Ice giant magnetospheres

The ice giant planets provide some of the most interesting natural laboratories for studying the influence of large obliquities, rapid rotation, highly asymmetric magnetic fields and wide-ranging Alfvénic and sonic Mach numbers on magnetospheric processes. The geometries of the solar wind–magnetosphere interaction at the ice giants vary dramatically on diurnal timescales due to the large tilt of the magnetic axis relative to each planet's rotational axis and the apparent off-centred nature of the magnetic field. There is also a seasonal effect on this interaction geometry due to the large obliquity of each planet (especially Uranus). With in situ observations at Uranus and Neptune limited to a single encounter by the Voyager 2 spacecraft, a growing number of analytical and numerical models have been put forward to characterize these unique magnetospheres and test hypotheses related to the magnetic structures and the distribution of plasma observed. Yet many questions regarding magnetospheric structure and dynamics, magnetospheric coupling to the ionosphere and atmosphere, and potential interactions with orbiting satellites remain unanswered. Continuing to study and explore ice giant magnetospheres is important for comparative planetology as they represent critical benchmarks on a broad spectrum of planetary magnetospheric interactions, and provide insight beyond the scope of our own Solar System with implications for exoplanet magnetospheres and magnetic reversals. This article is part of a discussion meeting issue ‘Future exploration of ice giant systems'.

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THEMIS observation of a substorm event on 04:35, 22 February 2008

Annales Geophysicae ◽

10.5194/angeo-27-1831-2009 ◽

2009 ◽

Vol 27 (5) ◽

pp. 1831-1841 ◽

Cited By ~ 13

Author(s):

J. Liu ◽

V. Angelopoulos ◽

H. Frey ◽

J. McFadden ◽

D. Larson ◽

...

Keyword(s):

Timing Analysis ◽

Magnetic Structures ◽

Current Disruption ◽

Reconnection Region ◽

Pi2 Pulsations ◽

Magnetic Pulsations ◽

Visual Onset ◽

The Magnetic Field ◽

Auroral Expansion

Abstract. We report on THEMIS in-situ and ground-based observations during a substorm between 04:30~04:50 UT on 22 February 2008. The spacecraft (probes) were aligned along the tail between XGSM=−5 RE to −25 RE. The most distant probe P1 (X=−24.5 RE) detected two successive tailward moving bipolar magnetic structures. P2 (X=−18 RE), P3 (X=−11 RE), P4 (X=−10.5 RE) all captured signatures related to the Earthward movement of a magnetic structure. THEMIS ground stations and all-sky imagers also recorded Pi2 pulsations and a sudden brightening in a white-light auroral imager followed by poleward expansion. We perform a detailed timing analysis of probe and ground-based data and reconstruct the time sequence of phenomena during this substorm. The earliest sign of substorm onset was the bipolar perturbation in the northward component of the magnetic field (interpreted as the result of reconnection onset) at P1 at 04:35:16 UT and corresponding magnetic perturbation at P2 at 04:35:14 UT. Auroral onset was seen at or before 04:36:55 UT, consistent with the visual onset of high-latitude magnetic pulsations at around that time. Earthward flows at P3 and P4 seen at ~04:36:03 UT, and dipolarization onset at ~04:36:50 UT, were observed at almost the same time as the ground onset signature, implying that near-Earth dipolarization happened in the aftermath of tail reconnection but not significantly ahead of the auroral intensification. Reconnection in the tail preceded ground onset and near-Earth dipolarization (current disruption) by ~2 min. Two reconnection pulses (the first one weaker than the second one) accompanied by correlative increases of cumulative magnetic flux transfer into the reconnection region were observed. A direct association of the reconnection pulses with two auroral intensifications can be made, suggesting that tail reconnection, like the auroral expansion, advances in steps rather than continuously.

