Pioneer 10 ultraviolet photometer observations of the Jovian hydrogen torus: The angular distribution     

R.W. Carlson  D.L. Judge 《Icarus》1975,24(4):395-399

The Pioneer 10 ultraviolet photometer observations of the Jovian hydrogen torus are analyzed to obtain the angular distribution. The cloud is asymmetric about Io, where the atoms presumably originate, with the greater density occurring in the trailing portion. A simple model which assumes Jeans escape from the atmosphere of Io is developed and compared to the observations. The results suggest that the exospheric temperature is high (～3000 K) and that the ionization lifetime of the cloud atoms is ～1 × 10⁵ sec.  相似文献   

Yield Forecasting of Spring Maize Using Remote Sensing and Crop Modeling in Faisalabad-Punjab Pakistan     

Ishfaq Ahmad  Umer Saeed  Muhammad Fahad  Asmat Ullah  M. Habib ur Rahman  Ashfaq Ahmad  Jasmeet Judge 《Journal of the Indian Society of Remote Sensing》2018,46(10):1701-1711

Real time, accurate and reliable estimation of maize yield is valuable to policy makers in decision making. The current study was planned for yield estimation of spring maize using remote sensing and crop modeling. In crop modeling, the CERES-Maize model was calibrated and evaluated with the field experiment data and after calibration and evaluation, this model was used to forecast maize yield. A Field survey of 64 farm was also conducted in Faisalabad to collect data on initial field conditions and crop management data. These data were used to forecast maize yield using crop model at farmers’ field. While in remote sensing, peak season Landsat 8 images were classified for landcover classification using machine learning algorithm. After classification, time series normalized difference vegetation index (NDVI) and land surface temperature (LST) of the surveyed 64 farms were calculated. Principle component analysis were run to correlate the indicators with maize yield. The selected LSTs and NDVIs were used to develop yield forecasting equations using least absolute shrinkage and selection operator (LASSO) regression. Calibrated and evaluated results of CERES-Maize showed the mean absolute % error (MAPE) of 0.35–6.71% for all recorded variables. In remote sensing all machine learning algorithms showed the accuracy greater the 90%, however support vector machine (SVM-radial basis) showed the higher accuracy of 97%, that was used for classification of maize area. The accuracy of area estimated through SVM-radial basis was 91%, when validated with crop reporting service. Yield forecasting results of crop model were precise with RMSE of 255 kg ha^?1, while remote sensing showed the RMSE of 397 kg ha^?1. Overall strength of relationship between estimated and actual grain yields were good with R² of 0.94 in both techniques. For regional yield forecasting remote sensing could be used due greater advantages of less input dataset and if focus is to assess specific stress, and interaction of plant genetics to soil and environmental conditions than crop model is very useful tool.  相似文献   

Electron excitation and auroral emission parameters     

R. J. R. Judge 《Planetary and Space Science》1972,20(12):2081-2092

Auroral luminosities of the main emission lines in the aurora have been calculated for excitation by an isotopic primary electron flux with spectra of the form J(E) = AE exp (−E/E₁) + B(E₂)E exp (−E/E₁). The variation of emissions from O and N₂⁺ with height are shown, as are the variations of column integrated intensities and pertinent intensity ratios with the characteristic energy E₂, this leading to a method of estimating the electron spectrum from ground observation.  相似文献   

Particle Filter-based assimilation algorithms for improved estimation of root-zone soil moisture under dynamic vegetation conditions   总被引：1，自引：0，他引：1  

Karthik Nagarajan  Jasmeet JudgeWendy D. Graham  Alejandro Monsivais-Huertero 《Advances in water resources》2011,34(4):433-447

In this study, we implement Particle Filter (PF)-based assimilation algorithms to improve root-zone soil moisture (RZSM) estimates from a coupled SVAT-vegetation model during a growing season of sweet corn in North Central Florida. The results from four different PF algorithms were compared with those from the Ensemble Kalman Filter (EnKF) when near-surface soil moisture was assimilated every 3 days using both synthetic and field observations. In the synthetic case, the PF algorithm with the best performance used residual resampling of the states and obtained resampled parameters from a uniform distribution and provided reductions of 76% in root mean square error (RMSE) over the openloop estimates. The EnKF provided the RZSM and parameter estimates that were closer to the truth than the PF with an 84% reduction in RMSE. When field observations were assimilated, the PF algorithm that maintained maximum parameter diversity offered the largest reduction of 16% in root mean square difference (RMSD) over the openloop estimates. Minimal differences were observed in the overall performance of the EnKF and PF using field observations since errors in model physics affected both the filters in a similar manner, with maximum reductions in RMSD compared to the openloop during the mid and reproductive stages.  相似文献   

