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Arcades of flare loops rise, slowing down in the wake of eruptive prominences. They lag significantly from the top of prominences and do not reach too great heights in the corona. It is widely accepted that their evolution is governed by the limited reconnection rate in the current sheet developed below the eruptive prominence. We suggest that the shape of eruptive prominences may be the determining factor in the ascension of the arcade. Arcade deceleration and their limited heights are analysed in the frame of a simple rectangular circuit model representing prominence eruption. A null point that appears below the rising electric current does not follow it to a great height but is detained by the influence of the field created by currents flowing along the vertical segments,‘legs’, of the rectangular contour. As a result, the flare loops are able to reach only limited heights even with fast reconnection in a small current sheet.

Bombus glacialis Friese, 1902 is an Arctic bumblebee that was thought to have a disjunctive range on the Arctic Ocean Islands, i.e., on Novaya Zemlya and Wrangel Island, with a 3600 km gap between these isolates. While the species status of the Novaya Zemlya’s population was recently confirmed using a molecular approach, its close affinities to the Wrangel’s isolate were proposed by a morphological similarity alone. Here, we report that B. glacialis samples from Wrangel share three unique COI haplotypes, which are closely related to each other and to those inferred from samples from Novaya Zemlya. Based on a combination of diagnostic morphological and molecular characters, the Wrangel’s population is described here as a new subspecies, Bombus glacialis marinae ssp. nov. Our novel data indicate that this species can be considered a polar relict that had had a much broader distribution along the continental margin of Eurasia during the Pleistocene. The two subspecies of B. glacialis were likely separated in the Middle Pleistocene (mean age = 0.27 Myr, 95% CI = 0.12–0.46 Myr) due to increasing of the sea level during an interglacial. The Novaya Zemlya Archipelago supported a B. glacialis population in the Late Pleistocene. Hence, this insular land was not covered completely by ice sheet during the Last Glacial Maximum. Our findings highlight that relict cold-adapted Pleistocene lineages still survive on remote islands in the Arctic Ocean and that such lineages are highly threatened by recent climate warming.

Model of a partial current-carrying torus loop anchored to the photosphere is analyzed. Conditions of the catastrophic loss of equilibrium are considered and corresponding value of the critical decay index of external magnetic field is found. Taking into account line-tying conditions leads to non-monotonous dependence of the critical decay index on the height of the apex and length of the flux rope (its endpoints separation). For relatively short flux ropes, the critical decay index is significantly lower than unity, which is in contrast to widespread models with the typical critical decay index above unity. The steep decrease of the critical index with height at low heights is due to the sharp increase of the curvature of the flux-rope axis that transforms from a nearly straight line to a crescent., Comment: 11 pages, 4 figures. Accepted for publication in MNRAS

International audience; Eclipse observations of the W-L corona show linear rays above active regions at times of solar maximum. We show that these linear rays are also observed in the field-of-view of the C2-LASCO coronagraph, in perfect correspondence with the eclipse results. A selected prominent case taken from the 2001 eclipse observation in Angola is analysed with several different methods, including the use of a synoptic map constructed using SoHO/LASCO C2 images. A clear signature of time variations near the eclipse observation is detected, suggesting that at least some parts of the beam are collimated. These observations strongly suggest high speed streams that apparently ignore the potential large scale coronal magnetic field rooted rather low in the corona. A possible origin is the neutral magnetic points located above the active region. Several mechanisms exist to explain how the plasma is accelerated in these regions to large quasi-relativistic velocities, possibly related to the occurrence of type III radio bursts. We point out a curious analogy with phenomena occurring inside coronal holes.

