A5061996654- Solar and Space Plasma Dynamics
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Ionosphere and magnetosphere dynamics
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Astronomy and Astrophysical Research
- Computational Physics and Python Applications
- Fluid Dynamics and Turbulent Flows
- Gamma-ray bursts and supernovae
- Inertial Sensor and Navigation
- Geophysical and Geoelectrical Methods
- Oil, Gas, and Environmental Issues
- Oceanographic and Atmospheric Processes
- Astronomical Observations and Instrumentation
- Methane Hydrates and Related Phenomena
- Astrophysics and Star Formation Studies
- Electron and X-Ray Spectroscopy Techniques
- Meteorological Phenomena and Simulations
- Advancements in Photolithography Techniques
- History and Developments in Astronomy
- Energetic Materials and Combustion
- Fluid Dynamics and Vibration Analysis
- Rocket and propulsion systems research
Lockheed Martin (United States)
2015-2024
Lockheed Martin (United Kingdom)
2004-2023
Lockheed Martin (Canada)
2023
Deutsches Zentrum für Luft- und Raumfahrt e. V. (DLR)
2005
University of Colorado Boulder
1996-2002
Joint Institute for Laboratory Astrophysics
1996-2002
Nonlinear force-free field (NLFFF) models are thought to be viable tools for investigating the structure, dynamics and evolution of coronae solar active regions. In a series NLFFF modeling studies, we have found that successful in application analytic test cases, relatively when applied numerically constructed Sun-like but they less real data. Different been markedly different line configurations provide widely varying estimates magnetic free energy coronal volume, require consistent, vector...
Splitting of the sun's global oscillation frequencies by large-scale flows can be used to investigate how rotation varies with radius and latitude within solar interior. The nearly uninterrupted observations Global Oscillation Network Group (GONG) yield power spectra high duty cycles signal-to-noise ratios. Frequency splittings derived from GONG confirm that variation rate seen at surface carries through much convection zone, base which is an adjustment layer leading latitudinally...
Solar flares and coronal mass ejections are associated with rapid changes in field connectivity powered by the partial dissipation of electrical currents solar atmosphere. A critical unanswered question is whether involved induced motion pre-existing atmospheric magnetic flux subject to surface plasma flows, or these emergence from within convective zone. We address this problem applying state-of-the-art nonlinear force-free (NLFFF) modeling highest resolution quality vector-magnetographic...
The global scales of solar convection are studied through three-dimensional simulations compressible carried out in spherical shells rotating fluid that extend from the base zone to within 15 Mm photosphere. Such modeling at highest spatial resolution date allows study distinctly turbulent convection, revealing coherent downflow structures associated with giant cells continue play a significant role maintaining differential rotation is achieved. These lower latitudes exhibit prograde...
We compare a variety of nonlinear force-free field (NLFFF) extrapolation algorithms, including optimization, magneto-frictional, and Grad – Rubin-like codes, applied to solar-like reference model. The model used test the algorithms includes realistic photospheric Lorentz forces complex weakly twisted, right helical flux bundle. codes were both forced "photospheric" more "chromospheric" vector magnetic boundary data derived from When chromospheric data, are able recover presence bundle...
The heliospheric magnetic field is of pivotal importance in solar and space physics. rooted the Sun's photosphere, where it has been observed for many years. Global maps based on full disk magnetograms are commonly used as boundary conditions coronal wind models. Two primary observational constraints models (1) open regions model should approximately correspond to holes emission, (2) magnitude flux match that inferred from situ spacecraft measurements. In this study, we calculate both MHD...
We present a method for performing data-driven simulations of solar active region formation and evolution. The approach is based on magnetofriction, which evolves the induction equation assuming plasma velocity proportional to Lorentz force. coronal field are driven by temporal sequences photospheric magnetograms from Helioseismic Magnetic Imager (HMI) instrument onboard Solar Dynamics Observatory (SDO). Under certain conditions, produce flux ropes that ejected modeled due loss equilibrium....
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...
The magnetic field in the solar photosphere frequently carries strong electric currents, even though global coronal configuration often resembles a potential ringed by heliospheric current sheet. To understand this, we compare TRACE EUV images of active-region coronae and potential-field source-surface extrapolations based on SOHO MDI magnetograms for 95 active regions. We conclude that significant nonpotentiality overall occurs (1) when new flux has emerged within or very near region last...
