GPS World, February 2014

INNOVATION Algorithms Methods FIGURE 3 Interplanetary magnetic field Bz component Kp index AE index and Dst index during October 13 25 doy 286 298 in 2011 nT nanoteslas Data from World Data Center for Geomagnetism Kyoto and Goddard Space Flight Center Space Physics Data Facility model 0008 TECU2 second is chosen to characterize the potential rapid change of the ionosphere LQDOO WKH HVWLPDWHG FRHI FLHQWV SURYLGHG E WKH DOPDQ OWHU DUH WKHQ XVHG WR UHFRQVWUXFW WKH HOHFWURQ GHQVLW HOG Testing the Approach In this section we report on tests of the 3D UNB IMT and compare its performance with that of the 3D SH approach HFDXVH RI WKH DGYDQWDJHV RI VHQVLWLYLW RI 81 07 especially with the single station processing strategy it is H SHFWHG WKDW WKLV WHFKQLTXH ZLOO KHOS LQ EHWWHU FDSWXULQJ ORFDOL HG LRQRVSKHULF VWUXFWXUHV DERYH VPDOO UHJLRQDO QHWZRUNV RU DERYH D VLQJOH VWDQGDORQH VWDWLRQ FRPSDUHG WR WKH 6 DSSURDFK GGLWLRQDO EHQH WV PD EH H SHFWHG IRU GLVWXUEHG LRQRVSKHULF FRQGLWLRQV RU DVVHVVLQJ WKH WZR PRGHOLQJ WHFKQLTXHV D VPDOO UHJLRQDO QHWZRUN RI IRXU 6 UHIHUHQFH VWDWLRQV ORFDWHG IURP JHRJUDSKLF ODWLWXGH 1 WR 1 DQG ORQJLWXGH WR ZDV FKRVHQ WR SHUIRUP VLQJOH VWDWLRQ DQG PXOWL VWDWLRQ QHWZRUN SURFHVVLQJ 7KH VWDWLRQV DUH 2 LQ UHHQEHOW 0DU ODQG 81 DQG 5 1 LQ UHGHULFWRQ 1HZ UXQVZLFN DQG 9 LQ 9DO G 2U 4XHEHF FIGURE 2 shows the locations of the reference stations chosen for the modeling 7KH GXDO IUHTXHQF 36 GDWD XVHG IRU WKH WHVWV ZDV REWDLQHG IURP 2FWREHU GD RI HDU GR LQ ZLWK WKH VDPSOLQJ WLPH LQWHUYDO RI VHFRQGV 7KH FRUUHVSRQGLQJ YDOXHV RI WKH LQWHUSODQHWDU PDJQHWLF HOG FRPSRQHQW WKH SODQHWDU JHRPDJQHWLF LQGH S WKH DXURUDO HOHFWURMHW LQGH DQG WKH GLVWXUEDQFH VWRUP WLPH LQGH VW RQ WKHVH GD V are shown in FIGURE 3 W LV VHHQ WKDW D VHYHUH LRQRVSKHULF VWRUP WULJJHUHG E D FRURQDO PDVV HMHFWLRQ IURP WKH VXQ RFFXUUHG ODWH RQ 2FWREHU GR DQG FRQWLQXHG WKURXJK WKH HQWLUH GD RI 2FWREHU GR 7KH RWKHU GD V VHHP UHODWLYHO TXLHW 7KXV ZH FKRVH 2FWREHU DV D W SLFDO GD ZLWK TXLHW LRQRVSKHULF FRQGLWLRQV DQG 2FWREHU DV D W SLFDO GD ZLWK GLVWXUEHG LRQRVSKHULF FRQGLWLRQV 2000 1800 1600 1400 1200 1000 800 600 400 200 0 Height kilometers 103 104 105 106 Electron density inverse centimeters