scholarly journals Multi-spacecraft observations of small-scale fluctuations in density and fields in plasmaspheric plumes

2012 ◽  
Vol 30 (3) ◽  
pp. 623-637 ◽  
Author(s):  
H. Matsui ◽  
F. Darrouzet ◽  
J. Goldstein ◽  
P. A. Puhl-Quinn ◽  
Yu. V. Khotyaintsev ◽  
...  
Keyword(s):  
Electric Fields ◽  
Small Scale ◽  
Fast Mode ◽  
Magnetic Fluctuations ◽  
Density Enhancement ◽  
Non Local ◽  
Similar Location ◽  
Local Generation ◽  
Alfven Velocity ◽  
Measured Density

Abstract. In this event study, small-scale fluctuations in plasmaspheric plumes with time scales of ~10 s to minutes in the spacecraft frame are examined. In one event, plasmaspheric plumes are observed by Cluster, while IMAGE measured density enhancement at a similar location. Fluctuations in density exist in plumes as detected by Cluster and are accompanied by fluctuations in magnetic fields and electric fields. Magnetic fluctuations are transverse and along the direction of the plumes. The E/B ratio is smaller than the Alfvén velocity. Another similar event is briefly presented. We then consider physical properties of the fluctuations. Alfvén mode modulated by the feedback instability is one possibility, although non-local generation is likely. It is hard to show that the fluctuations represent a fast mode. Interchange motion is possible due to the consistency between measurements and expectations. The energy source could be a pressure or density gradient in plasmaspheric plumes. When more events are accumulated so that statistical analysis becomes feasible, this type of study will be useful to understand the time evolution of plumes.

MHD and Ion Kinetic Waves in Field-aligned Flows Observed by Parker Solar Probe

2021 ◽  
Vol 922 (2) ◽  
pp. 188
Author(s):  
L.-L. Zhao ◽  
G. P. Zank ◽  
J. S. He ◽  
D. Telloni ◽  
L. Adhikari ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Whistler Wave ◽  
Spectral Energy ◽  
Small Scale ◽  
The Sun ◽  
Fast Mode ◽  
Magnetic Fluctuations ◽  
Background Magnetic Field ◽  
Ion Cyclotron

Abstract Parker Solar Probe (PSP) observed predominately Alfvénic fluctuations in the solar wind near the Sun where the magnetic field tends to be radially aligned. In this paper, two magnetic-field-aligned solar wind flow intervals during PSP’s first two orbits are analyzed. Observations of these intervals indicate strong signatures of parallel/antiparallel-propagating waves. We utilize multiple analysis techniques to extract the properties of the observed waves in both magnetohydrodynamic (MHD) and kinetic scales. At the MHD scale, outward-propagating Alfvén waves dominate both intervals, and outward-propagating fast magnetosonic waves present the second-largest contribution in the spectral energy density. At kinetic scales, we identify the circularly polarized plasma waves propagating near the proton gyrofrequency in both intervals. However, the sense of magnetic polarization in the spacecraft frame is observed to be opposite in the two intervals, although they both possess a sunward background magnetic field. The ion-scale plasma wave observed in the first interval can be either an inward-propagating ion cyclotron wave (ICW) or an outward-propagating fast-mode/whistler wave in the plasma frame, while in the second interval it can be explained as an outward ICW or inward fast-mode/whistler wave. The identification of the exact kinetic wave mode is more difficult to confirm owing to the limited plasma data resolution. The presence of ion-scale waves near the Sun suggests that ion cyclotron resonance may be one of the ubiquitous kinetic physical processes associated with small-scale magnetic fluctuations and kinetic instabilities in the inner heliosphere.

scholarly journals Non-Local Buckling Analysis of Functionally Graded Nanoporous Metal Foam Nanoplates

Coatings ◽  
2018 ◽  
Vol 8 (11) ◽  
pp. 389 ◽  
Author(s):  
Yanqing Wang ◽  
Zhiyuan Zhang
Keyword(s):  
Metal Foam ◽  
Plate Theory ◽  
Constitutive Relations ◽  
Equations Of Motion ◽  
Local Buckling ◽  
Functionally Graded ◽  
Small Scale ◽  
Refined Plate Theory ◽  
Nanoporous Metal ◽  
Non Local

In this study, the buckling of functionally graded (FG) nanoporous metal foam nanoplates is investigated by combining the refined plate theory with the non-local elasticity theory. The refined plate theory takes into account transverse shear strains which vary quadratically through the thickness without considering the shear correction factor. Based on Eringen’s non-local differential constitutive relations, the equations of motion are derived from Hamilton’s principle. The analytical solutions for the buckling of FG nanoporous metal foam nanoplates are obtained via Navier’s method. Moreover, the effects of porosity distributions, porosity coefficient, small scale parameter, axial compression ratio, mode number, aspect ratio and length-to-thickness ratio on the buckling loads are discussed. In order to verify the validity of present analysis, the analytical results have been compared with other previous studies.

scholarly journals Does eating local food reduce the environmental impact of food production and enhance consumer health?