Supplementary Materials: Table S1. List of sequenced specimens of Pterostichus brevicornis and Pterostichus nivalis, including the location wiht BOLD and NCBI’s GenBank accession numbers Table S2. Sampling sites and sample size: total number of pronotum (males and females) and male genitalia (aedeagus). Table S3. Contribution of significant principal components to shape variation of pronotum and aedeagus Pictures &nbsp

Total solar eclipse (TSE) coronal large and small scale events were reported in the historical literature but a definite synoptic coverage was missing for studying a relationship with the more general magnetic context of the solar-disk. We here analyze temporal changes in the solar corona before, during, and after the total solar eclipse on 21 August 2017 from a set of ground-based and of space-borne observations. High-quality ground-based white-light (W-L) observations and a deep image processing allow us to reveal these changes for the first time with a fraction of a one-minute time resolution. Displacements of a number of fine coronal features were measured for the first time at these small radial distances, using a diffraction limited instrument at a single site. The comparison with space-based observations, including observations from the {\it Solar Terrestrial Relations Observatory} (STEREO) mission, showed that the features belong to a slow coronal mass ejection (CME) propagating through the corona with the nearly constant speed of 250 km/s. Our TSE images provide the same typical velocity as measured at a distance of one solar radius from the surface. The event was initiated by coronal dynamics manifested by a prominence eruption that started just before the eclipse observations and an ascent of a U-shaped structure visible in the AIA 171 A channel, which we assume as the lower part of a coronal cavity. The prominence material was observed draining down towards the chromosphere along the prominence arch. While the prominence disappears in the STEREO-A field-of-view at the height of about 6$^{\prime}$ above the limb, the corresponding flux rope seems to continue towards the outer corona and produces the slow CME with turbulent motion. The overall mass of the moving features is evaluated based on absolute photometrical data extracted from our best W-L eclipse image., Comment: 25 pages, 11 figures, the paper has been accepted for publication in Solar Phys

We analyze 16 failed filament eruptions observed near 24 solar cycle maximum from May 2013 to July 2014. No significant rotation of filament spines is observed during the ascent in all studied failed eruptions, which does not support kink-instability mechanism of triggering the eruptions. We calculate potential magnetic field distributions in the corona above the initial locations of the filaments to study their height dependence. In seven events, the vertical profiles of the decay index $n$ are monotonic. The other nine events occur in the regions with the switchback or saddle-like n-profiles. The direction of the horizontal field near the saddle bottom is turned through more than 100$^\circ$ relative its direction at the initial filament position, which reveals the quadrupolar magnetic configuration with null points in these regions. The eruptive filaments stop above the null points where the total Lorenz force is directed upward. The most reasonable force that can terminate filament ascending and balance the Lorenz force seems the gravity., Comment: 13 pages, 12 figures, accepted for publication in MNRAS

Origins of the fauna in Iceland is controversial, although the majority of modern research supports the postglacial colonization of this island by terrestrial invertebrates rather than their long-term survival in glacial refugia. In this study, we use three bumblebee species as a model to test the hypothesis regarding possible cryptic refugia in Iceland and to evaluate a putative origin of recently introduced taxa.Bombusjonellusis thought to be a possible native Icelandic lineage, whereasB.lucorumandB.hortorumwere evidently introduced in the second half of the 20thcentury. These phylogeographic analyses reveal that the IcelandicBombusjonellusshares two COI lineages, one of which also occurs in populations on the British Isles and in mainland Europe, but a second lineage (BJ-02) has not been recorded anywhere. These results indicate that this species may have colonized Iceland two times and that the lineage BJ-02 may reflect a more ancient Late Pleistocene or Early Holocene founder event (e.g., from the British Isles). The Icelandic populations of bothBombuslucorumandB.hortorumshare the COI lineages that were recorded as widespread throughout Eurasia, from the European countries across Russia to China and Japan. The findings presented here highlight that the bumblebee fauna of Iceland comprises mainly widespread ubiquitous lineages that arrived via natural or human-mediated dispersal events from the British Isles or the mainland.

