Open Field Lines Research Articles

Magnetospheric Curvature Radiation by Bunches as Emission Mechanism for Repeating Fast Radio Bursts

Abstract Coherent curvature radiation as the radiation mechanism for fast radio bursts (FRBs) has been discussed since FRBs were discovered. We study the spectral and polarization properties of repeating FRBs within the framework of coherent curvature radiation by charged bunches in the magnetosphere of a highly magnetized neutron star. The spectra can be generally characterized by multisegmented broken power laws, and evolve as bunches move and the line of sight sweeps. Emitted waves are highly linear polarized and polarization angles are flat across the burst envelopes, if the line of sight is confined to the beam within an angle of 1/γ, while a circular polarization fraction becomes strong for off-beam cases. The spectro-temporal pulse-to-pulse properties can be a natural consequence due to the magnetospheric geometry. We investigate the relationship between drift rate, central frequency, and temporal duration. The radius-to-frequency mapping is derived and simulated within the assumptions of both dipolar and quadrupolar magnetic configurations. The geometric results show that FRBs are emitted in field lines more curved than open field lines for a dipolar geometry. This suggests that there are most likely existing multipolar magnetic configurations in the emission region.

Discrete Aurora on the Nightside of Mars: Occurrence Location and Probability

AbstractThis paper represents the first attempt to predict the occurrence location and probability of discrete electron aurora on the nightside of Mars. We run a 3‐D time‐dependent magnetohydrodynamic model to characterize the spatial and temporal dynamics of magnetic field and plasma distributions over the course of one planetary rotation. We perform eight simulation cases under solar minimum quiet‐solar‐wind conditions (four equinox/solstice seasons, each with two interplanetary magnetic field polarities) and in an actual interplanetary coronal mass ejection (ICME) case to assess quiet and space weather situations, respectively. The occurrence of detectable discrete aurora is subject to the combination of the probabilities that (a) the ionosphere is magnetically connected with high altitudes through open field lines and (b) precipitating energy fluxes of >30 eV electrons exceed 0.1 erg/cm2/s. Our results show that during quiet solar activity, discrete aurora occurs likely on small‐scale patches embedded inside strong crustal magnetic field regions (with a magnitude greater than 50 nT at 150 km), and the overall chance across the globe is ∼0.77%. The higher probability over strong crustal field regions is attributed to the stronger magnetic field convergence. Modeling shows the occurrence probability dramatically increases during the ICME event, particularly by more than an order of magnitude in weak crustal field regions. Our model results reasonably agree with NASA Mars Atmosphere and Volatile EvolutioN and Mars Express observations. Our study suggests that nightside discrete electron aurora is not caused by the direct entry of magnetosheath plasma in a cusp‐like process but due to the recycling of nightside magnetospheric electrons.

Homologous Accelerated Electron Beams, a Quasiperiodic Fast-propagating Wave, and a Coronal Mass Ejection Observed in One Fan-spine Jet

Abstract Using imaging and radio multi-wavelength observations, we studied the origin of two homologous accelerated electron beams and a quasiperiodic fast-propagating (QFP) wave train associated with a solar jet on 2012 July 14. The jet occurred in a small-scale fan-spine magnetic system embedded in a large-scale pseudostreamer associated with a GOES C1.4 flare, a jet-like coronal mass ejection (CME), a type II radio burst, and a type III radio burst. During the initial stage, a QFP wave train and a fast-moving on-disk radio source were detected in succession ahead of the jet along the outer spine of the fan-spine system. When the jet reached a height of about 1.3 solar radii, it underwent a bifurcation into two branches. Based on our analysis results, all the observed phenomena in association with the jet can be explained by using a fan-spine magnetic system. We propose that both the type III radio burst and the on-disk fast-moving radio source were caused by the same physical process, i.e., energetic electrons accelerated by magnetic reconnection at the null point, and these energetic electrons were propagating along the open field lines of the pseudostreamer and the closed outer spine of the fan-spine structure, respectively. Due to the bifurcation of the jet body, the lower branch along the closed outer spine of the fan-spine structure fell back to the solar surface, while the upper branch along the open field lines of the pseudostreamer caused the jet-like CME in the outer corona.

