DOI: 10.1029/2017JA024957
Scopus记录号: 2-s2.0-85047647349
论文题名: Empirical Characterization of Low-Altitude Ion Flux Derived from TWINS
作者: Goldstein J. ; LLera K. ; McComas D.J. ; Redfern J. ; Valek P.W.
刊名: Journal of Geophysical Research: Space Physics
ISSN: 21699380
出版年: 2018
卷: 123, 期: 5 起始页码: 3672
结束页码: 3691
语种: 英语
英文关键词: energetic neutral atom
; global imaging
; ion
; precipitation
; ring current
; TWINS
英文摘要: In this study we analyze ion differential flux from 10 events between 2008 and 2015. The ion fluxes are derived from low-altitude emissions (LAEs) in energetic neutral atom (ENA) images obtained by Two Wide-angle Imaging Neutral-atom Spectrometers (TWINS). The data set comprises 119.44 hr of observations, including 4,284 per energy images with 128,277 values of differential ENA flux from pixels near Earth's limb. Limb pixel data are extracted and mapped to a common polar ionospheric grid and associated with values of the Dst index. Statistical analysis is restricted to pixels within 10% of the LAE emissivity peak. For weak Dst conditions we find a premidnight peak in the average ion precipitation, whose flux and location are relatively insensitive to energy. For moderate Dst, elevated flux levels appear over a wider magnetic local time (MLT) range, with a separation of peak locations by energy. Strong disturbances bring a dramatic flux increase across the entire nightside at all energies but strongest for low energies in the postmidnight sector. The arrival of low-energy ions can lower the average energy for strong Dst, even as it raises the total integral number flux. TWINS-derived ion fluxes provide a macroscale measurement of the average precipitating ion distribution and confirm that convection, either quasi-steady or bursty, is an important process controlling the spatial and spectral properties of precipitating ions. The premidnight peak (weak Dst), MLT widening and energy-versus-MLT dependence (moderate Dst), and postmidnight low-energy ion enhancement (strong Dst) are consistent with observations and models of steady or bursty convective transport. ©2018. American Geophysical Union. All Rights Reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/113993
Appears in Collections: 气候减缓与适应
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作者单位: Space Science and Engineering Division, Southwest Research Institute, San Antonio, TX, United States; Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX, United States; Department of Astrophysical Sciences, Princeton University, Princeton, NJ, United States
Recommended Citation:
Goldstein J.,LLera K.,McComas D.J.,et al. Empirical Characterization of Low-Altitude Ion Flux Derived from TWINS[J]. Journal of Geophysical Research: Space Physics,2018-01-01,123(5)