Article
Astronomy & Astrophysics
Xiaocan Liu, Junjie Chen, Peng Han, Jiuhou Lei, Tong Dang, Fuqing Huang, Huaran Chen, Liguo Jiao, Xinxin Ma, Jiyao Tu, Yu Lei, Junhao Zhao
Summary: In this study, the researchers examined the response of geomagnetic daily variation and ionospheric currents to a solar annular eclipse that passed through China in June 2020. They found that the eclipse reduced the intensity of the geomagnetic daily variation, as well as the ionospheric solar quiet current system. The response varied depending on local time and latitude. The study also verified these findings using a global physical model.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Geochemistry & Geophysics
Zhao XuDong, He YuFei, Li Qi, Liu XiaoCan
Summary: The daily variation amplitude of the geomagnetic component Z from the Geomagnetic Network of China was analyzed for the past twelve years. The study found that the ionospheric conductivity primarily contributes to the daily variations of Z, with the same month or season changing with solar activity. However, the neutral wind in the ionosphere may also affect the daily variation amplitude of Z in certain scenarios. In Yunnan Province, the complex underground electrical structures act as an amplifier, increasing the daily variations amplitude of Z.
CHINESE JOURNAL OF GEOPHYSICS-CHINESE EDITION
(2022)
Article
Engineering, Aerospace
PR. Fagundes, VY. Tsali-Brown, VG. Pillat, MO. Arcanjo, K. Venkatesh, JB. Habarulema, M. J. A. Bolzan, R. de Jesus, A. J. de Abreu, A. Tardelli, F. Vieira, CM. Denardini
Summary: Coronal mass ejection (CME) is the abrupt release of solar plasma with an intrinsic magnetic field. CMEs often follow solar flares (SF). The released plasma cloud travels from the Sun to the Earth's system, impacting the ionosphere and causing geomagnetic storms.
ADVANCES IN SPACE RESEARCH
(2023)
Article
Engineering, Aerospace
Amalia Meza, Guillermo Bosch, Maria Paula Natali, Bernardo Eylenstein
Summary: Researchers studied VTEC measurements and geomagnetic field estimations during the 2017 North American eclipse, finding significant differences in the responses of the ionosphere and magnetic field to the eclipse event. They discovered that analyzing VTEC differences with respect to reference values provides better insight into the actual eclipse effect, and were able to characterize parameters such as time delay of maximum depletion and recovery phase. Additionally, they were able to test models quantitatively linking ionospheric variations, showing a striking accurate match between total electron content depletion measurements from GNSS and the behavior of magnetic field components over time.
ADVANCES IN SPACE RESEARCH
(2022)
Article
Astronomy & Astrophysics
Junjie Chen, Jiuhou Lei, Wenbin Wang, Jing Liu, Astrid Maute, Liying Qian, Ruilong Zhang, Tong Dang
Summary: In this study, the response of ionospheric electrodynamic processes to solar flares on September 6 and 10, 2017 was investigated using a numerical model. The simulations showed that solar flares increased global daytime currents and reduced eastward electric fields, primarily due to enhanced E-region conductivity. This study highlights the importance of considering the effects of flare-induced conductivity enhancements in understanding ionospheric electrodynamic responses.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
L. Holappa, R. M. Robinson, A. Pulkkinen, T. Asikainen, K. Mursula
Summary: Recent studies have shown that there is a dependence of auroral electrojets in the Northern Hemisphere on the B-y component of the interplanetary magnetic field (IMF), with a reversal of this dependence in NH summer compared to NH winter. The explicit B-y dependence is strong in the winter hemisphere but weak in the summer hemisphere.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Astronomy & Astrophysics
Wan Nur Izzaty Ismail, Nurul Shazana Abdul Hamid, Mardina Abdullah, Akimasa Yoshikawa, Teiji Uozumi, Zahira Mohd Radzi
Summary: This study investigated the longitudinal variability and local time characteristics of equatorial electrojet (EEJ) current using ground and satellite magnetometer data. Results showed good agreement between satellite and ground EEJ measurements during low solar activity, with seasonal dependence observed in the timing of maximum EEJ appearances in certain longitude sectors.
Article
Environmental Sciences
Shuhan Li, Jing Liu, Qiaoling Li
Summary: Ionospheric ion upflow is an important process for magnetosphere-ionosphere coupling. Both SAPS and neutral wind have impacts on ion upflow.
