Faculty Profiles - SHIOKAWA, Kazuo

Papers - SHIOKAWA, Kazuo

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The first long-term all-sky imager observation of lunar sodium tail Reviewed

Nishino Masaki N., Shiokawa Kazuo, Otsuka Yuichi

ICARUS Vol. 280 page： 199-204 2016.12

Ionospheric TEC Weather Map Over South America Reviewed Open Access

H. Takahashi, C. M. Wrasse, C. M. Denardini, M. B. Padua, E. R. de Paula, S. M. A. Costa, Y. Otsuka, K. Shiokawa, J. F. Galera Monico, A. Ivo, N. Sant'Anna

SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS Vol. 14 ( 11 ) page： 937 - 949 2016.11

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Ionospheric weather maps using the total electron content (TEC) monitored by ground-based Global Navigation Satellite Systems (GNSS) receivers over South American continent, TECMAP, have been operationally produced by Instituto Nacional de Pesquisas Espaciais's Space Weather Study and Monitoring Program (Estudo e Monitoramento Brasileiro de Clima Especial) since 2013. In order to cover the whole continent, four GNSS receiver networks, (Rede Brasileiro de Monitoramento Continuo) RBMC/Brazilian Institute for Geography and Statistics, Low-latitude Ionospheric Sensor Network, International GNSS Service, and Red Argentina de Monitoreo Satelital Continuo, in total similar to 140 sites, have been used. TECMAPs with a time resolution of 10min are produced in 12h time delay. Spatial resolution of the map is rather low, varying between 50 and 500km depending on the density of the observation points. Large day-to-day variabilities of the equatorial ionization anomaly have been observed. Spatial gradient of TEC from the anomaly trough (total electron content unit, 1TECU=10(16)elm(-2) (TECU) <10) to the crest region (TECU>80) causes a large ionospheric range delay in the GNSS positioning system. Ionospheric plasma bubbles, their seeding and development, could be monitored. This plasma density (spatial and temporal) variability causes not only the GNSS-based positioning error but also radio wave scintillations. Monitoring of these phenomena by TEC mapping becomes an important issue for space weather concern for high-technology positioning system and telecommunication.

DOI： 10.1002/2016SW001474

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Localized field-aligned currents in the polar cap associated with airglow patches Reviewed

Zou Ying, Nishimura Yukitoshi, Burchill Johnathan K., Knudsen David J., Lyons Larry R., Shiokawa Kazuo, Buchert Stephan, Chen Steve, Nicolls Michael J., Ruohoniemi J. Michael, McWilliams Kathryn A., Nishitani Nozomu

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 10 ) page： 10172-10189 2016.10

Heliospheric plasma sheet (HPS) impingement onto the magnetosphere as a cause of relativistic electron dropouts (REDs) via coherent EMIC wave scattering with possible consequences for climate change mechanisms Reviewed Open Access

B. T. Tsurutani, R. Hajra, T. Tanimori, A. Takada, R. Bhanu, A. J. Mannucci, G. S. Lakhina, J. U. Kozyra, K. Shiokawa, L. C. Lee, E. Echer, R. V. Reddy, W. D. Gonzalez

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 10 ) page： 10130 - 10156 2016.10

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

A new scenario is presented for the cause of magnetospheric relativistic electron decreases (REDs) and potential effects in the atmosphere and on climate. High-density solar wind heliospheric plasmasheet (HPS) events impinge onto the magnetosphere, compressing it along with remnant noon-sector outer-zone magnetospheric similar to 10-100 keV protons. The betatron accelerated protons generate coherent electromagnetic ion cyclotron (EMIC) waves through a temperature anisotropy (T-perpendicular to/T-|| > 1) instability. The waves in turn interact with relativistic electrons and cause the rapid loss of these particles to a small region of the atmosphere. A peak total energy deposition of similar to 3 x 10(20) ergs is derived for the precipitating electrons. Maximum energy deposition and creation of electron-ion pairs at 30-50 km and at > 30 km altitude are quantified. We focus the readers' attention on the relevance of this present work to two climate change mechanisms. Wilcox et al. (1973) noted a correlation between solar wind heliospheric current sheet (HCS) crossings and high atmospheric vorticity centers at 300 mb altitude. Tinsley et al. (1994) has constructed a global circuit model which depends on particle precipitation into the atmosphere. Other possible scenarios potentially affecting weather/climate change are also discussed.

