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1.
P. Pant 《Astrophysics and Space Science》1993,209(2):297-306
Sudden phase anomalies (SPA's) observed in the phase of GBR 16 kHz VLF signals during the years 1977 to 1983 have been analysed in the light of their associated solar X-ray fluxes in the 0.5–4 Å and 1–8 Å bands. An attempt has been made to investigate the solar zenith angle () dependence of the integrated solar X-ray flux for producing SPA's. It is deduced from the observations for < 81° that the phase deviation increases linearly as a whole with increasing solar X-ray fluxes in these two bands. The threshold X-ray flux needed to produce a detectable SPA effect has been estimated to be 1.6 × 10–4 ergcm–2 s–1 and 1.8 × 10–3 ergcm–2 s–1 in the 0.5–4 Å and 1–8 Å bands, respectively. For both bands the average cross section for all atmospheric constituents at a height of 70 km is almost equal to the absorption cross section for the 3 Å X-ray emission. 相似文献
2.
David D. Meisel 《Solar physics》1968,5(4):575-587
Semi-quantitative reports of shortwave radio reception during the 12 November 1966 total solar eclipse have been used to determine the characteristics of a major source of D layer ionization. An effective electron depletion coefficient of 1.2 × 10–2 sec–1 was found empirically and used to reduce the data. Analysis of the radio absorption shows the source was located near heliographic coordinates, B = +7°, L = 340° and was probably less than 0.5 of arc in diameter. At the time of the eclipse, the source accounted for 40% of the radio absorption on a single, vertical pass through the D layer. Preoccultation behavior of the signal strength is interpreted by assuming a portion of the source X-ray flux was reflected at grazing incidence from the limb of moon. For point sources, such reflections have specific chromatic characteristics which were used to derive a crude source spectrum in the 3–140 Å range. X-ray absorption edges of N, O, Na, Be, and possible Mg, Ar, Ne, Ca, and K arising from the terrestrial atmosphere have been identified. A source temperature approximately twice that of the rest of the corona is indicated. 相似文献
3.
A. Sauval 《Solar physics》1968,3(1):89-105
In order to obtain a better agreement between observed and computed values of the solar intensity, an improved temperature distribution is deduced for the range 0.02<0< 10. The intensity observations here considered refer to the wavelength region between 1980 and 129 500, and the center-limb variations generally go down to cos = 0.1. The improved model, given in Figure 4 and Table II, differs rather little from the Utrecht 1964 model, used here as a reference.It appears necessary to introduce an empirical correction function to be applied to the continuous absorption coefficient. This function was derived for the spectral region between 2000 and 130000 Å; it is shown in Figure 5.Furthermore, an extension of the model (1.10–7<0< 2.10–2) is deduced (see Table III and Figure 8), which reasonably well represents the observations of the ultraviolet solar flux (
900–1700 Å). 相似文献
4.
R. Brajša S. Pohjolainen V. Ruždjak T. Sakurai S. Urpo B. Vršnak H. Wöhl 《Solar physics》1996,163(1):79-91
Measurements of the Sun in the near-infrared He i 10830 Å absorption line were performed using the echelle spectrograph with a dispersion of 6.71 mÅ per pixel at the Vacuum Tower Telescope (German Solar Telescopes, Teide Observatory, Izaña, Tenerife, Spain) on May 26, 1993. These measurements were compared with full-disc soft X-ray images of the Sun (Japanese solar satellite Yohkoh), full-disc solar images in H (Big Bear Solar Observatory), full-disc solar images in the He i 10830 Å line (National Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at 37 GHz (Metsähovi Radio Research Station). In the He 10830 Å line the Sun displays a limb darkening similar to that in the visible part of the spectrum. Active regions and H filaments show a strong absorption in the He 10830 Å line, whereas the absorption is weak in coronal holes. 相似文献
5.