Article
Geosciences, Multidisciplinary
Yosuke Yamazaki
Summary: This paper describes the solar and lunar daily variations of the geomagnetic field in low- and mid-latitude regions using data from the Swarm satellites. The study finds that these variations are mainly of internal origin and can be attributed to ionospheric dynamo currents and induced underground currents. The global patterns of the internal solar and lunar current systems are consistent with previous ground observations.
EARTH PLANETS AND SPACE
(2022)
Article
Astronomy & Astrophysics
Qiaoling Li, Shuhan Li, Junjie Chen, Jing Liu, Ruilong Zhang, Libo Liu, Jiawei Kuai
Summary: The interplanetary magnetic field (IMF) has a significant influence on the global ionospheric electrodynamics, especially under long-duration northward IMF B-z (NBz) and B-y conditions. This study found that both NBz and B-y can significantly change the plasma convection, Joule heating, and thermospheric winds, and the penetration electric field (PEF) due to NBz plays an important role in the decrease of the equatorial electric field. The research also indicates that the NBz effects on the equatorial ionospheric electrodynamics are significant even during weak geomagnetic conditions, apart from the widely believed meteorological effects.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Pengyu Zhang, Yang-Yi Sun, Chieh-Hung Chen, Zhiqiang Mao
Summary: In this study, an improved method utilizing a magnetic observatory network in Asia was proposed to automatically determine the focus of the Solar quiet (Sq) current. By considering the variability and asymmetry of the Sq current, the proposed method determines the Sq focus through longitudinal and latitudinal fitting processes. Experimental results demonstrate that the method is capable of tracking the trajectory of the Sq focus, and the observing procedure experiment efficiently validates its performance.
EARTH AND SPACE SCIENCE
(2023)
Article
Multidisciplinary Sciences
Anna Morozova, Rania Rebbah, Paulo Ribeiro
Summary: This study utilizes raw geomagnetic field observations from the Coimbra Magnetic Observatory to investigate daily variations, extracting data using two methods. Results show that both methods are effective in capturing regular geomagnetic field variations related to daily changes, particularly in the ionospheric dynamo and magnetospheric currents.
Article
Engineering, Aerospace
Juan Manuel Castano, Maria Paula Natali, Amalia Meza
Summary: In this study, the behavior of the mid-latitude ionospheric trough (MIT) during solar cycle 24 was analyzed using Global Ionospheric Maps (GIMs). The MIT position shows asymmetry between the Northern and Southern Hemispheres, with equatorward movement during high solar activity. In addition, there is a clear dependence between MIT position and solar wind speed and IMF Bz-component at certain time scales.
ADVANCES IN SPACE RESEARCH
(2021)
Article
Astronomy & Astrophysics
Yunfang Zhong, Hui Wang, Hermann Luehr, Kedeng Zhang, Hao Xia, Chengyu Qian, Chengzhi Wang, Yu Sun
Summary: This study investigates the response of the ionospheric radial current (IRC) in the F region to the enhancement of merging electric field (Em) at different magnetic local times (MLT). The results show that IRC increases in the upward (downward) direction in the daytime (nighttime) within a short period after Em enhancement. The changes in disturbance zonal winds and F region electron density could explain the observed variations in the IRC. This work suggests that the penetration electric field effect plays a significant role in the changes of IRC in the ionospheric F layer.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
M. N. Pedersen, H. Vanhamaki, A. T. Aikio, S. Kaki, A. B. Workayehu, C. L. Waters, J. W. Gjerloev
Summary: This study investigates the impact of 28 geomagnetic storms driven by high-speed streams and associated stream interaction regions on ionospheric horizontal and field-aligned currents during 2010-2017. The currents peak 4-5.3 hours after the onset of the storm main phase, driven strongly by the solar wind. High solar wind dynamic pressure storms exhibit faster solar wind velocity maxima and shorter lead times compared to low dynamic pressure events.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2021)
Article
Engineering, Civil
Hiroki Yamashita, Christofer Feldmeier, Yosuke Yamazaki, Takanori Kato, Takahiro Fujimoto, Osamu Kondo, Hiroyuki Sugiyama
Summary: This study developed a wheel profile optimization procedure to minimize flange wear while considering wear evolution. Experimental validation showed that the optimized profile can reduce both flange wear and tread surface damage simultaneously over an extended traveling distance.
