Search

Magnetohydrodynamic (MHD) waves are often invoked to interpret quasi-periodic pulsations (QPPs) in solar flares. We study the response of a straight flare loop to a kink-like velocity perturbation using three-dimensional MHD simulations and forward model the microwave emissions using the fast gyrosynchrotron code. Kink motions with two periodicities are simultaneously generated,with the long-period component P_L = 57s being attributed to the radial fundamental kink mode and the short-period component P_S=5.8s to the first leaky kink mode. Forward modeling results show that the two-periodic oscillations are detectable in the microwave intensities for some lines of sight. Increasing the beam size to (1")^2 does not wipe out the microwave oscillations. We propose that the first leaky kink mode is a promising candidate mechanism to account for short-period QPPs. Radio telescopes with high spatial resolutions can help distinguish between this new mechanism with such customary interpretations as sausage modes., Comment: Accepted for publication in ApJL

La historia cafetera y ganadera de esta zona se destacaba en el departamento hace unos años, en épocas de crisis la minería surgió y hoy es una de las principales razones de desarrollo económico en Amaga, la industria esta siendo apalancada por la vía que lo conecta con el Área metropolitana. The coffee and livestock history of this area stood out in the department a few years ago, in times of crisis, mining emerged and today it is one of the main reasons for economic development in Amaga, the industry is being leveraged by the road that connects it with the metropolitan area. Pregrado

Background: Pulmonary vein isolation (PVI) with multielectrode duty-cycled radiofrequency (PVAC) has been shown to be effective in the treatment of atrial fibrillation (AF). We describe pulmonary vein (PV) reconnection at repeat ablation in patients with AF recurrence after PVAC PVI and analyze the correlation between the time of AF recurrence and the observed PV reconnection patterns. Methods: Eighty-five patients undergoing a redo PVI for recurrent AF 9.2 ± 3.8 months after an initial PVAC PVI procedure was retrospectively enrolled. Results: A total of 93% had PV reconnections with a mean of 2.97 ± 1.2 reconnected PVs/patients and 75% of formerly isolated PVs were found reconnected. The highest reconnection rates (94%) were observed for left common trunks (CTs). A total of 33% patients had three and four reconnected PVs, respectively, while 7% were without PV reconnection. There was a moderate but significant negative correlation between the time of AF recurrences and the extending of PV reconnections at redo PVI for patients with proven PV reconnection (r = -0.32, P = 0.005), whereas five out of six patients without PV reconnection had recurrences within the first 9 months after PVI. Conclusions: At redo ablation most patients with recurrence of AF after PVAC PVI had PV reconnection(s). Patients with PV reconnection(s) showed a moderate negative correlation between the number of reconnected PVs and the time of AF recurrence with more extensive PV reconnections resulting in earlier PV recurrences after the blanking period. Patients without PV reconnection experienced early AF recurrences, indicating non-PV triggers contribute to AF recurrences in these patients. Cardiol Res. 2020;11(3):179-184 doi: https://doi.org/10.14740/cr1050

We performed high-resolution three-dimensional global MHD simulations to determine the impact of weak southward interplanetary magnetic field (IMF) (Bz = −2 nT) and slow solar wind to the Earth’s magnetosphere and ionosphere. We considered two cases of differing, uniform time resolution with the same grid spacing simulation to find any possible differences in the simulation results. The simulation results show that dayside magnetic reconnection and tail reconnection continuously occur even during the weak and steady southward IMF conditions. A plasmoid is generated on closed plasma sheet field lines. Vortices are formed in the inner side of the magnetopause due to the viscous-like interaction, which is strengthened by dayside magnetic reconnection. We estimated the dayside magnetic reconnection which occurred in relation to the electric field at the magnetopause and confirmed that the enhanced electric field is caused by the reconnection and the twisted structure of the electric field is due to the vortex. The simulation results of the magnetic field and the plasma properties show quasi-periodic variations with a period of 9–11 min between the appearances of vortices. Also the peak values of the cross-polar cap potential are both approximately 50 kV, the occurrence time of dayside reconnections are the same, and the polar cap potential patterns are the same in both cases. Thus, there are no significant differences in outcome between the two cases.

Most geomagnetic indices are associated with processes internal to the magnetosphere-ionosphere system: convection, magnetosphere-ionosphere current systems, particle pressure, ULF wave activity, etc. The saturation (or not) of various geomagnetic indices under various solar-wind driver functions (a.k.a. coupling functions) is explored by examining plots of the various indices as functions of the various driver functions. In comparing an index with a driver function, “saturation” of the index means that the trend of stronger geomagnetic activity with stronger driving weakens in going from mid-range driving to very strong driving. Issues explored are 1) whether the nature of the index matters (i.e., what the index measures and how the index measures it), 2) the relation of index saturation to cross-polar-cap potential saturation, and 3) the role of the choice of the solar-wind driver function. It is found that different geomagnetic indices exhibit different amounts of saturation. For example the SuperMAG auroral-electrojet indices SME, SML, and SMU saturate much less than do the auroral-electrojet indices AE, AL, and AU. Additionally it is found that different driver functions cause an index to show different degrees of saturation. Dividing a solar-wind driver function by the theoretical cross-polar-cap-potential correction (1+Q) often compensates for the saturation of an index, even though that index is associated with internal magnetospheric processes whereas Q is derived for solar-wind processes. There are composite geomagnetic indices E(1) that show no saturation when matched to their composite solar-wind driver functions S(1). When applied to other geomagnetic indices, the composite S(1) driver functions tend to compensate for index saturation at strong driving, but they also tend to introduce a nonlinearity at weak driving.

Understanding the nature and characteristics of high-frequency waves inside a flux rope may be important as the wave-particle interaction is important for charged-particle energization and the ensuing dissipation process. We analyze waves generated by an electron beam in a crater-shaped magnetic flux rope observed by MMS spacecraft on the dawnside tailward magnetopause. In this MMS observation, a depression of magnetic field, or a crater, of ∼100 km is located at the center of the magnetic flux rope of ∼650 km. There exist parallel and perpendicular electrostatic wave modes inside the depression of the magnetic field at the center of the flux rope, and they are distinguished by their locations and frequencies. The parallel mode exists at the center of the magnetic depression and its power spectrum peaks below Fce (electron cyclotron frequency). In contrast, the perpendicular mode exists in the outer region associated with the magnetic depression, and its power spectrum peaks near Fce. The linear analysis of kinetic instability using a generalized dispersion solver shows that the parallel mode can be generated by the electron beam of 5,000 km/s. They can thermalize electrons ≲100 eV effectively. However, the generation mechanism of the perpendicular mode is not clear yet, which requires further study.

