Coronal-Jet-Producing Minifilament Eruptions as a Possible Source of Parker Solar Probe (PSP) Switchbacks
aa r X i v : . [ a s t r o - ph . S R ] J un Draft version June 11, 2020
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Coronal-Jet-Producing Minifilament Eruptions as a Possible Source of Parker Solar Probe (PSP) Switchbacks
Alphonse C. Sterling and Ronald L. Moore
1, 2 NASA/Marshall Space Flight Center, Huntsville, AL 35812, USA Center for Space Plasma and Aeronomic Research,University of Alabama in Huntsville, Huntsville, AL 35805, USA
ABSTRACTThe Parker Solar Probe (PSP) has observed copious rapid magnetic field direction changes in thenear-Sun solar wind. These features have been called “switchbacks,” and their origin is a mystery.But their widespread nature suggests that they may be generated by a frequently occurring processin the Sun’s atmosphere. We examine the possibility that the switchbacks originate from coronal jets.Recent work suggests that many coronal jets result when photospheric magnetic flux cancels, andforms a small-scale “minifilament” flux rope that erupts and reconnects with coronal field. We arguethat the reconnected erupting minifilament flux rope can manifest as an outward propagating Alfv´enicfluctuation that steepens into an increasingly compact disturbance as it moves through the solar wind.Using previous observed properties of coronal jets that connect to coronagraph-observed white-lightjets (a.k.a. “narrow CMEs”), along with typical solar wind speed values, we expect the coronal-jet-produced disturbances to traverse near-perihelion PSP in < ∼
25 min, with a velocity of ∼
400 km s − .To consider further the plausibility of this idea, we show that a previously studied series of equatoriallatitude coronal jets, originating from the periphery of an active region, generate white-light jets inthe outer corona (seen in STEREO /COR2 coronagraph images; 2.5—15 R ⊙ ), and into the innerheliosphere (seen in STEREO /Hi1 heliospheric imager images; 15—84 R ⊙ ). Thus it is tenable thatdisturbances put onto open coronal magnetic field lines by coronal-jet-producing erupting minifilamentflux ropes can propagate out to PSP space and appear as switchbacks. Keywords:
Solar filament eruptions, solar magnetic fields, solar magnetic reconnection, solar wind INTRODUCTIONThe Parker Solar Probe (PSP) mission (Bale et al. 2016; Fox et al. 2016; Kasper et al. 2016) has for the first timecarried out in situ observations in the near-Sun solar wind, reaching ∼ R ⊙ in 2018 November and also in 2019April. An exciting early observation from the mission is that the near-Sun magnetic field is replete with transient,kinked structures that have been called “switchbacks” (Bale et al. 2019; Kasper et al. 2019; Dudok de Wit et al. 2020;Mozer et al. 2020). Similar structures were also seen earlier (e.g., Kahler et al. 1996; Yamauchi et al. 2004; Suess2007). The source of these features is not understood. A possibility that we investigate here is that solar coronal jetsmight be responsible for the switchbacks (as suggested by, e.g., Horbury et al. 2020).Here we examine the possibility that a recently suggested process for making coronal jets, based on the eruption ofsmall-scale filaments and their enveloping field that reconnects with coronal field, results in the switchbacks. CORONAL JETS AND WHITE-LIGHT JETS2.1.
