Chromospheric Synoptic Maps of Polar Crown Filaments

TL;DR

This paper presents the creation and analysis of synoptic maps of polar crown filaments using multi-line chromospheric data from ChroTel, revealing their properties and variations over Solar Cycle 24 to enhance understanding of solar cycle dynamics.

Contribution

It introduces a new method for automatically extracting and analyzing polar crown filaments from multi-line chromospheric observations, including Doppler velocity mapping, over a significant solar cycle phase.

Findings

Polar crown filaments' number and location vary with the solar cycle phase.

Comparison shows differences between polar crown and quiet-Sun filaments.

A comprehensive super-synoptic map summarizes filament properties over Solar Cycle 24.

Abstract

Polar crown filaments form above the polarity inversion line between the old magnetic flux of the previous cycle and the new magnetic flux of the current cycle. Studying their appearance and their properties can lead to a better understanding of the solar cycle. We use full-disk data of the Chromospheric Telescope (ChroTel) at the Observatorio del Teide, Tenerife, Spain, which were taken in three different chromospheric absorption lines (H-alpha 6563A, CaII-K 3933A, and HeI 10830A), and we create synoptic maps. In addition, the spectroscopic HeI data allow us to compute Doppler velocities and to create synoptic Doppler maps. ChroTel data cover the rising and decaying phase of Solar Cycle 24 on about 1000 days between 2012 and 2018. Based on these data, we automatically extract polar crown filaments with image-processing tools and study their properties. We compare contrast maps of polar crown filaments with those of quiet-Sun filaments. Furthermore, we present a super-synoptic map summarizing the entire ChroTel database. In summary, we provide statistical properties, i.e. number and location of filaments, area, and tilt angle for both the maximum and declining phase of Solar Cycle 24. This demonstrates that ChroTel provides a promising data set to study the solar cycle.