Space Climate 7 Meeting Abstract
On the polar magnetic fields in the GONG solar synoptic maps
Ljubomir Nikolic (Natural Resources Canada )
The Global Oscillation Network Group (GONG) synoptic maps of the photospheric magnetic field are widely used in the solar and space weather community. The GONG maps are assembled using measurements from six observatories, which together provide 24-hour coverage of the solar disc and hourly updated synoptic maps. GONG maps are a particularly popular choice in operational space weather applications. Since the Sun’s polar regions are not always visible due to the tilt of the Sun’s rotation axis in respect to the ecliptic plane, interpolation methods are usually used to represent the polar magnetic fields. Correction of the polar fields is a standard part of the GONG magnetogram processing pipeline. Here, GONG synoptic maps of the magnetic field are investigated for 2006-2019. The results reveal periodic changes in the polar magnetic field which, particularly in recent years, suggest issues with the GONG treatment of observational gaps in the polar fields. The issues with the representation of the polar magnetic fields do not involve only inaccuracy in the field strength. The results suggest that the polarity of the field could be missed as well. This contributes to the fact that numerically modeled open magnetic flux with GONG synoptic maps significantly underestimates the observed flux.
Mode of presentation: poster