A5020101263- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Astrophysics and Star Formation Studies
- Spacecraft and Cryogenic Technologies
- Atmospheric Ozone and Climate
- Climate variability and models
- Oceanographic and Atmospheric Processes
- Earthquake Detection and Analysis
- Magnetic and Electromagnetic Effects
- Fluid Dynamics and Turbulent Flows
- Distributed and Parallel Computing Systems
- Meteorological Phenomena and Simulations
- Computational Physics and Python Applications
- Plasma Diagnostics and Applications
- Photovoltaic System Optimization Techniques
- Adaptive optics and wavefront sensing
- Atomic and Molecular Physics
- Market Dynamics and Volatility
- Advanced Thermodynamics and Statistical Mechanics
- Hydrocarbon exploration and reservoir analysis
High Altitude Observatory
2015-2024
NSF National Center for Atmospheric Research
2015-2024
Laboratory for Atmospheric and Space Physics
2023
University of Colorado Boulder
2023
Northumbria University
2023
AlbaNova
2022
Stockholm University
2022
University Corporation for Atmospheric Research
2010-2021
Max Planck Institute for Solar System Research
2000-2008
Max Planck Society
2000-2008
Results of a three-dimensional MHD simulation sunspot with photospheric size about 20 Mm are presented. The has been carried out the MURaM code, which includes realistic equation state partial ionization and radiative transfer along many ray directions. largely relaxed shows division in central dark umbral region bright dots penumbra showing filaments 2–3 length lanes. By process similar to formation dots, penumbral result from magnetoconvection form upflow plumes, become elongated by...
ABSTRACT We present a new version of the MURaM radiative magnetohydrodynamics (MHD) code that allows for simulations spanning from upper convection zone into solar corona. implement relevant coronal physics in terms optically thin loss, field aligned heat conduction, and an equilibrium ionization equation state. artificially limit Alfvén conduction speeds to computationally manageable values using approximation semi-relativistic MHD with reduced speed light (Boris correction). example...
We present a radiative magnetohydrodynamics simulation of the formation an Active Region on solar surface. The models rise buoyant magnetic flux bundle from depth 7.5 Mm in convection zone up into photosphere. plasma is accompanied by predominantly horizontal expansion. Such expansion leads to scaling relation between density and field strength such that $B\propto\varrho^{1/2}$. emergence photosphere appears as complex pattern, which results interaction rising with turbulent convective...
We present a simple model for the solar differential rotation and meridional circulation based on mean field parameterization of Reynolds stresses that drive rotation. include subadiabatic part tachocline show this, in conjunction with turbulent heat conductivity within convection zone overshoot region, provides key physics to break Taylor-Proudman constraint, which dictates contour lines parallel axis case an isentropic stratification. inclined by 10 - 30 degrees respect is robust result...
Sunspots are concentrations of magnetic field on the visible solar surface that strongly affect convective energy transport in their interior and surroundings. The filamentary outer regions (penumbrae) sunspots show systematic radial outward flows along channels nearly horizontal field. These were discovered 100 years ago present all fully developed sunspots. By using a comprehensive numerical simulation sunspot pair, we penumbral structures with such outflows form when average inclination...
In this paper we discuss a dynamic flux-transport dynamo model that includes the feedback of induced magnetic field on differential rotation and meridional flow. We consider two different approaches for feedback: mean Lorentz force quenching transport coefficients such as turbulent viscosity heat conductivity. find even strong flow does not change character significantly; however, it leads to significant reduction rotation. To large degree independent parameters, saturation takes place when...
MHD simulations of sunspots have successfully reproduced many aspects sunspot fine structure as consequence magneto convection in inclined magnetic field. We study how global properties and penumbral depend on the top boundary condition well grid spacing. The overall radial extent penumbra is subject to condition. All other are resolved at an acceptable level starting from a resolution 48 [24] km (horizontal [vertical]). find that amount inverse polarity flux overturning convective motions...
We present numerical simulations of active region scale flux emergence covering a time span up to 6 days. Flux is driven by bottom boundary condition that advects semi-torus magnetic field with $1.7 \times 10^{22}$ Mx into the computational domain. The show that, even in absense twist, able rise through upper $15.5$ Mm convection zone and emerge photosphere form spots. find spot formation sensitive persistence upflows at footpoints, i.e. continuing upflow would prevent formation. In...
We present a series of radiative MHD simulations addressing the origin and distribution mixed polarity magnetic field in solar photosphere. To this end, we consider numerical that cover uppermost 2–6 Mm convection zone explore scales ranging from 2 km to 25 Mm. study how strength photosphere subsurface layers depend on resolution, domain size, boundary conditions. find 50% energy at τ = 1 level comes fields with less than 500 G resides smaller about 100 km. While probability functions are...
The stratification near the base of Sun's convective envelope is governed by processes overshooting and element diffusion, region widely believed to play a key role in solar dynamo. that gives rise characteristic signal frequencies p modes, which has been used determine depth convection zone investigate extent overshoot. Previous helioseismic investigations have shown spherically symmetric this smoother than standard model without overshooting, ruled out simple models incorporating extend...
The 11-year solar magnetic cycle shows a high degree of coherence in spite the turbulent nature convection zone. It has been found recent high-resolution magnetohydrodynamics simulations that maintenance large-scale coherent field is difficult with small viscosity and diffusivity (≲10 (12) square centimenters per second). We reproduced previous findings indicate reduction energy for lower diffusivities demonstrate recovery global-scale using unprecedentedly resolution. an efficient...