Intermittent structures and quasi-stationary equilibrium in a simple magnetized torus in open field line configuration

A steady regime dominated by intermittent blob and hole structures is identified in the plasma state of a simple magnetized torus by achieving a quasi-stationary equilibrium using an open magnetic field line configuration. The open helical field line configuration is characterized by a connection length, cm, and pitch ratio, This is realized by superposing a vertical magnetic fied, to the toroidal field, and the regime is achieved for mT. The combined effect of plasma rotation, arising from a substantial radial electric field, together with an open field line, results in vertically elongated plasma profile and an asymmetric sheared poloidal flow. The analysis shows the existence of density fluctuations exhibiting universal statistical properties, dominated by non-Gaussian blob events in the edge region and holes in the core plasma, separated by a region ascribed as blob birth zone corresponding to a velocity shear layer. Two-dimensional conditional averaging analyses of fluctuations indicate that blobs form in the sheared layer, when the leading edge of an elongated coherent structure breaks off by differential stretching exerted by the background fluctuating field. Convection of this isolated blob out of the contour corresponding to the maximum radial electric field in the low field side, leads to its ejection while holes move along the same contour driven back into the main plasma. The corresponding potential structure shows counter-rotating velocity field within oppositely charged structures, where the embedded electric field is consistent with the observed structure propagation. A comparison with cross-correlation analysis yields a similar conclusion except for a slight overestimation of the structure size and lifetime.

A statistical study of polar cap flow channels observed in both hemispheres using SuperDARN radars

This paper details the first large-scale, interhemispheric statistical study into ionospheric fast flow (>900 m/s) channels in the polar cap using the SuperDARN radar network. An automatic algorithm was applied to 6 years of data (2010–2016) from 8 SuperDARN radars with coverage in the polar cap regions in both hemispheres. Over 17,000 flow channels were detected, the majority of which occurred in the dayside polar cap region. To determine a statistical relationship between the flow channels and the IMF, a Monte Carlo simulation was used to generate probability distribution functions for IMF conditions and dipole tilt angles. These were used as a baseline for comparisons with IMF conditions associated with the flow channels. This analysis showed that fast flow channels are preferentially driven by IMF By dominant conditions, suggesting that a magnetic tension force on the newly reconnected field lines is required to accelerate the ionospheric plasma to high speeds on the dayside. The flow channels also occur preferentially during disturbed IMF conditions. Large populations of flow channels were observed on the flanks of the polar cap region. This indicates that significant momentum transfer from the magnetosphere can routinely occur on open field lines on the flanks, far from the dayside and nightside reconnection regions.

Secondary Magnetic Reconnection at Earth’s Flank Magnetopause

We report local secondary magnetic reconnection at Earth’s flank magnetopause by using the Magnetospheric Multiscale observations. This reconnection is found at the magnetopause boundary with a large magnetic shear between closed magnetospheric field lines and the open field lines generated by the primary magnetopause reconnection at large scales. Evidence of this secondary reconnection are presented, which include a secondary ion jet and the encounter of the electron diffusion region. Thus the observed secondary reconnection indicates a cross-scale process from a global scale to an electron scale. As the aurora brightening is also observed at the morning ionosphere, the present secondary reconnection suggests a new pathway for the entry of the solar wind into geospace, providing an important modification to the classic Dungey cycle.

MAVEN Observations of Periodic Low-altitude Plasma Clouds at Mars

Abstract Ion escape to space through the interaction of solar wind and Mars is an important factor influencing the evolution of the Martian atmosphere. The plasma clouds (explosive bulk plasma escape), considered an important ion escaping channel, have been recently identified by spacecraft observations. However, our knowledge about Martian plasma clouds is lacking. Based on the observations of the Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft, we study a sequence of periodic plasma clouds that occurred at low altitudes (∼600 km) on Mars. We find that the heavy ions in these clouds are energy-dispersed and have the same velocity, regardless of species. By tracing such energy-dispersed ions, we find the source of these clouds is located in a low-altitude ionosphere (∼120 km). The average tailward moving flux of ionospheric plasma carried by clouds is on the order of 107 cm−2 s−1, which is one order higher than the average escaping flux for the magnetotail, suggesting explosive ion escape via clouds. Based on the characteristics of clouds, we suggest, similar to the outflow of Earth’s cusp, these clouds might be the product of heating due to solar wind precipitation along the open field lines, which were generated by magnetic reconnection between the interplanetary magnetic field and crustal fields that occurred above the source.

