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Magnetic Field Models in the Satellite Situation Center Software, V. 2.2

The magnetic field models used in the Satellite Situation Center (SSC) software were updated between Versions 2.1 and 2.2, to use the newer versions of the Tsyganenko models, as recommended by the Goddard Space Flight Center Magnetospheric Modeling Group.

Existing Tsyganenko Models

The GSFC Modeling Group makes available several versions of both T87 and T89 models, as listed below:
Model Designation Based on data from Activity Levels and criterion Tailward range of validity Reference and/or comments
T87a IMP-HEOS 6 by Kp 70 RE Oringinal (Long) T87 model [Tsyganenko, 1987]
T87b IMP-HEOS 8 by Kp 30 RE Original (Short) T87 model [Tsyganenko, 1987]
T87Wa IMP-HEOS 6 by Kp 70 RE Warped variation of (Long) T87 using Gosling et al. [1986] formula [Peredo and Stern,1991b]
T87Wb IMP-HEOS 8 by Kp 30 RE Warped variation of (Short) T87 using Gosling et al. [1986]formula [Peredo and Stern, 1991b]
T87WSa IMP-HEOS 6 by Kp 70 RE Stern variation of T87Wa with current free lobes [Stern, 1990]
T87WSb IMP-HEOS 8 by Kp 30 RE Stern variation of T87Wb with current free lobes [Stern, 1990]
T87Wc ISEE 8 by Kp 22 RE Warped variation of (Short) T87 based on ISEE data [Peredo and Stern, 1991a]
*T87Wd IMP-HEOS-ISEE 6 by Kp 70 RE T87 with warping effects incorporated self-consistently
T87We IMP-HEOS-ISEE 12 by psw /Bz 30 RE Self-consistently warped T87 organized by solar wind and IMF conditions [Peredo et al., 1992]
T89a IMP-HEOS 6 by Kp 70 RE Original T89 model [Tsyganenko, 1989]
T89b IMP-HEOS 6 by AE 70 RE Variant of T89 organized by AE
*T89c IMP-HEOS-ISEE 7 by Kp 70 RE Revised T89 based on expanded data set
* These models are the ones recommended by the GSFC Modeling Group for use until a new model is released.

The updated SSC version thus uses the T87Wd, T89b and T89c Tsyganenko models (using the nomenclature of Peredo et al., JGR, 98, 15343, 1993). The T87Wd and T89c models are provided as those are the ones recommended by the modeling group. The T89b model is offered as an alternative model, parameterized by the AE index instead of the Kp index.

As noted in the table, one key difference between T87Wd and T89c and the original models is the extent of the database on which they are based. The table below summarizes the key characteristics of the datasets used to construct the models.

Data Sets Used to Derive Models

Spacecraft Time Interval Used No. Points Total Time,hours No. Orbits
A-IMP D
(Explorer 33)		 July '66 - July '68 724 356 34
A-IMP E
(Explorer 35)		 July '67 - Jan '69 1,260 1,260 17
IMP 4
(IMP F, Explorer 34)		 May '67 - Sept '71 5,173 2,799 144
IMP 5
(IMP G,Explorer 41)		 June '69 -Sept '71 9,426 5,480 195
IMP 6
(IMP I, Explorer 43)		 Mar '71 - Sept '74 11,801 5,419 312
HEOS 1 Dec '68 - Dec '73 3,908 1,980 215
HEOS 2 Feb '72 - Aug '74 3,044 1,320 152
IMP 7
(IMP H, Explorer 47)		 Sept '72 - Apr '73 681 650 14
IMP 8
(IMP J,Explorer 50)		 Oct '73 - June '86 9,568 8,052 280
ISEE 1 Jan '80 - Dec '81 17,602 6,794 301
ISEE 2 Jan '78 - Jan '80 16,558 6,497 311
Totals 79,745 40,607

For additional information about these data sets please refer to "A large magnetosphere magnetic field database," Fairfield et al. JGR, 99, 11319, 1994.

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