A Ian F Stewart

A Ian F Stewart

University of Colorado Boulder

H-index: 61

North America-United States

About A Ian F Stewart

A Ian F Stewart, With an exceptional h-index of 61 and a recent h-index of 31 (since 2020), a distinguished researcher at University of Colorado Boulder, specializes in the field of MAVEN, Cassini, Mars, Venus, Ultraviolet Spectroscopy.

His recent articles reflect a diverse array of research interests and contributions to the field:

Implications of Vertical Stability Control on the SPARC Tokamak

Analysis of Equilibrium Pressure and Current Dynamics in SPARC

Overview of SPARC Progress: Construction, Manufacturing, and Operational Planning

Tearing mode detectability in the SPARC tokamak

Optimization of the equilibrium magnetic sensor set for the SPARC tokamak

Assessing the impact of vessel eddy currents on SPARC equilibrium reconstructions

An optical-input Maximum Likelihood Estimation feedback system demonstrated on tokamak horizontal equilibrium control

Full-pulse simulations for SPARC using MOSAIC

A Ian F Stewart Information

University

University of Colorado Boulder

Position

Laboratory for Atmospheric and Space Physics

Citations(all)

11451

Citations(since 2020)

3449

Cited By

8941

hIndex(all)

61

hIndex(since 2020)

31

i10Index(all)

141

i10Index(since 2020)

67

Email

University Profile Page

University of Colorado Boulder

A Ian F Stewart Skills & Research Interests

MAVEN

Cassini

Mars

Venus

Ultraviolet Spectroscopy

Top articles of A Ian F Stewart

Implications of Vertical Stability Control on the SPARC Tokamak

Authors

AO Nelson,DT Garnier,DJ Battaglia,C Paz-Soldan,I Stewart,M Reinke,AJ Creely,J Wai

Journal

arXiv preprint arXiv:2401.09613

Published Date

2024/1/17

To achieve its performance goals, SPARC plans to operate in equilibrium configurations with a strong elongation of , destabilizing the vertical instability. However, SPARC also features a relatively thick conducting wall that is designed to withstand disruption forces, leading to lower vertical instability growth rates than usually encountered. In this work, we use the TokSyS framework to survey families of accessible shapes near the SPARC baseline configuration, finding maximum growth rates in the range of s. The addition of steel vertical stability plates has only a modest () effect on reducing the vertical growth rate and almost no effect on the plasma controllability when the full vertical stability system is taken into account, providing flexibility in the plate conductivity in the SPARC design. Analysis of the maximum controllable displacement on SPARC is used to inform the power supply voltage and current limit requirements needed to control an initial vertical displacement of of the minor radius. From the expected spectra of plasma disturbances and diagnostic noise, requirements for filter latency and vertical stability coil heating tolerances are also obtained. Small modifications to the outboard limiter location are suggested to allow for an unmitigated vertical disturbance as large as of the minor radius without allowing the plasma to become limited. Further, investigations with the 3D COMSOL code reveal that strategic inclusion of insulating structures within the VSC supports are needed to maintain sufficient magnetic response. The workflows presented here help to establish a model for the integrated predictive …

Analysis of Equilibrium Pressure and Current Dynamics in SPARC

Authors

Daniel Burgess,Ian Stewart,Carlos Paz-Soldan,Christopher Hansen

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

The plasma shape of the SPARC tokamak changes as a function of pedestal height and current density distribution. The equilibrium sensitivity to these dynamics is assessed using both the``TokaMaker''time-dependent Grad-Shafranov solver and the time-independent EFIT solver. This investigation informs shape control tolerances, an essential step in avoiding damage to the divertor and first-wall during plasma operation. Changes to the strike point locations as a function of pedestal height are found to be sensitive to the bootstrap current fraction and fidelity of real-time equilibrium reconstructions. This suggests potential challenges in constraining strike point sweep locations if an unexpected L-to-H transition occurs. Additionally, the sensitivity of magnetics-only equilibrium reconstructions to tearing-unstable current profiles is investigated, assessed without the benefit of Motional Stark Effect. These analyses will be …

Overview of SPARC Progress: Construction, Manufacturing, and Operational Planning

