The global distribution of total ozone: TOMS satellite measurements

The general behavior of total ozone by season and latitude was known before 1930 through the pioneering observations by G. M. B. Dobson. The ozone record at Oxford and other European stations was dominated by an annual cycle and by irregular short term fluctuations. The amplitude and phase of the annual cycle were determined at representative latitudes in both hemispheres. However, the short term variations appeared to be of meteorological origin, although the specific cause could not be identified. Data from the Total Ozone Mapping Spectrometer (TOMS) on the Nimbus 7 spacecraft, with global coverage at an average spatial resolution of 66 km, can now be used to completely map the total ozone field. These maps demonstrate that troughs and ridges in the upper troposphere are responsible for the large, short term ozone variations found at middle latitudes, while in the troplcs, the steady, low ozone levels show broad scale structure associated with the Hadley circulation.     

The development of a neural network based short term foF2 forecast program

The maximum electron density is related to the critical frequency of the F2 layer in the ionosphere, foF2, which is a measurable quantity. Neural Networks (NNs) were trained to forecast foF2 using 24 years of foF2 data from Grahamstown (26.5°E, 33.3°S), South Africa.This paper is in two parts. The first part describes how NNs were used to find the optimum input parameters required to forecast foF2 in the short term. Several NNs were trained with different data in order to find the optimum combination of ionospheric indices (I-indices) to use as inputs. The rms error between the measured and predicted output values was used for determing when a combination of input parameters was optimum. The I-indices were based on recent and archived values of foF2. It was found that the NN requires short term and long term indicators in order to forecast foF2. The short term indicators were the values of foF2 for the previous 1, 2, 3, and 4 hours. The longer term indicators were 30-day running mean values of foF2. These values were based on the running means of the 4 hours ahead of the most recently measured (current) value, ending on the previous days value. We used the rms error between the measured and predicted values of foF2 as an indicator of how well the NN had trained.In the second part it is shown how two networks can be used together to provide a short term forecast of foF2, given recently measured values, and how the rms errors increase with increasing forecast delay time. Using day number, hour, and the above mentioned short and long term indicators as inputs, a Neural Network (NN1) was trained to forecast the value of foF2 for 1, 2, 3, 4 and 25 hours ahead. The errors from these 5 outputs were then squared and used as targets to train a second Neural Network (NN2) using the same input data. The square root of the outputs of NN2 were then used as an estimate of the rms errors in the forecast of NN1. A working version of this program can be viewed on http://phlinux.ru.ae.za/hoia .     

Heating experiments of the Tagish Lake meteorite: Investigation of the effects of short‐term heating on chondritic organics

We present in this study the effects of short‐term heating on organics in the Tagish Lake meteorite and how the difference in the heating conditions can modify the organic matter (OM) in a way that complicates the interpretation of a parent body's heating extent with common cosmothermometers. The kinetics of short‐term heating and its influence on the organic structure are not well understood, and any study of OM is further complicated by the complex alteration processes of the thermally metamorphosed carbonaceous chondrites—potential analogues of the target asteroid Ryugu of the Hayabusa2 mission—which had experienced posthydration, short‐duration local heating. In an attempt to understand the effects of short‐term heating on chondritic OM, we investigated the change in the OM contents of the experimentally heated Tagish Lake meteorite samples using Raman spectroscopy, scanning transmission X‐ray microscopy utilizing X‐ray absorption near edge structure spectroscopy, and ultraperformance liquid chromatography fluorescence detection and quadrupole time of flight hybrid mass spectrometry. Our experiment suggests that graphitization of OM did not take place despite the samples being heated to 900 °C for 96 h, as the OM maturity trend was influenced by the heating conditions, kinetics, and the nature of the OM precursor, such as the presence of abundant oxygenated moieties. Although both the intensity of the 1s?σ* exciton cannot be used to accurately interpret the peak metamorphic temperature of the experimentally heated Tagish Lake sample, the Raman graphite band widths of the heated products significantly differ from that of chondritic OM modified by long‐term internal heating.     

