We present a case study for the global extreme-ultraviolet (EUV) wave and its chromospheric counterpart the Moreton-Ramsey Wave associated with the second X-class flare in Solar Cycle 25 and a halo coronal mass ejection (CME). The EUV wave was observed in the Hα and EUV passbands with different characteristic temperatures. In the 171 Å and 193/195 Å images, the wave propagates circularly with an initial velocity of 600–720 km s−1 and a deceleration of 110–320 m s−2. The local coronal plasma is heated from log(T/K) ≈ 5.9 to log(T/K) ≈ 6.2 during the passage of the wave front. The Hα and 304 Å images also reveal signatures of wave propagation with a velocity of 310–540 km s−1. With multiwavelength and dual-perspective observations, we found that the wave front likely propagates forwardly inclined to the solar surface with a tilt angle of ∼53°.2. Our results suggest that this EUV wave is a fast-mode magnetohydrodynamic wave or shock driven by the expansion of the associated CME, whose wave front is likely a dome-shaped structure that could impact the upper chromosphere, transition region, and corona.

https://iopscience.iop.org/article/10.3847/1538-4357/ac590d/pdf

Three-dimensional Propagation of the Global Extreme-ultraviolet Wave Associated with a Solar Eruption on 2021 October 28

Abstract Type II radio bursts are often associated with coronal shocks that are typically driven by coronal mass ejections (CMEs) from the Sun. Here we conduct a case study of a type II radio burst that is associated with a C4.5-class flare and a blowout jet, but without the presence of a CME. The blowout jet is observed near the solar disk center in the extreme-ultraviolet (EUV) passbands with different characteristic temperatures. Its evolution involves an initial phase and an ejection phase with a velocity of 560 ± 87 km s −1 . Ahead of the jet front, an EUV wave propagates at a projected velocity of ∼403 ± 84 km s −1 in the initial stage. The velocity of the type II radio burst is estimated to be ∼641 km s −1 , which corresponds to the shock velocity against the coronal density gradient. The EUV wave and the type II radio burst are closely related to the ejection of the blowout jet, suggesting that both are likely the manifestation of a coronal shock driven by the ejection of the blowout jet. The type II radio burst likely starts lower than those associated with CMEs. The combination of the velocities of the radio burst and the EUV wave yields a modified shock velocity at ∼757 km s −1 . The Alfvén Mach number is in the range of 1.09–1.18, implying that the shock velocity is 10%–20% larger than the local Alfvén velocity. 

A Type II Radio Burst Driven by a Blowout Jet on the Sun

Quasi-periodic pulsations (QPPs), which carry time features and plasma characteristics of flare emissions, are frequently observed in light curves of solar/stellar flares. In this study, we investigated non-stationary QPPs associated with recurrent jets during an M1.2 flare on 2022 July 14. A quasi-period of ∼ 45 ± 10 s, determined by the wavelet transform technique, is simultaneously identified at wavelengths of soft/hard X-ray and microwave emissions, which are recorded by the Gravitational Wave High-Energy Electromagnetic Counterpart All-sky Monitor, Fermi and the Nobeyama Radio Polarimeters, respectively. A group of recurrent jets with an intermittent cadence of about 45 ± 10 s are found in the Atmospheric Imaging Assembly (AIA) image series at 304 Å, but they are 180 s earlier than the flare QPP. All observational facts suggest that the flare QPPs could be excited by recurrent jets, and they should be associated with non-thermal electrons that are periodically accelerated by a repeated energy release process, such as repetitive magnetic reconnection. Moreover, the same quasi-period is discovered at double footpoints connected by a hot flare loop in AIA 94 Å, and the phase speed is measured to be ∼1,420 km s−1. Based on the differential emission measure, the average temperatures, number densities, and magnetic field strengths at the loop top and footpoint are estimated to be ∼7.7/6.7 MK, ∼7.5/3.6 × 1010 cm−3, and ∼143/99 G, respectively. Our measurements indicate that the 45-s QPP is probably modulated by the kink-mode wave of the flare loop.

/pdf/flare-quasi-periodic-pulsation-associated-with-recurrent-er43dnq7.pdf

Flare quasi-periodic pulsation associated with recurrent jets

Large-scale extreme-ultraviolet (EUV) waves are frequently observed as an accompanying phenomenon of flares and coronal mass ejections (CMEs). Previous studies mainly focused on EUV waves with single wave fronts that are generally thought to be driven by the lateral expansion of CMEs. Using high spatiotemporal resolution multi-angle imaging observations taken by the Solar Dynamics Observatory and the Solar Terrestrial Relations Observatory, we present the observation of a broad quasiperiodic fast-propagating (QFP) wave train composed of multiple wave fronts along the solar surface during the rising phase of a GOES M3.5 flare on 2011 February 24. The wave train transmitted through a lunate coronal hole (CH) with a speed of ∼840 ± 67 km s−1, and the wave fronts showed an intriguing refraction effect when they passed through the boundaries of the CH. Due to the lunate shape of the CH, the transmitted wave fronts from the north and south arms of the CH started to approach each other and finally collided, leading to a significant intensity enhancement at the collision site. This enhancement might hint at the occurrence of interference between the two transmitted wave trains. The estimated magnetosonic Mach number of the wave train is about 1.13, which indicates that the observed wave train was a weak shock. Period analysis reveals that the period of the wave train was ∼90 s, in good agreement with that of the accompanying flare. Based on our analysis results, we conclude that the broad QFP wave train was a large-amplitude fast-mode magnetosonic wave or a weak shock driven by some nonlinear energy release processes in the accompanying flare.

