資料8-G

Commission G Report
December 24, 2014
1. Research Report
1.1. Report from National Institute of Communications and Information (NICT)(Minoru Kubota, NICT)=== Report from recent papers ===(1) A system to optimize the management of global space-weather observation networks has beendeveloped by the National Institute of Information and Communications Technology (NICT).
Named the WONM (Wide-area Observation Network Monitoring) system, it enables dataacquisition, transfer, and storage through connection to the NICT Science Cloud, and has been
supplied to observatories for supporting space-weather forecast and research. This systemprovides us with easier management of data collection than our previously employed systems bymeans of autonomous system recovery, periodical state monitoring, and dynamic warning
procedures. Operation of the WONM system is introduced in this report.
(2) We analyze the ionogram data recorded by the Frequency Modulated Continuous Wave (FM/CW)
ionosondes for the periods of minimum solar activity from September 2008 to April 2009 and in
the equinoctial months (March and April) from 2006 to 2013. The spread-F signatures aremanually categorized into three types: the frequency spread-F (FSF), the range spread-F (RSF)
and the mixed spread-F (MSF) and the monthly average percentage of the occurrence of each ESF
type is presented. The results show that the percentage of RSF occurrence at CPN, which islocated around the magnetic equator, is higher than at other stations and the RSF mostly occurs
during the equinoctial months. On the other hand, the FSF occurrence at CMU and KTB, that arelocated in the northern and southern hemispheres, respectively, are higher than at CPN. The RSF
occurrence typically has the peaks before midnight, while the maximum occurrence rate of FSF isafter midnight. Furthermore, the RSF onsets normally precede the FSF onsets by about 1-2 h. As
the solar activity levels go up, the percentages of RSF occurrence increase, but the percentages of
FSF tends to decrease. In addition, we compare the statistics of observed RSF occurrence with theprediction of the IRI-2012 model. This work is important for an improvement of the IRI model inthe prediction of the spread F occurrence probability in the low-latitude region.
Reference(1) Citation: Nagatsuma, T., K. T. Murata, K. Yamamoto, T. Tsugawa, H. Kitauchi, T. Kondo, H.
Ishibashi, M. Nishioka, and M. Okada (2014), Operation of a data acquistion, transfer, and storage
system for the global space-weather observation network, Data Science Journal, Vol. 13 (2014) p.
PDA51-PDA56(2) Klinngam, S., P. Supnithi, S. Rungraengwajiake, T. Tsugawa, M. Ishii, and T. Maruyama (2014),
The occurrence of equatorial spread-F at conjugate stations in Southeast Asia, Adv. Space Res, inpress.

資料8-G

1.2. Report from Solat-Terrestrial Environmental Laboratory, Nagoya University(Satonori Nozawa, Nagoya University)=== Report from recent papers ===The characteristics of nighttime medium-scale travelling ionospheric disturbance (MSTID) features
observed over Yonaguni (24.5oN, 123.0oE; 19.3oN dip latitude), Japan are studied using all-sky
imaging of OI 630.0 nm airglow emission. The uniqueness of these observations is that the area
observed by the imager covers the transition region between low to middle latitudes in the ionosphere.
Typical low latitude limit of mid-latitude type nighttime MSTIDs possessing phase front alignments
along the northwest to the southeast occurs in this region. These MSTID features are rarely sighted at
dip latitudes below 15o. We selected two year period for analysis in which one year corresponded tothe solar minimum conditions and another year to the solar maximum conditions. The MSTIDs wereobserved to extend to farther lower latitudes during the solar minimum conditions than during the solar
maximum periods. Their observed range of wavelengths, phase velocities, phase front alignment andpropagation directions are similar to those observed at typical mid-latitude sites. However, on manyoccasions the phase fronts of the observed MSTIDs did not extend over the whole field of view of theimager indicating that some process inhibits their extension to further lower latitudes. Detailed
investigation suggests that the poleward propagating enhancement of airglow intensity, probably
associated with the midnight pressure bulge, causes the MSTID features to disappear when they reach
lower latitudes later in the night. When the MSTIDs reach lower latitudes well before midnight, they
are found to be inhibited by the equatorial ionization anomaly crest region.
Reference

V. Lakshmi Narayanan, K. Shiokawa, Y. Otsuka, S. Saito, Airglow observations of nighttime
medium-scale traveling ionospheric disturbances from Yonaguni: Statistical characteristics andlow latitude limit, J. Geophys. Res., in press, doi: 10.1029/2014JA020368, 2014.
1.3. Report from National Institute for Polar Research(Yasunobu Ogawa, NIPR)=== Report from recent PANSY-related papers ===(1) The PANSY radar is the first Mesosphere–Stratosphere–Troposphere/Incoherent Scatter (MST/IS)
radar in the Antarctic region. It is a large VHF monostatic pulse Doppler radar operating at 47
MHz, consisting of an active phased array of 1045 Yagi antennas and an equivalent number oftransmit–receive (TR) modules with a total peak output power of 500 kW. The first stage of theradar was installed at Syowa Station (69°00′S, 39°35′E) in early 2011, and is currently
operating with 228 antennas and modules. This paper reports the project's scientific objectives,technical descriptions, and the preliminary results of observations made to date. The radar isdesigned to clarify the role of atmospheric gravity waves at high latitudes in the momentum
budget of the global circulation in the troposphere, stratosphere and mesosphere, and to explore
the dynamical aspects of unique polar phenomena such as polar mesospheric clouds (PMC) andpolar stratospheric clouds (PSC). The katabatic winds as a branch of Antarctic troposphericcirculation and as an important source of gravity waves are also of special interest. Moreover,strong and sporadic energy inputs from the magnetosphere by energetic particles and field-aligned
currents can be quantitatively assessed by the broad height coverage of the radar which extends
from the lower troposphere to the upper ionosphere. From engineering points of view, the radar
had to overcome restrictions related to the severe environments of Antarctic research, such as verystrong winds, limited power availability, short construction periods, and limited manpower

