{'fraction_non_alphanumeric': 0.029539394573116537, 'fraction_numerical': 0.02901657343022952, 'mean_word_length': 4.545955349376631, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Polar Coronal Plumes as Tornado-Like Jets

We examine the dynamical behavior of white light polar plume structures in the inner corona that are observed from the ground during total solar eclipses, based on their EUV hot and cool emission line counterparts observed from space. EUV observations from SDO/AIA of a sequence of rapidly varying coronal hole structures are analyzed. Evidence of events showing acceleration in the 1.25 Mk line of Fe XII at 193 A is given. The structures along the plume show an outward velocity of about 140 kms-1 that can be interpreted as an upwards propagating wave in the 304 A and 171 A lines; higher speeds are seen in 193 A (up to 1000 km/s). The ejection of the cold He II plasma is delayed by about 4 min in the lowest layer and more than 12 min in the highest level compared to the hot 193 A behavior. A study of the dynamics using time-slice diagrams reveals that a large amount of fast ejected material originates from below the plume, at the footpoints. The release of plasma material appears to come from a cylinder with quasi-parallel edge-enhanced walls. After the initial phase of a longitudinal acceleration, the speed substantially reduces and the ejecta disperse into the environment. Finally, the detailed temporal and spatial relationships between the cool and hot components were studied with simultaneous multi-wavelength observations, using more AIA data. The outward-propagating perturbation of the presumably magnetic walls of polar plumes supports the suggestion that Alfven waves propagate outwardly along these radially extended walls.

Genuine polar plumes are linear, rather straight structures seen in the EUV line at 171 A up to 1.3RQ and in white-light during eclipses to much larger distances (see Figure 1 for a convincing correspondence). They should not be confused with the edge of streamer sheets seen in projection above the polar limbs (Bravo & Stewart 1996). In Figure 1 we illustrate the correlation between the classical white-light plumes from eclipse observations and the plumes seen in the excellent 171 A AIA/SDO filtergrams after using a summing of 80 consecutive images with cadence of 12 sec. Outwardly propagating fast features are visible in hot coronal lines along the plumes as illustrated in Figure 1, EUV 171 A structures with W-L structures making the ray-like features in the polar region and usually called polar plumes or polar jets. Further, we looked at the relationship with He II 304 macrospicules and polar erupting small prominence structures, as was suggested from simultaneous ground based observation performed at the feet of the plume in the cool Ha line (Georgakilas et al. 2001). Macrospicules were broadly defined in He II 304 A observations as long, usually pointed jets ranging in length from 5 to over 50 arcsec (Bohlin et al. 1975).
The ions in high-speed solar wind accelerate to terminal speeds of about 800 kms -1 above the CH (Wilhelm et al. 2000(Wilhelm et al. , 2011. This rapid acceleration cannot be explained by hydrodynamic forces (plasma gas pressure) alone. Some other form of momentum transfer, such as forces appearing in the region due to self-excited dynamo must be at work (Lorrain et al. 2006), or other mechanisms, such as Alfven-cyclotron resonance (Kasper et al. 2008). Coronal plumes, together with other dynamic structures in the solar atmosphere, such as macrospicules and X-ray jets, are potential sources of solar wind (spicules provide 100 times more mass than what is needed to fill the corona Pneuman and Kopp (1978)) and moreover, recent studies indicate that plumes are a plausible source of the fast solar wind streams (Gabriel et al. 1994(Gabriel et al. , 2009). Other investigations led to different results (e.g. Wang et al. 1998;Habbal et al. 1995;Wilhelm et al. 2000). Wang et al. (1998) reported speeds of 400-1100 kms -1 for the outermost part of the W-L jets, whereas their centroidal velocities for the bulk of material are much lower. The contribution of polar plumes to the fast solar wind rising from the polar CH is thus still a subject of debate and controversy (e.g. Habbal 1992; Gabriel et al. 2003). More details about plumes and inter-plume regions were listed in the review of Wilhelm et al. (2011) andof Poletto (2015).
