Comparison of the Global Analystical Models of the Main Geomagnetic Field with the Stratospheric Balloon Magnetic Data
Tsvetkov, Yury; Filippov, Sergey; Sidorova, Larisa; Frunze, Alla

Three global analytical models of the main geomagnetic field constructed on the base of satellite data are used. First model is IGRF, second one is Daily Mean Spherical Harmonic Model (DMSHM) has been derived from CHAMP daily mean data and third one - EMM2010, model derived from satellite and ground base data.

Regional (lithospheric) magnetic field at altitude of ~30 km is formed by all sources of the Earth's crust. This fact allows receive the fullest data about regional and long-wave-length magnetic anomalies along the stratospheric balloon tracks at the altitude of ~30 km.

DMSHM model is capable to eliminate of the secular variation of main geomagnetic field up to 0,2 nT during process of the extracting of the magnetic anomalies. This model can be constructed within ± 1 months from the moment of stratospheric balloon surveys with sampling of the days with magnetic activity up to Kp <20. Comparing data of balloon geomagnetic surveys (in situ) and the DMSHM data, we have received - last one leads to an error of representation of the main geomagnetic field up to ±5 nT (at the altitude of ~30 km). The admissible spectral restriction of the model which is free of the magnetic anomaly harmonics of the observed area is investigated on an example of EMM2010 model. It is shown that the restriction of the model by the first 13 harmonics can lead to the errors in the representation of the main geomagnetic field up to 15 nT (at the altitude of ~30 km). According to the balloon data it is shown that EMM2010 model unsatisfactorily displays the main geomagnetic field at the altitude of 30 km. The regional anomaly geomagnetic field derived from EMM2010 model differs (70%) from the measured one on the balloon.

Conclusion - the qualitative model of the main geomagnetic field cannot be constructed only by means of satellite and ground base data. An improved model derived from the satellite, ground base and balloon magnetic survey data could show more reliable information about the regional crust magnetic field and could have the way to see deep magnetic structures of the Earth's crust.

The method (way) to check and correct global analytical models of the main geomagnetic field have suggesting and describing here also. The main idea of this way - use the balloon gradient magnetic surveys to find the areas where the magnetic anomalies are absent. Then it is possible to compare the balloon's (in situ) and model's data. The difference will be the amendment for model data (correcting number). But corrections are available only for places close to along balloon route.

IZMIRAN plans to launch a few balloon flights with magnetic gradiometer onboard during Swarm mission. IZMIRAN team is included in the list of principal investigators of Swarm mission. We hope to apply the approaches described above to data of Swarm mission.