資料8-G

availability. We resolved these problems through the adoption of specially designed class-E
amplifiers, light weight and tough antenna elements, and versatile antenna arrangements.
Although the radar is currently operating with only about a quarter of its full designed systemcomponents, we have already obtained interesting results on the Antarctic troposphere,
stratosphere and mesosphere, such as gravity waves, multiple tropopauses associated with a severe
snow storm in the troposphere and stratosphere, and polar mesosphere summer echoes (PMSE).
(2) Strong meteor trail echoes are interferences in the wind velocity estimates made from mesosphereradar observations. Contaminated spectra are detected by their discontinuity and are removed at
the risk of greater fluctuations of spectra, leading to a severe reduction of the signal-to-noise ratio(SNR) and inaccurate wind estimates for weak atmospheric echoes. This paper presents anadaptive signal processing technique for the suppression of spectral contaminations by meteor trail
echoes. The method is based on the norm-constrained and directionally-constrained minimizationof power (NC-DCMP), which balances the capability of canceling the clutter and the robustness ofbeam shaping, at the cost of a slight decrease in the SNR, which can be determined in advance.
Simulation results show that with a 3 dB decrease of the SNR being allowed, the method improves
the signal-to-interference ratio (SIR) by 15 dB, giving wind estimates that are about 8 m s −1
better in terms of root-mean-square error and providing four times as wide an observable range
when compared with the results of the ordinary non-adaptive beamforming method. The results
for an actual observation show that the improvement of both the SIR and the observable range areachieved as in the simulations, which implies that the method should provide the simulated
accuracy for the estimation of wind velocity from actual observations.
References(1) Sato, K., M. Tsutsumi, T. Sato, T. Nakamura, A. Saito, Y. Tomikawa, K. Nishimura, M. Kohma,
H. Yamagishi, and T. Yamanouchi, Program of the Antarctic Syowa MST/IS Radar (PANSY), J.
Atmos. Solar-Terr. Phys., 118A, 2-15, 2014.
(2) Hashimoto, T., K. Nishimura, M. Tsutsumi, and T. Sato, Meteor Trail Echo Rejection in
Atmospheric Phased Array Radars Using Adaptive Sidelobe Cancellation, J. Atmos. Oceanic
Tech., in press, 2014.
=== Report from recent EISCAT-related papers ===(1) Theoretical models and observations have suggested that the increasing greenhouse gas
concentration in the troposphere causes the upper atmosphere to cool and contract. However, ourunderstanding of the long-term trends in the upper atmosphere is still quite incomplete, due to alimited amount of available and well-calibrated data. The European Incoherent Scatter radar hasgathered data in the polar ionosphere above Tromsø for over 33 years. Using this long-term dataset, we have estimated the first significant trends of ion temperature at altitudes between 200 and
450 km. The estimated trends indicate a cooling of 10–15 K/decade near the F region peak (220–380 km altitude), whereas above 400 km the trend is nearly zero or even warming. The heightprofiles of the observed trends are close to those predicted by recent atmospheric generalcirculation models. Our results are the first quantitative confirmation of the simulations and of thequalitative expectations.
(2) Auroral patches in diffuse auroras are very common features in the postmidnight local time.
However, the processes that produce auroral patches are not yet well understood. In this paper we
present two examples of auroral fragmentation which is the process by which uniform aurora is
broken into several fragments to form auroral patches. These examples were observed at
Athabasca, Canada (geomagnetic latitude: 61.7°N), and Tromsø, Norway (67.1°N). Captured in資料8-G

sequences of images, the auroral fragmentation occurs as finger-like structures developing
latitudinally with horizontal-scale sizes of 40–100 km at ionospheric altitudes. The structures tend
to develop in a north-south direction with speeds of 150–420 m/s without any shearing motion,suggesting that pressure-driven instability in the balance between the earthward magnetic-tension
force and the tailward pressure gradient force in the magnetosphere is the main driving force of
the auroral fragmentation. Therefore, these observations indicate that auroral fragmentation
associated with pressure-driven instability is a process that creates auroral patches. The observed
slow eastward drift of aurora during the auroral fragmentation suggests that fragmentation occurs
in low-energy ambient plasma.
Reference(1) Ogawa, Y., T. Motoba, S. C. Buchert, I. Haggstrom and S. Nozawa, Upper atmosphere coolingover the past 33 years, Geophys. Res. Lett., 41, doi:10.1002/2014GL060591, 2014.
(2) Shiokawa, K., A. Hashimoto, T. Hori, K. Sakaguchi, Y. Ogawa, E. Donovan, E. Spanswick,
M. Connors, Y. Otsuka, S.-I. Oyama, S. Nozawa, K. McWilliams, Auroral fragmentation into
patches, J. Geophys. Res., 119, doi:10.1029/2014JA020050, 2014.
=== List of papers related to PANSY and EISCAT since January 2014 ===1.

