Search

A new optical instrument, the Fabry-Perot Doppler imaging system (FPDIS), has been developed for observations of two-dimensional distributions of thermospheric wind velocities and temperatures by the measurement of the Doppler shift and width of the aurora or of the airglow emission lines of atomic oxygen OI 557.7 nm and OI 630.0 nm over a wide field of view (165°). A technique for the derivation of Doppler temperatures and wind velocities was developed by use of a truncated Fourier series. Thermospheric wind velocities and temperatures have been obtained with unprecedented high temporal (1 min) and spatial (24 points for an all-sky image) resolutions. Errors in the derived wind velocities and temperatures are estimated to be less than 25 m/s and 100 K, respectively, for inner-fringe positions and 35 m/s and 170 K for outer-fringe positions, respectively. This system was applied to observations of thermospheric wind velocities and temperatures at Syowa Station (69.00° S, 39.58° E), Antarctica for the period of one austral winter in 1990.

Magnetic field and particle data obtained from the Akebono satellite in the period from December 1989 to February 1990 are used for examining the relationships between electron populations and field-aligned currents in the poleward boundary region of the nightside auroral oval. It is found that suprathermal electron beams frequently observed at the poleward boundary of the auroral oval associated with a latitudinally narrow (∼ 1°) field-aligned current system located at the poleward edge, which has been designated as “the boundary current system” by Fukunishi et al. (1993, p. 11,250). In addition, an unstructured band of plasma-sheet-like electrons with isotropic pitch angle distributions except for loss cone appears through the auroral oval including the boundary current region. As a result, the electron energy spectra at the poleward boundary are characterized by a superposition of two Maxwellian functions: the isotropic high-temperature component and the field-aligned low-temperature component. From the Maxwellian fitting procedure, the temperature and the density of the high-temperature component are estimated to be 0.3 - 1.7 keV and ≤ 1.0 cm−3, respectively, and those of the low-temperature component are estimated to be 10 - 80 eV and 2 - 16 cm−3, respectively. An important finding is that the temperature and the density of the low-temperature component and the density of the high-temperature component are significantly enhanced in the upward current region occupying the equatorward portion of the boundary current system, while the temperature of the high-temperature component is nearly constant throughout this region. These characteristics strongly suggest that the high-temperature component originates from plasma sheet electrons, while the low-temperature component originates from ionospheric electrons. It is likely that ionospheric thermal electrons flow away from the polewardmost downward current region into the magnetosphere and are accelerated and heated by some wave-particle interaction process during their inward motion due to E × B drift.

Accepted: 1992-07-24, 資料番号: SA1001659000

Using the magnetic field and low-energy particle data from the Akebono (EXOS D) satellite, the latitudinal structures of field-aligned currents and auroral particles in the nightside auroral oval region have been studied in detail for 12 northern hemisphere passes in the 20-04 MLT sector and at altitudes of 5000-10,000 km. It is found that the nightside field-aligned current system consists of the latitudinally narrow (∼1°) current system located at the poleward boundary of the auroral oval and the latitudinally wide current system which occupies the main portion of the oval. The former has been designated as “the boundary current system” and the latter as “the central current system.” Both current systems are suggested to be located in the closed field line region, since the polar rain is observed just poleward of the boundary current system. The boundary current system is suggested to be independent of the traditional region 1 current system associated with inverted V electron precipitation, since suprathermal electrons with field-aligned pitch angle distributions are found to be the main charge carrier of this current system. Another important finding is that energy-dispersed ion precipitation events, which are interpreted to be the result of the E × B drift of ions flowing earthward in the plasma sheet boundary layer, appear in this boundary current region. The central current system consists of the two regions, the inverted V electron precipitation region on the poleward side and the unstructured electron and ion precipitation region on the equatorward side. It is suggested therefore that this central current system corresponds to the traditional region 1 and region 2 current system in the nightside sector. It is further found that the diffuse band of plasma sheet kilovolt electrons is continuously observed form the polar cap boundary defined as the polar rain terminator to the equatorward boundary of the unstructured precipitation region through the inverted V electron precipitation region. Consequently, inverted V structures and diffuse plasma sheet electron precipitation always coexist. From these spatial relationships, it is strongly suggested that the boundary current system is mapped to the plasma sheet boundary layer, while the central current system is mapped to the main or central plasma sheet.

