Direct Observation of a Large-scale CME Flux Rope Event Arising from an Unwinding Coronal Jet

Coronal mass ejections (CMEs) are the most violent eruptive magnetic activities in the solar atmosphere. They often appear as stellar-sized magnetized plasma bubbles in white-light coronagraph observations, and can rapidly release a vast amount of mass and energy into the inner heliosphere making our near-Earth space a hazardous place (e.g., Chen 2011; Schmieder et al. 2013). To date, almost all CME theories suggested that the core of CMEs corresponds to rapidly erupting magnetic flux ropes (MFRs; e.g., Forbes 2000; Lin & Forbes 2000). As the desirable progenitor of CME flux ropes, an MFR is defined as a set of highly coherent helical magnetic field lines winding around one common axis. In such a nonpotential topology, a mature MFR often appears with a high storage of magnetic free energy and helicity, and is prone to suffer ideal MHD instabilities. Hence, the presence of a mature MFR prior to or even during CME initiations is always given great attention.

In the past two decades, a lot of effort has been made in numerical simulations and observations on the formation and destabilization of active-region MFRs (see reviews, i.e., Cheng et al. 2017; Georgoulis et al. 2019; Patsourakos et al. 2020). One important reason is that active-region MFR proxies often repeatedly form in newly emerged bipolar active regions (ARs) and their eruptions can result in recurrent CMEs in rapid succession (e.g., Zhang & Wang 2002; Li et al. 2012; Liu et al. 2017). In accord with filament channel formations, it is widely believed that MFRs can be created along polarity inversion lines in two ways: (1) the directly emergence of a mature MFR from the below photosphere (e.g., Fan & Gibson 2004; Manchester et al. 2004; Okamoto et al. 2008) or (2) successive reconnection of coronal fields induced by the continuously photospheric shearing or converging flows (e.g., Amari et al. 2000; Aulanier et al. 2010; Guo et al. 2013). Due to differences in the spatial height of reconnection, the second one may respectively manifest as tether-cutting reconnection just at the onset of the eruption (e.g., Liu et al. 2010; Chen et al. 2018, 2019) or slow flux cancellation in the photosphere long prior to the eruption (e.g., Green et al. 2011; Savcheva et al. 2012; Yang et al. 2016). In particular, apart from appearing in the formation phase of MFRs and filaments, flux cancellation is also thought as a popular triggering mechanism for CMEs and coronal jets (e.g., Zhang et al. 2001; Zhang & Wang 2001; Wang et al. 2017; Chen et al. 2018; Sterling et al. 2018).

In a bipolar configuration, the ideal MHD models suggest that the sudden onset of MFR eruptions is directly triggered by the ideal torus instability (Török et al. 2004; Olmedo & Zhang 2010), ideal kink instability (Hood & Priest 1979; Kliem & Török 2006), and also catastrophe mechanisms (Isenberg et al. 1993; Lin & Forbes 2000). Instead, the non-MHD models emphasize that MFR eruptions tend to take place if preflare reconnection below MFRs reduce their overlying magnetic constraints (e.g., Chen & Shibata 2000; Moore et al. 2001; Jiang et al. 2013; Chen et al. 2014, 2018). However, real source regions of many large-scale CMEs often cover more broad spatial ranges, connecting two intercoupled ARs, or even a cluster of ARs (e.g., Wen et al. 2006; Zhou et al. 2006; Wang et al. 2007, 2015; Zhang et al. 2007). Accordingly, their CME progenitors are more likely associated with larger-scale pre-eruption structures, such as transequatorial magnetic loops, interconnecting filaments among ARs, and extended bipolar polarity inversion lines (e.g., Zhou et al. 2006, 2019; Wang et al. 2007; Su & van Ballegooijen 2013). Under these multipolar complex magnetic systems, CME initiations and eruptive dynamics are not an alone behavior of a bipolar AR; instead, it may be tied to magnetic coupling and instability in the whole magnetic flux system (Antiochos et al. 1999; Wang et al. 2007, 2015; Schrijver et al. 2013; Zhou et al. 2019, 2020).