Sato, K., M. Tsutsumi, T. Sato, T. Nakamura, A. Saito, Y. Tomikawa, K. Nishimura, M.
Kohma, H. Yamagishi, and T. Yamanouchi, Program of the Antarctic Syowa MST/IS Radar(PANSY), J. Atmos. Solar-Terr. Phys., 118A, 2-15, 2014.
2. Hashimoto, T., K. Nishimura, M. Tsutsumi, and T. Sato, Meteor Trail Echo Rejection in
Atmospheric Phased Array Radars Using Adaptive Sidelobe Cancellation, J. Atmos. Oceanic
Tech., in press.
3. Takahashi, T., S. Nozawa, M. Tsutsumi, C. Hall, S. Suzuki, T. T. Tsuda, T. D. Kawahara, N.
Saito, S. Oyama, S. Wada, T. Kawabata, H. Fujiwara, A. Brekke, A. Manson, C. Meek, andR.Fujii, A case study of gravity wave dissipation in the polar MLT region using sodium
LIDAR and radar data, Ann. Geophys., 32, 1195-1205, 2014.
4. Shiokawa, K., A. Hashimoto, T. Hori, K. Sakaguchi, Y. Ogawa, E. Donovan, E. Spanswick,
M. Connors, Y. Otsuka, S.-I. Oyama, S. Nozawa, K. McWilliams, Auroral fragmentation into
patches, J. Geophys. Res., 119, doi:10.1029/2014JA020050, 2014.
5. Fujiwara, H., S. Nozawa, Y. Ogawa, R. Kataoka, Y. Miyoshi, H. Jin, and H. Shinagawa,Extreme ion heating in the dayside ionosphere in response to the arrival of a coronal massejection on 12 March 2012, Ann. Geophys., 32, 831-839, doi:10.5194/angeo-32-831-2014,
2014.
6. Ishida, T., Y. Ogawa, A. Kadokura, Y. Hiraki, and I. Haggstrom, Seasonal variation and solar
activity dependence of the quiet-time ionospheric trough, J. Geophys. Res.,
doi:10.1029/2014JA019996, 2014.
7. Ogawa, Y., T. Motoba, S. C. Buchert, I. Haggstrom and S. Nozawa, Upper atmospherecooling over the past 33 years, Geophys. Res. Lett., 41, doi:10.1002/2014GL060591, 2014.
8. Sakai, J., K. Hosokawa, S. Taguchi, Y. Ogawa, Storm-time enhancements of 630.0-nm
airglow associated with polar cap patches, J. Geophys. Res., 119, doi:10.1029/2013JA019197,
2014.
9. Oyama, S., Y. Miyoshi, K. Shiokawa, J. Kurihara, T. T. Tsuda, and B. J. Watkins, Heightdependent ionospheric variations in the vicinity of nightside poleward expanding aurora after
substorm onset, J. Geophys. Res., 119, doi:10.1002/2013JA019704, 2014.
10. Nozawa, S., T. Kawahara, N. Saito, C. Hall, T. Tsuda, T. Kawabata, S. Wada, A. Brekke, T.
Takahashi, H. Fujiwara, Y. Ogawa, and R. Fujii, Variations of the neutral temperature and資料8-Gsodium density between 80 and 107 km above Tromsoe during the winter of 2010-2011 by a
new solid state sodium LIDAR, J. Geophys. Res., 119, doi:10.1029/2013JA019520, 2014.
11. Vickers, H., M. J. Kosch, E. Sutton, L. Bjoland, Y. Ogawa and C. La Hoz, A solar cycle ofupper thermosphere density observations from the EISCAT Svalbard Radar, J. Geophys. Res.,
doi:10.1029/2014JA019885, 2014.
12. Kero, A., J. Vierinen, D. McKay-Bukowski, C.-F. Enell, M. Sinor, L. Roininen, and Y.
Ogawa, Ionospheric electron density profiles inverted from a spectral riometer measurement,
Geophys. Res. Lett., doi:10.1002/2014GL060986, 2014.
13. Kosch, M. J., H. Vickers, Y. Ogawa, A. Senior, and N. Blagoveshchenskaya, First
observation of the anomalous electric field in the topside ionosphere by ionosphericmodification over EISCAT, Geophys. Res. Lett., doi:10.1002/2014GL061679, 2014.
14. Kosch, M. J., C. Bryers, M.T. Rietveld, T. K. Yeoman, and Y. Ogawa, Aspect angle
sensitivity of pump-induced optical emissions at EISCAT, Earth, Planets and Space,
1301071410132468, in press.
1.4. Report from Graduate School of Science, Tohoku University(Takeshi Sakanoi, Tohoku University)=== Report from recent papers ===(1) We present phase curves for Venus in the 1–2 μm wavelength region, acquired with IR1 and IR2
on board Akatsuki (February–March 2011). A substantial discrepancy with the previouslypublished curves was found in the small phase angle range (0–30°). Through analysis by radiativetransfer computation, it was found that the visibility of larger (∼1 μm or larger) cloud particles was
significantly higher than in the standard cloud model. Although the cause is unknown, this may berelated to the recently reported increase in the abundance of SO2 in the upper atmosphere. It wasalso found that the cloud top is located at ∼75 km and that 1-μm particles exist above the cloud,
both of these results being consistent with recent studies based on the Venus Express observationsin 2006–2008. Further monitoring, including photometry for phase curves, polarimetry for aerosol
properties, spectroscopy for SO2 abundance, and cloud opacity measurements in the near-infraredwindows, is required in order to understand the mechanism of this large-scale change.
(2) HISAKI (SPRINT-A) satellite is an earth-orbiting Extreme UltraViolet (EUV) spectroscopic
mission and launched on 14 Sep. 2013 by the launch vehicle Epsilon-1. Extreme ultraviolet
spectroscope (EXCEED) onboard the satellite will investigate plasma dynamics in Jupiter’s innermagnetosphere and atmospheric escape from Venus and Mars. EUV spectroscopy is useful tomeasure electron density and temperature and ion composition in plasma environment. EXCEED
also has an advantage to measure spatial distribution of plasmas around the planets. To measureradial plasma distribution in the Jovian inner magnetosphere and plasma emissions fromionosphere, exosphere and tail separately (for Venus and Mars), the pointing accuracy of thespectroscope should be smaller than spatial structures of interest (20 arc-seconds). For satellites in
the low earth orbit (LEO), the pointing displacement is generally caused by change of alignment
between the satellite bus module and the telescope due to the changing thermal inputs from theSun and Earth. The HISAKI satellite is designed to compensate the displacement by tracking thetarget with using a Field-Of-View (FOV) guiding camera. Initial checkout of the attitude control
for the EXCEED observation shows that pointing accuracy kept within 2 arc-seconds in a case of“track mode” which is used for Jupiter observation. For observations of Mercury, Venus, Mars,and Saturn, the entire disk will be guided inside slit to observe plasma around the planets. Since
the FOV camera does not capture the disk in this case, the satellite uses a star tracker (STT) to資料8-G

