COMMISSION G: Ionospheric Radio and Propagation (November 2004 – October 2007)

Edited by Takashi Maruyama

 

 


G1. Ionospheric Irregularities

 

G1.1. Equatorial Spread F and Plasma Bubble

Onset conditions and the evolution of plasma bubbles were studied in a multi-instrumental atmosphere observation program, CPEA (Coupling Processes in the Equatorial Atmosphere) [Fukao, 2006], including FAI (field-aligned irregularity) mode operation of the Equatorial Atmosphere Radar (EAR) at Kototabang in Sumatra Island, Indonesia [Yokoyama et al., 2004a, 2005a; Patra et al., 2005; Yokoyama and Fukao, 2006; Fukao et al., 2006; Ogawa et al., 2006a; Otsuka et al., 2006a]. EAR observations of FAI were compared with the plasma blobs detected by the ROCSAT-1 satellite [Yokoyama et al., 2007]. Ionospheric height variations were studied in connection with onset conditions of plasma bubbles [Saito and Maruyama, 2006, 2007] by using the ionospheric sounding data from the Southeast Asia Ionospheric Network (SEALION) [Maruyama et al., 2007]. Passive remote soundings of plasma bubbles and the related structure were conducted by receiving TV broadcasting signals at VHF from Southeast Asia countries [Nakata et al., 2004, 2005] and by receiving HF radio broadcasting signals from Australia [Maruyama and Kawamura, 2006]. A greatly developed plasma bubble extending over middle Japan, with an equatorial height of approximately 2500 km, was detected by a dense GPS receiver network over Japan, GEONET (GPS Earth Observation Network), [Ma and Maruyama, 2006]. A geomagnetically conjugate aspect of well-developed plasma bubbles was observed by all-sky imagers located in Japan and Australia and an OI 135.6-nm imager onboard the IMAGE satellite [Ogawa et al., 2005a].

 

G1.2. Sporadic E and Quasi-Periodic Echo

A multi-instrumental observation campaign, SEEK-2 (Sporadic E Experiment over Kyushu 2), for sporadic E study was conducted around Kyushu Island, southern Japan. This was a continuation of the SEEK campaign conducted in 1996. An outline of the observation is described by Yamamoto et al. [2005]. Two sounding rockets were launched on the night of 3 August 2002, which carried the Electric field Detector [Pfaff et al., 2005], the Impedance Probe [Wakabayashi et al., 2005; Wakabayashi and Ono, 2005], the Dual-Band Beacon transmitter [Bernhardt et al., 2005], Tri-Methyl Aluminum release experiment [Larsen et al., 2005], and other instruments. Ground-based facilities operated along with the rocket launches were two VHF coherent backscatter radars in Tanegashima close to the rocket launch site [Saito et al., 2005], the middle and upper atmosphere (MU) radar [Ogawa et al., 2005b], a rapid-run ionosonde [Maruyama et al., 2006], and an all sky imager [Onoma et al., 2005]. The observations obtained during the campaign were compared with numerical simulations [Yokoyama et al., 2005b].

Generation mechanisms responsible for E-region field-aligned irregularities and quasi-periodic (QP) echoes involved with neutral atmospheric dynamic were studied using VHF radars, all sky imagers, and other experiments [Ogawa et al., 2006b; Saito et al., 2006, 2007; Patra et al., 2007; Otsuka et al., 2007], in numerical simulations [Yokoyama et al., 2004b], and through theoretical approaches [Tsunoda et al., 2004; Haldoupis et al., 2005]. Global and seasonal distribution of sporadic E was depicted by applying an occultation technique to radio propagation data from the GPS satellites to the CHAMP satellite [Garcia-Fernandez and Tsuda, 2006]. A correlation between the sporadic metal layers and the sporadic E layer was studied with simultaneous lidar and ionosonde observations over Kototabang in Sumatra Island, Indonesia [Shibata et al., 2006].

 

G2. Ionospheric Disturbances

 

G2.1. Ionospheric Storm

Ionospheric disturbances caused by the prompt penetration of magnetospheric electric fields during major magnetic storms were demonstrated. [Mannucci et al., 2005; Tsurutani et al., 2006] and model calculations were compared with the observations [Pavlov et al., 2006; Pavlov and Fukao, 2007; Tsurutani et al., 2007]. Observations including magnetometer data from the Pacific sector were used to study the equatorial ionospheric electric field during a geomagnetic storm [Fejer et al., 2007]. GEONET and an ionosonde network along the Japan’s meridian were used to study geomagnetic storm effects on the ionosphere disturbances [Unnikrishnan et al., 2005; Kutiev et al., 2005, 2006, 2007; Maruyama, 2006; Maruyama and Nakamura, 2007], while observations in the East Asian and Brazilian sectors were compared for studying global characteristics of ionospheric storms [Sahai et al., 2005; Abdu et al., 2007]. Responses of the D-region electron density to geomagnetic storms were studied by analyzing tweek atmospherics in the ELF/VLF bands [Ohya et al., 2006].

 

G2.2 Direct Effect of Energetic Radiations

Increases in EUV and soft X-ray radiations associated with solar flares cause ionospheric disturbances. Characteristics of the ionospheric response to solar flares were studied from sudden increases in the total electron content (SITEC) [Tsugawa et al., 2006b, 2007], rapid thermospheric responses observed by the CHAMP satellite [Liu, H. et al., 2007b], and changes in the amplitude of VLF signals with short and long propagation distances [Todoroki et al., 2007]. An ionospheric disturbance caused by another energetic event, a cosmic gamma-ray burst, was detected by a riometer and other instruments [Maeda et al., 2005].

 

G2.3. Traveling Ionospheric Disturbances

Geomagnetic conjugate characteristics of traveling ionospheric disturbances were studied with simultaneous observations in Japan and Australia by using an all-sky airglow imager network [Shiokawa et al., 2005a] and GPS receiver networks over Japan (GEONET) and Australia [Tsugawa et al., 2006a]. Midlatitude ionospheric irregularities over Japan were statistically investigated in connection with medium scale TIDs (MSTIDs) detected by GEONET [Otsuka et al., 2006c]. Characteristics of MSTIDs were analyzed by using TEC data derived from the International GNSS Service (IGS) dataset [Kotake et al., 2006], GPS networks in Southern California [Kotake et al., 2007], and MU radar observations [Liu, J. -Y. et al., 2007]. A general circulation model was applied to studying TIDs [Fujiwara and Miyoshi, 2006], and a TID propagating southward during a major magnetic storm was compared with NCAR-TIEGCM calculations incorporated with the assimilative mapping of ionospheric electrodynamics (AMIE) [Shiokawa et al., 2007].

 

G2.4. Other Disturbances Associated with Magnetic Storm

Low-latitude aurora events in the northern sky of Japan associated with magnetic storms were compiled and 20 events were identified in the high solar activity period from 1999 to 2004 [Shiokawa et al., 2005b]. In the historical literature written in the 12–19th centuries, low-latitude aurora events were picked up and interpreted in the eyes of the modern science [Nakazawa et al., 2004]. Significant nocturnal enhancements in electron temperature in the topside ionosphere were found by the HINOTORI satellite measurements [Oyama, K. -I. et al., 2005]. An ionospheric radio absorption event associated with a great geomagnetic storm on 15-16 July 2000 was observed in the Brazilian geomagnetic anomaly region using an imaging riometer [Nishino et al., 2006].