In addition, multipolar complex magnetic systems often breed frequent sympathetic eruptive events (Moon et al. 2003; Jiang et al. 2008, 2011; Török et al. 2011; Schrijver & Title 2011; Panesar et al. 2015). Under such a common dome of a magnetic flux system, a preceding filament eruption can easily weaken the magnetic constraint overlying other filaments and thus trigger sympathetic CMEs (e.g., Shen et al. 2012; Yang et al. 2012, 2015; Joshi et al. 2016; Hou et al. 2020). In particular, several observations reported that in helmet-streamer configurations, coronal jets can also drive streamer-puff (Bemporad et al. 2005; Moore & Sterling 2007; Panesar et al. 2016) or narrow (e.g., Wang & Sheeley 2002; Nisticò et al. 2009; Hong et al. 2011; Joshi et al. 2020) CMEs, supporting a physical link existing between these two types of eruptive phenomena. Recently, Panesar et al. (2016) found that a series of coronal jets occurring at the edge of AR 12192 resulted in homogeneous bubble-shaped CMEs. Based on the the release of magnetic twist from the jet-base field into large-scale coronal loops and related coronal dimming during the jet eruptions, they infer that the jet-guiding coronal loops eventually blew out as low-speed CME bubbles due to increasing twist.

In this paper, we study the initiation of an Earth-directed CME from a multipolar complex magnetic system, in which a large-scale CME flux rope event is found to arise from an unwinding coronal jet via magnetic coupling. With multiwavelength and stereoscopic observations from the Solar Dynamics Observatory (SDO; Pesnell et al. 2012) and Solar Terrestrial Relations Observatories (STEREO), this work presents a direct observation for the creation of a large-scale MFR by rapid twist transform in an unwinding jet spire, and sheds some light on the complex magnetic coupling in large-scale CME initiations. The layout of the remaining paper is as follows: Section 2 gives the data and methods; Section 3 presents the observational analysis and results; Section 4 presents the conclusion and discussion.

Multiwavelength EUV imaging data obtained from the Atmospheric Imaging Assembly (AIA; Lemen et al. 2012) on board SDO and Hα center images from the Global Oscillation Network Group (GONG) are used to study CME source activities. Line-of-sight (LOS) magnetograms from the Helioseismic and Magnetic Imager (HMI; Scherrer et al. 2012) are applied to study the photospheric magnetic evolution in the source region. Meanwhile, observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI; Lin et al. 2002) and the Nançay Radioheliograph (NRH; Kerdraon & Delouis 1997) are also used. The solar rotation of all these solar disk imaging data was removed through registering to a proper reference moment (09:30 UT). In addition, the CME and associated phenomena are detected from the inner to the outer corona with the combination observations from the Large Angle and Spectrometric Coronagraph (LASCO; Brueckner et al. 1995) on board the Solar and Heliospheric Observatory and Extreme Ultraviolet Imager (EUVI; Wuelser et al. 2004) on board STEREO-A and B.

Based on the Spaceweather HMI Active Region Patch (SHARP; Bobra et al. 2014) vector field products of AR 11515, the photospheric vertical electric current (J_z ) in the source region is computed from the direct observed horizontal field according to Ampere's law: ${{\boldsymbol{J}}}_{z}=\tfrac{1}{{\mu }_{0}}{( \triangledown \times {\boldsymbol{B}})}_{z}$. To reveal the pre-eruption magnetic field configuration, we "preprocessed" the Lambert cylindrical equal-area vector magnetograms to best suit the force-free condition, and then used them as the photospheric boundary to conduct a series of nonlinear force-free field (NLFFF) magnetic field modeling with the weighted optimization method (Wheatland et al. 2000; Wiegelmann 2004).