Coronal Jets
Coronal jets have been observed for some time at X-ray (e.g. Shibata et al. 1992; Cirtain et al. 2007) and EUV (e.g.Nistic`o et al. 2009) wavelengths. They are frequently occurring phenomena, with a rate of about 60/day in polarcoronal holes alone (Savcheva et al. 2007). For reviews of jets, see Shibata & Magara (2011), Raouafi et al. (2016),and Hinode Review Team et al. (2019).Recent observations support that at least many, if not most or all, coronal jets result from the eruption of a small-scalefilament, or minifilament , and its enveloping magnetic field. Sterling et al. (2015) proposed a “minifilament-eruptionmodel” for coronal jets, and argued that the entire coronal-jet event is a scaled-down version of the larger-scale eruptionsthat create typical solar flares and CMEs. Apparently almost all coronal jets, at least those in quiet Sun and coronalhole regions, are produced by such eruptions. Often the small-scale erupting field contains cool material (appearing asthe minifilament) in the core of the erupting magnetic arcade (e.g. Hong et al. 2014; Moore et al. 2010; Shen et al. 2012,2017, 2019; McGlasson et al. 2019), where the eruption can be either ejective or confined (Sterling et al. 2015). Wecannot however totally rule out that some other process, such as the much-earlier-suggested emerging-flux mechanism(Shibata et al. 1992; Yokoyama & Shibata 1995), might produce some jets and expel cool material into the corona.Other observations show that the coronal jets originate at photospheric locations where magnetic flux cancela-tion occurs under the pre-eruption minifilament (e.g. Shen et al. 2012; Hong et al. 2014; Young & Muglach 2014a,b;Panesar et al. 2016b). We have found observational evidence that in many cases magnetic flux cancelation creates theminifilament flux rope and triggers the eruption of the flux rope and its enveloping magnetic arcade, and this eruptionproduces the coronal jet (Panesar et al. 2016b, 2017; Sterling et al. 2017; Panesar et al. 2018a; McGlasson et al. 2019).An alternative view argued by Kumar et al. (2018) is that often shearing and/or rotational photospheric motion isresponsible for the build up of energy along the minifilament channel that gets released through eruption and producesthe jet.Figure 1 shows the basic minifilament-eruption jet-production idea of Sterling et al. (2015). Figure 1(a) shows across-sectional view of a 3D positive-polarity anemone-type field inside of a majority negative-polarity ambient openfield. One side of the anemone is highly sheared (and often twisted) and contains a minifilament (blue circle). InFigure 1(b) the minifilament field is erupting and undergoing reconnection in two locations: (1) internal (“tether-cutting” type) reconnection (larger red X), with the solid red lines showing the resulting reconnected fields, and wherethe thick red semicircle represents the “jet bright point” (JBP) at the jet’s base; and (2) external (a.k.a. “interchange”or “breakout”) reconnection occurs at the site of the smaller red X, with the dashed lines indicating its two reconnectionproducts. Figure 1(c) shows that if the external reconnection proceeds far enough, then the minifilament material canleak out onto the open field. Shaded areas represent heated jet material visible in X-rays and some
SDO /AIA EUVchannels as the jet’s spire. This picture has been successfully simulated by Wyper et al. (2017, 2018) (they refer tothis “minifilament-eruption model for jets” as a “breakout model for jets,” since breakout-type reconnection is integralto the jet’s production).Active region (AR) coronal jets similarly show evidence that they are made from small-scale eruptions, and thatthese eruptions are prepared and triggered by magnetic flux cancelation. It seems however as if the eruptions leadingto AR jets less frequently (than in non-AR areas) carry cool material that appears as a minifilament, although evidenceindicates that a minifilament-type flux-rope field still erupts to make the AR jets (Sterling et al. 2016, 2017).2.2.
White-light Jets and Twists on Coronal Jets
Coronal jets are capable of producing features observed in coronagraphs called “narrow CMEs” or “white-lightjets” (e.g., Wang et al. 1998; Nistic`o et al. 2009; Moore et al. 2015; Sterling et al. 2016). Such studies showed aclear connection between coronal jets on the Sun and the white-light jets observed with either the
STEREO
COR1coronagraph (Nistic`o et al. 2009, 2010; Paraschiv et al. 2010), or in the LASCO C2 coronagraph (Wang et al. 1998;Moore et al. 2015; Sterling et al. 2016). In other cases, jets can apparently propel outward – or at least accompany– broader “bubble-like” CMEs (e.g. Bemporad et al. 2005; Shen et al. 2012; Alzate & Morgan 2016; Panesar et al.2016a; Miao et al. 2018; Duan et al. 2019; Solanki et al. 2019); our focus here however is on the narrow CMEs.Several studies have found twist on jets (e.g. Pike & Mason 1998). A few such investigations have measured thenumber of turns a jet undergoes over its lifetime; Shen et al. (2011b) found a jet to undergo 1.2 to 2.6 turns, whileChen et al. (2012) estimated the same jet to undergo 3.6 turns. Hong et al. (2013) estimated a different jet, one thatmay have produced a white-light jet, to undergo 0.9 turns. Moore et al. (2013) found that 24 of 29 (83%) random polarjets that they examined had one-half or fewer turns, while the remaining five events had up to 2.5 turns. Liu et al.