powerful noninvasive tool for quantifying autonomic nervous system activity.

scholarly journals Amplitude Modulation of Relative Humidity by Wind in Northeast China: the Formation of Variance Annual Cycle in Relative Humidity

2021 ◽  
Author(s):  
Da Nian ◽  
Yu Huang ◽  
Zuntao Fu
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Annual Cycle ◽  
Amplitude Modulation ◽  
High Frequency ◽  
Northeast China ◽  
Low Frequency ◽  
Phase Correlation ◽  
Low Frequency Oscillations ◽  
Frequency Fluctuations

Abstract Relative humidity has an important impact not only on climate change and ecosystems but also on human life. The intensity of high-frequency fluctuations in relative humidity over Northeast China shows a predominant seasonally dependent structure, which may be closely related to regional monsoon activities. However, the factors responsible for this phenomenon remain unknown. This study defines the Variance Annual Cycle (VAC) to describe this seasonally dependent intensity structure of high-frequency relative humidity fluctuations. Relative humidity VAC shows a high correlation with low-frequency oscillations of wind speed. We examine the instantaneous amplitude-phase correlation map and amplitude modulation (AM) index between relative humidity and wind speed. We find that the wind speed with a period around 140-420 days has a significant amplitude modulation effect on the relative humidity with a period around 2-90 days over most regions in Northeast China, which reveals that the low-frequency oscillations of wind speed amplitude- modulate on the high-frequency fluctuations of relative humidity. To explore the physical mechanism behind this modulation, we examine the monthly mean patterns of the atmospheric fields. The patterns indicate that this amplitude modulation is induced by the evolution and transition of East Asian winter monsoon and summer monsoon.

scholarly journals On the Magnetic Field Spectrum and Its Fluctuations in a Primeval Cold Plasma in Thermal Equilibrium

2020 ◽  
pp. 10-21
Author(s):  
Francisco Caruso ◽  
Vitor Oguri ◽  
Felipe Silveira
Keyword(s):  
Frequency Spectrum ◽  
High Frequency ◽  
Low Frequency ◽  
Black Body ◽  
New Approach ◽  
Plasma Energy ◽  
Fluctuation Dissipation ◽  
Fluctuation Dissipation Theorem ◽  
Boltzmann Law ◽  
The Magnetic Field

This work reassesses previous results and generalizes the expression for the low-frequency spectrum of magnetic fields fluctuations in a thermal plasma, that was previously obtained within the framework of the fluctuation-dissipation theorem. The new approach presented here is able to avoid any approximation yielding a unique expression that covers both the low- and high-frequency spectrum, without the need of procedures to smooth the junction between the two limit frequency regions formerly used. Also, the simultaneous dependence of this intensity on the plasma and on the collisional frequencies is discussed. Finally, the total emitted plasma energy is compared to the Stefan-Boltzmann law of a pure black-body.

Anomalous transport and anomalous heating due to lower-hybrid wave fields

1988 ◽  
Vol 39 (3) ◽  
pp. 447-474 ◽  
Author(s):  
M. Krämer ◽  
N. Sollich ◽  
J. Dietrich
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Field Energy ◽  
Lower Hybrid ◽  
Hybrid Wave ◽  
Heating Rates ◽  
Lower Hybrid Wave ◽  
Drift Wave Turbulence ◽  
Frequency Fluctuations ◽  
High Frequency Waves

The microscopic and macroscopic behaviours of a linear reflex discharge in the presence of low-frequency turbulence are investigated under the action of moderate lower-hybrid wave power. The frequency and wavenumber spectra of both the low-frequency fluctuations and the high-frequency waves are measured using a correlation-analysis technique with two probes. The low-frequency fluctuations may be attributed to drift-wave turbulence. The fluctuation level is raised when RF power is coupled to the plasma, thus leading to considerably enhanced radial transport. The coupling between low-frequency fluctuations and high-frequency waves can be seen clearly from the spectra. The high-frequency wavenumber spectra measured inside the antenna are in reasonable agreement with the lower-hybrid wave dispersion. However, the wavenumbers observed in the lower-hybrid resonance region outside the antenna are – in contrast with expectation – not larger than in the plasma edge region. From the electric-field energy-density spectra and from measurements of the density and the temperatures, a detailed energy balance can be performed. The calculated heating rates are anomalously large for both the electrons and the ions. The absorption processes, relevant for the present experiment, are discussed.

Non-Respiratory Components of Heart Rate Variability in Heart Transplant Recipients: Evidence of Autonomic Reinnervation?

1994 ◽  
Vol 86 (5) ◽  
pp. 537-545 ◽  
Author(s):  
Luciano Bernardi ◽  
Felice Valle ◽  
Stefano Leuzzi ◽  
Mauro Rinaldi ◽  
Eugenia Marchesi ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Heart Transplant ◽  
High Frequency ◽  
Low Frequency ◽  
Transplant Recipients ◽  
Sinus Arrhythmia ◽  
Control Subjects ◽  
Amyl Nitrite ◽  
Heart Transplant Recipients ◽  
Frequency Fluctuations

1. Although the high-frequency fluctuations in R—R interval (respiratory sinus arrhythmia) observed in heart transplant recipients are not a reliable marker of reinnervation because of a previously shown direct mechanical effect of breathing, the presence of a non-respiration-related low-frequency oscillation reflects rhythms generated outside the heart, and thus could be neurally mediated. 2. To evaluate the presence of reinnervation, the spontaneous variability in R—R interval was investigated, supine and after passive tilting, in 23 heart transplant recipients (age 43 years, range 23–64 years) and in 25 normotensive control subjects by autoregressive spectral analysis of low- and high-frequency spontaneous fluctuations in R—R interval and respiration. The response of R—R interval to amyl nitrite inhalation was also evaluated in five heart transplant recipients and eight control subjects. 3. Detectable low-frequency oscillations, unrelated to respiration, were present in 13/23 heart transplant recipients, particularly in those who were transplanted at least 20 months earlier (11/14). The natural logarithm of the power of low-frequency fluctuations was markedly lower than in control subjects (0.75 ± 0.21 versus 5.62 ± 0.20 ms2, P < 0.001). The low-frequency but not the high-frequency fluctuations correlated with time since transplantation (r = 0.44, P < 0.05). The subjects with low-frequency fluctuations showed a sudden decrease in R—R interval with amyl nitrite linearly related to the decrease in mean blood pressure (r ≧ 0.94). The slopes obtained in these heart transplant recipients were comparable (although of lower values) with those obtained in control subjects. The subjects with no low-frequency fluctuations showed no change in R—R interval despite a similar reduction in blood pressure. 4. Twenty months after transplantation signs of functional (reflex) reinnervation can be found in most heart transplant recipients.

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