Figure 2 - uploaded by Wei Liu
Content may be subject to copyright.
![Space–time analysis of QFP waves in the funnel. (a)–(c) Running difference space–time diagrams obtained from AIA 171 Å images along the three cuts shown in Figure 1(d). The inset in (a) offers an enlarged view for the selected region, overlaid with a distance averaged profile showing a 43 s periodicity. (d) Base ratio space–time diagram of cut 2 obtained by normalizing image profiles with a pre-event profile. All the space–time diagrams are smoothed with a 3 × 3 pixel boxcar, except for (a) which is smoothed in space only. (e) Vertical slices of (b) at times and distances marked by the two plus signs. They are snapshots of intensity running difference (x-axis) as a function of distance (y-axis) at five consecutive times. Each curve (and thus its average position, marked by the vertical broken line) is incrementally shifted by 12 DN which equals AIA's 12 s cadence and thus the x-axis also serves as elapsed time. Each profile is fitted with a sine function Asin [2π(r − r0)/λ] shown in red, where A is the amplitude, λ is the wavelength, and r0 the initial phase in distance. The average fitted parameters and their standard deviations are listed. The filled circles mark the delayed occurrences at the average position, to which a linear fit indicates a phase velocity vph = 2200 ± 130 km s−1. (f) Horizontal slices of (d) in the selected region, i.e., temporal profiles of intensity base ratio at locations marked by the cross signs. Successive curves at greater distances are shifted upward. The two prominent wave periods of 69 and 181 s are marked with slanted lines, indicating wave propagation.](profile/Wei-Liu-282/publication/230904424/figure/fig1/AS:346648187293698@1459658776936/Space-time-analysis-of-QFP-waves-in-the-funnel-a-c-Running-difference-space-time.png)
Space–time analysis of QFP waves in the funnel. (a)–(c) Running difference space–time diagrams obtained from AIA 171 Å images along the three cuts shown in Figure 1(d). The inset in (a) offers an enlarged view for the selected region, overlaid with a distance averaged profile showing a 43 s periodicity. (d) Base ratio space–time diagram of cut 2 obtained by normalizing image profiles with a pre-event profile. All the space–time diagrams are smoothed with a 3 × 3 pixel boxcar, except for (a) which is smoothed in space only. (e) Vertical slices of (b) at times and distances marked by the two plus signs. They are snapshots of intensity running difference (x-axis) as a function of distance (y-axis) at five consecutive times. Each curve (and thus its average position, marked by the vertical broken line) is incrementally shifted by 12 DN which equals AIA's 12 s cadence and thus the x-axis also serves as elapsed time. Each profile is fitted with a sine function Asin [2π(r − r0)/λ] shown in red, where A is the amplitude, λ is the wavelength, and r0 the initial phase in distance. The average fitted parameters and their standard deviations are listed. The filled circles mark the delayed occurrences at the average position, to which a linear fit indicates a phase velocity vph = 2200 ± 130 km s−1. (f) Horizontal slices of (d) in the selected region, i.e., temporal profiles of intensity base ratio at locations marked by the cross signs. Successive curves at greater distances are shifted upward. The two prominent wave periods of 69 and 181 s are marked with slanted lines, indicating wave propagation.
Source publication
Quasi-periodic propagating fast mode magnetosonic waves in the solar corona were difficult to observe in the past due to relatively low instrument cadences. We report here evidence of such waves directly imaged in EUV by the new Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory. In the 2010 August 1 C3.2 flare/coronal...
Contexts in source publication
Context 1
... analyze wave kinematics, we placed three 20 (14.7 Mm) wide curved cuts that start from the brightest flare kernel and follow the shape of the funnel (Figure 1(d)). By averaging pixels across each cut, we obtained image profiles along it and stacking these profiles over time gives space-time diagrams as shown in Figure 2, where we see two types of moving features: ) Each wave front travels up to ∼400 Mm with a lifetime of ∼200 s before reaching the edge of AIA's FOV, likely resulting from damping and amplitude decay with distance (∝ 1/r 2 ). ...