(2019) studied 30 off-limb “large-scale rotational” coronal jets, and found that they all underwent at least 1.3 turnsand 80% of them rotated less than 2.8 turns, with the one with maximal rotation having 4.7 turns. References inLiu et al. (2019) discuss other papers with jet-twist measurements.Moore et al. (2015) studied 14 jets that produced white-light jets, and found that they had twist values of one-halfto 2.5 turns. They argued that an erupting twisted flux rope (which in subsequent papers we argue is a minifilamentflux rope) can inject twist onto the white-light jet. A conclusion of their study was that all of the coronal jets thatmade white-light jets in their study had comparatively large amount of twist in the spire of the coronal jets whenobserved in AIA 304 ˚A. Thus it was apparent that the twist was an important factor for the coronal jets to make itout to a few R ⊙ into the corona.Figure 2 shows our picture for how a coronal-jet-producing minifilament eruption could launch a white-light jet.Initially the minifilament field that erupts to form the coronal jet would carry twist, as in Figure 2(a). When this twistederupting flux rope strikes ambient field of opposite polarity in Figure 2(b) (corresponding to Fig. 1(b)) and undergoesexternal reconnection, that reconnection transfers twist onto the ambient open field, as proposed by Shibata & Uchida(1986). This twist would propagate outward (Fig. 2(c)) as an Alfv´enic twist-wave packet, driving the white-light jetseen in coronagraph images. Eventually (2(d)) the near-original setup is recovered, but with the imparted twist fromthe reconnected minifilament field now removed from in and near the jet’s base field. POSSIBLE PRODUCTION OF SWITCHBACKS BY PROPAGATING MAGNETIC TWIST ONWHITE-LIGHT JETSFigure 3 is a continuation of Figure 2, showing how the twist imparted to an open field by a coronal-jet-producingminifilament eruption evolves into a switchback, where the yellow circles represent the Sun, and the blue lines representheliospheric field lines that are curved, following a Parker spiral, with respect to a radial line (black). The twist putonto the white-light jet (Fig. 2(c)) will continue to propagate out into the heliosphere. In Figure 3(a), the twist isshown as an extension to the situation in Figure 2(c), with the twist having about the same small pitch angle as seenin the C2 images of Fig. 6 of Moore et al. (2015).In Figure 3(a), the twist imparted to the ambient coronal field in Figure 2(c) continues to propagate outward,becoming the red disturbance that appears as a low-pitch twist wave packet moving outward (the radial extent of thetwist packet would be comparable to a solar radius, and so is exaggerated by a factor of ∼ V A ≈ − . At the first PSP perihelion, Bale et al. 2019 report V A ∼
100 km s − in thesolar wind at 36.6 R ⊙ .) Based on Moore et al. (2015), the disturbance in C2 has length L comparable to R ⊙ . Thefront of the disturbance moves more slowly than its rear, resulting in a “compression” (increasing pitch angle) of thedisturbance. In Figure 3(c), this pitch-angle steepening of the disturbance continues as it moves even further from theSun, appearing as a “switchback” by the time it encounters PSP.PSP would detect the Alfv´en-wave packet as the packet flows and propagates by. The radial speed of the packetwill vary depending on its distance from the Sun. At the time of its launch in the low corona, the packet would have aspeed of about that of the local coronal Alfv´en speed ( ∼ − ), with a solar wind velocity, V SW , of practicallyzero. At PSP, the Alfv´en velocity will be ∼
100 km s − as mentioned above, but it will be riding in the solar windwith V SW ≈
300 km s − (which is the baseline solar-wind speed reported by Kasper et al. 2019 during the first PSPperihelion passage); that is, it will pass PSP at about 400 km s − .The length of the packet, L , at the Sun will be about V A × τ , where we can take τ ≈
600 s, since a typicalcoronal jet lasts about ten minutes (e.g., Savcheva et al. 2007). So the pulse’s length near the Sun, L cor , wouldbe L cor ∼ − would appear as a pulse passingthe spacecraft in 1500 s, i.e. ∼
25 min. The Alfv´en-wave-packet’s length at the spacecraft, L P SP , however will bereduced from what it was in the corona, via the above-argued pitch-angle-steepening rationale. Thus the passage ofthe pulse (the switchback) past PSP should be less than about 25 min. Smaller-scale “network jets” (or “jetlets”) (e.g.Raouafi & Stenborg 2014) appear to work like typical coronal jets (Panesar et al. 2018b). Thus these smaller eventsplausibly produce many briefer switchbacks in the solar wind. Observed switchbacks have durations ranging from lessthan a second to more than an hour (e.g. Dudok de Wit et al. 2020). OBSERVATIONS OF CORONAL JETS IN THE
STEREO
OUTER CORONAWhile §§ §
1, there have been several observations of the effects ofcoronal jets out to the
STEREO /COR1 (1.5—4 R ⊙ ; Howard et al. 2008) and LASCO C2 (1.5—6 R ⊙ ) distances. Polarcoronal jets have been tracked even further, into the STEREO /COR2 (2.5—15 R ⊙ ) field of view (FOV), and thenas density enhancements at substantial fractions of an A.U. in 3D reconstructions from Solar Mass Ejection Imager( SMEI ) data in recent studies (Yu et al. 2014, 2016).In this section we present observations of another example of the signatures of coronal jets propagating into theouter corona and inner heliosphere. Our example differs from those of Yu et al. (2014, 2016) and Moore et al. (2015),in that their examples originate from polar coronal hole jets, while our examples here originate from coronal jets atequatorial latitudes and from the periphery of an active region. Our coronal jets are the same as those of Sterling et al.(2016), and that paper showed the jets connecting to white-light jets in the
STEREO /COR1 FOV. Here we show thatsome of the coronal-jet signatures can be tracked to locations farther from the Sun.4.1.