Accepted: 1992-05-13, 資料番号: SA1001252000

Accepted: 1992-01-10, 資料番号: SA1001251000

Magnetosphere-ionosphere coupling processes in inverted-V electron precipitation regions have been investigated using particle and magnetic field data obtained from two antarctic sounding rockets S-310JA-11, and S-310JA-12, launched into quiet and active auroral arcs, respectively. These data have suggested the presence of a linear relation between field-aligned current and field-aligned potential difference, i.e., j∥ = KV∥, given by Fridman and Lemaire [1980] and Lyons [1980]. The density n and thermal energy E0 of primary electrons have been obtained by fitting accelerated Maxwellian distribution functions to the observed electron energy spectra. It is found that the thermal energy E0 is larger inside the arcs than outside the arcs for both the quiet and active arcs observed, suggesting that precipitating electrons are heated during the field-aligned acceleration. In contrast, the electron density n is enhanced outside the arcs for the quiet arc event, while it is enhanced inside the arcs for the active arc event. From an investigation of the relation between E0 and V∥ and also the relation between E0 and j∥, it is suggested that the heating occurs effectively when the current intensity exceeds a certain threshold and that the electron heating rate is 5–40% of the energy gain due to the field-aligned acceleration. Assuming that, this heating is due to Joule heating through anomalous resistivity, it is also suggested that the total anomalous resistivity along the magnetic field line decreases with an increase of K.

In order to clarify characteristics of geomagnetic sudden commencements (SC's) at geomagnetically conjugate stations, six SC events were analyzed by the use of digital magnetic data at Syowa Station in Antarctica and Husafell, Isafjordur and Tjornes in Iceland during the interval from September 1984 to January 1985. SC polarization, waveforms and SC-associated pulsations are examined between the conjugate stations, and the characteristics are discussed in comparison with a model (H. NAGANO et al. : Mem. Natl Inst. Polar Res., Spec. Issue, 36,123,1985) suggested for the latitudinal reversal of SC polarization in high latitudes on the ground.

Local time dependence of polarization of geomagnetic sudden commencements (SC's) at geostationary orbit was statistically analyzed, using magnetic data from GOES 2 and 3 satellites for the interval from August 1978 to August 1980. The polarization in the plane perpendicular to the geomagnetic field is counterclockwise in the morning side and clockwise in the afternoon side, when viewed along the field direction. The demarcation line across which the polarization is reversed seems to be located between 11h and 14h LT. This time span may be due to different angles at which shock fronts or discontinuities propagating in interplanetary space collide against the magnetosphere. The latitudinal reversal of polarization of SC observed in high latitudes on the ground does not seem to occur at geostationary orbit.

A rocket containing a triaxial fluxgate magnetometer was launched from Syowa Station, Antarctica, at 1935 UT on July 12,1985. Magnetic anomalous field was measured with high sampling time of every 10ms. The vector magnetometer indicated an existence of field-aligned currents in the vicinity of an auroral arc and electrojet currents at the ionospheric level.

1976年南極昭和基地において,ISIS1,2人工衛星からのVLF観測テータの受信が行われた.これらのVLFエミッションのテータと地上で同時刻に観測されたVLFエミッションおよひオーロラの観測テータとの比較を行った.一般に,ISIS 2が高緯度領域から低緯度領域に移動していくにつれ,ヒスエミッションとソーサーエミッションが順々に観測される.解析結果によると,ヒスエミッション領域からソーサーエミッション領域に移る境界付近か,地上て見られるもっとも低緯度側のオーロラ・アークを通る磁力線の位置に対応していることが明らかになった.地上て観測されたヒスエミッションのスペクトラムと人工衛星て受信されたヒスエミッションのスペクトラムを比較した結果,地上と人工衛星とを磁力線て結んた領域て観測されるヒススペクトラムは似ておらす,むしろ,人工衛星のサフサテライトポイントが,昭和基地と同じ地磁気緯度付近にある時に観測されるヒススペクトラムが互に類似していることがわかった.このことはヒスエミッションが,人工衛星の高度(h=1400 km)から地上まで磁力線に沿って伝搬していないことを示している.Ray pathの計算を行った結果,地上て受信されるヒスエミッションは,人工衛星の高度からノンダクトな伝搬路をとることが推定された., ISIS VLF data were received at Syowa Station, Antarctica in 1976. These data were compared with VLF and auroral data simultaneously observed on the around. In general, hiss and saucer emissions were succesively observed on ISIS 2, when ISIS 2 moved from the polar cap towards the low latitude. It is found that the geomagnetic field lines through a northernmost auroral arc are located between the occurrence regions of hiss and saucer emissions. It is also found that spectra of hiss emissions observed on the ground (Syowa) are not similar to those of VLF emissions observed in the region connected with field line at the satel-lite altitude, but are similar to those of VLF emissions observed near the same geomagnetlc latitude as that of Syowa Station. The result suggests that auroral hiss emissions do not propagate along the geomagnetic field lines from the statellite height (～1400 km) to the ground. The calculation by means of the ray theory suggests that hiss emissions propagate along a non-ducted path from the satellite height to the ground

