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  • SOLAR PHYSICS  (18)
  • Corotating high-speed streams  (1)
  • 1
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    Accelerated particles in solar flares (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: The variety of accelerated particle phenomena in solar flares is reviewed, including particle observation in interplanetary space and gamma-ray, neutron, hard X-ray, and radio emissions. It is emphasized that a significant or perhaps even large fraction of the total solar-flare energy is in accelerated particles. It is pointed out that the majority of the particles that produce impulsive flare phenomena remain trapped at the sun, probably due to confinement in the flaring magnetic loops. Gamma-ray observations are used to calculate the current rate of irradiation of the sun by MeV protons accelerated in solar flares. The current number of escaping protons is compared with irradiation rates of meteorites implied by observations of isotopic anomalies, and it is found that, except for the Ne-21 anomaly, enhanced proton irradiations from the ancient sun could not have been responsible for the observed isotopic anomalies.
    Keywords: SOLAR PHYSICS
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  • 2
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    Flare energetics (1986)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: In this investigation of flare energetics, researchers sought to establish a comprehensive and self-consistent picture of the sources and transport of energy within a flare. To achieve this goal, they chose five flares in 1980 that were well observed with instruments on the Solar Maximum Mission, and with other space-borne and ground-based instruments. The events were chosen to represent various types of flares. Details of the observations available for them and the corresponding physical parameters derived from these data are presented. The flares were studied from two perspectives, the impulsive and gradual phases, and then the results were compared to obtain the overall picture of the energics of these flares. The role that modeling can play in estimating the total energy of a flare when the observationally determined parameters are used as the input to a numerical model is discussed. Finally, a critique of the current understanding of flare energetics and the methods used to determine various energetics terms is outlined, and possible future directions of research in this area are suggested.
    Keywords: SOLAR PHYSICS
    Type: Energetic Phenomena on the Sun: The Solar Maximum Mission Flare Workshop. Proceedings; 20 p
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  • 3
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    Multiwavelength analysis of a well observed flare from SMM (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of an M 1.4 flare which began at 17:00 UT on November 12, 1980, are presented and analyzed. Ground based H-alpha and magnetogram data have been combined with EUV, soft and hard X-ray observations made with instruments on-board the Solar Maximum Mission satellite. The preflare phase was marked by a gradual brightening of the flare site in O v and the disappearance of an H-alpha filament. Filament ejecta were seen in O v moving southward at a speed of about 60 km/s, before the impulsive phase. The flare loop footpoints brightened in H-alpha and the Ca XIX resonance line broadened dramatically 2 min before the impulsive phase. Nonthermal hard X-ray emission was detected from the loop footpoints during the impulsive phase, while during the same period blue-shifts corresponding to upflows of 200-250 km/s were seen in Ca XIX. Evidence was found for energy deposition in both the chromosphere and corona at a number of stages during the flare. Two widely studied mechanisms for the production of the high temperature soft X-ray flare plasma in the corona are considered, i.e. chromospheric evaporation, and a model in which the heating and transfer of material occurs between flux tubes during reconnection.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 99; 167-188
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  • 4
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    Initial phase of chromospheric evaporation in a solar flare (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Attention is given to the initial phase of chromospheric evaporation in the solar flare observed by the Solar Maximum Mission's Hard X-ray Imaging Spectrometer, on May 21, 1980. Images of the flaring region in the 3.5-8.0 and 16-30 keV energy bands indicate that both the soft and hard X-ray emissions are localized near the footpoints early in the event, while they are weaker from the rest of the flaring loop system; this implies that there is no heating taking place at the top of the loops, while energy is primarily deposited at their base. Observations of the energy deposition in the chromosphere by electrons accelerated in the flare region to energies above 25 keV furnish further support for an interpretation of plasma upflows as the mechanism responsible for the formation of the soft X-ray flare, identified with chromospheric evaporation.
    Keywords: SOLAR PHYSICS
    Type: Solar Physics (ISSN 0038-0938); 96; 129-142
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  • 5
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    The development and cooling of a solar limb-flare (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Observations of a flare that began in soft X-rays at 20:37 UT on April 12, 1980 at the west limb of the sun are discussed. The observations of the flare and postflare loops are first described, and the Solar Maximum Mission data are interpreted in terms of the temperature, density, and geometry of the emitting regions. The observed postflare cooling time is compared with that expected from radiation, conduction, and enthalpy flux. The loop model is discussed, and the observed events are compared with other proposed models.
