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1.
X-ray photographs obtained with a zone plate camera on October 3, 1967 in the wavelength band 49.5–52.5 Å have been investigated photometrically.The most intense X-ray emission corresponds with active regions in H and Ca ii. About one quarter of the total solar flux is emitted by the three brightest X-ray sources (A, E and J). X-ray emission from quiet regions is also observed. Limb brightening is found, also at the poles, which indicates a higher electron density at the poles than during solar minimum.The brightest X-ray regions have a very small core of the order of 20. No relation to magnetic field strengths of sunspots has been found. However, a correlation with active prominences cannot be ruled out. X-ray source A is related either to prominence activity or to flare activity. One X-ray region (J) is probably related to flare activity.Assuming an electron temperature of 3 × 106K to 5 × 106K for coronal active regions an emission measure of a few times 1049 cm–3 is derived, which yields an electron density of a few times 1010 cm–3.  相似文献   

2.
A technique for analyzing measurements of XUV spectral line intensities is described. Application of the technique to OSO-4 and OSO-6 spectra indicates that the mean coronal temperature is 2.1 × 106 K in typical active solar regions and that the mean coronal temperature in typical quiet regions ranges from 1.5 × 106 to 2.1 × 106 K. One active region spectrum shows evidence for substantial quantities of coronal material with 2 × 106 < T < 3.5 × 106 K. Measurements from limb spectra show evidence that (1) coronal abundances of N and O are low relative to heavier elements; or (2) that the ionization equilibrium calculations used may contain systematic errors; or (3) that the XUV intensity measurements may be incorrectly calibrated.  相似文献   

3.
After correcting the observed flux of the forbidden lines for the supplementary reddening (due to the circumstellar envelope), we have recalculated the electron density and temperature of the envelope of the Nova. We have determined the temperature and radius of the Nova and obtained values of 1.03×105 K, 1.15×105 K and 1.21×105 K for the temperature and values of 8.49×1010 cm, 4.32×1010 cm and 1.18×1010 cm for the radius of the Nova for 1968, 1969 and 1970, respectively. Using the temperature and radius of the Nova the electron density and temperature of the envelope and the degree of ionization, we have determined the optical depth of the envelope in the Lyman continuum, and found that it is of the order of 10 during the nebular stage.Considering the stratification of the envelope in different regions of ionization, we have determined the radius of the inner and outer edge and the electron temperature of every region. We found that the electron temperature of the inner part of the envelope is at least three times greater than that of the outer part. The variation of electron temperature as a function of the radius of the ionization region considered shows an abrupt increase of theT e whenR/R out(env) is between 0.44 and 0.54.  相似文献   

4.
Brabban  D. H. 《Solar physics》1974,38(2):449-464
A rocket-borne, collimated spectrometer has obtained the soft X-ray (1.0–2.2 nm) spectra of three solar active regions. The principal features of the spectra are described and are then used to determine the conditions in the active regions. An isothermal (single temperature) model is not able to describe the observed spectra so that a continuous distribution of emission measure with temperature is introduced.This distribution, based on that proposed by Chambe, is then used to investigate the structure of the active regions. Several simple models are considered. It is shown that each active region has a hot, dense core surrounded by a large outer volume through which the temperature and density fall until normal coronal conditions are reached.Two of the regions exhibited similar characteristics with the cores having electron densities 1010 cm–3 and temperatures of at least 4 × 106K. Even the third region, which was much less impressive and quite compact in H, appears to have had a small amount of this dense plasma in its central core.  相似文献   

5.
The observation of extreme ultraviolet (EUV) emission lines of Fe ix through Fe xvi made by Orbiting Solar Observatory-1 are discussed and applied to a study of the solar corona above active regions. Ultraviolet and radio emission are determined and compared for several levels of activity classified according to the type of sunspot group associated with the active region. Both radio emission and line radiation from Fe xvi, the highest stage of ionization of Fe observed, are observed to increase rapidly with the onset of activity and are most intense over an E-spot group early in the lifetime of the active region. As activity diminishes, radiation from Fe xv and Fe xvi becomes relatively more prominent. The observations imply that the coronal temperature reaches a maximum during the period of highest activity, as indicated by sunspot-group complexity and the occurrence of chromospheric flares. A maximum coronal electron temperature of 4.0 × 106 °K is estimated when taking into account the mechanism of dielectronic recombination. Concurrently, the average coronal electron density increases by a factor of 10–12. Both electron temperature and density decrease as activity subsides. The coronal temperature above the remaining Ca ii plage is estimated to be 2.5–3.0 × 106 °K after flare activity has ceased and sunspots have disappeared.  相似文献   

