Faculty Profiles - SHIOKAWA, Kazuo

Papers - SHIOKAWA, Kazuo

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Auroral Heating of Plasma Patches Due to High-Latitude Reconnection Reviewed

Pena Joaquin Diaz, Semeter Joshua, Nishimura Yukitoshi, Varney Roger, Reimer Ashton, Hairston Marc, Zettergren Matthew, Hirsch Michael, Verkhoglyadova Olga, Hosokawa Keisuke, Shiokawa Kazuo

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 12 ) 2021.12

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

This study exploits the volumetric sampling capabilities of the Resolute Bay Incoherent Scatter Radar (RISR-N) in collaboration with all-sky imagery and in situ measurements to examine the interplay between cold plasma transport and auroral precipitation during a high-latitude lobe reconnection event on the dawn side. Solar wind IMF preceding the event was characterized by an impulsive negative excursion in Bz embedded within a period of Bz > 0 and By < 0. The combined effects of transport and magnetic stress release associated with a high-latitude reconnection pulse drove a co-mingling between patches and soft electron precipitation, creating common regions of elevated electron density and temperature. Vertical ionospheric profiles extracted in the rest frame of the drifting patch showed a contemporaneous increase in Te above 200 km and Ne below 250 km while at the same time showing only a small impact in Ne near the F-region peak. The observations suggest a new mechanism for creating a “hot patch” wherein the density enhancement is not generated by the precipitation but is warmed by it. The physics-based GEMINI model was used to explore the response to the observed precipitation as a function of altitude and time. Model results suggest that a correlated enhancement in Ne and Te at DMSP altitudes (∼800 km), that is, hot patch, can be produced by auroral heating and upward diffusion, irrespective of lower altitude density structure. The study highlights the need for densely distributed observations in space and time for understanding both mesoscale and small-scale ionospheric dynamics in regions subject to complex forcing.

DOI： 10.1029/2021JA029657

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Study of an Equatorward Detachment of Auroral Arc From the Oval Using Ground‐Space Observations and the BATS‐R‐US–CIMI Model Reviewed

Sneha Yadav, K. Shiokawa, S. Oyama, Y. Inaba, N. Takahashi, K. Seki, K. Keika, Tzu‐Fang Chang, S. W. Y. Tam, B.‐J. Wang, Y. Kazama, S.‐Y. Wang, K. Asamura, S. Kasahara, S. Yokota, T. Hori, Y. Kasaba, F. Tsuchiya, A. Kumamoto, M. Shoji, Y. Kasahara, A. Matsuoka, S. Matsuda, C.‐W. Jun, S. Imajo, Y. Miyoshi, I. Shinohara

Journal of Geophysical Research: Space Physics Vol. 126 ( 12 ) 2021.12

Multipoint Measurement of Fine‐Structured EMIC Waves by Arase, Van Allen Probe A, and Ground Stations Reviewed

S. Matsuda, Y. Miyoshi, Y. Kasahara, L. Blum, C. Colpitts, K. Asamura, Y. Kasaba, A. Matsuoka, F. Tsuchiya, A. Kumamoto, M. Teramoto, S. Nakamura, M. Kitahara, I. Shinohara, G. Reeves, H. Spence, K. Shiokawa, T. Nagatsuma, S. Oyama, I. R. Mann

Geophysical Research Letters Vol. 48 ( 23 ) 2021.11

Periodicities and Colors of Pulsating Auroras: DSLR Camera Observations From the International Space Station Reviewed

Nanjo Sota, Hozumi Yuta, Hosokawa Keisuke, Kataoka Ryuho, Miyoshi Yoshizumi, Oyama Shin-ichiro, Ozaki Mitsunori, Shiokawa Kazuo, Kurita Satoshi

