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Detailed laboratory astrophysics measurements are, in progress to produce spectral tables for the Fe VII Fe XXIV line emission in the EUV wavelength band. Results for Fe XIII are presented that update line lists used in the Chandra Emission Line Project.
Many years of ground and space observations of the plasmasphere have established a basic understanding of the physics of these plasmas in the inner magnetosphere. However, many questions remain. The EUV Instrument on the IMAGE spacecraft is now providing the first ever global pictures of thermal helium in the plasmasphere. Detached plasma, the sunward extending convection tail, a night-time interior plasmaspheric density cavity, and strong azimuthal plasmaspheric structures are all being revealed. What are the properties of these structures? How do they evolve? What is their relationship to magnetic storms and other plasma populations? These are some of the questions that define the state of plasmaspheric physics, to which IMAGE is now contributing answers. The graphic evidence and preliminary analysis of these features will be presented and discussed.
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The objective of the ORFEUS mission is to launch a deployable/retrievable astronomical platform and obtain ultraviolet spectra for both astrophysically interesting sources and the intervening interstellar medium. Also, the IMAX cameras will obtain footage of both the Shuttle and the ORFEUS-SPAS satellite during the deployment/retrieval operations phase of the ORFEUS-SPAS mission.
With the Coronal Diagnostic Spectrometer operating in rapid cadence (9.8 s) stare mode during a C6.6 flare on the solar disk, we observed a sudden brightening of Fe xix line emission (formed at temperature T ≈ 8 MK) above the pre-flare noise without a corresponding brightening of emission from ions formed at lower temperatures, including He i (0.01 MK), Ov (0.25 MK), and Si xii (2 MK). The sudden brightening persisted as a plateau of Fe xix intensity that endured more than 11 minutes. The Fe xix emission at the rise and during the life of the plateau showed no evidence of significant bulk velocity flows, and hence cannot be attributed to chromospheric evaporation. However, the line width showed a significant broadening at the rise of the plateau, corresponding to nonthermal velocities of at least 89 km s−1 due to reconnection outflows or turbulence. During the plateau He i, Ov, and Si xii brightened at successively later times starting about 3.5 minutes after Fe xix, which suggests that these brightenings were produced by thermal conduction from the plasma that produced the Fe xix line emission; however, we cannot rule out the possibility that they were produced by a weak beam of nonthermal particles. We interpret an observed shortening of the Ov wavelength for about 1.5 minutes toward the middle of the plateau to indicate new upward motions driven by the flare, as occurs during gentle chromospheric evaporation; relative to a quiescent interval shortly before the flare, the Ov upward velocity was around −10 km s−1.
We unveil the three-dimensional structure of quiet-Sun EUV bright points and their temporal evolution by applying a triangulation method to time series of images taken by SECCHI/EUVI on board the STEREO twin spacecraft. For this study we examine the heights and lengths as the components of the three-dimensional structure of EUV bright points and their temporal evolutions. Among them we present three bright points which show three distinct changes in the height and length: decreasing, increasing, and steady. We show that the three distinct changes are consistent with the motions (converging, diverging, and shearing, respectively) of their photospheric magnetic flux concentrations. Both growth and shrinkage of the magnetic fluxes occur during their lifetimes and they are dominant in the initial and later phases, respectively. They are all multi-temperature loop systems which have hot loops (approx. 10(exp 6.2) K) overlying cooler ones (approx 10(exp 6.0) K) with cool legs (approx 10(exp 4.9) K) during their whole evolutionary histories. Our results imply that the multi-thermal loop system is a general character of EUV bright points. We conclude that EUV bright points are flaring loops formed by magnetic reconnection and their geometry may represent the reconnected magnetic field lines rather than the separator field lines.
We report a high-resolution study [0.0036 nm full width at half maximum (FWHM) of electron-impact-induced emission spectra of CO 1t 30, 75 and 100 eV electron-impact energies. The spectral features were acquired in optically thin conditions, and represent the highest resolution single-scattering emission spectrum of CO induced by electron impact yet available.