Experimental results obtained by the sounding rockets at Syowa Station, Antarctica, are briefly summarized. The electron density profiles in auroras were measured by the rockets which penetrated into intensely bright (∿30kR for OI 5577 Å), bright (∿10kR) and weak (∿5kR) auroras. The E-region electron density amounts to ∿1.2×(10)^6 el/(cm)^3,∿5.0×(10)^5 el/(cm)^3 and ∿6.0×(10)^4el/(cm)^3 for intensely bright, bright and weak auroras respectively, while it is ∿6.0×(10)^3el/(cm)^3 for no aurora during the night. The electron density in the D-region beneath the lower boundary of an intensely bright arc (75-98 m in altitude) is also considerably enhanced, up to 0.7-1.0×(10)^6 el/(cm)^3. In bright auroral arcs, the electric field becomes small and points in the equatorward direction, whereas it becomes large with the predominant westward direction in the near space outside of a bright auroral arc. The electric field fluctuations (up to 240Hz in frequency) are greatly enhanced in auroras over a wide frequency range, at altitudes of 100-120km. Various kinds of VLF and HF emissions are observed in the auroral ionosphere. Characteristics of these emissions and their relations to the precipitating electron flux are discussed.

Conjugate observation of VLF emission was carried out at Kitdalen (69.1°N, 20.3°E geographic, 65.5°N, 105.3°E geomagnetic, L=6.0) in Norway and at Syowa Station (69.0°S, 39.6°E geographic, 66.2°S, 70.5°E geomagnetic, L=6.1) in Antarctica in February 1980,and also at Andφya (69.2°N, 16.0°E geographic, 66.0°N, 102.2°E geomagnetic, L=6.1) in Norway and at Syowa in March 1982. During these campaign periods, periodic VLF emissions were often observed at both stations in opposite hemispheres. A typical periodic emission event observed at both stations was chosen for cross spectral analysis of the emission period. The results show the characteristics of "symmetrical three-phase emission" reported by BRICE (Radio Sci., 69D, 257,1965) as three wave packets, which were symmetrically spaced along the line of force, were echoing in the magnetosphere. Though the geomagnetically conjugate point of Syowa is located about 1800km far from Kitdalen or Andφya, the common nature of the emissions observed at both stations suggests that the periodic emission which originates from the common source in the magnetosphere can spread more than 1800km at the ionospheric level. This observational result is compared with the ray tracing calculation. It is concluded that if the periodic emissions are guided by a field-aligned duct and the duct is terminated at an altitude of 6000km, the periodic emissions can spread as far as the observed distance.

The coordinated observations of the Antarctic middle atmosphere were conducted by the wintering parties of the 23rd-26th Japanese Antarctic Research Expeditions at Syowa Station (69.0°S, 36.6°E) during 1982-1985 in cooperation with the Middle Atmosphere Program (MAP). The wintering party of JARE-26 carried out the final campaign for the MAP at Syowa Station. The middle atmosphere was observed with a combination of remote-sensing techniques from the ground and spacecraft and in-situ measurements on balloons and sounding rockets. The major ground-based remote-sensing facilities were a Dobson spectrophotometer for ozone measurement, a ruby lidar for stratospheric aerosol measurement and a dye lidar for sodium layer measurement, a VHF doppler radar for measuring motions of ionized and neutral atmospheres and a multi-beam riometer for monitoring particle precipitation. The meteorological rockets launched at 2-hour intervals succeeded in detecting internal gravity waves at the 20-70km altitude range. This paper gives an outline of the MAP campaign in 1985.

The recent study of a storm time Pc 5 plasma wave event by Lanzerotti, Fukunishi, Lin, and Cahill is extended by the analysis of recently available high-latitude ground-based magnetometer data and hot plasma particle (∼1–40 keV) distribution data from a satellite in the magnetosphere. These additional data suggest that an odd mode shear Alfven wave (period ∼7 min) was excited by a high β drift instability at a high-altitude gradient region of the hot plasma distribution. The region of occurrence of the instability was characterized by a cold plasma density of ∼100 cm−3.

Dynamic spectral characteristics of magnetic pulsations in the frequency range from Pc3 to Pc5 are examined on the basis of the magnetic field data observed at the synchronous orbit, ATS 6 and at the high latitude ground stations, Syowa (L∿6) and Mizuho (L∿7) in Antarctica, and Husafell (a conjugate station to Syowa) in Iceland. The dynamic spectral power seen at both locations shows generally a similar frequency structure throughout the daylight hours. It contains several dominant frequency trends consisted of a harmonic relation with one another. The satellite location with respect to the magnetic latitude along the field line is very sensitive to the spectral structures seen in the dynamic spectra. When the satellite was located 10°above the magnetic equator, the spectra appeared with two dominant spectral trends. One of them was the lowest frequency trend corresponding to the Pc 4-5 frequency range (3-10mHz) and another trend was seen in the Pc3 frequency range (20-80mHz). They exhibited a harmonic relation with each other. When the satellite was located near the magnetic equator, the lowest frequency trend did not appear and its second harmonics became visible. In the dynamic spectra of the ground station, the spectral trends in the Pc3 and Pc4-5 are also in a harmonic relation with each other, seen similarly at the satellite location only except for many dotted structures with an interval of a few tens of minutes.