2010 ◽  
Vol 69 (4) ◽  
pp. 582-591 ◽  
Author(s):  
Gareth Edwards-Jones
Keyword(s):  
Food System ◽  
Local Food ◽  
Local Level ◽  
Qualitative Assessment ◽  
Small Scale ◽  
Quantitative Evidence ◽  
Self Sufficiency ◽  
Non Local ◽  
The Uk ◽  
The Impact

The concept of local food has gained traction in the media, engaged consumers and offered farmers a new marketing tool. Positive claims about the benefits of local food are probably not harmful when made by small-scale producers at the local level; however, greater concern would arise should such claims be echoed in policy circles. This review examines the evidence base supporting claims about the environmental and health benefits of local food. The results do not offer any support for claims that local food is universally superior to non-local food in terms of its impact on the climate or the health of consumers. Indeed several examples are presented that demonstrate that local food can on occasions be inferior to non-local food. The analysis also considers the impact on greenhouse gas emissions of moving the UK towards self-sufficiency. Quantitative evidence is absent on the changes in overall emissions that would occur if the UK switched to self-sufficiency. A qualitative assessment suggests the emissions per item of food would probably be greater under a scenario of self-sufficiency than under the current food system. The review does not identify any generalisable or systematic benefits to the environment or human health that arise from the consumption of local food in preference to non-local food.

scholarly journals Non-linear and non-local behaviour in spontaneously electrical solids

2018 ◽  
Vol 20 (7) ◽  
pp. 5112-5116 ◽  
Author(s):  
M. Roman ◽  
S. Taj ◽  
M. Gutowski ◽  
M. R. S. McCoustra ◽  
A. C. Dunn ◽  
...  
Keyword(s):  
Electric Fields ◽  
Dipole Orientation ◽  
Local Behaviour ◽  
Non Linear ◽  
Non Local

We show that solids displaying spontaneous dipole orientation possess quite general non-local and non-linear characteristics expressed through their internal electric fields.

Thermal buckling analysis of double-walled carbon nanotubes considering the small-scale length effect

2011 ◽  
Vol 225 (1) ◽  
pp. 248-256 ◽  
Author(s):  
A Ghorbanpour Arani ◽  
M Mohammadimehr ◽  
A R Saidi ◽  
S Shogaei ◽  
A Arefmanesh
Keyword(s):  
Temperature Change ◽  
Buckling Analysis ◽  
Buckling Load ◽  
Small Scale ◽  
Buckling Mode ◽  
Critical Buckling Load ◽  
Winkler Model ◽  
Non Local ◽  
Double Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

In this article, the buckling analysis of a double-walled carbon nanotube (DWCNT) subjected to a uniform internal pressure in a thermal field is investigated. The effects of the temperature change, the surrounding elastic medium based on the Winkler model, and the van der Waals forces between the inner and the outer tubes are considered using the continuum cylindrical shell model. The small-length scale effect is also included in the present formulation. The results show that there is a unique buckling mode corresponding to each critical buckling load. Moreover, it is shown that the non-local critical buckling load is lower than the local critical buckling load. It is concluded that, at low temperatures, the critical buckling load for the infinitesimal buckling of a DWCNT increases as the magnitude of temperature change increases whereas at high temperatures, the critical buckling load decreases with the increasing of the temperature.

scholarly journals Electrostatic forces alter particle size distributions in atmospheric dust

2020 ◽  
Vol 20 (5) ◽  
pp. 3181-3190 ◽  
Author(s):  
Joseph R. Toth III ◽  
Siddharth Rajupet ◽  
Henry Squire ◽  
Blaire Volbers ◽  
Jùn Zhou ◽  
...  
Keyword(s):  
Electric Field ◽  
Size Distribution ◽  
Long Range ◽  
Electric Fields ◽  
Electrostatic Force ◽  
Small Scale ◽  
Size Distributions ◽  
Electrostatic Forces ◽  
Atmospheric Dust ◽  
Airborne Dust