Many prominences are supported by magnetic flux ropes. One important question is how we can determine whether the flux rope is weakly-twisted or strongly-twisted. In this paper, we attempted to check whether prominences supported by weakly-twisted and strongly-twisted flux ropes can manifest different features so that we might distinguish the two types of magnetic structures by their appearance. We performed pseudo three-dimensional simulations of two magnetic flux ropes with different twists. We found that the resulting two prominences differ in many aspects. The prominence supported by a weakly-twisted flux rope is composed mainly of transient threads, forming high-speed flows inside the prominence. Its horns are evident. Conversely, the one supported by a highly-twisted flux rope consists mainly of stable quasi-stationary threads, including longer independently trapped threads and shorter magnetically connected threads. It is also revealed that the prominence spine deviates from the flux rope axis in the vertical direction and from the photospheric polarity inversion line projected on the solar surface, especially for the weakly-twisted magnetic flux rope. The two types of prominences differ significantly in appearance. It is also suggested that a piling-up of short threads in highly-twisted flux ropes might account for the vertical-like threads in some prominences., 10 pages, 7 figures, accepted for publication in A&A

Ganymede is the only Solar System moon that generates a permanent magnetic field. Dynamics within the Ganymedean magnetosphere is thought to be driven by energy-transfer interactions on its upstream magnetopause. Previously in Kaweeyanun et al. (2020), https://doi.org/10.1029/2019GL086228 we created a steady-state analytical model of Ganymede's magnetopause and predicted global-scale magnetic reconnection to occur frequently throughout the surface. This paper subsequently provides the first assessment of Kelvin-Helmholtz (K-H) instability growth on the magnetopause. Using the same analytical model, we find that linear K-H waves are expected on both Ganymedean magnetopause flanks. Once formed, the waves propagate downstream at roughly half the speed of the external Jovian plasma flow. The Ganymedean K-H instability growth is asymmetric between magnetopause flanks due to the finite Larmor radius effect arising from large gyroradii of Jovian plasma ions. A small but notable enhancement is expected on the sub-Jovian flank according to the physical understanding of bulk plasma and local ion flows alongside comparisons to the well-observed magnetopause of Mercury. Further evaluation shows that nonlinear K-H vortices should be strongly suppressed by concurring global-scale magnetic reconnection at Ganymede. Reconnection is therefore the dominant cross-magnetopause energy-transfer mechanism and driver of global-scale plasma convection within Ganymede's magnetosphere.

International audience; The segmentation of blood vessels in medical images is a challenging task as they are thin, connected and tortuous. The detection of a connected vascular network is of the utmost importance in clinical applications (e.g. blood flow simulations, vascular network modeling and analysis). Deep learning approaches have been developed to tackle this issue, but they require a large annotated dataset for each new application of interest, which is very challenging to build for vascular networks. In this work, rather than learning the segmentation task, we propose to learn a reconnecting regularization term that learns geometric properties of vascular networks independent of the image modality. Therefore, this term generalizes better than deep learning segmentation models, and can be easily plugged into variational segmentation frameworks to detect vascular networks in different datasets without requiring annotations. We apply this approach on retinal images by training our reconnecting term on the STARE dataset and applying it on the DRIVE dataset. We show that our approach better preserves the connectivity of vascular networks than classic regularization terms in the literature. Finally, we illustrate the generalization power of our reconnecting term by applying it to other types of data.

Geomagnetic storms are an important aspect of space weather and can result in significant impacts on space- and ground-based assets. The majority of strong storms are associated with the passage of interplanetary coronal mass ejections (ICMEs) in the near-Earth environment. In many cases, these ICMEs can be traced back unambiguously to a specific coronal mass ejection (CME) and solar activity on the frontside of the Sun. Hence, predicting the arrival of ICMEs at Earth from routine observations of CMEs and solar activity currently makes a major contribution to the forecasting of geomagnetic storms. However, it is clear that some ICMEs, which may also cause enhanced geomagnetic activity, cannot be traced back to an observed CME, or, if the CME is identified, its origin may be elusive or ambiguous in coronal images. Such CMEs have been termed "stealth CMEs." In this review, we focus on these "problem" geomagnetic storms in the sense that the solar/CME precursors are enigmatic and stealthy. We start by reviewing evidence for stealth CMEs discussed in past studies. We then identify several moderate to strong geomagnetic storms (minimum Dst < -50 nT) in solar cycle 24 for which the related solar sources and/or CMEs are unclear and apparently stealthy. We discuss the solar and in situ circumstances of these events and identify several scenarios that may account for their elusive solar signatures. These range from observational limitations (e.g., a coronagraph near Earth may not detect an incoming CME if it is diffuse and not wide enough) to the possibility that there is a class of mass ejections from the Sun that have only weak or hard-to-observe coronal signatures. In particular, some of these sources are only clearly revealed by considering the evolution of coronal structures over longer time intervals than is usually considered. We also review a variety of numerical modelling approaches..., 60 pages, 25 figures, 5 tables. Accepted for publication in Space Science Reviews

International audience; Ablation of atrial fibrillation (AF) is the cornerstone therapy for patients with symptomatic AF resistant to anti-arrhythmic drugs or as first-line therapy, and is based on permanent pulmonary vein (PV) isolation. The presence of a conduction gap in a wide antral circumferential ablation lesion around PVs is often sufficient to transform an initially successful ablation into a procedural failure, thus necessitating a redo intervention. The strategy during a redo procedure is based on the detection and ablation of the reconnection gap. Finding gaps is often simple, but also sometimes challenging, because gaps may be difficult to detect, resulting in unnecessary radiofrequency delivery. The present review aimed to describe the various techniques published thus far to detect residual reconnections along the encircling ablation lines around PVs, to help electrophysiologists to detect and ablate reconnection gaps. © 2019 American College of Cardiology Foundation

We performed 2D magnetohydrodynamical numerical experiments to study the response of the coronal magnetic configuration to the newly emerging magnetic flux. The configuration includes an electric-current-carrying flux rope modeling the prominence floating in the corona and the background magnetic field produced by two separated magnetic dipoles embedded in the photosphere. Parameters for one dipole are fixed in space and time to model the quiet background, and those for another one are time dependent to model the new flux. These numerical experiments duplicate important results of the analytic solution but also reveal new results. Unlike previous works, the configuration here possesses no symmetry, and the flux rope could move in any direction. The non-force-free environment causes the deviation of the flux rope equilibrium in the experiments from that determined in the analytic solution. As the flux rope radius decreases, the equilibrium could be found, and it evolves quasi-statically until the flux rope reaches the critical location at which the catastrophe occurs. As the radius increases, no equilibrium exists at all. During the catastrophe, two current sheets form in different ways. One forms as the surrounding closed magnetic field is stretched by the catastrophe, and another one forms as the flux rope squeezes the magnetic field nearby. Although reconnection happens in both the current sheets, it erases the first one quickly and enhances the second simultaneously. These results indicate the occurrence of the catastrophe in asymmetric and non-force-free environment, and the non-radial motion of the flux rope following the catastrophe.

