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Estimating the subsolar magnetopause position from soft X-ray images using a low-pass image filter

Earth and Planetary Physics 2024年第1期8卷 173-183页

作者： Hyangpyo Kim Hyunju K.Connor Jaewoong Jung Brian M.Walsh David Sibeck Kip D.Kuntz Frederick S.Porter Catriana K.Paw U Rousseau A.Nutter Ramiz Qudsi rumi nakamura Michael Collier Space Research Institute Austrian Academy of Sciences8042 GrazAustria Geophysical Institute University of Alaska FairbanksFairbanksAlaska 99775USA National Aeronautics and Space Administration(NASA)Goddard Space Flight Center GreenbeltMaryland 20771USA Astronomy Department University of Maryland College ParkCollege ParkMaryland 20742USA Center for Space Physics Boston UniversityBostonMassachusetts 02215USA Department of Physics and Astronomy Johns Hopkins UniversityBaltimoreMaryland 21218USA Howard University WashingtonDC 20059USA

The Lunar Environment heliospheric X-ray Imager(LEXI)and Solar wind Magnetosphere Ionosphere Link Explorer(SMILE)missions will image the Earth’s dayside magneto pause and cusps in soft X-rays after their respective launches in the near future,to specify glo bal magnetic reconnection modes for varying solar wind conditions.To suppo rt the success of these scientific missions,it is critical to develop techniques that extract the magnetopause locations from the observed soft X-ray images.In this research,we introduce a new geometric equation that calculates the subsolar magnetopause position(RS)from a satellite position,the look direction of the instrument,and the angle at which the X-ray emission is maximized.Two assumptions are used in this method:(1)The look direction where soft X-ray emissions are maximized lies tangent to the magnetopause,and(2)the magnetopause surface near the subsolar point is almost spherical and thus RSis nea rly equal to the radius of the magneto pause curvature.We create synthetic soft X-ray images by using the Open Geospace General Circulation Model(OpenGGCM)global magnetohydrodynamic model,the galactic background,the instrument point spread function,and Poisson noise.We then apply the fast Fourier transform and Gaussian low-pass filte rs to the synthetic images to re move noise and obtain accurate look angles for the soft X-ray pea ks.From the filte red images,we calculate RS and its accuracy for different LEXI locations,look directions,and solar wind densities by using the OpenGGCM subsolar magnetopause location as ground truth.Our method estimates RS with an accuracy of10 cm-3.The accuracy improves for greater solar wind densities and during southward interplanetary magnetic fields.The method ca ptures the magnetopause motion during southwa rd interplaneta ry magnetic field turnings.Consequently,the technique will enable quantitative analysis of the magnetopause motion and help reveal the dayside reconnection modes for dynamic solar wind con

关键词： soft X-ray magnetopause reconnection low-pass filter LEXI SMILE

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Observation of multiple sub-cavities adjacent to single separatrix

Observation of multiple sub-cavities adjacent to single sepa...

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中国科学院地质与地球物理研究所2013年度（第13届）...

作者： Rongsheng Wang Aimin Du rumi nakamura Quanming Lu Yuri V.Khotyaintsev Martin Volwerk Tielong Zhang E.A.Kronberg P.W.Daly Andrew N.Fazakerley Key Laboratory of Ionospheric Environment Institute of Geology and GeophysicsChinese Academy of Sciences Space Research Institute Austrian Academy of SciencesGrazAustria Department of Geophysics and Planetary Science University of Science and Technology of China

[1]We investigate a direct south-north crossing of a reconnection ion diffusion region in the magnetotail. During this crossing,multiple electron density dips with a further density decrease within the cavity,called subcavities, adjacent to the northern separatrix are observed. The correlation between electron density sub-cavities and strong electric field fluctuations is obvious.Within one of the sub-cavities,a series of very strong oscillating perpendicular electric field and patchy parallel electric field are observed.The parallel electric field is nearly unipolar and directs away from X line.In the same region,inflow electrons with energy up to 100 keV are injected into the X line.Based on the observations,we conclude that the highenergy inflowing electrons are accelerated by the patchy parallel electric field.Namely,electrons have been effectively accelerated while they are flowing into the X

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Observation of double layer in the separatrix region during magnetic reconnection

Observation of double layer in the separatrix region during ...

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中国科学院地质与地球物理研究所2014年度（第14届）...

作者： Rongsheng Wang Quanming Lu Yuri V.Khotyaintsev Martin Volwerk Aimin Du rumi nakamura Walter D.Gonzalez Xuan Sun Wolfgang Baumjohann Xing Li Tielong Zhang Andrew N.Fazakerley Can Huang Mingyu Wu Key Laboratory of Earth and Planetary Physics Institute of Geology and GeophysicsChinese Academy of Sciences Department of Geophysics and Planetary Science University of Science and Technology of China Swedish Institute of Space Physics Space Research Institute Austrian Academy of Sciences

We present in situ observation of double layer(DL) and associated electron measurement in the subspin time resolution in the separatrix region during reconnection for the first time.The DL is inferred to propagate away from the X line at a velocity of about ion acoustic speed and the parallel electric field carried by the DL can reach-20 mV/m.The electron displays a beam distribution inside the DL and streams toward the X line with a local electron Alfven velocity.A series of electron holes moving toward the X line are observed in the wake of the DL.The identification of multiple similar DLs indicates that they are persistently produced and therefore might play an important role in energy conversion during reconnection.The observation suggests that energy dissipation during reconnection can occur in any region where the DL can reach.

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