Collisionless plasma transport mechanisms in stochastic open magnetic field lines in tokamaks

The collisionless plasma transport in stochastic magnetic fields connecting to wall boundary has been studied to understand the underlying mechanisms of thermal quench physics in tokamak disruption. In this study, we present a comprehensive understanding of the plasma dynamics in three-dimensional stochastic open magnetic field lines, taking into account the consistent coupling of electron and ion dynamics through the ambipolar electric field. The open stochastic field lines act as a 3D magnetic mirror consisting of the magnetic well and hill regions. It was found that the magnetic hill regions play a critical role in enhancing electron thermal transport. When the plasma collapses to the wall, the 3D ambipolar potential arises in the stochastic layer to maintain the quasi-neutrality of the plasma. The E × B vortices induced by the 3D ambipolar potential mix the plasma across stochastic field lines and enhance the radial transport. Particularly, the E × B mixing between the magnetic well and hill regions provides a collisionless detrapping mechanism that plays a major role in the loss of high-energy trapped electrons. As a result, the electron temperature steadily decreases at a rate of about −0.5 keV ms−1, comparable to the rate observed in thermal quench experiments.

Space weather study through analysis of solar radio bursts detected by a single-station CALLISTO spectrometer

Abstract. This article summarises the results of an analysis of solar radio bursts (SRBs) detected by the Compound Astronomical Low-cost Low-frequency Instrument for Spectroscopy and Transportable Observatory (CALLISTO) spectrometer hosted by the University of Rwanda. The data analysed were detected during the first year (2014–2015) of the instrument operation. Using quick plots provided by the e-CALLISTO website, a total of 201 intense and well-separated solar radio bursts detected by the CALLISTO station located in Rwanda, are found consisting of 4 type II, 175 type III and 22 type IV radio bursts. It is found that all analysed type II and ∼ 37 % of type III bursts are associated with impulsive solar flares, while the minority (∼ 13 %) of type IV radio bursts are associated with solar flares. Furthermore, all type II radio bursts are associated with coronal mass ejections (CMEs), ∼ 44 % of type III bursts are associated with CMEs, and the majority (∼ 82 %) of type IV bursts were accompanied by CMEs. With aid of the atmospheric imaging assembly (AIA) images on board the Solar Dynamics Observatory (SDO), the location of open magnetic field lines of non-flare-associated type III radio bursts are shown. The same images are used to show the magnetic loops in the solar corona for type IV radio bursts observed in the absence of solar flares and/or CMEs. Findings from this study indicate that analysis of SRBs that are observed from the ground can provide a significant contribution to the early diagnosis of solar transients phenomena, such as solar flares and CMEs, which are major drivers of potential space weather hazards.

The effects of magnetic fields on observational signatures of atmospheric escape in exoplanets: Double tail structures

ABSTRACTUsing 3D radiative MHD simulations and Lyman-α transit calculations, we investigate the effect of magnetic fields on the observational signatures of atmospheric escape in exoplanets. Using the same stellar wind, we vary the planet’s dipole field strength (Bp) from 0 to 10G. For Bp < 3G, the structure of the escaping atmosphere begins to break away from a comet-like tail following the planet (Bp = 0), as we see more absorbing material above and below the orbital plane. For Bp ≥ 3G, we find a ‘dead-zone’ around the equator, where low velocity material is trapped in the closed magnetic field lines. The dead-zone separates two polar outflows where absorbing material escapes along open field lines, leading to a double tail structure, above and below the orbital plane. We demonstrate that atmospheric escape in magnetized planets occurs through polar outflows, as opposed to the predominantly night-side escape in non-magnetized models. We find a small increase in escape rate with Bp, though this should not affect the time-scale of atmospheric loss. As the size of the dead-zone increases with Bp, so does the line centre absorption in Lyman-α, as more low-velocity neutral hydrogen covers the stellar disc during transit. For Bp < 3G the absorption in the blue wing decreases, as the escaping atmosphere is less funnelled along the line of sight by the stellar wind. In the red wing (and for Bp > 3G in the blue wing) the absorption increases caused by the growing volume of the magnetosphere. Finally we show that transits below and above the mid-disc differ caused by the asymmetry of the double tail structure.