Authors

Alexander Creely,John Ball,Devon Battaglia,Alexander Battey,Tom Body,John Boguski,Anson Braun,Michael Brookman,Dan Brunner,Daniel Burgess,Leonardo Corsaro,Davide Curreli,Thomas Eich,Jacqueline Farnsworth,Darren Garnier,Robert Granetz,Joshua Hawke,Jon Hillesheim,Nathan Howard,Jerry Hughes,Thomas Jenkins,Adam Kuang,Yijun Lin,Nikolas Logan,Tom Looby,Shon Mackie,Robert Mumgaard,Clayton Myers,Enrico Panontin,Prasoon Raj,Cristina Rea,Matthew Reinke,John Rice,Pablo Rodriguez-Fernandez,Alex Saperstein,Steven Scott,Khrystyna Shvedova,Inwoo Song,Joshua Souza,Ian Stewart,Ryan Sweeney,Anna Teplukhina,Roy Tinguely,Gregorio Luigi Trevisan,Didier Vezinet,Gregory Wallace,Xinyan Wang,Michael Wigram,Dennis Whyte,Yiru Xiao,Sparc Team Team

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

Commonwealth Fusion Systems (CFS) and its partners are building SPARC, a high field (B T= 12.2 T), compact (R 0= 1.85 m, a= 0.57 m) tokamak designed to achieve Q~ 11 and Pfusio n~ 140 MW at H 98= 1.0. SPARC is under construction in Devens, Massachusetts and has progressed significantly in the past year. Tokamak and plant buildings are nearing completion and installation of the SPARC cryostat base is anticipated by the end of 2023. SPARC magnets are in manufacturing at the CFS magnet factory and will be tested at temperature before assembly into SPARC. Major procured items, such as the vacuum vessel and cryoplant, are well into production at vendors and will be arriving throughout 2024. Early SPARC operation will focus on commissioning the machine and then achieving Q> 1 in DT L-mode plasmas, which have recently been thoroughly analyzed. SPARC will then transition to studying H …

Tearing mode detectability in the SPARC tokamak

Authors

Anson Braun,Christopher Hansen,Alexander Battey,Carlos Paz-Soldan,Ian Stewart,Clayton Myers

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

To prepare for disruption prediction, the SPARC tokamak's [Creely JPP 2020] magnetic sensor arrays' ability to detect tearing modes is assessed. The instabilities are modeled in the ThinCurr code [Battey APS-DPP 2022] and the responses of the proposed sensors are evaluated. The tearing modes are modeled using three-dimensional current filaments running parallel to the magnetic field at the resonant surface. The inductive coupling between the current filaments, vacuum vessel, and modeled sensors is calculated. The sensor amplitudes are then assessed in the frequency domain assuming the tearing mode exhibits a sinusoidal current perturbation along the midplane. By scanning mode rotational frequency and width, the range of detectable tearing modes is determined. It is then determined if the sensitivity and placement of the magnetic sensors is sufficient for reliable detection of tearing modes.

Optimization of the equilibrium magnetic sensor set for the SPARC tokamak

Authors

IG Stewart,RS Granetz,CE Myers,C Paz-Soldan,R Sweeney,CJ Hansen,DT Garnier,DJ Battaglia,AJ Creely,ML Reinke

Journal

Nuclear Fusion

Published Date

2023/9/25

Accurate reconstruction of the plasma equilibrium is imperative for successful operation of the SPARC tokamak. In order to assess the expected reconstruction accuracy throughout the duration of design-point discharges, the EFIT equilibrium reconstruction code was deployed for SPARC. Reconstructions from SPARC baseline scenarios were compared with free-boundary equilibria generated by FreeGS, Toksys, and the Tokamak Simulation Code. The key geometric areas of interest, where design constraints are imposed, included: the inner and outer midplane gaps, the X-point locations, as well as the strike point locations. Successful reconstructions of various reference discharges, using deviations in these key geometric quantities as metrics, were calculated from synthetic signals considering an optimized equilibrium magnetic sensor set. The optimization process for this sensor set combined a scan of …

Assessing the impact of vessel eddy currents on SPARC equilibrium reconstructions

Authors

Ian Stewart,Clayton Myers,Christopher Hansen,Robert Granetz,Carlos Paz-Soldan,Daniel Burgess,Ryan Sweeney,Darren Garnier,Anna Teplukhina,Devon Battaglia,Alexander Creely,Matthew Reinke

