scholarly journals Development, Implementation and Testing of Algorithm to Detect Ionopause-Like Structure Using Parallel Processing in the Martian Atmosphere

2021 ◽  
Vol 9 (12) ◽  
pp. 1939-1949
Author(s):  
Masoom Jethwa
Keyword(s):  
Parallel Processing ◽  
Density Gradient ◽  
Dynamic Pressure ◽  
Martian Atmosphere ◽  
Primary Objective ◽  
Simultaneous Increase ◽  
Density Structure ◽  
Radial Magnetic Field ◽  
Martian Ionosphere ◽  
Present Algorithm

Abstract: This study assesses the Martian ionopause using MAVEN datasets between periapsis and 150-600 km. Ionopause is an abrupt reduction of the electron density with increasing altitude. It is also required to verify the simultaneous increase of the electron temperature and variability below 400 km. To address this issue, we have adopted a computational approach in determining the ionopause-like density structure of the ionospheric profile. From computing thermal & magnetic pressures, radial magnetic field components, ionopause-like density gradient are detected and stored. The ionopause (theoretically) is formed where the total ionospheric pressure equals solar wind dynamic pressure. The present algorithm consists of a comprehensive set of conditions to be performed on the dataset sequentially. These include datasets from various instruments simultaneously observed. The primary objective of the present study is to describe the implementation and testing of this algorithm for big datasets of the Martian ionosphere and extract ionopause-like density gradient using automation. Keywords: Ionopause, Mars, Remote sensing, MAVEN dataset, Parallel-processing

scholarly journals Torsional waves driven by convection and jets in Earth’s liquid core

2018 ◽  
Vol 216 (1) ◽  
pp. 123-129 ◽  
Author(s):  
R J Teed ◽  
C A Jones ◽  
S M Tobias
Keyword(s):  
Magnetic Field ◽  
Density Gradient ◽  
Inner Core ◽  
Liquid Core ◽  
Outer Core ◽  
Dynamo Action ◽  
Radial Magnetic Field ◽  
Torsional Waves ◽  
Plausible Mechanism ◽  
Rich Liquid

SUMMARY Turbulence and waves in Earth’s iron-rich liquid outer core are believed to be responsible for the generation of the geomagnetic field via dynamo action. When waves break upon the mantle they cause a shift in the rotation rate of Earth’s solid exterior and contribute to variations in the length-of-day on a ∼6-yr timescale. Though the outer core cannot be probed by direct observation, such torsional waves are believed to propagate along Earth’s radial magnetic field, but as yet no self-consistent mechanism for their generation has been determined. Here we provide evidence of a realistic physical excitation mechanism for torsional waves observed in numerical simulations. We find that inefficient convection above and below the solid inner core traps buoyant fluid forming a density gradient between pole and equator, similar to that observed in Earth’s atmosphere. Consequently, a shearing jet stream—a ‘thermal wind’—is formed near the inner core; evidence of such a jet has recently been found. Owing to the sharp density gradient and influence of magnetic field, convection at this location is able to operate with the turnover frequency required to generate waves. Amplified by the jet it then triggers a train of oscillations. Our results demonstrate a plausible mechanism for generating torsional waves under Earth-like conditions and thus further cement their importance for Earth’s core dynamics.

scholarly journals On the response of ionospheric electrojets to solar wind discontinuities

2009 ◽  
Vol 27 (10) ◽  
pp. 3791-3803 ◽  
Author(s):  
M. Palmroth ◽  
T. I. Pulkkinen ◽  
J. Polvi ◽  
A. Viljanen ◽  
P. Janhunen
Keyword(s):  
Solar Wind ◽  
Dynamic Pressure ◽  
Pressure Change ◽  
Solar Wind Dynamic Pressure ◽  
Simultaneous Increase ◽  
Sudden Increase ◽  
Step Size ◽  
Ionospheric Response ◽  
Superposed Epoch Analysis ◽  
The Imf