Abstract. Large amounts of dust are lofted into the atmosphere from arid regions of the world before being transported up to thousands of kilometers. This atmospheric dust interacts with solar radiation and causes changes in the climate, with larger-sized particles having a heating effect, and smaller-sized particles having a cooling effect. Previous studies on the long-range transport of dust have found larger particles than expected, without a model to explain their transport. Here, we investigate the effect of electric fields on lofted airborne dust by blowing sand through a vertically oriented electric field, and characterizing the size distribution as a function of height. We also model this system, considering the gravitational, drag, and electrostatic forces on particles, to understand the effects of the electric field. Our results indicate that electric fields keep particles suspended at higher elevations and enrich the concentration of larger particles at higher elevations. We extend our model from the small-scale system to long-range atmospheric dust transport to develop insights into the effects of electric fields on size distributions of lofted dust in the atmosphere. We show that the presence of electric fields and the resulting electrostatic force on charged particles can help explain the transport of unexpectedly large particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modeling results indicate that electrostatic forces may in some cases be relevant regarding the effect of atmospheric dust on the climate.

scholarly journals Inverse Energy Cascade in Advanced MHD Turbulence (the RNG Method)

1993 ◽  
Vol 157 ◽  
pp. 255-261
Author(s):  
N. Kleeorin ◽  
I. Rogachevskii
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Magnetic Field Effect ◽  
Magnetic Reynolds Number ◽  
Energy Cascade ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
Inverse Energy Cascade ◽  
Large Scale Magnetic Field

The nonlinear (in terms of the large-scale magnetic field) effect of the modification of the magnetic force by an advanced small-scale magnetohydrodynamic (MHD) turbulence is considered. The phenomenon is due to the generation of magnetic fluctuations at the expense of hydrodynamic pulsations. It results in a decrease of the elasticity of the large-scale magnetic field.The renormalization group (RNG) method was employed for the investigation of the MHD turbulence at the large magnetic Reynolds number. It was found that the level of the magnetic fluctuations can exceed that obtained from the equipartition assumption due to the inverse energy cascade in advanced MHD turbulence.This effect can excite an instability of the large-scale magnetic field due to the energy transfer from the small-scale turbulent pulsations. This instability is an example of the inverse energy cascade in advanced MHD turbulence. It may act as a mechanism for the large-scale magnetic ropes formation in the solar convective zone and spiral galaxies.

scholarly journals On the probability distribution function of small-scale interplanetary magnetic field fluctuations

2004 ◽  
Vol 22 (10) ◽  
pp. 3751-3769 ◽  
Author(s):  
R. Bruno ◽  
V. Carbone ◽  
L. Primavera ◽  
F. Malara ◽  
L. Sorriso-Valvo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Robust Statistics ◽  
Interplanetary Space ◽  
Parametric Instability ◽  
Field Vector ◽  
Small Scale ◽  
Magnetic Fluctuations ◽  
Mhd Turbulence ◽  
The One

Abstract. In spite of a large number of papers dedicated to the study of MHD turbulence in the solar wind there are still some simple questions which have never been sufficiently addressed, such as: a) Do we really know how the magnetic field vector orientation fluctuates in space? b) What are the statistics followed by the orientation of the vector itself? c) Do the statistics change as the wind expands into the interplanetary space? A better understanding of these points can help us to better characterize the nature of interplanetary fluctuations and can provide useful hints to investigators who try to numerically simulate MHD turbulence. This work follows a recent paper presented by some of the authors which shows that these fluctuations might resemble a sort of random walk governed by Truncated Lévy Flight statistics. However, the limited statistics used in that paper did not allow for final conclusions but only speculative hypotheses. In this work we aim to address the same problem using more robust statistics which, on the one hand, forces us not to consider velocity fluctuations but, on the other hand, allows us to establish the nature of the governing statistics of magnetic fluctuations with more confidence. In addition, we show how features similar to those found in the present statistical analysis for the fast speed streams of solar wind are qualitatively recovered in numerical simulations of the parametric instability. This might offer an alternative viewpoint for interpreting the questions raised above.

Infrared Reynolds number dependency of the two-dimensional inverse energy cascade

2011 ◽  
Vol 667 ◽  
pp. 463-473 ◽  
Author(s):  
ANDREAS VALLGREN
Keyword(s):  
Reynolds Number ◽  
Cascade Range ◽  
Energy Cascade ◽  
Energy Spectra ◽  
Small Scale ◽  
Two Dimensional ◽  
Inverse Energy Cascade ◽  
Linear Friction ◽  
Non Local ◽  
Reynolds Number Dependency

High-resolution simulations of forced two-dimensional turbulence reveal that the inverse cascade range is sensitive to an infrared Reynolds number, Reα = kf/kα, where kf is the forcing wavenumber and kα is a frictional wavenumber based on linear friction. In the limit of high Reα, the classic k−5/3 scaling is lost and we obtain steeper energy spectra. The sensitivity is traced to the formation of vortices in the inverse energy cascade range. Thus, it is hypothesized that the dual limit Reα → ∞ and Reν = kd/kf → ∞, where kd is the small-scale dissipation wavenumber, will lead to a steeper energy spectrum than k−5/3 in the inverse energy cascade range. It is also found that the inverse energy cascade is maintained by non-local triad interactions.

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