We analyzed a small flux rope eruption converted into a helical blowout jet in a fan-spine configuration using multi-wavelength observations taken by SDO, which occurred near the limb on 2016 January 9. In our study, first, we estimated the fan-spine magnetic configuration with the potential field calculation and found a sinistral small filament inside it. The filament along with the flux rope erupted upward and interacted with the surrounding fan- spine magnetic configuration, where the flux rope breaks in the middle section. We observed compact brightening, flare ribbons and post-flare loops underneath the erupting filament. The northern section of the flux rope reconnected with the surrounding positive polarity, while the southern section straightened. Next, we observed the untwisting motion of the southern leg, which was transformed into a rotating helical blowout jet. The sign of the helicity of the mini-filament matches the one of the rotating jet. This is consistent with the jet models presented by Adams et al. (2014) and Sterling et al. (2015). We focused on the fine thread structure of the rotating jet and traced three blobs with the speed of 60-120 km/s, while the radial speed of the jet is approx 400 km/s. The untwisting motion of the jet accelerated plasma upward along the collimated outer spine field lines, and it finally evolved into a narrow coronal mass ejection at the height of approx 9 Rsun . On the basis of the detailed analysis, we discussed clear evidence of the scenario of the breaking of the flux rope and the formation of the helical blowout jet in the fan-spine magnetic configuration., Comment: 18 pages, 12 figures, Accepted for publication in MNRAS Jouranl

Coronal mass ejections (CMEs) are closely related to eruptive filaments and usually are the continuation of the same eruptive process into the upper corona. There are failed filament eruptions when a filament decelerates and stops at some greater height in the corona. Sometimes the filament after several hours starts to rise again and develops into the successful eruption with a CME formation. We propose a simple model for the interpretation of such two-step eruptions in terms of equilibrium of a flux rope in a two-scale ambient magnetic field. The eruption is caused by a slow decrease of the holding magnetic field. The presence of two critical heights for the initiation of the flux-rope vertical instability allows the flux rope to stay after the first jump some time in a metastable equilibrium near the second critical height. If the decrease of the ambient field continues, the next eruption step follows., 8 pages, 5 figures, accepted for publication in MNRAS

Freshwater mussels (Unionida) are one of the most imperiled animal groups worldwide, revealing the fastest rates of extinction. Habitat degradation, river pollution and climate change are the primary causes of global decline. However, biological threats for freshwater mussels are still poorly known. Here, we describe a diverse ecological group of leeches (Hirudinea: Glossiphoniidae) inhabiting the mantle cavity of freshwater mussels. So far, examples of mussel-associated leech species are recorded from East Asia, Southeast Asia, India and Nepal, Africa, and North America. This group comprises a dozen glossiphoniid species with a hidden life style inside the mantle cavity of their hosts largely overlooked by researchers. We show that the association with freshwater mussels evolved independently in three leech clades, i.e. Batracobdelloides, Hemiclepsis, and Placobdella, at least since the Miocene. Seven mussel-associated leech species and two additional free-living taxa are described here as new to science.

The High Arctic bumble bee fauna is rather poorly known, while a growing body of recent molecular research indicates that several Arctic species may represent endemic lineages with restricted ranges. Such local endemics are in need of special conservation efforts because of the increasing anthropogenic pressure and climate changes. Here, we re-examine the taxonomic and biogeographic affinities of bumble bees from Novaya Zemlya using historical samples and recently collected materials (1895–1925vs.2015–2017). Three bumble bee species inhabit the Yuzhny (Southern) Island and the southern edge of Severny (Northern) Island of this archipelago:BombusglacialisFriese, 1902,B.hyperboreusSchönherr, 1809, andB.pyrrhopygusFriese, 1902.Bombusglacialisshares three unique COI haplotypes that may indicate its long-term (pre-glacial) persistence on Novaya Zemlya. In contrast,BombushyperboreusandB.pyrrhopygusshare a rather low molecular divergence from mainland populations, with the same or closely related haplotypes as those from Arctic Siberia and Norway. A brief re-description ofBombuspyrrhopygusbased on the newly collected topotypes is presented. Habitats, foraging plants and life cycles of bumble bees on Novaya Zemlya are characterized, and possible causes of extremely low bumble bee abundance on the archipelago are discussed. The species-poor bumble bee fauna of Novaya Zemlya is compared with those in other areas throughout the Arctic. The mean bumble bee species richness on the Arctic Ocean islands is three times lower than that in the mainland Arctic areas (3.1vs.8.6 species per local fauna, respectively). General linear models (GLMs) indicate that this difference can be explained by specific environmental conditions of insular areas. Our findings highlight that the insularity is a significant factor sharply decreasing species richness in bumble bee assemblages on the Arctic Ocean archipelagoes through colder climate (lower summer temperatures), prevalence of harsh Arctic tundra landscapes with poor foraging resources, and in isolation from the mainland.

