Structure function analysis of plasma density fluctuations during total loss of lock of GPS signal events

2020 ◽  
Author(s):  
Hossein Ghadjari ◽  
David Knudsen ◽  
Susan Skone
Keyword(s):  
Structure Function ◽  
Plasma Density ◽  
Large Scale ◽  
Function Analysis ◽  
Density Fluctuations ◽  
Total Loss ◽  
Small Scale ◽  
Self Similarity ◽  
Radio Signals ◽  
Swarm Mission

<p>Ionospheric irregularities are fluctuations or structures of plasma density that affect the propagation of radio signals. Whenever large-scale irregularities break up into meso and small-scale irregularities, these processes become similar to a turbulence cascade. In order to have a better comparison between this and plasma density irregularities, we study different orders of structure functions of plasma density of total loss of lock events measured with the faceplate measurements of plasma density and the GPS measurements from the Swarm mission. Total loss of lock of GPS signal is a physical proxy for severe degradation of GPS signals. In addition to different orders of structure-function, we study the existence of self-similarity or multifractality of plasma density of total loss of lock events to investigate any possible intermittent fluctuations. </p>

scholarly journals On the short-term variability of turbulence and temperature in the winter mesosphere

2018 ◽  
Vol 36 (4) ◽  
pp. 1099-1116
Author(s):  
Gerald A. Lehmacher ◽  
Miguel F. Larsen ◽  
Richard L. Collins ◽  
Aroh Barjatya ◽  
Boris Strelnikov
Keyword(s):  
Attitude Control ◽  
Large Scale ◽  
Lower Thermosphere ◽  
Density Fluctuations ◽  
Large Temperature ◽  
Small Scale ◽  
Spatial And Temporal Variability ◽  
Temperature Structure ◽  
Wind Shears

Abstract. Four mesosphere–lower thermosphere temperature and turbulence profiles were obtained in situ within ∼30 min and over an area of about 100 by 100 km during a sounding rocket experiment conducted on 26 January 2015 at Poker Flat Research Range in Alaska. In this paper we examine the spatial and temporal variability of mesospheric turbulence in relationship to the static stability of the background atmosphere. Using active payload attitude control, neutral density fluctuations, a tracer for turbulence, were observed with very little interference from the payload spin motion, and with high precision (<0.01 %) at sub-meter resolution. The large-scale vertical temperature structure was very consistent between the four soundings. The mesosphere was almost isothermal, which means more stratified, between 60 and 80 km, and again between 88 and 95 km. The stratified regions adjoined quasi-adiabatic regions assumed to be well mixed. Additional evidence of vertical transport and convective activity comes from sodium densities and trimethyl aluminum trail development, respectively, which were both observed simultaneously with the in situ measurements. We found considerable kilometer-scale temperature variability with amplitudes of 20 K in the stratified region below 80 km. Several thin turbulent layers were embedded in this region, differing in width and altitude for each profile. Energy dissipation rates varied between 0.1 and 10 mW kg−1, which is typical for the winter mesosphere. Very little turbulence was observed above 82 km, consistent with very weak small-scale gravity wave activity in the upper mesosphere during the launch night. On the other hand, above the cold and prominent mesopause at 102 km, large temperature excursions of +40 to +70 K were observed. Simultaneous wind measurements revealed extreme wind shears near 108 km, and combined with the observed temperature gradient, isolated regions of unstable Richardson numbers (0<Ri<0.25) were detected in the lower thermosphere. The experiment was launched into a bright auroral arc under moderately disturbed conditions (Kp∼5).

Ring structure in the poleward boundary current off Western Australia in Summer

1983 ◽  
Vol 34 (4) ◽  
pp. 547 ◽  
Author(s):  
JC Andrews
Keyword(s):  
Structure Function ◽  
Western Australia ◽  
Large Scale ◽  
Function Analysis ◽  
Ring Structure ◽  
Boundary Current ◽  
Length Scales ◽  
Leeuwin Current ◽  
Tropical Water ◽  
Geopotential Anomaly

