Understanding how energetic particles are accelerated and released from the low corona into the interplanetary medium during solar eruptions is crucial for space weather research. Here, we present multiwavelength observations of a solar eruption that are consistent with breakout reconnection playing an important role in driving a fast coronal mass ejection (CME) and the associated solar energetic particle (SEP) event. Extreme-ultraviolet and radio observations reveal evidence of breakout reconnection within a fan-spine topology. The filament eruption begins after the pre-eruption opening, accompanied by quasiperiodic jets and associated downflows near the null point, as well as recurrent faint Type III radio bursts during the ongoing slow breakout reconnection. Furthermore, the observations also reveal the formation of pre-eruption coronal rain via slow interchange reconnection near the null point. A large-scale circular ribbon, along with simultaneous four hard X-ray footpoint sources and intense Type III radio bursts, was observed during the explosive breakout reconnection that enabled opening of field lines and allowed energetic particles to escape into interplanetary space. In situ measurements by PSP and Wind confirm the prompt injection of electron beams consistent with the timing of the explosive breakout reconnection. A fast shock associated with the erupting flux rope during interchange reconnection played a major role in producing the gradual SEP event. These observations highlight the key role of breakout reconnection in producing a fast CME/shock with the SEP release and acceleration process. These results have broader implications for particle acceleration and release processes in multiscale null-point topologies, which produce a continuum of eruptions ranging from small-scale jets to large-scale CMEs.

This study investigates how magnetic reconnection reshapes coronal-hole (CH) boundaries during eruptive events. Using high-cadence EUV and magnetogram observations from the Solar Dynamics Observatory on 2015 June 4, we apply correlation dimension mapping (CDM), a technique designed to quantify the geometric complexity of CH boundaries across multiple spatial scales. We find that localized jet eruptions are systematically accompanied by rapid increases in the correlation dimension, indicating enhanced boundary irregularity during magnetic reconfiguration. Two of the three detected events correspond to coronal jets occurring within a multipolar magnetic configuration characterized by a polarity inversion line and a fan–spine topology favorable for reconnection. In both cases, the peak in boundary complexity occurs shortly after the jet’s intensity maximum, suggesting a delayed response of the large-scale magnetic structure to localized reconnection. These results demonstrate that CDM provides a sensitive diagnostic of dynamic restructuring at CH boundaries. The method offers a new way to track the geometric response of open–closed magnetic interfaces during eruptive activity and may help identify geometric signatures associated with reconnection-driven events in the solar corona.

A systematic study of nuclear shape transitions in even-even 280−314Fl isotopes is performed within the framework of the relativistic Hartree-Bogoliubov (RHB) model using the density-dependent point-coupling (DD-PC1) interaction. Triaxially constrained calculations are carried out to explore the potential energy surfaces in this isotopic chain. The incorporation of γ degree of freedom plays an important role in determining the ground-state configurations. A significant prolate deformation is observed in this isotopic chain, followed by a sudden prolate to oblate shape transition at N = 178. Furthermore, we predict prolate-oblate shape coexistence in 290Fl. To elucidate the origin of deformation, the single-particle shell structure for these superheavy nuclei is also examined. Other ground-state properties such as two-neutron separation energies (S2n) and α-decay energies (Qα) are also calculated for 280−314Fl isotopes and compared with other theoretical models as well as available experimental data. Moreover, the single-particle energy spectrum is studied to examine the shell structure of 298Fl. The calculated ground-state properties, shell structure, and microscopic observables provide evidence consistent with a spherical doubly magic character of 298Fl.

Plasmoids (or magnetic islands) are believed to play an important role in the onset of fast magnetic reconnection and particle acceleration during solar flares and eruptions. Direct imaging of flare current sheets and the formation/ejection of multiple plasmoids in extreme-ultraviolet images, along with simultaneous X-ray and radio observations, offers significant insights into the mechanisms driving particle acceleration in solar flares. Here, we present direct imaging of the formation and ejection of multiple plasmoids in flare plasma/current sheets and the associated quasiperiodic pulsations (QPPs) observed at X-ray and radio wavelengths, using observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly, RHESSI, and the Fermi Gamma-ray Burst Monitor. These plasmoids propagate bidirectionally upward and downward along the flare current sheet beneath the erupting flux rope during two successive flares associated with confined/failed eruptions. The flux rope exhibits evidence of helical kink instability, with the formation and ejection of multiple plasmoids in the flare current sheet, as predicted in an MHD simulation of a kink-unstable flux rope. RHESSI X-ray images show double coronal sources (“looptop” and higher coronal sources) located at both ends of the flare current/plasma sheet. Moreover, we detect an additional transient faint X-ray source (6–12 keV) located between the double coronal sources, which is cospatial with multiple plasmoids in the flare current sheet. X-ray (soft and hard) and radio (decimetric) observations unveil QPPs (periods ≈ 10 s and 100 s) associated with the ejection and coalescence of plasmoids. These observations suggest that energetic electrons are accelerated during the ejection and coalescence of multiple plasmoids in the flare current sheet.

