Quantitative Assessment of Tsyganenko Models at Geosynchronous Orbit Chia-Lin Huang* and Harlan Spence Boston University Howard Singer NOAA Nicolai Tsyganenko University of St. Petersburg Huang, C.-L., H. E. Spence, H. J. Singer, and N. A. Tsyganenko (2008), A quantitative assessment of empirical magnetic field models at geosynchronous orbit during magnetic storms, J. Geophys. Res., 113, A04208, doi: /2007JA

Comparison of Recent Tsgyanenko Models T96T02TS05 Boundary prescriptions Magnetopause based on Sibeck et al. [1991] Magnetopause based on Shue et al. [1998] and tailward =< 15 R E Same as T02 Field sources B CF + B SRC + B TC + B FAC + B INT Same as T96, plus B PRC Same as T02 Fitted magnetic field data Non-storm and storm time data a Same as T96 b Storm-time data from 37 storm events c Model inputs Pdyn, Dst, IMF By and Bz, dipole tilt Same as T96, plus 2 indices (G 1 and G 2 ) representing time-integration effect Same as T96, plus 6 indices (W 1 – W 6 ) representing time- integration effect Calculation methods Linear amplitude of the field sources depends on model inputs Same as T96Non-linear saturation for extreme storm conditions ; each field source has its own relaxation time and driving functions Chia-Lin Huang at 2009 RBSP SWG2 a IMPs, HEOS, ISEE-1 and 2 b Geotail, Polar, ISEE-2, AMPTE/CCE, AMPTE/IRM, CRRES, and DE-1 c GOES-8, 9, and 10, Polar, Geotail, and Equator-S

Statistical Study for Tsyganenko Models  52 major storms (Dst minimum < -100 nT) from 1996 to 2004, include pre- and post-storm intervals  Data/model residual fields (∆B = B Data – B Model ) as functions of local time and Dst 3Chia-Lin Huang at 2009 RBSP SWG Under-estimate Perfect prediction Over-estimate

Data/model residual fields (Dst) 4Chia-Lin Huang at 2009 RBSP SWG

Data/model residual fields (Local time) 5Chia-Lin Huang at 2009 RBSP SWG

Consequences of field model errors  Inaccurate B-field model could alter the results of related studies  Example, radial profiles of phase space density  Discrepancies between T models using same quiet-time inputs  Could affect calculations of non-local parameters such as K and L* 6Chia-Lin Huang at 2009 RBSP SWG ~15% error in L* calculation between T96 and TS05 45° 35° 30 °

Conclusions and Future work  What makes TS05 better than the earlier Tsyganenko models?  Partial ring current  Fitted data includes more storm-time data  Time-integration effect as the input parameters  Non-linear saturation for extreme storm conditions  Each field sources has its own relaxation time and driving functions  Future validation work besides GEO:  THEMIS outside GEO and magnetopause location  RBSP for inside GEO Chia-Lin Huang at 2009 RBSP SWG7 of 7