 

G3. GPS Application to Ionosphere Study

Several new techniques were developed for ionospheric application of GPS signals. A technique for determination of GPS differential biases and an ionospheric tomography based on the artificial neural network technique was developed [Ma et al., 2005a, b]. A combined use of limb sounding data with that from ground-based GPS receiver and ionosonde networks improved the accuracy of an ionospheric tomography [Garcia-Fernandez et al., 2005]. For the purpose of space weather monitoring, a near real-time estimation procedure of TEC was developed based on the GEONET data service [Miyake, 2007]. An improvement of the accuracy of vertical TEC estimates was discussed for the oblate earth’s gravitational equipotential surface model [Hobigar et al., 2007].

 

G4. Ionospheric Structure and Models

 

G4.1. Ionospheric Structure

A far ultraviolet (FUV) imager onboard the IMAGE satellite revealed nighttime zonal structure of the low latitude ionosphere with the wave-number-4 feature [Sagawa et al., 2005; England et al., 2006; Immel et al., 2006]. An electron density discontinuity or additional layering of the low latitude F region, sometimes referred to as the F3 layer in the bottomside or to as an ionospheric ledge in the topside, were studied by using topside soundings by the EXOS-C and ISIS-2 satellites [Uemoto et al., 2004, 2006] and bottomside soundings from a meridional ionosonde network over Southeast Asia [Uemoto et al., 2007]. Chaotic behavior of ionospheric fluctuations was studied in various geophysical conditions using GPS TEC data [Unnikrishnan et al., 2006a, b].

A D-region electron density profile was obtained at a noon high-latitude by using an LF/MF radio receiver and a DC probe onboard a sounding rocket [Ishisaka et al., 2005].

 

G4.2. Ionospheric Models

Long-term databases of incoherent scatter radars including the MU radar at Shigaraki, Japan were used to create local empirical models to complement global models such as the International Reference Ionosphere (IRI) [Zhang et al., 2005, 2007]. Electron densities and temperatures obtained by satellite in-situ measurements [Liu, H. et al., 2007c; Bilitza et al., 2007] and vertical electron density profiles [Uemoto et al., 2007] were compared with IRI predictions for improvements of the model.

 

G5. Coupling with Atmosphere/Lithosphere

 

G5.1. Neutral Atmosphere-Ionosphere System

 

Airglow measurements near the equator over Kototabang in Sumatra Island, Indonesia revealed quasi-periodic southward moving waves in the thermosphere [Shiokawa et al., 2006a] and northward propagating front-like structure aligned in the east-west direction in the mesosphere [Shiokawa et al., 2006b]. Thermospheric winds at midlatitudes observed by the MU radar at Shigaraki, Japan were compared with numerical simulations [Balan et al., 2006; Lei et al., 2007]. Equatorial thermospheric zonal winds as measured by the CHAMP satellite were investigated and compared with theoretical and empirical models [Liu, H. et al., 2006]. Climatology of the equatorial mass anomaly (EMA) in the thermosphere was investigated using CHAMP measurements and a strong variation of the EMA with the season and solar flux level was found [Liu, H. et al., 2007a].

 

G5.2. Effect of Thunder Storm and Meteorological Phenomenon

 

Coordinated optical and electromagnetic (VLF/ELF/VHF) measurements of sprites, optical emissions in the mesosphere associated with thunderstorm activities, were conducted [Adachi et al., 2005; Matsudo et al., 2007]. Electrical properties of lightning discharges that play an essential role in the initiation and development of sprites were investigated [Ohkubo et al., 2005]. The ISUAL payload, space-based measurement of sprites for the first time, onboard the FORMOSAT-2 satellite was launched [Mende et al., 2005]. The electron energy and electric field were estimated from the spectral data, and kinetic processes involved with sprites were studied [Adachi et al., 2006]. It was numerically demonstrated that the time scale of charge removal by lighting is an essential parameter for the initiation of sprites [Hiraki and Fukunishi, 2006]. Numerical simulations were made to study the behavior of positive charges causing sprite halos using a particle model combined with a quasi-electrostatic model [Tong et al., 2005]. Midlatitude ionospheric Alfvén resonator (IAR) excitation due to electromagnetic waves radiated from lightning discharges was studied analytically and numerically [Surkov et al., 2005, 2006]. The intensity of the Schumann resonance, global electromagnetic oscillations, has been monitored at Moshiri, Japan and a good correlation was found between the global ground temperature and the Schumann resonance intensity [Sekiguchi et al., 2006]. Ionospheric DC electric fields and plasma density variations associated with meteorological phenomena such as tropical storms and typhoons were investigated [Sorokin et al., 2005].

 

G5.3. Earthquake Effect on the Ionosphere

 

Upper atmospheric perturbations stimulated by the great Sumatra earthquake on 26 December 2004 were detected as changes in the ionospheric total electron content by GPS receiver networks [Otsuka et al., 2006b; Heki et al., 2006; Liu, J.-Y. et al., 2006] and as geomagnetic pulsations generated through the dynamo action of an atmospheric pressure pulse [Iyemori et al., 2005]. The observed TEC disturbances were numerically modeled [Shinagawa et al., 2007]. A similar TEC disturbance generated by a volcano eruption in central Japan was detected by GEONET [Heki 2006].

A precursor of ionospheric perturbations to the Sumatra earthquake was found in subionospheric VLF propagation signals [Horie et al., 2007]. An anomalous effect on the Schumann resonance was detected associated with other large earthquakes. For one of those earthquakes, an anomaly appeared one week to a few days before the main shock [Hayakawa et al., 2005], and this anomaly was numerically modeled [Nickolaenko et al., 2006]. A subionospheric LF and VLF propagation anomaly caused by ionospheric disturbances [Maekawa et al., 2006; Yamauchi et al., 2007] and anomalous sporadic E layers [Sorokin et al., 2006a] were observed in prior to earthquakes; the effect was numerically modeled [Soloviev et al., 2006]. Various applications of the Schumann resonance to ionospheric studies including an earthquake effect were reviewed [Nickolaenko and Hayakawa, 2007]. An electrodynamic model was developed for strong DC electric-field formation in the ionosphere above typhoon and earthquake regions [Sorokin et al., 2006b].

 

G6. Polar Atmosphere-Ionosphere

 

The cosmic radio noise absorption (CNA) was measured at Poker Flat Research Range, Alaska and results were compared with the precipitating electron flux observed by the NOAA12 satellite [Tanaka et al., 2005]. An all-sky airglow imager at Resolute Bay, Canada revealed polar cap patches that drift anti-sunward during a period of the southward IMF condition [Hosokawa et al., 2006]. The ratio of the Lorentz force to the Joule heating rate terms in generating atmospheric gravity waves in the auroral electrojets was investigated using data from the European Incoherent Scatter (EISCAT) radar [Yuan et al., 2005]. Using observations by the EISCAT Svalbard radar at Longyearbyen and the EISCAT UHF radar at Tromsø, it was shown that the ion drag plays an important role in wind dynamics in the lower thermosphere [Tsuda et al., 2007]. The ion and neutral temperatures in the auroral region and in the polar cap were compared using two EISCAT radars, and agreement/disagreement with the MSISE-90 empirical model was studied [Maeda et al., 2005]. Vertical ion velocities in the lower ionosphere were investigated using data from the EISCAT Tromsø UHF radar under geomagnetically quiet conditions [Oyama, S. et al., 2005a]. A new beam configuration for monostatic incoherent scatter radar observation at high latitudes was developed to estimate the vertical component of the neutral wind velocity in the lower thermosphere and it was applied to the Sonderstrom IS radar, Greenland [Oyama, S. et al., 2005b]. Vertical winds in the thermosphere were measured with Fabry-Perot interferometers at Poker Flat Research Range and Eagle Observatory, Alaska during the Horizontal E region experiment campaign (HEX) [Ishii et al., 2004]. A numerical simulation of atmospheric dynamics near an auroral arc was conducted and it was found that interaction of local heating and strong horizontal flow could play an important role in generating vertical motion [Shinagawa and Oyama, 2006].