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Synergistic Probe-Orbiter Science and Measurements for Understanding the Formation and Evolution of the Icy Giant Planets

10.5194/egusphere-egu2020-2232 ◽

2020 ◽

Author(s):

Sushil K. Atreya ◽

Olivier Mousis ◽

Kim R. Reh

Keyword(s):

Noble Gases ◽

Giant Planets ◽

Heavy Elements ◽

Critical Set ◽

Mixing Ratios ◽

Formation And Evolution ◽

Galileo Probe ◽

The Magnetic Field

The Galileo Probe was designed to measure the abundances of the heavy elements (mass >helium) and helium in Jupiter since they are key to understanding the planet&#8217;s formation and heat balance. Broadly speaking, the same formation scenarios presumably apply also to the Icy Giant Planets (IGP), Uranus and Neptune, so the determination of their heavy elements and He is equally important. We will show that the bulk of C, N, S, and O are sequestered in condensible volatiles whose well-mixed regions in the atmospheres of the IGP&#8217;s are extremely deep compared to Jupiter. That poses formidable challenges to their direct in situ measurements. On the other hand, being non-condensible and chemically inert, the noble gases &#8722; He, Ne, Ar, Kr and Xe &#8211; are expected to be uniformly mixed all over the planet, unlike the condensibles whose distribution is governed by dynamics, convection and purported deep oceans. Thus the noble gases would provide the most critical set of data for constraining the IGP formation models. Although the noble gases should be well-mixed everywhere below the homopause, measurements at and below the 1-bar level are needed considering their low mixing ratios, except for He. That depth also gets around any potential cold trapping of the heavy noble gases at the tropopause or adsorption on methane ice aerosols. Entry probes deployed to relatively shallow pressure levels of 5-10 bars would allow a robust determination of the abundances and isotopic ratios of the noble gases, amongst other things. A measurement of CO from orbit, along with other disequilibrium species has the potential of estimating the O/H ratio.&#160;Microwave radiometry from orbiter and the Earth have the potential of measuring the depth profiles of NH3 and H2O, which would be important for understanding the atmospheric dynamics and weather in the deep atmosphere. Combined with the above data and the data on the interior and the magnetic field, the probe results on the noble gases would provide essential constraints to the formation, migration and evolution models of the Icy Giant Planets.&#160;

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In Situ exploration of the giant planets

Experimental Astronomy ◽

10.1007/s10686-021-09775-z ◽

2021 ◽

Author(s):

O. Mousis ◽

D. H. Atkinson ◽

R. Ambrosi ◽

S. Atreya ◽

D. Banfield ◽

...

Keyword(s):

Solar System ◽

Giant Planets ◽

Atmospheric Composition ◽

Formation History ◽

History Of ◽

Composition Structure ◽

Galileo Probe ◽

Probe Measurements

AbstractRemote sensing observations suffer significant limitations when used to study the bulk atmospheric composition of the giant planets of our Solar System. This impacts our knowledge of the formation of these planets and the physics of their atmospheres. A remarkable example of the superiority of in situ probe measurements was illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases’ abundances and the precise measurement of the helium mixing ratio were only made available through in situ measurements by the Galileo probe. Here we describe the main scientific goals to be addressed by the future in situ exploration of Saturn, Uranus, and Neptune, placing the Galileo probe exploration of Jupiter in a broader context. An atmospheric entry probe targeting the 10-bar level would yield insight into two broad themes: i) the formation history of the giant planets and that of the Solar System, and ii) the processes at play in planetary atmospheres. The probe would descend under parachute to measure composition, structure, and dynamics, with data returned to Earth using a Carrier Relay Spacecraft as a relay station. An atmospheric probe could represent a significant ESA contribution to a future NASA New Frontiers or flagship mission to be launched toward Saturn, Uranus, and/or Neptune.

