ISSN  2096-3955

CN  10-1502/P

2017 Vol.1(1)

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Earth science, planetary vision——A foreword to Earth and Planetary Physics (EPP)
WeiXing Wan
2017, 1(1): 1-1. doi: 10.26464/epp2017001
Corotating drift-bounce resonance of plasmaspheric electron with poloidal ULF waves
Qiu-Gang Zong, YongFu Wang, Jie Ren, XuZhi Zhou, SuiYan Fu, Robert Rankin, Hui Zhang
2017, 1(1): 2-12. doi: 10.26464/epp2017002
The purpose of this paper is to understand how low energy plasmaspheric electrons respond to ULF waves excited by interplanetary shocks impinging on magnetosphere. It is found that both energy and pitch angle dispersed plasmaspheric electrons with energy of a few eV to tens of eV can be generated simultaneously by the interplanetary shock. The subsequent period of successive dispersion signatures is around 40 s and is consistent with the ULF wave period (third harmonic). By tracing back the energy and pitch angle dispersion signatures, the position of the electron injection region is found to be off-equator at around –32° in the southern hemisphere. This can be explained as the result of injected electrons being accelerated by higher harmonic ULF waves (e.g. third harmonic) which carry a larger amplitude electric field off-equator. The dispersion signatures are due to the flux modulations (or accelerations) of " local” plasmaspheric electrons rather than electrons from the ionosphere. With the observed wave-borne large electric field excited by the interplanetary shock impact, the kinetic energy can increase to a maximum of 23 percent in one bouncing cycle for plasmaspheric electrons satisfying the drift-bounce resonance condition by taking account of both the corotating drift and bounce motion of the local plasmaspheric electron.
Ambient noise surface wave tomography of marginal seas in east Asia
Qing Wang, XiaoDong Song, JianYe Ren
2017, 1(1): 13-25. doi: 10.26464/epp2017003
We conducted ambient noise tomography in east Asia, including the Chinese coastal provinces, Korea Peninsular, Japan, Taiwan Island, and marginal seas in between. We retrieved Rayleigh Green’s functions from inter-station correlations of 12 months of continuous waveform data at 573 broadband stations in the region. We obtained group and phase velocity dispersion curves and dispersion maps for periods from 10 to 70 s and inverted for 3D Vs model of the crust and uppermost mantle. Moho and lithosphere thickness were derived from the 3D model. We observed three prominent low velocity zones in the upper mantle, two in the accretionary wedges above the Pacific and Philippine subduction slabs and one beneath the Changbai Mountain region. The crust and lithosphere are generally thin in the region. The velocity anomalies, crustal thickness, and lithosphere thickness all show a similar trend in NNE-SSW direction. The lithosphere shows a striking " sausage”-type structure with alternating thickness. The crust thickness and lithosphere thickness both decrease progressively from NW to SE direction, which coincides with the distribution of episodic magmatism in SE China. We propose that the subduction of paleo-Pacific slab and its rollback were mainly responsible for the crustal and lithosphere extension and the mantle lithosphere removal in east Asia.
A seismic model for crustal structure in North China Craton
TianYu Zheng, YongHong Duan, WeiWei Xu, YinShuang Ai
2017, 1(1): 26-34. doi: 10.26464/epp2017004
We present a digital crustal model in North China Craton (NCC). The construction of crustal model is based on digitization of original seismic sounding profiles, and new results of three-dimensional structure images of receiver functions. The crustal model includes seismic velocity and thickness of crustal layers. The depths to Moho indicate a thinning crust ~30 km in the east areas and a general westward deepening to more than 40 km in the west. The P wave velocity varies from 2.0 to 5.6 km/s in the sedimentary cover, from 5.8 to 6.4 km/s in the upper crust, and from 6.5 to 7.0 km/s in the lower crust. By analyzing regional trends in crustal structure and links to tectonic evolution illustrated by typical profiles, we conclude that: (1) The delimited area by the shallowing Moho in the eastern NCC represents the spatial range of the craton destruction. The present structure of the eastern NCC crust retains the tectonic information about craton destruction by extension and magmatism; (2) The tectonic activities of the craton destruction have modified the crustal structure of the convergence boundaries at the northern and southern margin of the NCC; (3) The Ordos terrene may represent a relatively stable tectonic feature in the NCC, but with the tectonic remnant of the continental collision during the assembly of the NCC in the north-east area and the response to the lateral expansion of the Tibetan Plateau during the Cenozoic in the south-west.
Correlations between plasmapause evolutions and auroral signatures during substorms observed by Chang’e-3 EUV Camera
XiaoXin Zhang, Fei He, Bo Chen, Chao Shen, HuaNing Wang
2017, 1(1): 35-43. doi: 10.26464/epp2017005
The plasmapause locations determined from the Chang’e-3 (CE-3) Extreme Ultraviolet Camera (EUVC) images and the auroral boundaries determined from the Defense Meteorological Satellite Program (DMSP) Special Sensor Ultraviolet Spectrographic Imager (SSUSI) images are used to investigate the plasmaspheric evolutions during substorms. The most important finding is a nightside pointing plasmaspheric plume observed at 23:05 UT on 21 April 2014 under quiet solar wind and geomagnetic conditions, which drifted from the dusk sector. High correlations between the plasmapause evolutions and the auroral signatures exist during substorms. After substorm onset, the plasmapause erosion and the equatorward expansion of the auroral oval occur almost simultaneously in both MLT and UT, and then both the erosion and the expansion propagate westward and eastward. It is suggested that the plasmaspheric erosion and its MLT propagations are induced by the enhanced earthward plasma convection during substorm period, and the substorm dipolarization causes pitch-angle scattering of plasma sheet electrons and the resulting precipitation excites aurora emissions at the same time.