Among the backscattering from ionospheric irregularities, distinctive polar mesosphere summer echoes (PMSEs) were detected by the oblique incidence SuperDARN radars in the Arctic and Antarctic regions [Hosokawa et al., 2004, 2005; Ogawa et al., 2004]

A sounding rocket was launched from Andøya Rocket Range, Norway in the Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) campaign [Abe et al., 2006a], being coordinated with ground-based instruments. Atmospheric parameters were obtained along the rocket trajectory in a diffuse aurora; the electron density was increased by the auroral precipitation [Wakabayashi and Ono, 2006]; the electron temperature was remarkably high at 106-114 km altitudes [Abe et al., 2006b]; observed energy spectra of energetic electrons were compared with auroral images taken from the ground [Ogasawara et al., 2006]; the rotational temperature and the density of molecular nitrogen were measured and compared with the MSIS empirical model [Kurihara et al., 2006]; the neutral and electron temperatures measured by the DELTA rocket were compared with neutral/ion and electron temperatures observed by the EISCAT UHF radar [Nozawa et al., 2006].

 

References

 

Abdu, M. A., T. Maruyama, I. S. Batista, S. Saito, and M. Nakamura [2007], “Ionospheric responses to the October 2003 superstorm: Longitude/local time effects over equatorial low and middle latitudes,” J. Geophys. Res., Vol. 112, A10306, doi:10.1029/2006JA012228.

 

Abe,T., J. Kurihara, N. Iwagami, S. Nozawa, Y. Ogawa, R. Fujii, H. Hayakawa, and K-I. Oyama [2006a], “Dynamics and Energetics of the Lower Thermosphere in Aurora (DELTA) - Japanese sounding rocket campaign,” Earth Planets Space, Vol. 58, pp.1165-1171.

 

Abe,T., K. -I. Oyama, and A. Kadohata [2006b], “Electron temperature variation associated with the auroral energy input during the DELTA campaign,” Earth Planets Space, Vol. 58, pp.1139-1146.

 

Adachi, T., H. Fukunishi, Y. Takahashi, M. Sato, A. Ohokubo, and K. Yamamoto [2005], “Characteristics of thunderstorm systems producing winter sprites in Japan,” J. Geophys. Res., Vol. 110, D11203, doi:10.1029/2004JD005012.

 

Adachi, T., H. Fukunishi, Y. Takahashi, Y. Hiraki, R. -R. Hsu, H. T. Su, A. B. Chen, S. B. Mende, H. U. Frey, and L. C. Lee [2006], “Electric field transition between the diffuse and streamer regions of sprites estimated from ISUAL/array photometer measurements,” Geophys. Res. Lett., Vol. 33, L17803, doi:10.1029/2006GL026495.

 

Balan, N., S. Kawamura, T. Nakamura, M. Yamamoto, S. Fukao, W. L. Oliver, M. E. Hagan, A. D. Aylward, and H. Alleyne [2006], “Simultaneous mesosphere-lower thermosphere and thermospheric F region observations using middle and upper atmosphere radar,” J. Geophys. Res., Vol. 111, A10S17, doi:10.1029/2005JA011487.

 

Bernhardt, P. A., C. A. Selcher, C. Siefring, M. Wilkens, C. Compton, G. Bust, M. Yamamoto, S. Fukao, O. Takayuki, M. Wakabayashi, and H. Mori [2005], “Radio tomographic imaging of sporadic-E layers during SEEK-2,” Ann. Geophys., Vol. 23, pp.2357-2368.

Bilitza, D., V. Truhlik, P. Richards, T. Abe, and L. Triskova [2007], “Solar cycle variations of mid-latitude electron density and temperature: Satellite measurements and model calculations,” Adv. Space Res., Vol. 39, pp.779-789, doi:10.1016/j.asr.2006.11.022.

 

England, S. L., T. J. Immel, E. Sagawa, S. B. Henderson, M. E. Hagan, S. B. Mende, H. U. Frey, C. M. Swenson, and L. J. Paxton [2006], “Effect of atmospheric tides on the morphology of the quiet time, postsunset equatorial ionospheric anomaly,” J. Geophys. Res., Vol. 111, A10S19, doi:10.1029/2006JA011795.

 

Fejer, B. G., J. W. Jensen, T. Kikuchi, M. A. Abdu, and J. L. Chau [2007], “Equatorial ionospheric electric fields during the November 2004 magnetic storm,” J. Geophys. Res., Vol. 112, A10304, doi:10.1029/2007JA012376.

 

Fujiwara, H. and Y. Miyoshi [2006], “Characteristics of the large-scale traveling atmospheric disturbances during geomagnetically quiet and disturbed periods simulated by a whole atmosphere general circulation model,” Geophys. Res. Lett., Vol. 33, L20108, doi:10.1029/2006GL027103.

 

Fukao,S., T. Yokoyama, T. Tayama, M. Yamamoto, T. Maruyama, and S. Saito [2006], “Eastward traverse of equatorial plasma plumes observed with the Equatorial Atmosphere Radar in Indonesia,” Ann. Geophys., Vol. 24, pp.1411-1418.

 

Fukao, S. [2006], “Coupling Processes in the Equatorial Atmosphere (CPEA): A Project Overview,” J. Meteor. Soc. Japan, Vol. 84A, pp.1-18.

 

Garcia-Fernandez, M. and T. Tsuda [2006], “A global distribution of sporadic E events revealed by means of CHAMP-GPS occultations,” Earth Planets Space, Vol. 58, pp.33-36.

 

Garcia-Fernandez, M., A. Saito, J. M. Juan, and T. Tsuda [2005], “Three-dimensional estimation of electron density over Japan using the GEONET GPS network combined with SAC-C data and ionosonde measurements,” J. Geophys. Res., Vol. 110, A11304, doi:10.1029/2005JA011037.

 

Haldoupis, C., T. Ogawa, K. Schlegel, J. A. Koehler, and T. Ono [2005], “Is there a plasma density gradient role on the generation of short-scale Farley-Buneman waves?,” Ann. Geophys., Vol. 23, pp.3323-3337.


Hayakawa, M., K. Ohta, A. P. Nickolaenko, and Y. Ando [2005], “Anomalous effect in Schumann resonance phenomena observed in Japan, possibly associated with the Chi-chi earthquake in Taiwan,” Ann. Geophys., Vol. 23, pp.1335-1346.

Heki, K. [2006], “Explosion energy of the 2004 eruption of the Asama Volcano, central Japan, inferred from ionospheric disturbances,” Geophys. Res. Lett., Vol. 33, L14303, doi:10.1029/2006GL026249.

