A5003463585- Solar and Space Plasma Dynamics
- Stellar, planetary, and galactic studies
- Ionosphere and magnetosphere dynamics
- Astro and Planetary Science
- Geomagnetism and Paleomagnetism Studies
- Calibration and Measurement Techniques
- Geophysics and Gravity Measurements
- Solar Radiation and Photovoltaics
- Atmospheric Ozone and Climate
- Astronomy and Astrophysical Research
- Gamma-ray bursts and supernovae
- Spacecraft Design and Technology
- CCD and CMOS Imaging Sensors
- Planetary Science and Exploration
- Photocathodes and Microchannel Plates
- X-ray Spectroscopy and Fluorescence Analysis
- History and Developments in Astronomy
- Optical Polarization and Ellipsometry
- Scientific Research and Discoveries
- Adaptive optics and wavefront sensing
- Nuclear Physics and Applications
- Advanced X-ray Imaging Techniques
- Astrophysical Phenomena and Observations
- Spacecraft and Cryogenic Technologies
- Meteorological Phenomena and Simulations
Marshall Space Flight Center
2015-2024
Center for Astrophysics Harvard & Smithsonian
2000-2023
Southwest Research Institute
2023
University of Colorado Boulder
2023
University of Illinois Urbana-Champaign
2023
Predictive Science (United States)
2023
Goddard Space Flight Center
2023
Catholic University of America
2023
Laboratory for Atmospheric and Space Physics
2023
National Space Science and Technology Center
2020
The recent analysis of observations taken with the EUV Imaging Spectrometer and X-Ray Telescope instruments on Hinode suggests that well-constrained measurements temperature distribution in solar active regions can finally be made. Such are critical for constraining theories coronal heating. Past analysis, however, has suffered from limited sample sizes large uncertainties at temperatures between 5 10 MK. Here we present a systematic study differential emission measure 15 region cores. We...
The corona is a layer of hot plasma that surrounds the Sun, traces out its complex magnetic field, and ultimately expands into interplanetary space as supersonic solar wind. Although much has been learned in recent decades from advances observations, theory, computer simulations, we still have not identified definitively physical processes heat accelerate In this review, summarize these speculate about what else required to finally understand fundamental physics system. Specifically: ▪ We...
The High-resolution Coronal Imager (Hi-C) has provided Fe XII 193A images of the upper transition region moss at an unprecedented spatial (~0.3-0.4 arcsec) and temporal (5.5s) resolution. Hi-C observations show in some regions variability on timescales down to ~15s, significantly shorter than minute scale typically found previous moss, therefore challenging conclusion being heated a mostly steady manner. These rapid are located footpoints bright hot coronal loops observed by SDO/AIA 94A...
We systematically investigate the effects of geometrical assumptions in one-dimensional (1D) models coronal loops. Many investigations loops have been based on restrictive assumptions, including symmetry loop shape and heating profile, a uniform cross-sectional area. Starting with solution for symmetric uniform-area heating, we gradually relax these to consider nonuniform area, nonsymmetric shape, show that character solutions can change important ways. find area are more likely experience...
A novel space experiment achieves an unprecedented map of solar magnetic fields from the photosphere to base corona.
Recent Transition Region and Coronal Explorer (TRACE) observations have detected a class of active region loops whose physical properties are inconsistent with previous hydrostatic loop models. In this Letter we present the first co-aligned TRACE Solar Ultraviolet Measurement Emitted Radiation (SUMER) these loops. Although appear static in images, SUMER detects line-of-sight flows along up to 40 km s-1. The presence could imply an asymmetric heating function; such function would be expected...
Active region coronal loop observations with broadband X-ray instruments have often been found to be consistent the predictions of static models. Recent in EUV, however, discovered a class active loops that are difficult reconcile In this paper, we take comprehensive look at how compare We select 67 large range apex temperatures and half-lengths observed either Transition Region Coronal Explorer or Soft X-Ray Telescope. these models using both uniform nonuniform heating. find only 2 fully...
The "coronal heating problem" has been with us over 60 years, and hundreds of theoretical models have proposed without an obvious solution in sight. In this paper we point out that observations show no evidence for local the solar corona, but rather below corona transition region upper chromosphere, subsequent chromospheric evaporation as known flares. New observational scenario comes from (1) temperature evolution coronal loops, (2) overdensity hot (3) upflows (4) Doppler shift (5) upward...
We present observations of high-temperature emission in the core a solar active region using instruments on Hinode and Solar Dynamics Observatory (SDO). These multi-instrument allow us to determine distribution plasma temperatures follow evolution at different temperatures. find that apex loops measure is strongly peaked near 4 MK falls off sharply both higher lower Perhaps most significantly, 0.5 reduced by more than two orders magnitude from peak MK. also temporal broadband soft X-ray...
The frequency of heating events in the corona is an important constraint on coronal mechanisms. Observations indicate that intensities and velocities measured active region cores are effectively steady, suggesting occur rapidly enough to keep high temperature loops close equilibrium. In this paper, we couple observations Active Region 10955 made with XRT EIS \textit{Hinode} test a simple steady model. First calculate differential emission measure apex core. We find DEM be broad peaked around...
