scholarly journals O VI Profiles of Solar Quiet and Active Areas Recorded by OSO-8 L.P.S.P. Experiment

1977 ◽  
Vol 43 ◽  
pp. 46-46
Author(s):  
P. Lemaire ◽  
P. McWhirter ◽  
G. Artzner ◽  
J. C. Vial ◽  
R.M. Bonnet ◽  
...  
Keyword(s):  
Transition Zone ◽  
Time Resolution ◽  
Resonance Line ◽  
Angular Resolution ◽  
The Sun ◽  
Direct Measurements ◽  
Ionization Temperature ◽  
Maximum Ionization

O VI resonance line (2s2S - 2p2PO , 103.19 nm) is formed in the chromosphere-corona transition zone with a temperature of maximum ionization of 350 000°C (Jordan, 1969). The OSO-8/LPSP experiment has observed this line with a 0.006 nm resolution, few arcseconds angular resolution and a time resolution up to few seconds. We present the shape of the line in different areas on the sun (quiet and active). As transition lines are used to determine propagation of wave from chromosphere to corona, we compare width of the O VI line with other measurements obtained with lines of lower ionization temperature. From successive profiles we consider the possibility of direct measurements of wave propagating.

scholarly journals Chandra Studies of Supernova Remnants and Pulsars

2001 ◽  
Vol 205 ◽  
pp. 358-365
Author(s):  
Patrick Slane ◽  
John P. Hughes ◽  
Cara E. Rakowski ◽  
David N. Burrows ◽  
John A. Nousek ◽  
...  
Keyword(s):  
Time Resolution ◽  
Supernova Remnants ◽  
Angular Resolution ◽  
Fast Time ◽  
X Ray ◽  
Spatially Resolved ◽  
Unique Capability

With sub-arcsecond angular resolution accompanied by fast time resolution and spatially resolved spectral capabilities, the Chandra X-ray Observatory provides a unique capability for the study of supernova remnants (SNRs) and pulsars. Though in its relative infancy, Chandra has already returned stunning images of SNRs which reveal the distribution of ejecta synthesized in the stellar explosions, the distinct properties of the forward and reverse shocks, and the presence of faint shells surrounding compact remnants. Pulsar observations have uncovered jet features as well as small-scaled structures in synchrotron nebulae. In this brief review we discuss results from early Chandra studies of pulsars and SNRs.

scholarly journals Dielectronic Satellite Spectra in the Soft X-Ray Region

1972 ◽  
Vol 14 ◽  
pp. 655-664 ◽  
Author(s):  
A.H. Gabriel
Keyword(s):  
Steady State ◽  
Solar Flare ◽  
Resonance Line ◽  
Laboratory Experiments ◽  
Transient State ◽  
Dielectronic Recombination ◽  
The Sun ◽  
X Ray ◽  
Long Wavelength ◽  
Dielectronic Satellite

AbstractSatellite lines, situated on the long wavelength side of the helium-like ion resonance line, can be observed in highly-ionized ions both in laboratory sources and from the Sun. Although seen for more than 30 years, these lines have only recently been classified in detail as inner-shell transitions in lithium-like ions. Laboratory experiments have shown that under steady-state conditions these satellites are produced by dielectronic recombination, although in transient ionizing plasmas direct inner-shell excitation can be important. Detailed calculations have been carried out for high Z ions up to copper, and the results can be compared with solar flare spectra in iron. Such comparisons allow both the electron temperature and the transient state of the plasma to be determined. Laboratory spectra from such high-Z ions are different in appearance, and may be dominated by processes resulting from the transient ionizing state of the plasma.

scholarly journals Recent Development of the Nobeyama 17GHz Interferometer and Some Initial Results

1980 ◽  
Vol 86 ◽  
pp. 123-126
Author(s):  
Keizo Kai
Keyword(s):  
Spatial Resolution ◽  
Time Resolution ◽  
Solar Radio ◽  
High Time Resolution ◽  
The Sun ◽  
Radio Observatory ◽  
Time Calibration ◽  
Drift Scan ◽  
Time Variations ◽  
Initial Results

We have constructed a 17GHz interferometer of a multi-correlator type at the Nobeyama Solar Radio Observatory. Novel features of the new interferometer are summarized as (i) high time-resolution up to 0.8 s and (ii) “real-time” calibration of the whole system with an accuracy of ~ 2% for amplitudes and ~ 2° for phases. With the aid of these advantages over an interferometer of a conventional drift-scan type we are able to detect and follow rapid time variations of even a faint source (say, ~ 0.5 s.f.u.) on the Sun with a spatial resolution of ~ 40″. The interferometer has been put in operation since July 1978. We have recorded hundreds of bursts at 17GHz in a year including some tens of rapidly changing sources which would not precisely be measured so far. We present here some preliminary results of observations such as polarization structures of both rapidly changing and GRF bursts.

