A5055414639- Solar and Space Plasma Dynamics
- Astro and Planetary Science
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Geomagnetism and Paleomagnetism Studies
- Ionosphere and magnetosphere dynamics
- Earthquake Detection and Analysis
- Astronomy and Astrophysical Research
- Spacecraft and Cryogenic Technologies
- Fluid Dynamics and Turbulent Flows
- Atmospheric Ozone and Climate
- History and Developments in Astronomy
- Adaptive optics and wavefront sensing
- Global Energy and Sustainability Research
- Astrophysics and Star Formation Studies
- Meteorological Phenomena and Simulations
- Calibration and Measurement Techniques
- Tropical and Extratropical Cyclones Research
- Hydrocarbon exploration and reservoir analysis
- Solar Thermal and Photovoltaic Systems
- Seismic Imaging and Inversion Techniques
- Geophysics and Sensor Technology
- Geophysical and Geoelectrical Methods
- Methane Hydrates and Related Phenomena
New Jersey Institute of Technology
2016-2025
Heliophysics
2014-2024
Ames Research Center
2015-2024
NASA Research Park
2023-2024
Georgia State University
2022
Stanford University
2007-2016
Crimean Astrophysical Observatory
1981-2014
Bear Valley
2013-2014
National Solar Observatory
2014
Pacific Northwest National Laboratory
2014
The Helioseismic and Magnetic Imager (HMI) instrument investigation as a part of the NASA Solar Dynamics Observatory (SDO) is designed to study convection-zone dynamics solar dynamo, origin evolution sunspots, active regions, complexes activity, sources drivers magnetic activity disturbances, links between internal processes corona heliosphere, precursors disturbances for space-weather forecasts. A brief overview instrument, objectives, standard data products presented.
Data from the Global Oscillation Network Group (GONG) project and other helioseismic experiments provide a test for models of stellar interiors thermodynamic radiative properties, on which depend, matter under extreme conditions found in sun. Current are agreement with inferences, suggests, example, that disagreement between predicted observed fluxes neutrinos sun is not caused by errors models. However, GONG data reveal subtle models, such as an excess sound speed just beneath convection...
The splitting of the frequencies global resonant acoustic modes Sun by large-scale flows and rotation permits study variation angular velocity Ω with both radius latitude within turbulent convection zone deeper radiative interior. nearly uninterrupted Doppler imaging observations, provided Solar Oscillations Investigation (SOI) using Michelson Imager (MDI) on Heliospheric Observatory (SOHO) spacecraft positioned at L1 Lagrangian point in continuous sunlight, yield oscillation power spectra...
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...
By applying time-distance helioseismology measurements and inversions to Solar Heliospheric Observatory (SOHO) Michelson Doppler Imager (MDI) dynamics campaign data, we obtain synoptic maps of subsurface plasma-flow fields at a depth 0-12 Mm for seven solar Carrington rotations, covering the years 1996-2002, from solar-activity minimum maximum. Vorticity distribution both zonal meridional flows are derived such flow maps, which contain an enormous amount information about dynamics. The...
Global Oscillation Network Group data reveal that the internal structure of sun can be well represented by a calibrated standard model. However, immediately beneath convection zone and at edge energy-generating core, sound-speed variation is somewhat smoother in than it This could consequence chemical inhomogeneity too severe model, perhaps owing to inaccurate modeling gravitational settling or neglected macroscopic motion may present sun. Accurate knowledge sun's enables inferences made...
A time-distance helioseismic technique is employed to analyze a set of high-resolution Dopplergram observations large sunspot by SOHO/MDI on 1998 June 18. regularized, damped least-squares inversion applied the measurements travel times infer mass flows around below solar surface. Powerful converging and downward directed are detected at depths 1.5-5 Mm, which may provide observational evidence for downdrafts vortex that were suggested Parker cluster model sunspots. Strong outflows extending...
Meridional flow in the solar interior plays an important role redistributing angular momentum and transporting magnetic flux inside Sun. Although it has long been recognized that meridional is predominantly poleward at Sun's surface its shallow interior, location of equatorward return profile deeper remain unclear. Using first two years continuous helioseismology observations from Solar Dynamics Observatory / Helioseismic Magnetic Imager, we analyze travel times acoustic waves propagate...