DOI： 10.1002/2016JA022499

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Spectral characteristics of steady quiet-time EMIC waves observed at geosynchronous orbit Reviewed Open Access

Kim Khan-Hyuk, Park Jong-Sun, Omura Yoshiharu, Shiokawa Kazuo, Lee Dong-Hun, Kim Gi-Jeong, Jin Ho, Lee Ensang, Kwon Hyuck-Jin

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 9 ) page： 8640-8660 2016.9

A proposal on the study of solar-terrestrial coupling processes with atmospheric radars and ground-based observation network Reviewed Open Access

Tsuda Toshitaka, Yamamoto Mamoru, Hashiguchi Hiroyuki, Shiokawa Kazuo, Ogawa Yasunobu, Nozawa Satonori, Miyaoka Hiroshi, Yoshikawa Akimasa

RADIO SCIENCE Vol. 51 ( 9 ) page： 1587-1599 2016.9

Quasi-periodic rapid motion of pulsating auroras Reviewed Open Access

Fukuda Yoko, Kataoka Ryuho, Miyoshi Yoshizumi, Katoh Yuto, Nishiyama Takanori, Shiokawa Kazuo, Ebihara Yusuke, Hampton Donald, Iwagami Naomoto

POLAR SCIENCE Vol. 10 ( 3 ) page： 183-191 2016.9

Fast modulations of pulsating proton aurora related to subpacket structures of Pc1 geomagnetic pulsations at subauroral latitudes Reviewed Open Access

M. Ozaki, K. Shiokawa, Y. Miyoshi, R. Kataoka, S. Yagitani, T. Inoue, Y. Ebihara, C. -W Jun, R. Nomura, K. Sakaguchi, Y. Otsuka, M. Shoji, I. Schofield, M. Connors, V. K. Jordanova

GEOPHYSICAL RESEARCH LETTERS Vol. 43 ( 15 ) page： 7859 - 7866 2016.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

To understand the role of electromagnetic ion cyclotron (EMIC) waves in determining the temporal features of pulsating proton aurora (PPA) via wave-particle interactions at subauroral latitudes, high-time-resolution (1/8s) images of proton-induced N-2(+) emissions were recorded using a new electron multiplying charge-coupled device camera, along with related Pc1 pulsations on the ground. The observed Pc1 pulsations consisted of successive rising-tone elements with a spacing for each element of 100s and subpacket structures, which manifest as amplitude modulations with a period of a few tens of seconds. In accordance with the temporal features of the Pc1 pulsations, the auroral intensity showed a similar repetition period of 100s and an unpredicted fast modulation of a few tens of seconds. These results indicate that PPA is generated by pitch angle scattering, nonlinearly interacting with Pc1/EMIC waves at the magnetic equator.

DOI： 10.1002/2016GL070008

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Direct observational evidence for the merging of equatorial plasma bubbles Reviewed

V. L. Narayanan, S. Gurubaran, K. Shiokawa

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 8 ) page： 7923 - 7931 2016.8

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

In this work we present direct ground-based observational evidence for the merging of individual equatorial plasma bubbles (EPBs) obtained through the imaging of OI 630.0 nm airglow. Three potential mechanisms have been identified: (1) One of the EPBs tilts and reaches location of the adjacent growing EPB finally merging with it. (2) Some of the branches of an EPB arising from secondary instabilities reach out to adjacent EPB and merge with it. (3) The eastward zonal drift of the EPB on the eastern side slows down while the adjacent EPB on the western side drifts relatively faster and catches up. In one of the cases, a branch of an EPB was observed to get interchanged with another EPB as a result of merging and consequent pinching off from the parent EPB.

DOI： 10.1002/2016JA022861

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Shrinking equatorial plasma bubbles Reviewed Open Access

V. L. Narayanan, S. Gurubaran, K. Shiokawa, K. Emperumal

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 7 ) page： 6924 - 6935 2016.7

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

The formation of equatorial plasma bubbles (EPBs) associated with spread F irregularities are fairly common phenomenon in the postsunset equatorial ionosphere. These bubbles grow as a result of eastward polarization electric field resulting in upward ExB drift over the dip equator. As they grow they are also mapped to low latitudes along magnetic field lines. The EPBs are often observed as airglow depletions in the images of OI 630nm emission. On occasions the growth of the features over the dip equator is observed as poleward extensions of the depletions in all-sky images obtained from low latitudes. Herein, we present interesting observations of decrease in the latitudinal extent of the EPBs corresponding to a reduction in their apex altitudes over the dip equator. Such observations indicate that these bubbles not only grow but also shrink on occasions. These are the first observations of shrinking EPBs. The observations discussed in this work are based on all-sky airglow imaging observations of OI 630.0nm emission made from Panhala (11.1 degrees N dip latitude). In addition, ionosonde observations made from dip equatorial site Tirunelveli (1.1 degrees N dip latitude) are used to understand the phenomenon better. The analysis indicates that the speed of shrinking occurring in the topside is different from the bottomside vertical drifts. When the EPBs shrink, they might decay before sunrise hours.

