Geomagnetic pulsations

Conclusion In writing this review paper the author has been aware that although the present international classification on geomagnetic pulsations (see Table I) had been really useful for several years since the Berkeley Meeting, it seems unsuitable for the up-to-date pulsation study. This is mainly due to the fact that it depends only on the period and waveform of the pulsations. For example, (1) occurrence of PP type of Pc1 even in the international Pc3 range (Heacock, 1966), (2) PP and CE getting mixed in a common period band (cf. 2.7), (3) similar mixing tendency of Pc3 with Pc4 (cf. 3.3 or Figure 21), (4) subtypes of Pi pulsations having common period ranges but different source mechanisms, (5) existence of various types of pulsations which can be classified neither to Pc nor to Pi (cf. Section 6), and so on. Hence the author feels that a new pulsation classification based on physical image on the occurrence models is really needed now.According to the international definition which has a period range of pulsations from 0.2 (5 Hz) to 600 sec, a part of the following electromagnetic field fluctuations called ELF emissions and ELF whistlers should belong to geomagnetic pulsations. ELF emissions are at times observed near 4 Hz and 9 Hz. They are so termed because of the difference between these frequencies and the Schumann resonance frequencies of 8 and 14 Hz (Yanagihara and Shimizu, 1969; Polk, 1969). Another type, ELF whistlers, exhibit either rising, falling or fluctuating tones from about 2 Hz to probably a few tens of Hz (Duffus, Nasmyth et al., 1958; Yamashita, 1967; Glangeaud, 1967; Yanagihara and Shimizu, 1969). In this review paper, however, both ELF emissions and whistlers have not been reviewed, since most of these seem to be out of the international frequency range so far as present observational knowledge is concerned. Some of the Pc6 and Dp2, involved in the international period range of pulsations, have also not been commented on, but the reader is advised to refer to Herron (1967) and Nishida (1968), respectively, for more detail.It has been frequently pointed out in this paper that latitudinal dependence of pulsation amplitude is one of the most important clues for seeking the model of excitation and propagation of HM and EM waves, but that this dependence has not been precisely obtained so far owing to the difference in geomagnetic longitude of the pulsation stations (for example, see Figure 40). Cooperative observations based on standardized magnetometers are eagerly desired at stations which are densely arranged along the same magnetic meridian, even if the observation is temporal.As already reviewed, various conflicting models have been proposed for each type of pulsation. On the occurrence of pc's, for example, there are two main conflicting models. In the first model, Pc2, 3, and 4 (Troitskaya, 1967; Patel and Hastings, 1968; and others) or Pc3 and 4 (Radoski and Carovillano, 1966) are related to one and the same resonance system and the difference in the type of these pc's is attributed to an effect of geomagnetic activity on the size of this system. In the second model, Pc2, 3, 4 and 5 are related to three or four different resonant systems (Jacobs and Sinno, 1960b; Hirasawa and Nagata, 1966; Kato, Mori et al., 1968; and others). Most of the conflict among such models seems to be removable by combining more thorough theoretical studies and correct dynamic spectrum analyses of the data at the polar region, auroral zone, sub-auroral zone, and middle and low latitudes, for various geomagnetic disturbance conditions.     

An empirical model of the plasma environment around Mercury

Since the flyby observations by Mariner 10 in 1974 and 1975, Mercury has been one of the most interesting objects for space physics and planetary exploration. The MESSENGER and BepiColombo missions now plan to revisit this planet. In order to design plasma instruments for the BepiColombo mission, we have estimated electron and ion fluxes around Mercury with an empirical model, which has been developed for the Earth’s magnetotail. The solar wind data needed as input parameters are derived from Helios observations. The result shows that our predicted electron fluxes at aphelion agree well with the Mariner-10 data. It is also noted that ion instruments must cover a very wide dynamic range of proton fluxes. However, the applicability of the Earth’s magnetospheric model to Mercury is, in itself, an important issue for comparative magnetospheric studies.     

Mercury Ion Analyzer (MIA) onboard Mercury Magnetospheric Orbiter: MMO

The Mercury Magnetopsheric Orbiter (MMO) is one of the spacecraft of the BepiColombo mission; the mission is scheduled for launch in 2014 and plans to revisit Mercury with modern instrumentation. MMO is to elucidate the detailed plasma structure and dynamics around Mercury, one of the least-explored planets in our solar system. The Mercury Plasma Particle Experiment (MPPE) on board MMO is a comprehensive instrument package for plasma, high-energy particle, and energetic neutral particle atom measurements. The Mercury Ion Analyzer (MIA) is one of the plasma instruments of MPPE, and measures the three dimensional velocity distribution of low-energy ions (from 5 eV to 30 keV) by using a top-hat electrostatic analyzer for half a spin period (2 s). By combining both the mechanical and electrical sensitivity controls, MIA has a wide dynamic range of count rates for the proton flux expected around Mercury, which ranges from 10⁶ to 10¹² cm⁻² s⁻¹ str⁻¹ keV⁻¹, in the solar wind between 0.3 and 0.47 AU from the sun, and in both the hot and cold plasma sheet of Mercury’s magnetosphere. The geometrical factor of MIA is variable, ranging from 1.0 × 10⁻⁷ cm² str keV/keV for large fluxes of solar wind ions to 4.7 × 10⁻⁴ cm² str keV/keV for small fluxes of magnetospheric ions. The entrance grid used for the mechanical sensitivity control of incident ions also work to significantly reduce the contamination of solar UV radiation, whose intensity is about 10 times larger than that around Earth’s orbit.     

