Let’s Talk About Some WMM

Originally submitted by the Flying Cuttlefish, led me to this document

https://www.ncei.noaa.gov/sites/g/files/anmtlf171/files/2023-12/WMM_Annual_Report_2023.pdf

Chatty: Let’s break down and explain the elements of the figure and the associated terms mentioned:

1. Maximum Declination Deviations:
   Declination refers to the angle between magnetic north and true north. In geomagnetic studies, this deviation is important because it affects navigation systems that rely on magnetic compasses.
   Maximum Declination Deviations refer to the largest observed differences in declination during a specific geomagnetic storm.
2. G3 Storm:
   G3 Storm indicates a geomagnetic storm of moderate intensity according to the NOAA Space Weather Scales. Geomagnetic storms are disturbances in Earth’s magnetic field caused by solar activity, such as solar flares or coronal mass ejections.
3. February 27, 2023:
   The date of the specific G3 storm event being analyzed.
4. White and Black Circles:
   White Circles represent observatories where the maximum declination deviation during the storm was less than 1°. This means that the deviation from the expected magnetic north was minimal at these locations.
   Black Circles denote observatories where the maximum deviation exceeded 7°. This indicates a significant deviation from the expected magnetic north, which could impact navigation and other magnetic-sensitive operations.
5. WMM (World Magnetic Model):
   The World Magnetic Model (WMM) is a model that provides information about the Earth’s magnetic field. It is used for navigation and various applications that rely on accurate magnetic data. The WMM is updated periodically to reflect changes in the Earth’s magnetic field.
6. Contour Lines:
   Blue Solid Contour (2000 nT): This contour represents a horizontal magnetic field value of 2000 nanoteslas (nT). In the context of the WMM, this is used to define the blackout zone. Areas within this zone may experience significant magnetic field deviations that could affect magnetic navigation systems or instruments.
   Blue Dashed Contour (6000 nT): This contour represents a horizontal magnetic field value of 6000 nT and indicates the caution zone. This zone is less critical than the blackout zone but still indicates areas where the magnetic field values might be higher than usual, warranting caution in terms of magnetic navigation.
   Summary:
   The figure is illustrating the impact of the G3 geomagnetic storm on the magnetic declination at various observatories on February 27, 2023. The white and black circles show the extent of declination deviation, highlighting observatories with minimal versus significant deviations. The blue contours mark regions of different magnetic field strengths relative to the WMM, with specific thresholds for blackout and caution zones. The WMM helps in assessing these impacts, and the contours indicate areas where magnetic deviations are notable enough to require attention.