Case Report - New dielectric imaging modality in repeat ablation

On 5 May 2017, MMS observed a crater‐type flux rope on the dawnside tailward magnetopause with fluctuations. The boundary‐normal analysis shows that the fluctuations can be attributed to nonlinear Kelvin‐Helmholtz (KH) waves. Reconnection signatures such as flow reversals and Joule dissipation were identified at the leading and trailing edges of the flux rope. In particular, strong northward electron jets observed at the trailing edge indicated midlatitude reconnection associated with the 3‐D structure of the KH vortex. The scale size of the flux rope, together with reconnection signatures, strongly supports the interpretation that the flux rope was generated locally by KH vortex‐induced reconnection. The center of the flux rope also displayed signatures of guide‐field reconnection (out‐of‐plane electron jets, parallel electron heating, and Joule dissipation). These signatures indicate that an interface between two interlinked flux tubes was undergoing interaction, causing a local magnetic depression, resulting in an M‐shaped crater flux rope, as supported by reconstruction., Key Points MMS observed a magnetic flux rope formed on the boundary of a nonlinear Kelvin‐Helmholtz (KH) waveBoth in‐plane and midlatitude reconnection associated with the 3‐D structure of the KH vortex‐inducedflux rope were identifiedA current sheet at the flux rope center supported by reconstruction indicates two flux tubes interlinked to form a crater‐type flux rope

It is proposed that reconnection would be a main mechanism governing the plasma processes on auroral time scales in the topside ionosphere/high-latitude magnetosphere transition. It occurs in the downward current region between two narrow parallel closely spaced though separated downward current sheets. The field-aligned currents are carried by upward cold upper-ionospheric electrons closing the upward current in an adjacent region. This local process does primarily not affect the ambient field but generates an anomalous diffusivity., Comment: 13 pages, 4 Figures

Context: Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still being actively debated. Aims: We study six recurrent jets occurring in the active region NOAA 12644 on April 04, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit-jaw high spatial and temporal resolution images. Methods: The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We study the pre-jet phases by analyzing the intensity oscillations at the base of the jets with the wavelet technique. Results: A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like, double-chambered structure with cool emission on one side and hot emission in the other. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km/s) and accompanied by the cool surges and ejected kernels both moving at about 45 km/s. In the pre-phase of the jets, at their base we find quasi-periodic intensity oscillations in phase with small ejections; they have a period between 2 and 6 minutes and are reminiscent of acoustic or MHD waves. Conclusions: This series of jets and surges provides a good case-study to test the 2D and 3D magnetohydrodynamic (MHD) models that result from magnetic flux emergence. The double-chambered structure found in the observations corresponds to the cold and hot loop regions found in the models beneath the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appear in the models., Comment: 12 Pages, 11 Figures

Particle precipitation is a central aspect of space weather, as it strongly couples the magnetosphere and the ionosphere and can be responsible for radio signal disruption at high latitudes. We present the first hybrid-Vlasov simulations of proton precipitation in the polar cusps. We use two runs from the Vlasiator model to compare cusp proton precipitation fluxes during southward and northward interplanetary magnetic field (IMF) driving. The simulations reproduce well-known features of cusp precipitation, such as a reverse dispersion of precipitating proton energies, with proton energies increasing with increasing geomagnetic latitude under northward IMF driving, and a nonreversed dispersion under southward IMF driving. The cusp is also found more polewards in the northward IMF simulation than in the southward IMF simulation. In addition, we find that the bursty precipitation during southward IMF driving is associated with the transit of flux transfer events in the vicinity of the cusp. In the northward IMF simulation, dual lobe reconnection takes place. As a consequence, in addition to the high-latitude precipitation spot associated with the lobe reconnection from the same hemisphere, we observe lower-latitude precipitating protons which originate from the opposite hemisphere’s lobe reconnection site. The proton velocity distribution functions along the newly closed dayside magnetic field lines exhibit multiple proton beams travelling parallel and antiparallel to the magnetic field direction, which is consistent with previously reported observations with the Cluster spacecraft. In both runs, clear electromagnetic ion cyclotron waves are generated in the cusps and might further increase the calculated precipitating fluxes by scattering protons to the loss cone in the low-altitude cusp. Global kinetic simulations can improve the understanding of space weather by providing a detailed physical description of the entire near-Earth space and its internal couplings.

We present a novel numerical scheme for simulating the motion of relativistic charged particles in magnetospheres of compact objects, typically filled with highly magnetized collisionless plasmas. The new algorithm is based on a dynamic switch between the full system of equations of motion and a guiding center approximation. The switch between the two formulations is based on the magnetization of the plasma particles, such that the dynamics are accurately captured by the guiding center motion even when the gyro-frequency is under-resolved by the time step. For particles with a large gyro-radius, due to acceleration in, e.g., reconnecting current sheets, the algorithm adaptively switches to solve the full equations of motion instead. The new scheme is directly compatible with standard Particle-in-Cell codes, and is readily applicable in curved spacetimes via a dedicated covariant formulation. We test the performance of the coupled algorithm by evolving charged particles in electromagnetic configurations of reconnecting current sheets in magnetized plasma, obtained from special- and general-relativistic Particle-in-Cell simulations. The new coupled pusher is capable of producing highly accurate particle trajectories even when the time step is many orders of magnitude larger than the gyro-period, substantially reducing the restrictions of the temporal resolution.

MBArch -- The Contemporary Project The development of urban projects covers several issues, resulting in always facing different challenges with the biggest being the humans themselves. In that sense, with the rapid evolution of technology and globalization, we humans have lost the conversation between our body and our built environment. For that reason, it is important to establish a dialogue with a common language that can speak to today’s body. In our contemporary cities the dialogue happens in the way of how we live and experience the places we use. Using water as a critical element of our urban spaces, its experience and metaphysical nature plays a big role in the phenomenology of architectural understanding. It means, the importance of designing spaces that influence the outer body senses that both obtain and give meaning to its surroundings leading to a psychological sense of place. In other words, the body is the main generator of design and this thesis explores its dialogue with the environment through water as an important element of architecture.

International audience; While double ion populations, with a cold population originating from the solar wind and a hotter one from the magnetosphere, are frequently observed in the low-latitude boundary layers at the Earth's magnetopause, similar double electron populations are observed less often. A preliminary study of magnetopause crossings characteristics was used to determine the typical locations and energy spectra of ion and electron populations near the magnetopause. Then, we set up an automated detection algorithm for identifying regions with concomitant double populations in both ion and electron energy spectra. The statistical study was carried out on 7 years of Time History of Events and Macroscale Interactions during Substorms particle data, to determine the interplanetary magnetic field conditions in the upstream solar wind for these double populations. The results suggest that such concomitant ion and electron double population boundary layers form preferentially in the subsolar region and under northward interplanetary magnetic field but with a significant BY component. We interpret this finding as the result of reconnection of the same magnetosheath field line in both hemispheres with at least one end reconnecting in its hemisphere at lower latitude with a closed magnetospheric field line that already contains a hot electron source.

Context.The Kelvin-HeImholtz (KH) instability is a nonlinear shear-driven instability that develops at the interface between shear flows in plasmas. KH waves have been inferred in various astrophysical plasmas, and have been observed in situ at the magnetospheric boundaries of solar-system planets and through remote sensing at the boundaries of coronal mass ejections.Aims.KH waves are also expected to develop at flow shear interfaces in the solar wind. While they were hypothesized to play an important role in the mixing of plasmas and in triggering solar wind fluctuations, their direct and unambiguous observation in the solar wind was still lacking.Methods.We report in situ observations of quasi-periodic magnetic and velocity field variations plausibly associated with KH waves using Solar Orbiter during its cruise phase. They are found in a shear layer in the slow solar wind in the close vicinity of the heliospheric current sheet. An analysis was performed to derive the local configuration of the waves. A 2D magnetohydrodynamics simulation was also set up with approximate empirical values to test the stability of the shear layer. In addition, magnetic spectra of the event were analyzed.Results.We find that the observed conditions satisfy the KH instability onset criterion from the linear theory analysis, and its development is further confirmed by the simulation. The current sheet geometry analyses are found to be consistent with KH wave development, albeit with some limitations likely owing to the complex 3D nature of the event and solar wind propagation. Additionally, we report observations of an ion jet consistent with magnetic reconnection at a compressed current sheet within the KH wave interval. The KH activity is found to excite magnetic and velocity fluctuations with power law scalings that approximately followk−5/3andk−2.8in the inertial and dissipation ranges, respectively. Finally, we discuss reasons for the lack of in situ KH wave detection in past data.Conclusions.These observations provide robust evidence of KH wave development in the solar wind. This sheds new light on the process of shear-driven turbulence as mediated by the KH waves with implications for the driving of solar wind fluctuations.