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 10 ) 2021.10

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

We investigated the spatial characteristics of pulsating auroras (PsA) using digital camera measurements from the International Space Station. These measurements covered PsAs in (Formula presented.) 5-h wide regions in the magnetic local time (MLT) direction in short time intervals ((Formula presented.) 10 min). Analyses of two events suggested that the periodicity of the main pulsation of a PsA does not exhibit any clear dependence on the magnetic latitude (63– (Formula presented.)) and MLT (00–05). These results suggest that the periods are not controlled by the bounce time of trapped electrons but by local conditions such as gradients of temperature and/or density of electrons near the magnetospheric source region. We also analyzed the colors of PsAs as proxies for the energies of precipitating electrons. The blue and green channels of the digital camera are sensitive to the band emission of molecular nitrogen ions and the green line of oxygen atoms, respectively. Because the energy bands of precipitating electrons producing those two emissions are different, ratios of blue to green (B/G ratios) can be used as proxies for the energies of PsA electrons. The B/G ratio tends to be higher in the morning sector than in the midnight sector, which is consistent with the results of previous studies showing the MLT dependence of the energies of PsA electrons. This capability of estimating the energies of auroral electrons from digital camera images is expected to provide more opportunities for citizen scientists to contribute more deeply to auroral science.

DOI： 10.1029/2021JA029564

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Isolated Proton Aurora Driven by EMIC Pc1 Wave: PWING, Swarm, and NOAA POES Multi-Instrument Observations Reviewed

Hyangpyo Kim, Kazuo Shiokawa, Jaeheung Park, Yoshizumi Miyoshi, Yukinaga Miyashita, Claudia Stolle, Hyunju Kim Connor, Junga Hwang, Stephan Buchert, Hyuck Jin Kwon, Satoko Nakamura, Kohki Nakamura, Shin Ichiro Oyama, Yuichi Otsuka, Tsutomu Nagatsuma, Kaori Sakaguchi

Geophysical Research Letters Vol. 48 ( 18 ) 2021.9

Language：English Publishing type：Research paper (scientific journal)

We report the concurrent observations of F-region plasma changes and field-aligned currents (FACs) above isolated proton auroras (IPAs) associated with electromagnetic ion cyclotron Pc1 waves. Key events on March 19, 2020 and September 12, 2018 show that ground magnetometers and all-sky imagers detected concurrent Pc1 wave and IPA, during which NOAA POES observed precipitating energetic protons. In the ionospheric F-layer above the IPA zone, the Swarm satellites observed transverse Pc1 waves, which span wider latitudes than IPA. Around IPA, Swarm also detected the bipolar FAC and localized plasma density enhancement, which is occasionally surrounded by wide/shallow depletion. This indicates that wave-induced proton precipitation contributes to the energy transfer from the magnetosphere to the ionosphere.

DOI： 10.1029/2021GL095090

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An experimental investigation into the possible connections between the zonal neutral wind speeds and equatorial plasma bubble drift velocities over the African equatorial region Reviewed

Okoh D. I, Rabiu A. B., Shiokawa K., Otsuka Y., Wu Q., Seemala G. K., Katamzi-Joseph Z. T.

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 220 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Atmospheric and Solar-Terrestrial Physics

There is increasing interest to understand thermospheric neutral wind and ionized plasma coupling, especially by using empirical observations. This is the first study that reports simultaneous measurements of thermospheric neutral wind and equatorial plasma bubble (EPB) speeds over the African equatorial region. Neutral wind speeds were obtained using a Fabry-Perot interferometer (FPI), while EPB speeds were obtained using an all-sky optical imager. Both instruments are co-located in Abuja (Geographic: 8.99°N, 7.38°E; Geomagnetic: 1.60°S). Data for 11 nights of coincident neutral wind and EPB speed observations were used. The neutral wind speeds were in the range of about −30 to 300 m/s, while EPB speeds were in the range of about 15–400 m/s. The speeds of both neutral winds and EPBs were generally observed to be faster during the early night hours and to slow down towards midnight. In some instances, the neutral wind and EPB speeds were comparable, an observation that is in agreement with full development of the F region dynamo. There were also instances in which the EPBs were faster or slower than the neutral winds. In one of the nights, a southward turning of the IMF-Bz was observed to cause a sudden increase in the EPB speed. For some nights, the neutral winds were faster than the EPBs during earlier hours of the nights, and the disparity reduced during the later hours of the nights. This was attributed to the possibility that the F region dynamo was yet to be fully developed during the earlier hours.

