Ken T. Murata

Development and Application of Geospace Environment Simulator for the Analysis of Spacecraft–Plasma Interactions

Space development has been rapidly increasing, and a strong demand should arise regarding the understanding of the spacecraft-plasma interactions, which is one of the very important issues associated with the human activities in space. To evaluate the spacecraft-plasma interactions including plasma kinetics, transient process, and electromagnetic field variation, the authors have started to develop a numerical plasma chamber called Geospace Environment Simulator (GES) by making the most use of the conventional full particle-in-cell plasma simulations. For the development of a proto model of GES, the authors have used the Earth Simulator, which is one of the fastest supercomputers in the world. GES can be regarded as a numerical chamber in which space experiments can be virtually performed and temporal and spatial evolutions of spacecraft-plasma interactions can be analyzed. In this paper, the authors have briefly introduced GES in terms of its concept, modeling, and research targets. As one of the research topics of GES, the authors have investigated the impedance variation of electric field antenna onboard scientific satellites in the photoelectron environment in space. From the preliminary simulation results, the large change of reactance of the antenna impedance below the characteristic frequency corresponding to the local plasma frequency determined by the photoelectron density could be confirmed

Global MHD modeling of ionospheric convection and field‐aligned currents associated with IMF By triggered theta auroras

Using numerical magnetohydrodynamic simulations, we investigate the evolution of ionospheric convection and field-aligned currents (FACs) when θ auroras are formed in response to interplanetary magnetic field (IMF) By transitions. When the polarity of IMF By switches abruptly during northward IMF periods, the crossbar of the θ aurora is isolated from the flankside auroral oval and drifts into the polar cap. This drift motion is involved in a large round cell associated with new IMF By, with sunward convection residing only on the dayside tip of the crossbar. There exists an IMF By-controlled large-scale FAC system on the crossbar. When the θ aurora is drifting duskward (dawnward), the FACs are located on the dawnside (duskside) boundary of the crossbar adjacent to the “new” lobe. In contrast, the magnetospheric source region of the crossbar FAC system is located on the duskside (dawnside) boundary of the protruded plasma sheet adjacent to the “old” lobe. In the source region, plasma thermal pressure feeds the electromagnetic energy of FACs, and these processes can be interpreted as coupling of slow mode and Alfven mode disturbances. In the ionosphere, the crossbar-associated FACs close with part of the region 1 currents associated with the new crescent cell. The magnetospheric source of that part of the region 1 FACs is located on the plasma sheet boundary and the magnetopause both adjacent to the new lobe. Dynamo processes in the old-lobe side and the new-lobe side work together to drive the ionospheric drift motion of the crossbar.

Pi2 pulsation simultaneously observed in the E and F region ionosphere with the SuperDARN Hokkaido radar

We investigated Pi2 pulsations in the nightside ionosphere that began at 14:15 UT (2315 LT) on 11 July 2010, and they were observed with high-temporal (8 s) resolution by beam 4 of the Super Dual Auroral Radar Network (SuperDARN) Hokkaido radar. These pulsations were simultaneously observed in both the ground/sea scatter echoes reflected from the F region height and in ionospheric echoes from field-aligned irregularities in the sporadic Es region. They had the same period of 110 s and approximately no phase lag. From the radar observations and the International Geomagnetic Reference Field model, the amplitude of the eastward (EEW) component of the electric field of the Pi2 pulsations in the ionosphere was estimated ~8.0 mV/m in the F region and ~2.0 mV/m in the E region. Corresponding Pi2 pulsations appeared dominantly in the horizontal northward magnetic field component (H) at nearby ground stations, Moshiri (MSR), St. Paratunka (PTK), and Stecolny (STC), with amplitudes ranging from 6 nT (MSR) to 10 nT (STC). At the dominant frequency of 8.8 mHz, the coherences between H and EEW were high (>0.9), the cross phases of EEW relative to H were −56° and −45°, and the amplitude ratios were 2.7 × 105 m/s and 8.4 × 105 m/s, in the E and F regions, respectively. Based on a comparison of these results with theoretical predictions, we suggest that the concept of a pure cavity mode is not sufficient to explain the combined observations for midlatitude Pi2 waves and that the contribution of an Alfven waves must be taken in account.

A quality measurement tool for high-speed data transfer in long fat networks

Due to rapid increase of network bandwidth, applications and systems working in long fat network (LFN) play more important roles. For effective development of them, precise measurements of network conditions are significant. Transmission Control Protocol (TCP) is the most commonly used protocol, but is essentially unable to achieve high throughput in LFNs with packet losses. For this reason, it is hard for conventional network measurement tools to show the maximum or available bandwidth in LFN, especially in high packet loss environments. To overcome this issue, we introduce a novel data transfer protocol on TCP/IP transport layer, namely high-performance and flexible protocol (HpFP). For high-precision pace control and retransmission control, the HpFP intermittently monitors network conditions such as packet loss and latency. We develop an application via the HpFP, named hperf, which measures end-to-end throughput as well as status of packet loss and latency in LFNs. We carry out experiments to examine the abilities of the hperf in high-throughput data transfer and measurement of network qualities in terms of packet loss and latency. The hperf achieves almost wire-rate throughput, 10 Gbps, on the international link between Japan and the USA with even 0.5% packet loss ratio (PLR). The measurements of packet loss and latency show good correspondence with the conventional methods via iperf and ping. These results are verified in our laboratory experiments on 10 Gbps link using a network simulator as well. We conclude that the HpFP has significant potential for a variety of network applications and the hperf is a good network quality measurement tool in LFNs, compared to the conventional TCPs.

