on the role of nonthermal electrons in EUV and X-ray line emissions from solar flares

1997 ◽  
Vol 18 (1) ◽  
pp. 57-71 ◽  
Author(s):  
Ranjna Bakaya ◽  
R. R. Rausaria
Keyword(s):  
Solar Flares ◽  
X Ray ◽  
Nonthermal Electrons

Role of non-thermal electrons on the generation of X-ray and EUV lines in solar flares

1988 ◽  
Vol 148 (1) ◽  
pp. 75-84 ◽  
Author(s):  
Ranjna Bakaya ◽  
R. R. Rausaria ◽  
P. N. Khosa
Keyword(s):  
Solar Flares ◽  
X Ray

Millimeter, Microwave, Hard X-Ray, and Soft X-Ray Observations of Energetic Electron Populations in Solar Flares

1994 ◽  
Vol 142 ◽  
pp. 599-610
Author(s):  
M. R. Kundu ◽  
S. M. White ◽  
N. Gopalswamy ◽  
J. Lim
Keyword(s):  
Solar Flares ◽  
Energetic Electron ◽  
Impulsive Phase ◽  
High Energy ◽  
X Rays ◽  
High Turnover ◽  
X Ray ◽  
Nonthermal Electrons ◽  
Time Profiles ◽  
Wavelength Emission

AbstractWe present comparisons of multiwavelength data for a number of solar flares observed during the major campaign of 1991 June. The different wavelengths are diagnostics of energetic electrons in different energy ranges: soft X-rays are produced by electrons with energies typically below 10 keV, hard X-rays by electrons with energies in the range 10-200 keV, microwaves by electrons in the range 100 keV-1 MeV, and millimeter-wavelength emission by electrons with energies of 0.5 MeV and above. The flares in the 1991 June active period were remarkable in two ways: all have very high turnover frequencies in their microwave spectra, and very soft hard X-ray spectra. The sensitivity of the microwave and millimeter data permit us to study the more energetic (>0.3 MeV) electrons even in small flares, where their high-energy bremsstrahlung is too weak for present detectors. The millimeter data show delays in the onset of emission with respect to the emissions associated with lower energy electrons and differences in time profiles, energy spectral indices incompatible with those implied by the hard X-ray data, and a range of variability of the peak flux in the impulsive phase when compared with the peak hard X-ray flux which is two orders of magnitude larger than the corresponding variability in the peak microwave flux. All these results suggest that the hard X-ray-emitting electrons and those at higher energies which produce millimeter emission must be regarded as separate populations. This has implications for the well-known “number problem” found previously when comparing the numbers of nonthermal electrons required to produce the hard X-ray and radio emissions.Subject headings: Sun: flares — Sun: radio radiation — Sun: X-rays, gamma rays

scholarly journals Plasma Processes in Solar Flares

1990 ◽  
Vol 142 ◽  
pp. 355-364
Author(s):  
V.M. Tomozov
Keyword(s):  
Solar Flares ◽  
Large Scale ◽  
Stark Effect ◽  
Active Regions ◽  
Theoretical Models ◽  
Radio Bursts ◽  
X Ray ◽  
Plasma Effects ◽  
Collective Plasma

A rationale is presented for a conception that appearance of flares in active regions is due to the interaction of large-scale convective elements. Such an interaction gives rise to shear motions in the vicinity of the inverse polarity line of the photospheric magnetic field which generate vortical motions leading to non-equilibrium state of the magnetic configuration. Modern concepts of manifestations of turbulent plasma processes are described in terms of theoretical models for solar flares. Plasma effects arising at propagation of electron beams and thermal fluxes in the solar atmosphere are considered. Their role in the interpretation of hard X-ray and type III radio bursts is pointed out. The role of the turbulent Stark effect for diagnostics of collective plasma processes in solar flares is emphasized.

The role of magnetic loops in solar flares

1991 ◽  
Vol 336 (1643) ◽  
pp. 389-400 ◽  
Keyword(s):  
Solar Flare ◽  
Spatial Structure ◽  
Spatial Resolution ◽  
Solar Flares ◽  
Solar Maximum ◽  
Magnetic Topology ◽  
Solar Maximum Mission ◽  
X Ray ◽  
Ultraviolet Observations

X -ray and ultraviolet observations of flares have provided much important information on their spatial structure and magnetic topology. The early observations from Skylab emphasized the role of simple loops and loop arcades, but later observations from the Solar Maximum Mission have greatly complicated this picture. Flares appear in a multitude of loops with complex spatial and temporal interrelations. In many cases, interactions between different loops appear to play a crucial role. The inferred magnetic topology of solar flares will be reviewed with emphasis on the implications for processes of energy release and transfer. It will be shown that the spatial resolution of the observations obtained so far is still inadequate for solving many basic questions of solar flare research.

scholarly journals THE ROLE OF KELVIN–HELMHOLTZ INSTABILITY FOR PRODUCING LOOP-TOP HARD X-RAY SOURCES IN SOLAR FLARES

2016 ◽  
Vol 833 (1) ◽  
pp. 36 ◽  
Author(s):  
Xia Fang ◽  
Ding Yuan ◽  
Chun Xia ◽  
Tom Van Doorsselaere ◽  
Rony Keppens
Keyword(s):  
Solar Flares ◽  
Helmholtz Instability ◽  
X Ray

scholarly journals Relation of Microwave Emission to X-Ray Emission from Solar Flares