DOI： 10.1016/j.jastp.2021.105663

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First Simultaneous Observation of a Night Time Medium‐Scale Traveling Ionospheric Disturbance From the Ground and a Magnetospheric Satellite Reviewed

K. Kawai, K. Shiokawa, Y. Otsuka, S. Oyama, Y. Kasaba, Y. Kasahara, F. Tsuchiya, A. Kumamoto, S. Nakamura, A. Matsuoka, S. Imajo, Y. Kazama, S.‐Y. Wang, S. W. Y. Tam, T. F. Chang, B. J. Wang, K. Asamura, S. Kasahara, S. Yokota, K. Keika, T. Hori, Y. Miyoshi, C. Jun, M. Shoji, I. Shinohara

Journal of Geophysical Research: Space Physics Vol. 126 ( 9 ) 2021.9

Multi-instrument study of longitudinal wave structures for plasma bubble seeding in the equatorial ionosphere Reviewed

Takahashi H., Essien P., Figueiredo C. A. O. B., Wrasse C. M., Barros D., Abdu M. A., Otsuka Y., Shiokawa K., Li GuoZhu

EARTH AND PLANETARY PHYSICS Vol. 5 ( 5 ) page： 368 - 377 2021.9

Language：English Publishing type：Research paper (scientific journal) Publisher：Earth and Planetary Physics

Large Scale Wave Structures (LSWS) in the equatorial ionospheric F-region were observed by measuring spatial and temporal variations within detrended total electron content (dTEC) data obtained by ground-based GNSS receivers over the South American continent. By using dTEC-maps, we have been able to produce, for the first-time, two-dimensional representations of LSWS. During the period from September to December, the LSWS frequently occurred starting a few hours prior to Equatorial Plasma Bubble (EPB) development. From 17 events of LSWS observed in 2014 and 2015, wave characteristics were obtained: the observed wavelengths, periods, and the phase speeds are respectively, ~900 km, ~41 min and ~399 m/s; the waves propagated from the northeast to southeast. In some cases the front of the oscillation was meridionally aligned, extending to more than 1600 km, the first time such large extension of the wavefront has been reported. From F-layer bottom height oscillation data, measured by ionosonde, LSWS exhibit two different vertical phase propagation modes, in-phase and downward phase. The former mode indicates the presence of a polarization electric field in the F-layer bottom side; the latter suggests propagation of atmospheric gravity waves. The presence of LSWS near the solar terminator, followed by the development of EPBs, suggests that the upwelling of the F-layer bottom height produces a condition favorable to the development of Rayleigh–Taylor instability.

DOI： 10.26464/epp2021047

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PSTEP: project for solar-terrestrial environment prediction Reviewed International journal

Kanya Kusano, Kiyoshi Ichimoto, Mamoru Ishii, Yoshizumi Miyoshi, Shigeo Yoden, Hideharu Akiyoshi, Ayumi Asai, Yusuke Ebihara, Hitoshi Fujiwara, Tada-Nori Goto, Yoichiro Hanaoka, Hisashi Hayakawa, Keisuke Hosokawa, Hideyuki Hotta, Kornyanat Hozumi, Shinsuke Imada, Kazumasa Iwai, Toshihiko Iyemori, Hidekatsu Jin, Ryuho Kataoka, Yuto Katoh, Takashi Kikuchi, Yuki Kubo, Satoshi Kurita, Haruhisa Matsumoto, Takefumi Mitani, Hiroko Miyahara, Yasunobu Miyoshi, Tsutomu Nagatsuma, Aoi Nakamizo, Satoko Nakamura, Hiroyuki Nakata, Naoto Nishizuka, Yuichi Otsuka, Shinji Saito, Susumu Saito, Takashi Sakurai, Tatsuhiko Sato, Toshifumi Shimizu, Hiroyuki Shinagawa, Kazuo Shiokawa, Daikou Shiota, Takeshi Takashima, Chihiro Tao, Shin Toriumi, Satoru Ueno, Kyoko Watanabe, Shinichi Watari, Seiji Yashiro, Kohei Yoshida, Akimasa Yoshikawa

EARTH PLANETS AND SPACE Vol. 73 ( 1 ) 2021.8

Language：English Publishing type：Research paper (scientific journal) Publisher：SPRINGER