Improvement of real-time transfer of phased array weather radar data on long-distance networks

With the tremendous development of remote sensing technologies, large-scale data sets are collected from environmental and meteorological sensors. Edge computing for large-scale data sets is hard to be conducted in real time on the sensors, thus data transfer to cloud system and data processing play an important role. One of the barriers in such system is high-speed data transfer on long-distance networks. Even low packet loss condition leads to decrease in throughput by conventional transmission control protocol (TCP)-based tools. In this paper, we overcome this issue by proposing a high-performance data transfer tool to improve real-time data processing of phased array weather radar on long-distance networks. The proposed tool, called high-performance copy (hcp), is designed based on an open source tool for file copy operations and implemented using our socket library specialized for long-distance networks. We evaluate our tool with simulations and real data transfer scenarios. The results show that the hcp enables concurrent data transfer from radar sites to cloud system (data processing site) in real time. The throughput of data transfer from a radar site to a data processing site increases from 40 Mbps using the conventional TCP-based tool to 489.2 Mbps using the hcp.

Operation of a Data Acquisition, Transfer, and Storage System for the Global Space-Weather Observation Network

A system to optimize the management of global space-weather observation networks has been developed by the National Institute of Information and Communications Technology (NICT). Named the WONM (Wide-area Observation Network Monitoring) system, it enables data acquisition, transfer, and storage through connection to the NICT Science Cloud, and has been supplied to observatories for supporting space-weather forecast and research. This system provides us with easier management of data collection than our previously employed systems by means of autonomous system recovery, periodical state monitoring, and dynamic warning procedures. Operation of the WONM system is introduced in this report.

A bandwidth challenge at Super Computing (SC) Conference: Large-scale data transfer using 10Gbps network

Results of bandwidth challenge contest at Super Computing (SC) 2007 by NICT are discussed. The target of this contest is to make full use of 10 Gbps network for any scientific applications. We, NICT team, attempted to transfer large-scale numerical data at NICT (in Japan) to SC 2007 venue in Reno, USA. We optimized our data transfer system for the real-time computer simulation data, and finally obtained through-put from Japan to USA as high as 4 Gbps.

A web-based real-time and full-resolution data visualization for Himawari-8 satellite sensed images

It has been almost four decades since the first launch of geostationary meteorological satellite by Japan Meteorological Agency (JMA). The specifications of the geostationary meteorological satellites have shown tremendous progresses along with the generations, which are now entering their third generation. The third-generation geostationary meteorological satellites not only yield basic data for weather monitoring, but also globally observe the Earth’s environment. The development of multi-band imagers with improved spatial resolution onboard the third-generation geostationary meteorological satellites brings us meteorological data in larger size than those of the second-generation ones. Thus, new techniques for domestic and world-wide dissemination of the observational big data are needed. In this paper, we develop a web-based data visualization for Himawari-8 satellite sensed images in real time and with full resolution. This data visualization is supported by the ecosystems, which uses a tiled pyramid representation and parallel processing technique for terrain on an academic cloud system. We evaluate the performance of our techniques for domestic and international users on laboratory experiments. The results show that our data visualization is suitable for practical use on a temporal preview of observation image data for the domestic users.

Real-time 3D visualization of phased array weather radar data via concurrent processing in Science Cloud

With the tremendous development of remote sensing technologies, a large amount of observation data are generated from sensors. Since each sensor generates data periodically, e.g., every minute, a concurrent data processing using a cloud system plays an important role in the modern design process. This paper focuses on concurrent data processing techniques for an X-band phased array weather radar (PAWR) using high-speed network, parallel data processing system, and large-scale storage system. The PAWR at National Institute of Information and Communications Technology (NICT), Japan rotates in 30 sec to capture a 3D structure of rainfalls within 60 km in radius and 15 km in altitude. In this paper, we develop a real-time 3D visualization system of the observation data of the PAWR. Our visualization is carried out from 54 sec to 69 sec (depending on the weather conditions) after every observation period, which is in the same time scale with other conventional 2D visualization of X-band weather radars. In addition, we discuss a combination of cloud ecosystems for the concurrent processing at low cost. The methodology is considered as a pioneering case study to develop of a variety of real-time data processing systems of big data via remote sensing.

An application of novel communications protocol to high throughput satellites

For network communications using modern high throughput satellite (HTS) on geostationary orbits, network throughput of transmission control protocol (TCP), one of the most popular protocols, is limited due to the packet loss on the satellite link. The packet loss is mainly caused by the attenuation of signals in severe weather conditions like heavy rain. It is high time to develop novel network communication techniques on the transport layer in TCP/IP designed for the systems and applications in broadband communications. In this paper, we introduce a high-speed data transfer protocol, named high-performance and flexible protocol (HpFP), to achieve high throughput for the HTS even with packet loss. The HpFP, in comparison with TCP-Hybla and UDP-based data transfer (UDT) protocols, is evaluated on a laboratory experiment simulating a geostationary orbit satellite link of 10 Gbps. It is clarified that the HpFP outperforms both the TCP-Hybla and the UDT showing high throughputs (close to 10 Gbps) when the packet loss ratio (PLR) is 1%, and remains more than 1 Gbps under even 10% PLR condition. Moreover, in case of no packet loss, the HpFP exhibits a quick start-up time (6 sec) at the initial phase to achieve 10 Gbps, while the TCP-Hybla and the UDT take 9 sec and 16 sec to their maximum throughputs, respectively.