Rocket observations of the extreme ultraviolet dayglow   总被引：1，自引：0，他引：1  

R.W. Carlson  D.L. Judge 《Planetary and Space Science》1973,21(5):879-880

The ultraviolet dayglow in the wavelength region 750–1050 Å was investigated over the altitude range 100–800 km using a thin film filter photometer. From the airglow spectrum obtained by Carruthers and Page, one of the dominant features in this wavelength range is OII 834 Å. It is pointed out that the major excitation mechanism for this transition is photoionization excitation of atomic oxygen. Solution of the radiative transfer problem for this excitation process shows good agreement with the observed dayglow in the 300–800 km region. At lower altitudes additional components are present and are interpreted as the N₂, OI and possibly HI emissions observed by Carruthers and Page.  相似文献   

CCD Observations of Comet Hale-Bopp at Shajn Telescope I. Coude spectra     

Korsun  P. P.  Davis  S. P.  Shavrina  A. V.  Vasiljeva  I. E.  Malanushenko  V. P.  Savanov  I. S. 《Earth, Moon, and Planets》1997,78(1-3):119-125

Spectroscopic observations of Comet Hale-Bopp were made at the 2.6 m Shajn Telescope of the Crimean Astrophysical Observatory. Some spectra were obtained with high spectral resolution, FWHM = 0.18–0.4Å, in the coude focus on February 22 and 26, 1997. The observations were made in selected spectral windows (4805–4872 Å,6528–6595 Å, 7186–7253 Å, 8276–8408 Å).The spectrograph slit was centered on the nucleus and had dimensions of 25.2 × 0.6 arcsec² on the plane of the sky. The continuum spatial profiles were extremely asymmetrical toward the Sun. However, the continuum-subtracted spatial profiles of the molecular emissions were symmetrical relative to the nucleus, except for C₂. The shape of the spatial profiles of the C₂ emissions is similar to that one of continuum but is more flattened. So, there are evidences that dust can be an additional source of the C₂ radicals in the cometary coma. The main aim of our research was identification of the cometary emissions. Using recent laboratory spectroscopic data we identified newlines of C₂ associated with the transitions from high rotational levels in the 4805–4872 Å spectral region. We detected cometary H_α emission as well. Emissions of NH₂, H₂O⁺,and C₂ (Phillips system) were found in the red spectral windows. Some emission features are still unassigned.  相似文献   

The Gas Production Rate and Coma Structure of Comet C/1995 O1 (Hale–Bopp)     

Morgenthaler  Jeffrey P.  Harris  Walter M.  Roesler  Frederick L.  Scherb  Frank  Anderson  Christopher M.  Doane  Nathaniel E.  Oliversen  Ronald J. 《Earth, Moon, and Planets》2002,90(1-4):77-87

The University of Wisconsin–Madison and NASA–Goddard conducted acomprehensive multi-wavelength observing campaign of coma emissionsfrom comet Hale–Bopp, including OH 3080 Å, [O I] 6300 Å H₂O⁺ 6158 Å, H Balmer-α 6563 Å, NH₂ 6330 Å, [C I] 9850 ÅCN 3879 Å, C₂ 5141 Å, C₃ 4062 Å,C I 1657 Å, and the UV and optical continua. In thiswork, we concentrate on the results of the H₂O daughter studies.Our wide-field OH 3080 Å measured flux agrees with other, similarobservations and the expected value calculated from published waterproduction rates using standard H₂O and OH photochemistry.However, the total [O I] 6300 Å flux determined spectroscopically overa similar field-of-view was a factor of 3-4 higher than expected.Narrow-band [O I] images show this excess came from beyond theH₂O scale length, suggesting either a previously unknown source of[O I] or an error in the standard OH + ν→ O(¹ D) + H branching ratio. The Hale–Bopp OH and[O I] distributions, both of which were imaged tocometocentric distances >1 × 10⁶ km, were more spatiallyextended than those of comet Halley (after correcting for brightnessdifferences), suggesting a higher bulk outflow velocity. Evidence ofthe driving mechanism for this outflow is found in the Hα lineprofile, which was narrower than in comet Halley (though likelybecause of opacity effects, not as narrow as predicted by Monte-Carlomodels). This is consistent with greater collisional coupling betweenthe suprathermal H photodissociation products and Hale–Bopp's densecoma. Presumably because of mass loading of the solar wind by ionsand ions by the neutrals, the measured acceleration of H₂O⁺ downthe ion tail was much smaller than in comet Halley. Tailwardextensions in the azimuthal distributions of OH 3080 Å,[O I], and [C I] , as well as a Doppler asymmetry in the[O I] line profile, suggest ion-neutral coupling. While thetailward extension in the OH can be explained by increased neutralacceleration, the [O I] 6300 Å and [C I] 9850 Å emissions show 13%and >200% excesses in this direction (respectively), suggesting anon-negligible contribution from dissociative recombination of CO⁺and/or electron collisional excitation. Thus, models including theeffects of photo- and collisional chemistry are necessary for the fullinterpretation of these data.  相似文献   

