MMS Multipoint electric field observations of small-scale magnetic holes

<p>Experimental work on small-scale meltwater meandering channels over ice and field observations have identified similarities and differences between their planform morphologies and those of meandering channels in other media (e.g. alluvial, bedrock). Qualitatively and quantitatively, planform characteristics, including sinuosity, wavelength-to-width ratios, coefficient of skewness and fatness, suggest that most meandering channels behave in certain ways and within certain ranges. However, what makes meltwater meandering channels over ice unique? In this contribution, I highlight the different aspects that set meltwater meandering channels over ice apart from meandering channels in other media and share ongoing work focusing in their planform morphologies, curvature signals, and cross section geometry.</p>

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Free Vibration Response of FG Porous Sandwich Micro-Beam with Flexoelectric Face-Sheets Resting on Modified Silica Aerogel Foundation

International Journal of Applied Mechanics ◽

10.1142/s175882511950087x ◽

2019 ◽

Vol 11 (09) ◽

pp. 1950087 ◽

Cited By ~ 3

Author(s):

Ali Ghorbanpour Arani ◽

Hassan Baba Akbar Zarei ◽

Pouya Pourmousa

Keyword(s):

Free Vibration ◽

Electric Field ◽

External Electric Field ◽

Silica Aerogel ◽

Free Vibration Analysis ◽

Strain Gradient Theory ◽

Small Scale ◽

Gradient Theory ◽

Dimensionless Frequency ◽

Modified Silica

The free vibration analysis of sandwich micro-beam (SMB) which is subjected to electrical field is investigated by adopting the Euler–Bernoulli beam theory (EBBT) and modified strain gradient theory (MSGT). SMB is made of three layers, including a functionally graded (FG) porous core and two flexoelectric face-sheets. The porosities are assumed to be distributed over the beam thickness based on the two distribution functions. Also, due to the electric properties of flexoelectric materials, face-sheets of SMB are subjected to the external electric field. The modified Silica Aerogel foundation model is employed to consider the effects of elastic foundation on SMB. The size-dependent governing equations of motion are derived using Hamilton’s principle and solved by Navier’s solution method for a case of simply supported SMB. The effects of various parameters, such as length to thickness ratio, porosity index, flexoelectric loadings (the load applied to the flexoelectric face-sheets caused by external electric field), small scale parameter and foundation parameters on dimensionless frequency of SMB, are assessed. The results of this work can be used for optimum design and control of micro-electro-mechanical devices.

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New ground ice maps for Canada using a paleogeographic modelling approach

The Cryosphere ◽

10.5194/tc-13-753-2019 ◽

2019 ◽

Vol 13 (3) ◽

pp. 753-773 ◽

Cited By ~ 13

Author(s):

H. Brendan O'Neill ◽

Stephen A. Wolfe ◽

Caroline Duchesne

Keyword(s):

Glacial Lake ◽

Significant Advance ◽

Small Scale ◽

Permafrost Degradation ◽

Field Observations ◽

Tree Line ◽

Ground Ice ◽

Near Surface ◽

Western Arctic ◽

Modelling Approach

Abstract. Ground ice melt caused by climate-induced permafrost degradation may trigger significant ecological change, damage infrastructure, and alter biogeochemical cycles. The fundamental ground ice mapping for Canada is now >20 years old and does not include significant new insights gained from recent field- and remote-sensing-based studies. New modelling incorporating paleogeography is presented in this paper to depict the distribution of three ground ice types (relict ice, segregated ice, and wedge ice) in northern Canada. The modelling uses an expert-system approach in a geographic information system (GIS), founded in conceptual principles gained from empirically based research, to predict ground ice abundance in near-surface permafrost. Datasets of surficial geology, deglaciation, paleovegetation, glacial lake and marine limits, and modern permafrost distribution allow representations in the models of paleoclimatic shifts, tree line migration, marine and glacial lake inundation, and terrestrial emergence, and their effect on ground ice abundance. The model outputs are generally consistent with field observations, indicating abundant relict ice in the western Arctic, where it has remained preserved since deglaciation in thick glacigenic sediments in continuous permafrost. Segregated ice is widely distributed in fine-grained deposits, occurring in the highest abundance in glacial lake and marine sediments. The modelled abundance of wedge ice largely reflects the exposure time of terrain to low air temperatures in tundra environments following deglaciation or marine/glacial lake inundation and is thus highest in the western Arctic. Holocene environmental changes result in reduced ice abundance where the tree line advanced during warmer periods. Published observations of thaw slumps and massive ice exposures, segregated ice and associated landforms, and ice wedges allow a favourable preliminary assessment of the models, and the results are generally comparable with the previous ground ice mapping for Canada. However, the model outputs are more spatially explicit and better reflect observed ground ice conditions in many regions. Synthetic modelling products that incorporated the previous ground ice information may therefore include inaccuracies. The presented modelling approach is a significant advance in permafrost mapping, but additional field observations and volumetric ice estimates from more areas in Canada are required to improve calibration and validation of small-scale ground ice modelling. The ground ice maps from this paper are available in the supplement in GeoTIFF format.

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Electrostatic forces alter particle size distributions in atmospheric dust

Atmospheric Chemistry and Physics ◽

10.5194/acp-20-3181-2020 ◽

2020 ◽

Vol 20 (5) ◽

pp. 3181-3190 ◽

Cited By ~ 1

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.

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Viking magnetic and electric field observations of Pc 1 waves at high latitudes

Journal of Geophysical Research Atmospheres ◽

10.1029/ja095ia05p05941 ◽

1990 ◽

Vol 95 (A5) ◽

pp. 5941 ◽

Cited By ~ 108

Author(s):

R. E. Erlandson ◽

L. J. Zanetti ◽

T. A. Potemra ◽

L. P. Block ◽

G. Holmgren

Keyword(s):

Electric Field ◽

Field Observations ◽

High Latitudes

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High-latitude distributions of plasma waves and spatial irregularities from DE 2 alternating current electric field observations

Journal of Geophysical Research Atmospheres ◽

10.1029/92ja01836 ◽

1993 ◽

Vol 98 (A2) ◽

pp. 1629-1652 ◽

Cited By ~ 48

Author(s):

J. P. Heppner ◽

M. C. Liebrecht ◽

N. C. Maynard ◽

R. F. Pfaff

Keyword(s):

Electric Field ◽

High Latitude ◽

Plasma Waves ◽

Alternating Current ◽

Field Observations ◽

Current Electric Field

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Electrostatic forces alter particle size distributions in atmospheric dust

10.5194/acp-2019-650 ◽

2019 ◽

Cited By ~ 1

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 causing 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 on 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 particles can help explain the transport of unexpectedly larger particles and cause the size distribution to become more uniform as a function of elevation. Thus, our experimental and modelling results indicate that electrostatic forces should be considered when determining the effect of atmospheric dust on the climate.

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