PROCEEDINGS OF THE INSTITUTION OF MECHANICAL ENGINEERS PART F-JOURNAL OF RAIL AND RAPID TRANSIT
(2022)
Article
Geosciences, Multidisciplinary
Y. Yamazaki, C. Arras, S. Andoh, Y. Miyoshi, H. Shinagawa, B. J. Harding, C. R. Englert, T. J. Immel, S. Sobhkhiz-Miandehi, C. Stolle
Summary: This study provides observational support for the wind shear theory, showing that the occurrence of Es is correlated with the negative vertical shear of the eastward wind. Es can still be observed even when the vertical wind shear is positive.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
Charles Owolabi, Haibing Ruan, Y. Yamazaki, R. O. Kaka, O. O. Akinola, Akimasa Yoshikawa
Summary: This study investigated the solar quiet (Sq) ionospheric current variations over the American and European/African sectors. The Sq current function was derived using ground magnetometer data and decomposed into eigenmodes using empirical orthogonal function (EOF) analysis. The first three eigenmodes captured 96% of the overall Sq current variance. The EOF model successfully reconstructed the observed Sq current function and revealed its association with magnetic latitude, local time, season, and solar activity. The patterns of Sq current function were similar in both longitudinal sectors but with varying amplitudes. The newly developed model reproduced the Sq current variability over the two sectors as long as the observed variations had sufficient duration.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Kedeng Zhang, Hui Wang, Yosuke Yamazaki
Summary: This study investigates the temporal responses of the equatorial electrojet (EEJ) to subauroral polarization streams (SAPS). The results show that the counter equatorial electrojet (CEJ) excited by SAPS exhibits consistent temporal variations with SAPS, with a larger influence from zonal wind than meridional wind. The relative time delay between CEJ and SAPS is related to the propagation time of disturbance wind. This study contributes to the understanding of EEJ behaviors during SAPS periods and their implications for modeling and forecasting the equatorial space environment.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Geosciences, Multidisciplinary
Brian J. Harding, Yen-Jung Joanne Wu, Patrick Alken, Yosuke Yamazaki, Colin C. Triplett, Thomas J. Immel, L. Claire Gasque, Stephen B. Mende, Chao Xiong
Summary: The eruption of the Hunga Tonga-Hunga Ha'apai volcano on January 15, 2022 caused atmospheric waves. Observations from the ICON and Swarm satellites showed that the eruption had an impact on the ionospheric wind dynamo, leading to changes in the equatorial electrojet and neutral winds. These findings suggest that the dynamo plays a key role in the ionospheric response to volcanic disturbances.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Y. Yamazaki, J. Matzka, C. Stolle, G. Kervalishvili, J. Rauberg, O. Bronkalla, A. Morschhauser, S. Bruinsma, Y. Y. Shprits, D. R. Jackson
Summary: The study introduces a new geomagnetic activity index Hpo, which has higher time resolution and can accurately characterize severe geomagnetic storms compared to the traditional index Kp.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Yosuke Yamazaki
Summary: This paper describes the solar and lunar daily variations of the geomagnetic field in low- and mid-latitude regions using data from the Swarm satellites. The study finds that these variations are mainly of internal origin and can be attributed to ionospheric dynamo currents and induced underground currents. The global patterns of the internal solar and lunar current systems are consistent with previous ground observations.
EARTH PLANETS AND SPACE
(2022)
Article
Geosciences, Multidisciplinary
Sahar Sobhkhiz-Miandehi, Yosuke Yamazaki, Christina Arras, Yasunobu Miyoshi, Hiroyuki Shinagawa
Summary: This research investigates the role of atmospheric solar and lunar tides in the occurrence of sporadic E layers. The results show that both migrating and non-migrating solar tidal signatures, as well as the semidiurnal migrating lunar tidal signature, significantly affect the Es occurrence rate.
EARTH PLANETS AND SPACE
(2022)
Article
Geosciences, Multidisciplinary
Tarique A. Siddiqui, Jorge L. Chau, Claudia Stolle, Yosuke Yamazaki
Summary: This study investigates the variability of the migrating solar diurnal (DW1) tide in the mesosphere-lower thermosphere (MLT) region during Northern and Southern Hemisphere Sudden Stratospheric Warmings (SSWs) using temperature observations and simulations. The DW1 tide displays a reduction in amplitude at low-latitudes after the onset of SSWs in both observations and simulations. The simulations suggest that changes in the latitudinal shear of zonal winds in the MLT during SSWs could explain the observed variability of the DW1 tide.