Context 2
... find no temporal correlation between the waves in the closed loops and those in the funnel that is dominated by outgoing waves, except for marginal incoming wave signals near its base (Figure 2). Because of their simplicity (no superposition of bidirectional propagation), we choose to further analyze the waves in the funnel with Fourier transform as presented below. ...
Context 3
... Fourier power from running difference and detrended im- ages yields consistent peak frequencies, which can be visually identified in the space-time domain. The lowest frequency ν 0 = 5.5 mHz (P 0 = 181 ± 13 s ≈ 3 minutes) manifests as slow modulations in Figures 2(b) and (d) during 08:06-08:18 UT. The next period 69 ± 3 s (14.5 mHz), domi- nating the power from running difference images (Figure 4(b)), matches the temporal spacing between bright stripes near 08:08 UT in Figures 2(a)-(c) and the period given by the sinusoidal fits (Figure 2(e)). ...
Context 4
... lowest frequency ν 0 = 5.5 mHz (P 0 = 181 ± 13 s ≈ 3 minutes) manifests as slow modulations in Figures 2(b) and (d) during 08:06-08:18 UT. The next period 69 ± 3 s (14.5 mHz), domi- nating the power from running difference images (Figure 4(b)), matches the temporal spacing between bright stripes near 08:08 UT in Figures 2(a)-(c) and the period given by the sinusoidal fits (Figure 2(e)). The corresponding wave fronts are prominent in the original and Fourier filtered images (Figures 1(d)-(i), Animation 1(E)). ...
Context 5
... lowest frequency ν 0 = 5.5 mHz (P 0 = 181 ± 13 s ≈ 3 minutes) manifests as slow modulations in Figures 2(b) and (d) during 08:06-08:18 UT. The next period 69 ± 3 s (14.5 mHz), domi- nating the power from running difference images (Figure 4(b)), matches the temporal spacing between bright stripes near 08:08 UT in Figures 2(a)-(c) and the period given by the sinusoidal fits (Figure 2(e)). The corresponding wave fronts are prominent in the original and Fourier filtered images (Figures 1(d)-(i), Animation 1(E)). ...
Context 6
... corresponding wave fronts are prominent in the original and Fourier filtered images (Figures 1(d)-(i), Animation 1(E)). These two periods are also evident in the emission profiles of Figure 2(f). The higher frequency 25.1 mHz (40 ± 1 s) has considerably weaker power and a close frequency of 23 mHz (see Figure 4(d)) can be seen in the spacing of nar- row stripes near 08:01 UT (Figure 2(a)), when the other two frequencies are not yet strong. ...
Context 7
... two periods are also evident in the emission profiles of Figure 2(f). The higher frequency 25.1 mHz (40 ± 1 s) has considerably weaker power and a close frequency of 23 mHz (see Figure 4(d)) can be seen in the spacing of nar- row stripes near 08:01 UT (Figure 2(a)), when the other two frequencies are not yet strong. ...
Context 8
... The accompanying CME is unlikely to be the wave trig- ger because it takes place gradually for ∼30 minutes ( wave periods, Figure 2(b)) and its single pulse would have difficulty sustaining oscillations lasting ∼1 hr as ob- served here without being damped. However, the environ- ment in its wake might be favorable for these waves. ...
Similar publications
We consider a non-rotating, massive test particle acted upon by a 'pressure'-type, non-geodesic acceleration arising from a certain general class of gravitational theories with nonminimal coupling between the matter and the metric. The resulting orbital perturbations for a two-body system are investigated both analytically and numerically. Remarkab...
City parks, which have a significant place in open and green area systems, make important contributions in ecological, social and economic terms. These parks, which have undergone many developmental processes in the historical aspect, have been shaped by the users as well as the decisions of the planners and designers. This process, which is follow...