Del Zanna et al. (2003) found that bright points are seen near the plume footpoints only in the early phase of their formation. Wilhelm et al. (2010) found a strong association of plumes and jets from XRT/Hinode images and Raouafi et al. (2008) showed that X-ray jets are precursors of coronal plume formation. Studies of morphology, kinematics, dynamics and the production AASTEX POLAR CORONAL PLUMES AS TORNADO-LIKE JETS 3 mechanism of a rather small-scale tornado have been recently pursued (Wedemeyer-Bohm et al. 2012) at photospheric granulation scale. The evolution as a function of height towards the corona of this type of event is still unknown. Kitiashvili et al. (2013) provided a realistic numerical simulation showing that the small jets due to the vortex at the foot of a plume could capture and stretch the background magnetic field, generate shocks and push plasma to the upper atmosphere. The magnetic field captured in the vortex causes an initial perturbation and accelerates the plasma along the helical medium to produce a spontaneous-seeming ejection in the solar atmosphere (Lorrain et al. 2006). A great number of observations and studies show that tornado-type eruptions (including surges) are composed of fine, long threads (Tavabi et al. 2015b;Chen et al. 2012). The AIA observations of polar CHs suggest that the region may be finely structured at arcsec scales in width with multiple threads of both hot and cool dynamical tornados.

EUV Jets
X-ray jets were discovered with the X-ray telescope onboard the Japanese Yohkoh mission (Yokoyama and Shibata 1995;Shibata et al. 1992). They are associated with small flares and occur above X-ray bright points (Golub et al. 1974). Moore et al. (1976Moore et al. ( , 1977 also showed that X-ray bright points could be associated with Ha macrospicules. Shibata et al. (1992) and Canfield et al. (1996) have reported that X-ray jets are observed to be associated with cool ejections or plasmoids, nearly simultaneously and in nearly the same direction. There have been numerous studies predicting that twisting motions should be present in eruptive structures in the low corona. Radially-directed linear structures seen above the limb exhibit fast ejections that reach peak velocities of 20-200 kms -1 (Tavabi et al. 2011(Tavabi et al. , 2015aDe Pontieu et al. 2014). At chromospheric heights they are called spicules, and usually they exhibit a rotational motion with several turns (Tavabi et al. 2013). However, the rotational behavior seems uncommon in X-ray jets (e.g. Filippov et al. 2009). Pariat et al. (2010 performed 3D MHD simulations of an instability taking place in a quasi-statically driven MHD system showing a jet; they found that torsional Alfven waves with upflowing helical motion are the result of reconnection of initially twisted loops with open fields. Canfield et al. (1996) suggests that the rotational motion is due to the redistribution of stored twist after reconnection with two loops having different numbers of 360° turns. Patsourakos et al. (2008) reported on observations made by the twin spacecraft STEREO A and B in the EUV (195 A and 171 A) of a helical jet. This jet twists and untwists above the limb in a polar coronal hole. Moore et al. (2015) studied several cases of hot EUV jets in 193 A line, with erupting loops that are also seen as bright emission in the relatively cool 304 A line with darker components (absorption) seen in the 193 A hotter line at the base of an eruptive tornadolike event, which is also seen in our study (see Figures 2 and 3). This schema suggests that the interacting loops at the reconnection X-null point are related to the rather cool chromospheric features and with the initial plasma ejection being due to mutual interactions of highly twisted cool loops. Tornado phenomena were occasionally reported with a turn number of more than 3 full 360° turns (Shen et al. 2011). The number of turns and consequent untwisting behavior should be taken into account when interpreting the energy release and the acceleration mechanism. Panesar et al. (2013) reported tornados as dynamical, conspicuously helical magnetic structures mainly observed as a prominence activity that the tornado was dynamically associated with the expansion of the prominences helical field and its cavity.