Carole Jordan 《Solar physics》1967,2(4):441-450
The relative intensity of two Ci lines at 1993.6 Å and 1657.4 Å, observed in the limb spectrum of the sun, is a factor 2.6 × 103 larger than that expected if both lines were optically thin. It is shown that the observed intensity ratio may be explained in terms of the transfer of photons from 1657.4 Å to 1993.6 Å due to a large optical depth in the line at 1657.4 Å. The observed upper limit on the relative intensity of two further lines at 1992.0 Å and 1657.0 Å has been used to show that the line at 1993.6 Å is optically thin. Hence it is shown that (1657.4 Å) = 1300, and (1993.6 Å) = 0.44. These values provide an independent evaluation of optical depths against which chromospheric models may be checked. Assuming a mean temperature of T
e = 8000 °K, and a mean scale height of 350 km, the optical depths lead to a mean hydrogen-particle density of N (H) = 1.4 × 1012 cm–3. 相似文献
6.
This study is based on a set of ten solar rocket spectra well exposed for photometry photographed on July 27, 1966 by Purcell, Snider, and Tousey.The photometry of the far UV continuum illustrates the transition of the solar temperature minimum at 1700 Å in the solar spectrum - (a) the continuum intensity decreases by 30–50% between 1700 Å and the1
D limit of silicon at 1682 Å, and (b) the equivalent brightness temperature shows minimum values throughout the spectral range 1540–1682 Å, which average just under 4700 ± 100K.The minimum UV brightness temperature is 300K higher than the far infrared measurement of the solar minimum temperature, and possible reasons for this are discussed.Brightness temperatures measured in prominent CO band heads and in the aluminum 1937 Å auto-ionization line also are given. 相似文献
7.
Pierre Kaufmann 《Solar physics》1968,4(1):58-66
A strong S-component of solar radiation was identified during the total solar eclipse of November 12, 1966. Its characteristics, as measured at 4.28 cm, were studied in terms of flux and polarization, and its spectral features were derived by the use of data from other observatories. The whole source presented approximately the typical characteristics suggested by some authors in the last few years, and further it has been shown that it could be resolved into at least two enhanced regions, one showing unpolarized radiation with a brightness temperature T
b 1.2 × 106 °K, and the other showing 50% of left-handed circularly polarized radiation, with T
b 0.7 × 106 °K. The source's overall characteristics favour the presence of non-thermal absorption at the emitting regions. 相似文献
8.
Keenan F.P. Pinfield D.J. Mathioudakis M. Aggarwal K.M. Thomas R.J. Brosius J.W. 《Solar physics》2000,197(2):253-262
Theoretical electron density sensitive emission line ratios involving a total of eleven 2s
22p
2–2s2p
3 transitions in Sxi between 187 and 292 Å are presented. A comparison of these with solar active region observations obtained during rocket flights by the Solar EUV Rocket Telescope and Spectrograph (SERTS) reveals generally good agreement between theory and experiment. However, the 186.87 Å line is masked by fairly strong Fexii emission at the same wavelength, while 239.83 Å is blended with an unknown feature, and 285.58 Å is blended with possibly Niv 285.56 Å. In addition, the 191.23 Å line appears to be more seriously blended with an Fexiii feature than previously believed. The presence of several new Sxi lines is confirmed in the SERTS spectra, at wavelengths of 188.66, 247.14 and 291.59 Å, in excellent agreement with laboratory measurements. In particular, the detection of the 2s
22p
2
3
P
1 –2s2p
3
3
P
0,1 transitions at 242.91 Å is the first time (to our knowledge) that this feature has been identified in the solar spectrum. The potential usefulness of the Sxi line ratios as electron density diagnostics for the solar transition region and corona is briefly discussed. 相似文献
9.