A large filament composed principally of two sections erupted sequentially in the southern hemisphere on January 26 2016. The central, thick part of the northern section was first lifted up and lead to the eruption of the full filament. This event was observed in H-alpha with GONG and CLIMSO, and in ultraviolet (UV) with the AIA/SDO imager. The aim of the paper is to relate the photospheric motions below the filament and its environment to the eruption of the filament. An analysis of the photospheric motions using SDO/HMI continuum images with the coherent structure tracking (CST) algorithm developed to track granules, as well as large-scale photospheric flows, has been performed. The supergranule pattern is clearly visible outside the filament channel but difficult to detect inside because the modulus of the vector velocity is reduced in the filament channel, mainly in the magnetized areas. The horizontal photospheric flows are strong on the west side of the filament channel and oriented towards the filament. The ends of the filament sections are found in areas of concentration of corks. Whirled flows are found locally around the feet. The strong horizontal flows with an opposite direction to the differential rotation create strong shear and convergence along the magnetic polarity inversion line (PIL) in the filament channel. The filament has been destabilized by the converging flows, which initiate an ascent of the middle section of the filament until the filament reaches the critical height of the torus instability inducing, consequently, the eruption. The "n" decay index indicated an altitude of 60 Mm for the critical height. It is conjectured that the convergence along the PIL is due to the large-scale size cells of convection that transport the magnetic field to their borders., 10 pages, 9 figures

We analyse observations of a saddle-like structure in the corona above the western limb of the Sun on 2017 July 18. The structure was clearly outlined by coronal loops with typical coronal temperature no more than 1 MK. The dynamics of loops showed convergence toward the centre of the saddle in the vertical direction and divergence in the horizontal direction. The event is a clear example of smooth coronal magnetic field reconnection. No heating manifestations in the reconnection region or magnetically connected areas were observed. Potential magnetic field calculations, which use as the boundary condition the SDO/HMI magnetogram taken on July 14, showed the presence of a null point at the height of 122" above the photosphere just at the centre of the saddle structure. The shape of field lines fits the fan-spine magnetic configuration above NOAA 2666., 11 pages, 9 figures, accepted for publication in PASA

We analyze multi-wavelength and multi-viewpoint observations of a helically twisted plasma jet formed during a confined filament eruption on 10-11 April 2013. Given a rather large scale event with its high spatial and temporal resolution observations, it allows us to clearly understand some new physical details about the formation and triggering mechanism of twisting jet. We identify a pre-existing flux rope associated with a sinistral filament, which was observed several days before the event. The confined eruption of the filament within a null point topology, also known as an Eiffel tower (or inverted-Y) magnetic field configuration results in the formation of a twisted jet after the magnetic reconnection near a null point. The sign of helicity in the jet is found to be the same as that of the sign of helicity in the filament. Untwisting motion of the reconnected magnetic field lines gives rise to the accelerating plasma along the jet axis. The event clearly shows the twist injection from the pre-eruptive magnetic field to the jet.