Frequency-resolved radio and high-energy emission of pulsars

Context. Pulsars are detected as broadband electromagnetic emitters from the radio wavelength up to high and very high energy in the MeV, the GeV and sometimes even in the TeV range. Multiwavelength phase-resolved spectra and light curves offer an unrivaled opportunity to understand their underlying radiation mechanisms and to localize their emission sites and therefore the particle acceleration regions. Aims. In this paper we compute pulsar multiwavelength phase-resolved light curves and spectra, assuming that both curvature and synchrotron radiation operate from inside the magnetosphere of a rotating vacuum magnet. Radio emission arises from dipolar regions above the polar caps, whereas gamma-ray energy emanates from the slot gaps in the vicinity of the separatrix between closed and open field lines. Methods. By integrating particle trajectories within the slot gaps, we compute energy-dependent photon sky maps in the radio band (MHz−GHz) and in the gamma-ray band (from MeV to GeV) for mono-energetic distribution functions of leptons. Results. We obtained many details of the energy-dependent light curves and phase-resolved spectra from the radio wavelength up to the gamma-ray energies. Choosing Lorentz factors of γ ≈ 30 for the secondary plasma responsible for the radio emitting particles and γ ≈ 107 for the primary beam producing gamma-ray-emitting particles limited by radiation reaction, we found realistic spectra that account for the wealth of multiwavelength pulsar observations.

Fifty Years of 3He-Rich Events

The early 1970s saw a new and surprising feature in the composition of solar energetic particles (SEPs), resonant enhancements up to 10,000-fold in the ratio 3He/4He that could even make 3He dominant over H in rare events. It was soon learned that these events also had enhancements in the abundances of heavier elements, such as a factor of ∼10 enhancements in Fe/O, which was later seen to be part of a smooth increase in enhancements vs. mass-to-charge ratio A/Q from H to Pb, rising by a factor of ∼1000. These events were also associated with streaming 10–100 keV electrons that produce type III radio bursts. In recent years we have found these “impulsive” SEP events to be accelerated in islands of magnetic reconnection from plasma temperatures of 2–3 MK on open field lines in solar jets. Similar reconnection on closed loops traps the energy of the particles to produce hot (>10 MK), bright flares. Sometimes impulsive SEP intensities are boosted by shock waves when the jets launch fast coronal mass ejections. No single theory yet explains both the sharp resonance in 3He and the smooth increase up to heavier elements; two processes seem to occur. Sometimes the efficient acceleration even exhausts the rare 3He in the source region, limiting its fluence.

TRICE 2 Observations of Low‐Energy Magnetospheric Ions Within the Cusp

AbstractOn December 08, 2018 the Twin Rocket Investigation of Cusp Electrodynamics 2 (TRICE 2) mission was successfully launched. The mission consisted of two sounding rockets, each carrying a payload capable of measuring electron and ion distributions, electric and magnetic fields, and plasma waves occurring in the northern magnetospheric cusp. This study highlights the ion and wave observations obtained by TRICE 2 in the cusp and observations from the magnetospheric multiscale (MMS) spacecraft at the low‐latitude magnetopause two hours prior to the TRICE 2 traversal of the cusp. Within the cusp, typical ion cusp features were observed, that is, energy‐latitude dispersion of injected magnetosheath plasma. However, a lower energy population was also measured near the equatorward edge of the cusp on open field lines. Pitch‐angle distributions of the low‐energy ions suggest that this population was magnetospheric in origin, and not from ionospheric upflows. Data from MMS show that counterstreaming ions were present in the outer magnetosphere and low‐latitude boundary layer at similar energies to those observed by TRICE 2 in the cusp. Correlations between the low‐energy ions within the cusp and broadband extremely low frequency waves suggest that the low‐energy magnetospheric ions that filled the flux tube may have undergone wave‐particle interactions. These interactions may cause pitch‐angle scattering of low‐energy magnetospheric ions closer to the loss cone, thereby allowing them to precipitate into the cusp and be measured by the TRICE 2 sounding rockets.