The transition between the supersonic solar wind and the subsonic heliosheath, the termination shock (TS), was observed by Voyager 2 (V2) on 2007 August 31-September 1 at a distance of 84 AU from the Sun. The data reveal multiple crossings of a complex, quasi-perpendicular supercritical shock. These experimental data are the starting point for a mo...
Citations
... The narrow QFP wave train was first reported by Liu et al. (2011) utilizing the AIA imaging data, which were identified as a fast-magnetosonic wave train by Ofman et al. (2011) using the 3D MHD model. These wave trains have some significant features different from the classical large-scale EUV wave that propagates along the solar surface, which is dominated by the vertical magnetic field line, such as permanently confined propagating along the closed-or open-loops system. ...
... These findings suggest that the counterpropagating QFP wave trains within closed coronal loops can generate a turbulent cascade capable of carrying substantial energy for heating the corona in low-corona magnetic structures. Generally, it was found that the narrow QFP wave trains appear in similar periodicities with the quasiperiodic pulsations (QPP; Liu et al. 2011;Shen & Liu 2012;Yuan et al. 2013;Li et al. 2018;Zhou et al. 2022a;Duan et al. 2022) of the accompanying flare emissions commonly seen from radio to hard X-rays (Nakariakov & Melnikov 2009;Li et al. 2015Li et al. , 2020Li et al. , 2021Zhang et al. 2016;Zhang 2024). This result aligns with previous studies indicating that flares can produce nonthermal electrons, which are accountable for microwave and X-ray emissions. ...
... Generally, the most likely relevant driven mechanisms are the energy release in the magnetic reconnections process Shen & Liu 2012;Yuan et al. 2013) and the dispersive evolution (Roberts et al. 1983;Pascoe et al. 2013Pascoe et al. , 2017Nisticò et al. 2014;Shen et al. 2018b). Liu et al. (2011) first reported the association between the flare pulsation detected in hard X-ray by RHESSI and the narrow QFP wave trains' periodicities: the narrow QFP wave trains exhibit a close physical relationship with the accompanying flares, always sharing similar periods and having a close temporal and spatial association (Shen & Liu 2012;Shen et al. 2013bShen et al. , 2018a. In some instances, multiple narrow wave trains with different properties are excited one after another, and each wave train is accompanied by an energy burst (Yuan et al. 2013;Miao et al. 2020;Zhou et al. 2022c), suggesting a strong connection between the flares and the narrow QFP wave trains. ...
This paper presents three distinct wave trains that occurred on 2023 April 21: a broad quasiperiodic fast-propagating (QFP) wave train and bidirectional narrow QFP wave trains. The broad QFP wave train expands outward in a circular wave front, while bidirectional narrow QFP wave trains propagate in the northward and southward directions, respectively. The concurrent presence of the wave trains offers a remarkable opportunity to investigate their respective triggering mechanisms. Measurement shows that the speed of the broad QFP wave train is in the range of 300–1100 km s ⁻¹ in different propagating directions. There is a significant difference in the speed of the bidirectional narrow QFP wave trains: the southward propagation achieves 1400 km s ⁻¹ , while the northward propagation only reaches about 550 km s ⁻¹ accompanied by a deceleration of about 1–2 km s ⁻² . Using the wavelet analysis, we find that the periodicity of the propagating wave trains in the southward and northward directions closely matches the quasiperiodic pulsations exhibited by the flares. Based on these results, the narrow QFP wave trains were most likely excited by the intermittent energy release in the accompanying flare. In contrast, the broad QFP wave train had a tight relationship with the erupting filament, probably attributed to the unwinding motion of the erupting filament, or the leakage of the fast sausage wave train inside the filament body.
... The quasi-periodic wave train (QFP, Liu et al. 2011) is an intriguing phenomenon of the disturbance to the corona that was observed for the first time by the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory (SDO, Lemen et al. 2012). It has been interpreted as the fast-mode magnetoacoustic wave (Cooper et al. 2003), characterized by continuous, narrow arc-like structures that propagate rapidly at speed up to 1416 km s −1 (Shen et al. 2013;Kumar et al. 2017). ...