Abstract. We investigate the ionospheric response to solar wind discontinuities as detected by the IE index computed from IMAGE ground magnetometers. The solar wind discontinuities include both sudden increases as well as decreases of the solar wind dynamic pressure, recorded by the SWEPAM instrument of the ACE spacecraft during the period 1998–2004. In our statistical study, we identify four categories of events: 1) sudden increases of the dynamic pressure with a simultaneous increase of the interplanetary magnetic field (IMF) magnitude; 2) sudden increases of the dynamic pressure accompanied with a simultaneous decrease of the IMF; 3) sudden decreases of the dynamic pressure accompanied with a sudden increase of the IMF; and 4) sudden decreases of the dynamic pressure with relatively steady IMF. We perform a superposed epoch analysis for the four event categories to distinguish the ionospheric response. We find that the IE index increases/decreases in response to the solar wind dynamic pressure increases/decreases regardless of the simultaneous change in the IMF or the amount of estimated input energy. We investigate the magnitude of the ionospheric response according to the IMF north-south direction, the dynamic pressure step size as well as the pressure level prior the dynamic pressure change. We find that the ionospheric result is augmented for larger pressure steps, while the prior IMF has a role only in some of the event categories. We also perform global MHD simulation runs to investigate the ionospheric dissipation rate during such solar wind discontinuities, and find that the simulation results are in good qualitative accordance with the observational statistical results.

scholarly journals A case study of a density structure over a vertical magnetic field region in the Martian ionosphere

2016 ◽  
Vol 43 (10) ◽  
pp. 4665-4672 ◽  
Author(s):  
F. Duru ◽  
D. A. Gurnett ◽  
C. Diéval ◽  
D. D. Morgan ◽  
D. Pisa ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Region ◽  
Density Structure ◽  
Vertical Magnetic Field ◽  
Martian Ionosphere ◽  
Magnetic Field Region

scholarly journals Correlation between Transit-Oriented Development (TOD), Land Use Catchment Areas, and Local Environmental Transformation

2018 ◽  
Vol 10 (12) ◽  
pp. 4622 ◽  
Author(s):  
Xin Tong ◽  
Yaowu Wang ◽  
Edwin H. W. Chan ◽  
Qingfeng Zhou
Keyword(s):  
Land Use ◽  
Density Gradient ◽  
Catchment Area ◽  
Primary Objective ◽  
Transit Oriented Development ◽  
Negative Exponential Function ◽  
Future Design ◽  
Catchment Areas ◽  
Negative Exponential ◽  
The Impact

Transit-oriented development (TOD) has been recognised as a sustainable planning approach and that is typically designed for a whole city. Individual land use characteristics and the causations have often been ignored. Therefore, the primary objective of this study was to explore the factors that influence the land use catchment area (LCA) characteristics at a station neighborhood level. First, it contributes a methodology to measure the LCA by introducing a new concept. The density gradient was introduced to generate the scale and compactness degree of each station. Second, it provides a theoretical framework for understanding the causes of different LCAs. The partial least squares (PLS) regression model was employed to explore the accessibility effects. By analysing density gradient curves, it reveals that stations grew to fit the negative exponential function. Regarding the scale and form degree of LCAs, the impact of accessibility before and after a station construction have been corroborated. Moreover, the effects of facilities function before construction, distance from main roads, and elevated stations have been emphasized. The results provide support for a more sophisticated concept of catchment area relating to land use at the level of an individual TOD station, while shedding light on the benefits of those engaged in the future design of TOD with due consideration of the local physical environments.

scholarly journals A limitation on Long's model in stratified fluid flows

1971 ◽  
Vol 48 (1) ◽  
pp. 161-179 ◽  
Author(s):  
Harvey Segur
Keyword(s):  
Froude Number ◽  
Barrier Height ◽  
Density Gradient ◽  
Dynamic Pressure ◽  
Fluid Flows ◽  
Critical Value ◽  
Stratified Fluid ◽  
Lee Wave ◽  
Finite Barrier ◽  
Internal Froude Number

