view Abstract Citations (28) References (17) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of solar flare transition zone plasmas from the Solar Maximum Mission Cheng, C. -C. ; Bruner, E. C. ; Tandberg-Hanssen, E. ; Woodgate, B. E. ; Shine, R. A. ; Kenny, P. J. ; Henze, W. ; Poletto, G. Abstract The spatial and temporal evolution of the Si IV and O IV intensity, density and mass motions in preflare and flare transition zone plasmas are studied for the case of the April 8, 1980 flare. It is found that: (1) the UV flare observed in the Si IV and O IV lines is unambiguously identified as occurring in a low-lying, preexisting transition zone loop which spanned the magnetic neutral line separating a larger leader spot and a newly emerged, isolated spot of opposite polarity; (2) at the onset of the flare, the easternmost footpoint, which was anchored in an isolated spot region of high longitudinal magnetic field gradient, showed sudden, impulsive brightening with large intensity increases; and (3) the release flare energy was transported by way of large-scale connecting field lines to other parts of the active region, producing the hot plasma and H-alpha kernels observed near the trailing spot. Publication: The Astrophysical Journal Pub Date: February 1982 DOI: 10.1086/159640 Bibcode: 1982ApJ...253..353C Keywords: Solar Flares; Solar Maximum Mission; Solar Wind; Solar X-Rays; H Alpha Line; Line Spectra; Oxygen Isotopes; Silicon Isotopes; Solar Magnetic Field; Solar Physics full text sources ADS |

Simultaneous observations of a solar limb flare in the X-ray and ultraviolet regions of the spectrum are presented. Temporal and spectral X-ray observations were obtained for the 25–300 keV range while temporal, spectral, and spatial X-ray observations were obtained for the 30–0.3 keV range. The ultraviolet observations were images with a 10″ spatial resolution in the lines of O v (Te ∼ 2.5 × 105 K) and Fe xxi (Te ∼ 1.1 × 107 K). The hard X-ray and O v data indicate that the impulsive phase began in the photosphere or chromosphere and continued for several minutes as material was ejected into the corona. Impulsive excitation was observed up to 30 000 km above the solar surface at specific points in the flare loop. The Fe xxi observations indicate a preheating before the impulsive phase and showed the formation of hot post-flare loops. This later formation was confirmed by soft X-ray observations. These observations provide limitations for current flare models and will provide the data needed for initial conditions in modeling the concurrent coronal transient.

view Abstract Citations (61) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spatial and temporal structures of impulsive bursts from solar flares observed in UV and hard X-rays Cheng, C. -C. ; Tandberg-Hanssen, E. ; Bruner, E. C. ; Orwig, L. ; Frost, K. J. ; Kenny, P. J. ; Woodgate, B. E. ; Shine, R. A. Abstract New observations are presented of impulsive UV and hard X-rays bursts in two solar flares obtained with instruments on Solar Maximum Mission. The UV bursts were observed in the Si IV and O IV emission lines, whose intensity ratio is density-sensitive. By comparing the spatially resolved Si IV/O IV observations with the corresponding hard X-ray observations, it is possible to study their spatial and temporal relationships. For one flare, the individual component spikes in the multiply peaked hard X-ray burst can be identified with different discrete Si IV/O IV flaring kernels of size 4 arcsec x 4 arcsec or smaller, which brighten up sequentially in time. For the other, many Si IV/O kernels, widely distributed over a large area, show impulsive bursts at the same time, which correlate with the main peak of the impulsive hard X-ray burst. The density of the flaring Si IV/O IV kernels is in the range from 5 x 10 to the 12th-13th/cu cm. Publication: The Astrophysical Journal Pub Date: August 1981 DOI: 10.1086/183619 Bibcode: 1981ApJ...248L..39C Keywords: Line Spectra; Solar Flares; Solar Spectra; Solar X-Rays; Spatial Resolution; Ultraviolet Spectra; Electron Energy; Emission Spectra; Light Curve; Oxygen Spectra; Silicon; Solar Maximum Mission; Spectrum Analysis; Solar Physics full text sources ADS |