DOI： 10.1002/2016JA022633

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ELF/VLF wave propagation at subauroral latitudes: Conjugate observation between the ground and Van Allen Probes A Reviewed Open Access

Martinez-Calderon Claudia, Shiokawa Kazuo, Miyoshi Yoshizumi, Keika Kunihiro, Ozaki Mitsunori, Schofield Ian, Connors Martin, Kletzing Craig, Hanzelka Miroslav, Santolik Ondrej, Kurth William S.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 6 ) page： 5384-5393 2016.6

Special issue "The 12th International Conference on Substorms"

Shiokawa Kazuo, Fok Mei-Ching, Fujimoto Masaki

EARTH PLANETS AND SPACE Vol. 68 2016.5

Possible generation mechanisms for Pc1 pearl structures in the ionosphere based on 6 years of ground observations in Canada, Russia, and Japan Reviewed Open Access

Jun Chae-Woo, Shiokawa Kazuo, Connors Martin, Schofield Ian, Poddelsky Igor, Shevtsov Boris

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 5 ) page： 4409-4424 2016.5

An evidence for prompt electric field disturbance driven by changes in the solar wind density under northward IMF B-z condition Reviewed Open Access

Diptiranjan Rout, D. Chakrabarty, R. Sekar, G. D. Reeves, J. M. Ruohoniemi, Tarun K. Pant, B. Veenadhari, K. Shiokawa

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 5 ) page： 4800 - 4810 2016.5

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Before the onset of a geomagnetic storm on 22 January 2012 (Ap = 24), an enhancement in solar wind number density from 10/cm(3) to 22/cm(3) during 0440-0510UT under northward interplanetary magnetic field (IMF B-z) condition is shown to have enhanced the high-latitude ionospheric convection and also caused variations in the geomagnetic field globally. Conspicuous changes in X are observed not only at longitudinally separated low-latitude stations over Indian (prenoon), South American (midnight), Japanese (afternoon), Pacific (afternoon) and African (morning) sectors but also at latitudinally separated stations located over high and middle latitudes. The latitudinal variation of the amplitude of the X during 0440-0510UT is shown to be consistent with the characteristics of prompt penetration electric field disturbances. Most importantly, the density pulse event caused enhancements in the equatorial electrojet strength and the peak height of the F layer (h(m)F(2)) over the Indian dip equatorial sector. Further, the concomitant enhancements in electrojet current and F layer movement over the dip equator observed during this space weather event suggest a common driver of prompt electric field disturbance at this time. Such simultaneous variations are found to be absent during magnetically quiet days. In absence of significant change in solar wind velocity and magnetospheric substorm activity, these observations point toward perceptible prompt electric field disturbance over the dip equator driven by the overcompression of the magnetosphere by solar wind density enhancement.

DOI： 10.1002/2016JA022475

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Lower thermospheric wind variations in auroral patches during the substorm recovery phase Reviewed Open Access

Oyama Shin-ichiro, Shiokawa Kazuo, Miyoshi Yoshizumi, Hosokawa Keisuke, Watkins Brenton J., Kurihara Junichi, Tsuda Takuo T., Fallen Christopher T.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 4 ) page： 3564-3577 2016.4

Coordinated observations of F region 3m field-aligned plasma irregularities associated with medium-scale traveling ionospheric disturbances Reviewed

F. F. Lin, C. Y. Wang, C. L. Su, K. Shiokawa, S. Saito, Y. H. Chu

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 4 ) page： 3750 - 3766 2016.4

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Three meter field-aligned irregularities (3m FAIs) associated with medium-scale traveling ionospheric disturbances (MSTIDs) that occurred on 5 February 2008 were observed by using the Chung-Li 52MHz coherent scatter radar. Interferometry measurements show that the plasma structures responsible for the 3m FAI echoes are in a clumpy shape with a horizontal dimension of about 10-78km in a height range of 220-300km. In order to investigate the dynamic behaviors of the plasma irregularities at different scales in the bottomside of F region, the VHF radar echo structures from the 3m FAIs combined with the 630 nm airglow images provided by the Yonaguni all-sky imager are compared and analyzed. The results show that the radar echoes were located at the west edge of the depletion zones of the 630 nm airglow image of the MSTIDs. The bulk echo structures of the 3m FAIs drifted eastward at a mean trace velocity of about 30m/s that is in general agreement with the zonal trace velocity of the MSTIDs shown in the 630nm airglow images. These results suggest that the observed F region 3m FAIs for the present case can be regarded as the targets that are frozen in the local region of theMSTIDs. In addition, the radar-observed 3mFAI echo intensity and spectral width bear high correlations to the percentage variations of the 630nm emission intensity. These results seem to suggest that through the nonlinear turbulence cascade process, theMSTID-associated 3mFAIs are very likely generated from the kilometer-scale plasma irregularities with large amplitude excited by the gradient drift instability.