Data from five summer cruises off Western Australia are examined objectively using structure functions to establish principal length scales and amplitudes of mesoscale fields. Previous estimates of length scales using geopotential anomaly and geomagnetic electrokinetograph vectors as inputs to structure- function analyses gave length scales that differed by a factor of two. The present analysis shows that there are two length scales, which dominate in different parts of the flow, and this reconciles the two previous estimates. The shorter scale is λs = 157�25 km and the longer is λL = 309�28 km. Regions of strong large-scale currents have warm- and cold-core rings and mesoscale waves associated with them that assume the Rossby deformation scale. These are the λS structures. The longer, λL structures are found in regions of weak large-scale currents. Geopotential anomaly amplitudes and currents in the rings are, respectively, about 0.7 m2 s-2 (geopotential relief = 1 4 m2 s-1) and 70 cm s-1. Data from one summer cruise with a station density of approximately 12 per degree square are analysed in detail subjectively and the structure-function analysis is shown to be quantitatively meaningful. This cruise was near the shelf and shows the advection of low-salinity tropical water poleward over the slope in a narrow baroclinic current. Seaward cyclonic rings were associated with the current. The baroclinic structure of the current and of the rings is compatible with the winter behaviour of Lagrangian drifters released into the Leeuwin Current.

Collective backscattering of gyrotron radiation by small-scale plasma density fluctuations in large helical device

2008 ◽  
Vol 79 (10) ◽  
pp. 10E721 ◽  
Author(s):  
Nikolay Kharchev ◽  
Kenji Tanaka ◽  
Shin Kubo ◽  
Hiroe Igami ◽  
German Batanov ◽  
...  
Keyword(s):  
Plasma Density ◽  
Density Fluctuations ◽  
Small Scale

scholarly journals Characterization of VHF radar observations associated with equatorial Spread F by narrow-band optical measurements

2004 ◽  
Vol 22 (9) ◽  
pp. 3129-3136 ◽  
Author(s):  
R. Sekar ◽  
D. Chakrabarty ◽  
R. Narayanan ◽  
S. Sripathi ◽  
A. K. Patra ◽  
...  
Keyword(s):  
Large Scale ◽  
Temporal Variations ◽  
Density Fluctuations ◽  
Optical Measurements ◽  
Small Scale ◽  
Upward Movement ◽  
Vhf Radar ◽  
Equatorial Spread F ◽  
Spread F ◽  
Airglow Intensity

Abstract. The VHF radars have been extensively used to investigate the structures and dynamics of equatorial Spread F (ESF) irregularities. However, unambiguous identification of the nature of the structures in terms of plasma depletion or enhancement requires another technique, as the return echo measured by VHF radar is proportional to the square of the electron density fluctuations. In order to address this issue, co-ordinated radar backscatter and thermospheric airglow intensity measurements were carried out during March 2003 from the MST radar site at Gadanki. Temporal variations of 630.0-nm and 777.4-nm emission intensities reveal small-scale ("micro") and large-scale ("macro") variations during the period of observation. The micro variations are absent on non-ESF nights while the macro variations are present on both ESF and non-ESF nights. In addition to the well-known anti-correlation between the base height of the F-region and the nocturnal variation of thermospheric airglow intensities, the variation of the base height of the F-layer, on occasion, is found to manifest as a bottomside wave-like structure, as seen by VHF radar on an ESF night. The micro variations in the airglow intensities are associated with large-scale irregular plasma structures and found to be in correspondence with the "plume" structures obtained by VHF radar. In addition to the commonly observed depletions with upward movement, the observation unequivocally reveals the presence of plasma enhancements which move downwards. The observation of enhancement in 777.4-nm airglow intensity, which is characterized as plasma enhancement, provides an experimental verification of the earlier prediction based on numerical modeling studies.

scholarly journals Statistics of Heat Transfer in Two-Dimensional Turbulent Rayleigh-Bénard Convection at Various Prandtl Number

Entropy ◽  
2018 ◽  
Vol 20 (8) ◽  
pp. 582 ◽  
Author(s):  
Hui Yang ◽  
Yikun Wei ◽  
Zuchao Zhu ◽  
Huashu Dou ◽  
Yuehong Qian
Keyword(s):  
Heat Transfer ◽  
Structure Function ◽  
Dissipation Rate ◽  
Large Scale ◽  
Thermal Dissipation ◽  
Small Scale ◽  
Linear Scaling ◽  
Two Dimensional ◽  
Large Scale Circulation ◽  
Rayleigh Benard