著者人数: 20名, Accepted: 2019-05-28, 資料番号: SA1190061000

A supersonic flow of magnetized plasma is produced by the application of a 1 MA-peak, 500 ns current pulse to a cylindrical arrangement of parallel wires, known as an inverse wire array. The plasma flow is produced by the J × B acceleration of the ablated wire material, and a magnetic field of several Tesla is embedded at source by the driving current. This setup has been used for a variety of experiments investigating the interactions of magnetized plasma flows. In experiments designed to investigate magnetic reconnection, the collision of counter-streaming flows, carrying oppositely directed magnetic fields, leads to the formation of a reconnection layer in which we observe ions reaching temperatures much greater than predicted by classical heating mechanisms. The breakup of this layer under the plasmoid instability is dependent on the properties of the inflowing plasma, which can be controlled by the choice of the wire array material. In other experiments, magnetized shocks were formed by placing obstacles in the path of the magnetized plasma flow. The pile-up of magnetic flux in front of a conducting obstacle produces a magnetic precursor acting on upstream electrons at the distance of the ion inertial length. This precursor subsequently develops into a steep density transition via ion-electron fluid decoupling. Obstacles which possess a strong private magnetic field affect the upstream flow over a much greater distance, providing an extended bow shock structure. In the region surrounding the obstacle the magnetic pressure holds off the flow, forming a void of plasma material, analogous to the magnetopause around planetary bodies with self-generated magnetic fields., Department of Energy (Awards DE-NA0003764, DE-F03-02NA00057, DE-SC-0001063, DE-SC0016215), National Science Foundation (Award DE-SC0016215), Air Force Office of Scientific Research (Grant FA9550-17-1-0036), Engineering and Physical Sciences Research Council (EPSRC) (Grant EP/ N013379/1)

We conduct forward-modeling analysis based on our 2.5 dimensional magnetohydrodynamics (MHD) simulation of magnetic flux rope (MFR) formation and eruption driven by photospheric converging motion. The current sheet (CS) evolution during the MFR formation and eruption process in our MHD simulation can be divided into four stages. The current sheet (CS) evolution during the MFR formation and eruption process in our MHD simulation can be divided into four stages. The first stage shows the CS forming and gradually lengthening. Resistive instabilities that disrupt the CS mark the beginning of the second stage. Magnetic islands disappear in the third stage and reappear in the fourth stage. Synthetic images and light curves of the seven Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA) channels, i.e., 9.4 nm, 13.1 nm, 17.1 nm, 19.3 nm, 21.1 nm, 30.4 nm, and 33.5 nm, and the 3-25 keV thermal X-ray are obtained with forward-modeling analysis. The loop-top source and the coronal sources of the soft X-ray are reproduced in forward modeling. The light curves of the seven SDO/AIA channels start to rise once resistive instabilities develop. The light curve of the 3-25 keV thermal X-ray starts to go up when the reconnection rate reaches one of its peaks. Quasiperiodic pulsations (QPPs) appear twice in the SDO/AIA 17.1 nm, 21.1 nm, and 30.4 nm channels, corresponding to the period of chaotic (re)appearance and CS-guided displacements of the magnetic islands. QPPs appear once in the SDO/AIA 9.4 nm and 33.5 nm channels after the disruption of the CS by resistive instabilities and in the 19.3 nm channel when the chaotic motion of the magnetic islands reappears., The content of the paper has been published on ApJ. This version on arXiv is an improved version of the published one in ApJ, and some typos in the published one have been corrected

In the planetary magnetospheres there are specific places connected with velocity breakdown, reconnection, and dynamo processes. Here we pay attention to sliding layers. Sliding layers are formed in the ionosphere, on separatrix surfaces, at the magnetopauses and boundaries of stellar astrospheres, and at the Alfvén radius in the equatorial magnetosphere of rapidly rotating strongly magnetized giant planets. Although sliding contacts usually occur in thin local layers, their influence on the global structure of the surrounding space is very great. Therefore, they are associated with non-local processes that play a key role on a large scale. There can be an exchange between different forms of energy, a generation of strong field-aligned currents and emissions, and an amplification of magnetic fields. Depending on the conditions in the magnetosphere of the planet/exoplanet and in the flow of magnetized plasma passing it, different numbers of sliding layers with different configurations appear. Some are associated with regions of auroras and possible radio emissions. The search for planetary radio emissions is a current task in the detection of exoplanets.

International audience; Localized kinetic-scale regions of strong current are believed to play an important role in plasma thermalization and particle acceleration in turbulent plasmas. We present a detailed study of a strong localized current, 4900 nA m-2, located at a fast plasma jet observed in the magnetosheath downstream of a quasi-parallel shock. The thickness of the current region is ∼3 ion inertial lengths and forms at a boundary separating magnetosheath-like and solar wind-like plasmas. On ion scales the current region has the shape of a sheet with a significant average normal magnetic field component but shows strong variations on smaller scales. The dynamic pressure within the magnetosheath jet is over 3 times the solar wind dynamic pressure. We suggest that the current sheet is forming due to high velocity shears associated with the jet. Inside the current sheet we observe local electron acceleration, producing electron beams, along the magnetic field. However, there is no clear sign of ongoing reconnection. At higher energies, above the beam energy, we observe a loss cone consistent with part of the hot magnetosheath-like electrons escaping into the colder solar wind-like plasma. This suggests that the acceleration process within the current sheet is similar to the one that occurs at shocks, where electron beams and loss cones are also observed. Therefore, electron beams observed in the magnetosheath do not have to originate from the bow shock but can also be generated locally inside the magnetosheath.