We study the structure and evolution of solar flare ribbons in the chromosphere to infer properties of magnetic reconnection that occurs in the corona. We analyze the imaging observations of the M7.3 SOL2014-04-18T13 flare obtained by IRIS in both the near and far ultraviolet passbands and by SDO/AIA in the 1600A passband. Two flare ribbons are observed to spread away from the magnetic polarity inversion line as the flare progresses. Using the high-resolution IRIS observations, we measure the width of the newly brightened ribbon front along the extension of the ribbon, which maps the feet of magnetic field lines reconnecting in the current sheet in the corona. We find that the width of the ribbon front is highly structured, possibly reflecting corresponding structure in the coronal current layer. Further the ribbon grows most rapidly with time in regions where non-thermal hard X-ray (HXR) emission is concentrated (Brosius, et al. 2015). The light curve of the ultraviolet emissions in this region, as measured by IRIS and AIA, also well matches the HXR light curve at photon energies above 25 keV. In contrast, the ribbon-width evolution and light curves in other regions along the ribbons do not correlate well with the HXR emission. These results suggest that there is a strong connection between the production of non-thermal electrons and locally enhanced perpendicular extent of flare ribbon fronts, which reflect the inhomogeneous structure and/or reconnection dynamics of the flare current sheet in the corona.
We analyze the structure and evolution of ribbons from the M7.3 SOL2014-04-18T13 flare using ultraviolet images from the Interface Region Imaging Spectrograph and the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), magnetic data from the SDO/Helioseismic and Magnetic Imager, hard X-ray (HXR) images from the Reuven Ramaty High Energy Solar Spectroscopic Imager, and light curves from the Fermi/Gamma-ray Burst Monitor, in order to infer properties of coronal magnetic reconnection. As the event progresses, two flare ribbons spread away from the magnetic polarity inversion line. The width of the newly brightened front along the extension of the ribbon is highly intermittent in both space and time, presumably reflecting nonuniformities in the structure and/or dynamics of the flare current sheet. Furthermore, the ribbon width grows most rapidly in regions exhibiting concentrated nonthermal HXR emission, with sharp increases slightly preceding the HXR bursts. The light curve of the ultraviolet emission matches the HXR light curve at photon energies above 25 keV. In other regions the ribbon-width evolution and light curves do not temporally correlate with the HXR emission. This indicates that the production of nonthermal electrons is highly nonuniform within the flare current sheet. Our results suggest a strong connection between the production of nonthermal electrons and the locally enhanced perpendicular extent of flare ribbon fronts, which in turn reflects the inhomogeneous structure and/or reconnection dynamics of the current sheet. Despite this variability, the ribbon fronts remain nearly continuous, quasi-one-dimensional features. Thus, although the reconnecting coronal current sheets are highly structured, they remain quasi-two-dimensional and the magnetic energy release occurs systematically, rather than stochastically, through the volume of the reconnecting magnetic flux.
Understanding the solar corona requires knowledge of its dynamics through its various layers and subsequent connectivity to the heliosphere. This requires understanding the nature of the outflows and the physical transitions through the middle corona (∼1.5–6.0 Rs). While this region is still inaccessible to in situ measurements, remote sensing observations are available, but their interpretation can be controversial due to line-of-sight effects and the nonradial motion of outflowing structures close to the Sun (≤3.0 Rs). In this work, we describe a method to mitigate these challenges by generating nonradial height–time profiles of outflows by using advanced image processing techniques. The northern and southern boundaries of a large equatorial streamer during the 2008 solar minimum were identified in STEREO/SECCHI solar images, using two different methodologies based on thresholds of brightness and piecewise polynomial function fitting. To address line-of-sight issues, we used tomographic reconstruction of the 3D distribution of the coronal electron density based on SECCHI/COR2 images. Spectral analysis of the time series of the position angle of the streamer boundary revealed its oscillatory nature at some heights at 36–48 and 10.5–14.6 hr. Dividing the distance between the northern and southern streamer boundaries in equal parts at each height, we obtained nonradial height–time paths from which we generated nonradial profiles of corona/solar wind plasma outflow. We tracked outflows as they moved uninterruptedly from the Sun in EUVI, through COR1 and into COR2. Finally, we discuss the preliminary results of nonradial plane-of-sky velocities for a coronal mass ejection and two small-scale features.
Impulsive solar energetic particle (ISEP) events show peculiar elemental composition, with enhanced 3 He and heavy-ion abundances, markedly different from our Solar System composition. Furthermore, the events are characterized by a wide variety of energy spectral shapes from power laws to rounded spectra toward the low energies. Solar sources of the events have been firmly associated with coronal jets. Surprisingly, new observations have shown that events are often accompanied by so-called extremeultraviolet (EUV) coronal waves–a large-scale phenomenon compared to jets. This paper outlines the current understanding of the linkage of EUV waves with jets and energetic ions in ISEP events.