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Sub-Level Stoping in an Underground Limestone Quarry: An Analysis of the State of Stress in an Evolutionary Scenario

Archives of Mining Sciences ◽

10.1515/amsc-2016-0015 ◽

2016 ◽

Vol 61 (1) ◽

pp. 199-216 ◽

Cited By ~ 1

Author(s):

Marilena Cardu ◽

Sergio Dipietromaria ◽

Pierpaolo Oreste

Keyword(s):

Numerical Models ◽

The State ◽

In Situ Tests ◽

Future Scenario ◽

Limestone Quarry ◽

Geomechanical Properties ◽

State Of Stress ◽

Upper Level ◽

Pillar Structure

Abstract The aim of this study was to evaluate the state of stress of a „voids-pillar“ structure excavated by means of the sub-level stoping method in an underground limestone quarry near Bergamo (Italy). Both the current structure of the quarry (i.e. the rooms exploited till now) and a possible future scenario were analysed using the (FDM) FLAC 2D code. The quarry has been in operation since 1927; at present, exploitation is carried out underground via the sub-level stoping method. Exploitation involves two levels, with 5 rooms on the upper level and 9 rooms on the lower level. After analysing data obtained from laboratory and in situ tests carried out on rock samples and natural discontinuities, the geomechanical properties of the medium, knowledge of which is essential in order to establish the parameters that must be included in the numerical model, were evaluated. The implementation of three numerical models made it possible to study both the present conditions of quarry exploitation and the evolution of the exploited rooms, as well as a possible expansion involving a third level of rooms. Using the results obtained regarding the stress-strain present in the pillars, a potential change in room geometry was proposed aimed at reducing the stress state inside the pillars, decreasing plasticity and increasing overall quarry safety.

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Analysis of TBM Tunnel Behavior in Jointed Rock Mass

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.90-93.2033 ◽

2011 ◽

Vol 90-93 ◽

pp. 2033-2036 ◽

Cited By ~ 1

Author(s):

Jin Shan Sun ◽

Hong Jun Guo ◽

Wen Bo Lu ◽

Qing Hui Jiang

Keyword(s):

Rock Mass ◽

Numerical Models ◽

Jointed Rock ◽

In Situ Stress ◽

Jointed Rock Mass ◽

Joint Orientation ◽

Joint Spacing ◽

Factors Affecting ◽

Dip Angle

The factors affecting the TBM tunnel behavior in jointed rock mass is investigated. In the numerical models the concrete segment lining of TBM tunnel is concerned, which is simulated as a tube neglecting the segment joint. And the TBM tunnel construction process is simulate considering the excavation and installing of the segment linings. Some cases are analyzed with different joint orientation, joint spacing, joint strength and tunnel depth. The results show that the shape and areas of loosing zones of the tunnel are influenced by the parameters of joint sets and in-situ stress significantly, such as dip angle, spacing, strength, and the in-situ stress statement. And the stress and deformation of the tunnel lining are influenced by the parameters of joint sets and in-situ stress, too.

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Ice-Phase Precipitation

Meteorological Monographs ◽

10.1175/amsmonographs-d-16-0013.1 ◽

2017 ◽

Vol 58 ◽

pp. 6.1-6.36 ◽

Cited By ~ 17

Author(s):

I. Gultepe ◽

A. J. Heymsfield ◽

P. R. Field ◽

D. Axisa

Keyword(s):

