Coronal magnetic fields evolve quasi-statically over long timescales and dynamically over short timescales.As of now there exist no regular measurements of coronal magnetic fields,and therefore generating the coronal ...Coronal magnetic fields evolve quasi-statically over long timescales and dynamically over short timescales.As of now there exist no regular measurements of coronal magnetic fields,and therefore generating the coronal magnetic field evolution using observations of the magnetic field at the photosphere is a fundamental requirement to understanding the origin of transient phenomena from solar active regions(ARs).Using the magneto-friction(MF)approach,we aim to simulate the coronal field evolution in the solar AR 11429.The MF method is implemented in the open source PENCIL CODE along with a driver module to drive the initial field with different boundary conditions prescribed from observed vector magnetic fields at the photosphere.In order to work with vector potential and the observations,we prescribe three types of bottom boundary drivers with varying free-magnetic energy.The MF simulation reproduces the magnetic structure,which better matches the sigmoidal morphology exhibited by Atmospheric Imaging Assembly(AIA)images at the pre-eruptive time.We found that the already sheared field further driven by the sheared magnetic field will maintain and further build the highly sheared coronal magnetic configuration,as seen in AR 11429.Data-driven MF simulation is a viable tool to generate the coronal magnetic field evolution,capturing the formation of the twisted flux rope and its eruption.展开更多
Remote-sensing measurements indicate that heavy ions in the corona undergo an anisotropic and mass-charge dependent energization.A popular explanation to this phenomenon is the damping of the Alfven/ion cyclotron wave...Remote-sensing measurements indicate that heavy ions in the corona undergo an anisotropic and mass-charge dependent energization.A popular explanation to this phenomenon is the damping of the Alfven/ion cyclotron waves.In this paper,we propose that the ion beam instability can be an important source of the Alfven/ion cyclotron waves,and we study the excitation of the ion beam instability in the corona at the heliocentric distance~3R_(⊙)and the corresponding energy transfer process therein ba sed on plasma kinetic theory.The results indicate that the existence of the motionless heavy ions inhibits the ion beam instability.However,the anisotropic beams of heavy ions promote the excitation of the ion beam instability.Besides,the existence ofαbeams can provide a second energy source for exciting beam instability.However,when both the proton beam and the a beam reach the instability excitation threshold,the proton beam driven instability excites preferentially.Moreover,the excitation threshold of the Alfven/ion cyclotron instability driven by ion beam is of the local Alfven speed or even less in the corona.展开更多
An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perih...An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles(CEBTs) occurring near the footpoints of coronal loops.Combining SDO/AIA observations, we determine the altitudes of six distinct CEBTs by stereoscopy, ranging from ~1300 to 3300 km. We then notice a substantial presence of dark, cooler filamentary structures seemingly beneath the CEBTs, displaying periodic up-and-down motions lasting 3–5 minutes. This periodic behavior suggests an association of the majority of CEBTs with Type I spicules. Out of the ten selected CEBTs with fast downward velocity, six exhibit corrected velocities close to or exceeding 50 km s^(-1). These velocities notably surpass the typical speeds of Type I spicules. We explore the generation of such velocities. It indicates that due to the previous limited observations of spicules in the EUV wavelengths, they may reveal novel observational features beyond our current understanding. Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.展开更多
It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope stru...It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope structure.The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure or that some processes destroyed these magnetic flux rope structures.Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures.We introduce a special kind of ICME which has a low magnetic field magnitude and stable magnetic field direction,relatively fast expansion speed,and lower proton temperature and density.All three of the measured magnetic field components are relatively stable.We want to know whether these ICMEs also have magnetic flux rope structures or not.We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics.We took a special ICME as an example,which had an apparent rope configuration at 1 au but evolved to a special ICME at 5.4 au,to illustrate that this kind of ICME could come from magnetic clouds(MCs)whose rope structure had been being stretched due to expansion.We inferred that the missing obvious flux rope structure may be due to the expansion of MCs,not the flank crossing effect.However,more than 50%of the events were associated with the dominant x-component of the magnetic field,which indicates a leg crossing.Therefore,the detection of part of these special ICMEs may also be the result of the leg-crossing effect.展开更多