We propose a mechanism for the excitation of large-scale quasi-periodic fast-propagating magnetoa-coustic (QFP) waves observed on both sides of the coronal mass ejection (CME). Through a series of numerical experiments, we successfully simulated the quasi-static evolution of the equilibrium locations of the magnetic flux rope in response to the change of the background magnetic field, as well as the consequent loss of the equilibrium that eventually gives rise to the eruption. During the eruption, we identified QFP waves propagating radially outwards the flux rope, and tracing their origin reveals that they result from the disturbance within the flux rope. Acting as an imperfect waveguide, the flux rope allows the internal disturbance to escape to the outside successively via its surface, invoking the observed QFP waves. Furthermore, we synthesized the images of QFP waves on the basis of the data given by our simulations, and found the consistence with observations. This indicates that the leakage of the disturbance outside the flux rope could be a reasonable mechanism of QFP waves.
... ultraviolet (EUV) emission intensity (e.g. Liu et al. 2011Liu et al. , 2012Shen & Liu 2012 ;Shen et al. 2013Shen et al. , 2019Shen et al. , 2020Qu, Jiang & Chen 2017 ;Miao et al. 2019Miao et al. , 2020. Typically, QFP waves resemble a train of 'ripples', emanating from an epicentre in an active region. ...
The highly-filamented nature of the coronal plasma significantly influences dynamic processes in the corona such as magnetohydrodynamic waves and oscillations. Fast magnetoacoustic waves, guided by coronal plasma non-uniformities, exhibit strong geometric dispersion, forming quasi-periodic fast-propagating (QFP) wave trains. QFP wave trains are observed in extreme-ultraviolet imaging data and indirectly in microwaves and low-frequency radio, aiding in understanding the magnetic connectivity, energy, and mass transport in the corona. However, measuring the field-aligned group speed of QFP wave trains, as a key parameter for seismological analysis, is challenging due to strong dispersion and associated rapid evolution of the wave train envelope. We demonstrate that the group speed of QFP wave trains formed in plane low-β coronal plasma non-uniformities can be assessed through the propagation of the wave train’s effective centre of mass, referred to as the wave train’s centroid speed. This centroid speed, as a potential observable, is shown empirically to correspond to the group speed of the most energetic Fourier harmonic in the wave train. The centroid speed is found to be almost insensitive to the waveguide density contrast with the ambient corona, and to vary with the steepness of the transverse density profile. The discrepancy between the centroid speed as the group speed measure and the phase speed at the corresponding wavelength is shown to reach 70%, which is crucial for the energy flux estimation and interpretation of observations.
... Magnetohydrodynamic (MHD) waves and oscillations are ubiquitous in the dynamic solar atmosphere (see Nakariakov & Verwichte 2005;Nakariakov et al. 2016;Shen et al. 2022; and references therein), such as the spectacular global extreme ultraviolet waves (e.g., Liu & Ofman 2014;Shen & Liu 2012a;Shen et al. 2018a, quasiperiodic fast-propagating (QFP) wave trains (e.g., Liu et al. 2011;Li et al. 2018b;Shen et al. 2022), and transverse and vertical oscillations of filaments and coronal loops (e.g., Zimovets & Nakariakov 2015;Shen et al. 2014aShen et al. , 2014b. Kink oscillations and QFP wave trains are prevalent MHD waves in the magnetized corona, which can be used to diagnose the mysterious properties of the coronal plasma. ...
... The first QFP wave train was reported by Liu et al. (2011) using the high temporal and high spatial resolution images taken by the Atmospheric Imaging Assembly (AIA; Lemen et al. 2012) on board the SDO. Over the last decade, QFP wave trains have been extensively studied theoretically and observationally in details. ...
