Ray tracing study of electromagnetic ion cyclotron (EMIC) waves is conducted based on a realistic plasma density model. The simulation result shows that EMIC waves propagate away from the equatorial source region to higher latitudes basically along geomagnetic field lines, and are reflected at the region where their frequency matches the local bi-ion frequency. H+ band suffers H+-He+ bi-ion frequency reflection at lower latitudes, whereas He+ band suffers He+-O+ bi-ion frequency reflection at higher latitudes. Moreover, the concentration of heavy ions slightly affects the bi-ion frequencies and then slightly determines the reflection location of ray paths of EMIC waves. The current results present the first detailed study on the propagation characteristics of EMIC waves associated with bi-ion frequencies.
<p>Based on data from the Van Allen Probes and ZH-1 satellites, relativistic electron enhancements in extremely low L-shell Regions (reaching L~3) were observed during major geomagnetic storm (minimum Dst`-190 nT). &#160;Contrary to what occurs in the outer belt, such an intense and deep electron penetration event is rare and more interesting. Strong whistler-mode (chorus and hiss) waves, with amplitudes 81-126 pT, were also observed in the extremely low L-shell simultaneously (reaching L~2.5) where the plasmapause was suppressed. The bounce-averaged diffusion coefficient calculations support that the chorus waves can play a significantly important role in diffusing and accelerating the 1-3 MeV electrons even in such low L-shells during storms. This is the first time that the electron acceleration induced by chorus waves in the extremely low L-shell region is reported. This new finding will help to deeply understand the electron acceleration process in radiation belt physics.</p>
This report presents a set of results for different microbenchmarks and applications on the Intel
Xeon Platinum8160 Processor, formerly known as Skylake. For simplicity, we will use both Skylake
and SKX to refer to this processor. We use the Skylake nodes that will be available in Stampede2.
This systemwill provide Intel Knights Landing and Skylake chips interconnected by a 100 Gb/sec
Intel Omni-Path (OPA) network with a fat tree topology. The peak performance of the system will
be 18 PF.
Abstract Based on observations from the Parker Solar Probe in the near-Sun solar wind, this study identifies an ion-scale wave event characterized by two distinct frequency bands. The lower-band waves exhibit right-hand polarization, while the upper-band waves have left-hand polarization. Alongside these waves, there are clear indications of the existence of both proton core and beam components, with the perpendicular temperature being higher than the parallel temperature in the measured proton velocity distribution functions (VDFs). Utilizing the plasma parameters derived from typical proton VDFs, instability analyses are conducted to investigate the mode nature of the observed waves and their excitation mechanism. The lower-band waves are identified as sunward ion cyclotron waves (ICWs), generated through the proton beam cyclotron instability; the upper-band waves are recognized as antisunward ICWs, induced by the proton core cyclotron instability. This study provides the first direct observational evidence confirming the presence of counterpropagating ICWs and proton cyclotron instability in the solar wind.
Scientists and engineers using supercomputer clusters should be able to focus on their scientific and technical work instead of worrying about operating their user environment. However, creating a convenient and effective user environment on modern supercomputers becomes more and more challenging due to the complexity of these large-scale systems. In this report, we discuss important design issues and goals in user environment that must support multiple compiler suites, various applications, and diverse libraries on heterogeneous computing architectures. We present our implementation on the latest high-performance computing system, Yellowstone, which is a powerful dedicated resource for earth system science deployed by the National Center for Atmospheric Research. Our newly designed user environment is built upon a hierarchical module structure, customized wrapper scripts, pre-defined system modules, Lmod modules implementation, and several creative tools. The resulting implementation realizes many great features including streamlined control, versioning, user customization, automated documentation, etc., and accommodates both novice and experienced users. The design and implementation also minimize the effort of the administrator and support team in managing users environment. The smooth application and positive feedback from our users demonstrate that our design and implementation on the Yellowstone system have been well accepted and have facilitated thousands of users all over the world.
The NCAR-Wyoming Supercomputing Center (NWSC) will begin operating in June 2012, and will house NCAR's next generation HPC system. The NWSC will support a broad spectrum of Earth Science research drawn from a user community with diverse requirements for computing, storage, and data analysis resources. To ensure that the NWSC satisfies the needs of this community, the procurement benchmarking process was driven by science requirements from the start. We will discuss the science objectives for NWSC, translating scientific goals into technical requirements for a machine, and assembling a benchmark suite from community science models and synthetic tests to measure the technical capabilities of the proposed HPC systems. We will also talk about the benchmark analysis process, extending the benchmark suite as a testing tool over the life of the machine, and the applicability of the NWSC benchmarking suite to other HPC centers.