The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fill the whole volume of a dark coronal cavity. The flux ropes can be in stable equilibrium in the coronal magnetic field for weeks and even months, but suddenly they loose their stability and erupt with high speed. Their transition to the unstable phase depends on the parameters of the flux rope (i.e., total electric current, twist, mass loading etc.), as well as on the properties of the ambient coronal magnetic field. One of the major governing factors is the vertical gradient of the coronal magnetic field which is estimated as decay index (n). Cold dense prominence material can be collected in the lower parts of the helical flux tubes. Filaments are therefore good tracers of the flux ropes in the corona, which become visible long before the beginning of the eruption. The perspectives of the filament eruptions and following CMEs can be estimated by the comparison of observed filament heights with calculated decay index distributions. The present paper reviews the formation of magnetic flux ropes, their stable and unstable phases, eruption conditions, and also discusses their physical implications in the solar corona., 27 pages, 14 figures; to appear in Journal of Astrophysics & Astronomy (Special Issue; Eds: V. Fedun, A.K. Srivastava, R. Erdelyi, J.C. Pandey)

Invertebrate herbivores, insects in particular, play important functional roles in terrestrial ecosystems. At background (non-outbreak) densities, they consume 5–15 % of woody plant foliage in forests across the planet. At the same time, almost nothing is known about the levels of insect herbivory in Arctic tundra. To test the hypothesis that the amount of plant biomass lost to insects in tundra is substantially less than in subarctic forests, in 2013, we explored foliar herbivory in woody plants at three sites in the Arctic tundra and four sites in the subarctic forests of European Russia. A vast majority of foliar damage was imposed by externally feeding defoliators. In forests, defoliators damaged three times more leaves and consumed eight times more leaf area than in the tundra. No miners were found in the tundra, and gallers affected five times less leaf area in the tundra compared with forests. An abrupt decrease in loss of woody plant foliage to insects between subarctic forests and tundra (from 4.34 to 0.56 %) supports the existence of a latitudinal gradient in herbivory in terrestrial ecosystems. More studies are needed to predict how tundra plants, which have been historically exposed to low levels of insect herbivory, will cope with the increased levels of damage that are expected to occur due to climate-driven range expansion and increased abundances of plant-feeding insects.

The notions of «religious awakening» and «religious revival» refer to processes which took place in the history of European civilization. These notions are widely used in academic language and literature. During the last third of the twentieth and the beginning of the twenty-first century, a global phenomenon emerged which can be described as «de-secularization», «religious revival» or «spiritual awakening». This was characteristic of all religions. Sociologists, researchers of religions and political scientists have begun to discuss its nature and character. The author attempts to place it in the broader context of Western European and Russian history of the last five hundred years. He wishes to examine it with reference to the cyclic-wave theory of social development. He introduces the concept of «religious tension» defined as the idea that mankind and the individual cannot be in a state of constant religious tension. Following the wave of spiritual tension or religious revival a «return wave» of spiritual indifference or tranquility succeeds. The two periods taken together constitute a single cycle. As a criterion for assessing the presence or absence of tension, the author highlights popular piety and the religious atmosphere just before the Protestant Reformation. These models are later employed as part of a pattern underlining similar characteristics of religious life at other times. The first section of the article presents the theory behind the problem and the characteristics of the return wave lasting from 1930 to 1960. This was the wave that served as the basis for the theory of secularization. The second section of the article highlights the religious tension characteristic of the second half of the twentieth and the start of the twenty-fi rst century.

The polar tiger moth Pararctia subnebulosa (Dyar 1899) (Erebidae: Arctiinae) is one of the few conspicuous and largest Lepidoptera species in the High Arctic. However, the biology and distribution patterns of this remarkable species have not been sufficiently studied. In the present note, we summarize known data for the species localities, provide DNA barcode data and describe the immature stages and a gregarious parasitoid. The species was collected from Kolguev Island, Arctic European Russia, for the first time. This locality is situated 500 km westward from a previously known species recording in the Yugor Peninsula, which substantiates that P. subnebulosa is also a member of the European fauna. DNA barcode data revealed that the Kolguev specimen shares a close haplotype with those from Chukotka at distance ca. 5,000 km. However, a specimen from Canada has a highly divergent haplotype that indicates that the Russian populations are a separate cryptic species, P. tundrana Tshistjakov 1990. We provide the first data for an assessment of the role of Meteorus parasitoid pressure on the imago abundance of P. subnebulosa. Among 87 moth larvae collected from the Yugor Peninsula, only eight larvae (9.2 %) developed into imagoes, and all of the others (79 ind., 90.8 %) were lost due to parasitoid invasion. DNA barcode data show that this parasitoid is a sister to Meteorus acerbiavorus (Braconidae, Euphorinae). Our findings highlight the existence of multiple cryptic refugia in Beringia and an important role of parasitoids in the suppression of Arctic Lepidoptera populations.