SSC events at the geosynchronous altitude have been studied using the data obtained at the geosynchronous satellite, SMS/GOES, as well as the data obtained on the ground for the period from 1976 to 1980. In the compressional component (parallel to the ambient magnetic field direction), the SSC amplitude is very large in the noonside, while it becomes smaller with increasing distance from the noonside and is very small or none in the midnightside. In the transverse component (east-west direction), the direction of the initial movement of Psc changes drastically across the noon and the midnight. The direction is eastward in the morningside, while it is westward in the eveningside. These observational results will be examined quantitatively in the present study.

Main purposes of this study are to clarify source region and generation mechanism of periodic emissions by means of comparison of characteristics of the emissions observed at high and low latitudes. In the present paper, long-term variations of the occurrence at Syowa Station and Memambetsu during five years from 1976 to 1980 are investigated statistically. It is an important result obtained from the investigation that the variation has a clear reverse relation to that of the relative sunspot number, that is, the occurrence decreases with increase of the solar activity. More intense attenuation of the emissions in the ionospheric duct in such active years will be regarded as the main cause of the decrease. Because of inward shift of the plasmapause, the wave-particle interaction caused by ring-current protons will also hardly occur statistically in the active years. In other words, the long-term variation can also be explained well by the mechanisms of generation and propagation of the emissions proposed already by the same authors. As an only event in 1980,periodic emissions with unusual low frequency were observed successively at Memambetsu throughout the day of December 20. As the frequency seems to be fairly lower than the cutoff frequency of the ionospheric duct, the emissions will be unable to propagate through the duct. Therefore, the source latitudes will be located near Memambetsu. The generation may be related to another exciting mechanism such as helium cyclotron resonance.

Lidar measurements of the mesospheric sodium layer were made on 42 nights from April to October in 1985 during the wintering period of the 26th Japanese Antarctic Research Expedition (JARE-26) at Syowa Station, Antarctica (69°00'S, 39°35'E). This work was carried out as a part of the Middle Atmosphere Program (MAP). There were no significant seasonal variations in sodium abundance. Especially, the enhancement of abundance in winter was not observed. These results differ from those obtained at midlatitudes in the northern hemisphere. However, it is interesting that the sodium abundance oscillated with a period of about 36 days. As for the nocturnal variations of the sodium layer, the semidiurnal oscillation in the abundance was not detectable, but the wavelike structure due to gravity wave activity was frequently observed in the sodium vertical profile. Moreover, it was found that the sodium layer was perturbed during an auroral breakup event.

The S-310JA-12 rocket was launched geomagnetically northward from Syowa Station, Antarctica, during a strong substorm period. The onboard instruments were a Faraday cup for measuring electron density and its fluctuations up to 8kHz together with total flux of electrons with energies above 105eV and a pair of double probes for measuring DC electric field and electric field fluctuations of 5-220Hz, which detected various kinds of ELF-VLF band fluctuations during the flight. During the ascent, the Faraday cup observed strong VLF fluctuations in the E region and burst-like fluctuations over the region from 140 to 200km in altitude. The former might be caused by the two-stream instability and/or the cross-field instability, while the latter is considered to be generated artifitially around the rocket. Around the height of 220km, quasi-sinusoidal waves with the frequency of about 150Hz were observed by the both instruments. They are found to be right-hand circularly or elliptically polarized waves by crosscorrelation analysis. During the descent, the rocket passed through highly active auroras and the both instruments observed strong ELF fluctuations. It is suggested by the Faraday cup measurement that the rocket was considerably charged up by the precipitating electrons in the auroras.

SSC events at the geosynchronous altitude have been studied using data obtained from the geosynchronous satellites SMS/GOES, as well as data obtained on the ground for the period from 1976 to 1980. Two characteristic local time dependencies are found for the SSC associated phenomena at the geosynchronous altitude. In the compressional component (parallel to the ambient magnetic field direction), the SSC associated signature is very large in the noon-side, while it becomes smaller with increasing distance from the noon-side and is very small or zero in the midnight-side. In the transverse component (east-west direction), the direction of the initial movement of Psc changes drastically across the noon and the midnight. The direction is eastward in the morning-side, while it is westward in the evening-side. These observational results will be examined quantitatively in the present study.