1975 ◽  
Vol 68 ◽  
pp. 299-313 ◽  
Author(s):  
Tatsuo Takakura
Keyword(s):  
Solar Flares ◽  
Microwave Emission ◽  
Radio Sources ◽  
X Rays ◽  
Radio Emissions ◽  
Energetic Electrons ◽  
X Ray ◽  
Time Histories ◽  
Temporal And Spatial

Recent observations of impulsive microwave and hard X-ray emissions during the early phase of the flares are briefly reviewed in order to deduce the dynamics of energetic electrons consistently from two view points of the microwaves and X-rays. An emphasis is put on the necessity of distinction between temporal and spatial variations so far confused in the interpretation of the time histories of the X-ray and radio emissions. The role of plasma turbulence on the dynamics of the energetic electrons is shown to be important in deducing the model of X-ray and radio sources.

On the role of reverse current on the hard X-ray production in solar flares and time-lags between high- and low-energy photons

1992 ◽  
Vol 195 (2) ◽  
pp. 401-412
Author(s):  
Ranjana Bakaya ◽  
S. A. Chasti ◽  
R. R. Rausaria
Keyword(s):  
Solar Flares ◽  
Reverse Current ◽  
Low Energy ◽  
Time Lags ◽  
X Ray

Digital x-ray mapping of nanometer-size supported bimetallic catalysts

1988 ◽  
Vol 46 ◽  
pp. 530-531
Author(s):  
L. T. Germinario
Keyword(s):  
Background Radiation ◽  
Metal Cluster ◽  
Single Element ◽  
Beam Diameter ◽  
X Rays ◽  
X Ray ◽  
Major Interest ◽  
Induced Changes

Understanding the role of metal cluster composition in determining catalytic selectivity and activity is of major interest in heterogeneous catalysis. The electron microscope is well established as a powerful tool for ultrastructural and compositional characterization of support and catalyst. Because the spatial resolution of x-ray microanalysis is defined by the smallest beam diameter into which the required number of electrons can be focused, the dedicated STEM with FEG is the instrument of choice. The main sources of errors in energy dispersive x-ray analysis (EDS) are: (1) beam-induced changes in specimen composition, (2) specimen drift, (3) instrumental factors which produce background radiation, and (4) basic statistical limitations which result in the detection of a finite number of x-ray photons. Digital beam techniques have been described for supported single-element metal clusters with spatial resolutions of about 10 nm. However, the detection of spurious characteristic x-rays away from catalyst particles produced images requiring several image processing steps.

The role of silicon in forages: A quantitative X-Ray study

1987 ◽  
Vol 45 ◽  
pp. 416-417
Author(s):  
Janet H. Woodward ◽  
D. E. Akin
Keyword(s):  
Sodium Acetate ◽  
Dry Matter ◽  
Acetate Buffer ◽  
Plant Tissues ◽  
Sodium Acetate Buffer ◽  
X Ray ◽  
Dry Matter Digestibility ◽  
Percent Composition

Silicon (Si) is distributed throughout plant tissues, but its role in forages has not been clarified. Although Si has been suggested as an antiquality factor which limits the digestibility of structural carbohydrates, other research indicates that its presence in plants does not affect digestibility. We employed x-ray microanalysis to evaluate Si as an antiquality factor at specific sites of two cultivars of bermuda grass (Cynodon dactvlon (L.) Pers.). “Coastal” and “Tifton-78” were chosen for this study because previous work in our lab has shown that, although these two grasses are similar ultrastructurally, they differ in in vitro dry matter digestibility and in percent composition of Si.Two millimeter leaf sections of Tifton-7 8 (Tift-7 8) and Coastal (CBG) were incubated for 72 hr in 2.5% (w/v) cellulase in 0.05 M sodium acetate buffer, pH 5.0. For controls, sections were incubated in the sodium acetate buffer or were not treated.

Pathophysiological function of the mitochondria as a calcium reservoir: Quantitative x-ray microanalysis

1990 ◽  
Vol 48 (2) ◽  
pp. 164-165
Author(s):  
K. Teraoka ◽  
N. Kaneko ◽  
Y. Horikawa ◽  
T. Uchida ◽  
R. Matsuda ◽  
...  
Keyword(s):  
Bolus Injection ◽  
Contact Method ◽  
X Ray

The aim of this study was to elucidate the role of the mitochondria as a store of calcium(Ca) under the condition of pathophysiological Ca overload induced by a rise in extracellular Ca concentration and the administration of isoproterenol.Eight rats were employed, and hearts were perfused as in the Langendorff method with Krebs-Henseleit solution gassed with 95% O2 and 5% CO2. Tow specimens were perfused with 2mM Ca for 30 min, and 2 were perfused with 5.5 mM Ca for 20 min. 4 specimens were perfused with 2 mM Ca for 5 min, and of these 4, 2 were infused with 10-7 mM/kg/min. isoproterenol for 5 min, and 2 were given a bolus injection of 3 x 10-7 mM isoproterenol. After rapid-cryofixation by the metal-mirror contact method with a Reichert-Jung KF80/MM80, and cryosectioning at -160 to -180° C with a Reichert-Jung Ultracut Fc-4E, ultrathin specimens (100nm) were free-ze-dreid for several hours at 10-5 Torr in the JEOL FD 7000, and mitochondrial Ca was determined by quantitative x-ray micranalysis (JEOL 1200EX, LINK AN 10000S).

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