Solar Physics最新文献

Sympathetic eruptions of solar prominences have been studied for decades, however, it is usually difficult to identify their causal links. Here, we present two failed prominence eruptions on 26 October 2022 and explore their connections. Using stereoscopic observations, the South prominence (PRO-S) erupts with untwisting motions, flare ribbons occur underneath, and new connections are formed during the eruption. The North prominence (PRO-N) rises up along with PRO-S, and its upper part disappears due to catastrophic mass draining along an elongated structure after PRO-S failed eruption. We suggest that the eruption of PRO-S initiates due to a kink instability, and fails to erupt due to reconnection with surrounding fields. The elongated structure connecting PRO-N overlies PRO-S, which causes the rising up of PRO-N along with PRO-S and mass drainage after PRO-S eruption. This study suggests that a prominence may end its life through mass drainage forced by an eruption underneath.

Filament eruptions often result in flares and coronal mass ejections (CMEs). Most studies attribute the filament eruptions to their instabilities or magnetic reconnection. In this study, we report a unique observation of a filament eruption whose initiation process has not been reported before. This large-scale filament, with a length of about 360 Mm crossing an active region, is forced to erupt by two small-scale erupting filaments pushing out from below. This process of multifilament eruption results in an M6.4 flare in the active region NOAA 13229 on 25 February 2023. The whole process can be divided into three stages: the eruptions of two active-region filaments, F1 and F2; the interactions between the erupting F1, F2, and the large-scale filament F3; and the eruption of F3. Though this multifilament eruption occurs near the northwest limb of the solar disk, it produces a strong halo CME that causes a significant geomagnetic disturbance. Our observations present a new filament eruption mechanism in which the initial kinetic energy of the eruption is obtained from and transported to by other erupting structures. This event provides us a unique insight into the dynamics of multifilament eruptions and their corresponding effects on the interplanetary space.

We present a new iterative rotation inversion technique based on the Simultaneous Algebraic Reconstruction Technique developed for image reconstruction. We describe in detail our algorithmic implementation and compare it to the classical inversion techniques like the Regularized Least Squares (RLS) and the Optimally Localized Averages (OLA) methods. In our implementation, we are able to estimate the formal uncertainty on the inferred solution using standard error propagation, and derive the averaging kernels without recourse to any Monte-Carlo simulation. We present the potential of this new technique using simulated rotational frequency splittings. We use noiseless sets that cover the range of observed modes and associate to these artificial splittings observational uncertainties. We also add random noise to present the noise magnification immunity of the method. Since the technique is iterative we also show its potential when using an a priori solution. With the correct regularization, this new method can outperform our RLS implementation in precision, scope, and resolution. Since it results in very different averaging kernels where the solution is poorly constrained, this technique infers different values. Adding such a technique to our compendium of inversion methods will allow us to improve the robustness of our inferences when inverting real observations and better understand where they might be biased and/or unreliable, as we push our techniques to maximize the diagnostic potential of our observations.

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.

Galactic cosmic rays (GCRs) interact with the Earth’s atmosphere to produce energetic neutrons and cosmogenic radionuclides, such as ¹⁴C. The atmosphere is partially shielded from the interstellar GCR spectrum by both the geomagnetic and solar magnetic fields. Solar shielding is often expressed as the heliospheric modulation potential (phi ), which consolidates information about the strength and structure of the solar magnetic field into a single parameter. For the period 1951 to today, (phi ) can be estimated from ground-based neutron monitor data. Prior to 1950, ¹⁴C in tree rings can be used to estimate (phi ) and hence the solar magnetic field, back centuries or millennia. Bridging the gap in the (phi ) record is therefore of vital importance for long-term solar reconstructions. One method is to model (phi ) using the sunspot number (SN) record. However, the SN record is only an indirect measure of the Sun’s magnetic field, introducing uncertainty, and the record suffers from calibration issues. Here we present a new reconstruction of (phi ) based on geomagnetic data, which spans both the entire duration of the neutron monitor record and stretches back to 1845, providing a significant overlap with the ¹⁴C data. We first modify and test the existing model of (phi ) based on a number of heliospheric parameters, namely the open solar flux (F_{S}), the heliospheric current sheet tilt angle (alpha ), and the global heliospheric magnetic polarity (p). This modified model is applied to recently updated geomagnetic estimates of (F_{S}) and cyclic variations of (alpha ) and (p). This approach is shown to produce an annual estimate of (phi ) in excellent agreement with that obtained from neutron monitors over 1951 – 2023. It also suggests that ionisation chamber estimates of (phi ) – which have previously been used to extend the instrumental estimate back from 1951 to 1933 – are not well calibrated. Comparison of the new geomagnetic (phi ) with ¹⁴C estimates of (phi ) suggests that the long-term trend is overestimated in the most recent ¹⁴C data, possibly due to hemispheric differences in the Suess effect, related to the release of carbon by the burning of fossil fuels. We suggest that the new geomagnetic estimate of (phi ) will provide an improved basis for future calibration of long-term solar activity reconstructions.

