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1.
Long-term MGS drag density observations at 390 km reveal variations of the density with season LS (by a factor of 2) and solar activity index F10.7 (by a factor of 3 for F10.7 = 40-100). According to Forbes et al. (Forbes, J.M., Lemoine, F.G., Bruinsma, S.L., Smith, M.D., Zhang, X. [2008]. Geophys. Res. Lett. 35, L01201, doi:10.1029/2007GL031904), the variation with F10.7 reflects variations of the exospheric temperature from 192 to 284 K. However, the derived temperature range corresponds to variation of the density at 390 km by a factor of 8, far above the observed factor of 3. The recent thermospheric GCMs agree with the derived temperatures but do not prove their adequacy to the MGS densities at 390 km. A model used by Forbes et al. neglects effects of eddy diffusion, chemistry and escape on species densities above 138 km. We have made a 1D-model of neutral and ion composition at 80-400 km that treats selfconsistently chemistry and transport of species with F10.7, T∞, and [CO2]80 km as input parameters. Applying this model to the MGS densities at 390 km, we find variation of T∞ from 240 to 280 K for F10.7 = 40 and 100, respectively. The results are compared with other observations and models. Temperatures from some observations and the latest models disagree with the MGS densities at low and mean solar activity. Linear fits to the exospheric temperatures are T∞ = 122 + 2.17F10.7 for the observations, T∞ = 131 + 1.46F10.7 for the latest models, and T∞ = 233 + 0.54F10.7 for the MGS densities at 390 km. Maybe the observed MGS densities are overestimated near solar minimum when they are low and difficult to measure. Seasonal variations of Mars’ thermosphere corrected for the varying heliocentric distance are mostly due to the density variations in the lower and middle atmosphere and weakly affect thermospheric temperature. Nonthermal escape processes for H, D, H2, HD, and He are calculated for the solar minimum and maximum conditions.Another problem considered here refers to Mars global photochemistry in the lower and middle atmosphere. The models gave too low abundances of CO, smaller by an order of magnitude than those observed. Our current work shows that modifications in the boundary conditions proposed by Zahnle et al. (Zahnle, K., Haberle, R.M., Catling, D.C., Kasting, J.F. [2008]. J. Geophys. Res. 113, E11004, doi:10.1029/2008JE003160) are reasonable but do not help to solve the problem.  相似文献   

2.
The correlation coefficients of the linear regression of six solar indices versus 10.7 cm radio flux F 10.7 were analysed in solar cycles 21, 22 and 23. We also analysed the interconnection between these indices and F 10.7 with help of approximation by polynomials of second order. The indices we have studied in this paper are: the relative sunspot numbers – SSN, 530.3 nm coronal line flux – F 530, the total solar irradiance – TSI, Mg II 280 nm core-to-wing ratio UV-index, the Flare Index – FI and the counts of flares. In most cases the regressions of these solar indices vs. F 10.7 are close to the linear regression except the moments of time near the minimums and maximums of the 11-year activity. For the linear regressions, we found that correlation coefficients K corr(t) for the solar indices vs. F 10.7 and SSN dropped to their minimum values twice during each 11-year cycle.  相似文献   

3.
Nonthermal emission occurs in the cores of the 9.4- and 10.4-μm CO2 bands on Mars, and has been recently identified as a natural atmospheric laser. This paper presents observations of the total flux and center-to-limb dependence of this emission for Mars and Venus. The emission is believed to be excited by absorption of solar flux in the near-ir CO2 bands, followed by collisional transfer to the 00°1 state of CO2. A comparison is made between the observations and a detailed theoretical model based on this mechanism. It is found that the theoretical model successfully reproduces the observed center-to-limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations. A comparison is also made between the observed fluxes and the predictions of the theoretical models. The observed flux from Mars agrees closely with the prediction of the model; the flux observed from Venus is 74% of the flux predicted by the model. This emission is utilized to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T = 135 ± 20°K. The frequency width of the emission is also analyzed to derive a temperature of 126 ± 6°K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T = 204 ± 10°K.  相似文献   

4.
Additional analysis of the behavior of the international sunspot number (R) series and the solar radio flux density (F10.7 cm) series during two long (250–500 days) and distinct episodes of persistent ≈13-day variations (Crane, Solar Phys. 1998, 253, 177) is reported. The conclusion is that while the center-to-limb behavior of R does not change between solar minimum and solar maximum, F10.7 cm exhibits significantly less limb brightening at solar maximum than at solar minimum.  相似文献   