Two spectra of the ultra-violet nightglow from 1900 Å to 3400 Å have been recorded by a fast wide-field spectrograph during balloon flights from Aire sur Adour, France on 15 September, 1969 and on 5 October, 1970. These two spectra are composed of theOi line at 2972 Å, of the molecular oxygen Herzberg band systemA
3
u
+
X
3
g
–
and of a molecular band system that seems to belong to the NO SystemX
2 C
2
X
+, situated at 1991 ű4 Å, 2060 ű4 Å and 2136 ű4 Å. Around 2540 Å, there is absorption by ozone at the altitudes at which the spectra were recorded (35 km and 40 km). We present our calculated value of ozone absorption at 35 km, and the zenith-horizon variation of the nightglow emission. 相似文献
10.
Six-color ultraviolet light curves of the complex eclipsing binary system Lyr were obtained with the OAO-2 Wisconsin Experiment Package. The filters had a typical width at half maximum of 150 to 200 Å and centered at 1430, 1550, 1910, 2460, 2980 and 3320 Å. The most striking characteristics of the ultraviolet light curves are that the secondary minimum deepens at shorter wavelengths. This indicates that we arenot observing the eclipse effect of two stars having roughly a Planckian distribution of energy. In combination with the high resolution far ultraviolet spectra of Lyr recently obtained withCopernicus (OAO-3) Princeton Telescope Spectrometer, it is concluded that the far ultraviolet light curves are dominated by emission from the high temperature gas surrounding the binary system. The ultraviolet observations with OAO-2 andCopernicus are consistent with a model in which the enigmatic secondary component involves a gravitationally collapsed object, i.e., a black hole; however, alternative models are also admissible. 相似文献
11.
This paper deals with molecular clouds discovered in the absorption spectra (z=2–3) of distant quasars. It is argued that these clouds belong to the gaseous subsystems of young galaxies. We estimate the gas concentration to ben<104 cm–3 in the cloud observed in the direction of the quasar PHL957. It is shown that this cloud is exposed to ultraviolet radiation. The UV-energy flux does not exceed the value typical for our Galaxy by an order of magnitude (F2×10–6 ergs cm–2 s–1 Å–1 at =2000 Å). The mechanisms maintaining the thermal balance in this cloud are discussed. 相似文献
12.
From 17 through 21 April 1967, an international study week was held in the Bilderberg near Arnhem, Netherlands, with the aim of obtaining an internationally acceptable model of the solar photosphere and low chromosphere. It was found that such a model, based on observed intensities and center-to-limb observations of the solar continuous spectrum, could indeed be established. This model, henceforth called the Bilderberg Continuum Atmosphere (BCA), is shown in Table I, which gives the temperature, gas and electron pressures, and other data as functions of the continuous optical depth at 5000 Å between 5000 = 10–7 and 25. The model is characterized by a flat temperature minimum of 4600 °K between 5000 10–2 to 10–4. The model is homogeneous, and in hydrostatic equilibrium. A hydrogen-helium ratio of 10 has been assumed.Much divergence remains in the interpretation of line-profile observations with regard to the establishment of a photospheric model (Section 4). It proved to be as yet impossible to obtain reliable information on the variation with depth of the following functions: temperature fluctuations, turbulence velocities, convective velocities, and vibrational velocity amplitudes (Section 5). Provisionally, it is assumed that
macro = 2 km/sec and
micro = 1 km/sec, isotropic and independent of depth. 相似文献
13.
New R-matrix calculations of electron impact excitation rates in Caxv are used to derive theoretical electron density diagnostic emission line intensity ratios involving 2s
22p
2–2s2p
3 transitions, specifically R
1=I(208.70 Å)/I(200.98 Å), R
2=I(181.91 Å)/I(200.98 Å), and R
3=I(215.38 Å)/I(200.98 Å), for a range of electron temperatures (T
e=106.4–106.8 K) and densities (N
e=109–1013 cm–3) appropriate to solar coronal plasmas. Electron densities deduced from the observed values of R
1, R
2, and R
3 for several solar flares, measured from spectra obtained with the Naval Research Laboratory's S082A spectrograph on board Skylab, are found to be consistent. In addition, the derived electron densities are in excellent agreement with those determined from line ratios in Caxvi, which is formed at a similar electron temperature to Caxv. These results provide some experimental verification for the accuracy of the line ratio calculations, and hence the atomic data on which they are based. A set of eight theoretical Caxv line ratios involving 2s
22p
2–2s2p
3 transitions in the wavelength range 140–216 Å are also found to be in good agreement with those measured from spectra of the TEXT tokamak plasma, for which the electron temperature and density have been independently determined. This provides additional support for the accuracy of the theoretical line ratios and atomic data. 相似文献
14.