EARTH PLANETS AND SPACE
(2022)
Article
Astronomy & Astrophysics
Yosuke Yamazaki, Gabriel Soares, Jurgen Matzka
Summary: Modeling studies have predicted that geophysical events like earthquakes and volcanos can cause acoustic resonance in the atmosphere, leading to oscillation of the geomagnetic field. However, observations of this phenomenon have been limited. A recent submarine volcano eruption in the Pacific Ocean provided an opportunity to investigate geomagnetic effects associated with acoustic resonance. The eruption resulted in geomagnetic oscillations, primarily in the Pc 5 band, at a location approximately 835 km away, confirming the presence of atmospheric oscillation due to acoustic resonance.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Gabriel Soares, Yosuke Yamazaki, Achim Morschhauser, Jurgen Matzka, Katia J. Pinheiro, Claudia Stolle, Patrick Alken, Akimasa Yoshikawa, Kornyanat Hozumi, Atul Kulkarni, Pornchai Supnithi
Summary: This study proposes a new technique for modeling the equatorial electrojet (EEJ) based on principal component analysis (PCA) and compares its performance with existing models. By using ground-satellite geomagnetic data, the researchers successfully determine the amplitudes of solar tides and find a remarkable correlation between tidal signatures in the EEJ and tidal signatures derived from neutral atmosphere temperature observations. The results of the study suggest that meaningful EEJ spectra related to solar tides can be obtained even with relatively short observation periods.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2022)
Article
Astronomy & Astrophysics
Y. Yamazaki, B. J. Harding, L. Qiu, C. Stolle, T. A. Siddiqui, Y. Miyoshi, C. R. Englert, S. L. England
Summary: This paper presents the monthly climatology of zonal-mean winds and tides based on the v05 ICON/MIGHTI data and compares it with the HWM14 model. The results show good agreement between ICON/MIGHTI and HWM14, but larger amplitudes of lower thermospheric tides are observed in ICON/MIGHTI, suggesting the need for improvements in the tidal representation of HWM14.
EARTH AND SPACE SCIENCE
(2023)
Article
Astronomy & Astrophysics
Lihui Qiu, Yosuke Yamazaki, Tao Yu, Yasunobu Miyoshi, Xiaomin Zuo
Summary: Previous studies have used various physical parameters as indicators of Es layer height, but this study found that vertical ion velocity null (IVN) most accurately represents the height of Es layer over Wuhan. The simulation results also suggest that the vertical gradient of the ratio of ion-neutral collision frequency to ion gyrofrequency affects the formation of Es layer at lower altitudes. Additionally, the effect of electric fields on the height and intensity of Es layers was examined, showing that eastward/upward electric fields can lift the Es layer height and reduce intensity.
JOURNAL OF GEOPHYSICAL RESEARCH-SPACE PHYSICS
(2023)
Article
Astronomy & Astrophysics
Lihui Qiu, Yosuke Yamazaki, Tao Yu, Erich Becker, Yasunobu Miyoshi, Yifan Qi, Tarique A. Siddiqui, Claudia Stolle, Wuhu Feng, John M. C. Plane, Yu Liang, Huixin Liu
Summary: The modulation of sporadic E (Es) layers by gravity waves (GWs) is examined through numerical simulations in this paper. It is found that the inclusion of GWs leads to short-period density perturbations in Es layers, and the effect on metallic ion density varies with altitude and longitude. The geographical distribution of GWs activity in the mesosphere and lower thermosphere region plays a primary role in the longitudinal variation of metallic ion density.
EARTH AND SPACE SCIENCE
(2023)
Article
Astronomy & Astrophysics
Juliana Jaen, Toralf Renkwitz, Jorge L. Chau, Maosheng He, Peter Hoffmann, Yosuke Yamazaki, Christoph Jacobi, Masaki Tsutsumi, Vivien Matthias, Chris Hall
Summary: This study investigates the mesospheric winds and zonal geostrophic winds over Germany and northern Norway using specular meteor radars and partial reflection radars. The results show significant year-to-year variability in the summer beginning, especially at high latitudes. The mesosphere summer length exhibits an increasing trend over the years, while the length of summer in the mesosphere and lower-thermosphere does not show a well-defined trend. The study also explores possible influences of solar activity and large-scale atmospheric phenomena on the summer length.
ANNALES GEOPHYSICAE
(2022)