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An EUV light source including a vacuum chamber, a droplets injector operatively connected to the vacuum chamber for directing the droplets into the vacuum chamber, droplets produced by the droplets injector wherein the droplets have one side and another side opposite the one side, the droplets including a solid higher Z bead in a low Z liquid, and at least one laser beam directed onto the one side of the droplets.
A conceptual plan for the development of a comprehensive long duration solar space observatory, The Advanced Solar Observatory (ASO) is described. The ASO is intended to provide solar astronomers with the observational power necessary to address fundamental problems relating to the solar convection zone and activity cycle; the thermal and nonthermal processes that control the transport of energy, mass, and magnetic flux in the solar atmosphere; the generation of the solar wind; and the dynamics of the inner heliosphere. The ASO concept encompasses three proposed Space Station-based instrument ensembles: (1) the High Resolution Telescope Cluster, which includes far ultraviolet, extreme ultraviolet, and X-ray telescopes; (2) the Pinhole/Occulter Facility, which includes Fourier transform and coded aperture hard X-ray and gamma ray telescopes and occulted ultraviolet and visible light coronagraphs; and (3) the High Energy Facility, which contains neutron, gamma ray, and low frequency radio spectrometers. Two other facilities, the Orbiting Solar Laboratory, and a package of Global Dynamics Instrumentation, will, with the Space Station ensembles, form a comprehensive capability for solar physics. The scientific program of the ASO, current instrument concepts for the Space Station based ASO instrument ensembles, and plans for their accommodation on the Space Station are described.
We investigate the structure of accretion disks illuminated by X-rays from a central compact object in a binary system. X-rays can photoionize the upper atmosphere of the disk and form an accretion disk corona (ADC) where emission lines can form. We construct a model to calculate the vertical structure and the emission spectrum of the ADC with parameters appropriate to low-mass X-ray binaries. These models are made by nonlocal thermodynamic equilibrium calculations of ion and level populations and include a large number of atomic processes for 10 cosmically abundant elements. Transfer of radiation is treated by using the escape probability formalism. The vertical temperature profile of the ADC consists of a Compton-heated region and a mid-T zone where the temperature is approximately 10(exp 6) K. A thermal instability occurs close to the disk photosphere and causes the temperature of the ADC to drop abruptly from 10(exp 6) K to several times 10(exp 4) K. The emission spectrum in the optical, ultraviolet, extreme ultraviolet, and X-ray range is discussed and compared with the observations.
By coordinating coronal SOHO observations in white light, ultraviolet, extreme ultraviolet, with radio occultation measurements, and complementing these with modeling, two break-throughs were achieved from this funding: (1) The discovery that minor ions are accelerated much faster than protons in the fast solar wind, and (2) that the imprint of coronal density structures is carried outwards from the Sun into the solar wind. Three refereed papers and one invited review, published in the proceedings of the conference, resulted from this funding. A summary of each is given.
A viewgraph presentation describing an ideal Silicon Carbide detector for ultraviolet, vacuum ultraviolet, extreme ultraviolet and soft x-ray detection is shown. The topics include: 1) An ideal photo-detector; 2) Dark current density of SiC photodiodes at room temperature; 3) Dark current in SiC detectors; 4) Resistive and capacitive feedback trans-impedance amplifier; 5) Avalanche gain; 6) Excess noise; 7) SNR in single photon counting mode; 8) Structure of SiC single photon counting APD and testing structure; 9) Single photon counting waveform and testing circuit; 10) Amplitude of SiC single photon counter; 11) Dark count of SiC APD photon counters; 12) Temperature-dependence of dark count rate; 13) Reduce the dark count rate by reducing the breakdown electric field; 14) Spectrum range for SiC detectors; 15) QE curves of Pt/4H-SiC photodiodes; 16) QE curve of SiC; 17) QE curves of SiC photodiode vs. penetration depth; 18) Visible rejection of SiC photodiodes; 19) Advantages of SiC photodiodes; 20) Competitors of SiC detectors; 21) Extraterrestrial solar spectra; 22) Visible-blind EUV detection; 23) Terrestrial solar spectra; and 24) Less than 1KeV soft x-ray detection.