In this paper, we present a multiwavelength analysis to mass draining and oscillations in a large quiescent filament prior to its successful eruption on 2015 April 28. The eruption of a smaller filament that was parallel and in close, ∼350″ proximity was observed to induce longitudinal oscillations and enhance mass draining within the filament of interest. The longitudinal oscillation with an amplitude of ∼25 Mm and ∼23 km s⁻¹ underwent no damping during its observable cycle. Subsequently the slightly enhanced draining may have excited a eruption behind the limb, leading to a feedback that further enhanced the draining and induced simultaneous oscillations within the filament of interest. We find significant damping for these simultaneous oscillations, where the transverse oscillations proceeded with the amplitudes of ∼15 Mm and ∼14 km s⁻¹, while the longitudinal oscillations involved a larger displacement and velocity amplitude (∼57 Mm, ∼43 km s⁻¹). The second grouping of oscillations lasted for ∼2 cycles and had a similar period of ∼2 hr. From this, the curvature radius and transverse magnetic field strength of the magnetic dips supporting the filaments can be estimated to be ∼355 Mm and ≥34 G. The mass draining within the filament of interest lasted for ∼14 hr. The apparent velocity grew from ∼35 to ∼85 km s⁻¹, with the transition being coincident with the occurrence of the oscillations. We conclude that two filament eruptions are sympathetic, i.e., the eruption of the quiescent filament was triggered by the eruption of the nearby smaller filament.

In this paper, we present the imaging and spectroscopic observations of the simultaneous horizontal and vertical large-amplitude oscillation of a quiescent filament triggered by an extreme-ultraviolet (EUV) wave on 2022 October 2. Particularly, the filament oscillation involved winking phenomenon in Hα images and horizontal motions in EUV images. Originally, a filament and its overlying loops across AR 13110 and 13113 erupted with a highly inclined direction, resulting in an X1.0 flare and a non-radial coronal mass ejection. The fast lateral expansion of loops excited an EUV wave and the corresponding Moreton wave propagating northward. Once the EUV wave front arrived at the quiescent filament, the filament began to oscillate coherently along the horizontal direction, and the “winking filament” appeared concurrently in Hα images. The horizontal oscillation involved an initial amplitude of ∼10.2 Mm and a velocity amplitude of ∼46.5 km s⁻¹, lasting for ∼3 cycles with a period of ∼18.2 minutes and a damping time of ∼31.1 minutes. The maximum Doppler velocities of the oscillating filament are 18 km s⁻¹ (redshift) and −24 km s⁻¹ (blueshift), which were derived from the spectroscopic data provided by the Chinese Hα Solar Explorer/Hα Imaging Spectrograph. The three-dimensional velocity of the oscillation is determined to be ∼50 km s⁻¹ at an angle of ∼50° to the local photosphere plane. Based on the wave–filament interaction, the minimum energy of the EUV wave is estimated to be 2.7 × 10²⁰ J. Furthermore, this event provides evidence that Moreton waves should be excited by the highly inclined eruptions.

Circular-ribbon flares (CFs) are a special type of solar flares owing to their particular magnetic topology. In this paper, we conducted a comprehensive statistical analysis of 134 CFs from 2011 September to 2017 June, including 4 B-class, 82 C-class, 40 M-class, and 8 X-class flares. The flares were observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory spacecraft. The physical properties of CFs are derived, including the location, area (A _CF), equivalent radius (r _CF) assuming a semispherical fan dome, lifetime (τ _CF), and peak soft X-ray (SXR) flux in 1–8 Å. It is found that all CFs are located in active regions, with the latitudes between −30° and 30°. The distributions of areas and lifetimes could be fitted with a lognormal function. There is a positive correlation between the lifetime and area. The peak SXR flux in 1–8 Å is well in accord with a power-law distribution with an index of −1.42. For the 134 CFs, 57% of them are accompanied by remote brightenings or ribbons. A positive correlation exists between the total length (L _RB) and average distance (D _RB) of remote brightenings. About 47% and 51% of the 134 CFs are related to type III radio bursts and jets, respectively. The association rates are independent of flare energies. About 38% of CFs are related to minifilament eruptions, and the association rates increase with flare classes. Only 28% of CFs are related to coronal mass ejections (CMEs), meaning that a majority of them are confined rather than eruptive events. There is a positive correlation between the CME speed and peak SXR flux in 1–8 Å, and faster CMEs tend to be wider.

We present an investigation of partial filament eruption on 2012 June 17 in the active region NOAA 11504. For the first time, we observed the vertical splitting process during the partial eruption with high-resolution narrowband images at 10830 Å. The active filament was rooted in a small δ-sunspot of the active region. Particularly, it underwent the partial eruption in three steps, i.e., the precursor, the first eruption, and the second eruption, while the latter two were associated with a C1.0 flare and a C3.9 flare, respectively. During the precursor, slow magnetic reconnection took place between the filament and the adjoining loops that also rooted in the δ-sunspot. The continuous reconnection not only caused the filament to split into three groups of threads vertically but also formed a new filament, which was growing and accompanied brightening took place around the site. Subsequently, the growing filament erupted together with one group splitted threads, resulted in the first eruption. At the beginning of the first eruption, a subsequent magnetic reconnection occurred between the erupting splitted threads and another ambient magnetic loop. After about 3 minutes, the second eruption occurred as a result of the eruption of two larger unstable filaments induced by the magnetic reconnection. The high-resolution observation provides a direct evidence that magnetic reconnection between filament and its ambient magnetic fields could induce the vertical splitting of the filament, resulting in partial eruption.

Hot channels (HCs) are prevalent in the solar corona and play a critical role in driving flares and coronal mass ejections (CMEs). In this paper, we estimate the energy content of an X1.4 eruptive flare with a fast CME generated by an HC eruption on 2011 September 22. Originating from NOAA Active Region 11302, the HC is the most dramatic feature in 131 and 94 Å images observed by the Atmospheric Imaging Assembly (AIA) on board the Solar Dynamics Observatory (SDO). The flare is simultaneously observed by SDO/AIA, the Reuven Ramaty High-energy Solar Spectroscopic Imager, and the Extreme-ultraviolet Imager on board the “behind” Solar Terrestrial Relations Observatory (STEREO). The CME is simultaneously detected by the white-light coronagraphs of the Large Angle Spectroscopic Coronagraph on board the Solar and Heliospheric Observatory and the COR1 coronagraph on board the behind STEREO. Using multiwavelength and multiview observations of the eruption, various energy components of the HC, flare, and CME are calculated. The thermal and kinetic energies of the HC are (1.77 ± 0.61) × 10³⁰ erg and (2.90 ± 0.79) × 10³⁰ erg, respectively. The peak thermal energy of the flare and total radiative loss of the soft X-ray–emitting plasma are (1.63 ± 0.04) × 10³¹ erg and (1.03–1.31) × 10³¹ erg, respectively. The ratio between the thermal energies of the HC and flare is 0.11 ± 0.03, suggesting that the thermal energy of the HC is not negligible. The kinetic and potential energies of the CME are (3.43 ± 0.94) × 10³¹ erg and (2.66 ± 0.49) × 10³⁰ erg, yielding a total energy of (3.69 ± 0.98) × 10³¹ erg for the CME. Continuous heating of the HC is required to balance the rapid cooling by heat conduction, which probably originates from intermittent magnetic reconnection at the flare current sheet. Our investigation may provide insight into the buildup, release, and conversion of energies in large-scale solar eruptions.