Multi-Scale Jets And Related Energy Transportation In The Solar Atmosphere

Jets are one of the most common phenomena occurring within the solar atmosphere through which hot plasma is injected from the chromosphere to the solar corona. They are usually associated with magnetic reconnection, which indicates energy release of solar magnetic filed and transportation from the chromosphere to corona. Solar jets are also often accompanied by flares, coronal mass ejections (CMEs) or radio bursts, which could lead to significant changes of the space weather and terrestrial magnetic field. Thus, studying solar jets could not only deepen our understandings on some basic issues in solar physics, such as the evolution of solar magnetic field and coronal heating, but also help us learn more about the mechanism of solar eruptions to improve our capability in space weather forecasting.Due to limits of the observational technology many issues such as the detailed dynamics of jets, the energy transportation and their interaction with solar atmospheric waves are still unclear. Here, we study two kinds of jets:large-scale and small-scale jets. Large-scale jets are eruptions of large amount of plasma materials (with length ranging from tens to hundreds of mega-meters) in solar corona, triggered from lower solar atmosphere and (always) accompanied by flarings. Small-scale jets are eruptions of small amount plasma materials which are ubiquitous throughout the chromosphere to corona and quasi-periodical triggered. In this thesis, we will systematically present the detailed analysis of them. We expect to make up some blanks in understanding this typical phenomenon and their laws.1. Dynamics of Large-scale JetsPrevious studies have shown that large-scale jets are triggered by magnetic recon-nections at their footpoint regions. The magnetic reconnection not only provides the energy for heating plasmas, but also injects the initial kinetic energy of jets. However, some jets are found to reach a height beyond that it could reach according to the initial speed obtained from the reconnection. Previous studies mostly focus on the trigger-ing mechanism, but ignored the energy releasing process after the reconnection. We firstly present the detailed analysis on a coronal large-scale EUV jet employing the multi-view and multi-wavelength observations from the SDO AIA and STEREO EUVI instruments. We find that the Lorentz force, which comes from continuous untwisting motion of the magnetic field after the reconnection, provides a persistent upward driv-ing force on the jet. During the whole course of the jet event, kinetic energy of the jet obtained from the untwisting motion is about1.6times of that obtained from the initial reconnection. Meawhile, the untwisting motion of the magnetic field could also keep the jet rotating all the way during its off-limb phase. The rotational motion does not show any signature of deceleration during the ascending and descending phase of the jet. We also find that the jet is able to heat the local corona even if only2%of the energy flux it carries dissipates. Thus we believe, a large-scale jet could gain enough energy from the reconnection and untwisting motion to make its possible contribution to local coronal heating.Based on the above results, we further study the rules of magnetic energy release during large-scale jet events. Again using the multi-view and multi-wavelength ob-servations from the SDO AIA and STEREO EUVI instruments, we perform the first observation, analysis and MHD simulation of solar coronal twin jets. A large-scale jet, which exhibits its blowout jet nature, erupts as the preceding jet. Analysis on the ki-netics and energy of the preceding jet reveals that, the kinetic energy of the jet injected by the untwisting motion of the magnetic field is about2.4times of that injected by the initial reconnection. However, the whole process does not stop here. Around the arrival of the preceding jet at the solar surface, two smaller large-scale jets are initiated. All the observational evidences indicate that they share the same triggering process and they are twin jets. Three-dimensional MHD numerical simulation has shown that a sigmoidal structure is formed during the eruption of the preceding jet, and the reconnections be-tween the two arms of the sigmoid and the ambient open fields lead to the eruption of the twin jets. The twins then represent the further free energy release process after the reconnection and untwisting motion of the preceding jet. These results could deepen our knowledge in understanding local magnetic evolution and energy transportation during such events.On the other hand, numerous studies have shown the close relation between large-scale jets and flares. However, is there any connection between jets and CMEs? Are large-scale jets really "harmless" phenomena which only occur in the solar atmosphere and will