We present the observations of multimode kink waves and a narrow quasiperiodic fast-propagating (QFP) wave train in association with a jet on 2011 December 11. The jet impinged on a loop, which excited a propagating kink mode transitioning into a standing kink mode and also excited a QFP wave train away from the jet. Motion magnification is used to fit the higher harmonic standing wave oscillation profile with three periods at three different spatial locations. The periods have the ratio 6:3:2. The ratio of the fundamental mode to the second harmonic of the standing wave is about 1.95, suggesting that the magnetic field strength variation effect is strong enough to cancel out the density stratification. The differential emission measure is used to estimate the loop’s plasma property at these three points, and it found the density and the temperature are roughly constant. The magnetic field strength, B = 51 ± 16 G, is derived by the coronal seismology using the fundamental kink mode. It is striking to find that the the ratio of the second harmonic to the third harmonic of the kink wave coincides with that of the periods of the QFP wave train, and the ratio of periods is about 1.5 in both cases. We propose that the excitation of the high-order harmonics and the QFP wave train could be the nonlinear response of the steep density-gradient plasma interacting with electromagnetic field in the southwest foot region. This region, like a resonator, might play an important role in energy reservoir capture and act as a frequency filter to generate propagating waves of particular frequencies.
... In addition to this, since we are using imaging observations which depend upon density perturbations to probe the presence of any disturbances, presence of Alfvén waves can be safely discarded as it can not be probed by perturbation in density because of its incompressible nature (Priest 2014). Also, for fast waves, the propagation speeds are expected to be much larger (roughly of an order of 1000 km s −1 in the solar corona) than these speeds estimated using Surfing technique (Liu et al. 2011Liu & Ofman 2014;Qu et al. 2017). Therefore the PDs are essentially the flows but certainly not the slow waves with phase speed scaled as √ T or any other form of waves like fast magnetoacoustic waves or Alfvén waves. ...
Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO), are analyzed to determine its driving mechanism and physical nature. Two magnetic strands in the localised corona are observed to approach and merge with each other followed by the generation of brightening, which further propagates in a cusp-shaped magnetic channel. Differential emission measure analysis shows an occurrence of heating in this region-of-interest (ROI). We extrapolate potential magnetic field lines at coronal heights from observed Helioseismic and Magnetic Imager (HMI) vector magnetogram via Green's function method using MPI-AMRVAC. We analyze the field to locate magnetic nulls and quasi-separatrix layers (QSLs) which are preferential locations for magnetic reconnection. Dominant QSLs including a magnetic null are found to exist and match the geometry followed by PDs, therefore, it provides conclusive evidence of magnetic reconnection. In addition, spectroscopic analysis of Interface Region Imaging Spectrograph (IRIS) Si IV 1393.77 {\AA} line profiles show a rise of line-width in the same time range depicting presence of mass motion in the observed cusp-shaped region. PDs are observed to exhibit periodicities of around four minutes. The speeds of PDs measured by Surfing Transform Technique are almost close to each other in four different SDO/AIA bandpasses, i.e., 304, 171, 193 and 131 {\AA} excluding the interpretation of PDs in terms of slow magnetoacoustic waves. We describe comprehensively the observed PDs as quasi-periodic plasma flows generated due to periodic reconnection in vicinity of a coronal magnetic null.
... In addition to this, since we are using imaging observations which depend upon density perturbations to probe the presence of any disturbances, presence of Alfvén waves can be safely discarded as it can not be probed by perturbation in density because of its incompressible nature (Priest 2014). Also, for fast waves, the propagation speeds are expected to be much larger (roughly of an order of 1000 km s −1 in the solar corona) than these speeds estimated using Surfing technique (Liu et al. 2011Liu & Ofman 2014;Qu et al. 2017). Therefore the PDs are essentially the flows but certainly not the slow waves with phase speed scaled as √ T or any other form of waves like fast magnetoacoustic waves or Alfvén waves. ...