With these NLFFF and potential field (PF) magnetic extrapolation modelings, coronal magnetic free energy (E_f ) can be computed within a certain volume V as follows: ${E}_{f}\,={\int }_{V}\tfrac{{B}_{N}^{2}}{8\pi }{dV}-{\int }_{V}\tfrac{{B}_{P}^{2}}{8\pi }{dV}$, where the subscripts N(P) denote NLFFF(PF) extrapolated magnetic field (Sun et al. 2012). In addition, newly injected magnetic energy from the below the photosphere is also estimated from the energy (Poynting) flux that crosses the photospheric surface as follows (Liu & Schuck 2012): $\tfrac{{{dE}}_{{in}}}{{dt}}=\tfrac{1}{4\pi }{\int }_{S}{B}_{t}^{2}{V}_{\perp n}$ ${dS}-\tfrac{1}{4\pi }{\int }_{S}({{\boldsymbol{B}}}_{t}\cdot {{\boldsymbol{V}}}_{\perp t}){B}_{n}{dS},$ where the emerging term (first term) comes from the emergence of magnetic tubes from the solar interior, and the shearing term (second term) is generated by shear motions on the solar surface.

The multipolar flux magnetic system that bred the solar eruptive event of our interest consists of two intercoupled ARs (NOAA 11514 and 11515; see Figure 1(b)). As shown in Figure 1(a), the major flare (SOL2012-07-02T10:48) belongs to a short-duration one, which started, peaked, and rapidly ended at around 10:43, 10:48, and 10:57 UT, respectively. Previously, Louis et al. (2014) studied the sunspot splitting of AR 11515 and emphasized its role in triggering the major flare. Different from their study, here we mainly investigate CME initiations and related magnetic coupling processes. Note that this solar eruption simultaneously resulted in two successive Earth-directed CMEs (see Figures 1(c1)–(c2)), but the second is the one of our interest since it is closely related to the formation and eruption of a large-scale CME flux rope.

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From 211 Å observation and PF extrapolations in Figures 1(d) and (e), it can be seen that this multipolar flux system consisted of at least three groups of opposite-polarity magnetic fluxes: P1–N1, P2–N2, and P3–N3. As two bundles of high-lying coronal loops, L1 connected N2 and P2, while L2 connected P1/P2 and remote negative background magnetic fluxes; instead, L3 connected P1 to N3 and disperse background fields. At the adjacent footpoints of L1 and L2, a small solar filament (F1) with a length of ∼45 Mm resided in a newly emerged magnetic system (P1–N1).

Via NLFFF modeling, the pre-eruption magnetic configuration above the source region is better presented in Figures 2(a) and (b). In 3D perspectives, one can notice that there exist two privileged positions for the occurrence of magnetic reconnection: an opposite-polarity interface in POS1 and a null point in POS2, according to 3D reconnection theory (Demoulin et al. 1994). POS1 corresponds to the interface between L1 and the emerging magnetic system P1–N1. Within this system, the filament structure of F1 is mainly constrained by a bundle of arch loops (yellow lines) that connects P1 and N1. Accordingly, the maximum twist number of F1 is derived as −0.88 turns from the NLFFF extrapolation by the equation ${T}_{w}=\tfrac{1}{4\pi }{\int }_{L}\alpha {dl}$ (Berger & Prior 2006). Meanwhile, near the north section of the filament structure, there exists a null-point-type configuration (blue lines, L3), which arched its outer spine to the remote negative-polarity flux N3 and partially restrained the filament structure with its inner spine lines.

Before the occurrence of the major eruption, a so-called coronal geyser site (Paraschiv et al. 2020) formed the interface at the POS1. As shown in Figures 2(c)–(e) and its animation, four recurrent coronal jets successively took place there with similar narrow jet spires and evident plasma heating signals (especially the hard X-ray emission and chromospheric flaring patch in Figures 2(d) and (e)). Such analogous dynamics features suggest that these recurrent jets are homologous ones (e.g., Chen et al. 2015; Liu et al. 2018; Lu et al. 2019; Paraschiv et al. 2020).