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

Accurate determination of the plasma shape, position, and divertor strike points is required to ensure heat and particle loads to in-vessel components are within design limits during operation of SPARC. However, with time varying magnetic coil currents, as well as changing plasma current and shape, the eddy currents induced through various conducting structures and vacuum vessel walls can make equilibrium reconstructions of the plasma geometry challenging. These currents can be especially large during critical periods for plasma control, including plasma start-up and strike point sweeps. To assess the impact of these eddy currents on equilibrium reconstruction quality, a suite of codes including, TSC, FreeGS, ThinCurr, and MEQ were used to determine eddy currents in the conducting structures for different operational scenarios. The newest code, ThinCurr, calculates the full 3D structure of the eddy currents …

An optical-input Maximum Likelihood Estimation feedback system demonstrated on tokamak horizontal equilibrium control

Authors

Rian Chandra,Jeffrey Levesque,Yumou Wei,Boting Li,Alex Saperstein,Ian Stewart,Christopher Hansen,Michael Mauel,Gerald Navratil

Journal

Fusion Engineering and Design

Published Date

2023/6/1

A readily parallelized Maximum Likelihood Estimation (MLE) algorithm with linear computational complexity is demonstrated in real time using only measurements from an extreme ultraviolet (EUV) diagnostic to control the horizontal position of a tokamak plasma. A set of trial emissivity profiles are parameterized by the control quantity of interest (R m), and the MLE is identified from the profile which minimizes the signal reconstruction residual. The algorithm depends on an empirically determined likelihood function with exponential form. EUV emission (λ≈ 15 eV-1 keV) is captured in a poloidal plane by four 16-channel AXUV diodes mounted at different poloidal angles with radial and angular resolution sufficient to discern plasma equilibrium evolution in HBT-EP. Calculations of the plasma major radius by the system are consistent within diagnostic uncertainty for the majority of the discharge with those of: a …

Full-pulse simulations for SPARC using MOSAIC

Authors

Anna Teplukhina,Devon Battaglia,Thomas Body,Mark Boyer,Alexander Creely,Christoph Hasse,Panagiotis Kaloyannis,James Logan,Tom Looby,Josiah Wai,Cassandre Contre,Federico Felici,Antoine Merle,Olivier Sauter,Darren Garnier,Nathan Howard,Pablo Rodriguez-Fernandez,Allen Wang,Oak Nelson,Carlos Paz-Soldan,Ian Stewart

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

MOSAIC (Modelling framewOrk for ScenArIo and Control) is a flexible, modular simulation framework built for efficient planning and optimization of the pulse scenarios needed to achieve the target missions of the SPARC tokamak. The framework supports predictive full-pulse, time-dependent simulations with medium-fidelity plasma models at close-to-real-time computational speeds in order to enable automated optimization of actuator trajectories that satisfy the device constraints and maximize the likelihood of achieving the mission of the scenario. Control-oriented models are derived from the actuator and plasma parameter trajectories in order to support separate closed-loop calculations for control development and testing, particularly for off-normal event response. The first application of MOSAIC illustrates the integration of the Matlab EQuilibrium (MEQ) tools and the core transport solver RAPTOR with reduced …

Measuring fusion gain Q> 1 in SPARC

Authors

Roy Tinguely,Matthew Reinke,Carlos Paz-Soldan,John Ball,Robert Granetz,Nathan Howard,Shon Mackie,Enrico Panontin,Conor Perks,John Rice,Pablo Rodriguez-Fernandez,Xinyan Wang,Devon Battaglia,Alexander Creely,Russell Gocht,Ian Holmes,Clayton Myers,Prasoon Raj,Didier Vezinet,Alexandra Lachmann,Nils Leuthold,Ian Stewart

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

An early-operations mission of the SPARC tokamak [Creely 2020 JPP] is to achieve a fusion plasma gain Q> 1, a measurement which will be fairly scrutinized. In this talk, we present an approach to make this claim with confidence and transparency. The numerator of Q will be the total fusion power (Pfu s) from a majority DT plasma with He3 as a minority species. A suite of neutron diagnostics will make complementary and redundant (primarily DT) fusion neutron measurements. Kinetic profile information (density, temperature, and dilution) will also be used to assess Pfu s, with a minimum viable subset of measurements and chords down-selected by exploring a range of physical synthetic profiles. The denominator of Q will be the sum of ohmic power (measured by standard magnetics) and radio frequency (RF) heating less the stored energy's rate of change (dW/dt). The RF contribution will be the power launched …

Equilibrium reconstruction sensitivity studies on SPARC

Authors

Ian Stewart,Carlos Paz-Soldan,Ryan Sweeney,Darren Garnier,Robert Granetz,Alexander Creely,Clayton Myers,Devon Battaglia,Matthew Reinke