never affect the terrestrial environments? Via employing the multi-view obser-vations from instruments onboard SDO, STEREO and SOHO, we exhibit the analysis on a large-scale jet event which drives a high-speed CME. The CME erupted with a radial velocity over1000km s-1, which means it could result in large disturbances in solar wind and the interplanetary environment. The driving jet is located right un-derneath the CME. We suggest the situation as that the eruption of the jet pushes a blob-like structure upward and leads to the eruption of the CME. The observational fea-tures of magnetic fields and EUV structures indicate that the jet is triggered by a typical three-dimensional null-point topology, providing the detailed observational evidences for such three-dimensional triggering mechanism of large-scale jets. We also find that the rotational motion of the jet undergoes severe deceleration. The deceleration may be caused by the initial underneath magnetic field topology which leads to little free energy left for driving the rotational motion of the jet, or the loss of angular momentum which has been passed to the CME.2. Interaction of Small-scale Jets with Atmospheric WavesThe term of "small-scale jets" includes type-I spicules, type-II spicules and coro-nal quasi-periodic (QP) mass flows. Previous studies have shown that coronal QP mass flows are resulted from chromospheric type-II spicules, whose triggering mechanism are the same as the above large-scale jets i.e., they are both triggered by reconnections. Due to the ubiquitous nature of QP mass flows, we try to figure out if there will be any interaction between them and another ubiquitous phenomenon-Alfvenic waves. As we know, these Alfvenic waves obtain enough energy flux powerful to heat the corona. Thus, how are these wave energies dissipated? If the propagating Alfvenic waves, which have periods of3-5min and phase speeds around600kms-1, encounter QP density enhancements (QP small-scale jets) which obtain longer periods15min and much slower speed100km s-1, there will be a sequence of reflection and transmission. This process could result in the wave train cascade to turbulence, which will cause the dissipation of wave energy and heating of local corona. Then, does this situation really exist in the corona? Via analyzing the propagation features of Alfvenic waves within37coronal loops, we find that the "Excess of High Frequency FFT power"(EHFF) phenomenon around the apexes of these loops, which could be the potential evidence for the existence of Alfvenic turbulence. Further analysis shows that how much the EHFF phenomenon would be is nearly proportional to the length of loops, consistent with deduction from turbulence theories. Meanwhile, the changes of line widths ob-served within these loops also support the onset of turbulence. Synthesizing all the evidence, we believe that there are ubiquitous turbulence generated via non-linear in-teraction between QP small-scale jets and Alfvenic waves within coronal loops. The results emphasize the role of small-scale jets in coronal heating.Then, do QP small-scale jets play any important role in accelerating high speed solar wind? We analyze14plumes appeared in the antarctic coronal hole on Dec.20th2011using observations from SDO and CoMP. Detailed analysis reveals that QP small-scale jets and Alfvenic perturbations exist simultaneously within all the plume struc-tures. The average amplitude, projected phase speed and period of the perpendicular Alfvenic perturbations are about0.5km s-1,830km s-1and3-5min, respectively. The phase speed and period of the QP small-scale jets are only120km s-1and15min, respectively. The above results reveal that there are ubiquitous QP small-scale jets and Alfvenic perturbations in the lower region of coronal holes. Their existence make the presence of turbulence possible and small-scale jets could also possibly play an impor- tant role in accelerating high-speed solar wind.Besides, we present an event of slow magneto-acoustic waves which are probably generated by QP small-scale jets. These slow magneto-acoustic (MA) waves, which exist simultaneously with QP small-scale jets, occured within the famous solar "Tor-nado" on Sept.25th2011. This is the first observation of such slow MA waves in solar quiescent region. We find the multi-temperature nature of these slow MA wave-their phase speed in171A passband (with higher character temperature) is about101km s-1, while their phase speed in304A passband (with lower temperature) is only70km s-1. Their period is only about50s, which is about1/5-1/10of those observed in coronal holes and active regions. The energy flux carried by any single slow MA wave train is found not to be able to balance the radiative loss of local corona. However, as we find they tend to appear simultaneously, their detailed contribution to local coronal heating is worth to be investigated further.