We obtained time-sequence spectroscopic observations in (Fe x) 6374 Å and (Fe xiv) 5303 Å lines successively with the 25-cm coronagraph, and narrow-band and Doppler images in 5303 Å line by the 2-D 10-cm Doppler coronagraph NOGIS at the Norikura Solar Observatory, of a coronal region for about 7 h on 9 19–20, 2001. The raster scans were obtained with a quasi-periodicity of about 14 min and NOGIS obtained the images with an interval of about 1 min. The coronal region observed showed the formation of a coronal loop by a high-speed surge in the 6374 Å line rising from one of the footpoints of the loop. Off the limb spectroscopic observations in the 6374 Å line showed large velocities along the line of sight and vertical to the solar limb at the time of formation of the loop. The 5303 Å line observations showed negligible line-of-sight velocities and low vertical velocities when compared to those in the 6374 Å line. A hump in the intensity plots in 5303 Å with height appears to move up with respect to the solar limb with an average velocity of 4km s–1. The FWHM of the 6374 Å showed a much smaller value of about 0.7 Å near the foot point as compared to a value of 1.2 Å at larger heights at the beginning of observations. Later as the loop developed, the FWHM of 6374 Å line showed a gradual decrease along the loop up to 70 from the limb, reached a minimum value of about 0.5 Å and then increased with height during the formation of the loop; this trend lasted for about 2 h. About 3 h after the beginning of the formation of the loop, the FWHM of 6374 Å emission line showed normal values and normal rate of increase with height with some fluctuations. The FWHM of the 5303 Å line did not show such variations along the loop and showed normal decrease in FWHM with height found earlier (Singh et al., 2003a). These observations suggest that a relatively cooler plasma at a temperature of about 0.7 MK or less (corresponding to minimum value of FWHM of 0.5 Å) was ejected from the transition region with a large velocity of about 48km s–1, heated up in the corona by some process and formed a coronal loop with a height of about 200 above the limb that had lifetime greater than 4 h. It appears that the plasma moved from one of the footpoints and the loop was formed by evaporation of chromospheric plasma. No large-scale brightening and H flare were observed in this region during the observational period of 7 h.On leave from Indian Institute of Astrophysics, Bangalore 560034, India. 相似文献
15.
Takara Nishikawa 《Solar physics》1984,93(1):37-51
The weakening of EUV line emission due to continuum absorptions of neutral hydrogen and neutral helium is investigated to examine its wavelength-dependence. After convolving the intensities predicted from multilevel calculations over an instrumental profile, we found a systematic, linear weakening for lines shortward of 912 Å, which can be attributed to Lyman continuum absorption in the cool chromospheric cloud. The degree of the weakening at the quiet Sun seems to be constant in the temperature range of 4.3 < log T < 5.4. We also find that the lines shortward of 504 Å are somewhat weakened by He i continuum absorption. From the comparison of both weakenings the temperature of the absorber is estimated to be rather low (T
e 7 × 103 K). 相似文献
16.