Although solar activity may significantly impact the global environment and socioeconomic systems, the mechanisms for solar eruptions and the subsequent processes have not yet been fully understood. Thus, modern society supported by advanced information systems is at risk from severe space weather disturbances. Project for solar-terrestrial environment prediction (PSTEP) was launched to improve this situation through synergy between basic science research and operational forecast. The PSTEP is a nationwide research collaboration in Japan and was conducted from April 2015 to March 2020, supported by a Grant-in-Aid for Scientific Research on Innovative Areas from the Ministry of Education, Culture, Sports, Science and Technology of Japan. By this project, we sought to answer the fundamental questions concerning the solar-terrestrial environment and aimed to build a next-generation space weather forecast system to prepare for severe space weather disasters. The PSTEP consists of four research groups and proposal-based research units. It has made a significant progress in space weather research and operational forecasts, publishing over 500 refereed journal papers and organizing four international symposiums, various workshops and seminars, and summer school for graduate students at Rikubetsu in 2017. This paper is a summary report of the PSTEP and describes the major research achievements it produced.

DOI： 10.1186/s40623-021-01486-1

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Does Solar Variation Change Earth's Environment?

SHIOKAWA Kazuo

TRENDS IN THE SCIENCES Vol. 26 ( 8 ) page： 8_18 - 8_21 2021.8

Spatial Evolution of Wave‐Particle Interaction Region Deduced From Flash‐Type Auroras and Chorus‐Ray Tracing Reviewed

Mitsunori Ozaki, Tomohiro Inoue, Yoshimasa Tanaka, Satoshi Yagitani, Yoshiya Kasahara, Kazuo Shiokawa, Yoshizumi Miyoshi, Kousuke Imamura, Keisuke Hosokawa, Shin‐ichiro Oyama, Ryuho Kataoka, Yusuke Ebihara, Yasunobu Ogawa, Akira Kadokura

Journal of Geophysical Research: Space Physics Vol. 126 ( 7 ) 2021.7

What controls the luminosity of polar cap airglow patches?: Implication from airglow measurements in Eureka, Canada in comparison with SuperDARN convection pattern Reviewed

Hosokawa K., Nagata M., Shiokawa K., Otsuka Y.

POLAR SCIENCE Vol. 28 2021.6

Language：English Publishing type：Research paper (scientific journal) Publisher：Polar Science

Polar cap patches are known as islands of enhanced electron density in the polar cap F region ionosphere. To observe the airglow signature of polar cap patches continuously at a fixed point near the center of the MLAT/MLT coordinate system, we started operating an all-sky imager in Eureka, Canada since 2015, where the magnetic latitude is ~87°. By statistically analyzing the 630-nm airglow images from Eureka, it was identified that the luminosity of patches, which is proportional to the electron density in the F region, increases during specific UT interval from 16 to 22 UT. This outstanding UT variation of patch luminosity can be explained simply by the systematic shift of the terminator in the MLAT/MLT coordinate system due to the offset between the geographic and geomagnetic pole. That is, the spatial relationship between the dense source plasma in the sunlit area and the high-latitude convection system controls the UT variation. We also found that when the IMF By is positive, the number of polar cap patches was twice of that in the negative IMF By. By deriving average convection patterns from the archived SuperDARN map potential data, we confirmed that the configuration of plasma convection is more appropriate for patches to be transported toward the magnetic pole during the positive IMF By condition.

DOI： 10.1016/j.polar.2020.100608

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Influence of Zonal Wind Velocity Variation on Equatorial Plasma Bubble Occurrences Over Southeast Asia Reviewed

Sarudin I., Hamid N. S. A., Abdullah M., Buhari S. M., Shiokawa K., Otsuka Y., Hozumi K., Jamjareegulgarn P.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 5 ) 2021.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

The present study aims to investigate the influence of the zonal wind velocity on equatorial plasma bubble (EPB) occurrences over Southeast Asia. The observation of the EPB occurrence is obtained from the GPS Rate of TEC change index. Meanwhile, the zonal winds were measured using a Fabry-Perot interferometer located at Kototabang and Chiang Mai stations, and the height of F layer was acquired using an ionosonde at Chumphon station near the magnetic equator. This is the first study to report the influence of zonal wind velocity variation on EPB occurrences with the presence and absence of EPB using GPS data in the Southeast Asian sector. The results illustrated that the average magnitude of zonal wind velocity during the presence of EPB (78 ± 23 m/s) was higher than that of its absence (68 ± 21 m/s). It was observed using long-term data analyses which led to in-depth analyses. The analysis of temporal variation of zonal wind variation demonstrated that the zonal winds during EPB were higher in the evening compared to midnight and postmidnight periods from medium to high solar activities. The dependence of zonal wind velocity on EPB over local time was obtained based on the analysis which utilized the data collected during equinox in high solar activity. Besides that, a positive correlation was obtained between the zonal wind velocity and EPB occurrences during pre-reversal enhancement (PRE) corroborated the effects of zonal wind influence on PRE, and thus EPB occurrences.