Understanding how shocks interact with coronal structures is crucial for understanding the mechanisms of particle acceleration in the solar corona and inner heliosphere. Using simultaneous radio and white-light observations, we investigate the interaction between a coronal mass ejection (CME)-driven shock and a plasmoid. LASCO and STEREO-A COR-2 white-light images are analyzed to track the evolution of the plasmoid, CME, and its associated shock, while the Wind/WAVES and STEREO/WAVES dynamic spectra provide complementary radio signatures of the shock–plasmoid interaction at ≈7 R _⊙ . An interplanetary type II radio burst was detected as the shock propagated through the plasmoid. The merging of the plasmoid into the CME was accompanied by interplanetary type III radio bursts, suggesting escaping electron beams during the reconnection process. These observations clearly demonstrate that shock–plasmoid interactions can enhance the efficiency of particle acceleration associated with CMEs, with implications for electron acceleration in flare and heliospheric current sheets as well.

The magnetic breakout model explains a variety of solar eruptions, ranging from small-scale jets to large-scale coronal mass ejections (CMEs). Most of our previous studies are focused on jets and CMEs in single null-point topologies. Here, we investigate the initiation of CMEs and associated particle acceleration in a double null-point (or nested fan-spine) topology during multiple homologous M- and X-class flares from an active region. The initiation of the flare and associated eruption begins with inflow structures moving toward the inner null of the closed fan-spine topology. Simultaneous slow flare reconnection below a small filament formed a hot flux rope along with expansion of the overlying flux during slow breakout reconnection at the inner null. The first explosive breakout reconnection of the flux rope at the inner null produced a circular and a remote ribbon along with successful eruption of the flux rope and associated fast EUV (shock) wave. Simultaneous flare reconnection beneath the erupting flux rope produced a typical two-ribbon flare along with two hard X-ray footpoint sources. When the flux rope (with shock) reaches the outer null, a second explosive breakout reconnection produces another large-scale remote ribbon. The radio observations reveal quasiperiodic Type III bursts (period = 100 s) and a Type II burst during the breakout reconnection near the inner and outer nulls, along with gradual solar energetic particles observed at 1 au for magnetically connected events. This study highlight the importance of two successive breakout reconnections in the initiation of CMEs in nested-null topologies and associated particle acceleration and release into the interplanetary medium. The particles are accelerated by the shock ahead of the flux rope, which formed during the inner breakout reconnection. These findings have significant implications for particle acceleration and escape processes in multiscale null-point topologies that produce jets and CMEs.

We investigate the effects of nuclear matter incompressibility on the equation of state of asymmetric nuclear dense matter, different nuclear matter parameters, and neutron star properties. To aim this, we consider six different interactions for the energy density functional in the relativistic mean field (RMF) model, where the incompressibility K varies from 200 to 300 MeV. The equations of state for β - equilibrated matter have been calculated for these functionals and confronted the predicted neutron star properties with various astrophysical observations. The central values of the linear density dependence of symmetry energy (L), neutron star radius ( R 1.4 ), and dimensionless tidal deformability (Λ 1.4 ) for a 1.4 M ⊙ neutron star exhibit a good correlation with incompressibility. A statistical analysis has also been performed to estimate the theoretical uncertainties on model parameters and related nuclear and neutron star observables.

Magnetic reconnection is widely believed to be the fundamental process in the solar atmosphere that underlies magnetic energy release and particle acceleration. This process is responsible for the onset of solar flares, coronal mass ejections, and other explosive events (e.g., jets). Here, we report direct imaging of a prolonged plasma/current sheet along with quasiperiodic magnetic reconnection in the solar corona using ultra-high-resolution observations from the 1.6 m Goode Solar Telescope at the Big Bear Solar Observatory and the Solar Dynamics Observatory/Atmospheric Imaging Assembly. The current sheet appeared near a null point in the fan-spine topology and persisted over an extended period (approximate to 20 hr). The length and apparent width of the current sheet were about 6 '' and 2 '', respectively, and the plasma temperature was approximate to 10-20 MK. We observed quasiperiodic plasma inflows and outflows (bidirectional jets with plasmoids) at the reconnection site/current sheet. Furthermore, quasiperiodic reconnection at the long-lasting current sheet produced recurrent eruptions (small flares and jets) and contributed significantly to the recurrent impulsive heating of the active region. Direct imaging of a plasma/current sheet and recurrent null-point reconnection for such an extended period has not been reported previously. These unprecedented observations provide compelling evidence that supports the universal model for solar eruptions (i.e., the breakout model) and have implications for impulsive heating of active regions by recurrent reconnection near null points. The prolonged and sustained reconnection for about 20 hr at the breakout current sheet provides new insights into the dynamics and energy release processes in the solar corona.