The diffuse far UV radiation ( 1350–1480 Å) observed in the sky region ofl
II180°, 0°b
II40° is analyzed in connection with the distributions of stars and dust grains as well as with optical properties of grains. Its intensity (starlight+scattered light) is about 6×10–7 erg cm–2 sec–1 sr–1 Å–1 in the direction ofb
II0° andl
II180°. The latitude dependence of the intensity is in approximate agreement with the plane parallel slab model of the galaxy with a reasonable set of parameters. The interstellar scattering gives an albedo close to unity and forward phase function of about 0.6, which are not inconsistent with the model of interstellar grains of Wickramasinghe. The upper limit of the extragalactic UV is 2×10–8 erg cm–2 sec–1 sr–1 Å–1 in the same region of wave-length. 相似文献
17.
Some weak unidentified solar photospheric lines in the wavelength range: (3400–3465) Å may be due to PH lines of the (0, 0) band of the PH(A
3
i
- X
3 -)system. These faint PH molecular lines have resulted an excitation temperature of the order of 4500 K. Using experimental lifetime data for PH in the A
3
i
state, an absorption oscillator strength f
00 = 0.0075 is derived for the 3410 Å band of the PH (A
3
i
- X
3 -)system. Accurate line positions, oscillator strength and transition probability for the 4.4 fundamental rotation-vibration band of the PH molecule are obtained. A comparison of positions of some lines of the 4.4 band with those obtained on new tracings of high resolution solar spectra shows many coincidences with weak solar lines. 相似文献
18.
Yu. I. Grineva V. I. Karev V. V. Korneev V. V. Krutov S. L. Mandelstam L. A. Vainstein B. N. Vasilyev I. A. Zhitnik 《Solar physics》1973,29(2):441-446
Results are given of the detailed analysis of fourteen Fe xxv-xxiii lines ( = 1.850–1.870 Å) in the spectra of a solar flare on 16 Nov. 1970. The spectra were obtained with a resolution of about 4 × 10–4 Å, which revealed lines not previously observed and allowed the measurement of line profiles. The measured values of the wavelengths and emission fluxes are presented and compared with theoretical calculations. The analysis of the contour of the Fe xxv line ( = 1.850 Å) leads to the conclusion that there is unidirectional macroscopic gas motion in the flare region with the velocity (projection on the line of sight) ± 90 km s–1.Measurements of the 8.42 Å Mg xii and 9.16 Å Mg xi lines in the absence of solar flares indicate prolonged existence of active regions on the solar disk with T
e = 4–6 × 106K and emission measure ME 1048 cm–3. The profile of the Mg xii line indicates a macroscopic ion motion with a velocity up to 100 km s–1. 相似文献
19.
Spectroheliograms obtained in extreme ultraviolet (EUV) lines and the Lyman continuum are used to determine the rotation rate of the solar chromosphere, transition region, and corona. A cross-correlation analysis of the observations indicates the presence of differential rotation through the chromosphere and transition region. The rotation rate does not vary with height. The average sidereal rotation rate is given by (deg day–1) = 13.46 - 2.99 sin2
B where B is the solar latitude. This rate agrees with spectroscopic determinations of the photospheric rotation rate, but is slower by 1 deg day–1) = 13.46 - 2.99 sin2 than rates determined from the apparent motion of photospheric magnetic fields and from the brightest points of active regions observed in the EUV. The corona does not clearly show differential rotation as do the chromosphere and transition region. 相似文献
20.
Stuart D. Jordan 《Solar physics》1977,51(1):51-59
Calculations performed with several models of the solar chromosphere support Ulmschneider's conclusion that relatively short period acoustic waves heat the low chromosphere in the region just above the temperature minimum. However, these same short period waves (10 period P80 s) are not able to maintain chromospheric temperatures at heights where 5000Å(normal) < 10-6. The calculations also show that an earlier conjecture stating that the H2 population might influence the non-LTE chromospheric H- population is probably not correct, due to lower values of the ratio n
e/n
H inferred from more recent observations. Finally, the calculations support Athay's contention that the Cayrel mechanism alone cannot produce the observed temperature rise, because the magnitude of the radiative cooling in the lines is too great. 相似文献