Description: This study presents a multi-stream superthermal electron transport model for the Mars space environment. This model includes the magnetic inhomogeneity effects, which is vital to understand electron motion around Mars. The convergence tests on the step sizes of variables are carried out and appropriate grid setups are determined. In addition, we have examined three physical parameters, F 10.7 values, thermal electron/plasma density and neutral densities. Through the investigation of F 10.7 values, an interesting fact about the Hinteregger model is found that the photon flux of each wavelength is scaled differently. The resultant photoelectron fluxes also show a non-uniform percentage of increase. The results of plasma density and neutral densities tests are consistent with previous theories, such as the expected degradation of fluxes in the low energy range with increased thermal electron/plasma density, and the elevated peak altitude of photoelectron fluxes with increased neutral densities. The examination of these physical parameters indicates the model's ability to simulate various environments and verifies the model's performance. Finally, a data-model comparison is carried out and the modeled omni-directional fluxes agree well (within a factor of 2) with the observation.

Description: No abstract is available for this article.

Description: Ion temperatures as a function of the x - and y -axes in the Geocentric Solar Magnetospheric (GSM) coordinate system and time are available for 76 geomagnetic storms that occurred during the period July 2008-December 2013 on CDAWeb. The method for mapping energetic neutral atom data from the Two Wide-angle Imaging Spectrometers (TWINS) mission to the GSM equatorial plane and subsequent ion temperature calculation are described here. The ion temperatures are a measure of the average thermal energy of the bulk ion population in the 1–40 keV energy range. These temperatures are useful for studies of ion dynamics, for placing in situ measurements in a global context, and for establishing boundary conditions for models of the inner magnetosphere and the plasma sheet. ©2015. American Geophysical Union. All Rights Reserved.

Description: The magnitude of anthropogenic influence, especially dam regulation, on hydrological system is of scientific and practical value for large river management. As the largest dam in the world by far, Three Gorges Dam (TGD) is expected to be a strong evidence on dam impacts on downstream hydrological regime. In this study, statistical methods are performed on the pre- and post-TGD daily hydrological data at Yichang, Hankou and Datong station to detect the daily, monthly, yearly and spatial fluctuations in river hydrology along the Yangtze River during the period of 2000–2013. It is found that TGD makes a significant hydrological variation along the Yangtze River following the dam operation since 2003. Specifically, the daily discharge and water level are gathered to normal event ranges with less extreme events than before 2003. Both maximum and minimum daily water level at the study stations have decreased due to TGD-induced riverbed incision. The operation of TGD shifts the maximum monthly discharge and water level from August to July at Yichang station. The significance of TGD effect on discharge and water level relationship presents spatial variation. The rating curves at upstream reach experience the most significant effects with a substantial upward shift, while those at lower reach only suggest slight modification. Of the potential drivers considered in this study, dam regulation is responsible for the changes in downstream river hydrology. Moreover, the tributary and adjoining riparian lakes of the Yangtze River contribute to weaken the effect of TGD on downstream hydrological behavior.

Description: We report here on the relationship between titanium abundance and its spectral features on the Moon, using 36 craters exposed in Sinus Iridum, a landing site for China's Lunar Exploration Program. Six absorption parameters (Full Wave at Half Maximum (FWHM), absorption depth (D), absorption position (λ), absorption area (A), absorption asymmetry (S) and (R min ) at the wavelength of 500-550 nm were computed, and the lowest reflectance values (R min ) to characterize the properties of titanium abundance and its spectral features were calculated. The correlation between R min and TiO 2 abundance calculated by Clementine multispectral images is 0.812, and a second-order polynomial fits the data better with a correlation of 0.837. The TiO 2 abundance inversed by the CE-1 IIM data is thus relatively higher than that revealed by the Clementine data. This good correlation between R min and TiO 2 abundance may thus be used very effectively to estimate the Ti distribution on the surface of the Moon by IIM hyper-spectral data.

Description: The Panoramic Cameras on NASA's Mars Exploration Rovers have each returned more than 17000 images of their calibration targets. In order to make optimal use of this dataset for reflectance calibration, a correction must be made for the presence of airfall dust. Here we present an improved dust correction procedure based on a two-layer scattering model and we present a dust reflectance spectrum derived from long-term trends in the dataset. The dust on the calibration targets appears brighter than dusty areas of the Martian surface. We derive detailed histories of dust deposition and removal revealing two distinct environments: At the Spirit landing site half the year is dominated by dust deposition, the other half by dust removal, usually in brief, sharp events. At the Opportunity landing site the Martian year has a semiannual dust cycle with dust removal happening gradually throughout two removal seasons each year. The highest observed optical depth of settled dust on the calibration target is 1.5 on Spirit and 1.1 on Opportunity (at 601 nm). We derive a general prediction for dust deposition rates of 0.004 +/− 0.001 in units of surface optical depth deposited per sol per unit atmospheric optical depth. We expect this procedure to lead to improved reflectance-calibration of the Panoramic Camera dataset. In addition it is easily adapted to similar datasets from other missions in order to deliver improved reflectance calibration as well as data on dust reflectance properties and deposition and removal history.