冕洞的地磁效应

分析了２２太阳活动周（１９８６．１—１９９５．６；ＣＲ１７７１—ＣＲ１８９８）冕洞对地磁扰动的长期效应和短期效应。作为长期效应，赤道冕洞数和面积指数随太阳活动周的演化与同期的地磁Ａｐ指数的长期变化基本一致，二者在α＝０．０１的信度水平上密切相关，表明赤道冕洞不仅对低年的磁扰有贡献，而且对峰年期间地磁扰动的贡献也是不可忽视的。对冕洞的短期地磁效应的研究表明，不论哪种类型的冕洞，在它们过中经后的１—４天，地磁Ａｐ指数都有不同程度的增长；大冕洞比小冕洞引起的地磁效应较强烈；跨越赤道的冕洞比未跨越赤道的同级冕洞引起的地磁效应较强烈     

Yardang identification in Magellan imagery of Venus

Yardang complexes should appear as dark lineation groups in Magellan imagery of Venus. Such structures are not found in preliminary analysis of Magellan imagery.     

On the detection of high‐frequency oscillations in short gamma‐ray bursts

In this work we present the results of an investigation aimed at a search for an oscillatory phenomenon during short gamma‐ray bursts. The wavelet technique, used for this analysis, is applied to the data from the BATSE 3B catalogue. We have detected oscillations, which periods are found to be in the milliseconds range and their amplitudes up to dozens of percents. A possible scenario for such a phenomenon is the coalescence of stellar‐mass black holes and neutron stars. During the coalescence process the matter orbiting the black hole produces rapid, periodic phenomena. Such system will also emit gravitational waves which cause the orbital radius to decrease and leads to the emission of a chirp of radiation. Estimates lead to a timescale of milliseconds for the coalescence process and oscillation frequencies of hundreds of Hz. The gamma‐ray bursts considered in this paper, show both frequencies and survival times of oscillations close to the mentioned values. A chirp phenomenon is also present. We therefore argue in favor of the black hole – neutron star coalescence as a scenario for the production of short gamma‐ray bursts (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

原子时的小波分解算法

时间尺度的就是根据一组原子钟的数据,用统计的方法计算出平均的时间尺度。其目的是使综合时间尺度的噪声最小。一般的原子时算有脱离经典加权的局限性,只能抑制原子钟的栽一种噪声。运用小波分解的方法建立以分解原子时,将原子信号在小汉域按频率尺度分解原,然后在不同频率范围加权,这种方法不但考虑不同原子钟在同一个频率分量的不同稳定度,而且考虑不同频率分量的不同稳定度,它有着独特的优越性。     

Color enhanced imagery of major geological features on Mars

Red, green, and violet filtered color Viking imagery of Mars provides further detail of the planet's surface. Major geological features discussed here are the Tharsis volcanoes, the Labyrinthus Noctis-Valles Marineris region, dark-floored craters, Kasei Vallis, and Mareotis Fossae-Tempe Fossae. The imagery provides further evidence that dark material is mostly subsurface material underlying light material.     

A Golden Era for Astronomy: The Advent of CCDs and Infrared Arrays

The advent of solid-state imaging devices transformed astronomy. Beginning with the introduction into astronomy of charge-coupled devices in 1976, followed a decade later by infrared arrays, astronomers gained access to near-perfect imaging devices. The consequences have been nothing short of revolutionary, perhaps especially so in the infrared. Witness, for example, the spectacular pictures from the Hubble Space Telescope cameras, or the impressive infrared imagery from the 2MASS project. Within the last decade CCD formats deployed or planned for use in ground-based cameras have become huge. Infrared mosaics, stimulated by the Next Generation Space Telescope, are coming soon. In addition, new technologies such as CMOS (Complementary Metal Oxide Semiconductors) and STJs (Superconductiong Tunnel Junctions) are being developed and the future of astronomical detectors looks very exciting, especially in an era of giant telescopes performing at their diffraction-limit. This revised version was published online in July 2006 with corrections to the Cover Date.     