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2022

Accurate reconstruction of the plasma equilibrium is imperative for the successful operation of the SPARC tokamak. In order to assess the expected reconstruction accuracy throughout the duration of design-point discharges, the EFIT equilibrium reconstruction code was deployed for SPARC. Reconstructions from SPARC baseline scenarios were compared with free-boundary equilibria generated by FreeGS, Toksys, and the Tokamak Simulation Code (TSC). The key geometric areas of interest to focus design tolerances include: the inner and outer gaps, the X-point locations, as well as the strike point locations. The deviation of these and other geometric quantities from their nominal positions in the synthetic equilibria were determined considering the addition of error to synthetic measurements of magnetic flux and magnetic field, contributions from eddy currents in conducting structures, applied resonant magnetic …

The Magnetic Diagnostics for SPARC

Authors

Robert Granetz,Ryan Sweeney,Roy Tinguely,Clayton Myers,Matthew Reinke,Chris Chrobak,Devon Battaglia,Alexander Creely,Ian Stewart,Carlos Paz-Soldan,Sparc Team Team

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2022

Although SPARC will be groundbreaking in many ways, its magnetic diagnostics (MAGX) are rather conventional, albeit with several key features driven by SPARC's unique conditions. Nearly all sensors will be located on the interior walls of the vacuum chamber, and therefore baking and DT operation necessitate the use of mineral-insulated cable for the sensors and leads. The lack of in-vessel maintenance opportunities after initial operation warrants careful attention to redundancy and elimination of failure modes. For this reason MAGX will have electrical joints only at the vacuum feedthroughs, and feedthrough prototyping will include exhaustive testing for reliability. The high heat loads and disruption forces on first wall components require extensive structural supports, severely limiting the spaces in which MAGX sensors and leads can be located. As a consequence, nearly all flux measurements will use saddle …

Scenario modeling supporting SPARC design activities

Authors

Devon Battaglia,M Brookman,A Creely,T Looby,C Myers,M Reinke,D Garnier,R Granetz,P Rodriguez-Fernandez,A Battey,A Nelson,I Stewart,C Hansen,J Wai,Sparc Team

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2022

A suite of plasma scenario simulation tools has supported the rapid maturation of the SPARC design basis. An important component of the scenario modeling is a time-dependent electromagnetic calculation that includes an axisymmetric description of the toroidally conductive structures suitable for efficient calculations. A framework utilizing modules from the HEAT code was developed to distill 3D Computer-Aided Design (CAD) models into a meshed 2D description that enables rapid evaluation of design options. An accurate 2D description of the conducting structures is especially important for evaluating plasma startup, ramp-down, strike-point sweeping and the vertical position control system in order to refine the power supply requirements. Psi-Tet calculations for the induced 3D currents in the conductive structures inform the calibration of the lower-fidelity 2D axisymmetric model. Coordinated analysis identified …

Operational space mapping on HBT-EP and DIII-D using Variational Autoencoder (VAE) neural networks

Authors

Yumou Wei,David Arnold,Rian Chandra,Jeffrey Levesque,Boting Li,Alex Saperstein,Ian Stewart,Michael Mauel,Gerald Navratil,Christopher Hansen

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2021

A Variational Autoencoder (VAE) is a type of unsupervised neural network which is able to learn meaningful data representations in a reduced dimension. We present an application in identifying the operational boundary of tokamak experiments. In contrast to disruption prediction by supervised learning algorithms, a VAE maps the input signals onto a low-dimensional latent space by their similarities with neighboring samples, creating a smooth operational space map in which individual shots form continuous trajectories. By projecting the operational parameters onto the same space, this provides an intuitive way for the operator to perform disruption avoidance using a relevant control actuator as a discharge approaches a stability boundary. We implemented a VAE using a dataset of over 3000 shots from HBT-EP and found it to be capable of forming a continuous operational space map and identifying the …

Active mode control using current-injecting electrodes in a tokamak

Authors

Jeffrey Levesque,John Brooks,James Bialek,Michael Mauel,David Arnold,Rian Chandra,Boting Li,Gerald Navratil,Alex Saperstein,Ian Stewart,Yumou Wei,Christopher Hansen