DOI： 10.1029/2020JA028994

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Simultaneous Observation of Two Isolated Proton Auroras at Subauroral Latitudes by a Highly Sensitive All-Sky Camera and Van Allen Probes Reviewed

Nakamura Kohki, Shiokawa Kazuo, Otsuka Yuichi, Shinbori Atsuki, Miyoshi Yoshizumi, Connors Martin, Spence Harlan, Reeves Geoff, Funsten Herbert O., MacDowall Robert, Smith Charles, Wygant John, Bonnell John

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 5 ) 2021.5

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

Isolated proton auroras (IPAs) appearing at subauroral latitudes are generated by energetic protons precipitating from the magnetosphere through interaction with electromagnetic ion cyclotron (EMIC) waves. An IPA thus indicates the spatial scale and temporal variation of wave-particle interactions in the magnetosphere. In this study, a unique event of simultaneous ground and magnetospheric satellite observations of two IPAs were conducted on March 16, 2015, using an all-sky imager at Athabasca, Canada and Van Allen Probes. The Van Allen Probes observed two isolated EMIC waves with frequencies of ∼1 and 0.4 Hz at L ≈ 5.0 when the satellite footprint crossed over the two IPAs. This suggests that the IPAs were caused by localized EMIC waves. Proton flux at 5–20 keV increased locally when the EMIC waves appeared. Electron flux at energies below ∼500 eV also increased. Temperature anisotropy of the energetic protons was estimated at 1.5–2.5 over a wide L-value range of 3.0–5.2. Electron density gradually decreased from L = 3.5 to 5.4, suggesting that the EMIC wave at L ≈ 5.0 was located in the gradual plasmapause. From these observations, we conclude that the localized IPAs and associated EMIC waves took place because of localized enhancement of energetic proton flux and plasma density structure near the plasmapause. The magnetic field observed by the satellite showed small variation during the wave observation, indicating that the IPAs were accompanied by the weak field-aligned current.

DOI： 10.1029/2020JA029078

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Multi‐Event Analysis of Plasma and Field Variations in Source of Stable Auroral Red (SAR) Arcs in Inner Magnetosphere During Non‐Storm‐Time Substorms Reviewed

Yudai Inaba, Kazuo Shiokawa, Shin‐ichiro Oyama, Yuichi Otsuka, Martin Connors, Ian Schofield, Yoshizumi Miyoshi, Shun Imajo, Atsuki Shinbori, Artem Yu Gololobov, Yoichi Kazama, Shiang‐Yu Wang, Sunny W. Y. Tam, Tzu‐Fang Chang, Bo‐Jhou Wang, Kazushi Asamura, Shoichiro Yokota, Satoshi Kasahara, Kunihiro Keika, Tomoaki Hori, Ayako Matsuoka, Yoshiya Kasahara, Atsushi Kumamoto, Shoya Matsuda, Yasumasa Kasaba, Fuminori Tsuchiya, Masafumi Shoji, Masahiro Kitahara, Satoko Nakamura, Iku Shinohara, Harlan E. Spence, Geoff D. Reeves, Robert J. Macdowall, Charles W. Smith, John R. Wygant, John W. Bonnell

Journal of Geophysical Research: Space Physics Vol. 126 ( 4 ) 2021.4

Preface of the special issue: "Variability of the Sun and Its Terrestrial Impact (VarSITI) Completion Symposium 2019 and the SCOSTEP 14th Quadrennial Solar-Terrestrial Physics Symposium (STP14)" Preface Reviewed

Shiokawa Kazuo, Dasso Sergio, Miteva Rositsa, Pallamraju Duggirala, Zhang Shun-Rong

JOURNAL OF ATMOSPHERIC AND SOLAR-TERRESTRIAL PHYSICS Vol. 215 2021.4

Development of research capacities in space weather: a successful international cooperation Reviewed

