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

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 

机构地区：[1]Space Research Institute,Austrian Academy of Sciences,8042 Graz,Austria [2]Geophysical Institute,University of Alaska Fairbanks,Fairbanks,Alaska 99775,USA [3]National Aeronautics and Space Administration(NASA)Goddard Space Flight Center,Greenbelt,Maryland 20771,USA [4]Astronomy Department,University of Maryland College Park,College Park,Maryland 20742,USA [5]Center for Space Physics,Boston University,Boston,Massachusetts 02215,USA [6]Department of Physics and Astronomy,Johns Hopkins University,Baltimore,Maryland 21218,USA [7]Howard University,Washington,DC 20059,USA

出　　处：《Earth and Planetary Physics》2024年第1期173-183,共11页地球与行星物理（英文版）

基　　金：supported by NASA(Grant Nos.80NSSC19K0844,80NSSC20K1670,80MSFC20C0019,and 80GSFC21M0002);support from NASA Goddard Space Flight Center internal funding programs(HIF,Internal Scientist Funding Model,and Internal Research and Development)。

摘　　要：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 of<0.3 RE when the solar wind density exceeds>10 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 c

关 键 词：soft X-ray MAGNETOPAUSE RECONNECTION low-pass filter LEXI SMILE 

分 类 号：P172.2[天文地球—天文学]