We consider a diffuse interface model for tumour growth consisting of a Cahn--Hilliard equation with source terms coupled to a reaction-diffusion equation. The coupled system of partial differential equations models a tumour growing in the presence of a nutrient species and surrounded by healthy tissue. The model also takes into account transport mechanisms such as chemotaxis and active transport. We establish well-posedness results for the tumour model and a variant with a quasi-static nutrient. It will turn out that the presence of the source terms in the Cahn--Hilliard equation leads to new difficulties when one aims to derive a priori estimates. However, we are able to prove continuous dependence on initial and boundary data for the chemical potential and for the order parameter in strong norms., 29 pages, minor typos corrected, accepted for publication

The magnetospheric cusps are important sites of the coupling of a magnetosphere with the solar wind. The combination of both ground- and space-based observations at Earth have enabled considerable progress to be made in understanding the terrestrial cusp and its role in the coupling of the magnetosphere to the solar wind via the polar magnetosphere. Voyager 2 fully explored Neptune's cusp in 1989 but highly inclined orbits of the Cassini spacecraft at Saturn present the most recent opportunity to repeatedly studying the polar magnetosphere of a rapidly rotating planet. In this paper we discuss observations made by Cassini during two passes through Saturn's southern polar magnetosphere. Our main findings are that i) Cassini directly encounters the southern polar cusp with evidence for the entry of magnetosheath plasma into the cusp via magnetopause reconnection, ii) magnetopause reconnection and entry of plasma into the cusp can occur over a range of solar wind conditions, and iii) double cusp morphologies are consistent with the position of the cusp oscillating in phase with Saturn's global magnetospheric periodicities., Journal accepted version before copy-editing: 55 pages, 12 figures. Accepted for publication in J. Geophys. Res. Space Physics

Jets often have a helical structure containing ejected plasma that is both hot and also cooler and denser than the corona. Various mechanisms have been proposed to explain how jets are primarily attributed to a magnetic reconnection between the emergence of magnetic flux and environment or that of twisted photospheric motions that bring the system into a state of instability. Multi-wavelength observations of a twisted jet observed with AIA and IRIS were used to understand how the twist was injected into the jet. We followed the magnetic history of the active region based on the analysis of HMI vector magnetic field computed with the UNNOFIT code. This region is the result of the collapse of two emerging magnetic fluxes (EMFs) overlaid by arch filament systems that have been well-observed with AIA, IRIS, and NVST in H-alpha. In the magnetic field maps, we found evidence of the pattern of a long sigmoidal flux rope (FR) along the polarity inversion line between the two EMFs, which is the site of the reconnection. Before the jet, an extension of the FR was present and a part of it was detached and formed a small bipole with a bald patch (BP) region, which dynamically became an X-current sheet over the dome of one EMF where the reconnection took place. At the time of the reconnection, the Mg II spectra exhibited a strong extension of the blue wing that is decreasing over a distance of 10 Mm (from -300 km/s to a few km/s). This is the signature of the transfer of the twist to the jet. A comparison with numerical magnetohydrodynamics (MHD) simulations confirms the existence of the long FR. We conjecture that there is a transfer of twist to the jet during the extension of the FR to the reconnection site without FR eruption. There connection would start in the low atmosphere in the BP reconnection region and extend at an X-point along the current sheet formed above., 22 pages, 13 figures, Astronomy and Astrophysics

ispartof: ASTROPHYSICAL JOURNAL vol:898 issue:1 status: published

The 'standard solar' flare model collects all physical ingredients identified by multi-wavelength observations of our Sun: magnetic reconnection, fast particle acceleration and the resulting emission at various wavelengths, especially in soft to hard X-ray channels. Its cartoon representation is found throughout textbooks on solar and plasma astrophysics, and guides interpretations of unresolved energetic flaring events on other stars, accretion disks and jets. To date, a fully self-consistent model that reproduces the standard scenario in all its facets is lacking, since this requires the combination of a large scale, multi-dimensional magnetohydrodynamic (MHD) plasma description with a realistic fast electron treatment. Here, we demonstrate such a novel combination, where MHD combines with an analytic fast electron model, adjusted to handle time-evolving, reconnecting magnetic fields and particle trapping. This allows to study (1) the role of fast electron deposition in the triggering of chromospheric evaporation flows; (2) the physical mechanisms that generate various hard X-ray sources at chromospheric footpoints or looptops; and (3) the relationship between soft X-ray and hard X-ray fluxes throughout the entire flare loop evolution. For the first time, this self-consistent solar flare model demonstrates the observationally suggested relationship between flux swept out by the hard X-ray footpoint regions, and the actual reconnection rate at the X-point, which is a major unknown in flaring scenarios. We also demonstrate that a looptop hard X-ray source can result from fast electron trapping., 23 pages, 11 figures

A Monte Carlo method of investigating the effects of placing selection criteria on the magnetic signature of in situ encounters with flux ropes is presented. The technique is applied to two recent flux rope surveys of MESSENGER data within the Hermean magnetotail. It is found that the different criteria placed upon the signatures will preferentially identify slightly different subsets of the underlying population. Quantifying the selection biases first allows the distributions of flux rope parameters to be corrected, allowing a more accurate estimation of the intrinsic distributions. This is shown with regard to the distribution of flux rope radii observed. When accounting for the selection criteria, the mean radius of Hermean magnetotail quasi‐force‐free flux ropes is found to be 589−269+273 km. Second, it is possible to weight the known identifications in order to determine a rate of recurrence that accounts for the presence of the structures that will not be identified. In the case of the Hermean magnetotail, the average rate of quasi‐force‐free flux ropes is found to 0.12 min−1 when selection effects are accounted for (up from 0.05 min−1 previously inferred from observations)., Key Points A Monte Carlo method is presented to estimate and correct for sampling biases in spacecraft surveys of magnetic flux ropesMethod allows the correction of observed distributions (e.g., flux rope radii) according to the selection criteria employedAccounting for unidentified flux ropes increases the average rate of flux ropes in Mercury's magnetotail from 0.05 to 0.12 min−1

International audience; The influence of the interplanetary magnetic field (IMF) cone angle θ (the angle between the IMF direction and the Sun-Earth line) on the invariant latitudes of the footprints of the field-aligned currents (FACs) in the magnetotail has been investigated. We performed a statistical study of 542 FAC cases observed by the four Cluster spacecraft in the Northern Hemisphere. The results show that there are almost no FACs when the IMF cone angle is less than 10°, and there are indications of the FACs in the plasma sheet boundary layers being weak under the radial IMF conditions. The footprints of the large FAC (>10 nA/m2) cases are within invariant latitudes 60°, which implies that the footprints of the large FACs mainly expand equatorward with large IMF cone angle. The equatorward boundary of the FAC footprints in the polar region decreases with increasing IMF cone angle (and has a better correlation for northward IMF), which shows that the IMF cone angle plays an important controlling role in FAC distributions in the magnetosphere-ionosphere coupling system. There is almost no correlation between the poleward boundary and the IMF cone angle for both northward and southward IMF. This is because the poleward boundary movement is limited by an enhanced lobe magnetic flux. This is the first time a correlation between FAC footprints in the polar region and IMF cone angles has been determined.