Observation of solar particle fluxes over extended solar longitudes

Detailed particle observations from various Pioneer Spacecrafts located at different heliolongitudes during the complex solar flare events of March 30–April 10, 1969 have been utilised to investigate the energy dependence of azimuthal gradients of cosmic ray particles and its effect on the decay of the flare intensity. For an observer located to the east of the centroid of the population, the azimuthal corotation term and the convection term will be additive, resulting in a short decay time constant. An observer located to the west of the centroid of the population will experience a much longer decay time constant, the corotation term partially or completely compensating the loss of particles due to convection. At very low energies, the azimuthal corotation term may even be more than the convection term, thus resulting in a rise in intensity instead of decay during late in the event. Using the relationship showing the dependence of the spectral exponent of the cosmic ray flux late in a flare event on the azimuth from the centroid of the population given by McCracken et al., the energy dependence of the decay time constant and the cross-over energy at which the azimuthal gradient term equals the convection term are investigated. The experimental observations are shown to be generally consistent with the theoretical picture, confirming the importance of convection and the azimuthal gradient in determining the decay profile of flare events.On leave from Physical Research Laboratory, Ahmedabad, India.Now at CSIRO, G.P.O. Box 136, North Ryde, N.S.W., Australia.     

23周太阳活动预报方法研究

文中评价了２３ 周以来北京天文台的短期太阳活动预报工作,Ｘ 射线耀斑的报准率为８９ ．６ ％ ,太阳质子事件的报准率为６２ ．５ ％ 。另外,还叙述了第２３ 周峰年北京天文台太阳活动预报工作的选题（ 包括研究课题和实施课题     

The evolution of polycyclic aromatic hydrocarbons under simulated inner asteroid conditions

Large polycyclic aromatic hydrocarbons (PAHs) are an important component of the interstellar medium. PAHs have been identified in the soluble and insoluble matter of carbonaceous chondrites (CCs). Here, we study the evolution of PAHs under conditions relevant to the interiors of asteroids and compare our results to PAHs observed in CCs. We have performed long‐term and short‐term hydrothermal experiments, in which we exposed PAH‐mineral mixture analogs of meteorites to temperature conditions representative of those predicted for asteroids interiors. Our results show that small PAHs with melting points within the aqueous alteration temperature of CCs form carbonaceous spherules in the presence of water. In this work, we describe the microstructure and morphology of these spherules. We discuss the similarities and differences compared to globules isolated from CCs.     

Relativistic and the first sectorial harmonics corrections in the critical inclination

The problem of the critical inclination is treated in the Hamiltonian framework taking into consideration post-Newtonian corrections as well as the main correction term of sectorial harmonics for an earth-like planet. The Hamiltonian is expressed in terms of Delaunay canonical variables. A canonical transformation is applied to eliminate short period terms. A modified critical inclination is obtained due to relativistic and the first sectorial harmonics corrections.     

The absence of yardangs on Venus

Large yardang formations, found on Earth and Mars, have not been detected in Venera 15/16 imagery of Venus.     

Geologic context of in situ rocky exposures in Mare Serpentis, Mars: Implications for crust and regolith evolution in the cratered highlands

Global acquisition of infrared spectra and high-resolution visible and infrared imagery has enabled the placement of compositional information within stratigraphic and geologic context. Mare Serpentis, a low albedo region located northwest of Hellas Basin, is rich in spectral and thermophysical diversity and host to numerous isolated exposures of in situ rocky material. Most martian surfaces are dominated by fine-grained particulate materials that bear an uncertain compositional and spatial relationship to their source. Thus location and characterization of in situ rock exposures is important for understanding the origin of highland materials and the processes which have modified those materials. Using spectral, thermophysical and morphologic information, we assess the local and regional stratigraphy of the Mare Serpentis surface in an effort to reconstruct the geologic history of the region. The martian highlands in Mare Serpentis are dominated by two interspersed surface units, which have distinct compositional and thermophysical properties: (1) rock-dominated surfaces relatively enriched in olivine and pyroxene, and depleted in high-silica phases, and (2) sediment or indurated material depleted in olivine and pyroxene, with relatively higher abundance of high-silica phases. This is a major, previously unrecognized trend which appears to be pervasive in the Mare Serpentis region and possibly in other highland areas. The detailed observations have led us to form two hypotheses for the relationship between these two units: either (1) they are related through a widespread mechanical and/or chemical alteration process, where less-mafic plains materials are derived from the mafic bedrock, but have been compositionally altered in the process of regolith formation, or (2) they are stratigraphically distinct units representing separate episodes of upper crust formation. Existing observations suggest that the second scenario is more likely. In this scenario, plains materials represent older, degraded, and possibly altered, “basement” rock, whereas the rocky exposures represent later additions to the crust and are probably volcanic in origin. These hypotheses should be further testable with decimeter-resolution imagery and meter-resolution short wavelength infrared spectra.     