Coronal-Jet Origins
We give a brief summary of the solar origins of the coronal jets, more details of which are provided in Sterling et al.(2016). That paper studied a series of coronal jets that occurred at the edge of NOAA AR 11513. While theyprimarily used
SDO /AIA data for their analysis, they also used complementary views from
STEREO -B and showedthat many of their coronal jets produced white-light jets in the
STEREO -B COR1 FOV. While the AIA imagesshowed that the COR1 features originated from several locations around the AR, here we concentrate on the featuresthat made white-light jets in COR1 at a position angle of ≈ ◦ ; this is because it is at about this same position anglewhere we can identify white-light jets further out in the corona. From the COR1 coronagraph video of Sterling et al.(2016) (the video accompanying Fig. 5 in that paper), it can be seen that the white-light jets from this position anglelargely originated from location of the AR labeled “C” in that paper (see Fig. 3(a) of Sterling et al. 2016). Hence weconcentrate on coronal jets from that location in the following.Figures 4(a—c), and accompanying video vid4abc, show coronal jets from this location in AIA 304 ˚A, and Fig-ures 4(d—f) and accompanying video vid4def show the magnetic evolution of the region in SDO /HMI magnetograms.Table 1 lists the primary jets occurring from this location over 19:00—23:50 UT on 2012 June 30, which is the timeperiod we will focus on. Figures 4(a—c) track the progress of jet J5 of table 1.As discussed in Sterling et al. (2016), the coronal jets from this location originate from either of the two neutrallines pointed to by the yellow and red arrows in Figure 4(d). Over the time of Figures 4(d—f), the positive-polaritypatch between these arrows decreases in size; from video vid4def, this decrease is consistent with convergence of thepositive-polarity flux patch and surrounding negative-polarity flux, resulting in flux cancelation. From this observation,in conjunction with our understanding of coronal-jet initiation outlined in §
1, we conclude that it is likely that fluxcancelation built a minifilament field that erupted to make the coronal jets, following the picture of Figure 1. Thecontinued cancelation is responsible for the continuing series of essentially homologous coronal jets (Panesar et al.2016a; Sterling et al. 2017).In their study of 14 polar coronal hole jets, Moore et al. (2015) found that coronal jets that extended into white-lightjets in the LASCO/C2 FOV tended to be those with relatively high amounts of twist when observed in AIA 304 ˚Aimages. Those jets reaching C2 had between 0.5 and 2.5 axial turns, with a peak near 1.5 turns. In contrast, theyfound that a more general population of 29 jets had axial rotations mostly between zero and 0.5 turns. Thus the jetsthat reach C2 preferentially have more twist than the general population of coronal hole jets.Our coronal jets here are from an AR rather than a coronal hole, but we can ask whether these jets show spinningmotions. Inspection of the 304 ˚A movie vid4abc shows that several jets indeed appear to spin during their onset phase.We estimate the number of turns that each jet makes using same basic procedure as in Moore et al. (2015), specificallyby picking a feature on the jet, tracking its lateral motion, and counting how many apparent oscillations it makes inthe left-right (east-west) direction it makes during the early part of the jet. The black arrows in Figure 4(a—c) showan example, where we track an absorbing feature in jet J5 of table 1. Table 1 provides our results, giving our estimatednumber of turns for each jet. Other than jet J3, all of the jets show obvious indications of spin, where the values rangefrom 0.25 to 1.5 turns, with an average of 0.8 turns. Only two of the eight jets (J3 and J6) have spin values smallerthan the 0.5 lowest value of the Moore et al. (2015) coronal jets that made white-light jets.Even though our interpretation of coronal-jet spin is based on visual inspection only, there is strong evidence fromspectral studies providing evidence from Doppler measurements that many jets truly spin (e.g. Pike & Mason 1998;Kamio et al. 2010). Similar to the situation in Moore et al. (2015), the appearance is that the spinning is an unwinding of the field containing the cool 304 ˚A jet material, as the spinning eventually slows and stops in all of the cases.We measured the outflow velocities of the coronal jets over the FOV of Figure 4, by tracking portions of the jetspire in emission in 304 ˚A; the absorbing material (likely erupting-minifilament material) sometimes moves out at aslower velocity. Jet J6 has a velocity higher than the others; this is probably due to a stronger energy release, as itcorresponds to an explosive flare of
