 Geomagnetism Frequently Asked Questions by National Oceanic and Atmospheric Administration

Official NCEI geomagnetism FAQ: www.ncei.noaa.gov/products/geomagnetism-frequently-asked-questions

The section on magnetic elements gives a representative terrestrial surface total-intensity range of about $25$–$65\mu \mathrm{T}$. This is not a specified orbital field measurement. The source separately identifies geographic variation and external magnetic contributions.