Small-scale filament eruptions as the driver of X-ray jets in solar coronal holes

Abstract

Solar X-ray jets are evidently made by a burst of reconnection of closed magnetic field in a jet's base with ambient "open" field 1, 2 . In the widely-accepted version of the "emergingflux" model, that reconnection occurs at a current sheet between the open field and emerging closed field and also makes a compact hot brightening that is usually observed at the edge of the jet's base 1, 3 . Here we report on high-resolution X-ray and EUV observations of 20 randomly-selected X-ray jets in polar coronal holes. In each jet, contrary to the emergingflux model, a miniature version of the filament eruptions that initiate coronal mass ejections (CMEs) 4-7 drives the jet-producing reconnection, and the compact hot brightening is made by internal reconnection of the legs of the minifilament-carrying erupting closed field, analogous to solar flares of larger-scale eruptions. Previous observations have found that some jets are driven by base-field eruptions [8][9][10]12 , but only one such study, of only one jet, provisionally questioned the emerging-flux model 13 . Our observations support the view that solar filament eruptions are made by a fundamental explosive magnetic process that occurs on a vast range of scales, from the biggest CME/flare eruptions down to X-ray jets, and perhaps down to 1 even smaller jets that are candidates for powering coronal heating 10,14, 15 . A picture similar to that suggested by our observations was drawn before, inferred from different observations and based on a different origin of the erupting minifilament flux rope 11 (see Methods). Solar X-Ray jets are imaged from space in the ∼0.2-2.0 keV range. They are dynamic (upward velocities ∼200 km s −1 ), long (∼5×10 4 km), narrow (8×10 3 km), and transient (lifetimes To assess observationally the production of X-ray jets, we analysed 20 jets (Extended Data Table 1) in the solar polar regions using X-ray images from the X-ray telescope (XRT) on the Hinode satellite 22 , which detects a broad temperature range of coronal plasmas hotter than about These images clearly show a dark feature, similar to a small-scale solar chromospheric filament (hereafter, "minifilament"), moving upward and laterally, starting from ∼22:06 UT. Its velocity is ∼ 40 km s −1 between 22:07 UT and ∼22:10 UT, when it reaches the apex of the illuminated arched base of the X-ray jet. After 22:10 UT, the minifilament is expelled in the spire of an EUV jet that is the counterpart to the XRT jet. In EUV the jet has both emission and absorption components, with the minifilament evolving into part of the jet. Significantly however, the JBP, both in soft X-rays and in EUV, is at the location from where the minifilament erupted. Thus the JBP is the analog to the commonly-observed solar flare arcade forming in the wake of larger-scale filament 3 eruptions; such flare arcades are made by internal reconnection (i.e., reconnection occurring on the inside of the closed driving field 24 ) of the legs of the erupting closed field of a filament. This is not consistent with the JBP result...

A Breakout Model for Solar Coronal Jets with Filaments

“…Jet minifilaments are typically close in size to the width of the jet base, usually assumed to correspond to the closed-field region. Consequently, the lengths of mini-filaments vary with jet size, with quoted values varying from » l 6 Mm to » l 36 Mm (e.g., Sterling et al 2015;Panesar et al 2016). In our simulations, the sheared filament channel is of comparable size to the extent of the separatrix in the z direction.…”

“…A particular challenge to the the flux emergence model is posed by the relatively recent identification in many jets of small filament-like structures that are invisible in X-rays but can be seen in wavelengths associated with cooler plasma, such as EUV and a H (e.g., Zheng et al 2012;Sterling et al 2015;Hong et al 2016;Zhang et al 2016). These "mini-filaments" are observed along and above the polarity inversion lines (PILs) of preexisting strong bipoles (e.g., Chae et al 1999;Hong et al 2011Hong et al , 2014Hong et al , 2016Zheng et al 2012;Adams et al 2014;Panesar et al 2016;Zhang et al 2016).…”

“…Recently, Sterling et al (2015) examined 20 randomly selected jets and found that all involved mini-filaments. The largest were comparable in size to the closed-field region and erupted to form broad blowout jets with a strongly rotating spire.…”

“…Motivated by the observations of Sterling et al (2015), we conducted a high-resolution MHD simulation (Wyper et al 2017) showing how the "magnetic breakout" mechanism (Antiochos et al 1999) for large-scale CMEs is universal, also explaining small-scale coronal jets involving mini-filaments. In these jets, free energy is stored in the filament channel along the PIL of a bipole embedded in an open ambient magnetic field; the filament subsequently erupts to form a blowout-like untwisting jet.…”

Observations of Multiple Blobs in Homologous Solar Coronal Jets in Closed Loop

“…They have cool components and show rotating and/or transverse drifting motions Hong et al, 2013;Pucci et al, 2013;Schmieder et al, 2013;Zhang & Ji, 2014a;Liu et al, 2015b). However, Sterling et al (2015) proposed that both the standard and blowout polar jets in their sample are driven by small-scale filament eruptions, which resemble the coronal mass ejections (CMEs) driven by typical filament eruptions (Lin, 2004). Sometimes, a jet recurs at the same place with the same morphology and direction of outflow, forming the so-called recurrent or homologous jets.…”