We present here an interesting two-step filament eruption during 14-15 March 2015. The filament was located in NOAA AR 12297 and associated with a halo Coronal Mass Ejection (CME). We use observations from the Atmospheric Imaging Assembly (AIA) and Heliospheric Magnetic Imager (HMI) instruments onboard the Solar Dynamics Observatory (SDO), and from the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO). We also use H-alpha data from the Global Oscillation Network Group (GONG) telescope and the Kanzelhoehe Solar Observatory. The filament shows a first step eruption on 14 March 2015 and it stops its rise at a projected altitude ~ 125 Mm on the solar disk. It remains at this height for ~ 12 hrs. Finally it eruptes on 15 March 2015 and produced a halo CME. We also find jet activity in the active region during both days, which could help the filament de-stabilization and eruption. The decay index is calculated to understand this two-step eruption. The eruption could be due to the presence of successive instability-stability-instability zones as the filament is rising., 11 pages, 7 figures, accepted for the publication in Solar Physics

Interest to lateral details of the solar filament shape named barbs, motivated by their relationship to filament chirality and helicity, showed their different orientation relative to the expected direction of the magnetic field. While the majority of barbs are stretched along the field, some barbs seem to be transversal to it and are referred to as anomalous barbs. We analyse the deformation of helical field lines by a small parasitic polarity using a simple flux rope model with a force-free field. A rather small and distant source of parasitic polarity stretches the bottom parts of the helical lines in its direction creating a lateral extension of dips below the flux-rope axis. They can be considered as normal barbs of the filament. A stronger and closer source of parasitic polarity makes the flux-rope field lines to be convex below its axis and creates narrow and deep dips near its position. As a result, the narrow structure, with thin threads across it, is formed whose axis is nearly perpendicular to the field. The structure resembles an anomalous barb. Hence, the presence of anomalous barbs does not contradict the flux-rope structure of a filament.

The existence of coronal plasmoids has been postulated for many years in order to supply material to streamers and possibly to the solar wind (SW). The W-L SoHO C2 Lasco coronagraph observations were made under the 2.2 solar radii (R0) occulting disk to look at the ultimate sources of the SW; EUV imagers are preferably devoted to the analysis of the corona on and very near the solar disk. Here, in addition to eclipse white-light (W-L) snapshots, we used the new SWAP space-borne imager designed for the systematic survey of coronal activity in the EUV lines near 17.4 nm, over a field of view (FOV) up to 2 R0. Using summed and co-aligned images, the corona can then be evaluated for the 1st time up to the limit of this FOV. At the time of the July 11, 2010, solar total eclipse a 20h continuous run of observations was collected, including images taken during eclipse totality from several ground observing locations where W-L data were collected. A plasmoid-like off-limb event was followed using the SWAP summed

Observations of jet- like phenomena near the solar limb are reported for a long time, first in H α (Secchi observations of spicules in the 1870 ies), and after, from eclipse high resolution coronal images taken in white-light (1920–1973) as spiky structures. EUV jets were reported in the 70 ies from rocket and space-borne CIV filtergrams and finally X-EUV jets were reported from SXT observations of Yohkoh and from EIT and CDS SoHO observations. There is now little doubt that they are of magnetic origin although no magnetic field measurements exist for these regions and thermo-dynamical models are still work out. New observations of both spicules and jets with the SOT/SXT of Hinode were subjected to an analysis showing the influence of the null point(s) of the magnetic field. The collective behavior of the H CaII SOT(Hinode) time sequences of processed with the Madmax operator images of limb spicules show the torsional effects which were partly suggested before from the interpretation of high resolution limb spectra taken on Russian coronagraphs and the VTT at SacPeak. 100 s and shorter period waves are recorded. We propose a reconnection process occurring at the top of an emerging twisted flux tube for explaining some peculiarities of the spicular eruptions and possibly, as a viable mechanism for explaining the SXR jet eruptions. The result of a numerical 3D modeling illustrates this erupting mechanism although the behavior of the magneto-plasma structure near a null point, as shown by coronal filtergrams, does not necessary imply reconnections, especially the case of jets making a long coronal ray we observed in white-light with Lasco C2.