scholarly journals The Morphology and Physics of the Local Interstellar Medium

1996 ◽  
Vol 152 ◽  
pp. 261-268 ◽  
Author(s):  
Fredrick C. Bruhweiler
Keyword(s):  
Interstellar Medium ◽  
Radiation Field ◽  
Special Role ◽  
Low Density ◽  
The Sun ◽  
Local Interstellar Medium ◽  
Density Region ◽  
Direct Measurements ◽  
Extreme Uv ◽  
Local Cloud

We are finally on the threshold of obtaining a coherent morphological and physical picture for the local interstellar medium (LISM), especially the region within 300 pc of the Sun. The EUVE is playing a special role in revealing this picture. This instrument can provide direct measurements of the the radiation field that photoionizes both hydrogen and helium. It also can yield direct measurements of the column densities of hydrogen, but especially He I and He II toward nearby white dwarfs. These observations suggest that the ionization in the Local Cloud, the cloud in which the Sun is embedded, is not in equilibrium, but in a recombination phase. Heuristic calculations imply that the the present ionization is due to the passage of shocks, at times greater than 3 × 106 years ago. The origin of these shocks are probably linked to the supernova which was responsible for the expanding nebular complex of clouds know as the Loop I supernova remnant, of which the Local Cloud is a part, extreme- UV radiation field, that which ionizes both hydrogen and helium in the LISM. Of the ISM within 300 pc, the volume appears to be predominantly filled by hot (106 K) coronal gas. This gas is laced with six largescale shell structures with diameters ~100−150 pc including the long-recognized radio loops, Loop I−IV, as well as the Orion-Eridanus and Gum Nebulae are identified. An idea that has evolved in the literature for over two decades is that the kinematically-linked OB associations representing Gould’s Belt, plus the gas and dust of Lindblad’s Ring, require that previous supernova activity and stellar winds carved out a 400–600 pc diameter cavity some 3 to 6 × 107 yr ago. This activity produced a pre-existing low density region, into which the present young loop structures have expanded. The outer boundaries of the identified expanding loop structures, inside this preexisting cavity, delineate the periphery of the the mis-named “local interstellar bubble.” Thus, this picture naturally explains some of the problems often associated with the presence of this low density region exterior to Loop I.

scholarly journals The Needs and Requirements from the Standpoint of the Ultraviolet Solar Observations

1968 ◽  
Vol 1 ◽  
pp. 538-540
Author(s):  
E.M. Reeves
Keyword(s):  
Spatial Resolution ◽  
Time Resolution ◽  
Solar Disk ◽  
Emission Lines ◽  
High Time Resolution ◽  
The Sun ◽  
X Ray ◽  
Solar Observations ◽  
Partial Success

Extending from the present to the early part of 1969 there are three Orbiting Solar Observatories to be launched, and these will all be capable of constructing spectroheliograms of the Sun in solar emission lines of the EUV and X-ray region. The recently launched and highly successful OSO-III has obtained EUV and X-ray spectra with high-time resolution, but without spatial resolution on the solar disk. The later OSO satellites will provide spatial resolution of 1′ of arc to 30″ of arc, and will provide the basis for the extension to even higher spatial resolution in the future.The comparatively short periods covered by these satellites, coupled with a real probability of only partial success, make it particularly important to obtain the fullest possible use of the data by implementing a complementary and simultaneous series of ground-based observations.

scholarly journals The Sun at millimeter wavelengths

2020 ◽  
Vol 635 ◽  
pp. A71 ◽  
Author(s):  
Sven Wedemeyer ◽  
Mikolaj Szydlarski ◽  
Shahin Jafarzadeh ◽  
Henrik Eklund ◽  
Juan Camilo Guevara Gomez ◽  
...  
Keyword(s):  
Brightness Temperature ◽  
Large Scale ◽  
Angular Resolution ◽  
Band 3 ◽  
Total Power ◽  
Small Scale ◽  
Solar Chromosphere ◽  
The Sun ◽  
Brightness Temperatures ◽  
Diagnostic Potential

Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started regular observations of the Sun in 2016, first offering receiver Band 3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around 1.25 mm (239 GHz). Aims. Here we present an initial study of one of the first ALMA Band 3 observations of the Sun. Our aim is to characterise the diagnostic potential of brightness temperatures measured with ALMA on the Sun. Methods. The observation covers a duration of 48 min at a cadence of 2 s targeting a quiet Sun region at disc-centre. Corresponding time series of brightness temperature maps are constructed with the first version of the Solar ALMA Pipeline and compared to simultaneous observations with the Solar Dynamics Observatory (SDO). Results. The angular resolution of the observations is set by the synthesised beam, an elliptical Gaussian that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit network patches, internetwork regions, and elongated thin features that are connected to large-scale magnetic loops, as confirmed by a comparison with SDO maps. The ALMA Band 3 maps correlate best with the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit network features and, although very weak in the ALMA maps, imprints of large-scale loops. A group of compact magnetic loops is very clearly visible in ALMA Band 3. The brightness temperatures in the loop tops reach values of about 8000−9000 K and in extreme moments up to 10 000 K. Conclusions. ALMA Band 3 interferometric observations from early observing cycles already reveal temperature differences in the solar chromosphere. The weak imprint of magnetic loops and the correlation with the 171, 131, and 304 SDO channels suggests, however, that the radiation mapped in ALMA Band 3 might have contributions from a wider range of atmospheric heights than previously assumed, but the exact formation height of Band 3 needs to be investigated in more detail. The absolute brightness temperature scale as set by total power measurements remains less certain and must be improved in the future. Despite these complications and the limited angular resolution, ALMA Band 3 observations have a large potential for quantitative studies of the small-scale structure and dynamics of the solar chromosphere.

General Structure of the X-ray Corona

1994 ◽  
Vol 144 ◽  
pp. 69-76
Author(s):  
L. W. Acton
Keyword(s):  
Time Scales ◽  
Time Resolution ◽  
Angular Resolution ◽  
General Structure ◽  
Coronal Holes ◽  
Active Regions ◽  
X Ray ◽  
Structure Changes

AbstractX-ray images have revealed the corona to comprise four basic morphologies. In order of X-ray luminosity these structures are: (1) Bright, relatively short, X-ray loops in active regions, (2) Less bright and larger X-ray structures of the so-called quiet corona, (3) X-ray bright points, and (4) Coronal holes. The soft X-ray telescope (SXT) onYohkohprovides good angular resolution with much improved time resolution and continuity of coverage as compared to the earlier observations. In the SXT movies these structures often appear to be interacting and change appearance on time scales from seconds to weeks. Flare, flare-like, and eruptive processes continuously alter the general structure of the corona. This paper will comment on the structure, changes and heating of the X-ray corona as revealed by theYohkohobservations.

scholarly journals 1.1.2 Helios Zodiacal Light Experiment

1976 ◽  
Vol 31 ◽  
pp. 19-23 ◽  
Author(s):  
E. Pitz ◽  
C. Leinert ◽  
H. Link ◽  
N. Salm
Keyword(s):  
Angular Resolution ◽  
Ecliptic Plane ◽  
The Other ◽  
Integration Time ◽  
The Sun ◽  
Effective Wavelength ◽  
The South ◽  
Zodiacal Light

The Z.L. experiment consists of 3 photometers which are mounted rigidly into the s/c with orientations of about 15°, 30° and 90° south of the s/c – XY-plane, which coincides in orbit with the ecliptic plane (see Fig.1). Helios is spinning uith 1 Hz, and the integration time of the experiment is 513 revolutions. The 90° – photometer always looks to the south ecliptic pole and one revolution of the s/c is divided into 8 sectors to get information on the polarization of Z.L. The polarization is measured by a fixed polaroid foil within the photometer which is rotated by the s/c. In the other two photometers one revolution is split into 32 sectors with different angular resolution. Near the antisun where the gradient in Z.L. intensity is small, the sector length is 4 times the length near the sun (see Fig.2). In these 2 photometers the polarization is obtained by 3 differently oriented polarization foils moved by stepping motors. Intensity and polarization of Z.L. is measured in 3 different colors, which are near the international UBV – system (Ažusienis and Straižs 1969), the effective wavelength shifted by about 100 Å to the blue end.

Putting gravity to work: Imaging of exoplanets with the solar gravitational lens

2019 ◽  
Vol 28 (10) ◽  
pp. 1950125
Author(s):  
Slava G. Turyshev ◽  
Michael Shao ◽  
Viktor T. Toth
Keyword(s):  
Optical Properties ◽  
High Resolution ◽  
Angular Resolution ◽  
Optical Axis ◽  
Space Mission ◽  
Gravitational Lens ◽  
High Resolution Spectroscopy ◽  
The Sun ◽  
Deep Space ◽  
Focal Area

The remarkable optical properties of the solar gravitational lens (SGL) include major brightness amplification ([Formula: see text] on the optical axis, at a wavelength of [Formula: see text]m) and extreme angular resolution ([Formula: see text][Formula: see text]arcsec). A deep space mission equipped with a modest telescope and coronagraph, traveling to the focal area of the SGL that begins at [Formula: see text] astronomical units (AU) from the Sun, offers an opportunity for direct megapixel imaging and high-resolution spectroscopy of a habitable Earth-like exoplanet. We present a basic overview of this intriguing opportunity.

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