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  • 1
    Electronic Resource
    Electronic Resource
    A line identification list for the solar flare of 7 September, 1973 in the wavelength range 1335 Å–380 Å (1983)
    Springer
    Solar physics 89 (1983), S. 115-131 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A wavelength list is presented for the solar flare of 7 September, 1973 in the spectral range 1335 Å–380 Å. The ions observed suggest a range of temperatures in the flare plasma from 8 × 103 K to 107 K. This wavelength range contains many of the important electron density diagnostics lines for the solar transition zone and corona. The line list should also be of potential use in the identification and comparison with stellar spectra.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00211957
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  • 2
    Electronic Resource
    Electronic Resource
    Mgix and Sixi line ratios in the sun (1984)
    Springer
    Solar physics 94 (1984), S. 91-98 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New theoretical emission line ratios for the Be-sequence ions Mgix and Sixi are presented. A comparison with observational data for two solar flares and an active region loop obtained with the Harvard EUV spectrometer and NRL XUV spectroheliograph aboard Skylab reveals that these plasmas are in ionization equilibrium at coronal temperatures. Unfortunately most of the density diagnostics are not particularly useful under solar plasma conditions, as they vary only slightly over the electron density range 108–1013cm−3. However the Sixi ratioI(3 P e 2 -3 P o 2)/I(3 P o 1 –1 S e 0) is density sensitive in the range 108 to 1010cm−3, which is representative of electron densities found in solar active regions or small flares.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00154810
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  • 3
    Electronic Resource
    Electronic Resource
    Energetics of a double flare on November 8, 1980 (1985)
    Springer
    Solar physics 98 (1985), S. 141-158 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Here we complete an energy balance analysis of a double impulsive hard X-ray flare. From spatial observations, we deduce both flares probably occur in the same loop within the resolution of the data. For the first flare, the energy in the fast electrons (assuming a thick-target model) is comparable to the convective up-flow energy, suggesting that these are related successive modes of energy storage and transfer. The total energy lost through radiation and conduction, 2.0 × 1028 erg, is comparable to the energy in fast electrons 2.5 × 1028 erg. For the second flare, the energy in the fast electrons is more than one order of magnitude greater than the energy of the convective up-flow. Total energy losses are within a factor of two lower than the calculated fast electron energy. We interpret the observations as showing that the first flare occurred in a small loop with fast electrons heating the chromosphere and resulting in chromospheric evaporation increasing the density in the loop. For the second flare most of the heating occurred at the electron acceleration site. The two symmetrical components of the Ca xix resonance line and a high velocity down-flow of 115 km s −1 observed at the end of the second hard X-ray burst are consistent with the flare eruption (reconnection) region being high in the flare loop. The estimated altitude of the acceleration site is 5500 km above the photosphere.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00177204
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  • 4
    Electronic Resource
    Electronic Resource
    Ultraviolet radiation from stellar flares and the coronal X-ray emission for dwarf-Me stars (1985)
    [s.l.] : Nature Publishing Group
    Nature 313 (1985), S. 378-380 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] In a survey of X-ray fluxes from the Einstein satellite2, those for the dMe stars varied over three orders of magnitude. To investigate the relationship between this flux and flare activity, we compiled a list of stars (Table 1) for which both the flare-activity rate in the U band and the ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/313378a0
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  • 5
    Electronic Resource
    Electronic Resource
    Basic stellar parameter determination for active cool eclipsing binaries (1996)
    Springer
    Astrophysics and space science 236 (1996), S. 215-227 
    Details
    ISSN: 1572-946X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We examine procedures for the determination of reliable parameter sets characterizing stars in short period eclipsing binary systems of later dwarf, generally sunlike, spectral types. These stars have magnetodynamically active components and form a useful “extension to the solar laboratory”. Their much more rapid rotation than that of the Sun implies correspondingly enhanced indications of activity-particularly with relatively large maculation effects in broadband data. We concentrate on five such systems, for which we discuss new data and analyses-CG Cyg, ER Vul, YY Gem, BH Vir and UV Psc. Our main aim is to enable more reliable absolute comparisons between the basic properties of such stars and the Sun. Some indications of the ages of these binaries can also provide further pointers to the relative importance of different parameters (e.g. rotation, age, etc.), in determining stellar activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00645145
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  • 6
    Electronic Resource
    Electronic Resource
    Which size distribution is best for IRC +10°216? (1995)
    Springer
    Astrophysics and space science 224 (1995), S. 425-426 
    Details
    ISSN: 1572-946X
