Katia Nazarova, Mike Purucker, Terry Sabaka
New Magsat Data Set
The data set of Magsat observations utilized for the CMP3 Comprehensive Model of the geomagnetic field (Sabaka et al., 2000) was originally developed for main field analysis up to degree 13 only. The CMP3 model now includes static internal terms in excess of degree and order 65. One area of weakness in the CMP3 is the limited areal distribution of the data set with significant gaps in the Siberian region. In order to fill in the gaps and improve its areal distribution we have utilized a bootstrap approach. In this approach we identify additional data by evaluating it's residual to CMP3. In the process we have created a data set that should be useful to the broader geomagnetic community involved in modeling and analysis. This new data set includes both vector dawn and dusk Magsat data that has been selected for adherence to attitude quality guidelines (accuracy better than 20 arc seconds). The data is from magnetically quiet times as defined by Kp and has been decimated to 0.02 Hz (approximately 1 sample every 350 km along track). Internal lithospheric static fields to degree and order 42, ionospheric, magnetospheric, and toroidal fields have been removed at the remaining observation locations. In excess of 58,000 observations have been evaluated in this way. The residuals to these observations offer a way of selecting data for input to regional models, and for improving the distribution of data in the comprehensive model. The data set is Available on-line from the GSFC geomagnetics group.