The B-field structures of two ICMEs each observed by a pair of spacecraft close to radial alignment have been analysed. The ICMEs were observed in situ by MESSENGER and STEREO-B in Nov. 2010 and Nov. 2011, while the spacecraft were separated by more than 0.6 AU in heliocentric distance, less than 4{\deg} in heliographic longitude, and less than 7{\deg} in heliographic latitude. Both ICMEs took around 2 days to travel between the spacecraft. The ICME B-field profiles observed by MESSENGER have been mapped to the heliocentric distance of STEREO-B and compared directly to the profiles observed by STEREO-B. Figures that result from this mapping allow for easy qualitative assessment of similarity in the profiles. Macroscale features in the profiles that varied on timescales of 1 hour, and which corresponded to the underlying flux rope structure of the ICMEs, were well correlated in the solar east-west and north-south directions, with Pearson's correlation coefficients of around 0.85 and 0.95, respectively; microscale features with timescales of 1 minute were uncorrelated. Overall correlation values in the profiles of one ICME were increased when an apparent change in the flux rope axis direction between the observing spacecraft was taken into account. The high degree of similarity seen in the B-field profiles may be interpreted in in two ways. If the spacecraft sampled the same region of each ICME (i.e. if the spacecraft angular separations can be neglected), the similarity indicates that there was little evolution in the underlying structure of the sampled region during propagation. Alternatively, if the spacecraft observed different, nearby regions within the ICMEs, it indicates that there was spatial homogeneity across those different regions. The field structure similarity observed in these ICMEs points to the value of placing in situ space weather monitors well upstream of the Earth., Comment: 22 pages, 9 figures

International audience; This paper reports on Magnetospheric Multiscale observations of whistler mode chorus and higher-frequency electrostatic waves near and within a reconnection diffusion region on 23 November 2016. The diffusion region is bounded by crescent-shaped electron distributions and associated dissipation just upstream of the X-line and by magnetic field-aligned currents and electric fields leading to dissipation near the electron stagnation point. Measurements were made southward of the X-line as determined by southward directed ion and electron jets. We show that electrostatic wave generation is due to magnetosheath electron beams formed by the electron jets as they interact with a cold background plasma and more energetic population of magnetospheric electrons. On the magnetosphere side of the X-line the electron beams are accompanied by a strong perpendicular electron temperature anisotropy, which is shown to be the source of an observed rising-tone whistler mode chorus event. We show that the apex of the chorus event and the onset of electrostatic waves coincide with the opening of magnetic field lines at the electron stagnation point.

We report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5 ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from E × B drift in the interval where the out-of-plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out-of-plane current is transitioning to in-plane current, the electron momentum equation is not satisfied at 7.5 ms resolution.

The Kelvin-Helmholtz instability (KHI) is a known mechanism for penetration of solar wind matter into the magnetosphere. Using three-dimensional, resistive magnetohydrodynamic simulations, the double mid-latitude reconnection (DMLR) process was shown to efficiently exchange solar wind matter into the magnetosphere, through mixing and reconnection. Here, we compute test particle orbits through DMLR configurations. In the instantaneous electromagnetic fields, charged particle trajectories are integrated using the guiding centre approximation. The mechanisms involved in the electron particle orbits and their kinetic energy evolutions are studied in detail, to identify specific signatures of the DMLR through particle characteristics. The charged particle orbits are influenced mainly by magnetic curvature drifts. We identify complex, temporarily trapped, trajectories where the combined electric field and (reconnected) magnetic field variations realize local cavities where particles gain energy before escaping. By comparing the orbits in strongly deformed fields due to the KHI development, with the textbook mirror-drift orbits resulting from our initial configuration, we identify effects due to current sheets formed in the DMLR process. We do this in various representative stages during the DMLR development., Comment: Matching accepted version in AGU JGR: Space Physics

We report Magnetospheric Multiscale observations of electron pressure gradient electric fields near a magnetic reconnection diffusion region using a new technique for extracting 7.5ms electron moments from the Fast Plasma Investigation. We find that the deviation of the perpendicular electron bulk velocity from E × B drift in the interval where the out-of-plane current density is increasing can be explained by the diamagnetic drift. In the interval where the out-of-plane current is transitioning to in-plane current, the electron momentum equation is not satisfied at 7.5ms resolution.

The origins and generation mechanisms of the slow solar wind are still unclear. Part of the slow solar wind is populated by "number density structures", discrete patches of increased number density that are frozen in to and move with the bulk solar wind. In this paper we aimed to provide the first in-situ statistical study of number density structures in the inner heliosphere. We reprocessed in-situ ion distribution functions measured by Helios in the inner heliosphere to provide a new reliable set of proton plasma moments for the entire mission. From this new data set we looked for number density structures measured within 0.5 AU of the Sun and studied their properties. We identified 140 discrete areas of enhanced number density. The structures occurred exclusively in the slow solar wind and spanned a wide range of length scales from 50 Mm to 2000 Mm, which includes smaller scales than have been previously observed. They were also consistently denser and hotter that the surrounding plasma, but had lower magnetic field strengths, and therefore remained in pressure balance. Our observations show that these structures are present in the slow solar wind at a wide range of scales, some of which are too small to be detected by remote sensing instruments. These structures are rare, accounting for only 1\% of the slow solar wind measured by Helios, and are not a significant contribution to the mass flux of the solar wind., Comment: Accepted for publication in A&A

Fast plasma flows produced as outflow jets from reconnection sites or X lines are a key feature of the dynamics in the Earth's magnetosphere. We have used a polar plane simulation of the hybrid-Vlasov model Vlasiator, driven by steady southward interplanetary magnetic field and fast solar wind, to study fast plasma sheet ion flows and related magnetic field structures in the Earth's magnetotail. In the simulation, lobe reconnection starts to produce fast flows after the increasing pressure in the lobes has caused the plasma sheet to thin sufficiently. The characteristics of the earthward and tailward fast flows and embedded magnetic field structures produced by multi-point tail reconnection are in general agreement with spacecraft measurements reported in the literature. The structuring of the flows is caused by internal processes: interactions between major X points determine the earthward or tailward direction of the flow, while interactions between minor X points, associated with leading edges of magnetic islands carried by the flow, induce local minima and maxima in the flow speed. Earthward moving flows are stopped and diverted duskward in an oscillatory (bouncing) manner at the transition region between tail-like and dipolar magnetic fields. Increasing and decreasing dynamic pressure of the flows causes the transition region to shift earthward and tailward, respectively. The leading edge of the train of earthward flow bursts is associated with an earthward propagating dipolarization front, while the leading edge of the train of tailward flow bursts is associated with a tailward propagating plasmoid. The impact of the dipolarization front with the dipole field causes magnetic field variations in the Pi2 range. Major X points can move either earthward or tailward, although tailward motion is more common. They are generally not advected by the ambient flow. Instead, their velocity is better described by local parameters, such that an X point moves in the direction of increasing reconnection electric field strength. Our results indicate that ion kinetics might be sufficient to describe the behavior of plasma sheet bulk ion flows produced by tail reconnection in global near-Earth simulations. Keywords. Magnetospheric physics (magnetospheric configuration and dynamics; plasma sheet) – space plasma physics (numerical simulation studies)

Collisionless plasmas, mostly present in astrophysical and space environments, often require a kinetic treatment as given by the Vlasov equation. Unfortunately, the six-dimensional Vlasov equation can only be solved on very small parts of the considered spatial domain. However, in some cases, e.g. magnetic reconnection, it is sufficient to solve the Vlasov equation in a localized domain and solve the remaining domain by appropriate fluid models. In this paper, we describe a hierarchical treatment of collisionless plasmas in the following way. On the finest level of description, the Vlasov equation is solved both for ions and electrons. The next courser description treats electrons with a 10-moment fluid model incorporating a simplified treatment of Landau damping. At the boundary between the electron kinetic and fluid region, the central question is how the fluid moments influence the electron distribution function. On the next coarser level of description the ions are treated by an 10-moment fluid model as well. It may turn out that in some spatial regions far away from the reconnection zone the temperature tensor in the 10-moment description is nearly isotopic. In this case it is even possible to switch to a 5-moment description. This change can be done separately for ions and electrons. To test this multiphysics approach, we apply this full physics-adaptive simulations to the Geospace Environmental Modeling (GEM) challenge of magnetic reconnection., Comment: 13 pages, 5 figures