GOES level C1.6. Sterling et al. (2016) also found that this coronal jet extendedto a COR1 white-light jet that was the fastest of their set: 841 km s − . This is consistent with the study of Shen et al.(2011a), which provides observational evidence that the GOES class of a flare is directly related to the kinetic energyof the accompanying erupting filament. 4.2.
The Jets in the Outer Corona
Figure 5(a) shows the progression of the jets J4 and J5 into the
STEREO /COR1 coronagraph FOV, based on theresults of Sterling et al. (2016) (see Fig. 5 and accompanying video of that paper; in that paper, our jets J4 and J5 arerespectively jets 6 and 7). Figure 5(b) shows the jets in the
STEREO -B COR2 coronagraph, and the accompanyingvideo, vid5abcd, shows that this feature is clearly a continuation of the jet J4/J5 feature of Figure 5(a). From the5-min-cadence COR1 movie in Sterling et al. (2016), these two jets occur very closely together in time in COR1, andso we cannot differentiate between them in the 15-min-cadence COR2 movie (in vid5abcd, the cadence of both theCOR1 and COR2 movies are set to match the cadence of the COR2 movies). Figure 5(c) shows jet J6 of Table 1 (thisidentification between J6 and the COR1 jet was made in Sterling et al. 2016 using the 5-min-cadence COR1 movie).Figure 5d shows a white-light jet in COR2 from the same time and position angle; this is either a continuation of jetJ4/J5, or it could be jet J6, or a combination of jets, but the time cadence of COR2 is not high enough for us todetermine which of these is the case. In the COR2 video, the white-light jet of Figures 5(b) and 5(d) has velocity ofabout 800 km s − . 4.3. The Jets in the Inner Heliosphere
Figure 5 shows a COR2 image in 5(e), concurrent with a
STEREO -B Hi1 image in 5(f). Hi1 observes the innerheliosphere with a wide FOV (15—84 R ⊙ ; Howard et al. 2008), but offset from Sun center; in Figure 5(f) the Sun islocated off of the left side of the panel. From the accompanying video, vid5ef, the jet in Figure 5(f) is a continuationof one of, or a combination of some of, the Table 1 jets that have already left the FOV of Figure 5(e). We can confirmthat the location of the jet with the arrow in Figure 5(f) corresponds to the position angle of the Table 1 jets by usingthe large-scale eruption that appears in COR2 at 12:09 UT in vid5ef. That eruption is very large, and expands outinto a CME that is visible in the Hi1 video from 15:29 UT. This feature is an unmistakable continuation of the COR2eruption. In the Hi1 movie, it has a position angle slightly smaller than (just clockwise of) that of the Table 1 jets, andthis gives us confidence that the jet seen in Hi1 at a slightly larger position angle in Figure 5(f) indeed corresponds tothe jets of Table 1. (The large eruption beginning at 12:09 UT in COR2 originates from a neutral line to the east ofthe images in Fig. 4; in Sterling et al. 2016, the source location is between locations marked “A” and “B” in Fig. 3(a)of that paper.) That eruption was of a larger scale than those that make the jets at location displayed in Figure 4. Inthe Hi1 FOV, the white-light jet of Figure 5(f) has velocity of about 750 km s − ; to within the uncertainties of ourestimate, this can be regarded as about the same as the velocity of the white-light jet (or combination of jets) observedin COR2 ( § DISCUSSIONBecause coronal jets are frequent, and because recent work suggests that they are formed when magnetic flux ropeserupt away from the solar surface and reconnect with coronal field (Fig. 1), it is natural to ask whether the coronaljets could be the source of the magnetic “switchback” fluctuations observed by PSP in the near-Sun solar wind. Wehave presented a picture (Figs. 2 and 3) by which the Alfv´enic fluctuations resulting from the magnetic eruptionsthat produce the jets might