Abstract
Abstract High-resolution observations from the Interface Region Imaging Spectrometer reveal the existence of a particular type of small solar jet, which arose singly or in clusters from a tornado-like prominence suspended in the corona. In this study, we perform a detailed statistical analysis of 43 selected mini-jets in the tornado event. Our results show that the mini-jets typically have (1) a projected length of 1.0–6.0 Mm, (2) a width of 0.2–1.0 Mm, (3) a lifetime of 10–50 s, (4) a velocity of 100–350 km s−1, and (5) an acceleration of 3–20 km s−2. Based on spectral diagnostics and EM-Loci analysis, these jets seem to be multithermal small-scale plasma ejections with an estimated average electron density of ∼2.4 × 1010 cm−3 and an approximate mean temperature of ∼2.6 × 105 K. Their mean kinetic energy density, thermal energy density, and dissipated magnetic field strength are roughly estimated to be ∼9 erg cm−3, 3 erg cm−3, and 16 G, respectively. The accelerations of the mini-jets, the UV and EUV brightenings at the footpoints of some mini-jets, and the activation of the host prominence suggest that the tornado mini-jets are probably created by fine-scale external or internal magnetic reconnections (a) between the prominence field and the enveloping or background field or (b) between twisted or braided flux tubes within the prominence. The observations provide insight into the geometry of such reconnection events in the corona and have implications for the structure of the prominence magnetic field and the instability that is responsible for the eruption of prominences and coronal mass ejections.
Highlights
Solar jets are transient collimated plasma ejections in the solar atmosphere (Roy 1973)
As space-borne instruments have evolved since the 1980ʼs, the observations of dynamic solar events have been extended from Hα and radio to UV, EUV, and X-ray wave bands (e.g., Schmahl 1981; Schmieder et al 1988; Alexander & Fletcher 1999; Zhang et al 2000; Cirtain et al 2007; Jiang et al 2007; Chen et al 2008; Tian et al 2011; Joshi et al 2018; Zhang & Ni 2019)
Most of the mini-jets were captured by the Atmospheric Imaging Assembly (AIA; Lemen et al 2012) on board the Solar Dynamics Observatory (SDO; Pesnell et al 2012), which supplies us with full-disk intensity images up to 0.5 Re above the solar limb with 0 6 pixel size and 12 s cadence in seven EUV channels centered at 304 Å (He II, 0.05 MK), 131 Å (Fe VIII, 0.4 MK and Fe XXI, 11 MK), 171 Å (Fe IX, 0.6 MK), 193 Å (Fe XII, 1.3 MK and Fe XXIV, 20 MK), 211 Å (Fe XIV, 2 MK), 335 Å (Fe XVI, 2.5 MK), and 94 Å (Fe XVIII, 7 MK), respectively
Summary
Solar jets are transient collimated plasma ejections in the solar atmosphere (Roy 1973). A substantial amount of observations (e.g., Chen et al 2009; Hong et al 2011, 2016; Shen et al 2012, 2017; Young & Muglach 2014; Lee et al 2015; Li et al 2015; Sterling et al 2016; Zhang & Zhang 2017; Kumar et al 2018; Yang et al 2019b) and numerical simulations (e.g., Archontis & Hood 2013; Pariat et al 2015, 2016; Wyper et al 2018; Meyer et al 2019) have shown that the blowout eruption of a small-scale sheared-core magnetic arcade can play an important role in producing a solar jet. Samanta et al (2019) detected flux emergence and/ or flux cancellation around the spicule footpoint region and conjectured that this supports the formation of spicules from reconnection Their observations do not exclude other formation mechanisms of small jets (e.g., Martínez-Sykora et al 2017).
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