Magnetic Structure of an Erupting Filament

Abstract

The full 3-D vector magnetic field of a solar filament prior to eruption is presented. The filament was observed with the Facility Infrared Spectropolarimeter at the Dunn Solar Telescope in the chromospheric He i line at 10830Å on May 29 and 30, 2017. We inverted the spectropolarimetric observations with the HAnle and ZEeman Light (HAZEL) code to obtain the chromospheric magnetic field. A bimodal distribution of field strength was found in or near the filament. The average field strength was 24 Gauss, but prior to the eruption we find the 90th percentile of field strength was 435 Gauss for the observations on May 29. The field inclination was about 67 degree from the solar vertical. The field azimuth made an angle of about 47 to 65 degree to the spine axis. The results suggest an inverse configuration indicative of a flux rope topology. He i intensity threads were found to be co-aligned with the magnetic field direction. The filament had a sinistral configuration as expected for the southern hemisphere. The filament was stable on May 29, 2017 and started to rise during two observations on May 30, before erupting and causing a minor coronal mass ejection. There was no obvious change of the magnetic topology during the eruption process. Such information on the magnetic topology of erupting filaments could improve the prediction of the geoeffectiveness of solar storms.

Prominence formation by levitation-condensation at extreme resolutions

“…For both the 'prominence' and 'filament' projections, the internal dynamics of the associated material are oriented in line with their internal structures, which are themselves conflicting despite being identical phenomena (e.g., Zirker et al 1998;Berger et al 2008). Furthermore, the observed magnetic field within prominences favours the picture laid out by general filament observations in that their associated magnetic field, responsible for their suspension and therein their appearance, is oriented predominantly horizontal to the solar surface (as predicted by Kippenhahn & Schlüter (1957), see e.g., Casini et al 2003;Merenda et al 2007;Orozco Suárez et al 2014;Wang et al 2020).…”

Synoptic solar observations of the Solar Flare Telescope focusing on space weather

“…Utilizing the polarization data obtained from the observations of the He I 1083.0 nm, which show the magnetic field in filaments, are expected to aid such studies, even if their availability is limited to cases where the CMEs are accompanied by filament eruptions. Actually, Wang et al (2020) and Kuckein et al (2020) successfully carried out the detailed analysis of the magnetic field in filaments before and during their eruption. The observations of the SFT is expected to provide data for such analyses routinely.…”

Determining the dynamics and magnetic fields in He I 10830 Å during a solar filament eruption

“…The topology of these field lines is often reported as a flux rope, where field lines twist around the plasma at the main axis or spine of the filament. There are numerous studies supporting this scenario by means of models (see, e.g., van Ballegooijen & Martens 1989;Amari et al 1999), extrapolations (see, e.g., Guo et al 2010;Canou & Amari 2010;Jing et al 2010;Yelles Chaouche et al 2012), and observations (see, e.g., Kuckein et al 2012;Xu et al 2012;Wang et al 2020). Magnetic field strengths of 20-40 G are typically found in quiescent filaments (see, e.g., Trujillo Bueno et al 2002;Merenda et al 2006), whereas AR filaments can host fields up to 600-800 G (Kuckein et al 2009;Guo et al 2010;Xu et al 2012).…”

“…Their strongly blueshifted Hα profiles reached at least 60 km s −1 , although the real velocities were likely higher, but outside of the spectral range of the instrument. Recently, Wang et al (2020) followed a quiescent filament eruption with the Dunn Solar Telescope (DST, New Mexico, USA). The authors concentrated on the magnetic properties of the filament and found homogeneous linear polarization signals in the He i 10830 Å triplet, which they interpret as a magnetic flux rope.…”