On the photosphere, as shown in Figure 3, the ongoing emerged N1 kept converging toward P2 forming an emergence-driven canceling interface between N1 and P2, which spatially coincides with POS1. During 00:00 to 18:00 UT, N1 successively increased its flux from 1.9 × 10²² to 3.2 × 10²² Mx, while the positive flux demonstrated a weak decrease from 06:00 to 12:00 UT (see Figure 3(d1). Moreover, along this canceling interface, enhanced vertical current flux density J_z concurrently built up with an elongated pattern (see Figure 3(a3)). The integrated curves of its unsigned vertical current, I_out and I_in, both demonstrate an increasing trend during this 18 hr (see Figure 3(c2)). As responses of recurrent jets, episodes of analogous flaring patches took place along the localized J_z enhancement. These results support that recurrent jets were triggered by repetitive reconnection at POS1 (e.g., Archontis et al. 2010; Guo et al. 2013).

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With the occurrence of recurrent jets, the high-lying L1 underwent sudden expansions at the same time (see Figure 2(a) and the accompanying animation), implying a sudden reconstruction of magnetic topology. More importantly, soon after the appearance of the fourth jet, F1 suddenly erupted from coronal geyser site at around 10:45 UT. To better describe this process, a spacetime plot is made along the green slice 1 in Figure 2(e), which both goes through the southeast end of F1 and the ejecting trajectory of coronal jets. The result is presented in Figure 2(f) with the comparison of the GOES flux curve. From which one can intuitively see that before its final eruption: (1) four preceding recurrent jets correspond to the four peaks in the GOES flux curves and source-region AIA fluxes (also see Figure 1(a)); (2) with the occurrence of recurrent jets, F1 displayed a quasi-static ascent. This indicates that such preceding flux peaks and recurrent jets might be considered as precursors for the imminent main eruption.

As shown in in Figure 3(d1), during the occurrence of recurrent jets and the main eruption, the time profile of magnetic free energy in the source region underwent three obvious drops. Thereinto, the former two respectively released 1.5 × 10³¹ and 1.3 × 10³¹ erg of free energy, while the last drop that includes the main eruption released 2.2 × 10³¹ erg of free energy. Meanwhile, mainly due to the emergence term of Poynting flux, around 4.5 × 10³¹ erg of magnetic energy was injected upward from the below the photospheric surface and refilled such a free energy decrease (see Figure 3(d2)).

Via interacting with its overlying null point configuration (POS2; see Figure 2(b)), the erupting F1 soon underwent a rapid disintegration and triggered the M5.6-class flare (see Figures 4(a1)–(a3)). As a result, typical signals of null-point reconnection, including a quasi-circular flare ribbon and a remote brightenings, were detected around the main flare ribbon (e.g., Masson et al. 2009; Zhang et al. 2016; Li et al. 2018, 2019). As the filament disintegration proceeded, the north (also positive-polarity) feet of F1 remained line-tied at its original position, but its south feet appeared as an "open" jet spire. Accordingly, the filament plasma rapidly ejected toward the southeast possibly along L1 and also displayed a conspicuous counterclockwise unwinding motion (see Figures 4(b1)–(b3) and (c1)–(c3)). Compared with those preceding narrow and collimated jets, this unwinding jet can be characterized as a so-called blowout jet due to its broader jet spire (Moore et al. 2010).

