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  • Books
  • Other Sources  (12)
  • SOLAR PHYSICS  (12)
  • 1980-1984  (12)
  • 1984  (5)
  • 1982  (7)
  • 1
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    Flare build-up study - Homologous flares group. I (1984)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: Solar Maximum Mission observations have been used to study the origin and amount of energy, mechanism of storage and release, and conditions for the occurrence of solar flares, and some results of these studies as they pertain to homologous flares are briefly discussed. It was found that every set of flares produced 'rafales' of homologous flares, i.e., two, three, four, or more flares separated in time by an hour or less. No great changes in macroscopic photospheric patterns were observed during these flaring periods. A quantitative brightness parameter of the relation between homologous flares is defined. Scale changes detected in the dynamic spectrum of flare sites are in good agreement with a theoretical suggestion by Sturrock. Statistical results for different homologous flare active regions show the existence in homologous flaring areas of a 'pivot' of previous filaments interpreted as a signature of an anomaly in the solar rotation.
    Keywords: SOLAR PHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 7, 19
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  • 2
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    About the onsets of closely-consecutive homologous flares (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The onsets of closely consecutive homologous flares (CCHF), which are separated by less than 6 hours and most often by about 1 hour, are compared with that of isolated flares (no flare in the region half a day before). Isolated flares appear to be formed of two components, a surging arch and a flaring arch, while a set of CCHF may be composed of consecutive elementary flares or of a series of complex ones. It is shown that the onset of eruptive flare phenomena is not the same for an isolated event and for a member of CCHF (excluding the first) as found in H-alpha and EUV observations, and probably in X-ray observations also. It is suggested that a CCHF set would become a single flare with episodic enhancement of brightness by taking account of the common H-alpha behavior of surging and flaring arches as well as the EUV emission.
    Keywords: SOLAR PHYSICS
    Type: (ISSN 0273-1177)
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  • 3
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    Unusual coronal activity following the flare of 6 November 1980 (1982)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: The major two-ribbon flare that occurred on November 6, 1980 is discussed, using data from the hard X-ray imaging spectrometer aboard the SMM satellite. The post-flare X-ray arch and loops are analyzed, showing the flare characteristics, the coronal arch, the time variations of X-rays after the flare, and the time variation of the maximum intensity at the top of the coronal arch in the 3.5-5.5 keV range. A comparison is made with an earlier arch. The post-flare conronal brightness variations are discussed, including a correlation with a 169 MHz noise stomr, the absence of chromospheric excitation, the brightness and temperature of the X-ray arch, the locations of the brightenings, and the details of the first and fifth brightenings. Problems posed by the observations are discussed.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 80; Sept
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  • 4
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    A multiple type-II burst associated with a coronal transient and its MHD simulation (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A large coronal transient took place on May 8, 1981. The transient was related to an M7.7/2B flare and was associated with at least two coronal type-II bursts. The velocities of the type-II bursts were in the range 1100-1800 km/s, in excess of the transient velocity of 1000 km/s. Two dimensional positions of the type-II radio sources are available from both the Clark Lake and the Culgoora Radio Observatories. Two dimensional MHD simulations of the event are carried out, taking into account the observed velocity, position, and size of the type-II bursts. The multiple shocks observed during the event and their interaction are simulated, and results of the simulation are discussed.
    Keywords: SOLAR PHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 7 19
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  • 5
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    Magnetohydrodynamic modelling of interplanetary disturbances between the sun and earth (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: A time-dependent, nonplanar, two-dimensional magnetohydrodynamic computer model is used to simulate a series, separately examined, of solar flare-generated shock waves and their subsequent disturbances in interplanetary space between the sun and the earth's magnetosphere. The 'canonical' or ansatz series of shock waves include initial velocities near the sun over the range 500 to 3500 km/s. The ambient solar wind, through which they propagate, is taken to be a steady state homogeneous plasma (that is, independent of heliolongitude) with a representative set of plasma and magnetic field parameters. Complete sets of solar wind plasma and magnetic field parameters are presented and discussed. Particular attention is addressed to the MHD model's ability to address fundamental operational questions vis-a-vis the long-range forecasting of geomagnetic disturbances. These questions are: (1) will a disturbance (such as the present canonical series of solar flare shock waves) produce a magnetospheric and ionospheric disturbance, and, if so, (2) when will it start, (3) how severe will it be, and (4) how long will it last? The model's output is used to compute various solar wind indices of current interest as a demonstration of the model's potential for providing 'answers' to these questions.