Multiwavelength observations of the propagating disturbances (PDs), discovered by Atmospheric Imaging Assembly (AIA) onboard Solar Dynamics Observatory (SDO), are analyzed to determine its driving mechanism and physical nature. Two magnetic strands in the localised corona are observed to approach and merge with each other followed by the generation of brightening, which further propagates in a cusp-shaped magnetic channel. Differential emission measure analysis shows an occurrence of heating in this region-of-interest (ROI). We extrapolate potential magnetic field lines at coronal heights from observed Helioseismic and Magnetic Imager (HMI) vector magnetogram via Green's function method using MPI-AMRVAC. We analyze the field to locate magnetic nulls and quasi-separatrix layers (QSLs) which are preferential locations for magnetic reconnection. Dominant QSLs including a magnetic null are found to exist and match the geometry followed by PDs, therefore, it provides conclusive evidence of magnetic reconnection. In addition, spectroscopic analysis of Interface Region Imaging Spectrograph (IRIS) Si IV 1393.77Å line profiles show a rise of line-width in the same time range depicting presence of mass motion in the observed cusp-shaped region. PDs are observed to exhibit periodicities of around four minutes. The speeds of PDs measured by Surfing Transform Technique are almost close to each other in four different SDO/AIA bandpasses, i.e., 304, 171, 193 and 131 A excluding the interpretation of PDs in terms of slow magnetoacoustic waves. We describe comprehensively the observed PDs as quasi-periodic plasma flows generated due to periodic reconnection in vicinity of a coronal magnetic null.
... On the other hand, the decayless oscillation often lasts for several wave periods or even longer (Tian et al. 2012;Anfinogentov et al. 2015). Hence, the external driver should be continuous to keep the decayless oscillation for a long time, as seen in Appendix B. Now, several theoretical models have been proposed to illustrate the excitation/driver of decayless oscillations, for instance, it might be triggered by the fast magnetoacoustic wave train (Liu et al. 2011;Wang et al. 2012), or it could be excited by the coronal rain caused by a catastrophic cooling process (Verwichte et al. 2017), or it may be a self-oscillation that is driven by the slipping interaction between oscillating loops and steady external medium flows . However, the triggered eruptions are difficult to detect, largely due to their fine-scale structures, as shown in Figure 10, which presents an overview of our observation. ...
Coronal loop oscillations are common phenomena in the solar corona, which are often classified as decaying and decayless oscillations. Using the high-resolution observation measured by the Extreme Ultraviolet Imager (EUI) on board the Solar Orbiter, we statistically investigate small-scale transverse oscillations with short periods (<200 s) of coronal loops in an active region (AR), i.e., NOAA AR 12965. A total of 111 coronal loops are identified in EUI 174 Å images, and they all reveal transverse oscillations without any significant decaying, regarded as decayless oscillations. Oscillatory periods are measured from ∼11 to ∼185 s, with a median period of 40 s. Thus, they are also termed short-period oscillations. The corresponding loop lengths are measured from ∼10.5 to ∼30.2 Mm, and a strong dependence of oscillatory periods on loop lengths is established, indicating that the short-period oscillations are standing kink-mode waves in nature. Based on the coronal seismology, kink speeds are measured to be ∼330–1910 km s ⁻¹ , and magnetic field strengths in coronal loops are estimated to be ∼4.1–25.2 G, while the energy flux carried by decayless kink oscillations lies in the range from roughly 7 to 9220 W m ⁻² . Our estimations suggest that the wave energy carried by short-period decayless kink oscillations cannot support the coronal heating in the AR.
... On the other hand, the decayless oscillation often lasts for several wave periods or even longer (Tian et al. 2012;Anfinogentov et al. 2015). Hence, the external driver should be continuous to keep the decayless oscillation for a long time, as seen in Appendix B. Now, several theoretical models have been proposed to illustrate the excitation/driver of decayless oscillations, for instance, it might be triggered by the fast magnetoacoustic wave train (Liu et al. 2011;Wang et al. 2012), or it could be excited by the coronal rain caused by a catastrophic cooling process (Verwichte et al. 2017), or it may be a self oscillation that is driven by the slipping interaction between oscillating loops and steady external medium flows . However, the triggered eruptions are difficult to detect, largely due to their fine-scale structures, as shown in Figure 10, which presents an overview of our observation. ...
