To save this undefined to your undefined account, please select one or more formats and confirm that you agree to abide by our usage policies. If this is the first time you used this feature, you will be asked to authorise Cambridge Core to connect with your undefined account.
Find out more about saving content to .
To save this article to your Kindle, first ensure firstname.lastname@example.org is added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Then enter the ‘name’ part of your Kindle email address below.
Find out more about saving to your Kindle.
Note you can select to save to either the @free.kindle.com or @kindle.com variations. ‘@free.kindle.com’ emails are free but can only be saved to your device when it is connected to wi-fi. ‘@kindle.com’ emails can be delivered even when you are not connected to wi-fi, but note that service fees apply.
The Japanese solar maximum satellite HINOTORI was launched on 21 February 1981, and so far 720 Solar flares were detected including many large flares; the largest observed was a X12 class flare occurred on June 6, 1982. Unfortunately, the data recorder malfunctioned in June, 1982, since then the real time basis observation has been possible to continue. The general introductory explanation and some important results were already published in some proceedings (1, 2, 3 ), therefore we would like to focus on presenting some new results of the Soft X-ray spectra obtained by the spectrometers rather than on talking a review.
The X-Ray Polychromator (XRP) resumed operations on 24 April 1984 following the successful in-orbit repair of the Solar Maximum Mission Satellite. Since that time the two instruments that comprise the XRP, the Flat Crystal Spectrometer (FCS) and the Bent Crystal Spectrometer (BCS), have been used to obtain new spectroscopic data from active regions and flares. The FCS, in particular, has accumulated far more observations of soft X-ray line profiles than were obtained during SMM-I in 1980. For this short presentation, we have chosen two topics to illustrate the type of data that we have obtained since the repair.
The upward motion of the hot thermal regions of several large (M type) solar flares have been determined from the soft X-ray spectral data recorded by the scanning spectrometer (SOLFLEX) on the P78-1 spacecraft. The change in position of the emission is measured with a spatial resolution of 2000 km and a temporal resolution of 58 sec. For the limb flares that are studied, the centroid of the Ca XIX emission region moves to a higher altitude with a speed of 20 to 40 km/sec for a period of 20 to 30 minutes following onset of the flare and reaches an altitude of 30,000 to 40,000 km. The speed of ascent decreases with time, and in several flares that are studied, there is an indication that the centroids of the Ca XIX emission oscillate in altitude with amplitudes of 5,000 to 10,000 km and with periods of 5 to 8 minutes.
The relative concentrations of different ionization stages of iron are measured using the spectral emission of plasmas formed during solar flares. This is an extension of a study on the ionization balance of heavy elements, initiated with the analysis of calcium solar spectra (Antonucci et al., 1984). The data consist of a large set of iron spectra in the wavelength range from 1.84 to 1.88 Å, detected during the recent maximum of activity with the X-ray Polychromator Bent Crystal Spectrometer (BCS) on the NASA Solar Maximum Mission satellite and on the Soft X-ray Crystal Spectrometer (SOX) on the Hinotori satellite.
At the low densities typical of the solar corona, in the steady state the ionization balance of an element is a function of the plasma electron temperature. Hence, it can be measured for plasmas of known temperature and in slowly varying physical conditions, and in most cases, solar flare plasmas can be considered to be in such conditions.
The 21 May event was a large two-ribbon flare which occurred in active region 2456 at S13W15. The flare was extensively documented by coordinated Hα, X-ray, and magnetograph observations. In particular, spatially resolved images in hard X-rays were obtained by the Hard X-ray Imaging Spectrometer (HXIS) aboard SMM. Hence this flare comprises an ideal example for studying the spatial relationship between the X-ray and Hα-ribbon morphologies. Although evidence has been reported for magnetic flux emergence at the beginning of this flare (Harvey, 1983), it appears that a potential field (rising source-surface) model may adequately represent the major large-scale features of the magnetic configuration believed to result from fieldline reconnection in the corona during the decay phase (Kopp and Pneuman, 1976).
We present the first observational evidence for the variation of the coronal calcium abundance in the high-temperature solar flare plasmas. The analyzed data consists of the X-ray flare spectra observed by the Solar Maximum Mission satellite with the Bent Crystal Spectrometer. From BCS spectra we derived the ratio of the line to continuum flux IL/IC for the resonance line of Ca XIX λ = 3.1781Å and the continuum at the same wavelength as a function of the temperature. The studies of 13 flares showed similar temperature dependence during the decay phases, but the agreement of the IL/IC ratio from flare to flare could only be achieved by adjusting an overall normalization factor. As the continuum flux depends weakly on the heavy elemental abundance, this variation of the IL/IC ratio can be attributed to the variation in the calcium abundance. For the flares considered, the variation between the extreme cases represented the factor of 2.5. We stress the consequences of the observed abundance variation for the analysis and interpretation of XUV and X-ray spectra.
The NRL High Resolution Telescope and Spectrograph (HRTS) consists of a telescope, stigmatic UV spectrograph, UV broadband spectroheliograph and Hα film and video cameras. An image of the Sun is focussed onto the slit jaws of the spectrograph by a 30 cm Cassegrain telescope with a spatial resolution of 1". The stigmatic UV spectrograph employs a tandem-Wadsworth mount and photographically records spectra along the 1000" (1 solar radius) slit with a resolution of 50 mÅ in the 1170–1710 Å wavelength region. Images of the slit jaws in a tunable 100 Å bandpass are produced on film by the UV spectroheliograph which uses a reversed tandem-Wadsworth mount. The slit jaws are also viewed through an Hα filter by video and film cameras. To date, the HRTS instrument has flown on four rocket flights and is being prepared for flight on Spacelab-2.