Earth’s magnetopause separating the fast and often turbulent magnetosheath and the relatively stagnant magnetosphere provides various forms of free energy that generate low-frequency surface waves. The source mechanism of this energy includes current-driven kinetic physical processes such as magnetic reconnection on the dayside magnetopause and flux transfer events drifting along the magnetopause, and velocity shear-driven (Kelvin-Helmholtz instability) or density/ pressure gradient-driven (Rayleigh-Taylor instability) magnetohydro-dynamics (MHD) instabilities. The solar wind external perturbations (impulsive transient pressure pulses or quasi-periodic dynamic pressure variations) act as seed fluctuations for the magnetopause waves and trigger ULF pulsations inside the magnetosphere via global modes or mode conversion at the magnetopause. The magnetopause waves thus play an important role in the solar wind-magnetosphere coupling, which is the key to space weather. This paper presents recent findings regarding the generation of surface waves (e.g., Kelvin- Helmholtz waves) at the Earth’s magnetopause and analytic and observational studies accountable for the linking of the magnetopause waves and inner magnetospheric ULF pulsations, and the impacts of magnetopause waves on the dynamics of the magnetopause and on the inner magnetosphere.

International audience; With electron and magnetic field data obtained by the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we have identified closed magnetic field lines, with both foot points embedded in the dayside ionosphere, extending up to 6,200 km altitude into the Martian tail. This topology is deduced from photoelectrons produced in the dayside ionosphere being observed traveling both parallel and antiparallel to the magnetic field. At trapped-zone pitch angles (within a range centered on 90° where electrons magnetically reflect before interacting with the atmosphere), cases with either solar wind electrons or photoelectrons have been found, indicating different formation mechanisms for these closed loops. These large closed loops are present in MHD simulations. The case with field-aligned photoelectrons mixed with solar wind electrons having trapped-zone pitch angles is likely to be associated with reconnection, while the case with photoelectrons at all pitch angles is probably due to closed field lines being pulled tailward by the surrounding plasma flow. By utilizing an algorithm for distinguishing photoelectrons from solar wind electrons in pitch angle-resolved energy spectra, we systematically map the spatial distribution and occurrence rate of these closed magnetic loops over the region sampled by the MAVEN orbit. We find that the occurrence rate ranges from a few percent to a few tens of percent outside of the optical shadow and less than one percent within the shadow. These observations can be used to investigate the general magnetic topology in the tail, which is relevant to cold ion escape, reconnection, and flux ropes.

著者人数: 19名, Accepted: 2018-01-07, 資料番号: SA1170245000

Multispacecraft measurements from the Time History of Events and Macroscale Interactions during Substorms (THEMIS) mission are used to probe the spatial extent of an X line at the dayside magnetopause. A case study from 21 April 2014 is presented where two THEMIS spacecraft have a near-simultaneous encounter with the equatorial dayside magnetopause separated by 3.9 Earth radii. Both spacecraft observe similar steady inflow conditions with southward interplanetary magnetic field and a high magnetic shear angle at the magnetopause (133 degrees) boundary. One spacecraft observes clear fluid and kinetic signatures of active magnetic reconnection, while the other spacecraft does not observe reconnection. The predicted location of reconnection across the magnetopause is found using several theoretical models and a Block Adaptive Tree Solarwind Roe-type Upwind Scheme (BATS-R-US) MHD simulation. Each model predicts a continuous X line passing close to the two spacecraft, suggesting both would observe reconnection, if active. Using the constraints of the multipoint measurements, the extent or length L of the reconnection is estimated to be 2.4L

We investigate the effects of different initialisation methods of the GUMICS-4 global magnetohydrodynamic (MHD) simulation to the dynamics in different parts of the Earth's magnetosphere and hence compare five 12 h simulation runs that were initiated by 3 h of synthetic data and followed by 9 h of solar wind measurements using the OMNI data as input. As a reference, we use a simulation run that includes nearly 60 h of OMNI data as input prior to the 9 h interval examined with different initialisations. The selected interval is a high-speed stream event during a 10-day interval (12–22 June 2007). The synthetic initialisations include stepwise, linear and sinusoidal functions of the interplanetary magnetic field with constant density and velocity values. The results show that the solutions converge within 1 h to give a good agreement in both the bow shock and the magnetopause position. However, the different initialisation methods lead to local differences which should be taken into consideration when comparing model results to satellite measurements.

From a new anti-parallel initial condition using long vortices, three-dimensional incompressible turbulence forms after two re- connection steps and the formation of at least one set of vortex rings, similar to how anti-parallel quantum vortices evolve [10] . The long domain allows multiple reconnections, which enhance vortex stretching rates and the generation of small-scale vortex structures within the vortex rings. For the Navier-Stokes vortices, further new features are a profile less likely to shed vortex sheets and an improved mapping of the direction of the vorticity onto the three-dimensional mesh. The vortices evolve via the following steps: First, until the first reconnection, dynamics largely consistent with how vortices attract in the Euler equations. Second, vortex reconnection where the symmetry planes meet. Third, a series of vortex rings, with the stretching at each following set of reconnections leading to the new reconnections and rings. Roughly half of the circulation reconnects into two “bridges”, leaving two distinct “threads”, as he extra stretching transforms the threads into spirals wrapped around the bridges. It is argued that these spirals are the source of the observed k −5 / 3 energy spectra and other statistics commonly associated with high Reynolds number turbulence.

Cette introduction éclaire le signifié du concept de dette écologique, à travers une mise en perspective de ses définitions et de ses implications. Quel est « pouvoir » du concept la dette écologique ? Quels en sont les objets (dette matérielle ou immatérielle) et les conséquences ? Ce concept peut-il soutenir un travail de reconnexion du monde sous l’angle de l’acceptation d’une dette infinie ? This paper enlights the concept of ecological debt through the diversity of its definitions and consequences. What is the “power” of the concept ? What are the objects (material and immaterial debt) and its consequences ?

