Engineering topics

Culhane, J. L.

Publications and source records attributed to Culhane, J. L..

At least 19 records

NASA NTRS2007

The Hinode(Solar-B)Mission: An Overview

The Hinode satellite (formerly Solar-B) of the Japan Aerospace Exploration Agency's Institute of Space and Astronautical Science (ISAS/JAXA) was successfully launched in September 2006. As the successor to the Yohkoh mission, it aims to understand how magnetic energy is transferred from the photosphere to the upper atmospheres and resulting in explosive energy releases. Hinode is an observatory style mission, with all the instruments being designed and built to work together to address the science aims. There are three instruments onboard: the Solar Optical Telescope (SOT), the EUV Imaging Spectrometer (EIS), and the X-ray Telescope (XRT). This paper overviews the mission, including the satellite, the scientific payload and operations. It will conclude with discussions on how the international science community can participate in the analysis of the mission data.

Kosugi, T.↗

NASA NTRS2002

Trajectories of Microwave Prominence Eruptions

On the basis of 17 GHz microwave images from the Nobeyama Radioheliograph near solar maximum (1999-2000), we examined trajectories of 50 prominence eruptions in order to address how prominence motions affect or reflect the surrounding coronal structures. We marked the heliocentric latitude of the top of the moving prominences on the white-light synoptic maps, which were constructed at 2.5-4.5 solar radii from the LASCO C2 coronagraph on the SOHO spacecraft. We found that i) 92% of the prominence eruptions were associated with coronal mass ejections (CMEs) and that the remaining 8% show weak mass motions confined to nearby streamers, and ii) coronal mass motions involving prominence eruptions and CMEs are not random but are organized by bundles of streamers. Our findings support the idea of multiple plasma sheets emanating from active regions, arcades, trans-equatorial interconnecting loops, and polar crown filaments, through which coronal mass is transported toward interplanetary space. This study suggests that microwave observations can provide useful information on the activity at the base of such "coronal mass corridors".

Hori, K.↗

NASA NTRS1994

The 1991 November 9 flare at 03.2 UT: Observations from Yohkoh

We discuss X-ray spectra and soft X-ray images of an M1.9 flare that occurred on 1991 November 9 near 03.2 UT. These data were obtained with instrumentation on the Japanese Yohkoh spacecraft. They cover the entire rise phase and peak flare emission, and the beginning of the decay phase. We determine the dynamics, temperature, and emission measure of the flare as inferred from the X-ray line profiles of resonance lines of Fe XXV, Ca XIX, and S XV. We discuss the morphology of the flare as inferred from the soft X-ray images. The November 9 flare is atypical in that a stronger than usual blueshifted emission component (relative to the stationary component) is observed for the resonance lines at flare onset. We discuss several methods for deconvolving the blueshifted component from the stationary component. The X-ray line profiles are consistent with predictions of numerical simulations of chromospheric evaporation. The X-ray images reveal a flare with a complicated loop geometry that is not fully understood. Many of the features in the images are moving upwards at speeds ranging from a few km/s to about 800 km/s. The blueshifted emission begins near the onset of hard X-ray emission, implying that particle acceleration and upflowing plasma have a common energy source.

Doschek, G. A.↗

NASA NTRS1994

The correlation of solar flare hard X-ray bursts with Doppler blueshifted soft X-ray flare emission

We have investigated the temporal correlation between hard X-ray bursts and the intensity of Doppler blueshifted soft X-ray spectral line emission. We find a strong correlation for many events that have intense blueshifted spectral signatures and some correlation in events with modest blueshifts. The onset of hard X-rays frequently coincides to within a few seconds with the onset of blueshifted emission. The peak intensity of blueshifted emission is frequently close in time to the peak of the hard X-ray emission. Decay rates of the blueshifted and hard X-ray emission are similar, with the decay of the blueshifted emission tending to lag behind the hard X-ray emission in some cases. There are, however, exceptions to these conclusions, and, therefore, the results should not be generalized to all flares. Most of the data for this work were obtained from instruments flown on the Japanese Yohkoh solar spacecraft.

Bentley, R. D.↗

NASA NTRS1991

A study of the flaring and quiescent X-ray and UV emission from II Pegasi

An investigation has been conducted of the rotational modulation of the transition-region UV and coronal X-ray emission for the RS CVn system II Pegasi. The X-ray light curve is dominated by a strong flare detected at orbital phase, where the minimum of the photometric wave occurred. The flare parameters derived show that the flare originates with a height greater than half the stellar radius. The characteristics of the flare are similar to those of a solar two-ribbon flare; a comparison of the midtransition region density with that in the coronal region shows a very steep pressure gradient.