The magnetic topology of erupting regions on the Sun is a key factor in the energy buildup and release, and the subsequent evolution of flares and coronal mass ejections (CMEs). The presence/absence of null points and separatrices dictates whether and where current sheets form and magnetic reconnection occurs. Numerical simulations show that energy buildup and release via reconnection in the simplest configuration with a null, the embedded bipole, is a universal mechanism for solar eruptions. Here we demonstrate that a magnetic topology with nested bipoles and two nulls can account for more complex dynamics, such as failed eruptions and CME–jet interactions. We investigate the stalled eruption of a nested configuration on 2013 July 13 in NOAA Active Region 11791, in which a small bipole is embedded within a large transequatorial pseudo-streamer containing a null. In the studied event, the inner active region erupted, ejecting a small flux rope behind a shock accompanied by a flare; the flux rope then reconnected with pseudo-streamer flux and, rather than escaping intact, mainly distorted the pseudo-streamer null into a current sheet. EUV and coronagraph images revealed a weak shock and a faint collimated outflow from the pseudo-streamer. We analyzed Solar Dynamics Observatory and Solar TErrestrial RElations Observatory observations and compared the inferred magnetic evolution and dynamics with three-dimensional magnetohydrodynamics simulations of a simplified representation of this nested fan-spine system. The results suggest that the difference between breakout reconnection at the inner null and at the outer null naturally accounts for the observed weak jet and stalled ejection. We discuss the general implications of our results for failed eruptions.

Coronal mass ejections (CMEs) from pseudostreamers represent a significant fraction of large-scale eruptions from the Sun. In some cases, these CMEs take a narrow jet-like form reminiscent of coronal jets; in others, they have a much broader fan-shaped morphology like CMEs from helmet streamers. We present results from a magnetohydrodynamic simulation of a broad pseudostreamer CME. The early evolution of the eruption is initiated through a combination of breakout interchange reconnection at the overlying null point and ideal instability of the flux rope that forms within the pseudostreamer. This stage is characterized by a rolling motion and deflection of the flux rope toward the breakout current layer. The stretching out of the strapping field forms a flare current sheet below the flux rope; reconnection onset there forms low-lying flare arcade loops and the two-ribbon flare footprint. Once the CME flux rope breaches the rising breakout current layer, interchange reconnection with the external open field disconnects one leg from the Sun. This induces a whip-like rotation of the flux rope, generating the unstructured fan shape characteristic of pseudostreamer CMEs. Interchange reconnection behind the CME releases torsional Alfv & eacute;n waves and bursty dense outflows into the solar wind. Our results demonstrate that pseudostreamer CMEs follow the same overall magnetic evolution as coronal jets, although they present different morphologies of their ejecta. We conclude that pseudostreamer CMEs should be considered a class of eruptions that are distinct from helmet-streamer CMEs, in agreement with previous observational studies.

We analyzed Interface-Region Imaging Spectrograph (IRIS) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations of a small coronal jet that occurred at the solar west limb on 29 August 2014. The jet source region, a small bright point, was located at an active-region periphery and contained a fan-spine topology with a mini-filament. Our analysis has identified key features and timings that motivated the following interpretation of this event. As the stressed core flux rises, a current sheet forms beneath it; the ensuing reconnection forms a flux rope above a flare arcade. When the rising filament-carrying flux rope reaches the stressed null, it triggers a jet via explosive interchange (breakout) reconnection. During the flux-rope interaction with the external magnetic field, we observed brightening above the filament and within the dome, along with a growing flare arcade. EUV images reveal quasi-periodic ejections throughout the jet duration with a dominant period of 4 minutes, similar to coronal jetlets and larger jets. We conclude that these observations are consistent with the magnetic breakout model for coronal jets.

