SOLAR OBSERVATIONS WITH A SOFT X-RAY SPECTROMETER
Solar observations with a soft x-ray spectrometer
SUN↗
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A soft X-ray spectrometer for diffuse cosmic sources
The design of a Bragg crystal spectrometer for the diffuse soft X-ray background is described. The instrument has no moving parts; a 6 degree x 20 degree FWHM field of view; resolution in the range 20-100; and spans wavelength ranges 44-80 A or 13-23 A when lead stearate or KAP crystals are used. If placed on a small spacecraft, integration times of approximately 1000 s will be required to detect the existence of the stronger lines expected in the X-ray background.
Borken, R. J.↗
PRELIMINARY SOLAR FLARE OBSERVATIONS WITH A SOFT X-RAY SPECTROMETER ON THE ORBITING SOLAR OBSERVATORY
Preliminary solar flare observations with an x-ray spectrometer carried by the orbiting solar observatory
X-RAY SPECTROSCOPY↗
An overview of the solar maximum mission
The Solar Maximum Mission (SMM), devoted to the study of active solar phenomena is expected to be launched in February 1980 and operate throughout the peak of the current maximum of solar activity. The SMM observatory consists of two main sections: the instrument module which houses the solar payload instruments and the Fine Pointing Sun Sensor System, and the Multimission Modular Spacecraft (MMS) which carries the spacecraft subsystem modules. The entire observatory is 4m long and 2.3m in diameter. The SMM will carry a payload of six instruments specifically selected to study the short wavelength and coronal manifestations of flares. These include: gamma ray spectrometer, hard X-ray burst spectrometer, hard-X-ray imaging spectrometer, soft X-ray polychromator, UV spectrometer and polarimeter, coronagraph/polarimeter and solar constant monitoring package which will measure the total solar irradiance to an accuracy of 0.1 percent. Specific scientific objectives will include: chromospheric evaporation, thermalization, electron acceleration and flare build-up. Complementary studies will be made as part of an SMM Guest Investigator Program. The SMM observation program will be operated on a 24 hour cycle.
Chipman, E. C.↗
Electronic design of a spectrometer for monitoring solar X-ray radiation in space.
Spectrometer monitoring soft solar X-ray radiation in 1 to 400 angstrom wavelength range
SPECTROMETER↗
Further results on cooling mechanisms for soft X-ray flares
Analysis of data from the soft X-ray proportional counter spectrometer on OSO-4 has been continued along the lines of earlier work. It was noticed that the time profiles of X-ray counts from the OSO-4 instrument's 1 to 3 Angstrom detectors for two events showed a very rapid initial decay after maximum, followed by a much more slowly falling section. At least in the case of the larger of the two events, the change of slope seems quite definitely to be discontinuous. Temperatures and emission measures for both flares have been derived, by fitting an emission function to eight-channel count histograms which form the output of the 1 to 3 Angstrom detectors, analyzed into eight energy intervals by pulse-height analysis. The computer program is described. It employs temperature and continuum emission measures in the Culhane-Acton formula and the flux in the 6.7 KeV iron-line feature as free parameters, adjusting them by small amounts in successive iterations until the original historgram is approximately reproduced. A chi-squared is used to examine the agreement between histograms and terminates the iteration accordingly. Account is taken of the proportional counters' energy resolution in the fitting process.
Craig, I. J. D.↗
Precision cleaver for "soft" crystals
"Soft" crystals are cleaved as thin 0.005 inch with special cleaver. Thin slices of soft crystalline materials are used in X-ray spectrometers. Slices are usually cut by hand with wire or blade. Wire tends to scratch surface and to produce slices of nonuniform thickness. Device will rapidly cut soft crystals in smooth, thin, uniform slices.
Benedicto, J. S. J.↗
Detector arrays for photometric measurements at soft X-ray, ultraviolet and visible wavelengths
The construction and modes of operation of the Multi-Anode Microchannel Array (MAMA) detectors are described, and the designs of spectrometers utilizing them are outlined. MAMA consists of a curved microchannel array plate, an opaque photocathode (peak quantum efficiency of 19% at 1216 A), and a multi-anode (either discrete- or coincidence-anode) readout array. Designed for use in instruments on spaceborne telescopes, MAMA can be operated in a windowless configuration in extreme-ultraviolet and soft X-ray wavelengths, or in a sealed configuration at UV and visible wavelengths. Advantages of MAMA include low applied potential (less than 3.0 kV), high gain (greater than 10 to the 6th electrons/pulse), low sensitivity to high-energy charged particles, and immunity to external magnetic fields of less than 500 Gauss
Timothy, J. G.↗
Analysis of X-ray and EUV spectra of solar active regions
Data acquired by two flights of an array of six Bragg crystal spectrometers on an Aerobee rocket to obtain high spatial and spectral resolution observations of various coronal features at soft X-ray wavelengths (9-23A) were analyzed. The various aspects of the analysis of the X-ray data are described. These observations were coordinated with observations from the experiments on the Apollo Telescope Mount and the various data sets were related to one another. The Appendices contain the published results, abstracts of papers, computer code descriptions and preprints of papers, all produced as a result of this research project.
Strong, K. T.↗
The last OSO satellite
Missions planned for OSO-8 are outlined. Instruments to be included on the satellite comprise a multichannel UV spectrometer, a high-resolution UV spectrometer, an X-ray crystal spectrometer and polarimeter, a hard X-ray telescope, a celestial X-ray spectrometer, a mapping X-ray heliometer, an extrasolar extreme UV monitor, and a soft X-ray telescope. The instruments make up a scientific payload that is larger, transmits data at a greater rate, can be pointed with higher accuracy, and has much better spatial and spectral resolution over a wider range of wavelengths than any payload carried by previous OSO satellites.