Tagliaferri, G.↗

NASA NTRS1990

The X-ray orbital lightcurve of TY Pyx - A 3.2-day eclipsing RS CVn system

An Exosat observation of one orbital cycle of the eclipsing 3.2-d RS CVn system TY Pyx is reported. This system contains two almost identical GV stars, which is unusual because most RS CVns contain F or G main-sequence star and a K subgiant. The X-ray light curves of the primary and secondary eclipses are different above and below 1 keV. At lower energies a sharp eclipse is seen, but at higher energies it is absent. This confirms earlier observations that the 1.5-4.0 x 10 to the 7th K emission from the RS CVn systems is not eclipsed and comes from an extended region, whereas the 7 x 10 to the 6th K emission comes from more compact solarlike active regions. Modeling the X-ray eclipse detected at low energies requires two emission regions, one on each star, covering less than 20 percent of the stellar surface. To avoid a strong orbital modulation caused by both regions being either simultaneously visible, or not visible, they must be located 180 deg apart in longitude. The derived longitudes are 0 and 180 deg; i.e., they point at each other on the inward faces of the two stars.

Culhane, J. L.↗

NASA NTRS1990

An Exosat observation of spectral variability from the RS CVn binary AR Lac

The eclipsing RS CVn system AR Lac (G2IV + K0IV) has been observed continuously for one 2-day binary cycle with the Exosat observatory. Below 1 keV, a factor of two intensity modulation is seen with a flat bottomed minimum around the time of primary eclipse and a shallow dip preceeding primary eclipse. Above 1 keV, where only emission with temperatures greater than 10 exp 7 K would be detected, no orbital modulation or eclipse is seen. This suggests that the greater than 20 million degree emission comes from a large region, comparable in size to the binary separation. The modulation in the less than 1 keV lightcurve has been modeled by chi-squared fitting to X-ray bright spots and by using maximum entropy deconvolution. The lower temperature emission is found to originate in compact regions with a pressure and temperature similar to that of the flaring sun.

White, N. E.↗

NASA NTRS1988

X-ray objective grating spectrograph

A grazing incidence X-ray spectrograph for investigating the spectra of cosmic X-ray sources is described. The overall instrument design is reviewed, and the key components of the spectrograph, including the gratings, telescope, and detector, are examined. Preliminary performance measurements are reported and plans for the instrument are addressed.

Catura, R. C.↗

NASA NTRS1986

X-ray instrumentation in astronomy; Proceedings of the Meeting, Cannes, France, December 2-4, 1985

Recent developments in X-ray and EUV astronomical instrumentation are discussed in reviews and reports. Topics examined include optical systems for the NASA Advanced X-ray Astrophysics Facility (AXAF), specialized X-ray systems, advanced X-ray optics, gas-filled X-ray detectors, instrumentation for spectrometry on AXAF, X-ray and EUV spectrometers, microchannel plate detectors, and solid-state detectors.

Culhane, J. L.↗

NASA NTRS1984

SMM observations of K-alpha radiation from fluorescence of photospheric iron by solar flare X-rays

High-resolution Fe K-alpha spectra near 1.94 A observed during solar flares with the Bent Crystal Spectrometer on the Solar Maximum Mission are presented. The evidence for two possible excitation mechanisms, electron impact and fluorescence, is examined. It is found that the fluorescence mechanism satisfactorily describes the results, while the observations do not support electron collisional excitation of the Fe K-alpha transitions in low ionization stages (II-XII) of iron. Using Bai's model of the fluorescent excitation process, the photospheric iron abundance relative to that of hydrogen is estimated to be 5-6 x 10 to the -5th. The mean height of the soft X-ray source producing the K-alpha fluorescence is calculated on the basis of this model for about 40 large flares. The solar K-alpha lines are found to be about 25 percent wider than those measured in the laboratory. Weak line features observed at wavelengths shorter than that of the K-alpha lines are discussed.

Parmar, A. N.↗

NASA NTRS1984

Results from the X-ray polychromator on SMM

Observations of the soft X-ray emitting plasma by means of the X-Ray Polychromator (XRP) on the Solar Maximum Mission satellite are described. The scientific advances achieved by use of the XRP are in the areas of: (1) flare morphology, (2) spectroscopy and plasma diagnostics, (3) chromospheric evaporation and the physics of flare loops, (4) studies of the microwave emission mechanisms of active regions, (5) the fluorescent excitation of Fe II K-alpha radiation, (6) measurement of variations of calcium abundance for X-ray plasmas, and (7) soft X-ray observations of spray transients. The findings in each of these areas are discussed.

Culhane, J. L.↗

NASA NTRS1982

Solar flare X-ray spectra from the Solar Maximum Mission Flat Crystal Spectrometer

High-resolution solar X-ray spectra obtained with the Flat Crystal Spectrometer aboard the Solar Maximum Mission from two solar flares and a nonflaring active region are analyzed. The 1-22 A region was observed during the flare on 1980 August 25, while smaller spectral regions were repeatedly covered during the 1980 November 5 flare. Voigt profiles were fitted to spectral lines to derive accurate wavelengths and to resolve blends. During the August 25 flare, 205 lines were found in the range 5.68-18.97 A, identifications being provided for all but 40 (mostly weak) lines. Upper limits to flare densities are derived from various line ratios, the hotter (about 10 to the 7th K) ions giving an electron density of less than 10 to the 12th per cu cm for the August 25 flare. Other observed line ratios (e.g., in Fe XVII and Mg XII) indicate a need for revisions in theoretical calculations.

