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111.
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Carl Heiles 《Astrophysics and Space Science》2004,292(1-4):77-88
We review observations of the physical properties of the diffuse ISM HI components, namely the Cold and Warm Neutral Media (CNM and WNM). There is somewhat more WNM than CNM, and at least half of the WNM is not thermally stable. The CNM has typical turbulent Mach number 3. Magnetic fields in the CNM are not as large as expected from the classical flux-freezing argument; neither are magnetic fields always strong enough for the Alfven velocity to equal the turbulent velocity. Nevertheless, they are usually strong enough to put CNM clouds in the magnetically subcritical regime. We identify a probable new source of turbulence for the diffuse ISM. We discuss one very cold cloud that has considerable internal turbulence and, because of its extreme thinness ~0.05 pc, a turbulent crossing time of only ~5 × 104 yr. 相似文献
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Ekaykin A. A. Teben’kova N. A. Lipenkov V. Ya. Tchikhatchev K. B. Veres A. N. Richter A. 《Russian Meteorology and Hydrology》2020,45(2):132-140
Russian Meteorology and Hydrology - It is shown that the snow stake measurements in central Antarctica systematically underestimate the value of the snow build-up. Two methods for the calculation... 相似文献
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M. J. Richter J. R. Graham G. S. Wright D. M. Kelly J. H. Lacy 《Astrophysics and Space Science》1995,233(1-2):67-70
We present spectroscopy of the molecular shock in the supernova remnant IC 443. The H2 level populations in IC 443 are nearly identical to Orion Peak 1 (Brand et al. 1988; Parmar et al. 1994) and are consistent with a partially dissociative J-shock. The similarity with Orion suggests the shock processes which dominate the emission in both regions are essentially identical. 相似文献
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Near-simultaneous R- and J-band photometric measurements of the short-period Comets 2P/Encke and the Deep Impact mission target 9P/Tempel 1 were obtained. The resulting R-J colors are +0.82±0.08 mag and +1.46±0.13 mag for Encke and Tempel 1, respectively. Tempel 1's color is redder than the solar R-J color index of +0.76. The Tempel 1 observations directly detected the nucleus while the Encke observations likely suffered from coma contamination. 相似文献
119.
Hydrogen peroxide (H2O2) has been suggested as a possible oxidizer of the martian surface. Photochemical models predict a mean column density in the range of 1015-1016 cm−2. However, a stringent upper limit of the H2O2 abundance on Mars (9×1014 cm−2) was derived in February 2001 from ground-based infrared spectroscopy, at a time corresponding to a maximum water vapor abundance in the northern summer (30 pr. μm, Ls=112°). Here we report the detection of H2O2 on Mars in June 2003, and its mapping over the martian disk using the same technique, during the southern spring (Ls=206°) when the global water vapor abundance was ∼10 pr. μm. The spatial distribution of H2O2 shows a maximum in the morning around the sub-solar latitude. The mean H2O2 column density (6×1015 cm−2) is significantly greater than our previous upper limit, pointing to seasonal variations. Our new result is globally consistent with the predictions of photochemical models, and also with submillimeter ground-based measurements obtained in September 2003 (Ls=254°), averaged over the martian disk (Clancy et al., 2004, Icarus 168, 116-121). 相似文献
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Jagdish Krishnaswamy Daniel D. Richter Patrick N. Halpin Michael S. Hofmockel 《水文研究》2001,15(12):2237-2257
An Erratum has been published for this article in Hydrological Processes 16(5) 2002, 1130–1131. Humid tropical regions are often characterized by extreme variability of fluvial processes. The Rio Terraba drains the largest river basin, covering 4767 km2, in Costa Rica. Mean annual rainfall is 3139±419sd mm and mean annual discharge is 2168±492sd mm (1971–88). Loss of forest cover, high rainfall erosivity and geomorphologic instability all have led to considerable degradation of soil and water resources at local to basin scales. Parametric and non‐parametric statistical methods were used to estimate sediment yields. In the Terraba basin, sediment yields per unit area increase from the headwaters to the basin mouth, and the trend is generally robust towards choice of methods (parametric and LOESS) used. This is in contrast to a general view that deposition typically exceeds sediment delivery with increase in basin size. The specific sediment yield increases from 112±11·4sd t km?2 year?1 (at 317·9 km2 on a major headwater tributary) to 404±141·7sd t km?2 year?1 (at 4766·7 km2) at the basin mouth (1971–92). The analyses of relationships between sediment yields and basin parameters for the Terraba sub‐basins and for a total of 29 basins all over Costa Rica indicate a strong land use effect related to intensive agriculture besides hydro‐climatology. The best explanation for the observed pattern in the Terraba basin is a combined spatial pattern of land use and rainfall erosivity. These were integrated in a soil erosion index that is related to the observed patterns of sediment yield. Estimated sediment delivery ratios increase with basin area. Intensive agriculture in lower‐lying alluvial fans exposed to highly erosive rainfall contributes a large part of the sediment load. The higher elevation regions, although steep in slope, largely remain under forest, pasture, or tree‐crops. High rainfall erosivity (>7400 MJ mm ha?1 h?1 year ?1) is associated with land uses that provide inadequate soil protection. It is also associated with steep, unstable slopes near the basin mouth. Improvements in land use and soil management in the lower‐lying regions exposed to highly erosive rainfall are recommended, and are especially important to basins in which sediment delivery ratio increases downstream with increasing basin area. Copyright © 2001 John Wiley & Sons, Ltd. 相似文献