hold the attitude (“hold mode”). Pointing accuracy during this mode has been 20–25 arc-seconds.
It has been confirmed that the attitude control works well as designed.
(3) The Sprint-A satellite with the EUV spectrometer (Extreme Ultraviolet Spectroscope for
Exospheric Dynamics: EXCEED) was launched in September 2013 by the Epsilon rocket. Now it
is orbiting around the Earth (954.05 km×1156.87 km orbit; the period is 104 minutes) and one has
started a broad and varied observation program. With an effective area of more than 1 cm2 andwell-calibrated sensitivity in space, the EUV spectrometer will produce spectral images (520–1480 Å) of the atmospheres/magnetospheres of several planets (Mercury, Venus, Mars, Jupiter,and Saturn) from the Earth’s orbit. At the first day of the observation, EUV emissions from the Io
plasma torus (mainly sulfur ions) and aurora (H2 Lyman and Werner bands) of Jupiter have been
identified. Continuous 3-month measurement for Io’s plasma torus and aurora is planned towitness the sporadic and sudden brightening events occurring on one or both regions. For Venus,
the Fourth Positive (A1 Π-X1 Σ +) system of CO and some yet known emissions of theatmosphere were identified even though the exposure was short (8-min). Long-term exposure
from April to June (for approximately 2 months) will visualize the Venusian ionosphere and tail in
the EUV spectral range. Saturn and Mars are the next targets.
(4) Jupiter’s magnetosphere is a strong particle accelerator that contains ultrarelativistic electrons in
its inner part. They are thought to be accelerated by whistler-mode waves excited by anisotropic
hot electrons (>10 kiloelectron volts) injected from the outer magnetosphere. However, electrontransportation in the inner magnetosphere is not well understood. By analyzing the extreme
ultraviolet line emission from the inner magnetosphere, we show evidence for global inward
transport of flux tubes containing hot plasma. High-spectral-resolution scanning observations of
the Io plasma torus in the inner magnetosphere enable us to generate radial profiles of the hot
electron fraction. It gradually decreases with decreasing radial distance, despite the shortcollisional time scale that should thermalize them rapidly. This indicates a fast and continuous
resupply of hot electrons responsible for exciting the whistler-mode waves.
(5) We searched for hydrogen peroxide (H2O2) in the Martian atmosphere using data measured by
the Planetary Fourier Spectrometer (PFS) onboard Mars Express during five martian years(MY27–31). It is well known that H2O2 plays a key role in the oxidizing capacity of the Martian
atmosphere. However, only a few studies based on ground-based observations can be found in theliterature. Here, we performed the first analysis of H2O2 using long-term measurements by aspacecraft-borne instrument. We used the ν4 band of H2O2 in the spectral range between 359
cm−1 and 382 cm−1 where strong features of H2O2 are present around 362 cm−1 and 379 cm−1.
Since the features were expected to be very weak even at the strong band, sensitive datacalibrations were performed and a large number of spectra were selected and averaged. We madethree averaged spectra for different seasons over relatively low latitudes (50°S–50°N). We foundfeatures of H2O2 at 379 cm−1, whereas no clear features were detected at 362 cm−1 due to large
amounts of uncertainty in the data. The derived mixing ratios of H2O2 were close to the detection
limits: 16 ± 19 ppb at Ls = 0–120°, 35 ± 32 ppb at Ls = 120–240°, and 41 ± 28 ppb at Ls = 240–
360°. The retrieved value showed the detection of H2O2 only for the third seasonal period, and thevalues in the other periods provided the upper limits. These long-term averaged abundances
derived by the PFS generally agreed with the ones reported by ground-based observations. From
our derived mixing ratio of H2O2, the lifetime of CH4 in the Martian atmosphere is estimated to
be several decades in the shortest case. Our results and sporadic detections of CH4 suggest thepresence of strong CH4 sinks not subject to atmospheric oxidation.
(6) We have investigated the cloud top structure of Venus by analyzing ground-based images taken at
the mid-infrared wavelengths of 8.66 μm and 11.34 μm. Venus at a solar phase angle of ∼90°, with