Coronal loop oscillations are common phenomena in the solar corona, which are often classified as decaying and decayless oscillations. Using the high-resolution observation measured by the Extreme Ultraviolet Imager (EUI) onboard the Solar Orbiter, we statistical investigate small-scale transverse oscillations with short periods (<200 s) of coronal loops in an active region, i.e., NOAA 12965. A total of 111 coronal loops are identified in EUI 174 A images, and they all reveal transverse oscillations without any significant decaying, regarding as decayless oscillations. Oscillatory periods are measured from about 11 s to 185 s, with a median period of 40 s. Thus, they are also termed as short-period oscillations. The corresponding loop lengths are measured from about 10.5 Mm to 30.2 Mm, and a strong dependence of oscillatory periods on loop lengths is established, indicating that the short-period oscillations are standing kink-mode waves in nature. Based on the coronal seismology, kink speeds are measured to about 330-1910 km/s, and magnetic field strengths in coronal loops are estimated to about 4.1-25.2 G, while the energy flux carried by decayless kink oscillations lies in the range from roughly 7 W m^(-2) to 9220 W m^(-2). Our estimations suggest that the wave energy carried by short-period decayless kink oscillations can not support the coronal heating in the active region.
... Liu et al. (2011), and Liu et al.(2014), Fourier analysis is applied to the Train-2. ...
About the driven mechanisms of the quasiperiodic fast-propagating (QFP) wave trains, there exist two dominant competing physical explanations: they are associated with the flaring energy release or attributed to the waveguide dispersion. Employing Solar Dynamics Observatory/Atmospheric Imaging Assembly 171 Å images, we investigated a series of QFP wave trains composed of multiple wave fronts propagating along a loop system during the accompanying flare on 2011 November 11. The wave trains showed a high correlation in start times with the energy release of the accompanying flare. Measurements show that the wave trains’ phase speed is almost consistent with its group speed with a value of about 1000 km s ⁻¹ , indicating that the wave trains should not be considered dispersed waves. The period of the wave trains was the same as that of the oscillatory signal in X-ray emissions released by the flare. Thus we propose that the QFP wave trains were most likely triggered by the flare rather than by dispersion. We investigated the seismological application with the QFP waves and then obtained that the magnetic field strength of the waveguide was about 10 G. Meanwhile, we also estimated that the energy flux of the wave trains was about 1.2 × 10 ⁵ erg cm ⁻² s ⁻¹ .
... Following the method of DeForest (2004), Liu et al. (2011), and, Fourier analysis is applied to the Train-2. We extracted a three-dimensional data cube (x, y, t) from a time series of 171 Å running difference images for the FOV marked by the white box in Fig.1 (d) during 06:50:00-07:03:48 UT. ...
About the driven mechanisms of the quasi-periodic fast-propagating (QFP) wave trains, there exist two dominant competing physical explanations: associated with the flaring energy release or attributed to the waveguide dispersion. Employing Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) 171 Å images , we investigated a series of QFP wave trains composed of multiple wavefronts propagating along a loop system during the accompanying flare on 2011 November 11. The wave trains showed a high correlation in start time with the energy release of the accompanying flare. Measurements show that the wave trains' phase speed is almost consistent with its group speed with a value of about 1000 km s −1 , indicating that the wave trains should not be dispersed waves. The period of the wave trains was the same as that of the oscillatory signal in X-ray emissions released by the flare. Thus we propose that the QFP wave trains were most likely triggered by the flare rather than by dispersion. We investigated the seismological application with the QFP waves and then obtained that the magnetic field strength of the waveguide was about 10 Gauss. Meanwhile, we also estimated that the energy flux of the wave trains was about 1.2 × 10 5 erg · cm −2 s −1 .