Statistics of heat transfer in two-dimensional (2D) turbulent Rayleigh-Bénard (RB) convection for Pr=6,20,100 and 106 are investigated using the lattice Boltzmann method (LBM). Our results reveal that the large scale circulation is gradually broken up into small scale structures plumes with the increase of Pr, the large scale circulation disappears with increasing Pr, and a great deal of smaller thermal plumes vertically rise and fall from the bottom to top walls. It is further indicated that vertical motion of various plumes gradually plays main role with increasing Pr. In addition, our analysis also shows that the thermal dissipation is distributed mainly in the position of high temperature gradient, the thermal dissipation rate εθ already increasingly plays a dominant position in the thermal transport, εu can have no effect with increase of Pr. The kinematic viscosity dissipation rate and the thermal dissipation rate gradually decrease with increasing Pr. The energy spectrum significantly decreases with the increase of Pr. A scope of linear scaling arises in the second order velocity structure functions, the temperature structure function and mixed structure function(temperature-velocity). The value of linear scaling and the 2nd-order velocity decrease with increasing Pr, which is qualitatively consistent with the theoretical predictions.

scholarly journals Large-Scale Structure –Function Analysis of the Arabidopsis RPM1 Disease Resistance Protein

2002 ◽  
Vol 14 (2) ◽  
pp. 435-450 ◽  
Author(s):  
Pablo Tornero ◽  
Ryon A. Chao ◽  
William N. Luthin ◽  
Stephen A. Goff ◽  
Jeffery L. Dangl
Keyword(s):  
Disease Resistance ◽  
Structure Function ◽  
Large Scale ◽  
Function Analysis ◽  
Large Scale Structure ◽  
Scale Structure ◽  
Disease Resistance Protein ◽  
Resistance Protein

scholarly journals Interaction of Upper-Tropospheric Turbulence and Gravity Waves as Obtained from Spectral and Structure Function Analyses

2008 ◽  
Vol 65 (8) ◽  
pp. 2676-2690 ◽  
Author(s):  
Chungu Lu ◽  
Steven E. Koch
Keyword(s):  
Structure Function ◽  
Gravity Waves ◽  
Function Analysis ◽  
Power Spectra ◽  
Physical Space ◽  
Energy Cascade ◽  
Small Scale ◽  
Order Structure ◽  
Scale Interactions ◽  
Inverse Energy Cascade

Abstract Spectral and structure function analyses of horizontal velocity fields observed in the upper troposphere and lower stratosphere during the Severe Clear Air Turbulence Collides with Air Traffic (SCATCAT) field program, conducted over the Pacific, were carried out in an effort to identify the scale interactions of turbulence and small-scale gravity waves. Because of the intermittent nature of turbulence, these analyses were conducted by clearly separating out the cases when turbulence did or did not occur in the data. In the presence of turbulence, transitional power spectra from k−2 to k−5/3 were found to be associated with gravity waves and turbulence, respectively. The second-order structure function analysis was able to translate these spectral slopes into r and r 2/3 scaling, consistent with the Monin and Yaglom conversion law, in physical space, which presented clearer pictures of scale interactions between turbulence and gravity waves. The third-order structure function analysis indicated the existence of a narrow region of inverse energy cascade from the scales of turbulence up to the gravity waves scales. This inverse energy cascade region was linked to the occurrence of Kelvin–Helmholtz instability and other wave-amplifying mechanisms, which were conjectured to lead to the breaking of small-scale gravity waves and the ensuing generation of turbulence. The multifractal analyses revealed further scale breaks between gravity waves and turbulence. The roughness and intermittent properties were also calculated for turbulence and gravity waves, respectively. Based on these properties, turbulence and gravity waves in a bifractal parameter space were mapped. In this way, their physical and statistical attributes were clearly manifested and understood.

scholarly journals Spatial structure of auroral day-time ionospheric electron density irregularities generated by a powerful HF-wave

1998 ◽  
Vol 16 (7) ◽  
pp. 812-820 ◽  
Author(s):  
E. D. Tereshchenko ◽  
B. Z. Khudukon ◽  
M. T. Rietveld ◽  
A. Brekke
Keyword(s):  
Statistical Analysis ◽  
Radio Wave ◽  
Electron Density ◽  
Large Scale ◽  
Density Fluctuations ◽  
Small Scale ◽  
Ionospheric Heating ◽  
Mean Values ◽  
Hf Wave ◽  
Electron Density Irregularities