A simulation study of 630 nm and 557.7 nm airglow variations due to dissociative recombination and thermal electrons by high-power HF heating
Tong Dang, JiuHou Lei, XianKang Dou, WeiXing Wan
2017, 1(1): 44-52. doi: 10.26464/epp2017006
One of the important effects of the ionospheric modification by high-power waves is the airglow enhancement. Both the thermal electrons and the dissociation recombination contribute to generate the airglow emissions during HF heating. However, the relative importance of the airglow emission induced by dissociative recombination and thermal electrons has been rarely investigated. In this study, we carry out a simulation study on the airglow produced by high-power HF heating at nighttime associated with dissociative recombination and thermal electrons. SAMI2 (Sami2 is Another Model of the Ionosphere) is employed to simulate the ionospheric variations during the HF heating. The main conclusions from this study are as follows: (1) For the airglow induced by dissociative recombination, both 630.0 nm and 557.7 nm emissions show a decrease at the heating wave reflection height during the heating period, while when the heating is turned off, an increase is shown at lower altitudes. The reduction of airglow during the heating is caused by the rapid increase of electron temperature and the diffusion of plasmas dominates the after-heating airglow enhancement. (2) 630.0 nm emission due to thermal electrons is greatly enhanced at the wave reflection height, indicating that thermal electrons play a major role in exciting 630.0 nm emission. For the 557.7 nm emission, the excitation threshold (4.17 eV) is too high for thermal electrons. (3) The combined effect of dissociative recombination and thermal electrons could be the possible reason for the observed X-mode (extraordinary mode) suppression of 630.0 nm airglow during O-mode (ordinary mode) enhancement.
Observations of loading-unloading process at Saturn’s distant magnetotail
ZhongHua Yao
2017, 1(1): 53-57. doi: 10.26464/epp2017007
Using in-situ measurements from the Cassini spacecraft in 2013, we report an Earth substorm-like loading-unloading process at Saturn’s distant magnetotail. We found that the loading process is featured with two distinct processes: a rapid loading process that was likely driven by an internal source and a slow loading process that was likely driven by solar wind. Each of the two loading processes could also individually lead to an unloading process. The rapid internal loading process lasts for ~ 1-2 hours; the solar wind driven loading process lasts for ~ 3-18 hours and the following unloading process lasts for ~1-3 hours. In this letter, we suggest three possible loading-unloading circulations, which are fundamental in understanding the role of solar wind in driving giant planetary magnetospheric dynamics.
Exact local refinement using Fourier interpolation for nonuniform-grid modeling
JinHai Zhang, ZhenXing Yao
2017, 1(1): 58-62. doi: 10.26464/epp2017008
Numerical solver using a uniform grid is popular due to its simplicity and low computational cost, but would be unfeasible in the presence of tiny structures in large-scale media. It is necessary to use a nonuniform grid, where upsampling the wavefield from the coarse grid to the fine grid is essential for reducing artifacts. In this paper, we suggest a local refinement scheme using the Fourier interpolation, which is superior to traditional interpolation methods since it is theoretically exact if the input wavefield is band limited. Traditional interpolation methods would fail at high upsampling ratios (say 50); in contrast, our scheme still works well in the same situations, and the upsampling ratio can be any positive integer. A high upsampling ratio allows us to greatly reduce the computational burden and memory demand in the presence of tiny structures and large-scale models, especially for 3D cases.
A planetary perspective on Earth’s space environment evolution
Yong Wei, XinAn Yue, ZhaoJin Rong, YongXin Pan, WeiXing Wan, RiXiang Zhu
2017, 1(1): 63-67. doi: 10.26464/epp2017009
The planet Earth is an integrated system, in which its multi-spheres are coupled, from the space to the inner core. Whether the space environment in short to long terms has been controlled by the earth’s interior process is contentious. In the past several decades, space weather and space climate have been extensively studied based on either observation data measured directly by man-made instruments or ancient data inferred indirectly from some historical medium of past thousands of years. The acquired knowledge greatly helps us to understand the dynamic processes in the space environment of modern Earth, which has a strong magnetic dipole and an oxygen-rich atmosphere. However, no data is available for ancient space weather and climate (>5 ka). Here, we propose to take the advantage of " space-diversity” to build a " generalized planetary space family”, to reconcile the ancient space environment evolution of planet Earth from modern observations of other planets in our solar system. Such a method could also in turn give us a valuable insight into other planets’ evolution.
Observations of the solar corona during the total solar eclipse on 21 August 2017
Hui Tian, ZhongQuan Qu, YaJie Chen, LinHua Deng, ZhengHua Huang, Hao Li, Yue Zhong, Yu Liang, JingWen Zhang, YiGong Zhang, BaoLi Lun, XiangMing Cheng, XiaoLi Yan, ZhiKe Xue, YuXin Xin, ZhiMing Song, YingJie Zhu, Tanmoy Samanta
2017, 1(1): 68-71. doi: 10.26464/epp2017010
Monitoring the geospace response to the Great American Solar Eclipse on 21 August 2017
Shun-Rong Zhang, Philip J. Erickson, Larisa P. Goncharenko, Anthea J. Coster, Nathaniel A. Frissell
2017, 1(1): 72-76. doi: 10.26464/epp2017011