Measuring proton energies and fluxes using EIT (SOHO) CCD areas outside the solar disk images     

L. V. Didkovsky  D. L. Judge  A. R. Jones  E. J. Rhodes  J. B. Gurman 《Astronomische Nachrichten》2006,327(4):314-320

An indirect proton flux measuring tool based on discrimination of the energy deposited by protons in 128 × 128 pixel EIT CCD areas outside the solar disk images is presented. Single pixel intensity events are converted into proton incident energy flux using modeled energy deposition curves for angles of incidence ±60° in four EIT spatial areas with different proton stopping power. The extracted proton flux is corrected for both the loss of one‐pixel events in the range of angles of incidence as well as for the contribution to the single pixel events resulting from scattered middle‐energy protons (low‐energy or high‐energy particles are stopped by the EIT components or pass through them, accordingly). A simple geometrical approach was found and applied to correct for a non‐unique relation between the proton‐associated CCD output signal and the incident proton energy. With this geometrical approximation four unique proton incident energy ranges were determined as 45–49, 145–154, 297–335, and 390–440 MeV. The indirect proton flux measuring tool has been tested by comparing Solar Energetic Particles (SEP) flux temporal profiles extracted from the EIT CCD frames and downloaded from the GOES database for the Bastille Day (BD) of 2000 July 14 and the more recent 2005 January 20 events. The SEP flux temporal profiles and proton spectra extracted from the EIT in the relatively narrow energy ranges between 45 and 440 MeV reported here are consistent with the related GOES profiles. The four additional EIT extracted ranges provide higher energy resolution of the SEP data. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

The ICE-MOSES experiment: Mapping permafrost zones electrically beneath the Beaufort Sea     

R. N. Edwards  P. A. Wolfgram  A. S. Judge 《Marine Geophysical Researches》1988,9(3):265-290

A novel variation of the geophysical technique known as MOSES, for Magnetometric Off-Shore Electrical Sounding, has been developed to map the electrical properties of the sea floor in Aretic regions. The particular target is the permafrost layer under the Beaufort Sea, a layer containing frozen or partially frozen sediment from 100 to 600 m thick underlying shallow sea water, typically 10 to 100 m deep, and several tens of metres of soft sediment. A detailed knowledge of the location and physical properties of the permafrost layer is essential for accurate interpretation of reflection seismic data. The permafrost can contain pockets, regions or layers of gas hydrate. The latter is both a possible resource and a hazard to drilling operations or hydrocarbon production. A local map of the permafrost zone is essential geotechnical information required prior to the construction of an offshore structure or pipeline.The MOSES method is particularly suitable for offshore electrical mapping as it can be made relatively insensitive to the shielding effects of the highly conductive sea water, in sharp contrast to many other electrical techniques. The transmitter is a vertical, long-wire bipole, extending from the sea surface to the sea floor. A commutated current is fed to two large electrodes: one near the sea surface and the other on the sea floor. The return current is through the sea water and the subjacent sediment. The receiver consists of two horizontal orthogonal coils located on the sea floor, and the data are measurements of two components of the magnetic field as a function of frequency and transmitter-receiver horizontal separation.The electrical conductivity of a sample of frozen material is much smaller than that of unfrozen or partially frozen sediment of the same type. Frozen and unfrozen thin layers are often observed sequentially throughout the geological section. The resistivity measured as a function of depth by an electrical logging tool is consequently highly variable. The resulting depth-averaged resistivity, the resistivity resolved by a surface electrical method, is macro-an-isotropic. An experimental design study reveals that both the vertical and horizontal averaged resistivities could be determined in a MOSES sounding without vertical scale distortion.A test of the methodology in very shallow water was conducted in the spring of 1986 at a site, approximate coordinates (70° N, 134.5° W), 85 km north-west of the town of Tuktoyaktuk. The instrumentation was lowered and subsequently recovered through holes in the ice which covers the Beaufort Sea at that time of the year. The transmitter power was obtained from a single lead-acid battery. Transmitter-receiver separations ranged from 10 to 300 m. A rapid increase in sediment resistivity with depth was observed. The higher resistivity values are consistent with those expected for a partially frozen zone.  相似文献   

