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North-South Asymmetry of the interplanetary magnetic field Magnitude and the Geomagnetic Indices

International Journal of Astronomy and Astrophysics 2016年第1期6卷 14-22页

作者： Mohammed Ali El-Borie Ali Abdel-Moniem Abdel-Halim Shady Yousry El-Monier Physics Department Faculty of Science Alexandria University Alexandria Egypt Arab Academy for Science & Technology and Maritime Transport Alexandria Egypt

Data of the daily interplanetary magnetic field (IMF), and the geomagnetic indices (aa, Ap, Kp, and DST) have been used to examine the asymmetry between the solar field north and south of the heliospheric current sheet, over the period (1975-2013). It important to note that during the positive polarity epochs: (T) refers to Toward the South of the heliospheric current sheet (Southern Hemisphere), and (A) refers to Away from North of the heliospheric current sheet (Northern Hemisphere). While, during the negative polarity epochs the opposite will be happened. The present study finds no clear indication of the presence of north-south asymmetry in the field magnitude, and also there is no magnetic solar cycle dependence that is evident. During the considered period, the north-south asymmetry for the considered parameters reaches maximum values around the declining phase or near to the minimum of the solar cycle. The geomagnetic indices have a clear asymmetry during the positive solar magnetic polarity period (qA > 0) and have a northern dominance during cycles (22 & 23) and southern dominance during cycles (21 & 24). From the power spectrum density, the considered parameters showed significant peaks which appeared in the north-south asymmetry but the 10.7 yr solar cycle was absent. In addition, the main periodicity of the asymmetry may be 5.2, 4.0 and 3.3 years that exist in the parameters with higher confidence levels. Finally, one can conclude that the asymmetry of the interplanetary parameters and the geomagnetic indices may provide multiple causes for producing the observed asymmetric modulations of cosmic rays.

关键词： Geomagnetic Indices interplanetary magnetic field North-South Asymmetry Solar Activity Distribution

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Distinct MLT asymmetry of auroral kilometric radiation observed by the FAST satellite

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Earth and Planetary Physics 2025年第1期9卷 188-193页

作者： JiaWen Tang Sai Zhang FuLiang Xiao HongMing Yang Si Liu YiHua He Chang Yang YuYue Jin ZhouKun Deng Ping Li Archie James Johnston School of Physics and Electronic Sciences Changsha University of Science and TechnologyChangsha 410114China Hunan Province Higher Education Key Laboratory of Modeling and Monitoring on the Near-Earth Electromagnetic Environments Changsha University of Science and TechnologyChangsha 410114China School of Electrical and Information Engineering Changsha University of Science and TechnologyChangsha 410114China

Auroral Kilometric Radiation (AKR) is a common radio emission,which can contribute to the magnetosphere-ionosphereatmosphere co u *** emissions have been observed in all magnetic planet magnetospheres of the solar *** this study,using observations from the FAST satellite from 30 August 1996 to 9 September 2001,the distribution of AKR in altitude=500-4500 km and invariant latitude (|ILAT|)=60°-80°has been analyzed.63045 AKR samples have been identified with~48%(52%) samples on the dayside (nightside).Of considerable interest,there is a distinct MLT asymmetry with the high occurrence rate in MLT=05-08 and 18-22(02-05 and 12-17) in the northern (southern) *** distinct MLT asymmetry is associated with the direction of Bxof the interplaneta ry magnetic *** addition,the occurrence rate on the nightside clearly increases as the AE^(*) index *** study further enriches the information and understanding of AKR in the magnetosphere as well as other similar radio emissions.

关键词： asymmetry auroral kilometric radiation interplanetary magnetic field

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The semiannual variation of transpolar arc incidence and its relationship to the Russell–McPherron effect

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Earth and Planetary Physics 2020年第6期4卷 619-626页

作者： Tao Tang Jun Yang QuanQi Shi AnMin Tian Shi-Chen Bai Alexander William Degeling SuiYan Fu JingXian Liu Tong Shao ZeYuan Sun Shandong Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment School of Space Science and PhysicsInstitute of Space SciencesShandong UniversityWeihai Shandong 264209China Institute of Space Physics and Applied Technology Peking UniversityBeijing 100871China

Earth’s aurora is a luminescent phenomenon generated by the interaction between magnetospheric precipitating particles and the upper atmosphere;it plays an important role in magnetosphere–ionosphere(M-I)*** transpolar arc(TPA)is a discrete auroral arc distributed in the noon-midnight direction poleward of the auroral oval and connects the dayside to the nightside sectors of the auroral *** the seasonal variation of TPA events can help us better understand the long-term variation of the interaction between the solar wind,the magnetosphere,and M-I ***,a statistical study of the seasonal variation of TPA incidence has not previously been carried *** this paper,we have identified 532 TPA events from the IMAGE database(2000–2005)and the Polar database(1996–2002),and calculated the incidence of TPA events for different *** find a semiannual variation in TPA *** peaks in the incidence of TPAs occur in March and September;a less pronounced peak appears in *** also examine seasonal variation in the northward interplanetary magnetic field(IMF)over the same time *** intensity and occurrence rate of the northward IMF exhibit patterns similar to that of the TPA *** studied IMF Bz before TPA onset,we find that strong and steady northward IMF conditions are favorable for TPA *** suggest that the semiannual variation observed in TPA incidence may be related to the Russell–McPherron(R-M)effect due to the projection effect of the IMF By under northward IMF conditions.