Collection Efficiency ◽

Numerical Models ◽

Mass Density ◽

Three Dimensional ◽

Phase Precipitation ◽

Microphysical Parameters ◽

Mass Size ◽

Ice Water ◽

Ice Phase

AbstractIce-phase precipitation occurs at Earth’s surface and may include various types of pristine crystals, rimed crystals, freezing droplets, secondary crystals, aggregates, graupel, hail, or combinations of any of these. Formation of ice-phase precipitation is directly related to environmental and cloud meteorological parameters that include available moisture, temperature, and three-dimensional wind speed and turbulence, as well as processes related to nucleation, cooling rate, and microphysics. Cloud microphysical parameters in the numerical models are resolved based on various processes such as nucleation, mixing, collision and coalescence, accretion, riming, secondary ice particle generation, turbulence, and cooling processes. These processes are usually parameterized based on assumed particle size distributions and ice crystal microphysical parameters such as mass, size, and number and mass density. Microphysical algorithms in the numerical models are developed based on their need for applications. Observations of ice-phase precipitation are performed using in situ and remote sensing platforms, including radars and satellite-based systems. Because of the low density of snow particles with small ice water content, their measurements and predictions at the surface can include large uncertainties. Wind and turbulence affecting collection efficiency of the sensors, calibration issues, and sensitivity of ground-based in situ observations of snow are important challenges to assessing the snow precipitation. This chapter’s goals are to provide an overview for accurately measuring and predicting ice-phase precipitation. The processes within and below cloud that affect falling snow, as well as the known sources of error that affect understanding and prediction of these processes, are discussed.

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Advanced experimental approaches to marine water-column biogeochemical processes

ICES Journal of Marine Science ◽

10.1093/icesjms/fsx146 ◽

2017 ◽

Vol 75 (1) ◽

pp. 30-42 ◽

Cited By ~ 6

Author(s):

Louis Legendre ◽

Richard B Rivkin ◽

Nianzhi Jiao

Keyword(s):

Water Column ◽

Numerical Models ◽

Free Water ◽

Sea Surface ◽

Biogeochemical Processes ◽

In Situ Experiments ◽

Technological Developments ◽

Approaches To Study ◽

Experimental Approaches

Abstract This “Food for Thought” article examines the potential uses of several novel scientific and technological developments, which are currently available or being developed, to significantly advance or supplement existing experimental approaches to study water-column biogeochemical processes (WCB-processes). After examining the complementary roles of observation, experiments and numerical models to study WCB-processes, we focus on the main experimental approaches of free-water in situ experiments, and at-sea and on-land meso- and macrocosms. We identify some of the incompletely resolved aspects of marine WCB-processes, and explore advanced experimental approaches that could be used to reduce their uncertainties. We examine three such approaches: free-water experiments of lengthened duration using bioArgo floats and gliders, at-sea mesocosms deployed several 100s m below the sea-surface using new biogeochemical sensors, and 50 m-tall on-land macrocosms. These approaches could lead to significant progress in concepts related to marine WCB-processes.

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Dynamics and metastable surface structure of double atomic layer of water molecules and ions at the interface between KBr(c) and water

Pure and Applied Chemistry ◽

10.1351/pac200476010115 ◽

2004 ◽

Vol 76 (1) ◽

pp. 115-122 ◽

Cited By ~ 3

Author(s):

K. Ichikawa ◽

S. Sato ◽

N. Shimomura

Keyword(s):

Surface Structure ◽

Vertical Motion ◽

Atomic Layer ◽

Water Molecules ◽

Potassium Ions ◽

Force Microscopy ◽

Structure And Dynamics ◽

Atomic Force ◽

Bromide Ions

The metastable surface structure and dynamics of water molecules, cations, and anions at the interface between KBr(001) and water have been demonstrated from the images in situ observed in atomic resolution using atomic force microscopy. The vertical motion of potassium ions, which means their own transfer from the equilibrium sites to the upper height right on the underlying bromide ions, has been observed at the interface. They are used to be located in some steady state stabilized by their interaction with water molecules in the double atomic layer at the interface. The observed water molecules bridge two bromide ions by hydrogen bond; the water molecules are sandwiched by the potassium ions and vice versa.

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Coupled Thermo-Hydro-Geochemical Models of Engineered Barrier Systems: The Febex Project

MRS Proceedings ◽

10.1557/proc-663-561 ◽

2000 ◽

Vol 663 ◽

Cited By ~ 2

Author(s):

J. Samper ◽

R. Juncosa ◽

V. Navarro ◽

J. Delgado ◽

L. Montenegro ◽

...

