Benchmark Test of Differential Emission Measure Codes and Multi-thermal Energies in Solar Active Regions

AbstractIn this review we present a short introduction to the X-ray Telescope on Hinode. We discuss its capabilities and new features and compare it with Yohkoh SXT. We also discuss some of the first results that include observations of X-ray jets in coronal holes, shear change in flares, sigmoid eruptions and evolution, application of filter ratios and differential emission measure analysis, structure of active regions, fine structure of X-ray bright points, and modeling non-potential fields around filaments. Finally, we describe how XRT works with other ground and space-based instrumentation, in particular with TRACE, EIS, SOT, and SOLIS.

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On the Thermal Structure of the Flare-Produced Plasma

Symposium - International Astronomical Union ◽

10.1017/s0074180900071680 ◽

1975 ◽

Vol 68 ◽

pp. 187-189

Author(s):

Ian Craig

Keyword(s):

Thermal Structure ◽

Emission Measure ◽

Active Regions ◽

Delta Function ◽

Power Law Distribution ◽

Differential Emission Measure ◽

X Ray ◽

Fitting Procedure ◽

Bremsstrahlung Emission ◽

Image Position

SummaryRecent flare studies have shown that soft X-ray data are not compatible with simple isothermal models of the source (Herring and Craig, 1973; Craig, 1973; Neupert et al., 1973). With this in mind, the emitting flare plasma has been represented by the temperature-emission measure distribution function, where ζ(T) is the differential emission measure (cm–3 per 106 K), T is the electron temperature in units of 106 K, T0 is a low temperature cut-off for the distribution, αi are real positive numbers, and Ai are positive coefficients determined from data (for appropriate values of T0 and αi) by a least squares fitting procedure. Such a distribution is suggested by results obtained by the present author using simple delta-function representations for ζ(T) (with n ≤ 4); these discreet multi-temperature models usually indicate that the emission measure decreases with increasing temperature. Also, as discussed by Brown (1974), a power law distribution for ζ(T) is consistent with the observed bremsstrahlung emission in the hard X-ray (> 10 keV) domain. In attempting to find a suitable form for the differential emission measure, a simple empirical function of the type assumed by Chambe (1971) for active regions was also tried, but the fit, as evidenced by the χ2 test was unsatisfactory.

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The Structure of Solar Active Regions from EUV and Soft X-Ray Observations

Symposium - International Astronomical Union ◽

10.1017/s007418090007162x ◽

1975 ◽

Vol 68 ◽

pp. 109-131 ◽

Cited By ~ 2

Author(s):

Carole Jordan

Keyword(s):

Spatial Distribution ◽

Active Region ◽

Emission Measure ◽

Active Regions ◽

Flux Tubes ◽

X Ray ◽

Solar Active Regions

The structure of solar active regions derived from EUV and soft X-ray observations is reviewed. The methods by which the emission measure as a function of temperature can be interpreted are discussed. The models of density and temperature which can be made from a variety of combinations of the emission measure with information on the spatial distribution of material, are broadly consistent. They show that the plasma at low heights over the central parts of an active region is hotter and denser than that which extends to greater heights. It appears that much of the emitting material exists in the form of loop structures, presumably magnetically controlled flux tubes. Analytical relationships between the physically important parameters describing the properties of the active region at Te > 2 × 105 K are developed and discussed.

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Radio Measurements of Coronal Magnetic Fields

International Astronomical Union Colloquium ◽

10.1017/s0252921100024933 ◽

1994 ◽

Vol 144 ◽

pp. 21-28 ◽

Cited By ~ 4

Author(s):

G. B. Gelfreikh

Keyword(s):

Magnetic Field ◽

Magnetic Fields ◽

Solar Corona ◽

Active Regions ◽

High Sensitivity ◽

Coronal Magnetic Field ◽

Transverse Magnetic ◽

Radio Sources ◽

Radio Waves ◽

Solar Active Regions

AbstractA review of methods of measuring magnetic fields in the solar corona using spectral-polarization observations at microwaves with high spatial resolution is presented. The methods are based on the theory of thermal bremsstrahlung, thermal cyclotron emission, propagation of radio waves in quasi-transverse magnetic field and Faraday rotation of the plane of polarization. The most explicit program of measurements of magnetic fields in the atmosphere of solar active regions has been carried out using radio observations performed on the large reflector radio telescope of the Russian Academy of Sciences — RATAN-600. This proved possible due to good wavelength coverage, multichannel spectrographs observations and high sensitivity to polarization of the instrument. Besides direct measurements of the strength of the magnetic fields in some cases the peculiar parameters of radio sources, such as very steep spectra and high brightness temperatures provide some information on a very complicated local structure of the coronal magnetic field. Of special interest are the results found from combined RATAN-600 and large antennas of aperture synthesis (VLA and WSRT), the latter giving more detailed information on twodimensional structure of radio sources. The bulk of the data obtained allows us to investigate themagnetospheresof the solar active regions as the space in the solar corona where the structures and physical processes are controlled both by the photospheric/underphotospheric currents and surrounding “quiet” corona.

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