SOLIS/VSM Polar Magnetic Field Data

TL;DR

This paper describes the SOLIS/VSM instrument's capabilities for high-resolution solar magnetic field observations and details the procedure for computing daily polar magnetic field measurements from these data.

Contribution

It introduces a method for deriving daily weighted averages of the solar polar magnetic field from SOLIS/VSM observations, with plans for further analysis.

Findings

Publicly available time series of polar magnetic field measurements.

Methodology for computing daily weighted averages of the polar magnetic field.

Future plans for analyzing chromospheric and true radial polar fields.

Abstract

The Vector Spectromagnetograph (VSM) instrument on the Synoptic Optical Long-term Investigations of the Sun (SOLIS) telescope is designed to obtain high-quality magnetic field observations in both the photosphere and chromosphere by measuring the Zeeman-induced polarization of spectral lines. With 1$^{\prime \prime}$ spatial resolution (1.14$^{\prime \prime}$ before 2010) and 0.05\AA\ spectral resolution, the VSM provides, among other products, chromospheric full-disk magnetograms using the CaII 854.2 nm spectral line and both photospheric full-disk vector and longitudinal magnetograms using the FeI 630.15 nm line. Here we describe the procedure used to compute daily weighted averages of the photospheric radial polar magnetic field at different latitude bands from SOLIS/VSM longitudinal full-disk observations. Time series of these measurements are publicly available from the SOLIS website at http://solis.nso.edu/0/vsm/vsm\_plrfield.html. Future plans include the calculation of the mean polar field strength from SOLIS/VSM chromospheric observations and the determination of the {\it true} radial polar field from SOLIS/VSM full-Stokes measurements.