5.
Analysis of observed spectrograms is based on comparison with synthetic spectra. The O2(b1Σ+g?X3Σ?g Atm. (1,1) band in high latitude auroras observed from the ground is found to be the strongest in the Δv = 0 sequence. It is enhanced with altitude relative to the N2 1P(2, 0)and N+2 M(2,0) bands, but the O2 Atm. (2, 2) band has an unexpected low intensity. The range of rotational temperatures of the O2 Atm. bands varies from approx. 200 to above 500 K which indicates that the altitude of the centroid of the emission region varies from about 100 km to the F-region. The highest temperature is found in the midday aurora associated with the magnetospheric cusp. Conspicuous relative variations between the intensities of N2 and O2 spectra are documented, but a satisfactory explanation of the variety is not given. Deviations of the observed O2 Atm. band intensities from the vibrational intensity distribution predicted by Franck-Condor factors indicate that the excitation of the O2 Atm. bands in aurora is not mainly due to particle impact on O2, and the contribution due to energy transfer from hot O(1D) atoms has to be found in future research.  相似文献   

6.
The fractional convective flux πF c (x c /πF) is computed for the effective level x c = logτ c = 0.125, using bi-dimensional co-spectra for relative continuum-brightness fluctuations ΔI and radial velocity fluctuations ΔV measured for the C i 5052.16 spectral line. A more uncertain flux for x Fe ≈ - 0.9 is obtained for the Fe i 5049.83 line. Since the results (Figure 1) incorporate current uncertainties in RMS ΔI , RMS ΔV and RMS ΔT (x), where ΔT are photospheric temperature fluctuations, they must be considered qualitative until these uncertainties are appreciably reduced. The requirement that the fractional convective flux < 1, places restrictions on these uncertainties which suggest that current RMS ΔT (x)'s are too large. The results confirm the importance of overshoot at the top of the solar hydrogen convection zone and suggest a non-negligible fractional convective flux throughout the lower photosphere. Qualitatively, they do not agree with the predictions of the generally-used, local, mixing-length theory or those of Parsons' (1969) modified mixing-length theory. However, qualitative agreement with the predictions of the non-local, generalized mixing-length theory of Spiegel (1963) and with the non-local theory of Ulrich (1970) cannot be considered as observational confirmation of these theories.  相似文献   

7.
Empirical models of molecular ion densities (N2 +, NO+, O2 +) and the electron density (N e ) are presented in the altitude interval 50–4000 km as functions of time (diurnal, annual), space (position, altitude) and solar flux (F 10.7). Using observations of 6 satellites (AE-C, AE-D, AE-E, ALOUETTE-2, ISIS-1, ISIS-2), 4 incoherent scatter stations (Arecibo, Jicamarca, Millstone Hill, St Santin) and more than 700 D-region profiles, this model describes the global gross features of the ionosphere for quiet geophysical conditions (K p 3).The molecular ion densities and the electron density increase with increasing altitude up to a maximum (or several maxima) - and decrease from thereon with increasing height. Between ~80 and 200 km, the main ionic constituents are NO+ and O2 +; below ~80 km cluster ions are predominating. During local summer conditions the molecular ions and N e increase around polar latitudes and decrease correspondingly during local winter. The diurnal variations are intrinsically coupled to the individual plasma layers; in general, the molecular ion and electron densities are enhanced during daytime and depleted during nighttime (for details and exceptions, see text).  相似文献   

8.
The relations between variations of far UV (FUV) emission in 115–210 nm waveband and L 121.6 nm and F10.7 are studied. The changes of FUV flux are found to lag changes of F10.7 - as a rule for 1 day. It is shown that such a difference may be caused by two factors: 1) differences between the rates of decrease of local sources' (active regions) brightness in FUV and 10.7 cm; 2) differences between limb-darkening curves for different wavelengths. One may expect the fluxes at different wavelengths to exhibit phase shifts of one relative to another. Cross-correlation analysis reveals no time-delay between emission fluxes within the FUV waveband, in spite of different laws for limb-brightening (darkening) for different spectral intervals. The absence of a phase delay can be caused by relatively small contribution of active regions to the flux of the whole Sun at these wavelengths. Thus the Lyman-alpha line intensity variation reflects variations of Solar FUV emission more precisely than F10.7. Therefore, using the L intensity for flux intensity calculations of other FUV wavelengths is preferable to using the F10.7 index.  相似文献   