关键词： transpolar arc incidence interplanetary magnetic field Russell-McPherron effect semiannual variation

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magnetic Storm Effects in the Auroral Ionosphere Observed with EISCAT Radar-Two Case Studies

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Wuhan University Journal of Natural Sciences 2000年第2期5卷 181-186页

作者： Liu Hui-xin Ma Shu-ying K. Schlegel Wuhan University College of Electronic Information Wuhan China (GRID:grid.49470.3e) (ISNI:***) Max-Planck Institut für Aeronomie Katlenburg-Lindau Germany (GRID:grid.450267.2) Wuhan University College of Electronic Information Wuhan China (GRID:grid.49470.3e) (ISNI:***) the Chinese Academy of Sciences Wuhan Ionospheric Observatory Wuhan Institute of Physics and Mathematics Wuhan China (GRID:grid.9227.e) (ISNI:***) the Chinese Academy of Sciences Wuhan Ionospheric Observatory Wuhan Institute of Physics and Mathematics Wuhan China (GRID:grid.9227.e) (ISNI:***)

Storm-time changes of main plasma parameters in the auroral ionosphere are analyzed for two intense storms occurring on May 15, 1997 and Sept. 25, 1998, with emphasis on their relationship to the solar wind dynamic pressure and the IMFB z component. Strong hard particle precipitation occurred in the initial phase for both storms, associated with high solar wind dynamical pressure. During the recovery phase of the storms, some strong particle precipitation was neither concerned with high solar wind pressure nor southward IMFB z. Severe negative storm effects depicted by electron density depletion appeared in theF-region during the main and recovery phase of both storms, caused by intensive electric field-related strong Joule/frictional heating when IMF was largely southward. The ion temperature behaved similarly inE-andF-region, but the electron temperature did quite different, with a strong increase in the lowerE-region relating to plasma instability excited by strong electric field and a slight decrease in theF-region probably concerning with a cooling process. The field-aligned ion velocity was high and apparently anticorrelated with the northward component of the ion convection velocity.

关键词： magnetic storm auroral ionosphere interplanetary magnetic field particle precipitation Joule heating

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Global distributions of storm-time ionospheric currents as seen in geomagnetic field variations

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Advances in Polar Science 2013年第4期24卷 296-314页

作者： Atsuki Shinbori Tomoaki Hori Yoshimasa Tanaka Yukinobu Koyama Takashi Kiku-chi Tsutomu Nagatsuma Research Institute for Sustainable Humanosphere GokashoUjiKyoto 611-0011Japan Solar-Terrestrial Environment Laboratory Nagoya UniversityFurou-choChikusa-kuNagoyaAichi 464-8614Japan National Institute of Polar Research 10-3 Midori-choTachikawaTokyo 190-8518Japan Data Analysis Center for Geomagnetism and Space Magnetism Graduate School of ScienceKyoto UniversityKitashi-rakawa-Oiwake ChoSakyo-kuKyoto 606-8502Japan National Institute of Information and Communications Technology 4-2-1NukuikitamachiKoganeiTokyo 184-0015Japan

To investigate temporal and spatial evolution of global geomagnetic field variations from high-latitude to the equator during geomagnetic storms, we analyzed ground geomagnetic field disturbances from high latitudes to the magnetic equator. The daytime ionospheric equivalent current during the storm main phase showed that twin-vortex ionospheric currents driven by the Region 1 field-aligned currents （R1 FACs） are intensified significantly and expand to the low-latitude region of-30~ magnetic latitude. Centers of the currents were located around 70~ and 65~ in the morning and afternoon, respectively. Corresponding to intensification of the R1 FACs, an enhancement of the eastward/westward equatorial electrojet occurred at the daytime/nighttime dip equator. This signature suggests that the enhanced convection electric field penetrates to both the daytime and nighttime equa- tor. During the recovery phase, the daytime equivalent current showed that two new pairs of twin vortices, which are different from two-cell ionospheric currents driven by the R1 FACs, appear in the polar cap and mid latitude. The former led to enhanced north- ward Bz （NBZ） FACs driven by lobe reconnection tailward of the cusps, owing to the northward interplanetary magnetic field （IMF）. The latter was generated by enhanced Region 2 field-aligned currents （R2 FACs）. Associated with these magnetic field variations in the mid-latitudes and polar cap, the equatorial magnetic field variation showed a strongly negative signature, produced by the westward equatorial electrojet current caused by the dusk-to-dawn electric field.

关键词： solar wind interplanetary magnetic field geomagnetic storm convection electric field field-alignedcurrents equatorial electrojet NBZ FAC system

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