The propagation of disturbances in the solar atmosphere is inherently three-dimensional(3D), yet comprehensive studies on the spatial structure and dynamics of 3D wave fronts are scarce. Here we conduct high-resolutio...The propagation of disturbances in the solar atmosphere is inherently three-dimensional(3D), yet comprehensive studies on the spatial structure and dynamics of 3D wave fronts are scarce. Here we conduct high-resolution 3D numerical simulations to investigate filament eruptions, focusing particularly on the 3D structure and genesis of extreme ultraviolet(EUV) waves. Our results demonstrate that the EUV wave front forms a dome-like configuration subdivided into three distinct zones. The foremost zone, preceding the flux rope, consists of fastmode shock waves that heat the adjacent plasma. Adjacent to either side of the flux rope, the second zone contains expansion waves that cool the nearby plasma. The third zone, at the juncture of the first two, exhibits minimal disturbances. This anisotropic structure of the wave front stems from the configuration and dynamics of the flux rope, which acts as a 3D piston during eruptions—compressing the plasma ahead to generate fast-mode shocks and evacuating the plasma behind to induce expansion waves. This dynamic results in the observed anisotropic wave front. Additionally, with synthetic EUV images from simulation data, the EUV waves are observable in Atmospheric Imaging Assembly 193 and 211 ?, which are identified as the fast-mode shocks. The detection of EUV waves varies with the observational perspective: the face-on view reveals EUV waves from the lower to the higher corona, whereas an edge-on view uncovers these waves only in the higher corona.展开更多
基金the support from DST through Startup Research Grantfunding from the European Research Council(ERC)under the European Union’s Horizon 2020 research and innovation program(Project Uni SDyn,grant agreement No.818665)(JW)。
文摘Coronal magnetic fields evolve quasi-statically over long timescales and dynamically over short timescales.As of now there exist no regular measurements of coronal magnetic fields,and therefore generating the coronal magnetic field evolution using observations of the magnetic field at the photosphere is a fundamental requirement to understanding the origin of transient phenomena from solar active regions(ARs).Using the magneto-friction(MF)approach,we aim to simulate the coronal field evolution in the solar AR 11429.The MF method is implemented in the open source PENCIL CODE along with a driver module to drive the initial field with different boundary conditions prescribed from observed vector magnetic fields at the photosphere.In order to work with vector potential and the observations,we prescribe three types of bottom boundary drivers with varying free-magnetic energy.The MF simulation reproduces the magnetic structure,which better matches the sigmoidal morphology exhibited by Atmospheric Imaging Assembly(AIA)images at the pre-eruptive time.We found that the already sheared field further driven by the sheared magnetic field will maintain and further build the highly sheared coronal magnetic configuration,as seen in AR 11429.Data-driven MF simulation is a viable tool to generate the coronal magnetic field evolution,capturing the formation of the twisted flux rope and its eruption.
基金funded by the National Natural Science Foundation of China(NSFC)under No.12347166。
文摘Remote-sensing measurements indicate that heavy ions in the corona undergo an anisotropic and mass-charge dependent energization.A popular explanation to this phenomenon is the damping of the Alfven/ion cyclotron waves.In this paper,we propose that the ion beam instability can be an important source of the Alfven/ion cyclotron waves,and we study the excitation of the ion beam instability in the corona at the heliocentric distance~3R_(⊙)and the corresponding energy transfer process therein ba sed on plasma kinetic theory.The results indicate that the existence of the motionless heavy ions inhibits the ion beam instability.However,the anisotropic beams of heavy ions promote the excitation of the ion beam instability.Besides,the existence ofαbeams can provide a second energy source for exciting beam instability.However,when both the proton beam and the a beam reach the instability excitation threshold,the proton beam driven instability excites preferentially.Moreover,the excitation threshold of the Alfven/ion cyclotron instability driven by ion beam is of the local Alfven speed or even less in the corona.
基金supported by National Key R&D Program of China Nos. 2022YFF0503800 and 2021YFA0718600the Strategic Priority Research Program of the Chinese Academy of Sciences (No. XDB0560000)+1 种基金National Natural Science Foundation of China (NSFC, Grant Nos. 12073032, 42274201, 42150105, and 42204176)the Specialized Research Fund for State Key Laboratories of China。
文摘An extreme ultraviolet(EUV) close-up view of the Sun offers unprecedented detail of heating events in the solar corona. Enhanced temporal and spatial images obtained by the Solar Orbiter during its first science perihelion enabled us to identify clustered EUV bright tadpoles(CEBTs) occurring near the footpoints of coronal loops.Combining SDO/AIA observations, we determine the altitudes of six distinct CEBTs by stereoscopy, ranging from ~1300 to 3300 km. We then notice a substantial presence of dark, cooler filamentary structures seemingly beneath the CEBTs, displaying periodic up-and-down motions lasting 3–5 minutes. This periodic behavior suggests an association of the majority of CEBTs with Type I spicules. Out of the ten selected CEBTs with fast downward velocity, six exhibit corrected velocities close to or exceeding 50 km s^(-1). These velocities notably surpass the typical speeds of Type I spicules. We explore the generation of such velocities. It indicates that due to the previous limited observations of spicules in the EUV wavelengths, they may reveal novel observational features beyond our current understanding. Gaining insights into these features contributes to a better comprehension of small-scale coronal heating dynamics.