Stark effect detected in high Balmer lines emitted from flares, prominences, and quiet chromosphere is generally interpreted as pressure broadening in a plasma of relatively high density. But a recent study of post-flare loops indicates that the densities of order 1012 cm−3 required to explain the observed Balmer line broadening are an order of magnitude higher than values derived using other plasma diagnostics such as Thomson scattering and Balmer line emission measures (Foukal, Miller, and Gilliam 1983). The disagreement might be explained as the difference expected between the true local density (measured by the Stark effect) in the obviously inhomogeneous loop plasma, and the straight mean or root mean square densities measured by Thomson scattering and line emission measures. More interestingly, the disagreement might imply a macroscopic electric field generated by, e.g., plasma waves in coronal magnetic loops.
The Solar Wind Generation Experiment consists of a UV Coronal Spectrometer (UVCS) provided by the Harvard-Smithsonian Center for Astrophysics and a White Light Coronagraph (WLC) of the High Altitude Observatory. The instruments are similar to those flown together on three sounding rocket flights [1,2,3] but they have enhanced capabilities to take advantage of Spartan’s 27 hour observing period. The two instruments comprise a payload for Spartan 2, which is a self-contained instrument carrier that provides on-board data storage, power, thermal control, sun pointing and an observing program sequencer. Spartan is launched and deployed by the Shuttle and spends about 27 orbits in a detached mode before it is recovered and returned to the ground for data tape retrieval and post-flight instrument calibration.
The HRTS (High Resolution Telescope and Spectrograph) instrument is a high spectral (0.05 Å) and spatial (<1 arc sec) resolution spectrograph with a slit length of 900 arc sec on the solar disk (see Bartoe and Brueckner 1975, 1978). HRTS contains in addition a double grating, zero dispersion broadband spectroheliograph which images the spectrograph slit jaw plate (see Cook et al. 1983). The central wavelength is tunable by changing the grating geometry. Hα images are also photographed from the slit jaw plate image. HRTS has been flown four times as a rocket payload, and will fly in April 1985 as one of the solar experiments aboard Spacelab 2. The four rocket flights of the HRTS program have each been customized for a particular scientific objective. For the fourth flight, because the original hardware was utilized as the basis of the Spacelab HRTS, the opportunity was used to design and build a new rocket HRTS instrument specialized for observations at the solar limb. In this configuration the photographic speed was increased, a new curved slit was fabricated, and the spectroheliograph was modified for limb observations. The scientific observing program was a study of structure and short term temporal evolution at the limb, with a comparison of quiet and coronal hole areas.
Satellite lines are typical features of X-ray spectra. They correspond to radiative transitions involving an inner-shell vacancy. The most studied satellite lines are of the - type, i.e., (ls–2p) transition.
With the advent of Space Astronomy, X-ray spectra emitted by very hot solar plasma have been obtained. By a simple comparison of different spectra, it appears that, for highly ionized atoms, some satellite lines have intensities as large as resonance lines intensities and, more particularly, this is the case for the ls2n. – ls 2pn satellite lines of the 1s2 – ls2p resonance lines.
The analysis of the different population mechanisms responsible for the satellite lines and resonance lines emission has shown that different spectroscopic diagnostics could be derived from line ratios only if atomic data of great accuracy were available. There exists nowadays different atomic data programs adapted to X-ray satellite lines. They have in common to give a great amount of data simultaneously: wavelengths, autoionization and radiative transition probabilities. They take into account correlation and relativistic effects.
After tackling the simple 3-electron system, the programs give now appropriate data for more complex systems but this required large computers because the lines become blended. It is therefore impossible to limit the calculation to the most intense lines.
This talk presented the magnetic confinement experiments from a different angle, i.e. as laboratory sources which allow the study of various problems in such fields as atomic physics and astrophysics.
Tokamak and magnetic mirror plasmas have properties which make them particularly suitable for basic atomic physics experiments; they are stable over long intervals of time and have wide ranges of electrom densities and temperatures. Also, models on which electron density and temperature diagnostics are based in astrophysical research can be checked since these quantities are accurately measured by independent non-spectroscopic methods.
We describe a package of programs for the implementation of the collisional-radiative model to complex configurations. The number of levels taken into account may be several hundreds. The heart of the package is a very efficient program for excitation cross sections in the Distorted Wave framework, using the Relativistic Parametric Potential wave functions. The basic jj coupling scheme actually simplified the computations, enabling a useful factorization into radial and angular parts. Intermediate coupling and configuration interactions are accounted for. We computed ratios of intensities of 3d9 − 3d84s (E2) to 3d9 −3d84p (El) transitions as functions of ne and Te in Xe XXVIII and other Co-like spectra. The atomic model involves all the levels of configurations (3p6)3d9; −3d84s, −3d84p, −3d84d, −3d84f, and (3p5) −3d10, −3d94p. (275 levels) and all the transitions between them. Results compare very well with experimental spectra from TFR.
The soft X-ray lines emitted by highly ionized impurities are one of the most prominent spectral features of today’s tokamaks. In fact the hydrogen isotope plasmas produced in these devices attain temperature values ranging from about one to several keV. A great deal of information about the plasma conditions can be drawn, in particular, from the highly resolved spectra of medium-Z ions which are very rich in satellites excited via dielectronic recombination and innner shell excitation (Dubau and Volontè 1980, Bitter et al. 1979).