We present the multiwavelength observations of a flux rope that was trying to erupt from NOAA AR 11045 and the associated M-class solar flare on 12 February 2010 using space-based and ground-based observations from TRACE, STEREO, SOHO/MDI, Hinode/XRT, and BBSO. While the flux rope was rising from the active region, an M1.1/2F class flare was triggered near one of its footpoints. We suggest that the flare triggering was due to the reconnection of a rising flux rope with the surrounding low-lying magnetic loops. The flux rope reached a projected height of ≈0.15R ⊙ with a speed of ≈90 km s−1 while the soft X-ray flux enhanced gradually during its rise. The flux rope was suppressed by an overlying field, and the filled plasma moved towards the negative polarity field to the west of its activation site. We found the first observational evidence of the initial suppression of a flux rope due to a remnant filament visible both at chromospheric and coronal temperatures that evolved a couple of days earlier at the same location in the active region. SOHO/MDI magnetograms show the emergence of a bipole ≈12 h prior to the flare initiation. The emerged negative polarity moved towards the flux rope activation site, and flare triggering near the photospheric polarity inversion line (PIL) took place. The motion of the negative polarity region towards the PIL helped in the build-up of magnetic energy at the flare and flux rope activation site. This study provides unique observational evidence of a rising flux rope that failed to erupt due to a remnant filament and overlying magnetic field, as well as associated triggering of an M-class flare.

Short-lived plasma jets of various scales, from giant X-ray jets more than 300 Mm in extent to numerous small jets with sizes typical of macrospicules, are the phenomena observed in the solar corona in extreme ultraviolet and X-ray emission. Small jets are particularly prominent in polar coronal holes. They are close neighbors of tiny bright loops and coincide in time with their sudden brightening and increase in size. The geometric shape of the jets and their location suggest that they arise near singular null points of the coronal magnetic field. These points appear in coronal holes due to the emergence of small bipolar or unipolar magnetic structures within large-scale unipolar cells. Polar jets show a distinct vertical plasma motion in a coronal hole that introduces significant momentum and mass into the solar wind flow. Investigating the dynamics of polar jets can elucidate certain details in the problem of fast solar wind acceleration.

New XRT observations of the north polar region taken from the X-ray Telescope (XRT) of the Hinode (Solar-B) spacecraft are used to analyze several time sequences showing small loop brightenings with a long ray above. We focus on the recorded transverse displacement of the jet and discuss scenarios to explain the main features of the events: the relationship with the expected surface magnetism, the rapid and sudden radial motion, and possibly the heating, based on the assumption that the jet occurs above a null point of the coronal magnetic field. We conclude that 3-D reconnection models are needed to explain the observational details of these events., Comment: 11 pages 8 figures

The onset of a coronal mass ejection (CME) is not preceded by any specific form of activity that could be recognized several days before the event. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fills the whole volume of the dark cavity stretched in the corona along the photospheric polarity inversion line. Cold dense prominence matter accumulates in the lower parts of helical flux tubes, which serve as magnetic traps in the gravitation field. So, prominences and filaments are the best tracers of the flux ropes in the corona long before the beginning of eruption. A twisted flux rope is held by the tension of field lines of photospheric sources until parameters of the system reach critical values and catastrophe happens. The flux rope height above the photosphere is one of these parameters and it is revealed by the height of the filament. We had analyzed some 80 of filaments and found that eruptive prominences were near the limit of stability a few days before eruptions. We believe that a comparison of the real heights of prominences with the calculated critical heights could be helpful for revealing the filaments that are prone to erupt.