9.
The study of the variation of equivalent width in a Rayleighscattering planetary atmosphere along the intensity equator and along the mirror meridian on whichμ =μ 0 shows that the equivalent widths decrease monotonically towards the poles, the limb and the terminator with the following characteristics: (i) the weakest lines exhibit the maximum change; (ii) theI e r component shows more change than theI e r component; (iii) the decrease towards the limb or the terminator is not as sharp as that towards the poles; (iv)I e r component shows more decrease towards the limb whileI e r component shows more decrease towards the terminator; and (v) the relationW (μ, φ;μ 0,φ 0)= W (μ 0,φ 0;μ, φ) holds for the total intensity. These results are qualitatively in agreement with the observations of absorption bands in the spectra of Venus, Jupiter and Saturn.  相似文献   

10.
Calculations using a wide range of model ionospheres (with a peak at 300 km) show that the integrated electron content up to the height of the satellite could be up to four times the value deduced from Faraday rotation measurements. However, using a fixed mean field height of 400 km, the observed Faraday rotation gives the electron content up to a height hF of 2000 km with an accuracy of ±3 per cent. For observations at different magnetic and geographic latitudes, and geostationary satellites at different longitudes, the optimum value of hF varies by only ±200 km. Night-time increases in the height of the ionosphere have little effect on hF, but increase the mean field height to about 470 km. Using a fixed value of 420 km, with hF = 2000 km, gives an accuracy of ±5 per cent under most conditions.  相似文献   

11.
High resolution sunspot photographs in the blue, red and infrared continuum exposed on various days were used to derive the center-to-limb variation of the intensity ratio = I sp / I ph. Special care was taken to correct for image blurring, scattered light and the influence of line absorption.The observed increase of specific umbral intensities u towards the limb leads to an extremely small temperature gradient in the umbra. From geometrical changes of the profiles (Wilson effect), we derived an umbral depression of about 650 km and a density scale height of about 450 km when H - is assumed to be the predominant source of absorption. The penumbral depression was found to be 50 km or less. The density scale height of the umbra as computed from the observed temperature distribution is 80 km in the case of hydrostatic equilibrium. We conclude that either magnetic pressure components produce deviations from hydrostatic equilibrium or that another source of absorption, dominating in the outer layers, has to be taken into account.  相似文献   

12.
We develop a model for estimating solar total irradiance since 1600 AD using the sunspot number record as input, since this is the only intrinsic record of solar activity extending back far enough in time. Sunspot number is strongly correlated, albeit nonlinearly with the 10.7-cm radio flux (F 10.7), which forms a continuous record back to 1947. This enables the nonlinear relationship to be estimated with usable accuracy and shows that relationship to be consistent over multiple solar activity cycles. From the sunspot number record we estimate F 10.7 values back to 1600 AD. F 10.7 is linearly correlated with the total amount of magnetic flux in active regions, and we use it as input to a simple cascade model for the other magnetic flux components. The irradiance record is estimated by using these magnetic flux components plus a very rudimentary model for the modulation of energy flow to the photosphere by the subphotospheric magnetic flux reservoir feeding the photospheric magnetic structures. Including a Monte Carlo analysis of the consequences of measurement and fitting errors, the model indicates the mean irradiance during the Maunder Minimum was about 1 ± 0.4 W m−2 lower than the mean irradiance over the last solar activity cycle.  相似文献   

13.
Results of the scattered solar radiation spectrum measurements made deep in the Venus atmosphere by the Venera 11 and 12 descent probes are presented. The instrument had two channels: spectrometric (to measure downward radiation in the range 0.45 < γ < 1.17 μm) and photometric (four filters and circular angle scanning in an almost vertical plane). Spectra and angular scans were made in the height range from 63 km above the planet surface. The integral flux of solar radiation is 90 ± 12 W m?2 measured on the surface at the subsolar point. The mean value of surface absorbed radiation flux per planetary unit area is 17.5 ± 2.3 W m?2. For Venera 11 and 12 landing sites the atmospheric absorbed radiation flux is ～15 W m?2 for H >; 43 km and ～45 W m?2 for H < 48 km in the range 0.45 to 1.55 μm. At the landing sites of the two probes the investigated portion of the cloud layer has almost the same structure: it consists of three parts with boundaries between them at about 51 and 57 km. The base of clouds is near 48 km above the surface. The optical depth of the cloud layer (below 63 km) in the range 0.5 to 1 μm does not depend on the wavelength and is ～29 and ～38 for the Venera 11 and 12 landing sites, respectively. The single-scattering albedo, ω0, in the clouds is very close to 1 outside the absorption bands. Below 58 km the parameter (1 ? ω0) is <10?3 for 0.49 and 0.7 μm. The parameter (1 ? ω0) obviously increases above 60 km. Below 48 km some aerosol is present. The optical depth here is a strong function of wavelength. It varies from 1.5 to 3 at λ = 0.49 μm and from 0.13 to 0.4 at 1.0 μm. The mean size of particles below the cloud deck is about 0.1 μm. Below 35 km true absorption was found at λ < 0.55 μm with the (1 ? ω0) maximum at H ≈ 15 km. The wavelength and height dependence of the absorption coefficient are compatible with the assumption that sulfur with a mixing ratio ～2 × 10?8 normalized to S2 molecules is the absorber. The upper limits of the mixing ratio for Cl2, Br2, and NO2 are 4 × 10?8, 2 × 10?11, and 4 × 10?10, respectively. The CO2 and H2O bands are confidently identified in the observed spectra. The mean value of the H2O mixing ratio is 3 × 10?5 < FH2O < 10?4 in the undercloud atmosphere. The H2O mixing ratio evidently varies with height. The most probable profile is characterized by a gradual increase from FH2O = 2 × 10?5 near the surface to a 10 to 20 times higher value in the clouds.  相似文献   