Mutual conversion of various kinds of magnetohydrodynamic (MHD) waves can have profound impacts on wave propagation, energy transfer, and heating of the solar chromosphere and corona. Mode conversion occurs when an MHD wave travels through a region where the Alfvén and sound speeds are equal (e.g., a 3D magnetic null point). Here we report the direct extreme ultraviolet (EUV) imaging of mode conversion from a fast-mode to a slow-mode MHD wave near a 3D null point using Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) observations. An incident fast EUV wavefront associated with an adjacent eruptive flare propagates laterally through a neighboring pseudostreamer. Shortly after the passage of the fast EUV wave through the null point, a slow-mode wave appears near the null that propagates upward along the open structures and simultaneously downward along the separatrix encompassing the fan loops of the pseudostreamer base. These observations suggest the existence of mode conversion near 3D nulls in the solar corona, as predicted by theory and MHD simulations. Moreover, we observe decaying transverse oscillations in both the open and closed structures of the pseudostreamer, along with quasiperiodic type III radio bursts indicative of repetitive episodes of electron acceleration.

We present results of a quantitative analysis of structured plasma outflows above a polar coronal hole observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO) spacecraft. In a 6 hr interval of continuous high-cadence SDO/AIA images, we identified more than 2300 episodes of small-scale plasma flows in the polar corona. The mean upward flow speed measured by the surfing transform technique is estimated to be 122 ± 34 km s ^−1 , which is comparable to the local sound speed. The typical recurrence period of the flow episodes is 10–30 minutes, and the mean duration and transverse size of each episode are about 3–5 minutes and 3–4 Mm, respectively. The largest identifiable episodes last for tens of minutes and reach widths up to 40 Mm. For the first time, we demonstrate that the polar coronal-hole outflows obey a family of power-law probability distributions characteristic of impulsive interchange magnetic reconnection. Turbulent photospheric driving may play a crucial role in releasing magnetically confined plasma onto open field. The estimated occurrence rate of the detected self-similar coronal outflows is sufficient for them to make a dominant contribution to the fast-wind mass and energy fluxes and to account for the wind’s small-scale structure.

The middle corona, the region roughly spanning heliocentric distances from 1.5 to 6 solar radii, encompasses almost all of the influential physical transitions and processes that govern the behavior of coronal outflow into the heliosphere. The solar wind, eruptions, and flows pass through the region, and they are shaped by it. Importantly, the region also modulates inflow from above that can drive dynamic changes at lower heights in the inner corona. Consequently, the middle corona is essential for comprehensively connecting the corona to the heliosphere and for developing corresponding global models. Nonetheless, because it is challenging to observe, the region has been poorly studied by both major solar remote-sensing and in-situ missions and instruments, extending back to the Solar and Heliospheric Observatory (SOHO) era. Thanks to recent advances in instrumentation, observational processing techniques, and a realization of the importance of the region, interest in the middle corona has increased. Although the region cannot be intrinsically separated from other regions of the solar atmosphere, there has emerged a need to define the region in terms of its location and extension in the solar atmosphere, its composition, the physical transitions that it covers, and the underlying physics believed to shape the region. This article aims to define the middle corona, its physical characteristics, and give an overview of the processes that occur there.

Resolving 3D physics occurring on multiple spatial and temporal scales is difficult with spacecraft and computer simulations alone, but can be studied much more easily with laboratory plasma experiments.This white paper proposes increasing funding for both human and physical infrastructure development in laboratory plasma facilities, as well as educating early career scientists on how to better utilize laboratory experiments in their own research.

Plumes are bright structures in coronal holes extending from the solar surface into the corona and are considered as a possible source of the solar wind. Plumes are thought to be rooted in strong unipolar photospheric flux patches (network/plage region). The magnetic activities at the base of plumes may play a crucial role in producing outflows and propagating disturbances (PDs). However, the role of photospheric/chromospheric activities (e.g., jets/spicules) at the base of plumes and their connection to PDs is poorly understood. Using high-resolution observations of a plume taken on 2020 July 23 with the 1.6 m Goode Solar Telescope (GST), Interface Region Imaging Spectrograph (IRIS), and the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory, we analyzed chromospheric/transition region activities at the base of the plume and their connection to outflows/PDs in the plume. The GST Visible Imaging Spectrometer images reveal repetitive spicules with blueshifted emission (pseudo-Doppler maps) at the plume’s footpoint. In addition, the photospheric magnetograms provide evidence of mixed polarities at the base of the plume. The IRIS Mg ii k Dopplergrams show strong blueshifted emission (∼50 km s−1) and a high brightness temperature (Mg ii k2 line) at the footpoint of the plume. The long-period PDs (P ≈ 20–25 minutes) along the plume (AIA 171 Å) match the periodicity of spicules in the chromospheric images, suggesting a close connection between the spicules and the PDs. We suggest that the interchange reconnection between the closed and open flux of the coronal bright point at the plume’s footpoint is the most likely candidate to produce upflows and associated PDs along the plume.