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2021

Feedback control of instabilities is important for maintaining high performance tokamak plasmas near beta limits. A goal of this work is to expand the type of actuators, beyond 3D magnetic coils, that can be used to control instabilities. We demonstrate feedback control using an array of four biased electrodes that inject currents into the plasma along 3D paths. Electrode voltages are phased in response to magnetic sensors near the plasma surface. Resulting control current runs coherently along the magnetic field for some distance before conducting radially from electrodes to the wall, producing a geometry that naturally couples to modes. Injected currents suppress or amplify kink modes, depending on programmed phase between the detected fields and applied electrode voltages. Separate experiments with quiescent plasmas are used to map the driven current paths through the plasma by fitting magnetic sensors …

Suppression of ITG turbulence due to spectral shift during biasing induced H-mode on HBT-EP

Authors

IG Stewart,JW Brooks,JP Levesque,ME Mauel,GA Navratil

Journal

Physics of Plasmas

Published Date

2021/5/1

Investigations of biasing induced H-mode discharges on HBT-EP show that the edge turbulence is consistent with the ion temperature gradient) mode and have allowed for the controlled observation of the effect of applied flow shear on the turbulence. Measurements of the radial wavenumber spectrum of floating potentials at the edge show that the turbulence intensity decreases with increasing shift in the spectrum average⟨ k r⟩ when increasing amounts of bias probe voltage (and increasing amounts of flow shear) is applied. This is in agreement with the spectral shift model [Staebler et al., Phys. Rev. Lett. 110, 055003 2013] for turbulence suppression via sheared flow. A shift in the wavenumber spectrum occurs at applied electrode voltages and currents below the threshold needed for an L–H transition, and a dithering transition is obtained when biasing near the threshold. Suppression of blob-filament …

Transport Barrier Formation on HBT-EP

Authors

Ian G Stewart

Published Date

2021

The physics of the biasing induced LH transition and the mechanism for E× B shear flow suppression of turbulence are investigated on HBT-EP. Detailed measurements of the transverse length scales, behavior, and propagation direction of the edge turbulence match what is expected for the ion temperature gradient (ITG) mode. In the scrape-off layer (SOL), radially propagating blob-filament turbulence is identified and characterized, with velocities, sizes, and distributions comparable to measurements on other devices. Through systematic studies of the effect of applied shear flow on the turbulence, it is found that the E× B suppression of turbulence matches what is expected by the spectral shift model [Staebler et al. 2013 Phys. Rev. Lett. 110 055003]. Namely, the application of shear flow tilts the turbulent eddies and shifts the mean radial wavenumber⟨ k r⟩ of the turbulence spectrum from near zero to finite values …

Tearing mode structure study using tangential EUV/SXR diagnostic system on HBT-EP tokamak

Authors

Boting Li,Jeffrey Levesque,Gerald Navratil,Michael Mauel,Ian Stewart,Alex Saperstein,Rian Chandra,Christopher Hansen

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2021

Measuring and analyzing the intensity of the extreme ultraviolet (EUV) and soft x-ray (SXR) is an effective way to study the internal characteristics of MHD mode structures, including the temperature profiles. We present the progress on the two-color multi-energy EUV/SXR diagnostic system in the HBT-EP tokamak. This system includes a filter wheel with five different groups of dual-filter structure. By using a combination of 100 nm Aluminum and 200 nm Titanium filters with identical plasma views and two AXUV16ELG 16-channel diode arrays, this system can provide temperature profile information versus time by calculating the ratio of the amplitudes of the signals from different filters, calibrated with Thomson scattering system. To improve the frequency response of the amplifiers and advance the ability to study fast rotating modes, we built a new two-stage single-channel amplifier system. It has a bandwidth up to 200 …

Mars in the Ultraviolet: Highlights from (nearly) Six Years of Observations by the MAVEN Imaging UltraViolet Spectrograph

Authors

Justin Deighan,Matteo Crismani,Majd Matta,Michael Stevens,William Mcclintock,John Clarke,Roger Yelle,Franck Montmessin,Franck Lefevre,Bruce Jakosky,Greg Holsclaw,Nicholas Schneider,Michael Chaffin,J Scott Evans,Sonal Jain,Daniel Lo,Zachariah Milby,AIF Stewart,Andrea Hughes