Amory-Mazaudier Christine, Radicella Sandro, Doherty Patricia, Gadimova Sharafat, Fleury Rolland, Nava Bruno, Anas Emran, Petitdidier Monique, Migoya-Orue Yenca, Alazo-Cuartas Katy, Shiokawa Kazuo

JOURNAL OF SPACE WEATHER AND SPACE CLIMATE Vol. 11 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Space Weather and Space Climate

This paper presents an international cooperation which has successfully developed research capacities in the scientific disciplines of sun-earth relations and space weather in many countries over the world during the past decades. This success was based on the deployment of scientific instruments in countries that did not have them, on the sharing of knowledge and research tools, on thesis supervision and on the integration of researchers trained in their country. This article will only focus on aspects of training conducted by ICTP, Boston College, ICG, SCOSTEP and GIRGEA. We will highlight what has been enhanced in international cooperation to achieve this success and what remains to be done.

DOI： 10.1051/swsc/2021006

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Magnetic Conjugacy of Pc1 Waves and Isolated Proton Precipitation at Subauroral Latitudes: Importance of Ionosphere as Intensity Modulation Region Reviewed

Mitsunori Ozaki, Kazuo Shiokawa, Richard B. Horne, Mark J. Engebretson, Marc Lessard, Yasunobu Ogawa, Keisuke Hosokawa, Masahito Nosé, Yusuke Ebihara, Akira Kadokura, Satoshi Yagitani, Yoshizumi Miyoshi, Shion Hashimoto, Shipra Sinha, Ashwini K. Sinha, Gopi K. Seemala, Chae‐Woo Jun

Geophysical Research Letters Vol. 48 ( 5 ) 2021.3

A review of the SCOSTEP's 5-year scientific program VarSITI-Variability of the Sun and Its Terrestrial Impact Reviewed

Shiokawa Kazuo, Georgieva Katya

PROGRESS IN EARTH AND PLANETARY SCIENCE Vol. 8 ( 1 ) 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Progress in Earth and Planetary Science

The Sun is a variable active-dynamo star, emitting radiation in all wavelengths and solar-wind plasma to the interplanetary space. The Earth is immersed in this radiation and solar wind, showing various responses in geospace and atmosphere. This Sun–Earth connection variates in time scales from milli-seconds to millennia and beyond. The solar activity, which has a ~11-year periodicity, is gradually declining in recent three solar cycles, suggesting a possibility of a grand minimum in near future. VarSITI—variability of the Sun and its terrestrial impact—was the 5-year program of the scientific committee on solar-terrestrial physics (SCOSTEP) in 2014–2018, focusing on this variability of the Sun and its consequences on the Earth. This paper reviews some background of SCOSTEP and its past programs, achievements of the 5-year VarSITI program, and remaining outstanding questions after VarSITI. [Figure not available: see fulltext.]

DOI： 10.1186/s40645-021-00410-1

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GPS Scintillations and TEC Variations in Association With a Polar Cap Arc Reviewed

Wang Yong, Cao Zheng, Xing Zan-Yang, Zhang Qing-He, Jayachandran P. T., Oksavik K., Balan Nanan, Shiokawa K.

JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS Vol. 126 ( 3 ) 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Journal of Geophysical Research: Space Physics

A unique example of a polar cap arc producing clear amplitude and phase scintillations in GPS L-band signals is presented using observations from an all-sky imager and a GPS receiver and a digital ionosonde at Resolute Bay and the SuperDARN Inuvik radar. During the southward interplanetary magnetic field (IMF) condition, the polar cap arc moved quickly from the dusk-side to the midnight auroral oval at a speed of ∼700 m/s, as revealed by all-sky 557.7 and 630.0 nm images. When it intersected the raypath of GPS signals, both amplitude and phase scintillations appeared, which is very different from previous results. Moreover, the scintillations were precisely determined through power spectral analysis. We propose that the strong total electron content (TEC) enhancement (∼6 TECU) and flow shears in association with the polar cap arc under the southward IMF condition were creating the scintillations. It provides evidence for the existence of polar cap arc scintillations that may be harmful for satellite applications even through L-band signals.

DOI： 10.1029/2020JA028968

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Papers - SHIOKAWA, Kazuo