資料8-G

the morning terminator in view, was observed by the Cooled Mid-Infrared Camera andSpectrometer (COMICS), mounted on the 8.2-m Subaru Telescope, during the period October 25–
29, 2007. The disk-averaged brightness temperatures for the observation period are ∼230 K and ∼238 K at 8.66 μm and 11.34 μm, respectively. The obtained images with good signal-to-noise ratio
and with high spatial resolution (∼200 km at the sub-observer point) provide several important
findings. First, we present observational evidence, for the first time, of the possibility that the
westward rotation of the polar features (the hot polar spots and the surrounding cold collars) is
synchronized between the northern and southern hemispheres. Second, after high-pass filtering,the images reveal that streaks and mottled and patchy patterns are distributed over the entire disk,
with typical amplitudes of ∼0.5 K, and vary from day to day. The detected features, some of which
are similar to those seen in past UV images, result from inhomogeneities of both the temperatureand the cloud top altitude. Third, the equatorial center-to-limb variations of brightness
temperatures have a systematic day–night asymmetry, except those on October 25, that thedayside brightness temperatures are higher than the nightside brightness temperatures by 0–4 K
under the same viewing geometry. Such asymmetry would be caused by the propagation of the
migrating semidiurnal tide. Finally, by applying the lapse rates deduced from previous studies, wedemonstrate that the equatorial center-to-limb curves in the two spectral channels give access to
two parameters: the cloud scale height H and the cloud top altitude zc. The acceptable models fordata on October 25 are obtained at H = 2.4–4.3 km and zc = 66–69 km; this supports previous
results determined from spacecraft observations.
(7) The propagation of compressional Pi 2 waves in the inner magnetosphere is investigated byanalyzing the onset delay times between the ground and the geosynchronous altitude. We use thecompressional component (northward) of magnetic data from low-latitude stations and thegeosynchronous satellite ETS-VIII (GMLat. = -10.8°, GMLon. = 217.5°). The onset delays are
determined by a cross-correlation analysis, and we analyzed the events with high waveform
correlations (correlation coefficient greater than 0.75). Some of these high-correlation events havethe properties of propagating waves; Pi 2 waveforms at the ground stations and the satellite weresynchronized with each other when the data were shifted by onset delays. The results of thestatistical analysis show that 87% of the Pi 2 onsets at a ground station (Kuju, GMLat. = 26.13°,
GMLon. = 202.96°) were delayed from the Pi 2 onsets at ETS-VIII, and the average of the delay
times was 29 sec. This clearly shows Pi 2 onsets (initial perturbations of Pi 2) propagated from thegeosynchronous altitude to the low-latitude ground. The delay times tended to be larger around the
midnight sector than around the dawn and dusk sectors. These results are consistent with twodimensional propagation of fast waves estimated by the model of Uozumi et al. (J Geophys Res
114:A11207, 2009). The delay times are nearly identical to the travel time of fast waves fromgeosynchronous altitude to the low-latitude ground, and the local time variation of the delay
shows the azimuthal propagation along the geosynchronous orbit. We conclude that the initial
compressional perturbations of Pi 2 waves propagate radially and longitudinally as a fast wave in
the inner magnetosphere.
(8) We report observations of very low frequency (VLF) and extremely low frequency (ELF) chorus
waves taken during the ELF/VLF Campaign observation with High-resolution Aurora Imaging
Network (VLF-CHAIN) of 17–25 February 2012 at subauroral latitudes at Athabasca (L=4.3),
Canada. ELF/VLF waves were measured continuously with a sampling rate of 100 kHz to monitor
daily variations in ELF/VLF emissions and derive their detailed structures. We foundquasiperiodic (QP) emissions whose repetition period changes rapidly within a period of 1 h
without corresponding magnetic pulsations. QP emissions showed positive correlation between
amplitude and frequency sweep rate, similarly to rising-tone elements. We found an event ofnearly simultaneous enhancements of QP emissions and Pc1/electromagnetic ion cyclotron wave

資料8-G

intensities, suggesting that the temperature anisotropy of electrons and ions developed
simultaneously at the equatorial plane of the magnetosphere. We also found QP emissions whose
intensity suddenly increased in association with storm sudden commencement without changing
their frequency. Falling-tone ELF/VLF emissions were observed with their rate of frequencychange varying from 0.7 to 0.05 kHz/s over 10 min. Bursty-patch emissions in the lower andupper frequency bands are often observed during magnetically disturbed periods. Clear systematic
correlation between these various ELF/VLF emissions and cosmic noise absorption was not
obtained throughout the campaign period. These observations indicate several previously
unknown features of ELF/VLF emissions in subauroral latitudes and demonstrate the importanceof continuous measurements for monitoring temporal variations in these emissions.
(9) We present a newly developed parameterization of radiative heating and cooling for Jupiter’s
upper troposphere and stratosphere (103 to View the MathML source) suitable for generalcirculation models. The scheme is based on the correlated k-distribution approach, and accounts
for all the major radiative mechanisms in the jovian atmosphere: heating due to absorption of solar
radiation by methane, cooling in the infrared by methane, acetylene, ethane, and collisionallyinduced molecular hydrogen–hydrogen, and molecular hydrogen–helium transitions. The resultswith the scheme are compared with line-by-line calculations to demonstrate that the accuracy ofthe scheme is within 10%. The parameterization was applied to study the sensitivity of theheating/cooling rates due to variations of mixing ratios of hydrocarbon molecules. It was also used
for calculating the radiative–convective equilibrium temperature, which is in agreement withobservations in the equatorial region. In midlatitudes, the equilibrium temperature isapproximately 10 K colder. Our results suggest that the radiative forcing in the upper stratosphereis much stronger than it was thought before. In particular, the characteristic radiative relaxation
time decreases exponentially with height from View the MathML source near the tropopause toView the MathML source in the upper stratosphere.