Keyword(s):

Large Scale ◽

Reference Model ◽

Numerical Models ◽

Full Scale ◽

Small Scale ◽

Model Parameters ◽

In Situ Test ◽

Wide Range ◽

Engineered Barrier

ABSTRACTFEBEX (Full-scale Engineered Barrier EXperiment) is a demonstration and research project dealing with the bentonite engineered barrier designed for sealing and containment of waste in a high level radioactive waste repository (HLWR). It includes two main experiments: an situ full-scale test performed at Grimsel (GTS) and a mock-up test operating since February 1997 at CIEMAT facilities in Madrid (Spain) [1,2,3]. One of the objectives of FEBEX is the development and testing of conceptual and numerical models for the thermal, hydrodynamic, and geochemical (THG) processes expected to take place in engineered clay barriers. A significant improvement in coupled THG modeling of the clay barrier has been achieved both in terms of a better understanding of THG processes and more sophisticated THG computer codes. The ability of these models to reproduce the observed THG patterns in a wide range of THG conditions enhances the confidence in their prediction capabilities. Numerical THG models of heating and hydration experiments performed on small-scale lab cells provide excellent results for temperatures, water inflow and final water content in the cells [3]. Calculated concentrations at the end of the experiments reproduce most of the patterns of measured data. In general, the fit of concentrations of dissolved species is better than that of exchanged cations. These models were later used to simulate the evolution of the large-scale experiments (in situ and mock-up). Some thermo-hydrodynamic hypotheses and bentonite parameters were slightly revised during TH calibration of the mock-up test. The results of the reference model reproduce simultaneously the observed water inflows and bentonite temperatures and relative humidities. Although the model is highly sensitive to one-at-a-time variations in model parameters, the possibility of parameter combinations leading to similar fits cannot be precluded. The TH model of the “in situ” test is based on the same bentonite TH parameters and assumptions as for the “mock-up” test. Granite parameters were slightly modified during the calibration process in order to reproduce the observed thermal and hydrodynamic evolution. The reference model captures properly relative humidities and temperatures in the bentonite [3]. It also reproduces the observed spatial distribution of water pressures and temperatures in the granite. Once calibrated the TH aspects of the model, predictions of the THG evolution of both tests were performed. Data from the dismantling of the in situ test, which is planned for the summer of 2001, will provide a unique opportunity to test and validate current THG models of the EBS.

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Soft Robot Based on Hyperelastic Buckling Controlled by Discontinuous Magnetic Field

Journal of Mechanisms and Robotics ◽

10.1115/1.4051241 ◽

2021 ◽

pp. 1-35

Author(s):

Yingdong Xu ◽

Dongze Yan ◽

Kai Zhang ◽

Xuequan Li ◽

Y.F. Xing ◽

...

Keyword(s):

Magnetic Field ◽

Flexible Electronics ◽

Nonlinear Deformation ◽

Numerical Models ◽

Optical Path ◽

Magnetic Composite ◽

Soft Robot ◽

New Ideas ◽

Cargo Transportation ◽

The Magnetic Field

Abstract Most untethered magnetic soft robots are controlled by a continuously applied magnetic field. The accuracy of their motion depends completely on the accuracy of external magnetic field, consequently any slight disturbance may cause a dramatic change. Here, we report a new structure and driven method design to achieve a novel magnetic soft robot, which can achieve accurate and stable locomotion with weakly dependence on the magnetic field. The robot consists of functional magnetic composite materials with one central transportation platform and four crawling arms, whose motion is mainly based on hyperelastic buckling and recovering of the arms. The robot is capable of cargo transportation with multimodal locomotion, such as crawling, climbing and turning with high adaptability to various surfaces. The robot consumes much less driven energy compared to conventional magnetic robots. Moreover, we develop theoretical and numerical models to rationally design the precisely controlled robot. Our study shows applications in terms of transportation functions, such as for optical path adjustments and photographic tasks in complex circumstances. This work also provides new ideas on how to utilize nonlinear deformation more efficiently, one could combine the benefits for both the flexible electronics and actuation applications.

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