    Keywords: SOLAR PHYSICS
    Type: AD-A162513 , AFGL-TR-85-0305 , Astrophysics and Space Science (ISSN 0004-640X); 105; 1 c
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  • 6
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    Observations of a post-flare radio burst in X-rays (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: More than six hours after the two-ribbon flare of May 21, 1980, the hard X-ray spectrometer aboard the SMM imaged an extensive arch above the flare region which was found to be the lowest part of a stationary post-flare noise storm recorded at the same time at Culgoora. 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 are seen as correlation in time with radio brightness, suggesting that suprathermal particles from the radio noise regions dumped in variable quantities onto the low corona and transition layer.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 75; Jan. 198
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  • 7
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    H-alpha and hard X-ray development in two-ribbon flares (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Morphological features of two-ribbon flares have been studied, using simultaneous ISEE-3 hard X-ray records and high-resolution Big Bear H-alpha movies for more than 20 events. Long-lasting and complex hard X-ray bursts are almost invariably found associated with flares of the two-ribbon type. At least three events are found, namely March 31, 1979, April 10, 1980, and July 1, 1980, where the occurrence of individual spikes in hard X-ray radiation coincides with suddenly enhanced H-alpha emission covering the sunspot penumbra. There definitely exist important (greater than or equal to 1 B) two-ribbon flares without significant hard X-ray emission.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 90; 331-341
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  • 8
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    A new class of solar burst with MM-wave emission but only at the highest frequency (90 GHz) (1984)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: High sensitivity and high time resolution solar observations at 90 GHz (lambda = 3.3 mm) have identified a unique impulsive burst on May 21, 1984 with emission that was more intense at this frequency than at lower frequencies. The first major time structure of the burst was over 10 times more intense at 90 GHz than at 30 GHz, 7 GHz, or 2.8 GHz.Only 6 seconds later, the 30 GHz impulsive structures started to be observed but still with lower intensity than at 90 GHz. Hard X-ray time structures at energies above 25 keV were almost identical to the 90 GHZ structures (to better than one second). All 90 GHz major time structures consisted of trains of multiple subsecond pulses with rise times as short as 0.03 sec and amplitudes large compared to the mean flux. When detectable, the 30 GHz subsecond pulses had smaller relative amplitude and were in phase with the corresponding 90 GHz pulses.
    Keywords: SOLAR PHYSICS
    Type: NASA-TM-87369 , NAS 1.15:87369 , INPE-3241-PRE/587
    Format: application/pdf
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  • 9
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    EUV arcades - Signatures of filament instability (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The present investigation is based on the EUV observations from the HCO spectroheliometer aboard Skylab. These observations provide a great deal of information on coronal structures. The investigation is concerned with the EUV corona around active region filaments. One of its goals is to define the geometry and temperature distribution around those filaments which appear to be 'stable' (lifetimes equal to or greater than 2 days). The second goal is to study time changes in structures associated with other filaments which are 'unstable'. It is pointed out that the filaments and associated EUV loops reported in this investigation are not flare-related. The data of primary interest are those of Sept. 5, 1973, for which there exist simultaneous EUV and H-alpha filtergrams for the active region McMath 12510. It is found that active region filaments lie within channels of low emissivity in EUV lines formed above 1.5 x 10 to the 6th K.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 81; Nov. 198
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  • 10
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    Study of the post-flare loops on 29 July 1973. IV - Revision of T and n sub e values and comparison with the flare of 21 May 1980 (1982)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: Revised temperature and density estimates are provided in a synthesis of previous studies of the two-ribbon solar flare of July 29, 1973 and results are compared with observations of a similar event by the Solar Maximum Mission on May 21, 1980. Photographs taken through X ray filters permitted determination of the spatial distribution of temperature and density in the loop system and variations over time. The entire growth process of the flare is detailed, including the magnetic field configurations and the enlargement of the Halpha flare ribbon separation distance. The temperature is revised to 8.8 million K during maximum soft X ray emission and 6.8 million K at the appearance of the last Halpha loops. The 1973 flare is noted to have occurred in an old, decaying spotless region, producing higher loops at lower density than the 1980 flare, which displayed ribbons imbedded in a sunspot group.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics; 78; June 198
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