Cross-Calibrating Sunspot Magnetic Field Strength Measurements from the McMath-Pierce Solar Telescope and the Dunn Solar Telescope

摘要

In this article we describe a recent effort to cross-calibrate data from aninfrared detector at the McMath-Pierce Solar Telescope and the FacilityInfraRed Spectropolarimeter (FIRS) at the Dunn Solar Telescope. A synopticobservation program at the McMath-Pierce has measured umbral magnetic fieldstrengths since 1998, and this data set has recently been compared with umbralmagnetic field observations from SOHO MDI and SDO HMI. To further improve onthe data from McMath-Pierce, we compared the data with measurements taken atthe Dunn Solar Telescope with far greater spectral resolution than has beenpossible with space instrumentation. To minimise potential disruption to thestudy, concurrent umbral measurements were made so that the relationshipbetween the two datasets can be most accurately characterised. We find thatthere is a strong agreement between the umbral magnetic field strengthsrecorded by each instrument, and we reduced the FIRS data in two different waysto successfully test this correlation further.