Assuming the main axis of the unwinding jet spire can be regarded as a circular cylinder and its fine threads rotates rigidly, a rough twist calculation of such an unwinding jet spire can be given (e.g., Shen et al. 2011; Chen et al. 2012; Hong et al. 2013; Li et al. 2015; Liu et al. 2018, 2019). In Figures 4(d1) and (d2), two spacetime plots are made perpendicular to its jet spire (along the red slices S2 and S2 in Figure 4(c3)). One can see that rolling motions nearly perpendicular to the jet spire display as dark/bright strips, which last for 42 and 50 minutes in (d1) and (d2), respectively. By tracing and conducting linear fittings along these inclined dark/bright strips, the average rotational speed (ν_r ) of this unwinding jet can be estimated as 48.5 km s⁻¹ and 38.2 km s⁻¹, respectively. The average width of the jet spire (23.09 Mm and 21.40 Mm) is equal to its diameter (d). Accordingly, their angular speeds (ω = 2ν_r /d) along S2 and S3 are computed as 3.57 × 10⁻³ rad s⁻¹ (period 1758 s) and 4.20 × 10⁻³ rad s⁻¹ (period 1494 s), respectively. So the total amount of twist released in this jet spire is roughly at 1.43−2.01 turns, or 2.86−4.02π. This result reaches an agreement with other previous twist estimations (1.2−4.7 turns) in comparable coronal jets (e.g., Shen et al. 2011; Chen et al. 2012; Moore et al. 2013, 2015; Li et al. 2015; Liu et al. 2019). Note that the median twist number of pre-eruption F1 is derived as 0.88 turns from the NLFFF extrapolation. A similar disagreement is also found in Liu et al. (2018). We think the twist estimation by the feature tracing method is more reliable, because (1) the feature tracing method involves fewer assumptions, and (2) the low-lying F1 might require a sophisticated non-force-free modeling due to its small scale.

Due to the unwinding dynamics, new filament feet gradually appeared within the "open" jet spire and demonstrated an apparent slipping motion toward the south (see Figure 4(c3)). By the time of 11:28 UT, the jet-like plasma ejecta traced out a newborn closed magnetic structure. With the inspection of AIA (see the animation of Figure 4) and STEREO-A/EUVI observations, we found that the newborn closed magnetic structure actually corresponds to a newborn large-scale MFR. Especially near its north feet, prominent magnetic twist fields and counterclockwise unwinding (rolling) motion indeed exist (see Figure 4(c1) and the accompanying animation). It must be pointed out that the creation of this newborn large-scale MFR is accomplished at a relatively high coronal height, thus it soon erupts upward.

Figure 5 further presents this eruption process with a larger field of view (FOV). In H_α observations, this erupting large-scale MFR manifested as an obvious erupting filament against the solar disk, and rapidly disappeared by the time of 11:25 UT (see Figures 5(a) and (b)). In running-difference 211 Å images, it is found that as the major flare triggered, an EUV wave propagated toward the south, which might be the coronal imprint of the first CME (CME1; also see Figure 1(c1)). After the major flare, the large-scale MFR arose from the coronal geysers and slowly erupted toward the southwest, which eventually led to the second CME (CME2). This jet–CME coupling eruption needs to be differentiated from the simple extension of coronal jets in white-light observations (Wang & Sheeley 2002; Hong et al. 2011; Joshi et al. 2020) and other so-called twin CME events (Shen et al. 2012; Duan et al. 2019; Miao et al. 2019), because a newborn large-scale MFR was indeed created during the solar eruption by the rapid twist transport from jet-base to background fields.

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In particular, two unique features are found in the eruption of the large-scale MFR. First, as mentioned before, the newborn south feet of the large-scale MFR showed an apparent "drift" toward the south in 304 and 211 Å imaging observations. This evolution behavior is also evidenced by simultaneous radio imaging observations at 298 MHz from NRH, which corresponds to a computed height of around 170 Mm above the photosphere based on the coronal density model of Sittler & Guhathakurta (1999) and the plasma-density relationship ($f=8.98\times \sqrt{{n}_{e}}$). As energetic electrons were injected into and filled its erupting volume, the feet of the newborn large-scale MFR were clearly imaged as a pair of distinct radio sources in Figure 5(c). Similar feet signatures of eruptive MFRs were also reported by other previous radio imaging observations (e.g., Carley et al. 2020; Chen et al. 2020), but the feet radio source usually remain stationary. In this current observation, the north one remained stationary at its spatial position, while the south one first appeared at around 10:55 UT, and demonstrated a south-oriented "drift" during 11:00 to 11:29 UT (see Figures 5(g)–(i)).