Reference(1) Takehiko Satoh Shoko Ohtsuki, Naomoto Iwagami, Munetaka Ueno, Kazunori Uemizu, Makoto
Suzuki, George L. Hashimoto, Takeshi Sakanoi, Yasumasa Kasaba, Ryosuke Nakamura, Takeshi
Imamura, Masato Nakamura, Tetsuya Fukuhara, Atsushi Yamazaki, Manabu Yamada, Venus’
clouds as inferred from the phase curves acquired by IR1 and IR2 on board Akatsuki, Icarus,
Volume 248, 1 March 2015, Pages 213–220, 2014.
(2) A. Yamazaki, F. Tsuchiya, T. Sakanoi, K. Uemizu, K. Yoshioka, G. Murakami, M. Kagitani, Y.
Kasaba, I. Yoshikawa, N. Terada, et al., Field-of-View Guiding Camera on the HISAKI (SPRINTA) Satellite, Space Science Reviews, November 2014, Volume 184, Issue 1-4, pp 259-274, 2014.
(3) Ichiro Yoshikawa, Kazuo Yoshioka, Go Murakami, Atsushi Yamazaki, Fuminori Tsuchiya,
Masato Kagitani, Takeshi Sakanoi, Naoki Terada, Tomoki Kimura, Masaki Kuwabara, et al.,Extreme Ultraviolet Radiation Measurement for Planetary Atmospheres/Magnetospheres from the
Earth-Orbiting Spacecraft (Extreme Ultraviolet Spectroscope for Exospheric Dynamics:
EXCEED), Space Science Reviews, November 2014, Volume 184, Issue 1-4, pp 237-258, 2014.
(4) K. Yoshioka, G. Murakami, A. Yamazaki, F. Tsuchiya, T. Kimura, M. Kagitani, T. Sakanoi, K.
Uemizu, Y. Kasaba, I. Yoshikawa, M. Fujimoto, Evidence for global electron transportation into
the jovian inner magnetosphere, Science, Vol. 345 no. 6204 pp. 1581-1584, 26 September 2014.
(5) Shohei Aoki Marco Giuranna, Yasumasa Kasaba, Hiromu Nakagawa, Giuseppe Sindoni, Anna
Geminale, Vittorio Formisano, Search for hydrogen peroxide in the Martian atmosphere by thePlanetary Fourier Spectrometer onboard Mars Express, Icarus, Volume 245, 1 January 2015,
Pages 177–183, 2014.

資料8-G(6) T.M. Sato, H. Sagawa, T. Kouyama, K. Mitsuyama, T. Satoh, S. Ohtsuki, M. Ueno, Y. Kasaba, M.
Nakamura, T. Imamura, Cloud top structure of Venus revealed by Subaru/COMICS mid-infrared
images, Icarus, Volume 243, 15 November 2014, Pages 386–399, 2014.
(7) Shun Imajo, Kiyohumi Yumoto, Teiji Uozumi, Hideaki Kawano, Shuji Abe, Akihiro Ikeda,
Kiyokazu Koga, Haruhisa Matsumoto, Takahiro Obara, Richard Marshall, Victor A Akulichev,
Ayman Mahrous, Adam Liedloff and Akimasa Yoshikawa1, Analysis of propagation delays ofcompressional Pi 2 waves between geosynchronous altitude and low latitudes, Earth, Planets andSpace, 66:20 doi:10.1186/1880-5981-66-20, 2014.
(8) Kazuo Shiokawa, Yu Yokoyama, Akimasa Ieda, Yoshizumi Miyoshi, Reiko Nomura, Sungeun
Lee, Naoki Sunagawa, Yukinaga Miyashita, Mitsunori Ozaki, Kazumasa Ishizaka, Satoshi
Yagitani, Ryuho Kataoka, Fuminori Tsuchiya, Ian Schofield and Martin Connors, Ground-based
ELF/VLF chorus observations at subauroral latitudes—VLF-CHAIN Campaign, Journal ofGeophysical Research: Space Physics, Volume 119, Issue 9, pages 7363–7379, September 2014
(9) Takeshi Kuroda, Alexander S. Medvedev, Paul Hartogh, Parameterization of radiative heating andcooling rates in the stratosphere of Jupiter, Icarus, Volume 242, 1 November 2014, Pages 149–157,
2014.
1.4. Report from the University of Electro-Communications(Keisuke Hosokawa, The University of Electro-Communications)=== Report from recent papers ===This paper reports simultaneous observations of ionospheric scintillation during an auroral substormthat were made using an all-sky full-color digital single-lens reflex (DSLR) camera (ASC) and a
Global Positioning System (GPS) ionospheric scintillation and total electron content monitor (GISTM)
in Tromsø (69.60 N, 19.20 E), Norway. On the night of November 19, 2009, a small substorm
occurred in northern Scandinavia. The ASC captured its temporal evolution from the beginning of thegrowth phase to the end of the recovery phase. The amplitude scintillation, as monitored by the S4index from the GISTM, did not increase in any substorm phase. By contrast, phase scintillation, as
measured by the σφ index, occurred when discrete auroral arcs appeared on the GPS signal path. In
particular, the phase scintillation was significantly enhanced for a few minutes immediately after the
onset of the expansion phase. During this period, bright and discrete auroral forms covered the entire
sky, which implies that structured precipitation on the scale of a few kilometers to a few tens ofkilometers dominated the electron density distribution in the E region. Such inhomogeneous ionization
structures probably produced significant changes in the refractive index and eventually resulted in theenhancement of the phase scintillation.
Reference
Keisuke Hosokawa, Yuichi Otsuka, Yasunobu Ogawa and Takuya Tsugawa, Observations of GPS
scintillation during an isolated auroral substorm, Progress in Earth and Planetary Science 2014 1:16.