Statistics of the Big Blue Bump Feature in a Low Redshift Sample of Active Galactic Nuclei     

Shuang-An Huang  You-Yuan Zhou  Ting-Gui Wang 《Astrophysics and Space Science》2002,280(3):301-316

We present a statistical analysis of the big blue bump (BBB) feature for a large heterogeneous sample of 95 optically selected and soft X-ray bright, low redshift active galactic nuclei (AGNs). This sample covers a sufficiently broad luminosity range, allowing us to test the luminosity dependence of the spectral energy distribution in the BBB region. Following the works of Zheng et al., Laor et al. and Kriss et al., we introduce the broad band spectral index from 1050 Å to0.5 keV (α _UV-SX ), compare its distribution with that of the soft X-ray spectral index (α _SX ) obtained by ROSAT PSPC, and find that the two indices have equal average-values within 1 ～ 2σuncertainties, whether in the whole sample, in luminosity divisions or in subsamples. These equalities also have no obvious luminosity dependence. This indicates that a single power law can describe the overall UV toX-ray spectrum in a statistical sense, or the broad band UV to soft X-ray spectrum is the soft X-ray spectral extension on an average. Thus, our results support Laor et al.'s conjecture about the BBB peak aroundFUV 1050 Å from a statistical viewpoint. As we further test whether the equality holds for individual objects within measure errors, χ₂ test refuse to accept it. In addition, our statistical results, from the luminosity divisions and on the correlation of spectral indices with luminosity (M _B), imply that the luminosity dependence of α _UV and α _UV-SX is mainly due to absorption in low luminosity AGNs.  相似文献   

Observations of the optical spectrum of the dayside magnetospheric cleft aurora     

W.A. Gault  R.A. Koehler  R. Link  G.G. Shepherd 《Planetary and Space Science》1981,29(3):321-333

Optical spectra of the cleft aurora in the region 5000–8500 Å were measured in December, 1977 at Cape Parry, N.W.T. A Michelson interferometer was used at a resolution of 10 cm^?1. The auroral features observed were OI (5577, 6300-64, 7774, 8446 Å), OII (7319-30 Å), NI (5200 Å), Hα, O₂ atm (1,1), some weak N₂1P bands and possibly some Meinel bands of N₂⁺. In addition, nightglow emissions of Na and OH were observed. Theoretical predictions of the OI and NI emission rates using the model of Link et al. (1980) fit the observed rates reasonably well if a 40 eV Maxwellian incident electron spectrum is assumed. The predicted rates for OII exceed the observed value by a factor of 4. It is suggested that the ionization cross-section may be over-estimated.  相似文献   

Optical spectroscopy of the radio pulsar PSR B0656+14     

S. Zharikov  R. E. Mennickent  Yu. Shibanov  V. Komarova 《Astrophysics and Space Science》2007,308(1-4):545-549

We have obtained the spectrum of a middle-aged PSR B0656+14 in the 4300–9000 Å range with the ESO/VLT/FORS2. Preliminary results show that at 4600–7000 Å the spectrum is almost featureless and flat with a spectral index α _ν ??0.2 that undergoes a change to a positive value at longer wavelengths. Combining with available multiwavelength data suggests two wide, red and blue, flux depressions whose frequency ratio is about 2 and which could be the 1st and 2nd harmonics of electron/positron cyclotron absorption formed at magnetic fields ～10⁸ G in upper magnetosphere of the pulsar.  相似文献   