view Abstract Citations (39) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Preliminary observations and results obtained with the ultraviolet spectrometer and polarimeter Tandberg-Hanssen, E. ; Cheng, C. C. ; Athay, R. G. ; Beckers, J. M. ; Brandt, J. C. ; Chapman, R. D. ; Bruner, E. C. ; Henze, W. ; Hyder, C. L. ; Gurman, J. B. Abstract New observation with the Ultraviolet Spectrometer and Polarimeter (UVSP) of a number of manifestations of solar activity obtained during the first three months of Solar Maximum Mission operations are presented. Attention is given to polarimetry in sunspots, oscillations above sunspots, density diagnostics of transition-zone plasmas in active regions, and the eruptive prominence - coronal transient link. Publication: The Astrophysical Journal Pub Date: March 1981 DOI: 10.1086/183496 Bibcode: 1981ApJ...244L.127T Keywords: Polarimeters; Solar Instruments; Solar Maximum Mission; Ultraviolet Spectrometers; Circular Polarization; Plasma Diagnostics; Solar Corona; Solar Prominences; Sunspots; Solar Physics full text sources ADS |

view Abstract Citations (29) References (13) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Observations of the 1980 April 30 limb flare by the ultraviolet spectrometer and polarimeter on the Solar Maximum Mission Woodgate, B. E. ; Shine, R. A. ; Brandt, J. C. ; Chapman, R. D. ; Michalitsianos, A. G. ; Kenny, P. J. ; Bruner, E. C. ; Rehse, R. A. ; Schoolman, S. A. ; Cheng, C. C. Abstract Observations of the M2 limb flare of 1980 April 30 by the ultraviolet spectrometer and polarimeter in the C IV 1548 A line are described and compared with observations from other SMM instruments and with ground-based H-alpha data. Events observed during the 18 minutes leading up to the flare impulsive phase include the filling of a small loop with material moving at about 20 km/s, followed by a rapid brightening in C IV, H-alpha, and hard X-rays, with a subsequent brightening of a higher set of loops. The rapid brightening appears to be at the junction of the small loop with the overlying magnetic structures, which suggests the flare may be caused by their interaction. Publication: The Astrophysical Journal Pub Date: March 1981 DOI: 10.1086/183497 Bibcode: 1981ApJ...244L.133W Keywords: Solar Flares; Solar Limb; Solar Magnetic Field; Solar Maximum Mission; Solar Spectra; Ultraviolet Astronomy; H Alpha Line; Polarimeters; Solar Instruments; Solar X-Rays; Ultraviolet Spectrometers; Solar Physics full text sources ADS |

We describe the Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission (SMM) spacecraft. The instrument, which operates in the wavelength range 1150 – 3600 Å, has a spatial resolution of 2–3 arc sec and a spectral resolution of 0.02 Å FWHM in second order. A Gregorian telescope, focal length 1.8 m, feeds a 1 m Ebert-Fastie spectrometer. A polarimeter comprising rotating Mg F2 waveplates can be inserted behind the spectrometer entrance slit and allows all four Stokes parameters to be determined. The observing modes include rasters, spectral scans, velocity measurements, and polarimetry. Finally, we present examples of initial observations made since launch.

Measurements of the radiative energy output of the solar flare of Sept. 5, 1973, over a wavelength range of more than ten decades, from below 1 A to above 1 m are presented. Observations of soft X-rays (0.5-20 A), XUV and EUV lines (171-1863 A) and EUV continua (1400-1960 A), H alpha radiation, visible lines and continua (3700-8700 A) and radio emission (centimeter to meter wavelengths) were obtained concurrently by Skylab and ground-based instruments. Estimates of power output at flare maximum are obtained for the observed wavelengths with uncertainty of at least half an order of magnitude, due to corresponding uncertainties in EUV and visible fluxes. Taking into account energy radiated at unobserved wavelengths and the characteristic time of the best-reduced data (the soft X-ray), calculations indicate a total radiated flare energy of approximately 4 x 10 to the 29th erg.