Second, signatures of an extra flare reconnection were detected below the erupting large-scale MFR. As shown in Figures 4(b4) and (c4), by the time of 12:10 UT, a set of new postflare loops (second post-flare loops (PFLs)) formed behind the erupting large-scale MFR, bridging a newly formed chromospheric ribbon and the main flare region. Accordingly, RHESSI sources were also detected at the looptop of new postflare loops (see Figure 5(b4)), indicating the occurrence of particle acceleration. On the whole, the creation of a large-scale MFR and the appearance of the second PFLs provide solid evidence for this jet–CME coupling eruption. In the GOES flux, as shown in Figure 1(a), the associated X-ray emission enhancement in the second PFLs is also clearly detected as another C-class flare. Together with the jet-driven M5.6-class main flare, this result supports that this coupling eruption event involves two stages of flare magnetic reconnection.

With the aid of stereoscopy observations from STEREO, it becomes more evident in Figure 6 that the blowout jet first appeared along the high-lying loop L1, and then the newborn large-scale MFR displayed as a giant prominence eruption with two feet rooted at the source region "C" (marked by the black dashed box) and a remote region "D," respectively. The distance between "C" and "D" spans more than 270 Mm. With a close-up inspection, one can even notice that a counterclockwise rolling motion appeared in the north leg of the erupting large-scale MFR, which indicates an obvious transfer of magnetic twist took place from the feet "C" to the other feet "D" (also see Figures 6(c1)–(c2)). In the right part of Figure 6, the white-light coronagraphs from STEREO COR1 and COR2 well recorded its related CME. CME2 first appeared at 13:22 UT and successfully propagated to more than 18 R_s with a relative low velocity of around 300 km s⁻¹.

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CMEs and coronal jets are two types of common solar eruptive phenomena, which often independently happen at different spatial scales. The former are well known for stellar-sized violent magnetized plasma explosions and their potential capacity in causing hazardous space weather (e.g., Chen 2011; Schmieder et al. 2013), while the latter, as ubiquitous smaller-scale eruptive phenomena, are best known for their important contributions to the heating and mass supply for the upper solar atmosphere (e.g., Tian et al. 2014; Raouafi et al. 2016; Samanta et al. 2019; Shen 2021). In this paper, we study the origin of a large-scale CME flux rope event arising from an unwinding coronal jet. Based on the stereoscopic and multiband observational analysis, we find that this whole eruptive event started with a small-scale filament within a multipolar complex magnetic system whose eruption first triggered an unwinding blowout jet and an M5.6 short-duration flare. Due to the subsequent release of magnetic twist from the jet base, a newborn larger-scale MFR was then created in the unwinding jet spire, with its new south feet exchanged to a remote site (around 270 Mm from the jet base). Finally, this newborn large-scale MFR successfully erupted into the outer coronae driving a stellar-sized Earth-directed CME, leaving another C1.8 flare in its source region. On the whole, this event highlights the pathway of a real magnetic coupling process in the initiation of the Earth-directed CME, supporting the view that some large-scale coronal eruptive phenomena can originate from the magnetic coupling of different magnetic activities at various spatial scales (Wang et al. 2007, 2015; Schrijver et al. 2013).

Despite that the fast release of magnetic twist phenomena are often detected in blowout jet events (Curdt & Tian 2011; Shen et al. 2011; Chen et al. 2012; Hong et al. 2013; Moore et al. 2013, 2015; Li et al. 2015; Joshi et al. 2018; Liu et al. 2019; Yang et al. 2019) and filament eruption events (e.g., Yan et al. 2014, 2020; Jiang et al. 2018), their resulting consequences are as of yet poorly studied. This work provides a direct stereoscopic imaging observation on the creation of a large-scale erupting CME flux rope in an unwinding coronal jet. Different from previously mentioned flux-emergence formation mechanisms (e.g., Fan & Gibson 2004; Manchester et al. 2004; Okamoto et al. 2008; Chen et al. 2018; Yang & Chen 2019) and reconnection-cancellation formation mechanism (e.g., Savcheva et al. 2012; Wang et al. 2017, 2018; Chen et al. 2018, 2019), this observation supports an alternative scenario: the rapid magnetic twist transport from the jet base to background fields directly results in the formation of a newborn large-scale MFR. Moreover, a rough twist estimation of the blowout jet indicates that around 1.43−2.01 turns of magnetic twist were released in its jet spire. The twist characteristics of the newborn large-scale flux rope and its counterclockwise rolling motion can also be clearly recognized in STEREO/EUVI observations. In addition, the location of its "drift" remote feet is also confirmed as a moving radio source in simultaneous NRH radio observations.