Spots on FK Com: active longitudes and “flip‐flops”

We have earlier investigated the surface structures of a late‐type, single, giant FK Com for the years 1994–1998 using Doppler imaging. These surface temperature maps revealed long‐lived active regions at high latitudes. Long‐term photometric observations also show that these active regions tend to occur at two permanent active longitudes which are 180 degrees apart from each other, and that the activity switches the longitude with an average period of about 3 years (the “flip‐flop” phenomenon). In this work we present new Doppler maps of FK Com obtained 1998‐2003 and light‐curve maps obtained 2002–2003. These new maps are investigated together with the earlier temperature maps and light‐curve maps, with an aim of further studying the active longitudes, “flip‐flop” phenomenon and surface differential rotation on FK Com. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the difference in short timescale light variation between the high and low states of BL Lac objects

Combining our data for three BL Lac objects obtained in 1993–1995 with other authors' we note that activity is stronger and short timescale variations more frequent during the high than the low state. We propose that the relativistic jet in the AGN may change its orientation with time, and the high state corresponds to smaller angles of inclination to the line of sight, and the low, to larger angles. This explains the difference in behaviour as well as the new phenomenon discovered in the monitoring by Takalo et al.     

Local lunar topography from the Apollo 17 Alse radar imagery and altimetry

The Apollo 17 ALSE VHF radar provided imagery and continuous profiling data around the Moon during two revolutions. The imagery data are used to derive depth and diameter measurements of small craters (diameter <30 km). The profiling data are used to study the topography of a few large craters: the bulged floors in Hevelius, Neper, and Aitken; central peaks in Neper and Buisson; and the depressed floor of Maraldi. The same data provided accurate (better than 25 m) profiles of Mare Crisium and Mare Serenitatis.     

Landform investigation utilizing digitally processed satellite thematic mapper imagery

The potential of remotely sensed imagery for Earth science applications has been widely recognised for many years. However, with the advent of space borne sensors, a totally new perspective from which to view the Earth's surface has been available to such disciplines as geology and geography. Primary in this development was the deployment of the Landsat series of Earth observation satellites with their multispectral scanning capability. Although standard single band imagery and false-colour composites contain much geomorphological detail, a great deal more information can be extracted from the digital output of such scanners if the data is subjected to computer-assisted image processing.     

Stratigraphy in the Mawrth Vallis region through OMEGA, HRSC color imagery and DTM

The Mawrth Vallis region contains an extensive (at least 300 km × 400 km) and thick (?300 m), finely layered (at meter scale), clay-rich unit detected by OMEGA. We use OMEGA, HRSC DTMs derived from stereoscopic imagery, HRSC color imagery and high resolution imagery such as MOC, CTX and HiRISE to characterize the geometry and the composition of the clay-rich unit at the regional scale. Our results show that the clay-bearing unit can be divided into sub-units on the basis of differences in color and composition. In false-color visible imagery, alternating white/bluish and orange/red colored units correspond to a compositional succession of, respectively, Al- and Fe- or Mg-phyllosilicate rich material. Geological cross-sections are presented along the principal outcrops of the region in order to define the stratigraphy of these sub-units. This method shows that the dips of the sub-units are frequently close to the slopes of the present topography, except for scarps visible at the dichotomy boundary, inside impact craters walls, and outcrops inside Mawrth Vallis. In addition to the Al- and Fe- or Mg-phyllosilicate rich sub-units, an altered surface is identified as the lower basement unit. We propose two possible end-member scenarios to explain the derived stratigraphy: (1) alteration of volcaniclastic, aeolian or aqueous layered deposits of various compositions by groundwater, resulting in distinct altered rocks; or (2) Alteration coeval with the deposition of sediments under varying chemical conditions, in wet pedodiagenetic environment.