Phillips, K. J. H.↗

NASA NTRS1982

Impulsive phase of flares in soft X-ray emission

Observations using the bent crystal spectrometer instrument on the Solar Maximum Mission show that turbulence and blue-shifted motions are characteristic of the soft X-ray plasma during the impulsive phase of flares, and are coincident with the hard X-ray bursts observed by the hard X-ray burst spectrometer. A method for analysing the Ca XIX and Fe XXV spectra characteristic of the impulsive phase is presented. Nonthermal widths and blue-shifted components in the spectral lines of Ca XIX and Fe XXV indicate the presence of turbulent velocities exceeding 100 km/s and upward motions of 300-400 km/s. The April 10, May 9, and June 29, 1980 flares are studied. The April 10 flare has two separated footpoints bright in hard X-rays. Plasma heated to temperatures greater than ten million K rises from the footpoints. During the three minutes in which the evaporation process occurs an energy of 3.7 x 10 to the 30th ergs. This is consistent with the above figures, allowing for loss by radiation and conduction.

Antonucci, E.↗

NASA NTRS1982

X-ray spectral classification of supernova remnants in the Large Magellanic Cloud

The solid state spectrometer on the Einstein Observatory was used to measure the 0.6-4.5 keV X-ray spectra of six prominent supernova remnants in the Large Magellanic Cloud, namely, N132D, N63A, N49, 0525-66.0, N157B, and 0540-69.3. Thermal emission is detected from the first four remnants and is similar in nature to that observed from young galactic SNRs. In contrast, N157B and 0540-69.3 have featureless X-ray spectra which are well described by power-law models. The present data support a synchrotron origin for the X-rays from N157B and 0540-69.3, although an alternative emission mechanism is considered for the latter object.

Clark, D. H.↗

NASA NTRS1982

High resolution large area modular array of reflectors /LAMAR/ Wolter type I X-ray telescope for Spacelab

The Spacelab Wolter type I X-ray telescope, which is intended for both astronomical observations and the functional verification of the future Large Area Modular Array of Reflectors (LAMAR) concept, comprises five mirrors and is designed to have a blur circle radius of 20 arcsec, with effective areas of (1) 400 sq cm at 0.25 keV, (2) 200 sq cm in the 0.5-2.0 keV range, and (3) 50 sq cm between 2 and 5 keV. A rotary interchange mechanism allows either of two imaging proportional counters to be placed at the telescope focus. The telescope's primary objective is the observational study of galactic and extragalactic X-ray sources, extending the work of the Einstein Observatory to fainter sources and higher energies. Secondarily, the costs and performance to be expected from the use of this telescope type in the LAMAR mission will be assessed.

Catura, R. C.↗

NASA NTRS1982

Fluorescent excitation of photospheric Fe K-alpha emission during solar flares

The Bent Crystal Spectrometer on the NASA Solar Maximum Mission satellite provides high spectral and temporal resolution observations of the Fe K-alpha lines. Analyses have been conducted of spectra from almost 50 solar flares that occurred during 1980. These data strongly support fluorescent excitation of photospheric iron by photons of E greater than 7.11 keV emitted by the hot coronal plasma produced during the flare. After comparison of the data with a model, the observed K-alpha line widths are discussed along with estimates of the size of the emitting region, the height of the coronal source and the photospheric iron abundance.

Parmar, A. N.↗

NASA NTRS1981

Observations of transitions of hydrogen-like Fe XXVI in solar flare spectra

Observations of solar flare spectra over the wavelength range 1.769-1.796 A with the Bent Crystal Spectrometer on the NASA Solar Maximum Mission satellite are presented. The 2P3/2, 2P1/2 and associated satellite transitions of Fe XXVI are identified, their intensities and widths estimated and the results compared with theoretical predictions. For two spectra, which include the isolated n = 2 satellite features, the observations can be reproduced by plasma temperatures of 24,000,000 and 28,400,000 K. Linewidth measurements show evidence for nonthermal velocities of up to 150 km/s. Emission measures derived from the Fe XXVI observations are compared with those from lower temperature Ca XIX and Fe XXV measurements and an emission measure decreasing with temperature is found.

Parmar, A. N.↗

NASA NTRS1981

A European X-ray astrophysics mission

Five instruments (Bragg Spectrometer, Large Area Proportional and Scintillation Counter Detectors, Wide Field X-ray Cameras and a Gamma-Ray Burst Monitor) are discussed and estimates of their performance are given. Their scientific aims are summarized and sample observing programmes are discussed.

Culhane, J. L.↗