14.
H. C. Spruit 《Solar physics》1976,50(2):269-295
  相似文献   

15.
We observed a cluster of extremely bright penumbral grains located at the inner limb‐side penumbra of the leading sunspot in active region NOAA 10892. The penumbral grains in the cluster showed a typical peak intensity of 1.58 times the intensity I0 of the granulation surrounding the sunspot. The brightest specimen even reached values of 1.8–2.0 I0, thus, exceeding the temperatures of the brightest granules in the immediate surroundings of the sunspot. We find that the observed sample of extremely bright penumbral grains is an intermittent phenomenon, that disappears on time scales of hours. Horizontal flow maps indicating proper motions reveal that the cluster leaves a distinct imprint on the penumbral flow field. We find that the divergence line co‐located with the cluster is displaced from the middle penumbra closer towards the umbra and that the radial outflow velocities are significantly increased to speeds in excess of 2 km s–1. The extremely bright penumbral grains, which are located at the inner limb‐side penumbra, are also discernible in offband Hα images down to Hα ± 0.045 nm. We interpret the observations in the context of the moving flux tube model arguing that hotter than normal material is rapidly ascending along the inner footpoint of the embedded flux tube, i.e., the ascending hot material is the cause of the extremely bright penumbral grains. This study is based on speckle‐reconstructed broad‐band images taken at 600 nm and chromospheric Hα observations obtained with two‐dimensional spectroscopy. All data were taken with adaptive optics under very good seeing conditions at the Dunn Solar Telescope, National Solar Observatory/Sacramento Peak, New Mexico on 2006 June 10. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
We present radiometrically calibrated spectrophotometric images of Mars taken at the NASA Infrared Telescope Facility (IRTF) near and during the 1995 and 1999 oppositions. Absolute intensity and radiance factor (rF = I/F) values have been calculated for approximately 95% of the surface over all longitudes between −70° to 90° latitude in the 1.5- to 4.1-μm spectral region at a spectral resolution (Δλ/λ) of 1.5%. Values of radiance factor range from rF = 0.4 to 0.6 at 2.2 μm for the bright regions such as Moab and Arabia to rF = 0.12 to 0.3 at 2.2 μm around the dark regions Syrtis Major and Acidalia Planitia. Variations are seen due to seasonal dust and/or condensate cloud cover and viewing geometry. Our results are generally consistent with the few reported previous radiance factor determinations for Mars. These data are unique among ground-based data in their relatively high spatial resolution (?200 km/pixel at the sub-Earth point) and coverage combined with their spectral resolution and coverage. These radiometrically calibrated observations can be used as input to studies focusing on spectral unmixing of surface and atmospheric components, radiative transfer modeling of disk and limb radiances, and photometric modeling of the martian phase function.  相似文献   