基金support from the National Natural Science Foundation of China(NSFC,Grant Nos.41974197,41804162,and 42104158)supported by Central Plains Science and Technology Innovation Leading Talents of Henan Province under grant No.244200510012。
文摘It is generally believed that coronal mass ejections(CMEs)have magnetic flux rope structures because of their helical shapes.However,only about 30%–40%of interplanetary CMEs(ICMEs)have a local magnetic flux rope structure.The usual explanations are that the spacecraft only crossed the flank of the ropes and failed to detect the complete magnetic flux rope structure or that some processes destroyed these magnetic flux rope structures.Several studies suggest that some ICMEs inherently possess disordered magnetic fields and consequently exhibit no magnetic flux-rope structures.We introduce a special kind of ICME which has a low magnetic field magnitude and stable magnetic field direction,relatively fast expansion speed,and lower proton temperature and density.All three of the measured magnetic field components are relatively stable.We want to know whether these ICMEs also have magnetic flux rope structures or not.We identified 20 special ICMEs and analyzed their evolution based on their observed characteristics.We took a special ICME as an example,which had an apparent rope configuration at 1 au but evolved to a special ICME at 5.4 au,to illustrate that this kind of ICME could come from magnetic clouds(MCs)whose rope structure had been being stretched due to expansion.We inferred that the missing obvious flux rope structure may be due to the expansion of MCs,not the flank crossing effect.However,more than 50%of the events were associated with the dominant x-component of the magnetic field,which indicates a leg crossing.Therefore,the detection of part of these special ICMEs may also be the result of the leg-crossing effect.
基金supported by Strategic Priority Research Program of the Chinese Academy of Sciences No. XDB0560000National Key R&D Program of China No. 2022YFF0503804+6 种基金NSFC grants 11933009, 12273107, U2031141 and 12073073grants associated with the Yunling Scholar Project of Yunnan Provincethe Yunnan Province Scientist Workshop of Solar Physicsthe Yunnan Key Laboratory of Solar Physics and Space Exploration of Code 202205AG070009the Special Project for the construction of science and technology innovation centers faced to South Asiaand Southeast Asia-Yunnan International Joint Innovation Platform: “China-Malaysia HF-VHF Advanced Radio Astronomy Technology International Joint Laboratory of Yunnan” (202303AP140003)the support by grants associated with the Yunnan Revitalization Talent Support Programthe Foundation of the Chinese Academy of Sciences (Light of West China Program)。
文摘The propagation of disturbances in the solar atmosphere is inherently three-dimensional(3D), yet comprehensive studies on the spatial structure and dynamics of 3D wave fronts are scarce. Here we conduct high-resolution 3D numerical simulations to investigate filament eruptions, focusing particularly on the 3D structure and genesis of extreme ultraviolet(EUV) waves. Our results demonstrate that the EUV wave front forms a dome-like configuration subdivided into three distinct zones. The foremost zone, preceding the flux rope, consists of fastmode shock waves that heat the adjacent plasma. Adjacent to either side of the flux rope, the second zone contains expansion waves that cool the nearby plasma. The third zone, at the juncture of the first two, exhibits minimal disturbances. This anisotropic structure of the wave front stems from the configuration and dynamics of the flux rope, which acts as a 3D piston during eruptions—compressing the plasma ahead to generate fast-mode shocks and evacuating the plasma behind to induce expansion waves. This dynamic results in the observed anisotropic wave front. Additionally, with synthetic EUV images from simulation data, the EUV waves are observable in Atmospheric Imaging Assembly 193 and 211 ?, which are identified as the fast-mode shocks. The detection of EUV waves varies with the observational perspective: the face-on view reveals EUV waves from the lower to the higher corona, whereas an edge-on view uncovers these waves only in the higher corona.