 

Heki, K., Y. Otsuka, N. Choosakul, N. Hemmakorn, T. Komolmis, and T. Maruyama [2006], “Detection of ruptures of Andaman fault segments in the 2004 great Sumatra earthquake with coseismic ionospheric disturbances,” J. Geophys. Res., Vol. 111, B09313, doi:10.1029/2005JB004202.

 

Hiraki, Y. and H. Fukunishi [2006], “Theoretical criterion of charge moment change by lightning for initiation of sprites,” J. Geophys. Res., Vol. 111, A11305, doi:10.1029/2006JA011729.

 

Hobiger, T., T. Kondo, Y. Koyama, R. Ichikawa, and R. Weber [2007], “Effect of the Earth's oblateness on the estimation of global vertical total electron content maps,” Geophys. Res. Lett., Vol. 34, L11113, doi:10.1029/2007GL029792.

 

Horie, T., T. Yamauchi, M. Yoshida, and M. Hayakawa [2007], “The wave-like structures of ionospheric perturbation associated with Sumatra earthquake of 26 December 2004, as revealed from VLF observation in Japan of NWC signals,” J. Atmos. Solar-Terr. Phys., Vol. 69, pp.1021-1028, doi:10.1016/j.jastp.2007.03.012.

 

Hosokawa, K., T. Ogawa, A. S. Yukimatu, N. Sato, and T. Iyemori [2004], “Statistics of Antarctic mesospheric echoes observed with the SuperDARN Syowa radar,” Geophys. Res. Lett., Vol. 31, L02106, doi:10.1029/2003GL018776.

 

Hosokawa, K., T. Ogawa, N. F. Arnold, M. Lester, N. Sato, and A. S. Yukimatu [2005], “Extraction of PMSE from SuperDARN data,” Geophys. Res. Lett., Vol. 32, L12801, doi:10.1029/2005GL022788.

 

Hosokawa, K., K. Shiokawa, Y. Otsuka, A. Nakajima, T. Ogawa, and J. D. Kelly [2006], “Estimating drift velocity of polar cap patches with all-sky airglow imager at Resolute Bay, Canada,” Geophys. Res. Lett., Vol. 33, L15111, doi:10.1029/2006GL026916.

 

Immel, T. J., E. Sagawa, S. L. England, S. B. Henderson, M. E. Hagan, S. B. Mende, H. U. Frey, C. M. Swenson, and L. J. Paxton [2006], “Control of equatorial ionospheric morphology by atmospheric tides,” Geophys. Res. Lett., Vol. 33, L15108, doi:10.1029/2006GL026161.

 

Ishii, M., M. Kubota, M. Conde, R. W. Smith, and M. Krynicki [2004], “Vertical wind distribution in the polar thermosphere during Horizontal E Region Experiment (HEX) campaign,” J. Geophys. Res., Vol. 109, A12311, doi:10.1029/2004JA010657.

 

Ishisaka, K., T. Okada, J. Hawkins, S. Murakami, T. Miyake, Y. Murayama, I. Nagano, and H. Matsumoto [2005], “Investigation of electron density profile in the lower ionosphere by SRP-4 rocket experiment,” Earth Planets Space, Vol. 57, pp.879-884.

 

Iyemori, T., M. Nose, D. Han, Y. Gao, M. Hashizume, N. Choosakul, H. Shinagawa, Y. Tanaka, M. Utsugi, A. Saito, H. McCreadie, Y. Odagi, and F. Yang [2005], “Geomagnetic pulsations caused by the Sumatra earthquake on December 26, 2004,” Geophys. Res. Lett., Vol. 32, L20807, doi:10.1029/2005GL024083.

 

Kotake, N., Y. Otsuka, T. Tsugawa, T. Ogawa, and A. Saito [2006], “Climatological study of GPS total electron content variations caused by medium-scale traveling ionospheric disturbances,” J. Geophys. Res., Vol. 111, A04306, doi:10.1029/2005JA011418.

 

Kotake, N., Y. Otsuka, T. Tsugawa, T. Ogawa, and A. Saito [2007], “Statistical study of medium-scale traveling ionospheric disturbances observed with the GPS networks in Southern California,” Earth Planets Space, Vol. 59, pp.95-102.

 

Kurihara, J., T. Abe, K. -I. Oyama, E. Griffin, M. Kosch, A. Aruliah, K. Kauristie, Y. Ogawa, S. Komada, and N. Iwagami [2006], “Observations of the lower thermospheric neutral temperature and density in the DELTA campaign,” Earth Planets Space, Vol. 58, pp.1123-1130.

 

Kutiev, I., S. Watanabe, Y. Otsuka, and A. Saito [2005], “Total electron content behavior over Japan during geomagnetic storms,” J. Geophys. Res., Vol. 110, A01308, doi:10.1029/2004JA010586.

 

Kutiev, I.., Y. Otsuka, A. Saito, and S. Watanabe [2006], “GPS observations of post-storm TEC enhancements at low latitudes,” Earth Planets Space, Vol. 58, pp.1479-1486.

 

Kutiev, I., Y. Otsuka, A. Saito, and T. Tsugawa [2007], “Low-latitude total electron content enhancement at low geomagnetic activity observed over Japan,” J. Geophys. Res., Vol. 112, A07306, doi:10.1029/2007JA012385.

 

Larsen, M. F., M. Yamamoto, S. Fukao, R. T. Tsunoda, and A. Saito [2005], “Observations of neutral winds, wind shears, and wave structure during a sporadic-E/QP event,” Ann. Geophys., Vol. 23, pp.2369-2375.

Lei, J., R. G. Roble, S. Kawamura, and S. Fukao [2007], “A simulation study of thermospheric neutral winds over the MU radar,” J. Geophys. Res., Vol. 112, A04303, doi:10.1029/2006JA012038.

 

Liu, H., H. Lühr, S. Watanabe, W. Köhler, V. Henize, and P. Visser [2006], “Zonal winds in the equatorial upper thermosphere: Decomposing the solar flux, geomagnetic activity, and seasonal dependencies,” J. Geophys. Res., Vol. 111, A07307, doi:10.1029/2005JA011415.

 

Liu, H., H. Lühr, and S. Watanabe [2007a], “Climatology of the equatorial thermospheric mass density anomaly,” J. Geophys. Res., Vol. 112, A05305, doi:10.1029/2006JA012199.

 

Liu, H., H. Lühr, S. Watanabe, W. Köhler, and C. Manoj [2007b], “Contrasting behavior of the thermosphere and ionosphere in response to the 28 October 2003 solar flare,” J. Geophys. Res., Vol. 112, A07305, doi:10.1029/2007JA012313.

 

Liu, H., C. Stolle, S. Watanabe, T. Abe, M. Rother, and D. L. Cooke [2007c], “Evaluation of the IRI model using CHAMP observations in polar and equatorial regions,” Adv. Space Res., Vol. 39, pp.904-909, doi:10.1016/j.asr.2006.08.006.

 

Liu, J. -Y., Y. -B. Tsai, K. -F. Ma, Y. -I. Chen, H. -F. Tsai, C. -H. Lin, M. Kamogawa, and C. -P. Lee [2006], “Ionospheric GPS total electron content (TEC) disturbances triggered by the 26 December 2004 Indian Ocean tsunami,” J. Geophys. Res., Vol. 111, A05303, doi:10.1029/2005JA011200.

 

Liu, J. -Y., C. C. Hsiao, C. H. Liu, M. Yamamoto, S. Fukao, H. Y. Lue, and F. S. Kuo [2007], “Vertical group and phase velocities of ionospheric waves derived from the MU radar,” Radio Sci., Vol. 42, RS4014, doi:10.1029/2005RS003435.