A series of small scientific satellite with flexible standard bus

Japan Aerospace Exploration Agency has a plan to develop the small satellite standard bus for various scientific missions and disaster monitoring missions. The satellite bus is a class of 250–400 kg mass with three-axis control capability of 0.02 accuracy. The science missions include X-ray astronomy missions, planetary telescope missions, and magnetosphere atmosphere missions. In order to adapt the wide range of mission requirements, the satellite bus has to be provided with flexibility. The concepts of modularization, reusability, and product line are applied to the standard bus system. This paper describes the characteristics of the small satellite standard bus which will be firstly launched in 2011.     

海南地区电离层不规则体纬向漂移速度的观测和研究

根据中国海南富克(19.3°N,109.1°E)三点GPS观测系统2007年3月至11月的观测数据,利用互相关方法分析了三站闪烁信号的时间延迟,得出了不规则体纬向漂移的基本特征.在中国海南地区,闪烁主要发生在春秋季节,夜间不规则体的纬向漂移速度以东向为主,大小在50～150 m/s之间;平均东向漂移速度随时间呈下降趋势.另外,在闪烁刚发生时,不规则体纬向速度起伏较大,这可能与不规则体的随机起伏以及等离子体泡产生时垂直速度较大有关.中国海南地区不规则体纬向漂移速度的这些基本特征与低纬其他地区的测量结果较为一致.     

Development of a plant growth unit for growing plants over a long-term life cycle under microgravity conditions.

To study the effect of the space environment on plant growth including the reproductive growth and genetic aberration for a long-term plant life cycle, we have initiated development of a new type of facility for growing plants under microgravity conditions. The facility is constructed with subsystems for controlling environmental elements. In this paper, the concept of the facility design is outlined. Subsystems controlling air temperature, humidity, CO2 concentration, light and air circulation around plants and delivering recycled water and nutrients to roots are the major concerns. Plant experiments for developing the facility and future plant experiments with the completed facility are also overviewed. We intend to install this facility in the Japan Experiment Facility (JEM) boarded on the International Space Station.     

Measurements of trace contaminants in closed-type plant cultivation chambers.

Trace contaminants generated in closed facilities can cause abnormal plant growth. We present measurement data of trace contaminants released from soils, plants, and construction materials. We mainly used two closed chambers, a Closed-type Plant and Mushroom Cultivation Chamber (PMCC) and Closed-type Plant Cultivation Equipment (CPCE). Although trace gas budgets from soils obtained in this experiment are only one example, the results indicate that the budgets of trace gases, as well as CO2 and O2, change greatly with the degree of soil maturation and are dependent on the kind of substances in the soil. Both in the PMCC and in the CPCE, trace gases such as dioctyl phthalate (DOP), dibutyl phthalate (DBP), toluene and xylene were detected. These gases seemed to be released from various materials used in the construction of these chambers. The degree of increase in these trace gas levels was dependent on the relationship between chamber capacity and plant quantity. Results of trace gas measurement in the PMCC, in which lettuce and shiitake mushroom were cultivated, showed that ethylene was released both from lettuce and from the mushroom culture bed. The release rates were about 90 ng bed-1 h-1 for the shiitake mushroom culture bed (volume is 1700 cm3) and 4.1 approximately 17.3 ng dm-2 h-1 (leaf area basis) for lettuce. Higher ethylene release rates per plant and per unit leaf area were observed in mature plants than in young plants.     

On the correlation of the solar wind observed at the L5 point and at the Earth

The L5 point is a promising location for forecasting co-rotating high-speed streams in the solar wind arriving at the Earth. We correlated the solar wind data obtained by the Nozomi spacecraft in interplanetary space and by the Advanced Composition Explorer (ACE) at the L1 point, and found that the correlation is significantly improved from that of the 27-day recurrence of ACE data. Based on the correlation between the two spacecraft observations, we estimated the correlation of the solar wind velocity between the L5 point and at the Earth, and found that the correlation coefficient was about 0.78 in late 1999, while that of the 27-day recurrence was 0.51. Eighty-eight percent of the velocity difference falls within 100 km/s between the L5 point and the Earth. This demonstrates the potential capability of solar wind monitoring at the L5 point to forecast the geomagnetic disturbances 4.5 days in advance.     

Sounding rocket experiment of bare electrodynamic tether system

An overview of a sounding rocket, S-520-25th, project on space tether technology experiment is presented. The project is prepared by an international research group consisting of Japanese, European, American, and Australian researchers. The sounding rocket will be assembled by the ISAS/JAXA and will be launched in the summer of 2009. The sounding rocket mission includes two engineering experiments and two scientific experiments. These experiments consist of the deployment of bare electrodynamic tape tether in space, a quick ignition test of hollow cathode system in space, the demonstration of bare electrodynamic tether system in space, and the test of the OML (orbital-motion-limit) current collection theory.