Total X-ray Flux Research Articles

Coronal plasma parameters in a long-duration X-ray event observed by SKYLAB

view Abstract Citations (32) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Coronal plasma parameters in a long-duration X-ray event observed by Skylab. Vorpahl, J. A. ; Tandberg-Hanssen, E. ; Smith, J. B., Jr. Abstract Physical conditions in the solar coronal X-ray-emitting plasma are analyzed for an event observed by the S-056 X-ray telescope on Skylab in August 1973. The event was located at the west limb and consisted of a series of high looplike structures that underwent dramatic changes in structure and intensity for more than 50 hours. A total X-ray energy (8 to 20 A) of about 5 by 10 to the 28th power erg is obtained by integrating over the lifetime and is shown to be equivalent to that reported previously for a 'typical' flare. It is found that a first major peak in total X-ray flux and thermal energy density was due to an increase in temperature, a major secondary peak in these parameters corresponded to the time of maximum in density, and conductivity energy losses near maximum intensity were much greater than radiative losses. Models dealing with sources of heating and energy balance are evaluated. Publication: The Astrophysical Journal Pub Date: March 1977 DOI: 10.1086/155074 Bibcode: 1977ApJ...212..550V Keywords: Plasma Physics; Solar Activity; Solar Corona; Solar Flux Density; Solar X-Rays; X Ray Astronomy; Digital Simulation; Energy Dissipation; Mass Flow; Plasma Density; Plasma Temperature; Skylab Program; Solar Flares; Solar Wind; Temperature Distribution; Temperature Gradients; Time Dependence; X Ray Density Measurement; X Ray Telescopes; Solar Physics full text sources ADS |

Ionospheric effects of solar flares—III. The quantitative relationship of flare X-rays to SID's

Abstract This paper describes the effects of changes in the spectral distribution of solar X-rays below 10 A, on the nature and magnitude of Sudden Cosmic Noise Absorption (SCNA) and compares 50 SCNA's with X-ray flares for which spectral distributions could be deduced. It is observed that the SCNA increases by an order of magnitude when the equivalent spectral temperature increases from 2 × 106 °K to 8 × 107 °K even though the total X-ray flux below 10 A is kept constant. It is further observed, from an examination of the threshold case, and from quantitative study of 50 flare events, that the required recombination coefficients in the region 70–90 km are considerably lower than those recently given by Reid (1970), and that these generally fall into one of three categories: one very low, similar to that of Mitra (1968); another relatively high (but lower than that of REId) with values around 2 × 10−5 cm3 sec−1 at 70km and 4 × 10−6 cm3 sec−1 at 80 km, and the third, intermediately between the two and approximating to the models of Adams and Masley (1965) and Mitra and Banerjee (1970). It is suggested that Reid's recombination coefficient model, which is not consistent with any of the flare models, represents the quiet time situation and that during the flare there is a decrease in the coefficient.

A Search for X-Ray Pulsations from Cygnus X-1

view Abstract Citations (43) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A Search for X-Ray Pulsations from Cygnus X-1 Rappaport, S. ; Doxsey, R. ; Zaumen, W. Abstract X-ray data from Cyg X-1 with a timing resolution of 1 ms have been obtained during a soundingrocket ffight. We find flaring activity on time scales down to 50 ms in which the X-ray intensity changes by a factor of 2. There are no regular X-ray pulsations which comprise more than 5 percent of the total X-ray flux in the range 0. .0 s. About 30 percent of the X-ray intensity is modulated with periodicities in the range 1.3-5 s. Publication: The Astrophysical Journal Pub Date: September 1971 DOI: 10.1086/180782 Bibcode: 1971ApJ...168L..43R full text sources ADS |

X-ray Scattering by Grains in the Direction of the Crab Pulsar and Sco XR-1

MOST of the X-ray emission from the Crab Nebula is from a diffuse cloud approximately 100″ in size1,2, and about 10 per cent of the total X-ray flux is in pulsed form3,4, presumably from the optical pulsar. Slysh5 suggests that all of the X-ray flux originates in pulsed form at the pulsar and that scattering by grains washes out the time coherence and produces the observed angular size. This article is a discussion of the hypothesis of Slysh from the observational point of view.

X-radiation studies of the corona

The coronal X-ray emission has been studied in a series of sunpointed Skylark-rocket flights over the period August 1964 to August 1967. Two types of instrument have been used, namely, an array of pinhole cameras, to study the distribution of X-ray sources across the solar disk, and a set of Bragg crystal spectrometers, to examine the detailed spectrum of the emission.Six rocket flights in all (Skylarks 301, 302, 303, 306, 307, and 406) have provided solar X-ray photographs, covering the wave-band 12–60 Å. The main conclusions of this work may be summarised as follows: (1)Of over twenty separate calcium-plages areas, all those having an area-intensity product greater than 300 were associated with enhanced coronal X-radiation, this ‘threshold’ being merely a function of X-ray camera sensitivity.(2)The plages studied were of from 1st to 4th rotation, indicating the enduring nature of the local coronal X-ray enhancement.(3)Crude spectral analysis, derived from different filters used in a given camera array, showed an increasing contrast between the active region and disk emissions below 25 Å, indicating the probability of the active region coronal material being rather hotter.(4)Photographs of regions on the disk and on the limb showed a typical coronal active region to produce more than 50% of its total X-ray flux from a region within 1 arc minute cube. Electron densities up to 10 times the normal coronal values are required by the measured X-ray brightness of the larger regions.(5)The major part of the emission above 20 Å arises from the (cooler) background corona. Examination of this coronal disk emission revealed strong limb brightening, polar darkening (particularly in the 1964–65 photographs) and a band of slightly enhanced X-radiation near latitude 35 °N. The latter observation was noted on successive flights, in October 1965 and February 1966, and clearly followed the tilt in aspect angle of the solar disk.Skylarks 304 and 305 were equipped with uncollimated Bragg crystal spectrometers. The former payload, flown in May 1966, revealed strong line emission down to the scan limit at 11 Å. Emission lines of O VII and VIII, Ne IX and X, Fe XVII and XVIII and NI XIX have been identified. All but the O VII series were found to have dominant components arising from a large active region on the solar disk, and an analysis has shown that the complete active-region spectrum is consistent with an electron temperature of 3 million degrees. Intercomparison of the different emission lines indicated coronal abundances of iron, nickel and neon comparable to those derived earlier by Pottasch from an analysis of the solar UV spectrum.Provisional analysis of the latest flight (Skylark 305 in August 1967), employing crystals of beryl and EDDT in addition to the KAP flown on Skylark 304, has shown strong emission lines of the helium-like ions Mg XI and Si XIII, with weaker but significant intensity in Lyman-α of Mg XII (8·4 Å) and Si XIV (6·2 Å), the latter emission requiring the presence of active region material at a temperature of near 107°K.