Detailed optical spectroscopy of the B[e] Star MWC17     

V. G. Klochkova  E. L. Chentsov 《Astrophysical Bulletin》2016,71(1):33-42

Based on the material of multiple high-resolution R = 60 000 observations conducted on the 6-m telescope (BTA) of the Special Astrophysical Observatory in combination with the Nasmyth Echelle Spectrograph (NES), we closely studied the features of the optical spectrum of the star MWC17 with the B[e] phenomenon. In the wavelength interval of 4050–6750 Å, we identified numerous permitted and forbidden emissions, interstellar Na I lines, and diffuse interstellar bands (DIBs). Radial velocities were estimated from lines of different origin. As the systemic velocity, V_sys, the velocity of the forbidden emissions can be accepted: ?47 kms^?1 (relative to the local standard V_lsr = ?42 kms^?1). Comparison of the obtained data with the earlier measurements allows us to conclude on the absence of considerable variability of spectral details.  相似文献   

Spectral variability of the peculiar A-type supergiant 3Pup     

E. L. Chentsov  V. G. Klochkova  A. S. Miroshnichenko 《Astrophysical Bulletin》2010,65(2):150-163

Optical spectra taken in 1997–2008 are used to analyze the spectral peculiarities and velocity field in the atmosphere of the peculiar supergiant 3 Pup. The profiles of strong Fe II lines and of the lines of other iron-group ions have a specific shape: the wings are raised by emissions, whereas the core is sharpened by a depression. The latter feature becomes more pronounced with the increasing line strength, and the increasing wavelength. Line profiles are variable: the magnitude and sign of the absorption asymmetry, and the blue-to-red emission intensity ratios vary from one spectrum to another. The temporal V_r variations are minimal for the forbidden emissions and sharp shell cores of the absorption features of FeII(42), and other strong lines of iron-group ions. The average velocity for the above lines can be adopted as the systemic velocity: V_sys = 28.5 ± 0.5 km/s. The weakest photospheric absorptions and photospheric MgII, Si II absorptions exhibit well-defined day-to-day velocity variations of up to 7 km/s. Quantitative spectral classification yields the spectral type of A2.7±0.3 Ib. The equivalent widths and profiles of Hδ and Hγ, and the equivalent width of the OI 7774 Å triplet yield an absolute magnitude estimate of Mv=?5.5^m ± 0.3^m, implying the heliocentric distance of 0.7 kpc.  相似文献   

Spatially resolved absolute spectral reflectivity of Jupiter: 3390–8400 Å     

Glenn S. Orton 《Icarus》1975,26(2):159-174

Observational determinations of the absolute spectral reflectivities of visually distinct regions of Jupiter are presented. The observations cover the 3390–8400 Å region at 10 Å resolution, and they are compared with observations using 150–200 Å filters in the 3400–6400 Å range. The effective reflectivities for several regions (on the meridian) in the 3400–8400 Å range are: South Tropical Zone, 0.76±0.05; North Tropical Zone, 0.68±0.08; South Equatorial Belt, 0.63±0.08; North Equatorial Belt, 0.62±0.04; and the Great Red Spot, 0.64±0.09. Reflectivities near the limb are also observed. The appropriate blue and red reflectivities are tabulated in support of the Pioneer 10 and 11 imaging photopolarimeter experiments. For the regions listed above, equivalent widths of molecular bands vary as: CH₄ (6190 Å), 14–16 Å; CH₄ (7250 Å), 77–86 Å; and NH₃ (7900 Å), 87–95 Å. Significant differences from the results of C. B. Pilcher, R. G. Prinn, and T. B. McCord (“Spectroscopy of Jupiter: 3200 to 11200 Å,” J. Atmos. Sci.30, 302–307.)  相似文献   

Multiwavelength Study of a Solar Eruption from AR NOAA 11112: II. Large-Scale Coronal Wave and Loop Oscillation     

Pankaj Kumar  K.-S. Cho  P. F. Chen  S.-C. Bong  Sung-Hong Park 《Solar physics》2013,282(2):523-541