Journal

43rd COSPAR Scientific Assembly. Held 28 January-4 February

Published Date

2021/1

The Mars Atmosphere and Volatile EvolutioN (MAVEN) mission's Imaging Ultraviolet Spectrograph (IUVS) observes Mars in the far and mid ultraviolet (110-340 nm), investigating lower and upper atmospheric structure and indirectly probing neutral atmospheric escape. The instrument is among the most powerful spectrographs sent to another planet, with several key capabilities: separate Far-UV & Mid-UV channels for stray light control; a high-resolution echelle mode to resolve deuterium and hydrogen emissions; internal instrument pointing and scanning capabilities to allow complete mapping and nearly continuous operation; and optimization for airglow studies. After nearly six Earth years in orbit (over three Mars years), IUVS has assembled a large quantity of data and provided insights on present-day processes at Mars including dayglow, nightglow, aurora, meteor showers, clouds, and solar-planetary …

HBT-EP program: MHD dynamics and active control through 3D fields and currents

Authors

Gerald Navratil,David Arnold,Anson Braun,Rian Chandra,Nigel Dasilva,Christopher Hansen,Jeffrey Levesque,Boting Li,Michael Mauel,Matthew Notis,Carlos Paz-Soldan,Yumou Wei

Journal

APS Division of Plasma Physics Meeting Abstracts

Published Date

2023

The HBT-EP research program aims to:(i) understand the physics of scrape-off layer currents (SOLC) and interactions between the helical plasma edge and conducting boundary structures,(ii) test new methods for measurement and mode control that integrate optical and magnetic detector arrays with both magnetic and SOLC feedback, and (iii) understand MHD issues from disruptions, resonant magnetic perturbations, SOLC, and disruption mitigation using an in-vessel passive coil. A two-color multi-energy EUV/SXR tangential array has been used to observe the suppression of sawtooth MHD activity correlated with the coupling of an internal 2/1 mode and an external 3/1 kink mode. This is consistent with observations of flux pumping which broadens the current profile as has been seen in hybrid plasmas in DIII-D and JET. A deep-learning-based MHD mode tracking algorithm to process video frames from the …

Martian water loss to space enhanced by regional dust storms

Authors

Michael S Chaffin,DM Kass,S Aoki,AA Fedorova,J Deighan,K Connour,NG Heavens,A Kleinböhl,SK Jain,J-Y Chaufray,M Mayyasi,JT Clarke,AIF Stewart,JS Evans,MH Stevens,WE McClintock,MMJ Crismani,GM Holsclaw,Franck Lefèvre,DY Lo,Franck Montmessin,NM Schneider,B Jakosky,G Villanueva,G Liuzzi,F Daerden,IR Thomas,J-J Lopez-Moreno,MR Patel,G Bellucci,B Ristic,JT Erwin,AC Vandaele,A Trokhimovskiy,OI Korablev

Journal

Nature Astronomy

Published Date

2021/10

Mars has lost most of its initial water to space as atomic hydrogen and oxygen. Spacecraft measurements have determined that present-day hydrogen escape undergoes large variations with season that are inconsistent with long-standing explanations. The cause is incompletely understood, with likely contributions from seasonal changes in atmospheric circulation, dust activity and solar extreme ultraviolet input. Although some modelling and indirect observational evidence suggest that dust activity can explain the seasonal trend, no previous study has been able to unambiguously distinguish seasonal from dust-driven forcing. Here we present synoptic measurements of dust, temperature, ice, water and hydrogen on Mars during a regional dust event, demonstrating that individual dust events can boost planetary H loss by a factor of five to ten. This regional storm occurred in the declining phase of the known …

See List of Professors in A Ian F Stewart University(University of Colorado Boulder)

A Ian F Stewart FAQs

What is A Ian F Stewart's h-index at University of Colorado Boulder?

The h-index of A Ian F Stewart has been 31 since 2020 and 61 in total.

What are A Ian F Stewart's top articles?

The articles with the titles of

Implications of Vertical Stability Control on the SPARC Tokamak

Analysis of Equilibrium Pressure and Current Dynamics in SPARC

Overview of SPARC Progress: Construction, Manufacturing, and Operational Planning

Tearing mode detectability in the SPARC tokamak

Optimization of the equilibrium magnetic sensor set for the SPARC tokamak

Assessing the impact of vessel eddy currents on SPARC equilibrium reconstructions

An optical-input Maximum Likelihood Estimation feedback system demonstrated on tokamak horizontal equilibrium control

Full-pulse simulations for SPARC using MOSAIC

...

are the top articles of A Ian F Stewart at University of Colorado Boulder.

What are A Ian F Stewart's research interests?

The research interests of A Ian F Stewart are: MAVEN, Cassini, Mars, Venus, Ultraviolet Spectroscopy

What is A Ian F Stewart's total number of citations?

A Ian F Stewart has 11,451 citations in total.

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