1.5. Report from Electro Navigation Research Institute (ENRI)(Susumu Saito, ENRI)=== Report from recent papers ===(1) We investigated low-latitude ionospheric scintillation in Indonesia using two GPS receivers
installed at Bandung (107.6◦ E, 6.9◦ S; magnetic latitude 17.5◦ S) and Pontianak (109.3◦ E, 0.02◦
S; magnetic latitude 8.9◦ S). This study aimed to characterise climatological and directional
ionospheric scintillation occurrences, which are useful not only for the physics of ionospheric資料8-G

irregularities but also for practical use in GNSS (global navigation satellite system)- basednavigation. We used the deployed instrument’s amplitude scintillation (S4 index) data from 2009,2010, and 2011; the yearly SSN (sunspot-smoothed numbers) were 3.1, 16.5, and 55.9,
respectively. In summary, (1) scintillation occurrences in the post-sunset period (18:00–01:00 LT)
during equinox months (plasma bubble season) at the two sites can be ascribed to the plasma
bubble; (2) using directional anal- yses of the two sites, we found that the distribution of
scintillation occurrences is generally concentrated between the two sites, indicating the average
location of the EIA (equatorial ionization anomaly) crest; (3) scintillation occurrence
enhancements for the two sites in field-aligned directions are herein reported for the first time byground-based observation in a low-latitude region; (4) distribution of scintillation occurrences at
Pontianak are concentrated in the southern sky, especially in the southwest direction, which isvery likely associated with the plasma bubble tilted westward with increasing latitude; and (5)scintillation occurrence in the post-midnight period in the non-plasma-bubble season is the mostintriguing variable occurring between the two sites (i.e. post-midnight scintillations are observed
more at Bandung than Pontianak). Most of the post-midnight scintillations ob- served at Bandungare concentrated in the northern sky, with low elevation angles. This might be due to theamplitude of irregularities in certain directions, which may be effectively enhanced by backgrounddensity enhancement by the EIA and because satellite–receiver paths are longer in the EIA crest
region and in a field-aligned direction.
(2) The ionospheric delay gradient is an important parameter for the planning of ground-based
augmentation system (GBAS) in a region. When it is beyond the limit, the integrity and safety forlanding approach of CAT II/III may be com- promised. In order to maintain the availability andsafety requirement of the sys- tem, the ionospheric threat models have been developed in several
countries during the past few years. However, the ionospheric delay gradient associated withplasma bubble in low latitude region has not been studied well. In this work, we present someanalytical results of ionospheric delay gradient based on three GPS monitoring stations near
Suvarnabhumi airport in Thailand. The stations are located on the campus of King Mongkut’s
Institute of Technology Ladkrabang (13.7278°N, 100.7726°E), Stamford University (13.7356°N,
100.6612°E) and Suvarnabhumi airport (13.6945°N, 100.7608°E). The analyzed results on 1st
September 2011 show that the ionospheric delay gradient varies from -95.23 to 107.7 mm/km
during the occurrence of the plasma bubbles.
Reference(1) P. Abadi, S. Saito, and W. Srigutomo, Low-latitude scintillation occurrences around the equatorial
anomaly crest over Indonesia, Annales Geophysicae, 32, 7–17, 2014(2) S. Rungraengwajiake, P. Supnithi, S. Saito, N. Siansawasdi, and A. Saekow, Study of ionosphericdelay gradient based on GPS monitoring stations near Suvarnabhumi airport in Thailand, Air
Traffic Management and Systems, 193-204, Springer, 2014.

1.6. Report from Department of Geophysics, Kyoto Univerisy(Akinori Saito, Kyoto University)=== Report from recent papers ===Spaceborne imagers are able to observe the airglow structures with wide field of views regardless ofthe tropospheric condition that limits the observational time of the ground-based imagers. Concentric
wave structures of the O2 airglow in 762 nm wavelength were observed over North America on 1 June2013 from the International Space Station. This was the first observation in which the entire image ofthe structure was captured from space, and its spatial scale size was determined to be 1200 km radius

資料8-G

without assumptions. The apparent horizontal wavelength was 80 km, and the amplitude in theintensity was approximately 20% of the background intensity. The propagation velocity of thestructure was derived as 125 ± 62 m/s and atmospheric gravity waves were estimated to be generated
for 3.5 ± 1.7 h. Concentric structures observed in this event were interpreted to be generated by supercells that caused a tornado in its early phase.
Reference
Y. Akiya, A. Saito, T. Sakanoi, Y. Hozumi, A. Yamazaki, Y. Otsuka, M. Nishioka and T. Tsugawa,First spaceborne observation of the entire concentric airglow structure caused by troposphericdisturbance, Geophysical Research Letters, Volume 41, Issue 19, pages 6943–6948, 16 October 2014.