Plasma density is an important factor in determining wave-particle interactions in the magnetosphere. We develop a machine-learning-based electron density (MLED) model in the inner magnetosphere using electron density data from Van Allen Probes between September 25, 2012 and August 30, 2019. This MLED model is a physics-based nonlinear network that employs fundamental physical principles to describe variations of electron density. It predicts the plasmapause location under different geomagnetic conditions, and models separately the electron densities of the plasmasphere and of the trough. We train the model using gradient descent and backpropagation algorithms, which are widely used to deal effectively with nonlinear relationships among physical quantities in space plasma environments. The model gives explicit expressions with few parameters and describes the associations of electron density with geomagnetic activity, solar cycle, and seasonal effects. Under various geomagnetic conditions, the electron densities calculated by this model agree well with empirical observations and provide a good description of plasmapause movement. This MLED model, which can be easily incorporated into previously developed radiation belt models, promises to be very helpful in modeling and improving forecasting of radiation belt electron dynamics.
The scale of scientific data generated by experimental facilities and simulations on high-performance computing facilities has been growing rapidly. In many cases, this data needs to be transferred rapidly and reliably to remote facilities for storage, analysis, sharing etc. At the same time, users want to verify the integrity of the data by doing a checksum after the data has been written to disk at the destination, to ensure the file has not been corrupted, for example due to network or storage data corruption, software bugs or human error. This end-to-end integrity verification creates additional overhead (extra disk I/O and more computation) and increases the overall data transfer time. In this paper, we evaluate strategies to maximize the overlap between data transfer and checksum computation. More specifically, we evaluate file-level and block-level (with various block sizes) pipelining to overlap data transfer and checksum computation. We evaluate these pipelining approaches in the context of GridFTP, a widely used protocol for science data transfers. We conducted both theoretical analysis and real experiments to evaluate our methods. The results show that block-level pipelining is an effective method in maximizing the overlap between data transfer and checksum computation and can improve the overall data transfer time with end-to-end integrity verification by up to 70% compared to the sequential execution of transfer and checksum, and by up to 60% compared to file-level pipelining.
To clarify the allometric growth pattern and hunger tolerance of Hemibarbus maculatus Bleeker larvae, the morphological lengths of their functional organs were measured continuously and their primary feeding rates under a state of starvation were studied. A control group and starvation group were set up for this study, and 10 larvae were sampled from each group every day in order to study their allometric growth pattern and starvation tolerance. The results indicated that the Hemibarbus maculatus larvae opened their mouths for feeding at 4 days after hatching, and that the yolk sac disappeared completely at 11 days after hatching. The Hemibarbus maculatus larvae preferentially developed their heads, fins, and eyes, related to the functions of feeding, balancing, and swimming, in order to cope with complex environments. The growth inflection points for the head length, pectoral fin length, dorsal fin length, eye diameter, eye spacing, snout length, and body height were characterized by total lengths of 10.93 mm, 11.67 mm, 11.67 mm, 13.17 mm, 16.53 mm, 15.13 mm, and 15.13 mm, respectively. Prior to and following the inflection point, positive allometric growth was observed in all organs. After the inflection point, the dorsal fin continued to maintain positive allometric growth, while the others changed to isometric allometric growth. A growth inflection point was not observed for trunk length or the lengths of the tail and anal fins. The trunk length always maintained negative allometry, while the tail and anal fin lengths were reversed. The growth inflection point of the tail length was at a total length of 13.68 mm. Before and after the growth inflection point, negative and isometric allometric growths were observed, respectively. According to the relationship between the total length and number of days after hatching, the growth inflection point of the Hemibarbus maculatus larvae was concentrated at TL = 10.93–16.53 mm, which was observed 14–20 days after hatching. The point of no return for the Hemibarbus maculatus larvae was 12–13 days after hatching, and the ratio of days after hatching in the mixed trophic period to the endotrophic period was 1.75, indicating that the larvae had strong hunger tolerance. Therefore, when considering a water temperature of 22.66 ± 1.56 °C, 4–5 days after hatching is the best time to cultivate in the pond, and it should not be carried out later than 12 days after hatching.
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