Editing Magnetic field (section)

===Measurement===
{{main|Magnetometer}}

An instrument used to measure the local magnetic field is known as a [[magnetometer]]. Important classes of magnetometers include using [[Search coil|induction magnetometers]] (or search-coil magnetometers) which measure only varying magnetic fields, [[Magnetometer#Rotating coil magnetometer|rotating coil magnetometers]], [[Hall effect]] magnetometers, [[proton magnetometer|NMR magnetometers]], [[SQUID|SQUID magnetometers]], and [[Magnetometer#Fluxgate magnetometer|fluxgate magnetometers]]. The magnetic fields of distant [[astronomical object]]s are measured through their effects on local charged particles. For instance, electrons spiraling around a field line produce [[synchrotron radiation]] that is detectable in [[radio waves]]. The finest precision for a magnetic field measurement was attained by [[Gravity Probe B]] at {{val|5|u=aT}} ({{val|5|e=-18|u=T}}).<ref>{{cite web | url=http://www.nasa.gov/pdf/168808main_gp-b_pfar_cvr-pref-execsum.pdf |archive-url=https://ghostarchive.org/archive/20221009/http://www.nasa.gov/pdf/168808main_gp-b_pfar_cvr-pref-execsum.pdf |archive-date=2022-10-09 |url-status=live|title=Gravity Probe B Executive Summary|pages=10, 21}}</ref>