Apart from our observation, applying state-of-the-art data-constrained 3D MHD simulations and observations, Jiang et al. (2018) also noticed that in NOAA 11283, an erupting sigmoidal flux rope breaks one of its legs, and quickly gives birth to a new tornado-like flux rope that is highly twisted and has multiple connections to the Sun (see also a similar 3D simulation from Prasad et al. 2020 that focuses on the same event but mainly studies its related coronal dimmings). Panesar et al. (2016) also reported a series of coronal jets occurring at the edge of AR 12192, which resulted in homogeneous bubble-shaped CMEs. Based on the release of magnetic twist from the jet-base field into large-scale coronal loops and related coronal dimming during the jet eruptions, Panesar et al. (2016) inferred that the jet-guiding coronal loops eventually blew out as low-speed CME bubbles due to increasing twist. Focusing on one of these CME-producing jets, Li et al. (2015) also provided a detailed twist estimation in the jet spire with high-resolution chromospheric observations, and they reported that the total rotation angle is high up to 8π. In the current work, the estimated rotation angle in the unwinding jet ranges from around 2.8−4.0π, which should be enough for the creation of the newborn CME flux rope.

Before the occurrence of the blowout jet, repetitive reconnection triggered four obvious recurrent jets above an elongated J_z enhancement between opposite-polarity converging fluxes (P2 and N1, namely, at POS1). These recurrent jets demonstrate a narrow jet spire and short lifetime, thus may be termed as "standard" jets, while the blowout jet of our interest has a broader unwinding spire and is triggered by a microfilament eruption scenario (Moore et al. 2010; Sterling et al. 2015). In their source region, flux emergence provided a continual injection of Poynting flux and magnetic free energy for recurrent eruptions (see Figures 3(d1)–(d2)). On the other hand, flux emergence also introduced an emergence-driven canceling interface. As a result, reconnection between F1-contained newly emerged flux and preexisting field happened, which weakened its constraint above the F1 to some degree (Sterling et al. 2007; Panesar et al. 2015; Yang & Chen 2019). Consistent with the results of Louis et al. (2014) and Sterling et al. (2016), these suggest that both flux emergence and its driven flux cancellation should play a role in the onset of this whole magnetic coupling eruption.

As a final remark, two issues are worth mentioning here. First, in order to fully understand such jet–CME coupling eruption events, the energetics and interplanetary effects of jet-driven CMEs should be linked back to their jet-base parameters in the future, especially the twisting effect of pre-jet filaments. Second, it must be pointed out that this newborn large-scale CME flux rope in the present observation immediately erupted due to its higher formation height, despite that it actually was created along an extended PIL. ⁵ Therefore, whether this twist-transport formation scenario can apply to explain the appearance of those long-term exited large-scale MFRs among intercoupled ARs (e.g., Zhou et al. 2019, 2020) remains unclear.

The authors sincerely thank the referee for constructive suggestions and comments. H.C.C. thanks Dr. Guiping Zhou for helpful discussions after the online seminar, "Frontiers in solar physics," held by the Key Laboratory of Solar Activity of NAO. H.C.C. is supported by the National Postdoctoral Program for Innovative Talents (BX20200013) and China Postdoctoral Science Foundation (2020M680201). This work is also supported by the National Key R&D Program of China (2019YFA0405000), and the National Natural Science Foundation of China under grants 11633008, 11873088, 11933009, and 11703084.