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Solar-active region physical parameters inferred from a thermal cyclotron line and soft-x-ray spectral lines

Technical Report ·
OSTI ID:6215592
; ; ;
Simultaneous high-resolution observations of coronal loops are presented at 20-cm wavelength with the Very Large Array and at soft-x-ray wavelengths. The images at 20-cm and soft-x-ray wavelengths have nearly identical sizes and ellipsoidal shapes, with a linear extent of about 5 cm. This emission stretches between and across regions of opposite magnetic polarity in the underlying photosphere. Complete x-ray coronal loops can therefore be imaged at 20 cm, and the VLA maps describe the radio wavelength counterpart of x-ray coronal loops. x-ray spectral lines were used to obtain values of electron temperature and electron density averaged over the emitting area. The absence of detectable circular polarization is consistent with an optically thick plasma. The observed brightness temperature was roughly equal to the electron temperature of the coronal plasma. The VLA maps at 10 closely spaced frequencies between 1440 and 1720 MHz describe the same coronal loops or arcades of loops. A plot of the maximum-brightness temperature of these loops as a function of observing frequency exhibits a line-like feature with a central frequency of 1650 MHz and a half width of 80 MHz. This spectral feature is attributed to a thermal-cyclotron line and indicates that the optical depth of thermal gyro-resonance radiation must be greater than that of thermal bremsstrahlung at these frequencies.
Research Organization:
Tufts Univ., Medford, MA (USA). Dept. of Physics and Astronomy
OSTI ID:
6215592
Report Number(s):
AD-A-179650/7/XAB
Country of Publication:
United States
Language:
English

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Related Subjects

640104* -- Astrophysics & Cosmology-- Solar Phenomena
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANTENNAS
ATMOSPHERES
BREMSSTRAHLUNG
BRIGHTNESS
CYCLOTRON RESONANCE
DEPTH
DIMENSIONS
ELECTRICAL EQUIPMENT
ELECTROMAGNETIC RADIATION
ELECTRON DENSITY
ELECTRONIC EQUIPMENT
EMISSION SPECTRA
EQUIPMENT
IONIZING RADIATIONS
MAGNETIC FIELDS
OPTICAL PROPERTIES
PHOTOSPHERE
PHYSICAL PROPERTIES
POLARIZATION
RADIATIONS
RADIO EQUIPMENT
RADIO TELESCOPES
RADIOWAVE RADIATION
RESONANCE
SHAPE
SHORT WAVE RADIATION
SOFT X RADIATION
SOLAR ACTIVITY
SOLAR ATMOSPHERE
SOLAR CORONA
SPECTRA
STELLAR ATMOSPHERES
STELLAR CORONAE
TELESCOPES
X RADIATION