Magnetic Reconnection Within the Boundary Layer of a Magnetic Cloud in the Solar Wind

AbstractThe twisted local magnetic field at the front or rear regions of the magnetic clouds (MCs) associated with interplanetary coronal mass ejections (ICMEs) is often nearly opposite to the direction of the ambient interplanetary magnetic field. There is also observational evidence for magnetic reconnection (MR) outflows occurring within the boundary layers of MCs. In this study, a MR event located at the western flank of the MC occurring on October 3, 2000 is studied in detail. Both the large‐scale geometry of the helical MC and the MR outflow structure are scrutinized in a detailed multipoint study. The ICME sheath is of hybrid propagation‐expansion type. Here, the freshly reconnected open field lines are expected to slip slowly over the MC resulting in plasma mixing at the same time. As for MR, the current sheet geometry and the vertical motion of the outflow channel between ACE‐Geotail‐WIND spacecraft were carefully studied and tested. The main findings on MR include (a) first‐time observation of non‐Petschek‐type slow‐shock‐like discontinuities in the inflow regions; (b) observation of turbulent Hall magnetic field associated with a Lorentz‐force‐deflected electron jet; (c) acceleration of protons by reconnection electric field and their back‐scatter from the slow‐shock‐like discontinuity; (d) observation of relativistic electron near the MC inflow boundary/separatrix; these electron populations can presumably appear as a result of nonadiabatic acceleration, gradient B drift, and via acceleration in the electrostatic potential well associated with the Hall current system; and (e) observation of Doppler‐shifted ion‐acoustic and Langmuir waves in the MC inflow region.

Exoplanet in the triple star system as the probable source of effective cyclotron emission

Interaction of exoplanet with a host star in the triple star system is considered. Besides reconnection of the stellar and planetary magnetic fields (if they exist), the specific interaction of exoplanet with three stars leads to increased impact on the planetary environment and the host star astrosphere. Encounters with different kinds of corotation interaction regions from the stellar winds of the distant stars in the triple system affect the host-star's astrosphere. Just out of the astrosphere's boundary, dynamo can act for the rapidly rotating magnetic host star, because corotation, transferred along open field lines, brakes down there with possible generation of magnetic field. When several stars exist in the system, the effect of their CMEs and flare activities can summarize. Rotational synchronization between the host star and close-in exoplanet can intensify the coronal activity of the star. All these effects could lead to possible increase of magnetic field at the boundary of the host star astrosphere and inside it, which, consequently, will result in the enhanced cyclotron radio emission from such systems.

The Evolution of Research on Abundances of Solar Energetic Particles

Sixty years of study of energetic particle abundances have made a major contribution to our understanding of the physics of solar energetic particles (SEPs) or solar cosmic rays. An early surprise was the observation in small SEP events of huge enhancements in the isotope 3He from resonant wave–particle interactions, and the subsequent observation of accompanying enhancements of heavy ions, later found to increase 1000-fold as a steep power of the mass-to-charge ratio A/Q, right across the elements from H to Pb. These “impulsive” SEP events have been related to magnetic reconnection on open field lines in solar jets; similar processes occur on closed loops in flares, but those SEPs are trapped and dissipate their energy in heat and light. After early controversy, it was established that particles in the large “gradual” SEP events are accelerated at shock waves driven by wide, fast coronal mass ejections (CMEs) that expand broadly. On average, gradual SEP events give us a measure of element abundances in the solar corona, which differ from those in the photosphere as a classic function of the first ionization potential (FIP) of the elements, distinguishing ions and neutrals. Departures from the average in gradual SEPs are also power laws in A/Q, and fits of this dependence can determine Q values and thus estimate source plasma temperatures. Complications arise when shock waves reaccelerate residual ions from the impulsive events, but excess protons and the extent of abundance variations help to resolve these processes. Yet, specific questions about SEP abundances remain.

First Frequency-time-resolved Imaging Spectroscopy Observations of Solar Radio Spikes

Abstract Solar radio spikes are short duration and narrow bandwidth fine structures in dynamic spectra observed from the GHz to tens of MHz range. Their very short duration and narrow frequency bandwidth are indicative of subsecond small-scale energy release in the solar corona, yet their origin is not understood. Using the LOw Frequency ARray, we present spatially, frequency, and time resolved observations of individual radio spikes associated with a coronal mass ejection. Individual radio spike imaging demonstrates that the observed area is increasing in time and the centroid positions of the individual spikes move superluminally parallel to the solar limb. Comparison of spike characteristics with that of individual Type IIIb striae observed in the same event show similarities in duration, bandwidth, drift rate, polarization, and observed area, as well the spike and striae motion in the image plane suggesting fundamental plasma emission with the spike emission region on the order of ∼108 cm, with brightness temperature as high as 1013 K. The observed spatial, spectral, and temporal properties of the individual spike bursts are also suggestive of the radiation responsible for spikes escaping through anisotropic density turbulence in closed loop structures with scattering preferentially along the guiding magnetic field oriented parallel to the limb in the scattering region. The dominance of scattering on the observed time profile suggests the energy release time is likely to be shorter than what is often assumed. The observations also imply that the density turbulence anisotropy along closed magnetic field lines is higher than along open field lines.