    Keywords: stars: IRC +10° 216 ; grain size distribution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A generalized two-streamed Eddington aproximation is applied to the problem of radiative transfer in a spherically symmetric dust shell. We investigate whether our technique allows us to draw conclusions about the size distribution of the grains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00667888
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  • 7
    Electronic Resource
    Electronic Resource
    An emission measure analysis of two sunspots observed by the UVSP instrument on the SMM spacecraft (1982)
    Springer
    Solar physics 81 (1982), S. 47-58 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The EUV observations from the SMM satellite of two sunspots are presented here. These observations show the sunspots (a) to be regions of lower intensity than the surrounding plage, contrary to that found by previous authors, and (b) to have line intensities which vary little over a period of several hours. An upper limit to mass flows of 2km s-1 is derived, indicating a relatively simple energy balance for the chromosphere-corona transition zone with thermal conduction being balanced by radiative losses. Electron densities derived from Niv to Civ line ratios imply electron pressures (log N eTe) of 15.0 to 15.3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00151978
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  • 8
    Electronic Resource
    Electronic Resource
    Theoretical Siiv line ratios compared to extreme ultraviolet solar observations (1988)
    Springer
    Solar physics 115 (1988), S. 229-234 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract New theoretical electron temperature sensitive emission line ratios in Siiv involving the 3d 2 D − 3p 2 P and 4s 2 S − 3p 2 P multiplets at ∼1125 and 816 Å, respectively, are derived using recent R-matrix electron excitation rate calculations. A comparison of these with observational data for a solar active region at the limb obtained with the Harvard S-055 spectrometer on board Skylab reveals that there is good agreement between theory and observation for ratios that include the 2 D 3/2, 5/2 − 2 P 3/2 transition at 1128.3 Å. This is in contrast to the findings of Keenan, Dufton, and Kingston (1986) and provides support for the atomic data adopted in the calculations. However, the 2 D 3/2 − 2 P 1/2 line at 1122.5 Å appears to be severely blended, as suggested previously by Burton and Ridgeley (1970) and Feldman and Doschek (1977), as it leads to electron temperature estimates that differ significantly from that expected in ionisation equilibrium. The fact that the I(1122.5 Å)/I(1128.3 Å) intensity ratios determined from several flare spectra are closer to theory than that for the active region indicates that the blending is probably due to species with relatively low ionization potentials, as noted by Flower and Nussbaumer (1975). Electron temperatures deduced for a sunspot are much lower than that predicted from ionisation balance calculations, in agreement with earlier results, and imply that a cooling flow may be present.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00148725
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  • 9
    Electronic Resource
    Electronic Resource
    Theoretical emission line strengths for Ov compared to EUV solar observations (1994)
    Springer
    Solar physics 150 (1994), S. 61-70 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract RecentR-matrix calculations of electron impact excitation rates in Ov are used to derive the emission line intensity ratios (in energy units) $$\begin{gathered} R_1 = I(2s2p^{ 3} P - 2p^{2 3} P)/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(761.1\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ R_2 = I(2s^{2 1} S_0 - 2s2p^{ 3} P_1 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(1218.4\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ ), \hfill \\ \end{gathered} $$ and $$R_3 = I(2s2p^{ 1} P_1 - 2p^{2 1} S_0 )/I(2s^{2 1} S_0 - 2s2p^{ 1} P_1 ) = I(774.5\mathop A\limits^ \circ )/I(629.7\mathop A\limits^ \circ )$$ as a function of electron temperature (T e) and density (N e). These results are presented as plots ofR 1 vsR 2, andR 1 vsR 3, which should allowboth N e andT e to be deduced for the Ov line emitting region of a plasma. Electron densities derived from the (R 1,R 2) and (R 1,R 3) diagrams in conjunction with observational data for several solar features obtained with the Harvard S-055 spectrometer on boardSkylab are found to be compatible, and in good agreement with values ofN e estimated from line ratios in species formed at similar electron temperatures to Ov. In addition, values ofT e determined from (R 1,R 2) and (R 1,R 3) are generally close to that expected theoretically. These results provide experimental support for the accuracy of the diagnostic calculations presented in this paper, and hence the atomic data used in their derivation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00712876
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  • 10
    Electronic Resource
    Electronic Resource
    A comparison of theoretical Sv emission line strengths with extreme ultraviolet observations of a sunspot (1990)
    Springer
    Solar physics 128 (1990), S. 345-351 
    Details
    ISSN: 1573-093X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Electron impact excitation rates for transitions in the S v ion, calculated with theR-matrix code, are used to derive the electron temperature sensitive emission line ratiosR 1 =I(854.8 Å)/I(786.9 Å),R 2 =I(852.2 Å)/I(786.9 Å),R 3 =I(849.2 Å)/I(786.9 Å), andR 4 =I(1199.1 Å)/I(786.9 Å), which are found to be significantly different from previous estimates. A comparison of the present results with observational data for a sunspot obtained with the Harvard S-055 spectrometer on boardSkylab reveals generally good agreement between theory and experiment, except in the case ofR 1, which is probably due to blending in the 854.8 Å feature. The possible effects of Lyman continuum absorption on the observed line ratios is briefly discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00838470
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