    Keywords: SOLAR PHYSICS
    Type: Royal Astronomical Society, Monthly Notices (ISSN 0035-8711); 210; 443-462
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  • 6
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    Homologous flares and the evolution of NOAA Active Region 2372 (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A detailed record of the evolution of NOAA Active Region 2372 has been compiled by the FBS Homology Study Group. It was one of the most prolific flare-producing regions observed by SMM. The flares occurred in distinct stages which corresponded to particular evolutionary phases in the development of the active region magnetic field. By comparison with a similar but less productive active region, it is found that the activity seems to be related to the magnetic complexity of the region and the amount of shear in the field. Further, the soft X-ray emission in the quiescent active region is related to its flare rate. Within the broader definition of homology adopted, there was a degree of homology between the events within each stage of evolution of AR2372.
    Keywords: SOLAR PHYSICS
    Type: Advances in Space Research (ISSN 0273-1177); 4; 7 19; 23-26
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  • 7
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    The starting conditions for an optically small solar gamma ray flare (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It is suggested that optically small gamma-ray flares result from gradual pre-flare acceleration of protons over approximately 1,000 s by a series of magnetohydrodynamic shocks in the low corona. A fraction of the accelerated protons are trapped in the corona where they form a seed population for future acceleration. If the shock acceleration is sufficiently rapid proton energies may exceed the gamma-ray production threshold and trigger gamma-ray emission. This occurs without the total flare energy being necessarily large. Magnetic field geometry is an important parameter.
    Keywords: SOLAR PHYSICS
    Type: SH-1.3-2 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 82-85; NASA-CP-2376-VOL-4
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  • 8
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    A dominant role for protons at the onset of solar flares (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: It is suggested that recent observations have cast considerable doubt on the generally accepted explanation that non-thermal electron beams transfer most of the flare energy during the onset of solar flares. It is argued that non-thermal protons in the energy region 100 to 1000 keV are a more probable energy transfer mechanism. An important consequence of this hypothesis is that the hard X-ray burst must be thermal.
    Keywords: SOLAR PHYSICS
    Type: SH-1.2-13 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 70-73; NASA-CP-2376-VOL-4
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  • 9
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    Spectral and spatial properties of solar microflares (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Solar microflares are studied using both hard ( 28 keV) and soft (3.5 to 8.0 keV) X-ray observations. The soft X-ray events have durations 3 m at 0.1x maximum intensity, and typically have similar rise and decay times. The fastest decay observed was 15 s (1/e). Soft and hard X-ray intensities are uncorrelated. The events are very compact, consistent with a projected area approximately 8 x 8 inches. They are normally not associated with H alpha or type 3 emissions and their time profiles suggest a thermal origin at the top of the chromosphere. If the primary energy release site is in the corona, an energy transfer agent consistent with the observations is a non-thermal proton beam.
    Keywords: SOLAR PHYSICS
    Type: SH-1.2-4 , 19th Intern. Cosmic Ray Conf - Vol. 4; p 38-41; NASA-CP-2376-VOL-4
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  • 10
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    Observational evidence for thermal wave fronts in solar flares (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Images in 3.5-30 keV X-rays obtained during the first few minutes of seven solar flares show rapid motions. In each case X-ray emission first appeared at one end of a magnetic field structure, and then propagated along the field at a velocity between 800 and 1700 km/s. The observed X-ray structures were 45,000-230,000 km long. Simultaneous H-alpha images were available in three cases; they showed brightenings when the fast-moving fronts arrived at the chromosphere. The fast-moving fronts are interpreted as electron thermal conduction fronts since their velocities are consistent with conduction at the observed temperatures of 1-3 x 10 to the 7th K. The inferred conductive heat flux of up to 10-billion ergs/s sq cm accounts for most of the energy released in the flares, implying that the flares were primarily thermal phenomena.
    Keywords: SOLAR PHYSICS
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 288; 401-409
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