1982年から1985年の間, 国際的に実施される中層大気観測計画(MAP)の一環として, 南極の昭和基地においても総合的な極域中層大気観測が実施される。中層大気の観測方法として, 地上, 飛行機, 衛星を用いてのリモートセンシングおよび飛行機, 気球, ロケットを用いての直接観測を行う。地上からのリモートセンシングによる主な観測装置は, レーザレーダー, VHFドップラーレーダー, 赤外分光, ドブソン法分光器などである。この論文では, これらプロジェクトの概要を示す。, Coordinated observations of the polar middle atmosphere are being carried out at Syowa Station in Antarctica as part of the Middle Atmosphere Program (MAP) for 1982-1985. The middle atmosphere is measured by a combination of remote sensing techniques from the ground, aircraft and spacecraft and in situ measurements by aircraft, balloon and sounding rocket. The main ground-based remote sensing facilities are laser radar, VHF doppler radar, infrared spectrometer and Dobson spectrophotometer. This paper gives an outline of this project.

A balloon observation of auroral X-rays was carried out over Syowa Station in Antarctica on December, 1985 by using a set of three inclined NaI (T1) scintillation counters. The energy-dependent structures of X-rays with energies greater than 22keV were measured. In a case study of the X-ray event occurred at 0145 UT on December 14,an X-ray source region moved toward lower latitudes with a velocity of about 1km/s. This experimental result was confirmed by a simulation calculation for auroral X-ray sources. The spatial distributions of auroral X-rays were found to be consistent with the north-south dependence of 30MHz cosmic noise absorption observed by a scanning-beam riometer at Syowa Station.

Conjugate observations of magnetic pulsations and ELF-VLF emissions were carried out at Syowa and Mizuho Stations in Antarctica and Husafell in Iceland during the northern summer seasons in 1977 and 1978. Husafell is located about 50km from the conjugate point of Syowa Station. Conjugacies of Pc 1,Pi 1 and Pc 3-5 magnetic pulsations are briefly summarized. It is also shown that the activity of polar chorus and quasi-periodic emissions observed in the daytime is well correlated at the conjugate points, while the conjugacy of discrete emissions and auroral hiss emissions observed in the nighttime is quite low.

Electromagnetic waves constructing auroral hiss in the VLF range were observed by the S-310JA-11 and -12 rockets launched into a quiet auroral arc and into a breakup aurora respectively, from Syowa Station in Antarctica. An altitude profile of the electric field intensity, which peaked at an altitude of 90km was observed by the S-310JA-12 rocket in the frequency range less than 5kHz. An estimation of the source location of the auroral hiss was made with the altitude profile of the hiss intensity calculated by the full wave analysis so as to agree with those observed especially around the altitude of 90km. It was found that the auroral hiss is most likely to be generated at an altitude about 700km or less. On the other hand, the absolute intensity of the auroral hiss at a frequency of 4kHz observed by the rocket, which was 9.4×10^ V/m/√, was much stronger, by about 50dB, than that observed at Syowa Station. This means that the k-vector direction of the auroral hiss actually observed by the rocket lay outside the transmission cone, so that the auroral hiss could reach Syowa Station with very week intensity.

Attitudes of the antarctic sounding rockets S-310JA-11 and S-310JA-12 launched from Syowa Station were determined from magnetometer and horizon aspect sensor data. The spin rate, precessional coning angle, and period determined for the S-310JA-11 and S-310JA-12 rockets were 0.57 and 0.59rps, 8.8 and 25.0 degrees, and 308 and 292 seconds, respectively.

A classification of the ULF-waves in the pc 1 and pi 1 frequency range was attempted on the basis of recent data (1976-78). Referring to the spectral structures of ULF waves, their similarities at the conjugate pair stations, their association with SC and SI events, and the correlations between auroras and VLF, it is shown that pc 1 and pi 1 ULF waves can be classified into six types with nine subclasses, as summarized in Table 1.

By using magnetic data measured at a network of stations extending from L approx. 3.2 to L approx. 4.4 and at a station in the conjugate area, ellipticities in the three orthogonal planes (H-D, H-Z, and D-Z) for the frequency range 2-5 mHz were computed continuously by the cross-spectral matrix method over 10 days with various levels of magnetic activity. The ellipticity diagrams in the H-D plane show that, except for the time interval during the main phase of a major magnetic storm, the sense of polarization reverses every day across local noon, with a left-hand polarization observed during local morning hours and a right-hand polarization observed during local evening hours, regardless of the level of magnetic activity. The second reversal of the sense of polarization occurs generally around approx. 2000 LT. The ellipticity diagrams in the H-Z plane show a predominantly clockwise polarization throughout the day, while the diurnal variation of the ellipticity in the D-Z plane tends to be confused. As to the latitude dependence of the wave phase, it is found that the D component oscillations are almost in phase at all latitudes, while the H component oscillations have advanced phase shifts at the lower-latitude stations. Asmore » to the conjugate dependence of wave phase, it is found that the D component oscillations are almost out of phase, while the H component oscillations are almost in phase atthe conjugate pair stations. These polarization characteristics are discussed in terms of external driving sources coupling to the shear Alfven waves of the local resonant field lines. Possible energy sources of Pc 5 waves are also discussed on the basis of the local time dependence of the sense of polarization. (AIP)« less

Statistical features of Pc1 pulsations are studied on the basis of data obtained at low- and high-latitude stations, Memambetsu in Japan and Syowa Station in Antarctica, during the period from January 1977 to January 1979. The observed features of high-latitude Pc1 can be divided into three groups, i.e., HM chorus, periodic emission and others (IPDP, Morning IPDP, dot, etc.). For the periodic emission, the generation mechanism is expected to be common to low and high latitudes.

