Jupiter's hydrocarbon polar brightening: Discovery of 3-micron line emission from south polar CH4, C2H2, and C2H6

Jupiter exhibits bright H⁺₃ auroral arcs at 3-4 microns that cool the hot (>1000 K) ionosphere above the ∼¹⁰−7 bar level through the infrared bands of this trace constituent. Below the ¹⁰−7 bar level significant cooling proceeds through infrared active bands of CH₄, C₂H₂, and C₂H₆. We report the discovery of 3-micron line emission from these hydrocarbon species in spectra of the jovian south polar region obtained on April 18 and 20, 2006 (UT) with CGS4 on the United Kingdom Infrared Telescope. Estimated cooling rates through these molecules are 7.5×¹⁰−3, 1.4×¹⁰−3, and , respectively, for a total nearly half that of H⁺₃. We derive a temperature of 450 ± 50 K in the ¹⁰−7-¹⁰−5 bar region from the C₂H₂ lines.     

Titan at 3 microns: Newly identified spectral features and an improved analysis of haze opacity

We have reanalyzed the high-resolution spectrum of Titan between 2.87 and 3.12 μm observed with NIRSPEC/Keck II on 2001 Nov. 21 in southern summer, using updated CH₃D and C₂H₆ line-by-line models. From new synthetic spectra, we identify all but a few of the previously unidentified significant absorption spectral features in this wavelength range as due to these two species, both of which had been previously detected by Voyager and ground-based observations at other wavelengths. We also derive opacities and reflectivities of haze particles as functions of altitude for the 2.87-2.92 μm wavelength range, where Titan's atmosphere is partially transparent down to the surface. The extinction per unit altitude is observed to increase from 100 km (∼8 mbar) toward lower altitude. The derived total optical depth is approximately 1.1 for the 2.87-2.92 μm range. At wavelengths increasing beyond 2.92 μm the haze layers become much more optically thick, and the surface is rapidly hidden from view. These conclusions apply to equatorial and southern-temperate regions on Titan, excluding polar regions. We also find it unlikely that there is a large enhancement of the tropospheric CH₄ mole fraction over the value reported from analysis of the Huygens/GCMS observations.     

Observations of soft electron flux during SAR arc event

Attempts to test the validity of the soft electron flux hypothesis for the excitation of SAR arcs have heretofore met with no apparent success. However, observations of other emissions during the times of some SAR arcs repeatedly favour the presence of the soft electron flux in the topside ionosphere.Although no new cases of coincident measurements of SAR arc intensities and the corresponding soft electron flux values are available, an instance has been analyzed in which an SAR arc was examined shortly after an OGO 6 measurement of the soft electron flux. The SAR arc observations were then interrupted by the weather, but in view of the behaviour of the electron flux during the arc development it is believed that this event lends strong observational support to the hypothesis that soft electrons can be an excitation source for SAR arcs.In the case considered, the precipitation of soft electron flux peaks at about the same location and time of occurrence as the SAR arc. The peak value is found to be 5.2 × 10⁸ cm^?2 sec^?1, which is more than adequate to excite the observed arc.     

Turbulence Heating for Protons in High-Speed Solar Wind

In high-speed solar wind, propagating Alfvén waves can be transferred into fast magnetosonic waves. When both the magnetic field strength and Alfvén wave velocity approach zero, fast magnetosonic waves will be transferred into ion-acoustic waves. As the phase velocity of ion-acoustic waves is slightly greater than the thermal velocity of protons, the turbulence energy of ion-acoustic waves can largely be absorbed by protons and can cause the mean temperature of protons to be greater than that of electrons by stochastic turbulence heating of ion-acoustic waves for protons.     

List of Forthcoming Papers

Other Index

List of Forthcoming Papers     

Application of Astronomic Time-latitude Residuals in Earthquake Prediction

After the earthquake (Ms = 6.1) occurred in Luquan county of Yunnan province on April 18, 1985, the relationship between major earthquakes and astronomical time-latitude residuals (ATLR) of a photoelectric astrolabe in Yunnan Observatory was analyzed. ATLR are the rest after deducting the effects of Earth’s whole motion from the observations of time and latitude. It was found that there appeared the anomalies of the ATLR before earthquakes which happened in and around Yunnan, a seismic active region. The reason of the anomalies is possibly from change of the plumb line due to the motion of the groundmass before earthquakes. Afterwards, using studies of the anomalous characters and laws of ATLR, we tried to provide the warning information prior to the occurrence of a few major earthquakes in the region. The significant synchronous anomalies of ATLR of the observatory appeared before the earthquake of magnitude 6.2 in Dayao county of Yunnan province, on July 21, 2003. It has been again verified that the anomalies possibly provide the prediction information for strong earthquakes around the observatory.     

Long-Term Soft X-Ray Variability of Active Galaxies. I. Mrk 926

We present a detailed analysis of the soft X-ray (0.1–2.4 keV) emission of the Seyfert 1 galaxy Mrk 926 in order to investigate its long-term variation. The X-ray data were obtained from the ROSAT-PSPC archives. The light curves show a gradual decrease of brightness for a time scales of 36months with the exception of a single flare event superimposed on the gradual variation of brightness. The light variations for three different energy bands and the hardness ratios were investigated to search for correlations; no correlation was confirmed. In order to compare spectral variations during the flare event with other periods, the spectral parameters were determined. Results of our analysis are discussed within the framework of the accretion disk phenomenon. This revised version was published online in July 2006 with corrections to the Cover Date.     

J1128+592: a highly variable IDV source

Short time‐scale radio variations of compact extragalactic radio quasars and blazars known as IntraDay Variability (IDV) can be explained in at least some sources as a propagation effect; the variations are interpreted as scintillation of radio waves in the turbulent interstellar medium of the Milky Way. One of the most convincing observational arguments in favor of a propagation‐induced variability scenario is the observed annual modulation in the characteristic time scale of the variation due to the Earth's orbital motion. So far there are only two sources known with a well‐constrained seasonal cycle. Annual modulation has been proposed for a few other less well‐documented objects. However, for some other IDV sources source‐intrinsic structural variations which cause drastic changes in the variability time scale were also suggested. J1128+592 is a recently discovered, highly variable IDV source. Previous, densely time‐sampled flux‐density measurements with the Effelsberg 100‐m radio telescope (Germany) and the Urumqi 25‐m radio telescope (China), strongly indicate an annual modulation of the time scale. The most recent 4 observations in 2006/7, however, do not fit well to the annual modulation model proposed before. In this paper, we investigate a possible explanation of this discrepancy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Contribution of close double white dwarfs to the Galactic gravitational wave foreground

This paper provides new detailed specifics and characteristics of the close double white dwarfs (CDWDs) LISA foreground noise floor using the newest information on the astrophysics with binary population algorithms, which were judged to satisfy the observations. We use the binary population synthesis approach of CDWDs in combination with the latest findings of synthesis models from Han (Mon. Not. R. Astron. Soc. 296:1019, 1998), here, specifically formation by the three evolutionary channels of (a) stable Roche lobe overflow plus common envelope (RLOF?+?CE), (b) CE plus CE, (c) exposed core plus CE. We collect resulting CDWDs in the frequency range of 10^?8 Hz to 10^?2 Hz and compare strength and number statistics per resolvable frequency bin to derive the properties of the noise floor and the nature of possible outliers that may become individually resolvable. We find resolvable outliers to be solely produced by CE?+?CE evolution; the other two channels contribute only to the unresolvable foreground noise. Within the CE?+?CE evolution a detailed look into the chemical buildup of the stars reveals dominantly double helium (He?+?He) WDs or carbon-oxygen CO?+?He WDs.