We follow-up the proposal by Cowley et al. (2004) that the plasma circulation in the magnetospheres of the giant planets is a combination of two cycles or circulation systems. The Vasyliunas cycle transports heavy material ionized deep within the magnetosphere eventually to loss in the magnetotail. The second cycle is driven by magnetic reconnection between the planetary and the solar wind magnetic fields (the Dungey cycle) and is found on flux tubes poleward of those of the Vasyliunas cycle. We examine features of the Dungey system, particularly what occurs out of the equatorial plane. The Dungey cycle requires reconnection on the dayside, and we suggest that at the giant planets the dayside reconnection occurs preferentially in the morning sector. Second, we suggest that most of the solar wind material that enters through reconnection on to open flux tubes on the dayside never gets trapped on closed field lines but makes less than one circuit of the planet and exits down tail. In its passage to the nightside, the streaming ex-solar wind material is accelerated centrifugally by the planetary rotation primarily along the field; thus, in the tail it will appear very like a planetary wind. The escaping wind will be found on the edges of the tail plasma sheet, and reports of light ion streams in the tail are likely due to this source. The paper concludes with a discussion of high-latitude circulation in the absence of reconnection between the solar wind and planetary field. ispartof: Journal of Geophysical Research: Space Physics vol:121 issue:6 pages:5394-5403 status: published

Los estudios sobre alimentación se inclinan por temas sobre diversos problemas en términos de acceso y de calidad de los alimentos. Al nivel mundial las discusiones advierten sobre el proceso de industrialización de la alimentación y vinculan el tema de lo rural como un potencializador de las nuevas relaciones de producción y consumo como punto central para el proceso de reconexión y relocalización, los cuales constituyen estrategias alternativas y de resistencia al modelo hegemónico. En ese escenario de discusión, el presente artículo busca debatir la realidad rural del estado de Rio Grande do Sul (RS), argumentando que las relaciones de producción y consumo no están totalmente desconectadas. Pero esta desconexión se ha acelerado por los límites derivados de las políticas públicas y normas sanitarias vigentes en Brasil. Sin embargo, las estrategias de valorización del origen de los productos adoptadas en muchos lugares del estado de Rio Grande do Sul presentan limitaciones para la formalización de la producción de alimentos. Promueven, en consecuencia, la desaparición de prácticas artesanales y la diversificación de las unidades de producción familiares o la manutención de la informalidad. En el estudio también se identificó que el proceso de formalización está promoviendo la especialización de los productores y el encarecimiento de los alimentos, como consecuencia de las exigencias burocráticas y sanitarias, además de la pérdida de características artesanales de los alimentos en virtud de los patrones de calidad industriales impuestos por la legislación. Se desataca así la necesidad de discutir sobre los patrones de calidad de los alimentos vigentes en Brasil, que respeten la producción artesanal de los alimentos como forma de valorizar y preservar saberes y prácticas conectadas. Es comprensible que la discusión brasileña no debe centrarse en la búsqueda de la reconexión o relocalización como en Europa, sino en la valorización de los productos alimentarios y en las relaciones de producción y consumo existentes, permitiendo de esta manera la reproducción de los alimentos y de los medios de vida rural. There is a consensus in food studies which points out many problems in terms of access and the quality of food. Global discussions warn of the food industrialization process and suggest that the rural become a locus of new relations of production and consumption with a focus to the process of reconnection and relocalization. These analyzes suggest that these processes are strategies of alternative and resistance to the hegemonic agrifood model. This article seeks to discuss the rural reality of Rio Grande do Sul by arguing that, although in our context the relations of production and consumption have not been totally disconnected, they have been accelerated by public policies and existing sanitary standards in Brazil. However, the strategies of valorization of the product origin which are adopted in many places in Rio Grande do Sul present limits to the formalization of food production, which brings about the disappearance of both traditional practices of food production and diversification of family production units or the persistence of informality. It could be observed that the formalization process has been promoting the specialization of producers and an increase in food prices as a consequence of bureaucratic and sanitary demands. Besides that, it has brought about a loss of the artisanal characteristics of food production in view of the industrial quality standards imposed by law. Thus, it points out the need for discussion on quality standards in vigor in Brazil regarding the traditional food production as a way to value and preserve connected knowledge and practices. In this sense, we state that the Brazilian case does not follow the same perspective of reconnection or relocalization as it is happening in Europe, but in the valorization of existing food products and the corresponding production and consumer relations, allowing food maintenance as well as rural livelihood reproduction. Des études sur l’alimentation mise en scène des problèmes en matière d’accès et de qualité des aliments. Les débats mondiaux misent en garde le processus d’industrialisation de la nourriture et indiquent le milieu rural comme facilitateur de nouveaux rapports de production et de consommation avec une attention sur le processus de reconnexion et de relocalisation, qui sont des solutions alternatives et en même temps stratégies de résistance au modèle hégémonique. Dans ce cadre, cet essai propose de discuter la réalité rurale de l’État du Rio Grande do Sul (Brésil), mise en évidence qui les rapports de production et de consommation n’étaient pas totalement déconnectés, mais ont été accélérées par les limites découlant des politiques publiques et des normes sanitaires en vigueur au Brésil. Cependant, les stratégies de rétablissement de l’origine des produits adoptées en nombreux endroits dans le Rio Grande do Sul, ont des limites pour formaliser la production d’aliments, s’entraînant de la disparition de pratiques artisanales et de la diversification des unités de production familiales ou même en maintient de l’informalité. Nous avons identifié que le processus de formalisation est en train de conduire à la spécialisation des agriculteurs et à la hausse des prix de l’alimentation en raison des exigences bureaucratiques et sanitaires, au-delà de la perte des caractéristiques artisanales en raison des paramètres de qualité industrielle imposées par la législation. Mise en regard ainsi la nécessité d’un débat sur les normes de qualité des aliments en vigueur au Brésil concernant à la production artisanale de l’alimentation, comme un moyen de valoriser et de préserver les savoir-faire. Il est entendu que le débat brésilien ne devrait pas se concentrer sur la reconnexion ou la relocalisation de la même façon qu’en Europe, mais sur la valorisation des produits alimentaires et des rapports de production et de consommation existantes, permettant ainsi la reproduction des modes et moyens de vie ruraux. Estudos sobre a alimentação apontam diversos problemas no que tange ao acesso e a qualidade dos alimentos. Discussões mundiais advertem sobre o processo de industrialização da alimentação e apontam o rural como potencializador de novas relações de produção e consumo com foco para o processo de reconexão e relocalização, os quais constituem estratégias alternativas e de resistência ao modelo hegemônico. Nesse cenário de discussão, o presente ensaio busca debater a realidade rural do Rio Grande do Sul, argumentando que as relações de produção e consumo não foram totalmente desconectadas, mas vêm sendo aceleradas pelos limites decorrentes de políticas públicas e padrões sanitários vigentes no Brasil. Contudo, as estratégias de valorização da origem dos produtos, adotadas em muitos locais no Rio Grande do Sul, apresentam limites para a formalização da produção de alimentos, promovendo o desaparecimento de práticas artesanais e da diversificação das unidades de produção familiares ou a manutenção da informalidade. Identificou-se ainda que o processo de formalização vem promovendo a especialização dos produtores e o encarecimento dos alimentos, como consequência de exigências burocráticas e sanitárias, além da perda de características artesanais dos alimentos em virtude dos padrões de qualidade industriais impostos pela legislação. Destacase, assim, a necessidade de discussão sobre os padrões de qualidade dos alimentos vigentes no Brasil no que tange a produção artesanal de alimentos como forma de valorizar e preservar saberes e práticas conectadas. Compreende-se que a discussão brasileira não deve centrar-se na busca pela reconexão ou relocalização como na Europa, mas na valorização dos produtos alimentares e das relações de produção e consumo existentes, permitindo, assim, a reprodução de alimentos e de meios de vida rurais. 149 - 169 rafaela.vendruscolo@iffarroupilha.edu.br fabianathomedacruz@gmail.com Schneider, Sérgio Semestral