6.
New electron excitation rates for O vii calculated by Tayal and Kingston using the R-matrix method are used to determine theoretical emission line strengths. Values of the electron density sensitive ratio R (forbidden line to intercombination line) are found to be very similar to those deduced by other authors. However the temperature sensitive ratios G (intercombination plus forbidden lines to resonance line) are approximately 20% lower than the best previous estimates. The observed value of G for solar active regions (G = 1.0 ± 0.1) predicts an electron temperature in the range 1.1 × 106 K < T e < 1.8 × 106 K, which overlaps that of maximum O vii emissivity, T M = 1.8 × 106 K. In addition, the theoretical G versus T e curve is in excellent agreement with that observed for a Tokamak plasma.  相似文献   

7.
The temperature and density structure of a typical coronal active region is deduced from X-ray observations of several active regions. Observations of the limb transits of three regions from OSO-5 indicate that the X-ray emission originates between 2 × 104 km and 1.5 × 105 km. An emission measure-temperature distribution is deduced from high resolution X-ray spectra obtained with a rocket observation of two similar regions. These observations are combined to give a model of a typical active region, the temperature varying from 2 to 6 × 106 K with corresponding densities between 2 × 109 and 1010 cms–3.  相似文献   

8.
1–8 Å, 2–12 Å and 8–20 Å non-flare X-ray flux data and 9.1 cm spectroheliograms for 1237 days during the period July 1966 to June 1970 have been studied to derive physical models of λ < 20 Å X-ray emitting regions on the Sun under quiescent (non-flare) conditions. The preferred regions of emission below 20 Å which coincide with the coronal active regions characterised by enhanced 9.1 cm microwave emission are found to have temperature lying between 1.8 and 3 × 106 K, emission measure 1049–1050 and electron density 109-1010 per cc. The average area of an active region is 1020 cm2. A slow gradient of temperature and electron density is seen to exist around a region of peak activity, both temperature and electron density decreasing outwards. Based on the derived physical model of the emitting regions a new method is presented for calculating X-ray flux and spectral energy distribution in this wave length region using daily 9.1 cm solar spectroheliograms. The calculated values are in good agreement with the observed values.  相似文献   

9.
New results concerning prominence observations and in particular the prominence–corona transition region (PCTR) are presented. In order to cover a temperature range from 2 × 104 to 7 × 105 K, several emission lines in many different ionization states were observed with SUMER and CDS on board SOHO. EM and DEM were measured through the whole PCTR. We compared the prominence DEM with the DEM from other solar structures (active region, coronal hole and the chromosphere–corona transition region (CCTR)). We notice a displacement of the prominence DEM minimum towards lower temperatures with respect to the minimum of the other structures. Electron density and pressure diagnostics have been made from the observed C III lines. Local electron density and pressure for T ∼ 7 × 104 K are respectively log N e = 9.30−0.34 +0.30 and 0.0405−0.014 +0.012. Extrapolations over the entire PCTR temperature range are in good agreement with previous SOHO results (Madjarska et al., 1999). We also provide values of electron density and pressure in two different regions of the prominence (center and edge). The Doppler velocity in the PCTR shows a trend to increase with temperature (at least up to 30 km s -1 at T ∼ 7 × 104 K), an indication of important mass flows. A simple morphological model is proposed from density and motion diagnostics. If the prominence is taken as a magnetic flux tube, one can derive an opening of the field lines with increasing temperature. If the prominence is represented as a collection of threads, their number increases with temperature from 20 to 800. Derived filling factors can reach values as low as 10−3 for a layer thickness of the order of 5000 km. The variation of non-thermal velocities is determined for the first time, in the temperature range from 2 × 104 to 7 × 105 K. The quite clear similarity with the CCTR non-thermal velocities would indicate that heating mechanisms in the PCTR could be the same as in the CCTR (wave propagation, turbulence MHD).  相似文献   

10.
    