 

Ma, G. and T. Maruyama [2006], “A super bubble detected by dense GPS network at East Asian longitudes,” Geophys. Res. Lett., Vol. 33, L21103, doi:10.1029/2006GL027512.

 

Ma, X. F., T. Maruyama, G. Ma, and T. Takeda [2005a], “Determination of GPS receiver differential biases by neural network parameter estimation method,” Radio Sci., Vol. 40, RS1002, doi:10.1029/2004RS003072.

 

Ma, X. F., T. Maruyama, G. Ma, and T. Takeda [2005b], “Three-dimensional ionospheric tomography using observation data of GPS ground receivers and ionosonde by neural network,” J. Geophys. Res., Vol. 110, A05308, doi:10.1029/2004JA010797.

 

Maeda, K., I. Tomizawa, T. F. Shibata, N. Tokimasa, A. Saito, and T. Maruyama [2005], “Ionospheric effects of the cosmic gamma ray burst of 29 March 2003,” Geophys. Res. Lett., Vol. 32, L18807, doi:10.1029/2005GL023525.

 

Maeda, S., S. Nozawa, Y. Ogawa, and H. Fujiwara [2005], “Comparative study of the high-latitude E region ion and neutral temperatures in the polar cap and the auroral region derived from the EISCAT radar observations,” J. Geophys. Res., Vol. 110, A08301, doi:10.1029/2004JA010893.


Maekawa, S., T. Horie, T. Yamauchi, T. Sawaya, M. Ishikawa, M. Hayakawa, and H. Sasaki [2006], “A statistical study on the effect of earthquakes on the ionosphere, based on the subionospheric LF propagation data in Japan,” Ann. Geophys., Vol. 24, pp.2219-2225.

Mannucci, A. J., B. T. Tsurutani, B. A. Iijima, A. Komjathy, A. Saito, W. D. Gonzalez, F. L. Guarnieri, J. U. Kozyra, and R. Skoug [2005], “Dayside global ionospheric response to the major interplanetary events of October 29–30, 2003 “Halloween Storms”,” Geophys. Res. Lett., Vol. 32, L12S02, doi:10.1029/2004GL021467.

 

Maruyama, T. [2006], “Extreme enhancement in total electron content after sunset on 8 November 2004 and its connection with storm enhanced density,” Geophys. Res. Lett., Vol. 33, L20111, doi:10.1029/2006GL027367.

 

Maruyama, T. and M. Kawamura [2006], “Equatorial ionospheric disturbance observed through a transequatorial HF propagation experiment,” Ann. Geophys., Vol. 24, pp.1401-1409.

Maruyama, T. and M. Nakamura [2007], “Conditions for intense ionospheric storms expanding to lower midlatitudes,” J. Geophys. Res., Vol. 112, A05310, doi:10.1029/2006JA012226.

 

Maruyama, T., S. Saito, M. Yamamoto, and S. Fukao [2006], “Simultaneous observation of sporadic E with a rapid-run ionosonde and VHF coherent backscatter radar,” Ann. Geophys., Vol. 24, pp.153-162.

Maruyama, T., M. Kawamura, S. Saito, K. Nozaki, H. Kato, N. Hemmakorn, T. Boonchuk, T. Komolmis, and C. Ha Duyen [2007], “Low latitude ionosphere-thermosphere dynamics studies with inosonde chain in Southeast Asia,” Ann. Geophys., Vol. 25, pp.1569-1577.

 

Matsudo, Y., T. Suzuki, M. Hayakawa, K. Yamashita, Y. Ando, K. Michimoto, and V. Korepanov [2007], “Characteristics of Japanese winter sprites and their parent lightning as estimated by VHF lightning and ELF transients,” J. Atmos. Solar-Terr. Phys., Vol. 69, pp.1431-1446, doi:10.1016/j.jastp.2007.05.002.

 

Mende, S. B., H. U. Frey, R. R. Hsu, H. T. Su, A. B. Chen, L. C. Lee, D. D. Sentman, Y. Takahashi, and H. Fukunishi [2005], “D region ionization by lightning-induced electromagnetic pulses,” J. Geophys. Res., Vol. 110, A11312, doi:10.1029/2005JA011064.

 

Miyake, W. [2007], “Prompt derivation of TEC from GEONET data for space weather monitoring in Japan,” J. Atmos. Solar-Terr. Phys., Vol. 69, Pages 803-816 doi:10.1016/j.jastp.2007.02.006.

 

Nakata, H., Y. Akaike, Y. Otsuka, T. Takano, S. Ujigawa, and I. Nagashima [2004], “Ray-tracing calculation of VHF radio waves scattered by field-aligned irregularities associated with equatorial plasma bubbles,” IEEJ Trans. FM, Vol. 124, pp.1253-1254.

 

Nakata, H., I. Nagashima, K. Sakata, Y. Otsuka, Y. Akaike, T. Takano, S. Shimakura, K. Shiokawa, and T. Ogawa [2005], “Observations of equatorial plasma bubbles using broadcast VHF radio waves,” Geophys. Res. Lett., Vol. 32, L17110, doi:10.1029/2005GL023243.

 

Nakazawa, Y., T. Okada, and K. Shiokawa [2004], “Understanding the “SEKKI” phenomena in Japanese historical literatures based on the modern science of low-latitude aurora,” Earth Planets Space, Vol. 56, pp.e41-e44.


Nickolaenko, A. P., M. Hayakawa, M. Sekiguchi, Y. Ando, and K. Ohta [2006], “Model modifications in Schumann resonance intensity caused by a localized ionosphere disturbance over the earthquake epicenter,” Ann. Geophys., Vol. 24, pp.567-575.


Nickolaenko, A. P. and M. Hayakawa [2007], “Recent studies of Schumann resonance and ELF transients,” J. Atmos. Electr., Vol. 27, pp.19-39.

 

Nishino, M., K. Makita, K. Yumoto, Y. Miyoshi, N. J. Schuch, and M. A. Abdu [2006], “Energetic particle precipitation in the Brazilian geomagnetic anomaly during the “Bastille Day storm” of July 2000,” Earth Planets Space, Vol. 58, pp.607-616.

 

Nozawa, S., Y. Ogawa, A. Brekke, T. Tsuda, C. M. Hall, H. Miyaoka, J. Kurihara, T. Abe, and R. Fujii [2006], “EISCAT observational results during the DELTA campaign,” Earth Planets Space, Vol. 58, pp.1183-1191.

 

Ogasawara, K., K. Asamura, T. Takashima, Y. Saito, and T. Mukai [2006], “Rocket observation of energetic electrons in the low-altitude auroral ionosphere during the DELTA campaign,” Earth Planets Space, Vol. 58, pp.1155-1163.

 

Ogawa, T., S. Nozawa, M. Tsutsumi, N. F. Arnold, N. Nishitani, N. Sato, and A. S. Yukimatu [2004], “Arctic and Antarctic polar mesosphere summer echoes observed with oblique incidence HF radars: Analysis using simultaneous MF and VHF radar data,” Ann. Geophys., Vol. 22, pp.4049-4059.

 

Ogawa, T., E. Sagawa, Y. Otsuka, K. Shiokawa, T. J. Immel, S. B. Mende, and P. Wilkinson [2005a], “Simultaneous ground- and satellite-based airglow observations of geomagnetic conjugate plasma bubbles in the equatorial anomaly,” Earth Planets Space, Vol. 57, pp.385-392.