We analyze multiwavelength observations of an M2.9/1N flare that occurred in AR NOAA 11112 on 16 October 2010. AIA 211 Å EUV images reveal the presence of a faster coronal wave (decelerating from ≈?1390 to ≈?830 km?s^?1) propagating ahead of a slower wave (decelerating from ≈?416 to ≈?166 km?s^?1) towards the western limb. The dynamic radio spectrum from Sagamore Hill radio telescope shows the presence of a metric type II radio burst, which reveals the presence of a coronal shock wave (speed ≈?800 km?s^?1). The speed of the faster coronal wave, derived from AIA 211 Å images, is found to be comparable to the coronal shock speed. AIA 171 Å high-cadence observations showed that a coronal loop, which was located at a distance of ≈?0.32R _⊙ to the west of the flaring region, started to oscillate by the end of the impulsive phase of the flare. The results indicate that the faster coronal wave may be the first driver of the transversal oscillations of coronal loop. As the slower wave passed through the coronal loop, the oscillations became even stronger. There was a plasmoid eruption observed in EUV and a white-light CME was recorded, having velocity of ≈?340?–?350 km?s^?1. STEREO 195 Å images show an EIT wave, propagating in the same direction as the lower-speed coronal wave observed in AIA, but decelerating from ≈?320 to ≈?254 km?s^?1. These observations reveal the co-existence of both waves (i.e. coronal Moreton and EIT waves), and the type II radio burst seems to be associated with the coronal Moreton wave.  相似文献   

Atmospheric wave propagations in the mesopause region observed by the OH(8,3) band,NaD, O₂A(8645Å) band and OI 5577 Å nightglow emissions     

H. Takahashi  P.P. Batista  Y. Sahai  B.R. Clemesha 《Planetary and Space Science》1985,33(4):381-384

Simultaneous measurements of the upper mesospheric NaD and OH(8,3) band emissions by meridional scanning photometers, and the OI 5577 Å, O₂ Atmospheric band at 8645 Å, NaD and OH(8,3) band emissions by multi-channel tilting filter type zenith photometers have been carried out at Cachoeira Paulista (22.7°S, 45.0°W), Brazil. On two nights during the period May–August 1983, the meridional scanning observations showed horizontal intensity gradients and phase propagations. The nocturnal intensity variations on one of these occasions 13–14 June 1983, which was a magnetically disturbed night with 4 ?k_p? 8, also showed vertical phase propagation. In this paper, we present these observations and discuss the possible effects of the horizontal wind system and of gravity wave propagation.  相似文献   

Absolute spectrophotometry of Comet Kohoutek 1973f: I. Column densities of cyanogen     

J.S. Neff  D. Ketelsen  G.D. Schmidt  J.B. Tatum 《Icarus》1976,27(4):545-551

Absolute spectrophotometry of the coma of Comet Kohoutek 1973f is discussed for the nights of January 24 and 26, 1974. Specific intensities are measured for spectral features and a continuum band in the wavelength region λλ3460–6062Å. The (0, 0) band of the Δν = 0 sequence of the violet system of the cyanogen molecule is analyzed and column densities of 1.7 × 10¹⁵m^?2 and 3.4 × 10¹⁴m^?2 are found for January 24 and 26, 1974, respectively. The analysis of the bands of C₂ will be reported in a second paper of this series.  相似文献   

The intensity variation of the atomic oxygen red line during morning and evening twilight on 9–10 April 1969     

R.G. Roble  J.F. Noxon  J.V. Evans 《Planetary and Space Science》1976,24(4):327-340

During the evening of 9 April and the morning of 10 April 1969, the twilight zenith intensity of the atomic oxygen red line OI(³P-¹D) at 6300 Å was measured at the Blue Hill Observatory (42°N, 17°W). At the same time incoherent scatter radar data were being obtained at the Millstone Hill radar site 50 km distant. We have used a diurnal model of the mid-latitude F-region to calculate the ionospheric structure over Millstone Hill conditions similar to 9–10 April 1969. The measured electron temperature, ion temperature, and electron density at 800 km are used as boundary conditions for the model calculations. The diurnal variation of neutral composition and temperature were obtained from the OGO-6 empirical model and the neutral winds were derived from a semiempirical three-dimensional dynamic model of the neutral thermosphere. The solar EUV flux was adjusted to yield reasonable agreement between the calculated and observed ionospheric properties.This paper presents the results of these model computations and calculations of the red line intensity. The 6300 Å emission includes contributions from photoelectron excitation, dissociative recombination, Schumann-Runge photodissociation and thermal electron impact. The variations of these four components for morning and evening twilight between 90–120° solar zenith angles, and their relative contributions to the total 6300 Å emission line intensity, are presented and the total is compared to the observations. For this particular day the Schumann-Runge photodissociation component, calculated using the solar fluxes tabulated by Ackermann (1970), is the dominant component of the morning twilight 6300 Å emission. During evening twilight it is necessary to utilize a lower O₂ density than for the morning twilight in order to bring the calculated and observed 6300 Å emission rates into agreement. The implication that there may be a diurnal variation in the O₂ density at the base of the thermosphere is discussed in the light of available experimental data and current theoretical ideas.  相似文献   