Observations of a Flare-ignited Broad Quasiperiodic Fast-propagating Wave Train

We report the observation of nonstationary quasi-periodic pulsations (QPPs) in high-energy particles during the impulsive phase of an X4.8 flare on 2002 July 23 (SOL2002-07-23T00:35). The X4.8 flare was simultaneously measured by the Reuven Ramaty High Energy Solar Spectroscopic Imager, Nobeyama Radio Polarimeters, and Nobeyama Radioheliograph. The quasi-period of ∼50 ± 15 s, determined by the wavelet transform, is detected in the γ-ray line emission. Using the same method, a quasi-period of ∼90 ± 20 s is found in the γ-ray continuum, hard X-ray (HXR), and radio emissions during almost the same time. Our observations suggest that the flare QPPs should be associated with energetic ions and nonthermal electrons that are quasi-periodically accelerated by the repetitive magnetic reconnection. The different quasi-periods between the γ-ray line and continuum/HXR/radio emissions indicate an apparent difference in acceleration or propagation between energetic ions and nonthermal electrons of this solar flare.

Quasi-periodic Accelerations of Energetic Particles during a Solar Flare

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.

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

Quasi-periodic fast-propagating (QFP) magnetosonic wave trains are commonly observed in the low corona at extreme ultraviolet wavelength bands. Here, we report the ﬁrst white-light imaging observation of a QFP wave train propagating outwardly in the outer corona ranging from 2 to 4 R (cid:12) . The wave train was recorded by the Large Angle Spectroscopic Coronagraph on board the Solar and Heliospheric Observatory (SOHO) , and was associated with a GOES M1.5 ﬂare in NOAA active region AR12172 at the southwest limb of the solar disk. Measurements show that the speed and period of the wave train were about 218 km s − 1 and 26 minutes, respectively. The extreme ultraviolet imaging observations taken by the Atmospheric Imaging Assembly on board the Solar Dynamic Observatory reveal that in the low corona the QFP wave train was associated with the failed eruption of a breakout magnetic system consisting of three low-lying closed loop systems enclosed by a high-lying large-scale one. Data analysis results show that the failed eruption of the breakout magnetic system was mainly because of the magnetic reconnection that occurred between the two lateral low-lying closed-loop systems. This reconnection enhances the conﬁnement capacity of the magnetic breakout system because the upward-moving reconnected loops continuously feed new magnetic ﬂuxes to the high-lying large-scale loop system. For the generation of the QFP wave train, we propose that it could be excited by the intermittent energy pulses released by the quasi-periodic generation, rapid stretching, and of the upward-moving, strongly bent reconnected loops.

/pdf/white-light-qfp-wave-train-and-the-related-failed-breakout-det17wel.pdf

White-light QFP wave train and the related failed breakout eruption


 The fine magnetic structure is vitally important to understanding the formation, stabilization and eruption of solar filaments, but so far, it is still an open question yet to be resolved. Using stereoscopic observations taken by the Solar Dynamics Observatory and Solar TErrestrial RElations Obsevatory, we studied the generation mechanism of a two-sided-loop jet (TJ) and the ejection process of the jet plasma into the overlying filament-cavity system. We find that the generation of the two-sided-loop jet was due to the magnetic reconnection between an emerging flux loop and the overlying filament. The jet’s two arms ejected along the filament axis during the initial stage. Then, the north arm bifurcated into two parts at about 50 Mm from the reconnection site. After the bifurcation, the two bifurcated parts were along the filament axis and the cavity which hosted the filament, respectively. By tracing the ejecting plasma flows of the TJ inside the filament, we not only measured that the magnetic twist stored in the filament was at least 5π but also found that the fine magnetic structure of the filament-cavity flux rope system is in well agreement with the theoretical results of Magnetic flux rope models.

/pdf/stereoscopic-diagnosing-of-a-filament-cavity-flux-rope-1zcriuep.pdf

Stereoscopic diagnosing of a filament-cavity flux rope system by tracing the path of a two-sided-loop jet

We report the first observations of simultaneous large-amplitude longitudinal and transverse oscillations of a quiescent filament trigged by a two-sided-loop jet formed by the magnetic reconnection between the filament and an emerging loop in the filament channel, recorded by the Solar Dynamics Observatory and the Solar TErrestrial RElations Observatory. The north arm of the jet firstly pushed the filament mass moving northwardly along the magnetic field lines consisting of the coronal cavity, then some elevated filament mass fell back and started to oscillate longitudinally at the bottom of the cavity (i.e., the magnetic dip). The northernmost part of the filament also showed transverse oscillation simultaneously. The amplitude and period of the longitudinal (transverse) oscillation are 12.96 (2.99) Mm and 1.18 (0.33) hours, respectively. By using the method of filament seismology, the radius of curvature of the magnetic dip is about 151 Mm, consistent with that obtained by the 3D reconstruction (166 Mm). Using different physical parameters of the observed longitudinal and transverse oscillations, the magnetic field strength of the filament is estimated to be about 23 and 21 Gauss, respectively. By calculating the energy of the moving filament mass, the minimum energy of the jet is estimated to be about 1.96 x 10^28 erg. We conclude that the newly formed jet can not only trigger simultaneous longitudinal and transverse oscillations in a single filament, but also can be used as a seismology tool for diagnosing filament information, such as the magnetic structure, magnetic field strength, and magnetic twists.

/pdf/stereoscopic-observation-of-simultaneous-longitudinal-and-1fv337mc.pdf

Stereoscopic Observation of Simultaneous Longitudinal and Transverse Oscillations in a Single Filament Driven by Two-sided-loop Jet

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