We will use new data from the High-resolution Coronal Imager (Hi-C) with unprecedented spatial resolution of solar corona to investigate structure coronal loops down 0.2 arcsec. During a rocket flight Hi-C provided images in wavelength band around 193 A that is dominated by emission Fe XII showing plasma at temperatures 1.5 MK. analyze part field-of-view study smallest observed so far and search for possible sub-structuring larger loops. find tiny MK loop-like structures we interpret as...
Abstract The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; Sounding Rocket was launched from White Sands Missile Range in New Mexico. instrument has been modified its original configuration 1) to observe solar corona a passband that peaks near 172 Å, and uses new, custom-built low-noise camera. targeted Active Region 12712, captured 78 images at cadence 4.4 s (18:56:22 – 19:01:57 UT; 5 min 35 observing time). image spatial resolution varies due...
Following the success of first mission, High-Resolution Coronal Imager (Hi-C) was launched for a third time (Hi-C 2.1) on 29th May 2018 from White Sands Missile Range, NM, USA. On this occasion, 329 seconds 17.2 nm data target active region AR 12712 captured with cadence ~4s, and plate scale 0.129''/pixel. Using by Hi-C 2.1 co-aligned observations SDO/AIA 17.1 we investigate widths 49 coronal strands. We search evidence substructure within strands that is not detected AIA, further consider...
Abstract Measuring the relative amount of high-temperature, low emission measure (EM) plasma is considered to be a smoking-gun observation constrain frequency heating in coronal structures. Often, narrowband, extreme-ultraviolet images, such as those obtained by Atmospheric Imaging Assembly (AIA) on Solar Dynamics Observatory (SDO), are used determine EM distribution, though sensitivity high-temperature limited. Conversely, soft X-ray wavelength range offers multiple diagnostics, including...
Observations with the Transition Region and Coronal Explorer (TRACE) have revealed a new class of active region loops. These loops relatively flat filter ratios, suggesting approximately constant temperatures near 1 MK along much loop length. The observed apex intensities are also higher than static, uniformly heated models predict. appear to persist for longer characteristic cooling time. Recent analysis has indicated that these first in hotter Fe XV 284 Å or XII 195 filters before they...
Recent observations with the Transition Region and Coronal Explorer (TRACE) have shown that many apparently cool (Te ~ 1-1.5 MK) active region loops are much brighter flatter temperature profiles than static loop models predict. Observations also indicate these can persist longer a characteristic cooling time. Using time-dependent hydrodynamic simulations, we explore possibility actually collection of small-scale filaments been impulsively heated through TRACE 171 Å (Fe IX/X) 195 XII)...
Observations made with TRACE have detected a class of persistent active region loops that flat 195/171 Å filter ratios. The intensity these implies density is as much 3 orders magnitude larger than the densities static solutions to hydrodynamic equations. It has recently been suggested are bundles impulsively heated strands cooling through passbands. This scenario would appear in hotter (Fe XV 284 or Fe XII 195 Å) images before appearing cooler IX/X 171 images. In this paper, we test...
In an attempt to test current initiation models of coronal mass ejections (CMEs), with emphasis on the magnetic breakout model, we inspect topology sources 26 CME events in context their chromospheric and response interval approximately 9 hr around eruption onset. First perform current-free (potential) extrapolations photospheric magnetograms retrieve key topological ingredients, such as null points. Then compare reconnection signatures observed high-cadence high spatial resolution...
The timescale for energy release is an important parameter constraining the coronal heating mechanism. Observations of "warm" loops (∼1 MK) have indicated that impulsive and plasma far from equilibrium. In contrast, observations at higher temperatures (∼3 generally been consistent with steady models. Previous observations, however, not able to exclude possibility high temperature are actually composed many small-scale threads in various stages cooling only appear be With new EUV Imaging...
Observing high-temperature, low emission measure plasma is key to unlocking the coronal heating problem. With current instrumentation, a combination of EUV spectral data from Hinode Extreme-ultraviolet Imaging Spectrometer (EIS; sensitive temperatures up 4 MK) and broadband filter X-ray Telescope (XRT; higher temperatures) typically used diagnose temperature structure observed plasma. In this Letter, we demonstrate that "blind spot" exists in temperature–emission space for combined EIS XRT...
Understanding how the solar corona is structured of fundamental importance to determine Sun's upper atmosphere heated high temperatures. Recent spectroscopic studies have suggested that an instrument with a spatial resolution 200 km or better necessary resolve coronal loops. The High Resolution Coronal Imager (Hi-C) achieved this performance on rocket flight in 2012 July. We use Hi-C data measure Gaussian widths 91 loops observed and find distribution peaks at about 270 km. also Atmospheric...
The High-resolution Coronal Imager (Hi-C) flew aboard a NASA sounding rocket on 2012 July 11 and captured roughly 345 s of high-spatial temporal resolution images the solar corona in narrowband 193 Å channel. In this paper, we analyze set rapidly evolving loops that appear an inter-moss region. We select six both fade out Hi-C during short flight. From data, determine size lifetimes characterize whether these simultaneously along their length or first at one footpoint before appearing other....
There is a thin transition region (TR) in the solar atmosphere where temperature rises from 10,000 K chromosphere to millions of degrees corona. Little known about mechanisms that dominate this enigmatic other than magnetic field plays key role. The magnetism TR can only be detected by polarimetric measurements few ultraviolet (UV) spectral lines, Lyman-$\alpha$ line neutral hydrogen at 121.6 nm (the strongest UV spectrum) being particular interest given its sensitivity Hanle effect...