The magnetic flux that is generated by dynamo processes inside the Sun emerges in form of bipolar regions. properties these directly observable signatures can be extracted from full-disk solar magnetograms. most homogeneous, high-quality synoptic data set magnetograms has been obtained with Michelson Doppler Imager (MDI) instrument on Solar and Heliospheric Observatory spacecraft during 1995–2011. We have developed an IDL program has, when applied to 73,838 MDI set, automatically identified...
The primary science goal of the Kepler Mission is to provide a census exoplanets in solar neighborhood, including identification and characterization habitable Earth-like planets. asteroseismic capabilities mission are being used determine precise radii ages for target stars from their solar-like oscillations. Chaplin et al. (2010) published observations three bright G-type stars, which were monitored during first 33.5 days operations. One these subgiant KIC 11026764, exhibits characteristic...
We present preliminary asteroseismic results from Kepler on three G-type stars. The observations, made at one-minute cadence during the first 33.5d of science operations, reveal high signal-to-noise solar-like oscillation spectra in all stars: About 20 modes may be clearly distinguished each star. discuss appearance spectra, use frequencies and frequency separations to provide radii, masses ages stars, comment light these prospects for inference other solar-type stars that will observe.
To explore the physics of large-scale flows in solar-like stars, we perform 3D anelastic simulations rotating convection for global models with stratification resembling solar interior. The numerical method is based on an implicit large-eddy simulation approach designed to capture effects from non-resolved small scales. We obtain two regimes differential rotation, equatorial zonal accelerated either direction rotation (solar-like) or opposite (anti-solar). While tend produce multiple cells...
Solar Energetic Particle (SEP) events are interesting from a scientific perspective as they the product of broad set physical processes corona out through extent heliosphere, and provide insight into particle acceleration transport that widely applicable in astrophysics. From operations perspective, SEP pose radiation hazard for aviation, electronics space, human space exploration, particular missions outside Earth's protective magnetosphere including to Moon Mars. Thus, it is critical...
High-resolution observations of a large solar flare on 2000 July 14 ("Bastille Day Flare") from the Michelson Doppler Imager instrument SOHO spacecraft reveal rapid variations magnetic field in lower atmosphere during flare. Some these were irreversible, occurred vicinity neutral lines, and likely related to energy release A surprising result is that happened very rapidly scale 10-15 minutes area ~50 Mm2 at beginning Other, more localized impulsive somewhat similar "magnetic transients"...
A new method is presented of determining the three-dimensional sound-speed structure and flow velocities in solar convection zone by inversion acoustic travel-time data recently obtained Duvall coworkers. The initial results reveal large-scale subsurface structures flows related to active regions, are important for understanding physics activity convection. provide evidence a zonal below surface low-latitude area magnetic activity. Strong converging downflows, up 1.2 km s-1, substantial...
The layer of transition from the nearly rigid rotation radiative interior to latitudinal differential convection zone plays a significant role in internal dynamics Sun. Using rotational splitting coefficients p-mode frequencies, obtained during 1986-1990 at Big Bear Solar Observatory, we have found that thickness transitional is 0.09 ± 0.04 solar radii (63 28 Mm), and most occurs beneath adiabatically stratified part zone, as suggested by dynamo theories 22 yr activity cycle.
The Global Oscillation Network Group (GONG) project estimates the frequencies, amplitudes, and linewidths of more than 250,000 acoustic resonances sun from data sets lasting 36 days. frequency resolution a single set is 0.321 microhertz. For frequencies averaged over azimuthal order m , median formal error 0.044 microhertz, associated fractional 1.6 × 10 −5 . 3-year set, expected to be 3 −6 GONG -averaged measurements differ other helioseismic by 0.03 0.08 differences arise combination...
Three helioseismic instruments on the Solar and Heliospheric Observatory have observed Sun almost continuously since early 1996. This has led to detailed study of biases induced by that measure intensity or Doppler velocity variation. Photospheric turbulence hardly influences tiny signature conditions in energy-generating core low-order modes, which are therefore very informative. We use sound-speed density profiles inferred from GOLF MDI data including these together with recent...