The flow of a continuously stratified fluid into a contraction is examined, under the assumptions that the dynamic pressure and the density gradient are constant upstream (Long's model). It is shown that a solution to the equations exists if and only if the strength of the contraction does not exceed a certain critical value which depends on the internal Froude number. For the flow of a stratified fluid over a finite barrier in a channel, it is further shown that, if the barrier height exceeds this same critical value, lee-wave amplitudes increase without bound as the length of the barrier increases. The breakdown of the model, as implied by these arbitrarily large amplitudes, is discussed. The criterion is compared with available experimental results for both geometries.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

Uranyl Acetate and Rotary Shadowing to Increase the Contrast of Small Aggregated Virus Particles

1969 ◽  
Vol 27 ◽  
pp. 424-425
Author(s):  
Lee F. Ellis ◽  
Richard M. Van Frank ◽  
Walter J. Kleinschmidt
Keyword(s):  
Electron Microscopy ◽  
Tissue Culture ◽  
Density Gradient ◽  
Density Gradient Centrifugation ◽  
Gradient Centrifugation ◽  
Uranyl Acetate ◽  
Interferon Inducer ◽  
Virus Particles ◽  
Staining Methods ◽  
Rotary Shadowing

The extract from Penicillum stoliniferum, known as statolon, has been purified by density gradient centrifugation. These centrifuge fractions contained virus particles that are an interferon inducer in mice or in tissue culture. Highly purified preparations of these particles are difficult to enumerate by electron microscopy because of aggregation. Therefore a study of staining methods was undertaken.

Electron Microscopic Characterization and Quantitation of Air Borne Particulate Matter with Special Emphasis on Asbestos

1972 ◽  
Vol 30 ◽  
pp. 356-357
Author(s):  
Peter K. Mueller ◽  
Glenn R. Smith ◽  
Leslie M Carpenter ◽  
Ronald L. Stanley
Keyword(s):  
Electron Microscopy ◽  
Light And Electron Microscopy ◽  
Ambient Air ◽  
Quality Standard ◽  
Primary Objective ◽  
Cellulose Ester ◽  
Main Concept ◽  
Electron Microscopic ◽  
Air Samples ◽  
Diffraction Patterns

At the present time the primary objective of the electron microscopy group of the Air and Industrial Hygiene Laboratory is the development of a method suitable for use in establishing an air quality standard for asbestos in ambient air and for use in its surveillance. The main concept and thrust of our approach for the development of this method is to obtain a true picture of fiber occurrence as a function of particle size and asbestos type utilizing light and electron microscopy.We have now available an electron micrographic atlas of all asbestos types including selected area diffraction patterns and examples of fibers isolated from air samples. Several alternative approaches for measuring asbestos in ambient air have been developed and/or evaluated. Our experiences in this regard will be described. The most promising method involves: 1) taking air samples on cellulose ester membrane filters with a nominal pore size of 0.8 micron; 2) ashing in a low temperature oxygen plasma for several hours;

Ultrasturcture of cerebellar cells and neuropil in rats subjected to partial global cerebral ischemia

1986 ◽  
Vol 44 ◽  
pp. 126-127
Author(s):  
R.V.W. Dimlich ◽  
M.H. Biros
Keyword(s):  
Purkinje Cells ◽  
Glial Cells ◽  
Granule Cells ◽  
Molecular Layer ◽  
Cell Types ◽  
Primary Objective ◽  
Global Cerebral Ischemia ◽  
Forebrain Ischemia ◽  
Substantial Evidence ◽  
Cerebellar Cells

Although a previous study in this laboratory determined that Purkinje cells of the rat cerebellum did not appear to be damaged following 30 min of forebrain ischemia followed by 30 min of reperfusion, it was suggested that an increase in rough endoplasmic reticulum (RER) and/or polysomes had occurred in these cells. The primary objective of the present study was to morphometrically determine whether or not this increase had occurred. In addition, since there is substantial evidence that glial cells may be affected by ischemia earlier than other cell types, glial cells also were examined. To ascertain possible effects on other cerebellar components, granule cells and neuropil near Purkinje cells as well as neuropil in the molecular layer also were evaluated in this investigation.

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