We investigate the deflection and rotation behaviour of 49 Earth-directed coronal mass ejections (CMEs) spanning the period from 2010 to 2020 aiming to understand the potential influence of coronal holes (CHs) on their trajectories. Our analysis incorporates data from coronagraphic observations captured from multiple vantage points, as well as extreme ultraviolet (EUV) observations utilised to identify associated coronal signatures such as solar flares and filament eruptions. For each CME, we perform a 3D reconstruction using the Graduated Cylindrical Shell (GCS) model. We perform the GCS reconstruction in multiple time steps, from the time at which the CME enters the field of view (FOV) of the coronagraphs to the time it exits. We analyse the difference in the longitude, latitude, and inclination between the first and last GCS reconstructions as possible signatures of deflection/rotation. Furthermore, we examine the presence of nearby CHs at the time of eruption and employ the Collection of Analysis Tools for Coronal Holes (CATCH) to estimate relevant CH parameters, including magnetic-field strength, centre of mass, and area. To assess the potential influence of CHs on the deflection and rotation of CMEs, we calculate the Coronal Hole Influence Parameter (CHIP) for each event and analyse its relationship with their trajectories. A statistically significant difference is observed between CHIP force and the overall change in a CME’s direction in the lower corona. The overall change in a CME’s direction accounts cumulatively for the change in latitude, longitude, and rotation. This suggests that the CHIP force in the low corona has a significant influence on the overall change in the direction of Earth-directed CMEs. However, as the CME evolves outward, the CHIP force becomes less effective in causing deflection or rotation at greater distances. Additionally, we observe a negative correlation between the deflection rate of the CMEs and their velocity, suggesting that higher velocities are associated with lower deflection rates. Hence, the velocity of a CME, along with the magnetic field from CHs, appears to play a significant role in the deflection of CMEs. By conducting this comprehensive analysis, we aim to enhance our understanding of the complex interplay between CHs, CME trajectories, and relevant factors such as velocity and magnetic-field strength.

The global magnetic field in the solar corona is known to contain free magnetic energy and magnetic helicity above that of a current-free (potential) state. But the strength of this non-potentiality and its evolution over the solar cycle remain uncertain. Here we model the corona over Solar Cycle 24 using a simplified magneto-frictional model that retains the magnetohydrodynamic induction equation but assumes relaxation towards force-free equilibrium, driven by solar surface motions and flux emergence. The model is relatively conservative compared to some others in the literature, with free energy approximately 20 – 25% of the potential field energy. We find that unsigned helicity is about a factor 10 higher at Maximum than Minimum, while free magnetic energy shows an even greater increase. The cycle averages of these two quantities are linearly correlated, extending a result found previously for active regions. Also, we propose a practical measure of eruptivity for these simulations, and show that this increases concurrently with the sunspot number, in accordance with observed coronal mass ejection rates. Whilst shearing by surface motions generates (50%) or more of the free energy and helicity in the corona, we show that active regions must emerge with their own internal helicity otherwise the eruptivity is substantially reduced and follows the wrong pattern over time.

The magnetic field inside the sunspot umbra, as observed by the Full-disk MagnetoGraph (FMG) onboard the Advanced Space based Solar Observatory (ASO-S), was found to be experiencing a weakening. To address this issue, we employed a method developed by Xu et al. (2021) to correct the weakening in the data of 20 active regions observed by FMG during the period from 29 December 2022 to 23 July 2023. Research has revealed that the onset of magnetic field weakening occurs at a minimum magnetic field strength of 705 G, with the peak strength reaching up to 1931 G. We computed the change ratio (R_{1}) of the unsigned magnetic flux within the sunspot umbra, considering measurements both before and after correction. The change ratio (R_{1}) spans from 26% to 124%, indicating a significant increase in the unsigned magnetic flux within sunspot umbrae observed by FMG after correction. To illustrate this, we selected four active regions for comparison with data from the Helioseismic and Magnetic Imager (HMI). After correction, we found that the unsigned magnetic flux in sunspot umbrae measured by FMG aligns more closely with that of HMI. This supports the effectiveness of the corrective method for FMG, despite imperfections, particularly at the umbra–penumbra boundary.

We present a case study of a failed eruption that accompanied an M1.5 GOES class solar flare. It was observed by STIX onboard Solar Orbiter, HXI onboard the Advanced Space-based Solar Observatory, AIA onboard Solar Dynamics Observatory, and WAVES onboard the STEREO-A. The important input is from stereoscopic hard X-ray (HXR) observations obtained by HXI and STIX, whose vantage points were separated by (31.5^{circ }), allowing us to unfold the 3D geometry of the event. The eruption was a two-phase event. First, it started with the rope helical kink and then was slowed down, but with the structure still unstable, it erupted two minutes later due to ongoing reconnection in the interacting legs of the kinked structure. A Type III burst was observed in association with the eruption, indicating the acceleration of semirelativistic electrons into the heliosphere. During the second phase, a hot cloud was disconnected and confined in the overlying magnetic field, where the overlying loops connected two adjacent active regions. The estimated and corrected for real geometry velocities are in the range of 385 – 400 km s⁻¹, whereas acceleration reached 4.78 – 6.33 km s⁻². These extreme values are much more demanding from a perspective of conditions that are needed to stop the eruption. Images obtained simultaneously by HXI and STIX located in different vantage points showed that flare-related sources are not lying along a normal to the solar surface. The understanding of the eruption analyzed here has been highly enriched thanks to the stereoscopic information about HXR source locations.

We present an empirical scenario of the energy release process during a solar limb flare on February 5, 2023. This event was observed by the Siberian Radioheliograph (SRH) within the 3 – 12 GHz range and the Advanced Space-based Solar Observatory / Hard X-ray Imager (ASO-S/HXI) within 10 – 300 keV range. The combination of these data allowed us to use information not only about the spectral features but also about the spatial evolution of the flare. The main source of the energy released was a small compact loop which was revealed in both the X-ray and microwave ranges. During the early phases of the flare evolution, a spectral analysis of microwave emission showed that thermal gyrosynchrotron emission turned to gyrosynchrotron emission of nonthermal electrons. This indicated the transition from the heating process to the acceleration processes. Spectral indices derived from hard X-ray and microwave data closely agree with each other and show the classical soft–hard–soft scenario of acceleration. The hardening of the average microwave spectrum at the end of the impulsive phase was caused by the contribution of jet emission to microwaves rather than by peculiarities of the acceleration processes.