Maran, S. P.↗
Absolute Calibration and Use of a Soft X-ray Source of Characteristic Carbon Radiation
Measurement of absolute photon yield of carbon K radiation produced by electron bombardment for calibration of grazing incidence grating spectrometer
YIELD↗
On the origin of multiply-impulsive emission from solar flares
A set of solar hard X-ray bursts observed with the hard X-ray burst spectrometer on board the OSO-5 satellite was analyzed. The multiply-impulsive two stage events were selected on the basis of both morphological characteristics and association with appropriate phenomena at other wavelengths. Coincident radio, soft X-ray, H-alpha interplanetary particle, and magnetographic data were obtained from several observatories, to aid in developing a comprehensive picture of the physical processes underlying these complex bursts. Two classes of multiply impulsive bursts were identified: events whose components spikes apparently originate in one location, and events in which groups of spikes appear to come from separate regions which flare sequentially. The origin of multiplicity in the case of a single source region remains unidentified. Purely impulsive emissions show no sign of betatron acceleration, thus eliminating this mechanisn as a candidate for inducing multiply spiked structure. The majority of the two stage bursts, however, exhibited spectral behavior consistent with the betatron model, for the first few minutes of the second stage. Betatron acceleration thus has been identified as a common second stage phenomenon.
Karpen, J. T.↗
Glancing incidence telescope for far ultraviolet and soft X-rays
Glancing-incidence telescope makes observations of distant celestial radiant bodies at wavelengths in the spectral region between 3 and 500 angstroms. The device can be used as a fore-optics system for a laboratory extreme ultraviolet spectrometer, or for the collection or imaging of thermal neutrons.
Neupert, W. M.↗
The soft X-ray polychromator for the Solar Maximum Mission
The paper considers the soft X-ray polychromator (XRP) operating in the 1.4-22.4 A range of the soft X-ray spectrum which includes many emission lines important for the diagnosis of plasmas in the 1.5-50 million deg temperature range. The flat crystal scanning spectrometer provides for a channel polychromatic mapping of flares and active regions in the resonance lines of O VIII, Ne IX, and Mg XI; in its spectral scanning mode it covers essentially the entire 1.4-22.5 A region.
Acton, L. W.↗
Solar X-ray flares observed with the Columbia University instrument on OSO-8
Observations of solar X-ray flares with a graphite-crystal spectrometer aboard the OSO 8 satellite are discussed. The development of the temperature and emission measure of a typical subflare is examined, and the temperature dependence of three Si satellite line systems is derived. Possible electron densities in the range between 10 to the 13th power and 10 to the 14th power per cu cm are determined from the intensities of He-like lines. The results indicate that it is always possible to fit a single-temperature model during all phases of flares and suggest that the energy in a coronal soft X-ray event is injected on time scales of minutes rather than instantaneously.
Parkinson, J. H.↗
Observation of soft X-rays from extended sources
Efforts were directed toward surveying several supernova remnants for the emission of soft X-rays. Rather than attempt to detect such faint X-ray emission, the program was redirected to observe the spectrum and angular structure of the extended X-ray source in the Perseus cluster of galaxies and the super-nova remnant Puppis A. An attempt was made to detect X-ray line emission from Puppis A with a Bragg crystal spectrometer. Observations provide evidence for the presence of X-ray line emission in the spectrum of Puppis A near .65 keV.
Catura, R. C.↗
X-ray spectroscopy of late-type stars
The solid state spectrometer on the Einstein Observatory determined .4 - 4.5 keV spectra for Capella, Algol and 6 RS CVn binaries. All show evidence for a bimodal distribution of emission measure with temperature with one component approximately 7 million degrees and one approximately 40 million degrees. The spread in values of both luminosity and emission measure is 10 for the low temperature component and approximately 500 for the high temperature component. Line emission due to Fe can be identified in most of them and abundances of Si, S and Fe are consistent with approximately solar values in all cases. Estimates indicate dimensions of the emitting regions are on the order of the stellar size and the binary separation for the low and high temperature components, respectively, unless the pressures are high. Variations in the flux were observed, mostly in the hard component for the RS CVn binaries, in the soft component for Capella. A flare was observed during primary eclipse of Algol. The possibility is discussed that the other variations could all be due to intrinsic variability with a time scale of hours-days rather than eclipse or modulation with photometric phase.
Swank, J. H.↗
IUE observations of a luminous M supergiant that exhibits emission continuum in the far ultraviolet
IUE observations of the late-type M supergiant star TV Gem which reveal an intense continuum in the far ultraviolet are discussed. TV Gem was observed in low dispersion in November 1979 and in high and low dispersion in January 1980 by the short and long wavelength cameras of the IUE spectrometer. An essentially featureless UV continuum was obtained, with the exception of a number of broad absorption features in the short wavelength region. A comparison with ground-based observations indicates that at wavelengths greater than 3200 A the continuum emission is essentially due to the M1 supergiant, while at shorter wavelengths the continuum is dominated by a hot companion. The UV continuum can be explained by a B9 or A1 III-IV early companion approximately 2 to 3 magnitudes fainter than the M1 supergiant, or by an accretion disk formed by mass transfer from the extended envelope of the M1 primary onto the surface of a highly condensed secondary. Soft X-ray observations from HEAO 2 are suggested as a means to investigate these interpretations.
Michalitsianos, A. G.↗