evolve into switchbacks. We have also presented evidence that jets at equatorial latitudescan reach the outer corona and the inner heliosphere (Fig. 5), supplementing earlier studies of white-light jets andsolar-wind disturbances from coronal jets from polar regions ( § ◦ , such that the field literally “switches back” on itself (e.g., as in extended data Figure 2 of Kasper et al. 2019).It seems however that only a small percentage of switchbacks have such rotation angles far beyond 90 ◦ (Mozer et al.2020). Perhaps a non-linear and/or turbulent effect, or some additional process in the solar wind, could augment theprogression pictured in Figure 3(c), so that the field’s angle greatly exceeds 90 ◦ in some cases.Our suggested connection between coronal jets and switchbacks is, however, still speculation, and therefore otherideas cannot be ruled out (e.g., Tenerani et al. 2020). Mapping a switchback, perhaps a particularly large one, backalong a Parker spiral to a magnetic footpoint on which a jet or series of jets is observed with the proper timing wouldprovide support for this idea. In addition, we hope that simulations of coronal jets that include the magnetic connectionsbetween thesolarsurface and the heliosphere (e.g. Lionello et al. 2016; Roberts et al. 2018), with the addition of drivingthe event by a minifilament-field eruption, will be able to test these ideas.We thank an anonymous referee for helpful comments. This work was supported by funding from the HeliophysicsDivision of NASA’s Science Mission Directorate through the Heliophysics Guest Investigators (HGI) Program, andthe MSFC Hinode
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Table 1.
Jets in AIA 304 ˚A Movie
Event Prev. Event a Start b End c Duration [min] d Velocity [km s − ] e Rotations (time period) f COR1 vel [km s − ] g J1 — 19:07:20 — — 150 0.75 (19:14:32–19:19:20) —J2 — 19:19:56 — — 190 0.50 (19:24:44–19:29:32) —J3 5 19:30:08 19:40:20 10 255 0(?) h ± ± i ± ± . ± . ±
155 0 . ± . a Corresponding event number in Sterling et al. (2016), when determinable. b Time of earliest clear brightening at base of erupting minifilament that makes the jet. c Approximate time that base activity ceases for this event. Cannot be determined in some cases due to overlap with subsequent activity. d Difference of previous two columns. e Measured in 304 ˚A images over Fig. 3 FOV, based on movement of bright spire features during fast-rise phase (i.e., following an initial slowstart to the minifilament’s rise. f Estimated number of 2 π turns of the spire over time period given in parentheses. g White-light jet velocity in
STEREO -B/COR1 coronagraph images, as measured in Sterling et al. (2016). h Spinning motion not obvious, but hard to determine with certainty that it does not exist. i The brightening accompanying event 7 in table 1 of Sterling et al. (2016) was from a location west of the Fig. 4 FOV, but our 304 ˚A jet inthe FOV of Fig. 4 likely corresponds to the feature listed as jet 7 in the Sterling et al. (2016) COR1 movie.
Figure 1.
Schematic showing jet generation via a “minifilament eruption model,” as proposed in Sterling et al. (2015). Thisversion of the schematic appeared in Sterling et al. (2018), and includes an adjustment due to Moore et al. (2018). (a) Cross-sectional view of a 3D positive-polarity anemone-type field inside of a majority negative-polarity ambient field (which we assumeto open into the heliosphere). One side of the anemone is highly sheared and contains a minifilament (blue circle). (b) Herethe minifilament is erupting and undergoing reconnection in two locations: (1) internal (“tether-cutting” type) reconnection(larger red X), with the solid red lines showing the resulting reconnected fields; the thick red semicircle represents the “jetbright point” (JBP) at the jet’s base; and (2) external (a.k.a. “interchange” or “breakout” reconnection) occurs at the site ofthe smaller red X, with the dashed lines indicating its two reconnection products. (c) If the external reconnection proceeds farenough, then the minifilament material can leak out onto the open field. Shaded areas represent heated jet material visible inX-rays and some
SDO /AIA EUV channels as the jet’s spire. See, e.g., Sterling et al. (2015) or Moore et al. (2018) for a moredetailed description. Figure 2.