昭和基地のほぼ地磁気共役点にあたる,アイスランドのHusafelにおいて,1977年7月29日から約50日間,ELF-VLF放射の共役点観測を行った.共役性についていえば,(1)昼間出現するポーラコーラス,準周期的(QP)放射の共役性は良い,(2)バーストタイプのティスクリート放射,オーロラコーラスの共役性は悪く,おもに北半球側が強い,(3)オーロラヒスの共役性は悪く,南半球(冬半球)側が圧倒的に強い.これらの観測結果から共役性の良いポーラコーラス,QP放射は磁気圏内の赤道面付近で発生し,磁力線に沿って伝搬しているものと理解できる.またオーロラヒス,バーストタイプ放射の非共役性は,電離層内の電子密度,磁場強度,磁力線の伏角等の南北半球での非対称およびこれらの放射の発生領域に依存すると思われる., Conjugate observations of ELF-VLF emissions, magnetic pulsations and auroras were carried out at Syowa Station in Antarctica and Husafell in Iceland from July 29, 1977 to September 18,1977. Husafell is located at a distance of about 50 km from the conjugate point of Syowa Station. Conjugacies of ELF-VLF emissions depend on emission types, such as polar chorus, quasiperiodic emissions, burst of discrete emissions and auroral hiss. Polar chorus and quasi-periodic emissions are observed simultaneously at the conjugate-pair stations. This suggests that the emissions are generated near the equatorial region in the outer magnetosphere and propagate to the both hemispheres along the field lines of force. Conjugacy of bursts of discrete emissions and auroral hiss is generally low. The emission intensity of auroral hiss is much stronger at Syowa Station (winter hemisphere) than at Husafell (summer hemisphere). Just the opposite tendency is observed for bursts of discrete emissions. The low conjugacy of these emissions may depend on the differences in geophysical conditions, such as the magnetic field, magnetic dip angle and the plasma density and also it depends on properties of the generation region of the emissions.

Polarization analyses were made on Pc1 and unstructured Pc 1-2 band pulsations observed at a conjugate pair, Husafell, Iceland and Syowa Station, Antarctica, in August and September 1977. It was found that L mode is predominant at Syowa Station, while R mode is at Husafell. From the comparison with the polarization at these stations, it was concluded that these two stations would not be in the conjugate relation in a strict sense at this time.

Electron density profiles in the auroral ionosphere were measured by the impedance probe on board the S-310JA-11 and -12 rockets. The S-310JA-11 rocket was launched from Syowa Station into quiet auroral arcs (-2kR) on May 29, 1985, while the S-310JA-12 rocket was launched into active arcs (-14kR) on July 12, 1985. The S-310JA-11 data showed a typical altitude profile of the electron number density in an auroral arc under geomagnetically quiet condition, with a peak number density of 2×105cm-3 at 115km altitude. The S-310JA-12 data, which was obtained in bright auroras in the expansion phase of a substorm, showed a peak density of 1.2×106cm-3 at 101km altitude. On the downleg of the S-310JA-12 rocket, strong irregularities in the electron density distribution were observed at F region height in the active auroral arc region. It is pointed out that the ionospheric structure in the E region is produced mainly by precipitating particles while that in the F region seems to be largely affected by dynamical processes.

Une serie de 5 fusees-sonde a ete lancee en 1984 et 1985 afin d'etudier la causalite entre le spectre d'energie des particules aurorales et les emissions de lumiere aurorale pendant differentes etapes de sous-orages polaires d'une part, et les processus d'interactions ondes-particules sur les lignes de champ aurorales d'autre part. Les objectifs scientifiques et les instruments de mesures sont brievement decrits. Les conditions geomagnetiques pendant les lancements sont presentees et les resultats scientifiques compares aux observations basees au sol

A sounding rocket with double-probes for DC electric field and AC electric field (5-220Hz band) measurement was launched from Syowa Station in Antarctica around the onset time of an intense auroral substorm. The rocket first encountered a poleward expanding auroral arc, where intense (1.4mV/m) and broad band electric field fluctuations were measured around the arc at the altitude of 105-128km. The rocket then moved across an equatorward drifting arc, where narrow-band electric field fluctuations around 40Hz were measured at the altitude of ∿190km. Considering the DC electric field data and the electron density gradient observed on the same rocket, it is likely that the former fluctuation is due to drift waves or ion acoustic waves excited by the cross-field type or two-stream type plasma instability, while the latter is due to electrostatic ion cyclotron waves excited by fieldaligned currents.