Lines of OIV and SIV in the Goddard High-Resolution Spectrograph spectrum of RR Tel: constraints on atomic data     

G. M. Harper  C. Jordan  P. G. Judge  R. D. Robinson  K. G. Carpenter  T. Brage 《Monthly notices of the Royal Astronomical Society》1999,303(3):L41-L46

  相似文献   

Possible geothermal resources in the Coast Plutonic Complex of southern British Columbia,Canada     

T. J. Lewis  A. S. Judge  J. G. Souther 《Pure and Applied Geophysics》1978,117(1-2):172-179

In southern British Columbia the terrestrial heat flow is low (44 mW m^–2) to the west of the Coast Plutonic Complex (CPC), average in CPC (50–60 mW m^–2),and high to the east(80–90 mW m^–2). The average heat flow in CPC and the low heat generation (less than 1 W m^–3) indicate that a relatively large amount of heat flows upwards into the crust which is generally quite cool. Until two million years ago the Explorer plate underthrust this part of the American plate, carrying crustal material into the mantle. Melted crustal rocks have produced the inland Pemberton and Garibaldi volcanic belts in the CPC.Meager Mountain, a volcanic complex in the CPC 150 km north of Vancouver, is a possible geothermal energy resource. It is the product of intermittent activity over a period of 4 My, the most recent eruption being the Bridge River Ash 2440 y B.P. The original explosive eruption produced extensive fracturing in the granitic basement, and a basal explosion breccia from the surface of a cold brittle crust. This breccia may be a geothermal reservoir. Other volcanic complexes in the CPC have a similar potential for geothermal energy.Earth Physics Contribution No. 704.  相似文献   

Comparison of Calibration Techniques for Ground-Based C-Band Radiometers     

Tien  K.-J. C. De Roo  R. D. Judge  J. Pham  H. 《Geoscience and Remote Sensing Letters, IEEE》2007,4(1):83-87

We quantify the performance of three commonly used techniques to calibrate ground-based microwave radiometers for soil moisture studies, external (EC), tipping-curve (TC), and internal (IC). We describe two ground-based C-band radiometer systems with similar design and the calibration experiments conducted in Florida and Alaska using these two systems. We compare the consistency of the calibration curves during the experiments among the three techniques and evaluate our calibration by comparing the measured brightness temperatures (T_Bs) to those estimated from a lake emission model (LEM). The mean absolute difference among the T_Bs calibrated using the three techniques over the observed range of output voltages during the experiments was 1.14 K. Even though IC produced the most consistent calibration curves, the differences among the three calibration techniques were not significant. The mean absolute errors (MAEs) between the observed and LEM T_B s were about 2-4 K. As expected, the utility of TC at C-band was significantly reduced due to transparency of the atmosphere at these frequencies. Because IC was found to have a MAE of about 2 K that is suitable for soil moisture applications and was consistent during our experiments under different environmental conditions, it could augment less frequent calibrations obtained using the EC or TC techniques  相似文献   

Variability of Solar Five-Minute Oscillations in the Corona as Observed by the Extreme Ultraviolet Spectrophotometer (ESP) on the Solar Dynamics Observatory/Extreme Ultraviolet Variability Experiment (SDO/EVE)     

L. Didkovsky  A. Kosovichev  D. Judge  S. Wieman  T. Woods 《Solar physics》2013,287(1-2):171-184

Solar five-minute oscillations have been detected in the power spectra of two six-day time intervals from soft X-ray measurements of the Sun observed as a star using the Extreme Ultraviolet Spectrophotometer (ESP) onboard the Solar Dynamics Observatory (SDO)/Extreme Ultraviolet Variability Experiment (EVE). The frequencies of the largest amplitude peaks were found to match the known low-degree (?=0?–?3) modes of global acoustic oscillations within 3.7 μHz and can be explained by a leakage of the global modes into the corona. Due to the strong variability of the solar atmosphere between the photosphere and the corona, the frequencies and amplitudes of the coronal oscillations are likely to vary with time. We investigated the variations in the power spectra for individual days and their association with changes of solar activity, e.g. with the mean level of the EUV irradiance, and its short-term variations caused by evolving active regions. Our analysis of samples of one-day oscillation power spectra for a 49-day period of low and intermediate solar activity showed little correlation with the mean EUV irradiance and the short-term variability of the irradiance. We suggest that some other changes in the solar atmosphere, e.g., magnetic fields and/or inter-network configuration may affect the mode leakage to the corona.  相似文献