DOI： 10.1002/2016JA022511

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Special issue "International CAWSES-II Symposium"

Yamamoto Mamoru, Shiokawa Kazuo, Nakamura Takuji, Gopalswamy Nat

EARTH PLANETS AND SPACE Vol. 68 2016.2

Altitude development of postmidnight F region field-aligned irregularities observed using Equatorial Atmosphere Radar in Indonesia Reviewed Open Access

Tam Dao, Otsuka Yuichi, Shiokawa Kazuo, Ram S. Tulasi, Yamamoto Mamoru

GEOPHYSICAL RESEARCH LETTERS Vol. 43 ( 3 ) page： 1015-1022 2016.2

Longitudinal frequency variation of long-lasting EMIC Pc1-Pc2 waves localized in the inner magnetosphere Reviewed Open Access

K. -H. Kim, K. Shiokawa, I. R. Mann, J. -S. Park, H. -J. Kwon, K. Hyun, H. Jin, M. Connors

GEOPHYSICAL RESEARCH LETTERS Vol. 43 ( 3 ) page： 1039 - 1046 2016.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

Long-lasting (>20h) electromagnetic ion cyclotron (EMIC) Pc1-Pc2 waves were observed by the Athabasca (L =approximate to 4.6) induction magnetometer and Canadian Array for Realtime Investigations of Magnetic Activity (L =approximate to 4-6) fluxgate magnetometers on 5 April 2007. These waves showed a systematic frequency change with local time, the minimum frequency near dusk, and the maximum frequency near dawn. Assuming the plasmapause as a potential source region of the waves, we estimated the plasmapause location from localized proton enhancement (LPE) events observed at NOAA-Polar Orbiting Environmental Satellites and METOP-2 satellites. We found that the longitudinal frequency variation of EMIC waves has a clear correlation with the estimated plasmapause location and that the waves are in the frequency band between the equatorial helium and oxygen gyrofrequencies at the estimated plasmapause. With our analysis results we suggest that the LPE events are caused by wave-particle interaction with the helium band EMIC waves generated near the plasmapause.

DOI： 10.1002/2015GL067536

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EMIC waves observed at geosynchronous orbit under quiet geomagnetic conditions (Kp1) Reviewed Open Access

J. -S. Park, K. -H. Kim, K. Shiokawa, D. -H. Lee, E. Lee, H. -J. Kwon, H. Jin, G. Jee

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 121 ( 2 ) page： 1377 - 1390 2016.2

Language：English Publishing type：Research paper (scientific journal) Publisher：AMER GEOPHYSICAL UNION

We statistically study the local time distribution of the helium band electromagnetic ion cyclotron (EMIC) waves observed at geosynchronous orbit when geomagnetic activity was low (Kp 1). In order to identify the geosynchronous EMIC waves, we use high time resolution magnetic field data acquired from GOES 10, 11, and 12 over a 2year period from 2007 and 2008 and examine the local time distribution of EMIC wave events. Unlike previous studies, which reported high EMIC wave occurrence in the postnoon sector with a peak around 1500-1600 magnetic local time (MLT) during magnetically disturbed times (i.e., storm and/or substorm), we observed that quiet time EMIC waves mostly occur in a region from morning (approximate to 0600MLT) to afternoon (approximate to 1600MLT) with a peak around 1100-1200MLT. To investigate whether the quiet time EMIC wave occurrence has a causal relationship with magnetospheric convection enhancement or solar wind dynamic pressure variations, we performed a superposed epoch analysis of solar wind parameters (solar wind speed, density, dynamic pressure, and interplanetary magnetic field B-z) and geomagnetic indices (AE and SYM-H). From the superposed epoch analysis we found that solar wind dynamic pressure variation is a more important parameter than AE and SYM-H for quiet time EMIC wave occurrence.

DOI： 10.1002/2015JA021968

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Papers - SHIOKAWA, Kazuo