New results concerning prominence observations and in particular the prominence–corona transition region (PCTR) are presented. In order to cover a temperature range from 2 × 104 to 7 × 105 K, several emission lines in many different ionization states were observed with SUMER and CDS on board SOHO. EM and DEM were measured through the whole PCTR. We compared the prominence DEM with the DEM from other solar structures (active region, coronal hole and the chromosphere–corona transition region (CCTR)). We notice a displacement of the prominence DEM minimum towards lower temperatures with respect to the minimum of the other structures. Electron density and pressure diagnostics have been made from the observed C III lines. Local electron density and pressure for T ∼ 7 × 104 K are respectively log N e = 9.30−0.34 +0.30 and 0.0405−0.014 +0.012. Extrapolations over the entire PCTR temperature range are in good agreement with previous SOHO results (Madjarska et al., 1999). We also provide values of electron density and pressure in two different regions of the prominence (center and edge). The Doppler velocity in the PCTR shows a trend to increase with temperature (at least up to 30 km s -1 at T ∼ 7 × 104 K), an indication of important mass flows. A simple morphological model is proposed from density and motion diagnostics. If the prominence is taken as a magnetic flux tube, one can derive an opening of the field lines with increasing temperature. If the prominence is represented as a collection of threads, their number increases with temperature from 20 to 800. Derived filling factors can reach values as low as 10−3 for a layer thickness of the order of 5000 km. The variation of non-thermal velocities is determined for the first time, in the temperature range from 2 × 104 to 7 × 105 K. The quite clear similarity with the CCTR non-thermal velocities would indicate that heating mechanisms in the PCTR could be the same as in the CCTR (wave propagation, turbulence MHD).  相似文献   

11.
Solar active-region temperatures have been determined from the full-Sun spectra of helium-like sulphur (Sxv) observed by the Bragg Crystal Spectrometer on board theYohkoh satellite. The average temperature deduced from Sxv is demonstrated to vary with the solar activity level: A temperature of 2.5 × 106 K is derived from the spectra taken during low solar activity, similar to the general corona, while 4 × 106 K is obtained during a higher activity phase. For the latter, the high-temperature tail of the differential emission measure of active regions is found most likely due to the superposition of numerous flare-like events (micro/nano-flares).  相似文献   

12.
Observations of the post-flare loop system formed after the east limb proton flare of 12 August 1970 include (a) sets of filtergrams from which photographic subtractions have been constructed and (b) spectra from which a distribution of electron density as a function of temperature for three coronal regions are derived. The filtergrams show no indications of radial velocities in excess of 80 km/s. The spectra indicate an increase in density at the tops of the loops with most of the material at a relatively cool temperature: N 6.0 × 1010, T = 3 × 105K. The distribution functions obtained for areas just above and just below loops indicate a lower electron density and the presence of material at high temperatures, N 2.0 × 1010 and T 2.6 × 106K (above the loops) and T e > > 4.4 × 106K for material below the loops.  相似文献   

13.
The slowly varying component of the solar radio emission (S-component) has been investigated from data obtained in the United States and Japan at 35, 17, 9.4 and 4 GHz. A good correlation occurs between the 35 GHz flux of the S-component and the corresponding plage area. This is interpreted by the assumption that the 35 GHz radiation is due to pure free-free emission, and the electron density in the coronal condensation is estimated to be about 2 × 109/cm3, assuming the electron temperature to be 2 × 106 K and the scale height of the coronal condensation to be 3 × 104 km.The S-component radiation at 17 GHz has, in turn, two components, one is due to pure free-free emission and the other is due to thermal-gyro emission. It is concluded that in the active regions a magnetic field of more than 2000 gauss extends horizontally over about 104 km.  相似文献   

14.
We studied the morphology and spatial distribution of loops in an active region, using coordinated observations obtained with both the S082A XUV spectroheliograph and the S056 grazingincidence X-ray telescope on Skylab. The active region loops in the temperature range 5 × 105 –3 × 106 K fall basically into two distinctive groups: the hot loops with temperatures 2–3 × 106 K as observed in coronal lines and X-rays, and the relatively cool loops with temperature 5 × 105 –1 × 106 K as observed in transition-zone lines (Ne vii, Mg ix). The brightest hot coronal loops in the active region are mostly low-lying, compact, closely-packed, and show greater stability than the transition-zone loops, which are fewer in number, large, and slender. The observed aspect ratio of the hot coronal loops is in the range of 0.1 and 0.2, which are almost two orders of magnitude larger than those for the Ne vii loops. Brief discussion of the MHD stability of the loops in terms of the aspect ratio is presented.  相似文献   