The Daniel K. Inouye Solar Telescope (DKIST) will revolutionize our ability to measure, understand and model the basic physical processes that control structure dynamics of Sun its atmosphere. first-light DKIST images, released publicly on 29 January 2020, only hint at extraordinary capabilities which accompany full commissioning five facility instruments. With this Critical Science Plan (CSP) we attempt anticipate some what those enable, providing a snapshot scientific pursuits hopes engage...
The Multi-slit Solar Explorer (MUSE) is a proposed NASA MIDEX mission, currently in Phase A, composed of multi-slit EUV spectrograph (in three narrow spectral bands centered around 171A, 284A, and 108A) an context imager two passbands 195A 304A). MUSE will provide unprecedented imaging diagnostics the solar corona at high spatial (<0.5 arcsec), temporal resolution (down to ~0.5s) thanks its innovative design. By obtaining spectra 4 bright lines (Fe IX 171A , Fe XV XIX-Fe XXI covering wide...
Abstract Current state-of-the-art spectrographs cannot resolve the fundamental spatial (subarcseconds) and temporal (less than a few tens of seconds) scales coronal dynamics solar flares eruptive phenomena. The highest-resolution data to date are based on imaging, which is blind many processes that drive energetics dynamics. As shown by Interface Region Imaging Spectrograph for low atmosphere, we need high-resolution spectroscopic measurements with simultaneous imaging understand dominant...
Abstract Nonlinear force-free extrapolations are a common approach to estimate the 3D topology of coronal magnetic fields based on photospheric vector magnetograms. The assumption is valid approximation at heights, but for dense plasma conditions in lower atmosphere, this not satisfied. In study, we utilize multiheight field measurements combination with physics-informed neural networks advance solar extrapolations. We include flexible height-mapping, which allows us account different...
The Mount Wilson Ca HK survey revealed magnetic activity variations in a large sample of solar-type stars with timescales ranging from 2.5 to 25 years. This broad range cycle periods is thought reflect differences the rotational properties and depths surface convection zones for various masses ages. In 2007 we initiated long-term monitoring campaign II H K emission 57 southern measure their cycles when possible. We report discovery 1.6-year exoplanet host star iota Horologii, obtain an...
While sunspots are easily observed at the solar surface, determining their subsurface structure is not trivial. There two main hypotheses for of sunspots: monolithic model and cluster model. Local helioseismology only means by which we can investigate subphotospheric structure. However, as current linear inversion techniques do yet allow to probe internal with sufficient confidence distinguish between monolith models, development physically realistic sunspot models a priority...
We analyze in detail the penumbral structure found a recent radiative magnetohydrodynamic simulation. Near τ = 1, simulation produces fine consistent with observationally inferred interlocking comb structure. Fast outflows exceeding 8 km s−1 are present along almost horizontal stretches of magnetic field; outer half penumbra, we see opposite polarity flux indicating returning beneath surface. The bulk brightness is maintained by small-scale motions turning over on scales shorter than length...
We review our current understanding of sunspots from the scales their fine structure to large scale (global) including processes formation and decay. Recently, sunspot models have undergone a dramatic change. In past, several aspects been addressed by static MHD with parametrized energy transport. Models relying heavily on strong assumptions about flow field geometry (e.g., flux-tubes, "gaps", convective rolls), which were motivated in part observed filamentary penumbrae or necessity...
We present a series of numerical sunspot models addressing the subsurface field and flow structure in up to 16 Mm deep domains covering 2 days temporal evolution. Changes photospheric appearance sunspots are driven by flows several depth. Most magnetic is pushed into downflow vertex convection pattern, while some fraction flux separates from main trunk spot. Flux separation deeper layers accompanied photosphere with light bridge formation early stages pores separating spot at later stages....
We use global heliseismic data from the Global Oscillation Network Group, Michelson Doppler Imager on board Solar and Heliospheric Observatory, Helioseismic Magnetic Dynamics to examine behavior, during rising phase of Cycle 24, migrating zonal flow pattern known as torsional oscillation. Although high-latitude part appears be absent in new cycle when flows are derived by subtracting a mean across full solar cycle, it can seen if we subtract over shorter period each these two rotation...
We present a realistic numerical model of sunspot and active region formation based on the emergence flux bundles generated in solar convective dynamo. To this end we use magnetic velocity fields horizontal layer near top boundary dynamo simulation to drive radiative-magnetohydrodynamic simulations upper most layers convection zone. The main results are: (1) emerging rise with mean speed upflows, fragment into small-scale elements that further photosphere, where bipolar pairs are formed...
We investigate small-scale dynamo action in the solar convection zone through a series of high resolution MHD simulations local Cartesian domain with 1$R_\odot$ (solar radius) horizontal extent and radial from 0.715 to 0.96$R_\odot$. The dependence solution on diffusivity is studied. For grid spacing less than 350 km, root mean square magnetic field strength near base reaches 95% equipartition (i.e. kinetic energy are comparable). these solutions Lorentz force feedback velocity found be...
Coronal loops, seen in solar coronal images, are believed to represent emission from magnetic flux tubes with compact cross-sections. We examine the 3D structure of plasma above an active region a radiative magnetohydrodynamic simulation locate volume counterparts for loops. In many cases, loop cannot be linked individual thin strand volume. While loops present synthetic bright structures fewer, and complex shape. demonstrate that this complexity can form impressions even absence strands....