Charge coupled device (CCD) spectroscopy of comets: Tuttle,Stephan-Oterma,Brooks 2, and Bowell     

J.R. Johnson  U. Fink  S.M. Larson 《Icarus》1984,60(2):351-372

Spectra of the four comets, Tuttle, Stephan-Oterma, Brooks 2, and Bowell, were taken with a prototype space telescope charge coupled device (CCD) camera using a 500 × 500 Texas Instruments chip. The spectra extended from 5600 to 10,400 Å at a resolution of $\text{～25}\text{A}\text{?}$. The spatial coverage along the slit was 180^?; its resolution was defined by the seeing ($\text{2–3}{}^{\mathrm{?}}$). Both absolute flux scales and spectral albedos were determined with the data reduction procedure which included flat fielding and sky subtraction. Comet Tuttle displayed extensive emissions by NH₂, the red system of CN, and the C₂ Swan bands as well as emissions by the forbidden oxygen lines [OI] ¹D at 6300 and 6364 Å, and the ionic species H₂O⁺. A feature at 6851 Å has been tentatively identified as the 3-0 band of CS⁺. Notable is the absence of the C₂ Phillips bands whose transitions are optimally placed in our spectrum. The much dustier comet, Stephan-Oterma showed emissions by CN, NH₂, and [OI] while only [OI] could be discerned in the noisier Brooks 2 spectrum. The fresh comet Bowell exhibited an unusually extended coma with an albedo times cross section two orders of magnitude larger than the other comets, a very flat albedo spectrum, and no emission features. For Tuttle and Stephan-Oterma, CN and NH₂ column densities using a number of bands were calculated. The CN band intensity ratios show good agreement with theoretical fluorescence models. The spatial profiles for CN and NH₂ were compared to two step Haser model decay calculations. The scale lengths most consistent with the data were compared with values previously reported and with values expected for various photodissociation reactions. Production rates were calculated for CN and NH₂. These should be less model dependent because of the simultaneous collection of spectral and spatial information. The production rate ratios of the parents of CN and NH₂ to the parent of OH are several orders of magnitude smaller than the solar abundance ratios of C/O and N/O.  相似文献   

Non-LTE models of the accretion disks of UX Ori stars     

L. V. Tambovtseva  V. P. Grinin  O. V. Kozlova 《Astrophysics》1999,42(1):54-63

The results of a non-LTE analysis of a number of spectral lines formed in the accreting envelopes of UX Ori stars are given. The accretion rate is estimated from an analysis of the first three lines of the Balmer series: M _a = 10^?8 ?10^?9 M _⊙ The gas temperature in this region is about 10,000 K. In the immediate vicinity of the star there is a hotter region, with T > 15,000 K, in which the 5876 Å line of neutral helium, observed in the spectra of these stars, is formed. The region of formation of this line has a small geometrical thickness, covers a small fraction of the star’s visible disk, and evidently consists of the site of contact of the accreting gas with the stellar surface. The low gas rotation rates in this region (150–200 km/sec) may mean that rapid rotation of the accreting gas is damped by the star’s magnetic field, which is strong enough to affect the gas stream. We estimate the magnetic field strength in this region to be about 150 G.  相似文献   

A method of calculating 0–20 Å solar X-ray flux and its spectral distribution using 9.1 cm spectroheliograms     

P. R. Sengupta 《Solar physics》1971,17(1):160-173

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   

Atmospheric iron abundance in the primary component of υ Sgr     

V. V. Leushin 《Astronomy Letters》2001,27(10):634-644

Based on the observed energy distribution and line spectrum of the primary component of the binary υ Sgr, we computed blanketed model atmospheres. The atmospheric iron abundance in the primary component of υ Sgr was derived from photographic and CCD spectra. Our analysis confirmed the previously inferred T _eff = 13500 ± 150 K and logg = 2.0 ± 0.5. The microturbulent velocity was found from spectral lines in different spectral ranges to be V _t = 8–12 km s^?1. We refined the mass fractions of light elements: 10^?4 for H, 0.91 for He, 0.013 for C, 0.049 for N, and 0.008 for O. The iron abundance was determined with a high accuracy from Fe I, Fe II, and Fe III lines in the spectral range 4000–7000 Å: log (N(Fe)/∑N _i ) = ?3.80±0.20.  相似文献   