15.
Lara  A.  Gopalswamy  N.  Kundu  M. R.  Pérez-EnrÍquez  R.  Koshiishi  H.  Enome  S. 《Solar physics》1998,178(2):353-378
We have studied the properties and evolution of several active regions observed at multiple wavelengths over a period of about 10 days. We have used simultaneous microwave (1.5 and 17 GHz) and soft X-ray measurements made with the Very Large Array (VLA), the Nobeyama Radio Heliograph (NRH) and the Soft X-ray Telescope (SXT) on board the Yohkoh spacecraft, as well as photospheric magnetograms from KPNO. This is the first detailed comparison between observations at radio wavelengths differing by one order of magnitude. We have performed morphological and quantitative studies of active region properties by making inter-comparison between observations at different wavelengths and tracking the day-to-day variations. We have found good general agreement between the 1.5 and 17 GHz radio maps and the soft X-rays images. The 17 GHz emission is consistent with thermal bremsstrahlung (free-free) emission from electrons at coronal temperatures plus a small component coming from plasma at lower temperatures. We did not find any systematic limb darkening of the microwave emission from active regions. We discuss the difference between the observed microwave brightness temperature and the one expected from X-ray data and in terms of emission of a low temperature plasma at the transition region level. We found a coronal optical thickness of 10-3 and 1 for radiation at 17 and 1.5 GHz, respectively. We have also estimated the typical coronal values of emission measure ( 5 × 1028 cm-5), electron temperature ( 4.5 × 1066 K) and density ( 1.2 × 109 cm3). Assuming that the emission mechanism at 17 GHz is due to thermal free-free emission, we calculated the magnetic field in the source region using the observed degree of polarization. From the degree of polarization, we infer that the 17 GHz radiation is confined to the low-lying inner loop system of the active region. We also extrapolated the photospheric magnetic field distribution to the coronal level and found it to be in good agreement with the coronal magnetic field distribution obtained from microwave observations.  相似文献   

16.
Monte Carlo radiative transfer techniques are used to develop a height-dependent spicule model based upon a more realistic configuration than has hitherto been considered. The spicule is represented by a uniform cylinder, of finite length, standing vertically upon a plane chromosphere. The observed, limb-darkened, anisotropic chromospheric flux incident upon the cylinder is incorporated into the transfer calculations.The resulting model is characterized by a random, line broadening velocity of 20 km/sec, with electron temperature increasing from 6 × 103 K at the base to about 1.5 × 104 K at 11500 km above the solar surface. The corresponding values of electron density are 8 × 1011 cm-3 and 4 × 1010 cm-3. Contrast curves of the spicule model against the chromospheric background are computed and indicate that spicules should appear both bright and dark on the disk, depending upon their position with respect to the limb, the spectral frequency of observation and the viewing height.This work is based on a Ph.D. thesis submitted to the Department of Astro-Geophysics, University of Colorado.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

17.
Extreme ultraviolet spectra of several active regions are presented and analyzed. Spectral intensities of 3 active regions observed with the NRL Skylab XUV spectroheliograph (170–630 Å) are derived. From this data density sensitive line ratios of Mg viii, Si x, S xii, Fe ix, Fe x, Fe xi, Fe xii, Fe xiii, Fe xiv, and Fe xv are examined and typically yield, to within a factor of 2, electron pressures of 1 dyne cm–2 (n e T = 6 × 1015 cm–3 K). The differential emission measure of the brightest 35 × 35 portion of an active region is obtained between 1.4 × 104 K and 5 × 106 K from HCO OSO-VI XUV (280–1370 Å) spectra published by Dupree et al. (1973). Stigmatic EUV spectra (1170–1710 Å) obtained by the NRL High Resolution Telescope and Spectrograph (HRTS) are also presented. Doppler velocities as a function of position along the slit are derived in an active region plage and sunspot. The velocities are based on an absolute wavelength scale derived from neutral chromospheric lines and are accurate to ±2 km s–1. Downflows at 105 K are found throughout the plage with typical velocities of 10 km s–1. In the sunspot, downflows are typically 5 to 20 km s–1 over the umbra and zero over the penumbra. In addition localized 90 and 150 km s–1 downflows are found in the umbra in the same 1 × 1 resolution elements which contain the lower velocity downflows. Spectral intensities and velocities in a typical plage 1 resolution element are derived. The velocities are greatest ( 10 km s–1) at 105 K with lower velocities at higher and lower temperatures. The differential emission measure between 1.3 × 104 K and 2 × 106 K is derived and is found to be comparable to that derived from the OSO-VI data. An electron pressure of 1.4 dynes cm–2 (n e T = 1.0 × 1016 cm–3 K) is determined from pressure sensitive line ratios of Si iii, O iv, and N iv. From the data presented it is shown that convection plays a major role in determining the structure and dynamics of the active region transition zone and corona.  相似文献   