OBSERVATIONS
The Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO) (Pesnell et al. 2012) is an array of four telescopes that captures images of the Sun's atmosphere out to 1.3RQ in ten separate EUV and UV wave bands (Title et al. 2006). The images are 4096 x 4096 square with a pixel size of 0.6" in the full spatial resolution mode, with a cadence of 12 seconds on 10 July 2010 ( Figure 2) that are considered here. A full day sequence was prepared by Koutchmy et al. (2012) for the analysis of events observed at the time of the total solar eclipse of 2010, to increase the signal/noise ratio, and improve the visibility of images. The processing method is based on frame summing, radial filtering and unsharp masking. A solid line in Figure 4 indicates the position along which the jet was ejected. We confirm the association of plumes with smallscale explosions at their feet using a movie assembled from the AIA data (movie S1). Several examples of dynamical jets were found at the pole over a time interval of ~ 24H. They were seen at the base of much more extended plumes. To quantify these motions, we did three cuts along the axis of the selected jet, oriented roughly perpendicular to the axis as shown in Figure 4. It is difficult to measure the radial velocity of the bulk of the plasma within the jets but, given the large number of such events now being seen in the 171 A channel using running difference frames ( Figure 5), it seems that in 193 A hotter line the speed is large enough (table 1) for the plasma to escape and to significantly contribute to the fast solar wind; the typical velocity is about 800 km s -1 . Time-slice diagrams (Figure 6) of the cuts clearly show the dynamical behavior of the trapped ejected plasma inside the plume. 4 TAVABI, KOUTCHMY AND GOLUB.
Based on this diagram, we suggest that the early phase of the plasma ejection, after a phase of circular motion inside the plumes, is followed by an evaporation phase (ejection) along the plume after the plasma emerges into the corona in an open-field environment, similarly to that proposed by e.g. Wilhelm et al. (2011). An initial ascending radial velocity is shown by the green line of the time-distance diagram in Figure 7 (result for the 304 A line). It shows a typical value of 140 ± 10 kms -1 found for the ascending velocity. The rotational velocity is found of order of 0.02 rad/sec (145 ± 30 kms -1 ); the deduced period of rotation is near 5 min. This rotational velocity is deduced assuming a spiral motion of identified features along what looks like a cylindrical surface. The average outflow velocity is the same for the 171 A line and remains approximately constant during the ascent. Considering the velocity of the intensity front, we find for the 193 A line velocity of 720 ± 10 up to more than 1000 ± 10 kms -1 during the ascent, which is in significant contrast with the apparent velocities observed in the cool 304 A line (Figure 7). In order to investigate this possible scenario of a helical motion followed by evaporative ejection, we analyzed the behavior of the cool part of our 304 A jet in Figure 7 using the time-distance method. The most significant result is the evidence (see the right part of the diagram of Figure 7) of time-distance diagram following quasi-parabolic trajectories. Some returning flux is also seen although the innermost part of the phenomenon inhibits a definite ejection. We note that a similar result was obtained (Kayshap et al. 2013) for a polar event interpreted as a macrospicule and the associated jet, without considering the coronal counterparts. In this study, we present detailed observations of a CH jet, with a cool tornado-like structure at the feet and extended in the radial direction.

DISCUSSION
To reveal the importance of the mechanism causing tornado-like events, the events were simultaneously observed in a time sequence of data obtained at multiple wavelengths in order to understand their dynamical characteristics. The first important aspect of this observation is the occurrence of jets as plasma ejections related to polar plumes. Raouafi and Stenborg (2014) also reported several jetlets (small jets) at the feet of plumes (see also white light observations from eclipse images, Koutchmy & Stellmacher (1976)). Jets are highly dynamic and are seemingly one of the main energetic material source for plumes. It was also noted that jet ejection along the preexisting plumes increases the plume brightness. Wilhelm et al. (2011) show that polar jets in the interplume region propagate along the plumes seen in the Large Angle Spectroscopic Coronagraph (LASCO) instrument on SoHO (Brueckner et al. 1995) white-light images (Figure 8), and in eclipse white-light images near the solar minimum of activity. An extended analysis of the activity in the polar regions was made by Wang et al. (1998) using the EIT EUV filtergrams and the LASCO C2 images during the SoHO mission with a more limited spatio-temporal resolution compared to the present study. Note that these authors called the EUV eruptive phenomenon event producing a polar W-L dynamical structure a dynamical jet. In Figure 10 we show more details and improve the visibility of the dynamical parts, the original intensities of plumes in each image were subjected to a running subtraction using a background image obtained after summing 16 minutes of consecutive images with cadence of 12 sec which run over the whole time sequence, pixel by pixel. In order to reproduce physically meaningful intensities we added a threshold to the result of the subtraction in Figure 5.