第26次南極地域観測隊越冬隊では国際中層大気観測計画(MAP)に呼応して, 1985年の冬季に2機のオーロラ探査ロケットを打ち上げる計画である。この観測はオーロラ発光高度での波動-粒子相互作用の過程を明らかにすることを目的としている。この論文では観測計画の概要を述べる。, It is scheduled that two sounding rockets are launched from Syowa Station, Antarctica in the austral winter of 1985 as part of the international Middle Atmosphere Program (MAP), by the wintering party of the 26th Japanese Antarctic Research Expedition. This experiment aims at the study of the wave-particle interaction processes on auroral field lines. The present paper gives an outline of the mission plan of the experiment.

A stratospheric balloon, carrying a NaI (T1) scintillation counter for measuring 20-100keV bremsstrahlung X-ray was launched from Stamsund (L=5.6) in Norway during the recovery phase of a magnetospheric substorm. The scintillation counter recorded X-ray pulsations with periods of 20-30s when the balloon was located at L=5.4-4.8 and at 0950-1300 MLT. A rising tone type of quasi-periodic (QP) VLF emissions and Pc 3 magnetic pulsations observed at Andoya (L=6.15), located at 160km northeast of Stamsund, were closely associated with these X-ray pulsations. The one-to-one correspondence between occurrences of QP emissions and enhancements of X-ray count rate suggests that QP emissions (whistler mode waves) modulate the pitch angle diffusion rate of energetic electrons trapped in the magnetosphere through the cyclotron interaction. Further a close relation between QP emissions and Pc 3 magnetic pulsations suggests that compressional mode Pc 3 waves propagating in radial direction from the dayside magnetopause toward the earth modulate the growth rate of whistler mode waves.

The measurements on polar stratospheric aerosol particles using lidar and meteorological sonde at Syowa Station (69°00′S, 39°35′E), Antarctica revealed that the content of stratospheric aerosols noticeably increased in winter when atmospheric temperature frequently fell down to about -80°C in the lower atmosphere, and that the depolarization ratio of the backscattered light from the enhanced stratospheric aerosols also has very large value (at least larger than 0.5 during the fully developed enhancement period).

167 SSC events have been studied by using the data observed at the multiple-satellites at the geosynchronous altitude. The strong local time asymmetry of the SSC amplitude which was found by Kokubun (1983) has been confirmed. The pronounced local time asymmetry has also been found with the direction of the initial movement of Psc magnetic pulsations. Those local time effects are interpreted by the intensification of the magnetopause surface current during a SSC event, and by the distance between the geosynchronous satellite and the surface current. It has also been clarified that the SSC signal propagates with a speed of 400–700 km s−1 across the field lines in the magnetosphere as suggested by Wilken et al. (1982).

This report describes the lidar measurement of mesospheric sodium layer made at Syowa Station (69°00'S, 39°35'E) in 1985. Our result does not show any pronounced seasonal variation in sodium abundance. Auroral activity may have disturbed the sodium layer significantly.

Simultaneous observations using two-channel meridian scanning photometers were carried out at geomagnetically conjugate-pair stations, Syowa Station in Antarctica and Husafell in Iceland (L=6.1), during August-September 1984. The photometers were equipped with interference filters for OI 5577A and Hs 4861A emissions. During the conjugate campaign, the data obtained on September 26, 1984 was of the highest quality with a clear sky and no moon. The initial results on the conjugacy of Hs proton auroras and their relations to 5577A electron auroras are as follows; i) During the pre-breakup phase the Hs auroras observed at Syowa were mostly located at a lower latitude than the simultaneous conjugate auroras observed at Husafell. Such Hs auroras showed high intensities at Syowa relatively to those at Husafell, ii) During the auroral breakup phase, enhancement of Hs emissions occurred almost simultaneously in the both hemispheres. However, the intensities of Hs auroras were higher at Husafell than at Syowa, iii) During the pre-breakup phase, Hs auroras observed continuously in the equator boundary were associated with weak diffuse 5577A auroras in the conjugate regions, (iv) In the regions and time intervals where 5577A auroras showed poor conjugacy, the Hs auroras also showed poor conjugacy.

A comparison is made of magnetohydrodynamic waves observed near the equator on Explorer 45 and at an array of ground stations in the northern hemisphere and at their conjugate station at Siple, Antarctica. The data comparisons strongly support the notion that the observed waves can be considered odd mode standing waves in the magnetosphere. This conclusion has important implications for the interpretation of single-point satellite and/or ground measurements of ULF plasma wave phenomena in the magnetosphere. Further, the data comparisons strongly suggest that the overall ULF (∼5–30 mHz) power levels are quite similar in the magnetosphere and on the ground, at least during the intervals studied.