 

Ogawa, T., Y. Otsuka, F. Onoma, K. Shiokawa, and M. Yamamoto [2005b], “The first coordinated observations of mid-latitude E-region quasi-periodic radar echoes and lower thermospheric 557.7-nm airglow,” Ann. Geophys., Vol. 23, pp.2391-2399.

 

Ogawa, T., Y. Otsuka, K. Shiokawa, A. Saito, and M. Nishioka [2006a], “Ionospheric disturbances over Indonesia and their possible association with atmospheric gravity waves from the troposphere,” J. Meteor. Soc. Japan, Vol. 84A, pp.327-342.

 

Ogawa, T., Y. Otsuka, and M. Yamamoto [2006b], “Characteristics and implications of Doppler spectra of E region quasi-periodic echoes observed by the multibeam middle and upper atmosphere radar,” J. Geophys. Res., Vol. 111, A05309, doi:10.1029/2005JA011335.

 

Ohkubo, A., H. Fukunishi, Y. Takahashi, and T. Adachi [2005], “VLF/ELF sferics evidence for in-cloud discharge activity producing sprites,” Geophys. Res. Lett., Vol. 32, L04812, doi:10.1029/2004GL021943.

 

Ohya, H., M. Nishino, Y. Murayama, K. Igarashi, and A. Saito [2006], “Using tweek atmospherics to measure the response of the low-middle latitude D-region ionosphere to a magnetic storm,” J. Atmos. Solar-Terr. Phys., Vol. 68, pp.697-709, doi:10.1016/j.jastp.2005.10.014.


Onoma, F., Y. Otsuka, K. Shiokawa, T. Ogawa, M. Yamamoto, S. Fukao, and S. Saito [2005], “Relationship between propagation direction of gravity waves in OH and OI airglow images and VHF radar echo occurrence during the SEEK-2 campaign,” Ann. Geophys., Vol. 23, pp.2385-2390.


Otsuka, Y., K. Shiokawa, and T. Ogawa [2006a], “Equatorial ionospheric scintillations and zonal irregularity drifts observed with closely-spaced GPS receivers in Indonesia,” J. Meteor. Soc. Japan, Vol. 84A, pp. 343-351.

 

Otsuka, Y., N. Kotake, T. Tsugawa, K. Shiokawa, T. Ogawa, Effendy, S. Saito, M. Kawamura, T. Maruyama, N. Hemmakorn, and T. Komolmis [2006b], “GPS detection of total electron content variations over Indonesia and Thailand following the 26 December 2004 earthquake,” Earth Planets Space, Vol. 58, pp.159-165.

 

Otsuka, Y., T. Aramaki, T. Ogawa, and A. Saito [2006c], “A statistical study of ionospheric irregularities observed with a GPS network in Japan,” in Corotating Solar Wind Streams and Recurrent Geomagnetic Activity, Geophys. Monogr., Amer. Geophys. Union, pp.271-281.

 

Otsuka, Y., F. Onoma, K. Shiokawa, T. Ogawa, M. Yamamoto, and S. Fukao [2007], “Simultaneous observations of nighttime medium-scale traveling ionospheric disturbances and E region field-aligned irregularities at midlatitude,” J. Geophys. Res., Vol. 112, A06317, doi:10.1029/2005JA011548.

 

Oyama, K. -I., D. R. Lakshmi, I. Kutiev, and M. A. Abdu [2005], “Low latitude Ne and Te variations at 600 km during 1 March 1982 storm from HINOTORI satellite,” Earth Planets Space, Vol. 57, pp.871-878.

 

Oyama, S., B. J. Watkins, S. Nozawa, S. Maeda, and M. Conde [2005a], “Vertical ion motion observed with incoherent scatter radars in the polar lower ionosphere,” J. Geophys. Res., Vol. 110, A04302, doi:10.1029/2004JA010705.

 

Oyama, S., B. J. Watkins, S. Maeda, and J. Watermann [2005b], “Application of a new beam configuration to estimate lower thermospheric vertical velocities at high latitudes with monostatic incoherent scatter radars,” Radio Sci., Vol. 40, RS4005, doi:10.1029/2004RS003205.  

 

Patra, A. K., T. Yokoyama, M. Yamamoto, S. Saito, T. Maruyama, and S. Fukao [2005], “Disruption of E region echoes observed by the EAR during the development phase of equatorial spread F: A manifestation of electrostatic field coupling,” Geophys. Res. Lett., Vol. 32, L17104, doi:10.1029/2005GL022868.

 

Patra, A. K., T. Yokoyama, M. Yamamoto, T. Nakamura, T. Tsuda, and S. Fukao [2007], “Lower E region field-aligned irregularities studied using the Equatorial Atmosphere Radar and meteor radar in Indonesia,” J. Geophys. Res., Vol. 112, A01301, doi:10.1029/2006JA011825.

 

Pavlov,  A. V. and S. Fukao [2007], “The ionospheric F2-region at low geomagnetic latitudes during the geomagnetic storms of 22–26 April 1990: Comparison of observed and modeled response,” J. Atmos. Solar-Terr. Phys., Vol. 69, pp.835-859, doi:10.1016/j.jastp.2007.01.006.

 

Pavlov, A. V., S. Fukao, and S. Kawamura [2006], “A modeling study of ionospheric F2-region storm effects at low geomagnetic latitudes during 17-22 March 1990,” Ann. Geophys., Vol. 24, pp.915-940.

Pfaff, R., H. Freudenreich, T. Yokoyama, M. Yamamoto, S. Fukao, H. Mori, S. Ohtsuki, and N. Iwagami [2005], “Electric field measurements of DC and long wavelength structures associated with sporadic-E layers and QP radar echoes,” Ann. Geophys., Vol. 23, pp.2319-2334.

Sagawa, E., T. J. Immel, H. U. Frey, and S. B. Mende [2005], “Longitudinal structure of the equatorial anomaly in the nighttime ionosphere observed by IMAGE/FUV,” J. Geophys. Res., Vol. 110, A11302, doi:10.1029/2004JA010848.

 

Sahai Y., P. R. Fagundes, F. Becker-Guedes, M. J. A. Bolzan, J. R. Abalde, V. G. Pillat, R. de Jesus, W. L. C. Lima, G. Crowley, K. Shiokawa, J. W. MacDougall, H. T. Lan, K. Igarashi, and J. A. Bittencourt [2005], “Effects of the major geomagnetic storms of October 2003 on the equatorial and low-latitude F region in two longitudinal sectors,” J. Geophys. Res., Vol. 110, A12S91, doi:10.1029/2004JA010999.

 

Saito, S. and T. Maruyama [2006], “Ionospheric height variations observed by ionosondes along magnetic meridian and plasma bubble onsets,” Ann. Geophys., Vol. 24, pp.2991-2996.

Saito, S. and T. Maruyama [2007], “Large-scale longitudinal variation in ionospheric height and equatorial spread F occurrences observed by ionosondes,” Geophys. Res. Lett., Vol. 34, L16109, doi:10.1029/2007GL030618.

 

Saito, S., M. Yamamoto, S. Fukao, M. Marumoto, and R. T. Tsunoda [2005], “Radar observations of field-aligned plasma irregularities in the SEEK-2 campaign,” Ann. Geophys., Vol. 23, pp.2307-2318.