1.7. Report from Research Institute for Sustainable Humanosphere, Kyoto University (RISH)(Mamoru Yamamoto, Kyoto University)=== Report from recent papers ===(1) Total electron content (TEC) is an important parameter for revealing latitudinal ionosphericstructures, such as the equatorial ionization anomaly (EIA) in Southeast Asia. Understanding the
EIA is beneficial for studying equatorial spread F. To reveal the structures, the absolute TEC as afunction of latitude must be accurately determined. In early 2012, we expanded a GNU Radio
Beacon Receiver (GRBR) network to provide latitudinal coverage in the Thailand-Indonesia
sector. We employed the GRBR network to receive VHF and UHF signals from polar low-Earthorbit satellites. The TEC offset is an unknown parameter in the absolute TEC estimation process.
We propose a new technique based on the two-station method to estimate the offset for thelatitudinal TEC estimation, and it works better than the original method for a sparse network. The
TEC estimation system requires two iterations to minimize the root-mean-square error (RMSE).
Once the RMSE reaches the global minimum, the absolute TECs are estimated simultaneously
over five GRBR stations. GPS-TECs from local stations are used as the initial guess of the offset
estimation. The height of the ionospheric pierce point is determined from the ionosonde hmF2. As
a result, the latitudinal GRBR-TEC was successfully estimated from the polar orbit satellites. The
two EIA humps were clearly captured by the GRBR-TEC. The result was well verified with the
TEC reconstructed from the /NOFS density data and the ionosonde bottomside data. This is asignificant step showing that the GRBR is a useful tool for the study of low-latitude ionosphericfeatures.
(2) A GNU Radio Beacon Receiver (GRBR) system for total electron content (TEC) measurements
using 150 and 400?MHz transmissions from Low-Earth Orbiting Satellites (LEOS) is fabricated inhouse and made operational at Ahmedabad (23.04°N, 72.54°E geographic, dip latitude 17°N)
since May 2013. This system receives the 150 and 400?MHz transmissions from high-inclination
LEOS. The first few days of observations are presented in this work to bring out the efficacy of an
ensemble average method to convert the relative TECs to absolute TECs. This method is a
modified version of the differential Doppler-based method proposed by de Mendonca (1962) andsuitable even for ionospheric regions with large spatial gradients. Comparison of TECs derived
from a collocated GPS receiver shows that the absolute TECs estimated by this method arereliable estimates over regions with large spatial gradient. This method is useful even when only
one receiving station is available. The differences between these observations are discussed tobring out the importance of the spatial differences between the ionospheric pierce points of thesesatellites. A few examples of the latitudinal variation of TEC during different local times using
GRBR measurements are also presented, which demonstrates the potential of radio beacon

資料8-G

measurements in capturing the large-scale plasma transport processes in the low-latitude
ionosphere.
(3) Using numerical simulations, we investigated a method for calculating the spectral parametersfrom Doppler spectra collected by high-resolution wind profiler radars (WPRs). Because highresolution WPRs collect a huge amount of Doppler spectra, calculations must be simple and fast.
The proposed method has two steps. In the first step, the echo range (Recho), in which the
Doppler spectrum point with peak intensity is contained and all the smoothed Doppler spectrum
points have intensities that are greater than the noise intensity, was determined. For producing thesmoothed Doppler spectrum, a running average with equal weight (RA) or multi-taper method(MTM) was used. In the second step, the spectral parameters were calculated using the Doppler
spectrum points within Recho. By comparing the performance of the computation methods using
RA and MTM, we concluded that the computation method using RA is more suitable because it
has better estimation performance for small spectrum widths and the calculations are faster.
Estimation error of the spectral parameters depends on the determination accuracy of the Doppler
spectrum peak and Recho. Furthermore, for the case of a 512-point Doppler spectrum and 13point RA, the estimation errors tend to be independent of the signal-to-noise ratio (SNR) when thepeak level of the Doppler spectrum (pest) is ~8?dB or more greater than the noise intensity. For
pest of < ~8?dB, the estimation errors are well correlated to pest and the SNR. Therefore, thenumber of incoherent integration times should be determined by considering the SNR and pest.
References(1) Watthanasangmechai, K., M. Yamamoto, A. Saito, T. Tsugawa, T. Yokoyama, P. Supnithi, and C.
Y. Yatini (2014), Latitudinal GRBR-TEC estimation in Southeast Asia region based on the twostation method, Radio Sci., 49, 910-920, doi:10.1002/2013RS005347.
(2) Thampi, S. V., M. S. Bagiya, D. Chakrabarty, Y. B. Acharya, and M. Yamamoto (2014), An
ensemble average method to estimate absolute TEC using radio beacon-based differential phasemeasurements: Applicability to regions of large latitudinal gradients in plasma density, Radio Sci.,
49, doi:10.1002/2014RS005372.
(3) Tong Gan, Masayuki K. Yamamoto, Hiroyuki Hashiguchi, Hajime Okamoto and Mamoru
Yamamoto, Error estimation of spectral parameters for high-resolution wind and turbulencemeasurements by wind profiler radars, Radio Science, DOI: 10.1002/2013RS005369, in press,
2014.
2. Research meetings
International Workshop on Program of the Antarctic Syowa MST/IS RadarWorkshop date: March, 10-11, 2014.
Venue: Department of Earth and Planetary Science, Graduate School of Science, The University of
Tokyo
Workshop program:
http://polaris.nipr.ac.jp/~tutumi/PANSYmeeting201403/pansy_workshop_program201403.html
3. Publication list
Publications were listed in each section of research report.