The heliospheric magnetic field is associated with changes in space weather, cosmic-ray flux, and likely climate. This determined by the largest scale patterns of magnetism at solar surface, dominated lower latitude active regions during cycle maximum circumpolar fields minimum. Whereas activity belt readily studied, high-latitude much less accessible, its study requires a combination modeling observation. Current models hold that on Sun solely accumulation transported poleward from regions....
We constrain the properties of mechanism(s) responsible for bulk heating corona Sun by simulating, first time, appearance entire solar corona. Starting from full-sphere magnetic field maps 2000 December 1 and 8, when was moderately active, we populate nearly 50,000 coronal lines with quasi-static loop atmospheres. These atmospheres are based on flux densities FH that depend in different ways half-length L, strength B at chromospheric base, expansion height, scale height. The best match to...
This paper investigates the solar origin of impulsive energetic particle (SEP) events, often referred to as 3He-rich flares, by attempting locate source regions 117 events observed at ~2-3 MeV amu-1. Given large uncertainties when ions these energies were injected, we use type III radio bursts that occur within a 5 hr time window preceding ion onset, and search in EUV X-ray full-disk images for brightenings around times bursts. In this way find sources 69 events. High cadence reveal jet...
Recently, several methods that measure the velocity of magnetized plasma from time series photospheric vector magnetograms have been developed. Velocity fields derived using such techniques can be used both to determine fluxes magnetic energy and helicity into corona, which important consequences for understanding solar flares, coronal mass ejections, dynamo, drive time-dependent numerical models fields. To date, these not rigorously tested against realistic, simulated data sets, in field...
The variable magnetic field of the solar photosphere exhibits periodic reversals as a result dynamo activity occurring within interior. We decompose surface observed by both Wilcox Solar Observatory and Michelson Doppler Imager into its harmonic constituents, present time evolution mode coefficients for past three sunspot cycles. interplay between various modes is then interpreted from perspective general theory, where coupling primary secondary families found to correlate with large-scale...
The nonlinear force-free field (NLFFF) model is often used to describe the solar coronal magnetic field, however a series of earlier studies revealed difficulties in numerical solution application photospheric boundary data. We investigate sensitivity modeling spatial resolution data, by applying multiple codes that numerically solve NLFFF sequence vector magnetogram data at different resolutions, prepared from single Hinode/SOT-SP scan NOAA Active Region 10978 on 2007 December 13. analyze...
Observations of the Sun's corona during space era have led to a picture relatively constant, but cyclically varying solar output and structure. Longer-term, more indirect measurements, such as from 10Be, coupled by other albeit less reliable contemporaneous reports, however, suggest periods significant departure this standard. The Maunder Minimum was one epoch where: (1) sunspots effectively disappeared for long intervals 70 yr period; (2) eclipse observations suggested distinct lack visible...
The most violent space weather events (eruptive solar flares and coronal mass ejections) are driven by the release of free magnetic energy stored in corona. Energy can build up on timescales hours to days, then may be suddenly released form a eruption, which propagates through interplanetary space, possibly impacting Earth's environment. Can we use observed evolution velocity fields photosphere model overlying field, including storage such eruptions? objective CGEM, Coronal Global...
The high-cadence, comprehensive view of the solar corona by SDO/AIA shows many events that are widely separated in space while occurring close together time. In some cases, sets coronal evidently causally related, other instances indirect evidence can be found. We present case studies to highlight a variety coupling processes involved events. find physical linkages between do occur, but concur with earlier these couplings appear crucial understanding initiation major eruptive or explosive...
Abstract In this paper we present an assessment of the status models global solar wind in inner heliosphere. We limit our discussion to class designed provide forecasts, excluding those for purpose testing physical processes idealized configurations. addition, modeling ambient absence coronal mass ejections. cover use both forecast mode and as tools scientific research. a brief history development these models, discussing range approximations use. discuss limitations data inputs available...
ABSTRACT With the global view and high-cadence observations from Solar Dynamics Observatory /Atmospheric Imaging Assembly TErrestrial RElations , many spatially separated solar eruptive events appear to be coupled. However, mechanisms for “sympathetic” are still largely unknown. In this study, we investigate impact of an erupting flux rope on surrounding structures through large-scale magnetic coupling. We build a realistic environment corona 2011 February 15 using magnetohydrodynamics model...
The structure and evolution of solar supergranulation is studied using horizontal velocity fields, deduced from applying local correlation tracking (LCT) techniques to full-disk, line-of-sight Doppler data observed by the Michelson Imager on board Solar Heliospheric Observatory spacecraft. Two 45° square regions photospheric plasma, one quiet Sun with increased magnetic activity, are tracked for as long they remain visible disk (about 6 days), enabling a determination complete life histories...