18.
It is shown that the simultaneous consideration of observed values of the solar wind proton flux density at 1 AU and of the electron pressure at the base of the solar corona leads to relatively strong constraints on the coronal temperature in the region of subsonic solar wind flow. The extreme upper limit on the mean coronal temperature in the subsonic region is found to be about 2.6 × 106 K, but this upper limit is reduced to about 2.0 × 106 K if reasonable, rather than extreme, assumptions are made; the limit on the maximum temperature is about 0.5 × 106 K greater than the limit on the mean. It is also found that the same two observations limit the rate of momentum addition possible in the region of subsonic solar wind flow.On leave from The Auroral Observatory, Institute of Mathematical and Physical Sciences, University of Troms0, N-9001 Tromsø, Norway.The National Center for Atmospheric Research is sponsored by the National Science Foundation.  相似文献   

19.
We report some results of a rocket experiment flown on 29 April, 1971. A survey of the solar corona was carried out with a pair of collimated Bragg spectrometers to study the resonance, intersystem and forbidden line emission from the helium-like ions O vii (22 Å) and Ne ix (13 Å). In the direction of dispersion the collimator provided a field of view of 1.7. Also, the continuum radiation near 3 Å was monitored by a collimated proportional counter within a view angle of 4.2. The observed X-ray emission came from the general corona, seven plage regions, and one dynamic feature- the late stage of a small flare. From the intensity of the O vii and Ne ix resonance lines the electron temperature and emission measure of the individual emitting regions are derived on the basis of two models, one (a) in which the region is assumed to be isothermal and another (b) in which the emission measure decreases exponentially with increasing temperature. The latter model, which is the most adequate of the two, yields for the electron temperature of the time-varying feature 2–3 × 106 K, for the other active regions 1.5–2.5 × 106 K, and for the general corona 1.3–1.7 × 106 K. The Ne ix emitting regions are about 1.5 times as hot as the O vii regions. The emission measure ranges from 0.4–2.3 × 1048 cm–3 for all active regions and is about 2 × 1049 cm–3 for one hemisphere of the general corona above 106 K. From an analysis of the ratio, R, of the forbidden and intersystem lines of O vii we conclude that none of the regions producing these lines at the time of the rocket flight had electron densities exceeding about 3 × 109 cm–3. Our data demonstrate a dependence of R upon temperature in agreement with the theory of Blumenthal et al. (1971). The wavelengths for the intersystem, the 1s 22s 2 S e–1s2p2s 2 P 0 satellite, and the forbidden transition show in the case of Ne ix improved agreement with predictions. The observed strength of the satellite lines for both O vii and Ne ix agrees with the predictions of Gabriel's (1972) theory, which attributes their formation to dielectronic recombination.We are saddened to report the death of A. J. Meyerott on 13 November, 1971.  相似文献   

20.
The flash spectrograms obtained at the June 30, 1973 eclipse contain the monochromatic images of a coronal condensation in three coronal lines of Fexiv 5303, Fex 6374 and Fexi 7892 and Hα line. The assumption of the axially-symmetric distribution of the emissivity in the coronal lines allows us to find the density and temperature structure of the coronal condensation. While the electron density in the central axis of the condensation is about ten times as high as that of the normal corona at each height, the temperature is not so high (T?2.3×106K). This seems to be a representative nature of a coronal active region in the post maximum phase of activity. It is found that there exists a cool and dense core (T = 106K, N e =6 × 109 cm-3 at 17000 km) at the lower part of the coronal condensation, which is in a close geometrical coincidence with the small active prominence protruding from the underlying plage region.  相似文献   

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