cubed FIGURE 4 The electron density profile produced by linear 3D UNB IMT overhead FRDN at 12 00 UT on October 16 doy 289 in 2011 LQ WKH IROORZLQJ WHVWV 7KH SHUIRUPDQFH RI ERWK PHWKRGV UNB IMT and SH model with the two processing scenarios ZLOO EH FRPSDUHG E DQDO LQJ WKH SRVW W UHVLGXDOV DQG 7 RI WKH VWDWH HVWLPDWLRQ SURFHVV IRU ERWK TXLHW DQG GLVWXUEHG ionospheric conditions OO IRXU UHIHUHQFH VWDWLRQV LQ WKH VPDOO QHWZRUN KDYH WKH DELOLW WR SURYLGH ERWK DQG 3 FRGH SVHXGRUDQJH PHDVXUHPHQWV Q RXU WHVWV WKH 3 FRGH REVHUYDEOH LV XVHG WR H WUDFW 7 WKURXJK OHYHOLQJ WKH FRUUHVSRQGLQJ FDUULHU SKDVH PHDVXUHPHQWV H XVHG D HOHYDWLRQ DQJOH FXW RII LQ RXU VWXG Single Station Experiment The estimated parameters of 2D DQG 81 07 KDYH GLIIHUHQW SK VLFDO PHDQLQJV GXH WR the different modeling strategies In theory the 3D UNB 07 FDQ UHSURGXFH WKH HOHFWURQ GHQVLWLHV IRU DQ ORFDWLRQ KRUL RQWDO DQG YHUWLFDO DW DQ HSRFK FIGURE 4 shows an H DPSOH RI WKH HOHFWURQ GHQVLW SUR OH SURGXFHG E WKH OLQHDU 81 07 LQ WKH HQLWK GLUHFWLRQ RI VWDWLRQ 5 1 DW 87 RQ 2FWREHU GR 7KHUHIRUH ZH ZLOO KDYH WR LQWHJUDWH HOHFWURQ GHQVLWLHV LQWR 7 IRU WKH 81 07 PRGHOLQJ UHVXOWV LI ZH ZDQW WR FRPSDUH KRZ WKH WZR DSSURDFKHV KDYH PRGHOHG WKH LRQRVSKHUH VLGH E VLGH RU WKH SXUSRVH RI VHQVLWLYLW FRPSDULVRQ WKH UHVXOWV IURP DQG 81 07 DUH FRPSDUHG LQ WHUPV RI SRVW W UHVLGXDOV DV ZHOO DV WLPH VHULHV RI HVWLPDWHG Y7 LQ WKH VLQJOH VWDWLRQ SURFHVVLQJ VFHQDULR V GLVFXVVHG DERYH ZH XVH WKH 36 GDWD IURP VWDWLRQ 5 1 RQO IRU 2FWREHU DQG LQ WKLV VXEVHFWLRQ 7KH SRVW W UHVLGXDOV DUH FDOFXODWHG DV WKH GLIIHUHQFH EHWZHHQ WKH PHDVXUHG DQG HVWLPDWHG ELDVHG V7 URP WKH WRS WR ERWWRP SDQHOV FIGURE 5 shows the estimated Y7 LQ WKH HQLWK GLUHFWLRQ RYHU WKH VWDWLRQ SRVW ILW UHVLGXDOV HVWLPDWHG VDWHOOLWH DQG UHFHLYHU V DQG XQELDVHG V7 ZLWK UHVSHFW WR ORFDO PHDQ VRODU WLPH VHULHV REWDLQHG with linear 2D left hand panels and 3D right hand panels 81 07 DSSURDFKHV UHVSHFWLYHO H XVH D GLIIHUHQW FRORU IRU HDFK VDWHOOLWH WR VHH LQGLYLGXDO LPSURYHPHQW RI VDWHOOLWHV LQ WHUPV RI SRVW W UHVLGXDOV HVWLPDWHG DQG XQELDVHG V7 V IRU WKH SRWHQWLDO LPSURYHPHQW RI 81 07 ZH VXSSRVHG LI WKH PRGHO ZLWK VLQJOH VKHOO DVVXPSWLRQ GPS World February 2014 www gpsworld com 62