Abstract. We describe an experiment in satellite radio-wave probing of the ionosphere, modified by powerful waves from the HF heating facility at Tromsø (Norway) in May 1995. Amplitude scintillations and variations of the phase of VHF signals from Russian navigational satellites passing over the heated region were observed. We show that both large-scale electron density irregularities (several tens of kilometers in size) and small-scale ones (from hundreds of meters to kilometers) can be generated by the HF radiation. Maximum effects caused by small-scale irregularities detected in the satellite signals are observed in the directions sector approximately parallel to the geomagnetic field lines although large-scale structures can be detected within a much larger area. The properties of small-scale irregularities (electron density fluctuations) are investigated by applying a statistical analysis and by studying experimental and model mean values of the logarithm of the relative amplitude of the signal. The results indicate that satellite radio probing can be a supporting diagnostic technique for ionospheric heating and add valuable information to studies of effects produced by HF modification.Key words. Satellite radio-wave probing · HF radiation · Electron density irregularities · Statistical analysis · Ionospheric heating

SAMPLE VARIANCE IN LARGE-SCALE COSMIC MICROWAVE BACKGROUND ANISOTROPY MEASUREMENTS

1998 ◽  
Vol 07 (01) ◽  
pp. 89-96 ◽  
Author(s):  
KIN-WANG NG
Keyword(s):  
Correlation Function ◽  
Cosmic Microwave Background ◽  
Large Scale ◽  
Large Angle ◽  
Density Fluctuations ◽  
Sample Variance ◽  
Small Scale ◽  
Microwave Background ◽  
Cosmic Microwave Background Anisotropy ◽  
Computationally Intensive

The effects of limited sky coverage in large-angle cosmic microwave background anisotropy experiments are investigated by computing the variance of the angular two-point correlation function with an incomplete sphere. We find that, assuming a power spectrum of density fluctuations with spectral index n = 1, the Galactic cut of half-width 20° (40°) about the Equator made by the COBE DMR experiment would induce a sample variance on the rms temperature fluctuation [(ΔT/T) rms ]2 (or equivalently, the correlation function at zero lag), which is 12% (38%) greater than the cosmic variance with a whole sky coverage. This result is about two times smaller than the naive expectation that the cosmic variance is enhanced by a factor of [Formula: see text], where A is the solid angle sampled by the experiment. We also find that the sample variance of the correlation function at nonzero lag can approach the cosmic variance limit. Our approach provides an analytic way of finding a theoretical error to the theoretical prediction for a particular experiment (either large- or small-scale), without having recourse to computationally intensive Monte Carlo or maximum likelihood methods.

scholarly journals Rapid structure-function insights via hairpin-centric analysis of big RNA structure probing datasets

2021 ◽  
Vol 3 (3) ◽  
Author(s):  
Pierce Radecki ◽  
Rahul Uppuluri ◽  
Sharon Aviran
Keyword(s):  
Structure Function ◽  
Rna Structure ◽  
Large Scale ◽  
Learning Algorithm ◽  
Function Analysis ◽  
Standard Data ◽  
Cellular Processes ◽  
Structure Probing ◽  
Rna Biology ◽  
Rapid Processing

Abstract The functions of RNA are often tied to its structure, hence analyzing structure is of significant interest when studying cellular processes. Recently, large-scale structure probing (SP) studies have enabled assessment of global structure-function relationships via standard data summarizations or local folding. Here, we approach structure quantification from a hairpin-centric perspective where putative hairpins are identified in SP datasets and used as a means to capture local structural effects. This has the advantage of rapid processing of big (e.g. transcriptome-wide) data as RNA folding is circumvented, yet it captures more information than simple data summarizations. We reformulate a statistical learning algorithm we previously developed to significantly improve precision of hairpin detection, then introduce a novel nucleotide-wise measure, termed the hairpin-derived structure level (HDSL), which captures local structuredness by accounting for the presence of likely hairpin elements. Applying HDSL to data from recent studies recapitulates, strengthens and expands on their findings which were obtained by more comprehensive folding algorithms, yet our analyses are orders of magnitude faster. These results demonstrate that hairpin detection is a promising avenue for global and rapid structure-function analysis, furthering our understanding of RNA biology and the principal features which drive biological insights from SP data.

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