In the temporal evolution from the 304 A images of the tornado, the main components (or kernels) of the event are launched from the base with a constant proper velocity having an average value of 140 ± 40 kms -1 (from the analysis of Figure 7), and a rotational velocity with a similar value, of 145 kms -1 in this cool line. This filtering process allows us to separate short-lived dynamic phenomena from rather longer life-time background plume intensity variations. The time-distance diagram along the axis of tornado (Figure 7) in 304 A line suggests that later the ejected plasma is flowing back to the Sun. This type of a suggested complete parabola motion path (e.g. Figure 7) is not seen in the 193 A line. The longitudinal motion observed in Figure 3 is confirmed by the enhancement appearing later (see Figure 8) above the same polar region and the same radial position, over the occulting disk of the C2 coronagraph of LASCO. Wang et al. (1998) already reported a large correlation between the Extreme-ultraviolet Imaging Telescope (EIT) jets and the long narrow white light structures in the outer corona recorded using the LASCO observations. A large maximum value of velocity, of order of 1100 km s -1 for the leading edge of the white-light jets (the outermost part of the jet that can be visually seen and distinguished) was found.
The two-threaded 171 A and 193 Al jets traveled at an apparent velocity of 140 km s -1 in Fe IX (171 Al) and up to 600 kms -1 to 1000 kms -1 in Fe XII (193 Al) images, with a median value of 720 kms -1 (Figure 10), 304 Al shows speed of 140 kms -1 , similar to what is observed for 171 Al (Figures 3 to 5). Such values in He II line are also reported from EIS observations by Kamio et al. (2010) for macrospicules seen associated to X-ray jets. 4. CONCLUSION In this study, we present detailed observations of a coronal hole jet, with a cool helical tornado-like structure at the feet and an extended hotter component in the radial direction. Our detailed analysis (Figures 9 to 11) shows that the propagation velocities are different for different line emissions and, accordingly, for different temperatures. In Figure 11 we show that at the highest level of the event the hot emissions occur first (also see Figure 10). This could suggest that the coronal heating is occurring first at higher levels where the densities are smaller. The foot region is presumably above a well-developed 10" size network element (rosette) of chromosphere. Recently Wedemeyer-Bohm et al. (2012) and Kitiashvili et al. (2013) considered an atmospheric tornado-like phenomenon as the result of a vortex magnetic structure driven by turbulence motions. It was also called a swirl with helical motion. Only a small scale (1 Mm) region was analyzed (Wedemeyer-Bohm et al. 2012;Kitiashvili et al. 2013), while here we deal with a region one order of magnitude larger. A simple model which permits a twisted magnetic field could imply a self-sustained ring current dynamo occurring in the high photosphere (Lorrain and Koutchmy 1996;Veselovsky et al. 1999) to enhance the magnetic field, as a result of converging horizontal motion. We propose that the main steps of tornado evolution consist of three phases (see Figures 3, 9 and 10): (1) a precursor heating phase where new magnetic flux emerges to the reconnection site with heating by current sheet at the X-null point made by interacting loops, (2) the impulsive phase that begins when the cool chromospheric loops start to rotate, and (3) the main phase, when the stored magnetic energy is released by ejection and untwisting.
The observation of a time difference between the hot linear jet-like feature and the ensuing tornado-like cool event suggests that the tornado helical formation is closely related to the precursor hot component that occurs when a release of energy occurs with the acceleration inside the tornado plasma vortex near the reconnection site. The SDO/AIA temporal and spatial resolution allows us to resolve some uncertainty concerning the relationship of hot line ejections and the cold tornado events at their footpoints. The detailed analysis of the behavior of different components of our event strongly supports the rather new suggestion that polar plumes (e.g. see Figure 1) are made of simple cylindrical structures of 10" to 25" diameter with an expansion in time, height and width. A more detailed comparison with the sub-structure and the behavior of eclipse white-light polar-plumes is needed (work in progress) to understand these structures. The forthcoming launch by ESA of a novel coronagraph system (PROBA3 mission) permitting a total solar eclipse in space for several hours (Lamy et al. 2008) is another opportunity for making progress on this very old and classical question of explaining magnetic solar coronal polar plumes.        Table 1 and future analyzed in Figure 11.