17.
Venus nightglow was observed at NASA IRTF using a high-resolution long-slit spectrograph CSHELL at LT = 21:30 and 4:00 on Venus. Variations of the O2 airglow at 1.27 μm and its rotational temperature are extracted from the observed spectra. The mean O2 nightglow is 0.57 MR at 21:30 at 35°S-35°N, and the temperature increases from 171 K near the equator to ∼200 K at ±35°. We have found a narrow window that covers the OH (1-0) P1(4.5) and (2-1) Q1(1.5) airglow lines. The detected line intensities are converted into the (1-0) and (2-1) band intensities of 7.2 ± 1.8 kR and <1.4 kR at 21:30 and 15.5 ± 2 kR and 4.7 ± 1 kR at 4:00. The f-component of the (1-0) P1(4.5) line has not been detected in either observation, possibly because of resonance quenching in CO2. The observed Earth’s OH (1-0) and (2-1) bands were 400 and 90 kR at 19:30 and 250 and 65 kR at 9:40, respectively. A photochemical model for the nighttime atmosphere at 80-130 km has been made. The model involves 61 reactions of 24 species, including odd hydrogen and chlorine chemistries, with fluxes of O, N, and H at 130 km as input parameters. To fit the OH vibrational distribution observed by VEX, quenching of OH (v > 3) in CO2 only to v ? 2 is assumed. According to the model, the nightside-mean O2 emission of 0.52 MR from the VEX and our observations requires an O flux of 2.9 × 1012 cm−2 s−1 which is 45% of the dayside production above 80 km. This makes questionable the nightside-mean O2 intensities of ∼1 MR from some observations. Bright nightglow patches are not ruled out; however, the mean nightglow is ∼0.5 MR as observed by VEX and supported by the model. The NO nightglow of 425 R needs an N flux of 1.2 × 109 cm−2 s−1, which is close to that from VTGCM at solar minimum. However, the dayside supply of N at solar maximum is half that required to explain the NO nightglow in the PV observations. The limited data on the OH nightglow variations from the VEX and our observations are in reasonable agreement with the model. The calculated intensities and peak altitudes of the O2, NO, and OH nightglow agree with the observations. Relationships for the nightglow intensities as functions of the O, N, and H fluxes are derived.  相似文献   

18.
Multiple-beam observations of solar flares at submillimeter wavelengths need detection with at least four beams to derive the flux density $\mbox{$F$} $ of the emitting source, its size, and centroid position. When this condition is not fulfilled, the assumptions on the location and/or size of the emitting source have to be made in order to compute $\mbox{$F$}$ . Otherwise, only a flux density range $\mbox{$\Delta F$}$ can be estimated. We report on simultaneous flare observations at 212 and 210 GHz obtained by the Solar Submillimeter Telescope (SST) and the Bernese Multibeam Radiometer for Kosma (BEMRAK), respectively, during two solar events on 28 October 2003. For both events, BEMRAK utilized four beam information to calculate the source flux density F 210, its size and position. On the other hand, the SST observed the events with only one beam, at low solar elevation angles and during high atmospheric attenuation. Therefore, because of these poor observing conditions at 212 GHz, only a flux density range ΔF 212 could be estimated. The results show that ΔF 212 is within a factor of 2.5 of the flux density F 210. This factor can be significantly reduced (e.g. 1.4 for one of the studied events) by an appropriate choice of the 212 GHz source position using flare observations at other wavelengths. By adopting the position and size of the 210 GHz source measured by BEMRAK, the flux density at 212 GHz, F 212b, is comparable to F 210 within the uncertainties, as expected. Therefore our findings indicate that even during poor observing conditions, the SST can provide an acceptable estimate of the flux density at 212 GHz. This is a remarkable fact since the SST and BEMRAK use quite different procedures for calibration and flux density determination. We also show that the necessary assumptions made on the size of the emitting source at 212 GHz in order to estimate its flux density are not critical, and therefore do not affect the conclusions of previous studies at this frequency.  相似文献   

19.
Height profiles of auroral emissions at 3914 Å, 4861 Å, and 5577 Å were obtained in two rocket flights through medium intensity stable aurora. The 3914 Å N2+ integral intensity data were compared with intensity variations predicted by an auroral model for a range of primary electron energy spectra. The observed profiles for the two flights were well reproduced respectively by a 5.6 keV mono-energtic flux and by a flux with an exponential spectrum cutting off around 12 to 15 keV. The data for 5577 Å (available only above 120 km) bear a constant ratio to that for 3914 Å. The emission profiles derived for 3914 Å, peak at 115 and 107 km respectively.  相似文献   

20.
It is shown (1) that the coefficients Ai of the limb darkening functions I(μ)/Icenter = P5 (μ) = ∑Ai μi (i = 0... 5; μ = cos ϑ), which had been published by Neckel and Labs (Solar Phys. 153, 91, 1994), can well be approximated by analytical functions of wavelength λ, and (2) that at first sight purely formal extrapolation of the functions P5(μ) to the very limb (μ = 0.0) is not meaningless: in combination with absolute intensities for the disk center these functions yield ‘limb intensities’ which all correspond to almost the same ‘limb temperature’, Tlimb≈4746 K. Together these results lead to ‘reference functions’ which can quickly yield rather reliable values of the Sun's continuum intensities, for any values of μ and λ.  相似文献   

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