Saito, S., M. Yamamoto, H. Hashiguchi, and A. Maegawa [2006], “Observation of three-dimensional structures of quasi-periodic echoes associated with mid-latitude sporadic-E layers by MU radar ultra-multi-channel system,” Geophys. Res. Lett., Vol. 33, L14109, doi:10.1029/2005GL025526.

 

Saito, S., M. Yamamoto, H. Hashiguchi, A. Maegawa, and A. Saito [2007], “Observational evidence of coupling between quasi-periodic echoes and medium scale traveling ionospheric disturbances,” Ann. Geophys., Vol. 25, pp.2185-2194.

 

Sekiguchi, M., M. Hayakawa, A. P. Nickolaenko, and Y. Hobara [2006], “Evidence on a link between the intensity of Schumann resonance and global surface temperature,” Ann. Geophys., Vol. 24, pp.1809-1817.

 

Shibata, Y., C. Nagasawa, M. Abo, T. Maruyama, S. Saito, and T. Nakamura [2006], “Lidar observations of sporadic Fe and Na layers in the mesopause region over equator,” J. Meteor. Soc. Japan, Vol. 84A, pp.317-325.

 

Shinagawa, H. and S. Oyama [2006], “A two-dimensional simulation of thermospheric vertical winds in the vicinity of an auroral arc,” Earth Planets Space, Vol. 58, pp.1173-1181.

 

Shinagawa, H., T. Iyemori, S. Saito, and T. Maruyama [2007], “A numerical simulation of ionospheric and atmospheric variations associated with the Sumatra earthquake on December 26, 2004,” Earth Planets Space, Vol. 59, pp.1015-1026.

 

Shiokawa, K., Y. Otsuka, T. Tsugawa, T. Ogawa, A. Saito, K. Ohshima, M. Kubota, T. Maruyama, T. Nakamura, M. Yamamoto and P. Wilkinson [2005a], “Geomagnetic conjugate observation of nighttime medium-scale and large-scale traveling ionospheric disturbances: FRONT3 campaign,” J. Geophys. Res., Vol. 110, A05303, doi:10.1029/2004JA010845.

 

Shiokawa, K., T. Ogawa, and Y. Kamide [2005b], “Low-latitude auroras observed in Japan: 1999-2004,” J. Geophys. Res., Vol. 110, A05202, doi:10.1029/2004JA010706.

 

Shiokawa, K., Y. Otsuka, and T. Ogawa [2006a], “Quasiperiodic southward moving waves in 630-nm airglow images in the equatorial thermosphere,” J. Geophys. Res., Vol. 111, A06301, doi:10.1029/2005JA011406.

 

Shiokawa, K., S. Suzuki, Y. Otsuka, T. Ogawa, T. Nakamura, M. G. Mlynczak, and J. M. Russell III [2006b], “A multi-instrument measurement of a mesospheric front-like structure at the equator,” J. Meteor. Soc. Japan, Vol. 84A, pp.305-316.

 

Shiokawa, K., G. Lu, Y. Otsuka, T. Ogawa, M. Yamamoto, N. Nishitani, and N. Sato [2007], “Ground observation and AMIE-TIEGCM modeling of a storm-time traveling ionospheric disturbance,” J. Geophys. Res., Vol. 112, A05308, doi:10.1029/2006JA011772.

 

Soloviev, O. V., M. Hayakawa, and O. A. Molchanov [2006], “Seismo-electromagnetic phenomenon in terms of 3D vector problem of subionospheric radio wave propagation across the solar terminator,” Phys. Chem. Earth, Vol. 31, pp.428-436.

 

Sorokin, V. M., N. V. Isaev, A. K. Yaschenko, V. M. Chmyrev, and M. Hayakawa [2005], “Strong DC electric field formation in the low latitude ionosphere over typhoons,” J. Atmos. Solar-Terr. Phys., Vol. 67, pp.1269-1279.

 

Sorokin, V. M., A. K. Yaschenko, and M. Hayakawa [2006a], “Formation mechanism of the lower-ionospheric disturbances by the atmosphere electric current over a seismic region,” J. Atmos. Solar-Terr. Phys., Vol. 68, pp.1260-1268, doi:10.1016/j.jastp.2006.03.005.

 

Sorokin, V. M., A. K. Yaschenko, V. M. Chmyrev and M. Hayakawa [2006b], “DC electric field formation in the mid-latitude ionosphere over typhoon and earthquake regions,” Phys. Chem. Earth, Vol. 31, pp.454-461.

 

Surkov, V. V., O. A. Molchanov, M. Hayakawa, and E. N. Fedorov [2005], “Excitation of the ionospheric resonance cavity by thunderstorms,” J. Geophys. Res., Vol. 110, A04308, doi:10.1029/2004JA010850.

 

Surkov, V. V., M. Hayakawa, A. Y. Schekotov, E. N. Fedorov, and O. A. Molchanov [2006], “Ionospheric Alfvén resonator excitation due to nearby thunderstorms,” J. Geophys. Res., Vol. 111, A01303, doi:10.1029/2005JA011320.

 

Tanaka, Y.-M., M. Ishii, Y. Murayama, M. Kubota, H. Mori, M.-Y. Yamamoto, A. Kadokura, D. Lummerzheim, J. Desrochers, and D. S. Evans [2005], “Comparison between CNA and energetic electron precipitation: simultaneous observation by Poker Flat imaging riometer and NOAA satellite,” Ann. Geophys., Vol. 23, pp.1555-1563.

Todoroki, Y., S. Maekawa, T. Yamauchi, T. Horie, and M. Hayakawa [2007], “Solar flare induced D region perturbation in the ionosphere, as revealed from a short-distance VLF propagation path,” Geophys. Res. Lett., Vol. 34, L03103, doi:10.1029/2006GL028087.


Tong, L., Y. Hiraki, K. Nanbu, and H. Fukunishi [2005], “Release of positive charges producing sprite halos,” J. Atmos. Solar-Terr. Phys., Vol. 67, pp.829-838.

 

Tsuda, T. T., S. Nozawa, A. Brekke, Y. Ogawa, T. Motoba, R. Roble, and R. Fujii [2007], “An ion drag contribution to the lower thermospheric wind in the summer polar region,” J. Geophys. Res., Vol. 112, A06319, doi:10.1029/2006JA011785.

 

Tsugawa, T., K. Shiokawa, Y. Otsuka, T. Ogawa, A. Saito, and M. Nishioka [2006a], “Geomagnetic conjugate observations of large-scale traveling ionospheric disturbances using GPS networks in Japan and Australia,” J. Geophys. Res., Vol. 111, A02302, doi:10.1029/2005JA011300.

 

Tsugawa, T., T. Sadakane, J. Sato, Y. Otsuka, T. Ogawa, K. Shiokawa, and A. Saito [2006b], “Summer-winter hemispheric asymmetry of sudden increase in ionospheric total electron content induced by solar flares: A role of O/N2 ratio,” J. Geophys. Res., Vol. 111, A11316, doi:10.1029/2006JA011951.

 

Tsugawa, T., S.-R. Zhang, A. J. Coster, Y. Otsuka, J. Sato, A. Saito, Y. Zhang, and L. J. Paxton [2007], “Summer-winter hemispheric asymmetry of the sudden increase in ionospheric total electron content and of the O/N2 ratio: Solar activity dependence,” J. Geophys. Res., Vol. 112, A08301, doi:10.1029/2007JA012415.