The 6300 Å O^1D airglow and dissociative recombination     

V.B. Wickwar  L.L. Cogger  H.C. Carlson 《Planetary and Space Science》1974,22(5):709-724

Measurements of night-time 6300 Å airglow intensities at the Arecibo Observatory have been compared with dissociative recombination calculations based on electron densities derived from simultaneous incoherent backscatter measurements. The agreement indicates that the nightglow can be fully accounted for by dissociative recombination. Thecomparisons are examined to determine the importance of quenching, heavy ions, ionization above the F-layer peak, and the temperature parameter of the model atmosphere. Comparable fits between the observed and calculated intensities are found for several available model atmos- pheres (e.g. CIRA, Jacchia). The least-squares fitting process, used to make the comparisons, produces comparable fits over a wide range of combinations of neutral densities and of reaction constants. Yet, the fitting places constraints upon the possible combinations: these constraints indicate that the latest laboratory chemical constants and densities extrapolated to a base altitude are mutually consistent. However, by imposing an additional constraint, an aero- nomically derived preference is given for about one O(^1D) per combination. A preference is also given for the lower base densities of O₂ derived from rockets rather than from models. Altitude profiles for the 6300 Å and 5577 Å emissions are deduced. In the early evening, there are no large discrepancies in the fits that might indicate an effect from elicited states of O₊, vibrational excitation of O₂, or both. The technique of comparing observed and cal- culated 6300 Å intensities has considerable potential as an aeronomical tool for examination of other possible sources of emission and for determination of relative changes in the neutral atmosphere.  相似文献   

Measurement of weak airglow emissions with a programmable scanning spectrometer     

John W. Meriwether 《Planetary and Space Science》1979,27(10):1221-1232

We demonstrate how the radiance response of a wavelength scanning instrument may be improved with a programmable scanning system. A minicomputer with a high level language offers a versatile software package that can be readily modified for any specific problem. We illustrate the technique with the application of the one meter Ebert Fastie spectrophotometer at the Arecibo Observatory's airglow facility to the measurements of the peak spectral emissions of the 5200 Å doublet of N(²D) in the nightglow and the 7320 Å doublet of O⁺(²P) in twilight. Typical measurement errors were ±0.2 R and ±0.5 R, respectively. We have also applied this method to measurements of the OH rotational temperature from the ratio of the P₁(2) and the P₁(5) rotational lines in the Meinel 8-3 band and obtained a precision of ±3 K within a time period of 6 min. The required modifications to the wavelength drive were not extensive, the costs were not high, and the technique may be applied to any wavelength scanning instrument in operation today.  相似文献   

Spectral reflectance change and luminescence of selected salts during 2–10 KeV proton bombardment: Implications for Io     

Robert M. Nelson  Douglas B. Nash 《Icarus》1979,39(2):277-285

Radiation damage and luminescence, caused by magnetospheric charged particles, have been suggested by several authors as mechanisms for explaining some of the peculiar spectral/albedo features of Io. We have pursued this possibility by measuring the uv-visual spectral reflectance and luminescent efficiency of several proposed Io surface constituents during 2 to 10-keV proton irradiation at room temperature and at low temperature (120 < T < 140°K). The spectral reflectance of NaCl and KCl during proton irradiation exhibits the well-known F-center absorption bands at 4580 and 5560 Å. Na₂SO₄ shows a generalized darkening which increases toward longer wavelengths. NaNO₃ shows a spectral reflectance change indicative of the partial alteration of NaNo₃ to NaNo₂. NaNO₂ shows no change. The luminescent efficiencies of NaCl and KCl are ～10^?4 at 300°K and increase by one-half order of magnitude at ～130°K. The efficiencies of K₂CO₃, Na₂CO₃, Na₂SO₄, and NaNO₃ are 10^?4, 10^?4, 10^?5 and 10^?6, respectively, at 300°K and they all decrease by one-half order of magnitude at ～130°K. These results indicate that magnetospheric proton irradiation of Io could cause spectral features in its observed ultraviolet and visible reflection spectrum if salts such as those studied here are present on its surface. However, because the magnitude of these spectral effects is dependent on competing factors such as surface temperature, incident particle energy flux, solar bleaching effects, and trace element abundance, we are unable at this time to make a quantitative estimate of the strength of these spectral effects on Io. The luminescent efficiencies of pure samples that we have studied in the laboratory suggest that charged-particle induced luminescence from Io's surface might be observable by a spacecraft such as Voyager when viewing Io's dark side.  相似文献