Observations and Modelling of the Pre-Flare Period of the 29 March 2014 X1 Flare

Abstract

On the 29 March 2014 NOAA active region (AR) 12017 produced an X1 flare which was simultaneously observed by an unprecedented number of observatories. We have investigated the pre-flare period of this flare from 14:00 UT until 19:00 UT using joint observations made by the Interface Region Imaging Spectrometer (IRIS) and the Hinode Extreme Ultraviolet Imaging Spectrometer (EIS). Spectral lines providing coverage of the solar atmosphere from chromosphere to the corona were analysed to investigate pre-flare activity within the AR. The results of the investigation have revealed evidence of strongly blue-shifted plasma flows, with velocities up to 200 km/s, being observed 40 minutes prior to flaring. These flows are located along the filament present in the active region and are both spatially discrete and transient. In order to constrain the possible explanations for this activity, we undertake non-potential magnetic field modelling of the active region. This modelling indicates the existence of a weakly twisted flux rope along the polarity inversion line in the region where a filament and the strong pre-flare flows are observed. We then discuss how these observations relate to the current models of flare triggering. We conclude that the most likely drivers of the observed activity are internal reconnection in the flux rope, early onset of the flare reconnection, or tether cutting reconnection along the filament.

27 pages, 15 figures, accepted for publication in Solar Physics

References in corpus (9)

• Torus instability
• Evidence of Non-Thermal Particles in Coronal Loops Heated Impulsively by Nanoflares
• The 2014 March 29 X-flare: sub-arcsecond resolution observations of Fe XXI 1354.1
• Modeling the Dispersal of an Active Region: Quantifying Energy Input into the Corona
• Imaging and Spectroscopic Diagnostics on the Formation of Two Magnetic Flux Ropes Revealed by SDO/AIA and IRIS
• The fast filament eruption leading to the X-flare on March 29, 2014
• On the Origin of a Sunquake during the 29 March 2014 X1 Flare
• Magnetic Energy Dissipation during the 2014 March 29 Solar Flares
• The role of filament activation in a solar eruption

Cited by in corpus (11)

• Critical Science Plan for the Daniel K. Inouye Solar Telescope (DKIST)
• Properties of Flare-Imminent versus Flare-Quiet Active Regions from the Chromosphere through the Corona II: NonParametric Discriminant Analysis Results from the NWRA Classification Infrastructure (NCI)
• Identification of Pre-flare Processes and Their Possible Role in Driving a Large-scale Flux Rope Eruption with Complex M-class Flare in the Active Region NOAA 12371
• Quasi-periodic pulsations in a solar flare with an unusual phase shift
• Electric current evolution at the footpoints of solar eruptions
• Properties of Flare-Imminent versus Flare-Quiet Active Regions from the Chromosphere through the Corona I: Introduction of the AIA Active Region Patches (AARPs)
• The Role of a Tiny Brightening in a Huge Geo-effective Solar Eruption Leading to the St Patrick's Day Storm
• Evolution of magnetic fields and energy release processes during homologous eruptive flares
• A new view of the solar interface region from the Interface Region Imaging Spectrograph (IRIS)
• Pre-flare and active region plasma flows and structure seen by the short wavelength camera on SOLAR-C/EUVST
• Investigating Pre-flare Signatures in Spectroscopic Observations of an X9-class Solar Flare