Small-scale Jets In The Solar Lower Atmosphere And Their Association With Coronal Plumes

The photospheric magnetic network is the dominant magnetic structure in quiet sun(including the quiet region and coronal holes),and its thermodynamics is an important aspect to understand the transport processes of energy and mass in the solar atmosphere.It has been observed that jets or jet-like structures with different thermodynamic characteristics commonly exit in network region,including jets in chromosphere(e.g.,spicules),network jets in transition region and coronal plumes.It has been shown that there is a one-to-one correspondence between some of small-scale jets in the solar lower atmosphere and propagating disturbances in coronal plume,suggesting there is some intrinsic correlation between low-atmospheric jets and the increase in energy or mass in coronal plumes,which is an important clue to understand the energy and mass transport processes in the solar atmosphere.First,based on observational data,the thesis distinguishes between network region with and without obvious coronal plumes,and uses an automated method to identify and track low-atmospheric jets to identify and analyze their dynamical characteristics in order to clarify what kind of low-atmospheric jets corresponds to coronal radiation enhancement(i.e.,energy or mass increase).Then,the thesis carries out numerical computations based on magnetohydrodynamics,and discusses the possible physical processes of the low-atmospheric jets affecting the corona.Firstly,combining the Solar Dynamics Observatory(SDO)AIA 171(?)(coronal temperature,used to certify the coronal plume)and the Transition Region Imaging Spectrograph(IRIS)1330 A(transition region temperature,used to certify transition region network jets),the thesis investigates the dynamics of transition region network jets in network region with and without coronal plumes.In this observation region,coronal plume only root in a portion of the network region,however,transition region network jets are prevalent above all network region.Based on the spatial distribution of coronal plumes,we classify the network region into two categories,those where coronal plumes are clearly visible(R1 and R2)and those where coronal plumes are weak or almost invisible(R3 and R4).Furthermore,while magnetic features in all these regions are dominated by positive polarity,they are more compact(suggesting stronger convergence)in R1 and R2 than that in R3 and R4.We develop an automated method to identify and track the network jets in the regions.In the regions rich in coronal plumes(i.e.R1 and R2),the average lifetimes,heights and speeds of all 619 network jets are 45.6 s with a standard deviation(1σ)of 35.0 s,8.1" with 1σ of 1.6" and 131 km s-1 with 1σ of 64 km s-1,respectively.In the regions poor in coronal plumes(i.e.R3 and R4),the average lifetimes,heights and speeds of all 674 network jets are 50.2 s with 1σ of 35.4 s,5.5" with 1σ of 1.9" and 89 km s-1 with 1σ of 45 km s-1,respectively.On average,the network jets from regions rich in coronal plumes are higher and faster than that from the regions poor in coronal plumes,indicating that network regions producing stronger coronal plumes also tend to produce more dynamic network jets.Then,using observations from the SDO/AIA 171(?) band and the 1-meter New Vacuum Solar Telescope(NVST)of the Fuxian Lake Solar Observatory in the Hα bias band(-0.6 (?),used to identify chromospheric structures).We investigate dynamics of chromospheric jets occurring above the network region with different coronal responses.With an automated method,we identify and track 1320 Ha jets in network regions,which the average lifetime,height and ascending speed of the Ha jets are 75.38 s,2.67 Mm,65.60 km s-1,respectively.The number of Ha jets is～58 per network region at any given time.Similarly,the Hα jets are classified into two categories and are studies their dynamics based on the presence or absence of distinct coronal plume structures.We find that Ha jets rooted in the footpoint regions of coronal plumes have an average lifetime of 76.1±35.0 s,an average height of 3.01±1.07 Mm and an average ascending velocity of 81.2×48.3 km s-1.While the Hα jets in the rest regions are having an average lifetime of 75.0±32.0 s,an average height of 2.48±0.95 Mm and an average ascending velocity of 56.9±36.3 km s-1,these results show that the Ha jets associated with coronal plumes are on average higher and more dynamic than those not with coronal plumes.We also find that propagating disturbances(PDs)in coronal plumes have a close connection with the Ha jets.The speeds of 28 out of 29 Ha jets associated with PDs are>50 km s-1.In a case of coronal jet,we find that the speeds of both the coronal jet and the Ha jet are over 150 km s-1,suggesting that both cool and hot jets can be coupled together.Based on our analyses,it is evident that more dynamic Hα jets could release the energies to corona in some way or another.Finally,to discuss how the energy in low-atmospheric jet is released into the upper corona,we use the PLUTO to numerically solve the system of magnetohydrodynamic(MHD)equations in a two-dimensional coordinate system,which is based on a layered solar model of the solar atmosphere.We inject transient vertical velocity pulses in the low chromosphere to form chromospheric jets,and investigate theirs evolution and theirs effect on the corona.The results of the numerical simulations show that the chromospheric jet is a very powerful tool for the development of the corona.The results of numerical simulations show that the instantaneous velocity pulse injected at the bottom of the chromosphere steepens into rebound shock,and lifts the chromosphere and transition plasma to form jet structures.Under the same initial conditions,the larger initial velocity pulse is,the faster jets are and the higher jets reach.Moreover,the greater the compression ratio in shock,the more temperature increase caused at a given height.So it is easier to observe coronal structures as the increase of temperature in corona.This is consistent with our observation that the the more energy small-scale jets in the lower atmospheric correspond to the coronal structures.Therefore,we believe that the more energy small-scale lower atmosphere jets may release more energy by shock to reach the corona through the transition region.At the same time,we suggest that chromospheric jets,transition region network jets correspond well to ray-like features in corona.And we suggest that they may be coherent phenomena,and they are important tunnels for cycling energy and mass in the solar atmosphere.