Test Particle Model Predictions of SEP Electron Transport and Precipitation at Mars

AbstractExtreme space weather events can episodically release solar energetic particles (SEPs) that precipitate into planetary atmospheres, leading to aurora and increased ionization. While the induced magnetosphere of Mars does not substantially obstruct SEP protons, the effect on SEP electrons is not known. We use a test particle model modified for relativistic electrons to model transport of 10–200 keV electrons from outside the bow shock and deep in the magnetotail of Mars. We find a substantial influence of curvature and gradient drifts on precipitation, leading to depletions in the bow shock and transport onto closed field lines. The model estimates ∼3% of incident flux precipitates into the Mars atmosphere for a typical SEP event under nominal solar wind conditions, exceeding the estimate from the guiding center path approximation without drift terms. Precipitation is globally patchy. The model estimates 55% of electrons precipitating into cusps along open field lines and 45% precipitating on closed field lines, suggesting drift and nonadiabatic transport mechanisms have a significant influence on precipitation. We also predict that the fraction of precipitating differential flux increases as a function of energy. We discuss how these predictions would be affected by disturbed conditions that tend to accompany the arrival of SEPs and by differing SEP electron spectra hardness and anisotropy. We finally discuss how the simulation predictions compare to observations of diffuse aurora.

The effect of rigid electron rotation on the Grad–Shafranov equilibria of a class of FRC devices

Rigid electron rotation of a Rotamak-FRC produces a pressure flux function that is more peaked than the Solov’ev flux function. This paper explores the implications of this peaked pressure flux function, including the isothermal case, which appear when the temperature profile is broader than the density profile, creating both benefits and challenges to a Rotamak-FRC based fusion reactor. In this regime, the density distribution becomes very peaked, enhancing the fusion power. The separatrix has a tendency to become oblate, which can be mitigated by flux conserving current loops. Plasma extends outside the separatrix, notably in the open field line region. This model does not apply to very kinetic FRCs or FRCs in which there are significant ion flows, but it may have some applicability to their outer layers.

Comparison of active region upflow and core properties using simultaneous spectroscopic observations from IRIS and Hinode

Context. The origin of the slow solar wind is still an open issue. It has been suggested that upflows at the edge of active regions are a possible source of the plasma outflow and therefore contribute to the slow solar wind. Aims. We investigate the origin and morphology of the upflow regions and compare the upflow region and the active region core properties. Methods. We studied how the plasma properties of flux, Doppler velocity, and non-thermal velocity change throughout the solar atmosphere, from the chromosphere via the transition region to the corona in the upflow region and the core of an active region. We studied limb-to-limb observations of the active region (NOAA 12687) obtained from 14 to 25 November 2017. We analysed spectroscopic data simultaneously obtained from IRIS and Hinode/EIS in the six emission lines Mg II 2796.4Å, C II 1335.71Å, Si IV 1393.76Å, Fe XII 195.12Å, Fe XIII 202.04Å, and Fe XIV 270.52Å and 274.20Å. We studied the mutual relationships between the plasma properties for each emission line, and we compared the plasma properties between the neighbouring formation temperature lines. To find the most characteristic spectra, we classified the spectra in each wavelength using the machine learning technique k-means. Results. We find that in the upflow region the Doppler velocities of the coronal lines are strongly correlated, but the transition region and coronal lines show no correlation. However, their fluxes are strongly correlated. The upflow region has a lower density and lower temperature than the active region core. In the upflow region, the Doppler velocity and non-thermal velocity show a strong correlation in the coronal lines, but the correlation is not seen in the active region core. At the boundary between the upflow region and the active region core, the upflow region shows an increase in the coronal non-thermal velocity, the emission obtained from the DEM, and the domination of the redshifted regions in the chromosphere. Conclusions. The obtained results suggest that at least three parallel mechanisms generate the plasma upflow: (1) The reconnection between closed loops and open magnetic field lines in the lower corona or upper chromosphere; (2) the reconnection between the chromospheric small-scale loops and open magnetic field; and (3) the expansion of the magnetic field lines that allows the chromospheric plasma to escape to the solar corona.