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 |

More than six hours after the two-ribbon flare of 21 May 1980, the hard X-ray spectrometer aboard the SMM imaged an extensive arch above the flare region which proved to be the lowest part of a stationary post-flare noise storm recorded at the same time at Culgoora. The X-ray arch extended over 3 or more arc minutes to a projected distance of 95 000 km, and its real altitude was most probably between 110 000 and 180 000 km. The mean electron density in the cloud was close to 109 cm−3 and its temperature stayed for many hours at a fairly constant value of about 6.5 × 106 K. The bent crystal spectrometer aboard the SMM confirms that the arch emission was basically thermal. Variations in brightness and energy spectrum at one of the supposed footpoints of the arch seem to correlate in time with radio brightness suggesting that suprathermal particles from the radio noise regions dumped in variable quantities into the low corona and transition layer; these particles may have contributed to the population of the arch, after being trapped and thermalized. The arch extended along the H∥ = 0 line thus apparently hindering any upward movement of the upper loops reconnected in the flare process. There is evidence from Culgoora that this obstacle may have been present above the flare since 15–30 min after its onset.

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.

Several solar flares have been observed from their onset in C IV λ 1548.2 and 1–8 Å X-rays using instruments aboard OSO-8. In addition, microwave and Hα flare patrol data have been obtained for this study. The impulsive brightening in C IV is frequently accompanied by redshifts, interpreted as downflows, of the order of 80 km s-1. The maximum soft X-ray intensity usually arrives several minutes after the maximum C IV intensity. The most energetic C IV event studied shows a small blueshift just before reaching maximum intensity, and estimates of the mass flux associated with this upflow through the transition-zone are consistent with the increase of mass in the coronal loops as observed in soft X-rays. This event had no observable microwave burst, suggesting that electron beams did not play a major role in the chromospheric and transition-zone excitation. Lastly, our observations suggest that the frequent occurrence of violent dynamical processes at the onset of the flare are associated with the initial energy release mechanism.

view Abstract Citations (19) References (15) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS OSO 8 observational limits to the acoustic coronal heating mechanism Bruner, E. C., Jr. Abstract An improved analysis of time-resolved line profiles of the C IV resonance line at 1548 A has been used to test the acoustic wave hypothesis of solar coronal heating. It is shown that the observed motions and brightness fluctuations are consistent with the existence of acoustic waves. Specific account is taken of the effect of photon statistics on the observed velocities, and a test is devised to determine whether the motions represent propagating or evanescent waves. It is found that on the average about as much energy is carried upward as downward such that the net acoustic flux density is statistically consistent with zero. The statistical uncertainty in this null result is three orders of magnitue lower than the flux level needed to heat the corona. Publication: The Astrophysical Journal Pub Date: July 1981 DOI: 10.1086/159040 Bibcode: 1981ApJ...247..317B Keywords: Line Spectra; Plasma Heating; Solar Corona; Solar Physics; Cross Correlation; Energy Transfer; Oso-8; Photons; Sound Waves; Solar Physics full text sources ADS |

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 |

A rocket borne experiment to measure the temperature structure of the inner solar corona via the doppler broadening of the resonance hydrogen Lyman-..cap alpha.. (lambda1216A) radiation scattered by ambient neutral hydrogen atoms was attempted during the 16 Feb 1980 solar eclipse. Two Nike-Black Brant V sounding rockets carrying instrumented payloads were launched into the path of the advancing eclipse umbra from the San Marco satellite launch platform 3 miles off the east coast of Kenya.

view Abstract Citations (83) References (11) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Steady flows in the solar transition region observed with SMM Gebbie, K. B. ; Hill, F. ; November, L. J. ; Gurman, J. B. ; Shine, R. A. ; Woodgate, B. E. ; Athay, R. G. ; Tandberg-Hanssen, E. A. ; Toomre, J. ; Simon, G. W. Abstract Steady flows in the quiet solar transition region have been observed with the Ultraviolet Spectrometer and Polarimeter experiment on the Solar Maximum Mission (SMM) satellite. The persistent vertical motions seen at disk center have spatial rms amplitudes of 1.4 km/s in the C II line, 3.9 km/s in Si IV, and 4.2 km/s in C IV. The amplitudes of the more horizontal flows seen toward the limb tend to be somewhat higher. Plots of steady vertical velocity versus intensity seen at disk center in Si IV and C IV show two distinct branches. Publication: The Astrophysical Journal Pub Date: December 1981 DOI: 10.1086/183705 Bibcode: 1981ApJ...251L.115G Keywords: Chromosphere; Satellite Observation; Solar Atmosphere; Solar Maximum Mission; Steady Flow; Ultraviolet Spectroscopy; Line Shape; Photosphere; Polarimeters; Solar Corona; Solar Limb; 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 |

The Ultraviolet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission spacecraft is described, including the experiment objectives, system design, performance, and modes of operation. The instrument operates in the wavelength range 1150–3600 Å with better than 2 arc sec spatial resolution, raster range 256 × 256 arc sec2, and 20 mÅ spectral resolution in second order. Observations can be made with specific sets of 4 lines simultaneously, or with both sides of 2 lines simultaneously for velocity and polarization. A rotatable retarder can be inserted into the spectrometer beam for measurement of Zeeman splitting and linear polarization in the transition region and chromosphere.

We now describe a new sounding rocket payload that has been developed for x-ray spectroscopic studies of the solar corona. The instrument incorporates a grazing incidence Rowland mounted grating spectrograph and an extreme off-axis parabolic sector telescope to isolate regions of the sun of order 1 X10 arc seconds in size. The focal surface of the spectrograph is shared by photographic and photoelectric detection systems, with the latter serving as a part of the rocket pointing system control loop. Fabrication and alignment of the optical system are based on high precision machining and mechanical metrology techniques. The spectrograph covers the 10 to 50 angstrom interval and has a resolution of 16 milliangstroms in the current version. Modifications planned for future flights will improve the resolution to around 5 milliangstroms, permitting line widths to be measured.