The S-310JA-11 and S-310JA-12 rockets, having a vector magnetometer with high sensitivity (1.8nT) and high sampling frequency (100Hz), were launched into the aurora on May 29 and July 12, 1985, from Syowa Station, Antarctica. The S-310JA-11 rocket penetrated twice quiet arcs, while the S-310JA-12 rocket traversed across intense and active auroral arcs during a large magnetic substorm. In the S-310JA-12 rocket experiment, intense field-aligned currents of 400-600nT were observed when the rocket penetrated an active arc during the descending flight. The magnetometer on board the S-310JA-12 rocket also detected intense electrojet currents with a center at 110km on the upward leg and at 108km on the downward leg. The magnetometer data of the S-310JA-11 rocket showed no distinguished magnetic field variation due to field-aligned current and electrojet.

By using cross-power spectral analysis techniques the amplitudes and polarization characteristics of geomagnetic variations in the three frquency bands of 2–5 mHz, 10–15 mHz, and 15–27 mHz are studied nonstatistically as functions of latitude and local time for 22 days. It is found that during the local day the diurnal changes in the polarization characteristics of the magnetic field variations in the highest- and lowest-frequency bands are very similar to the polarization characteristics arising from the analyses of discrete well-defined Alfven wave events in the same frequency ranges. This important result lends very strong additional evidence to the hypothesis that most local day magnetic fluctuations are controlled largely by a source external to the magnetosphere, probably the solar wind. During local night the results are consistent with a source propagation direction predominantly from local morning toward local evening. The results for the 10- to 15-mHz band are less clear and suggest that the geomagnetic variations are affected to a significant extent by plasma gradients (probably at the plasmapause) generally occurring within the latitude range of the present set of stations.

The laser radar system used for the monitoring of the polar middle atmosphere (10km-120km) is discussed. This system can emit laser pulses at three different wavelengths : 694nm, 589nm and 347nm. The laser radar measurements make an important contribution to clarify the behavior of stratospheric aerosols, the formation of stratospheric "Cist", and the interaction between noctilucent cloud particles and charged particles in the lower ionosphere of the polar region.

1977年7月29日-9月18日まで52日間にわたってアイスラントフサヘルおよび南極昭和,みずほ基地で観測された地磁気脈動データの解析から以下のことが明らかになった.(1)中心周波数が,20-40mHzおよび4-8mHzの2つのバントが,昼間観測される(2)f-tスペクトルの構造は,共役点で非常に類似している.(3)これら脈動の位相は,共役点でH成分がin-phase,D成分がout-of-phaseの関係を示す(4)H-D平面における楕円偏波の主軸の向きは,12MLTを境に反転するこれらの結果から昼間のPc3-5脈動は,磁気圏,境界面またはその外側でつくり出されたMHD波動が,磁気圏内に伝わり磁力線のodd-mode standing oscillationを励起させたものと考えられる., From the magnetic pulsation data recorded at the Syowa Station-Iceland conjugate pair, it is found that there are at least two pulsation bands in the Pc 3-5 frequency range in the daytime. 0ne pulsation band occurs in the 20-40 mHz range, while the other band occurs in the 4-8 mHz range, often independently of the 20-40 mHz band. The f-t spectral patterns of these pulsations are quite similar at the coniugate points, with the wave phase characteristics of odd-mode standing oscillations of local magnetic field lines. It is also found that the orientation angles of the polarization ellipses in the H-D plane switch across the magnetic local noon. These results suggest that the 20-40 mHz band and the 4-8 mHz band are standing oscillations of resonant field lines excited by external driving forces such as the Kelvin-Helmholtz instability on the magnetopause and/or the MHD waves generated near the bow shock

The results are given on the DC electric field in an active auroral arc and outside the equatorside of it observed with two pairs of orthogonal double probes launched by an Antarctic sounding rocket S-310JA-7 at 191550 UT on March 27,1978 at Syowa Station. The north-south component of the observed electric field was northward (equatorward) in the arc, and southward (poleward) outside the equatorside of the arc with a magnitude of about 20mV/m. The east-west component was mostly westward throughout the rocket flight and smaller (about 5mV/m) in the arc and larger (about 50mV/m) outside the arc. Anticorrelation of the electric field and precipitating particles is evident. An examination of the oppositely inward directed electric fields in the meridional cross section suggests an electrostatic potential configuration responsible for the acceleration of precipitating particles. The observed westward component would have been originated in the large scale earthward plasma convection in the magnetosphere.

The attitude of two sounding rockets, S-310JA-11 and -12 launched at Syowa Station on May 29 and July 12,1985,were determined using magnetometers and horizon aspect sensors. The spin rate of the S-310JA-11 rocket was 0.57rps and the coning half angle of the precession was 8.8° with the period of 308s. The spin rate of the S-310JA-12 rocket was 0.59rps and the coning half angle of the precession was 25.0° with the period of 292s.