Description: The abundance of atmospheric oxygen and its evolution through Earth's history is a highly debated topic. The earliest change of the Mo concentration and isotope composition of marine sediments are interpreted to be linked to the onset of the accumulation of free O 2 in Earth's atmosphere. The O 2 concentration needed to dissolve significant amounts of Mo in water is not yet quantified, however. We present laboratory experiments on pulverized and surface cleaned molybdenite (MoS 2 ) and a hydrothermal breccia enriched in Mo-bearing sulphides using a glove box set up. Duration of an experiment was 14 days and first signs of oxidation and subsequent dissolution of Mo compounds start to occur above an atmospheric oxygen concentration of 72 ± 20 ppmv (i.e. 2.6 to 4.6 × 10 −4 PAL). This experimentally determined value coincides with published model calculations supporting atmospheric O 2 concentrations between 1 × 10 −5 to 3 × 10 −4 PAL prior to the great oxidation event and sets an upper limit to the molecular oxygen needed to trigger Mo accumulation and Mo isotope variations recorded in sediments. In combination with the published Mo isotope composition of the rock record, this result implies an atmospheric oxygen concentration prior to 2.76 Ga of below 72 ± 20 ppmv.

Description: After the 11 March 2011 earthquake and tsunami off the coast of Tohoku, the ionospheric signature of the displacements induced in the overlying atmosphere has been observed by ground stations in various regions of the Pacific Ocean. We analyze here the data of radio-occultation satellites, detecting the tsunami-driven gravity wave for the first time using a fully space-based ionospheric observation system. One satellite of the COSMIC constellation recorded an occultation in the region above the tsunami 2 and half hours after the earthquake. The ionosphere was sounded from top to bottom, thus providing the vertical structure of the gravity wave excited by the tsunami propagation, observed as oscillations of the ionospheric Total Electron Content (TEC). The observed vertical wavelength was about 50 km, with maximum amplitude exceeding 1 TECU when the occultation reached 200 km height. We compared the observations with synthetic data obtained by summation of the tsunami-coupled gravity normal modes of the Earth/Ocean/atmosphere system, which models the associated motion of the ionosphere plasma. These results provide experimental constraints on the attenuation of the gravity wave with altitude due to atmosphere viscosity, improving the understanding of the propagation of tsunami-driven gravity waves in the upper atmosphere. They demonstrate that the amplitude of the tsunami can be estimated to within 20% by the recorded ionospheric data.

Description: The Horizontal Wind Model (HWM) has been updated in the thermosphere with new observations and formulation changes. These new data are ground-based 630-nm Fabry-Perot Interferometer (FPI) measurements in the equatorial and polar-regions, as well as cross-track winds from the Gravity Field and Steady State Ocean Circulation Explorer (GOCE) satellite. The GOCE wind observations provide valuable wind data in the twilight regions. The ground-based FPI measurements fill latitudinal data gaps in the prior observational database. Construction of this reference model also provides the opportunity to compare these new measurements. The resulting update (HWM14) provides an improved time dependent, observationally based, global empirical specification of the upper atmospheric general circulation patterns and migrating tides. In basic agreement with existing accepted theoretical knowledge of the thermosphere general circulation, additional calculations indicate that the empirical wind specifications are self-consistent with climatological ionosphere plasma distribution and electric field patterns.

Description: Long-term vertical seafloor displacements and geostrophic changes in the water column height could be easily monitored if pressure meters were less susceptible to drift. Currently, these signals, which have typical amplitudes from decimeters to less than one millimeter per year, cannot be differentiated from instrumental drift. In this paper, we introduce and outline a new constructional concept for an ocean bottom pressure meter (OBP) that aims for unequivocal detection and monitoring of long-term trends. The concept is based on a differential pressure sensor that measures the pressure difference between the environment and a reference pressure within a sealed volume. This sealed volume conserves the instantaneous pressure at the moment of its closure at the monitoring location in a temperature-compensated manner. Furthermore, the approach enables easy in situ calibration of the differential pressure gauge by simply opening the reference pressure chamber to the environment and checking the zero point offset.