scholarly journals Observations of energetic X-rays from quiescent solar active regions

1968 ◽  
Vol 35 ◽  
pp. 432-438 ◽  
Author(s):  
Loren W. Acton ◽  
Philip C. Fisher
Keyword(s):  
Active Regions ◽  
Flare Activity ◽  
X Rays ◽  
X Ray ◽  
Solar Active Regions ◽  
Optical Flare

A measurement of the solar X-ray spectrum in the 1–30 KeV interval was made by rocket-borne instruments at 0015 UT on April 5, 1967. These measurements show that the solar X-ray spectrum, which falls off steeply with energy below 4 KeV, becomes less steep above this energy. These data are taken to indicate that energetic, non-thermal, electrons are present or continuously produced in quiescent solar active regions. No optical flare activity was reported for several hours around the time of these observations.

scholarly journals Spatially Resolved Observations of Solar Active Regions in Soft X-Rays and Centimetric Wavelengths

1977 ◽  
Vol 43 ◽  
pp. 44-44
Author(s):  
R. Pallavicini ◽  
G. Tofani ◽  
G.S. Vaiana
Keyword(s):  
Active Regions ◽  
Detailed Comparison ◽  
X Rays ◽  
Radio Waves ◽  
X Ray ◽  
Spatially Resolved ◽  
Solar Active Regions ◽  
General Correspondence ◽  
The Magnetic Field ◽  
East West

Soft X-ray images of solar active regions obtained by the S-054 experiment on Skylab have been compared with simultaneous interferometric observations at 2.8 cm. The radio data consist of one-dimensional scans with a spatial resolution of 16 arcseconds in the East-West direction. The resolution, although lower than the X-ray telescope resolution, is high enough for a detailed comparison.We have found that there is a general correspondence in position and size between X-ray and radio sources, but relevant differences are also present. In particular, very bright, narrow components at 2.8 cm appear coaligned with regions of very weak X-ray emission. These strong radio components appear to be localized directly above sunspot umbrae.Models of active regions are investigated both for the atmosphere directly over the sunspot umbra and for regions above the adjacent plage. The presence of the magnetic field is taken into account and its effects on the energy dissipation and on propagation of radio waves are discussed.

scholarly journals High Resolution Soft X-ray Spectroscopy and the Quest for the Hot (5–10 MK) Plasma in Solar Active Regions

2021 ◽  
Vol 8 ◽  
Author(s):  
Giulio Del Zanna ◽  
Vincenzo Andretta ◽  
Peter J. Cargill ◽  
Alain J. Corso ◽  
Adrian N. Daw ◽  
...  
Keyword(s):  
High Resolution ◽  
Active Regions ◽  
High Resolution Spectroscopy ◽  
X Rays ◽  
X Ray ◽  
Hot Plasma ◽  
Exciting Opportunity ◽  
Solar Active Regions ◽  
Opening Up ◽  
Narrow Spectral Region

We discuss the diagnostics available to study the 5–10 MK plasma in the solar corona, which is key to understanding the heating in the cores of solar active regions. We present several simulated spectra, and show that excellent diagnostics are available in the soft X-rays, around 100 Å, as six ionization stages of Fe can simultaneously be observed, and electron densities derived, within a narrow spectral region. As this spectral range is almost unexplored, we present an analysis of available and simulated spectra, to compare the hot emission with the cooler component. We adopt recently designed multilayers to present estimates of count rates in the hot lines, with a baseline spectrometer design. Excellent count rates are found, opening up the exciting opportunity to obtain high-resolution spectroscopy of hot plasma.

scholarly journals X-Ray Spectra of Solar Active Regions

1975 ◽  
Vol 68 ◽  
pp. 45-64 ◽  
Author(s):  
John H. Parkinson
Keyword(s):  
Spectral Resolution ◽  
Active Regions ◽  
X Ray ◽  
Quantitative Theory ◽  
Great Progress ◽  
Solar Active Regions ◽  
Cascading Processes ◽  
Weak Satellite

The last few years have seen great progress in our understanding of X-ray spectra of solar active regions. This paper demonstrates both the usefulness and the limitations of the techniques, both scientific and instrumental, that have recently become available. Improvements in spectral resolution led to the discovery of weak satellite lines to helium-like ions; the quantitative theory for these lines is also discussed. The observed intensities of the Fe XVII lines are also investigated and found to be in agreement with calculations that allow for cascading processes.

scholarly journals Optical Flares of Cygnus X-1

1998 ◽  
Vol 188 ◽  
pp. 384-385
Author(s):  
N.G. Bochkarev ◽  
E.A. Karitskaya ◽  
V.M. Lyuty
Keyword(s):  
Tien Shan ◽  
Flare Activity ◽  
X Ray ◽  
Photoelectric Observations ◽  
Optical Flare

Photoelectric observations of Cyg X-1 in 1996-97 fulfilled in Tien-Shan, Kazakhstan (WBVR), Mt. Maidanak, Uzbekistan (UBVR) and in Crimea, Ukraine (UBV) have detected unusual optical flare activity. During May-August 1996 Cyg X-1 was in high soft X-ray state and after August 9, 1996 it returned to its ordinary state but with some evidences of X-ray activity.

Normal Incidence X-Ray Telescope Power Spectra of X-Ray Emission from Solar Active Regions. II. Theory

1993 ◽  
Vol 405 ◽  
pp. 773 ◽  
Author(s):  
Daniel O. Gomez ◽  
Petrus C. H. Martens ◽  
Leon Golub
Keyword(s):  
Power Spectra ◽  
Active Regions ◽  
Normal Incidence ◽  
X Ray ◽  
Solar Active Regions

X-ray observations of solar active regions from OSO-5

Solar Physics ◽  
1971 ◽  
Vol 17 (1) ◽  
pp. 146-159 ◽  
Author(s):  
J. H. Parkinson ◽  
K. A. Pounds
Keyword(s):  
Active Regions ◽  
X Ray ◽  
Solar Active Regions

scholarly journals Magnetic Helicity of Solar Active Regions as Revealed by Vector Magnetograms and Coronal X-Ray Images

2012 ◽  
Vol 64 (3) ◽  
pp. 54 ◽  
Author(s):  
Haiqing Xu ◽  
Yu Gao ◽  
Hongqi Zhang ◽  
Takashi Sakurai ◽  
Masaoki Hagino ◽  
...  
Keyword(s):  
Active Regions ◽  
Magnetic Helicity ◽  
X Ray ◽  
Vector Magnetograms ◽  
Solar Active Regions

scholarly journals MAGNETIC NON-POTENTIALITY OF SOLAR ACTIVE REGIONS AND PEAK X-RAY FLUX OF THE ASSOCIATED FLARES

2010 ◽  
Vol 721 (1) ◽  
pp. 622-629 ◽  
Author(s):  
Sanjiv Kumar Tiwari ◽  
P. Venkatakrishnan ◽  
Sanjay Gosain
Keyword(s):  
Active Regions ◽  
X Ray ◽  
Solar Active Regions
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