Schematic from Moore et al. (2015) of the generation of the magnetic-untwisting wave in an ejective minifilament-eruption (blowout) jet by the blowout and interchange reconnection of initially closed magnetic field at the base of the jet. At thetime of original publication in Moore et al. (2015), the full minifilament eruption model (Fig. 1) was still being developed, butseveral critical components of that model are already included here. Panels (a) and (b) show what we now call the minifilamentfield erupting, basically following Fig. 1. In this case however, the schematic emphasizes that the erupting minifilament fieldcontains twist. That twist is imparted to the ambient open field via the external reconnection in (b). This results in a relaxation(untwisting) of the reconnected twisted ambient coronal field in (c). Eventually the near-original setup ensues (d), but with theoriginal twist in the minifilament field now removed from in and near the jet’s base field. In this representation, the eruptingminifilament field has right-handed twist; this is imparted to the spire field, which then spins in a clockwise direction (viewedfrom above) to undo the imparted right-handed twist. Figure 3.
Schematic showing a continuation of Fig. 2, where the twist imparted to the ambient coronal field in Fig. 2(c)continues to propagate outward. Here, the yellow circles represent the Sun, and the blue lines represent heliospheric field linesthat are curved with respect to a radial line (black), following a Parker spiral. In (a), the wave imparted to the coronal fieldin Fig. 2(c) becomes the red disturbance, that appears as a low-pitch twist wave packet moving outward (the radial extent ofthe twist packet would be comparable to a solar radius, and so its extent is exaggerated by a factor of a few times comparedto the Sun in this schematic representation). Panel (b) shows how the pitch of the disturbance is expected to increase as itmoves further from the Sun, into a regime with lower Alfv´en speed compared to that in the corona, as described in the text.In (c), this pitch-angle steepening of the disturbance continues as it moves even further from the Sun, perhaps appearing as a“switchback” by the time it encounters PSP. (a) AIA 304: 30-Jun-2012 20:51:44 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) (b) AIA 304: 30-Jun-2012 20:52:20 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) (c) AIA 304: 30-Jun-2012 20:54:08 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) (d) HMI: 30-Jun-2012 15:00:41 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) (e) HMI: 30-Jun-2012 20:51:41 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) (f) HMI: 30-Jun-2012 23:54:41 UT -300 -280 -260 -240 -220 -200 -180 -160X (arcsecs)200220240260280300320340 Y ( a r cs e cs ) Figure 4.
Coronal jets from NOAA AR 11513 (studied in detail in Sterling et al. 2016). Panels (a—c) show
SDO /AIA304 ˚A subframes, showing jet J5 of table 1. Arrows show absorbing erupting-filament material undergoing spinning motion inthe successive frames. Panel (a) is overlaid with the magnetogram of (e), where blue and green contours respectively outlinepositive and negative polarities. Panels (d—f) show
SDO /HMI magnetograms of the region, with white and black respectivelyrepresenting positive and negative polarities. Arrows in (d) show two neutral lines that are the source locations of the jets intable 1; the positive-polarity patch between the arrows decreases with time due to flux cancelation. According to the model inFig. 1, this flux cancelation builds the minifilament flux ropes that erupt to drive the jets, as in (a—c). Accompanying videosvid4abc and vid4def respectively show time evolution of the 304 ˚A images and HMI magnetograms. !" *’+,$*-.$*/$*’+$*0$ Figure 5.
Outer-coronal and inner-heliospheric manifestations of coronal jets from AR 11513. These are coronagraph imagesfrom
STEREO -B COR1 (a and c) and COR2 (b, d, e), and a
STEREO -B Hi1 heliospheric imager image (f). Horizontal pairsof images (a)-(b), (c)-(d), and (e)-(f), are respectively at approximately the same times. Sterling et al. (2016) identified thewhite-light jet in (a) as being due to coronal jets J4 and J5 of table 1 (jets 6 and 7 of Sterling et al. 2016), and the white-lightin (c) as due to coronal jet J6 of table 1 (jet 8 of Sterling et al. 2016). Panels (b) and (d) show that these white-light jetsremain intact (blue arrows) in the COR2 FOV (2.5—15 R ⊙ ), and (f) shows that the white-light jet in (d) persists into the Hi1FOV (15—84 R ⊙⊙