We report a detailed analysis of a failed eruption and flare in active region 12018 on 2014 April 3 using multiwavelength observations from SDO/AIA, IRIS, STEREO, and Hinode/SOT. At least four jets were observed to emanate from the cusp of this small active region (large bright point) with a null-point topology during the two hours prior to the slow rise of a filament. During the filament slow rise multiple plasma blobs were seen, most likely formed in a null-point current sheet near the cusp. The subsequent filament eruption, which was outside the IRIS field of view, was accompanied by a flare but remained confined. During the explosive flare reconnection phase, additional blobs appeared repetitively and moved bidirectionally within the flaring region below the erupting filament. The filament kinked, rotated, and underwent leg-leg reconnection as it rose, yet it failed to produce a coronal mass ejection. Tiny jet-like features in the fan loops were detected during the filament slow-rise/pre-flare phase. We interpret them as signatures of reconnection between the ambient magnetic field and the plasmoids leaving the null-point sheet and streaming along the fan loops. We contrast our interpretation of these tiny jets, which occur within the large-scale context of a failed filament eruption, with the local nanoflare-heating scenario proposed by Antolin et al. (2021).

Microstreams are fluctuations in the solar wind speed and density associated with polarity-reversing folds in the magnetic field (also denoted switchbacks). Despite their long heritage, the origin of these microstreams/switchbacks remains poorly understood. For the first time, we investigated periodicities in microstreams during Parker Solar Probe (PSP) Encounter 10 to understand their origin. Our analysis was focused on the inbound corotation interval on 2021 November 19–21, while the spacecraft dove toward a small area within a coronal hole (CH). Solar Dynamics Observatory remote-sensing observations provide rich context for understanding the PSP in situ data. Extreme ultraviolet images from the Atmospheric Imaging Assembly reveal numerous recurrent jets occurring within the region that was magnetically connected to PSP during intervals that contained microstreams. The periods derived from the fluctuating radial velocities in the microstreams (approximately 3, 5, 10, and 20 minutes) are consistent with the periods measured in the emission intensity of the jetlets at the base of the CH plumes, as well as in larger coronal jets and in the plume fine structures. Helioseismic and Magnetic Imager magnetograms reveal the presence of myriad embedded bipoles, which are known sources of reconnection-driven jets on all scales. Simultaneous enhancements in the PSP proton flux and ionic ( ^3 He, ^4 He, Fe, O) composition during the microstreams further support the connection with jetlets and jets. In keeping with prior observational and numerical studies of impulsive coronal activity, we conclude that quasiperiodic jets generated by interchange/breakout reconnection at CH bright points and plume bases are the most likely sources of the microstreams/switchbacks observed in the solar wind.

Abstract The turbulence is one of the products of the magnetic reconnection process in the solar flare plasma. It intensely shifts the dynamics of the magnetic reconnection process and rapidly transfer energy that facilitates plasma heating by over 10 MK and particle energization. In this study, using results of Monte Carlo experiment through Euler-Maruyama approximation of stochastic Lagrangian models for inhomogeneous hydrodynamic turbulence, we present the velocity and dissipation (relaxation rate) characteristics of stochastic motions of particles (particles obeying Gaussian distribution) in the turbulence of the solar flare plasma. Monte Carlo experiment was performed for the turbulent kinetic energy of 10 30 erg, at a time scale of 10 sec and length scale of the order of full loop half-length 10 10 cm of the solar flare. The results of the velocity and dissipation (relaxation rate) are presented and analysed in both one and two dimensions. We observed that the positive value of relaxation rate of (1 − 8) × 10 −4 sec −1 for ≈ 5 sec of dispersion time could lead to the energy transfer and dissipation of the energy in the turbulence of the solar flare. The Monte Carlo mean relaxation rate of 4.5 × 10 −4 sec −1 shows that it dissipates ≈ 4.5 × 10 27 erg energy into thermal energy in 10 seconds, which is equal to the ≈ 0.5 % of the total injected kinetic energy. Velocities of the stochastic particles in the turbulence show the randomly fluctuations which are unsteadily dispersive in nature. The range and mean values of particles velocities are ∼ (0.5 − 3) × 10 6 cm sec −1 and 1.5 × 10 6 cm sec −1 respectively which indicate low atmospheric turbulence (chromosphere) in the solar flare. The turbulence onset at the loop top of the flare corona and propagate to lower chromosphere atmosphere of the flare. The obtained results are in the agreement with the observations. Our analysis thus demonstrates that the turbulence in the solar flare dissipate ≈ 0.5% of the injected energy into thermal energy. The rest of energy goes for the non-thermal particle energizing (particle acceleration).