========================================================================= National Space Science Data Center 5 May 1997 ========================================================================= NAME THE EQUATORIAL-NEUTRAL SHEET SOFTWARE SCIENTIFIC CONTACT Ronglan XU and Lei LI Center for Space Sci. and Applied Res., Chinese Academy of Science, PO Box 8701, Beijing 100080, China Internet: XURL@SUN20.CSSAR.AV.CN, XURL@SUN.IHEP.AC.CN (April 15, 1997) NSSDC CONTACT N. Papitashvili, NASA/GSFC/NSSDC, code 633/STX, Greenbelt, Maryland 20771, U.S.A., DECNET: NCF::NATASHA INTERNET: natasha@nssdca.gsfc.nasa.gov CONTENT: Name Comments -------------------------------------------------------------------------- AEN.FOR Finds the AEN (Analytical Equatorial Neutral) sheet in the magnetopause in different time and position DEN.FOR Finds the DEN (Displaced Equatorial Neutral) sheet inside the magnetopause in different tine and positions SEN.FOR Finds the SEN (Standard Equatorial Neutral) sheet inside the magnetopause in different time and position AAREADME.DOC This file -------------------------------------------------------------------------- BRIEF DESCRIPTION: The average configuration of the geomagnetotail has been deduced from numerous spacecrafts measurements. These lobes are separated by the neutral sheet. The position of the neutral sheet varies with time, and can only be definitely known at the instant a spacecraft traverses the reversal region of the magnetic field. Numerous studies (Fairfield 1980 and references there in) have shown that the annual and diurnal changes of the tilt angle between the earth-sun line and the subsolar point induce significant movements of the neutral sheet away from the solar magnetospheric XY plane. According to the previous neutral sheet models, there remains a varying discontinuous region between neutral sheet and the equatorial plane of the tilted geomagnetic dipole field. A Standard Equatorial-Neutral sheet (SEN) model (Xu, 1992), a Displaced Equatorial-Neutral sheet (DEN) model (Xu, 1991) and an Analytical Equatorial-Neutral sheet (AEN) model (Xu et al., 1993, Zhu and Xu, 1994 and Wang and Xu, 1994) inside the magnetopause (Sibeck et al., 1991) are developed. In these three Equatorial-Neutral Sheet models the tilted equatorial plane joints smoothly to the neutral sheet, so that they can be used in the whole magnetosphere regions, including in the near tail region. The SEN and DEN models contain of 3 different complicate equations. The AEN model is expressed by one simple equation and remain approximately the general characteristic of the DEN Model. Based on the AEN model, a normal curve coordinate system is set up, in which the AEN sheet becomes one of the coordinate surface. This coordinate system will change with the Earth's tilt angle,and thus can almost offset the titled effect on the pattern of the geomagnetic field on the Magnetotail (Zhu and XU, 1994). THE SOFTWARE This packege contains the FORTRAN 77 source codes (*.FOR) of SEN, DEN and AEN. They compute the position of SEN sheet along Zsm, at a given point Xsm and Ysm inside the magnetopause at different dates and times, The input and output of these software are: The Input are: DATE, TIME, XSM, YSM, ZSM. Where DATE and TIME are expressed in the following 2 different format, and XSM, YSM, ZSM is the position in GSM Coordinate System. (1) When Date is Year and DOY (Day Of Year), and Time is Second of Day (SD). For example: Year=1995, DOY=34, SD=35000, then Date is 95034 and SD is 35000 (2) When Date is Year/Month/Day, and Time is Hour/Minute/Second. For example: February 3, 1995, 2 Hour 5 minute and 10 second, then Date is 950203, and Time is 020520. The output are ZSEN (ZDEN or ZAEN) and IE. Where ZSEN (ZDEN or ZAEN) is the position of the neutral sheet along Zsm axis, at XSM and YSM. IE is the parameter to show whether the observed point in in or outside the magnetopause The software contain the following subroutines (1) SDOY(DATE,TIME,YR,DOY,HR,TMI,SC) Find Year, Day of year, Month, Day of month, Hour, Minute, Second from Date(year/month/day) and Hour/Minute/Second (2) STIME(YD,SD,YR,DOY,TMO,DAY,HR,TMI,SC) Find Year,Day of Year, Month), Day of month, Hour, Minute and Second from Year and Day of Year and Second of Day (3) STIL(DOY,HR,TMI,TIL) Find the tilt angle of the geomagnetic axis for different Date and Time (4) SMPF(XSM,RMP,IM) Find the radius of the cross section of the magnetopause (5) SSEN(SDEN or SAEN)(TILA,XSM,YSM,ZSEN,RMP,IE) Find the position of SEN sheet along ZSM axis for different Rate and Time For SDEN we have two other subroutines: (6) SD1(TIL,H,H1,XSM,D) Find the displaced parameter D of the DEN model, so that it provides approximately equal cross-sectional areas above and below the neutral sheet (7) SFA4(AA,BB,CC,DD,X) Find the root of equation: X**4+AA*X**3+BB*X**2+CC*X+DD=0 in SD1 The detail information and instructions of these software can be find in the commends of these software. If you have questions and commends please fill free to contact with us REFERENCES Fairfield, D. H., A statistical determination of the shape and position of the geomagnetic neutral sheet, J. Geophys. Res., 85, 775, 1980. Sibeck, D. G., R. E. Lopez, and R. C. Roelof, Solar wind control of the magnetopause shape, location, and motion, J. Geophys. Res., 96, 5489, 1991 Wang, Z.-D. and R.-L. Xu, Neutral Sheet Observed on ISEE Satellite, Geophysical Research Letter, 21, (19)2087, 1994 Xu, R.-L., A Displaced Equatorial Neutral Sheet Surface Observed on ISEE-2 Satellite, J. Atmospheric and Terrestrial Phys., 58, 1085, 1991 Xu, R.-L., Dynamics of the Neutral Sheet in the Magnetotail during Substorm, Advances in solar-terrestrial science of China, ed. by W.-R. Hu et al., China Science Press, 1992 Xu, R.-L., Z.-D. Wang, M. Zhu and Q.-G. Zong, Particle Precipitation from the Magnetotail during Substorm, Adv. Space Research, 13, (4)269, 1992 Zhu, M. and R.-L. Xu, A continuous neutral sheet model and a normal curved coordinate system in the magnetotail, Chinese J. Space Science, 14, (4)269, 1994 (in Chinese) Li and Xu, GRL,27,855 (March,2000) -------------------------------------------------------------------------------------