 

Tsunoda, R. T., R. B. Cosgrove, and T. Ogawa [2004], “Azimuth-dependent Es layer instability: A missing link found,” J. Geophys. Res., Vol. 109, A12303, doi:10.1029/2004JA010597.

 

Tsurutani, B. T., F. L. Guarnieri, T. Fuller-Rowell, A. J. Mannucci, B. Iijima, W. D. Gonzalez, D. L. Judge, P. Gangopadhyay, A. Saito, T. Tsuda, O. P. Verkhoglyadova, and G. A. Zambon [2006], “Extreme solar EUV flares and ICMEs and resultant extreme ionospheric effects: Comparison of the Halloween 2003 and the Bastille Day events,” Radio Sci., Vol. 41, RS5S07, doi:10.1029/2005RS003331.

 

Tsurutani, B. T., O. P. Verkhoglyadova, A. J. Mannucci, T. Araki, A. Sato, T. Tsuda, and K. Yumoto [2007], “Oxygen ion uplift and satellite drag effects during the 30 October 2003 daytime superfountain event,” Ann. Geophys., Vol. 25, pp.569-574.

 

Uemoto, J., T. Ono, A. Kumamoto, and M. Iizima [2004], “Ionization ledge structures observed in the equatorial anomaly region by using PPS system on-board the Ohzora (EXOS-C) satellite,” Earth Planets Space, Vol. 56, pp.e21-e24.

 

Uemoto, J., T. Ono, A. Kumamoto, and M. Iizima [2006], “Statistical analysis of the ionization ledge in the equatorial ionosphere observed from topside sounder satellites,” J. Atmos. Solar-Terr. Phys., Vol. 68, pp.1340-1351, doi:10.1016/j.jastp.2006.05.015.

 

Uemoto, J., T. Ono, T. Maruyama, S. Saito, M. Iizima, and A. Kumamoto [2007], “Magnetic conjugate observation of the F3 layer using the SEALION ionosonde network,” Geophys. Res. Lett., Vol. 34, L02110, doi:10.1029/2006GL028783.

 

Uemoto, J., T. Ono, A. Kumamoto, and M. Iizima [2007], “Comparison of the IRI 2001 model with electron density profiles observed from topside sounder on-board the Ohzora (EXOS-C) and the Akebono (EXOS-D) satellites,” Adv. Space Res., Vol. 39, pp.750-754, doi:10.1016/j.asr.2006.10.019.

 

Unnikrishnan, K., A. Saito, Y. Otsuka, M. Yamamoto, and S. Fukao [2005], “Transition region of TEC enhancement phenomena during geomagnetically disturbed periods at mid-latitudes,” Ann. Geophys., Vol. 23, pp.3439-3450.

Unnikrishnan, K., A. Saito, and S. Fukao [2006a], “Differences in magnetic storm and quiet ionospheric deterministic chaotic behavior: GPS total electron content analyses,” J. Geophys. Res., Vol. 111, A06304, doi:10.1029/2005JA011311.


Unnikrishnan, K., A. Saito, and S. Fukao [2006b], “Differences in daytime and nighttime ionospheric deterministic chaotic behavior: GPS total electron content analyses,” J. Geophys. Res., Vol. 111, A07310, doi:10.1029/2005JA011313.

 

Wakabayashi, M. and T. Ono [2005], “Multi-layer structure of mid-latitude sporadic-E observed during the SEEK-2 campaign,” Ann. Geophys., Vol. 23, pp.2347-2355.

 

Wakabayashi, M. and T. Ono [2006], “Electron density measurement under the influence of auroral precipitation and electron beam injection during the DELTA campaign,” Earth Planets Space, Vol. 58, pp.1147-1154.

Wakabayashi, M., T. Ono, H. Mori, and P. A. Bernhardt [2005], “Electron density and plasma waves in mid-latitude sporadic-E layer observed during the SEEK-2 campaign,” Ann. Geophys., Vol. 23, pp.2335-2345.

 

Yamamoto, M., S. Fukao, R. T. Tsunoda, R. Pfaff, and H. Hayakawa [2005], “SEEK-2 (Sporadic-E Experiment over Kyushu 2) − Project outline, and significance,” Ann. Geophys., Vol. 23, pp.2295-2305.

Yamauchi, T., S. Maekawa, T. Horie, M. Hayakawa, and O. Soloviev [2007], “Subionospheric VLF/LF monitoring of ionospheric perturbations for the 2004 Mid-Niigata earthquake and their structure and dynamics,” J. Atmos. Solar-Terr. Phys., Vol. 69, pp.793-802, doi:10.1016/j.jastp.2007.02.002.

 

Yokoyama, T., S. Fukao, and M. Yamamoto [2004a], “Relationship of the onset of equatorial F region irregularities with the sunset terminator observed with the Equatorial Atmosphere Radar,” Geophys. Res. Lett., Vol. 31, L24804, doi:10.1029/2004GL021529.

 

Yokoyama, T., T. Horinouchi, M. Yamamoto, and S. Fukao [2004b], “Modulation of the midlatitude ionospheric E region by atmospheric gravity waves through polarization electric field,” J. Geophys. Res., Vol. 109, A12307, doi:10.1029/2004JA010508.

 

Yokoyama, T., A. K. Patra, S. Fukao, and M. Yamamoto [2005a], “Ionospheric irregularities in the low-latitude valley region observed with the Equatorial Atmosphere Radar,” J. Geophys. Res., Vol. 110, A10304, doi:10.1029/2005JA011208.

 

Yokoyama, T., M. Yamamoto, S. Fukao, T. Takahashi, and M. Tanaka [2005b], “Numerical simulation of mid-latitude ionospheric E-region based on SEEK and SEEK-2 observations,” Ann. Geophys., Vol. 23, pp.2377-2384.

Yokoyama, T., and S. Fukao [2006], “Upwelling backscatter plumes in growth phase of equatorial spread F observed with the Equatorial Atmosphere Radar,” Geophys. Res. Lett., Vol. 33, L08104, doi:10.1029/2006GL025680.

 

Yokoyama, T., S. -Y. Su, and S. Fukao [2007], “Plasma blobs and irregularities concurrently observed by ROCSAT-1 and Equatorial Atmosphere Radar,” J. Geophys. Res., Vol. 112, A05311, doi:10.1029/2006JA012044.

 

Yuan, Z., R. Fujii, S. Nozawa, and Y. Ogawa [2005], “Statistical height-dependent relative importance of the Lorentz force and Joule heating in generating atmospheric gravity waves in the auroral electrojets,” J. Geophys. Res., Vol. 110, A12303, doi:10.1029/2005JA011315.

 

Zhang, S. -R., J. M. Holt, A. P. van Eyken, M. McCready, C. Amory-Mazaudier, S. Fukao, and M. Sulzer [2005], “Ionospheric local model and climatology from long-term databases of multiple incoherent scatter radars,” Geophys. Res. Lett., Vol. 32, L20102, doi:10.1029/2005GL023603.

 

Zhang S. -R., J. M. Holt, D. K. Bilitza, T. van Eyken, M. McCready, C. Amory-Mazaudier, S. Fukao, and M. Sulzer [2007], “Multiple-site comparisons between models of incoherent scatter radar and IRI,” Adv. Space Res., Vol. 39, pp.910-917, doi:10.1016/j.asr.2006.05.027.