本文選題：木星　切入點：磁層　出處：《中國科學(xué)技術(shù)大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：木星是太陽系中最大的行星,有著最快的自轉(zhuǎn)角速度和最強(qiáng)的磁場,并與其周圍的多顆衛(wèi)星構(gòu)成木星系。木星磁層在太陽風(fēng)作用下包裹著木星,范圍遠(yuǎn)超過伽俐略衛(wèi)星的軌道,因此磁層活動不僅與太陽風(fēng)相關(guān),還受到磁層內(nèi)衛(wèi)星的影響。當(dāng)磁層中物理過程產(chǎn)生高能粒子沿磁力線轟擊木星電離層時就形成了木星極光,其按形態(tài)主要分為三類:明亮的主極光卵、衛(wèi)星足跡和極區(qū)輻射。主極光卵目前認(rèn)為與磁層共轉(zhuǎn)破裂密切相關(guān),衛(wèi)星足跡直接反映了磁層與衛(wèi)星的作用過程,而極區(qū)輻射變化較復(fù)雜,反映了中遠(yuǎn)磁尾多變的磁層活動。本文介紹了木星磁層的現(xiàn)有研究成果,擴(kuò)展了具有離心力效應(yīng)的木星穩(wěn)態(tài)磁場模型,并在該磁場模型的基礎(chǔ)上對木星磁層進(jìn)行了初步研究。木星極光中極區(qū)輻射的具體形成過程頗有爭議,我們提出一個簡單且合理的極區(qū)輻射的發(fā)生原因一一中遠(yuǎn)磁尾處的磁力線擾動扭曲。Hill等人提出了木星磁層較差自轉(zhuǎn)的角速度分布,本文認(rèn)為在中遠(yuǎn)磁尾處角速度差異較大,相鄰磁通量管受擾動易扭曲形成渦旋結(jié)構(gòu)。通過具體的模擬分析顯示,赤道面上大約54Rj(Rj=71,400km是木星半徑)到59Rj的圓柱區(qū)域受擾動形成渦旋結(jié)構(gòu)所引發(fā)的數(shù)十萬安培電流注入到極區(qū)電離層,就可以形成大約半度大小的極區(qū)輻射,因此可以認(rèn)為不同的擾動區(qū)域?qū)?yīng)著極區(qū)輻射的不同亮斑,而亮度反映著扭曲的劇烈程度。木衛(wèi)二的極光足跡是本文研究的關(guān)注點。木衛(wèi)二在木星磁層中運(yùn)動,與快速共轉(zhuǎn)的木星磁場相互作用形成木星極光中木衛(wèi)二的尾跡,此尾跡反映了連續(xù)擾動的磁通量管對木星電離層電流注入的過程。連接木衛(wèi)二的磁通量管相對磁層而言尺度很小,因此可以應(yīng)用細(xì)絲理論模擬木衛(wèi)二運(yùn)動引起的極光演化過程。模擬結(jié)果表明,未擾動的上游磁通量管經(jīng)過大約720s的時間在木衛(wèi)二拉伸作用下形成角度約為4°且相對于木衛(wèi)二靜止的拉伸磁通量管,當(dāng)其脫離木衛(wèi)二時在磁張力的作用下加速,在隨后大約2160s的加速時間內(nèi),磁通量管的速度逐漸與背景磁力線接近。與此同時,磁通量管向木星電離層注入的電流也由9×105A逐漸衰減至0,以1/e初始電流處認(rèn)為是可觀測的木衛(wèi)二尾跡限度,則木衛(wèi)二的尾跡僅大約有一至兩個經(jīng)度,這與哈勃望遠(yuǎn)鏡觀測到的木衛(wèi)二尾跡大小大致相同。從能量角度考慮,木衛(wèi)二尾跡總的輸送能量約為2.3×1013J,比木衛(wèi)一輸送的能量小一個量級,這是導(dǎo)致尾跡長度遠(yuǎn)小于木衛(wèi)一的重要原因,同時也發(fā)現(xiàn)木衛(wèi)二附近的壓力凹槽對結(jié)果影響不大,可以忽略。木星磁層中的磁通量管在太陽風(fēng)壓力下和離心力作用下有復(fù)雜運(yùn)動,在研究極區(qū)輻射的過程中我們進(jìn)一步分析重聯(lián)的磁通量的來源,同時還發(fā)現(xiàn)使用的磁場模型在低磁緯(Λ50°)磁場與觀測基本符合,而高磁緯(Λ≥50)磁場與觀測相比向外膨脹,特別是遠(yuǎn)磁尾區(qū)域膨脹更明顯,不符合經(jīng)驗認(rèn)識,需要優(yōu)化其磁場位形。本文先利用熵參量來判定磁層的穩(wěn)定性,熵參量PV5/3被廣泛應(yīng)用于分析磁層等離子體片中的輸運(yùn)問題,其中P是壓力,V是單位磁通量管的體積,通過熵參量的分布和變化可以判斷磁層的穩(wěn)定性及揭示磁層中的動力學(xué)過程。對木星磁層的計算結(jié)果表明,磁層在55Rj內(nèi)熵參量呈上升趨勢,而之后有所下降,表明該模型在55Rj之外已經(jīng)不穩(wěn)定,這也證實了高磁緯的磁場位形需要優(yōu)化。同時假想的磁場重聯(lián)后的單位磁通量管的熵參量分布表明赤道面中遠(yuǎn)磁尾的磁場重聯(lián)是由尾向輸運(yùn)的磁力線管拉伸斷裂重聯(lián)引起的。在隨后的工作中為了優(yōu)化磁場位形,我們在保持赤道面壓力分布不變的條件下,采用坐標(biāo)變換的方法改變磁矢勢的分布,使中遠(yuǎn)磁尾磁場特別是高磁緯磁場向赤道面壓縮。變換后的磁場位形與原模型相比,低磁緯位形基本不變,高磁緯則大幅壓縮,更符合經(jīng)驗知識。
[Abstract]:Jupiter is the largest planet in the solar system, with the fastest rotation velocity and the strongest magnetic field, and many satellites around Jupiter and Jupiter form. The magnetic layer in the solar wind wrapped under Jupiter, far more than the range of Galileo satellite orbit, so the magnetosphere with the solar wind activity is not only related to it affected by the magnetic layer within the satellite. When the physical magnetic layer produced in the process of high-energy particle bombardment of Jupiter ionosphere along the magnetic field on the formation of the Jovian Aurora, according to its morphology is mainly divided into three categories: the main bright auroral and polar satellite footprint, radiation. The main auroral oval currently considered and magnetospheric corotation rupture closely related. The satellite footprint directly reflects the effect of magnetic layer and satellite process, while polar radiation change is complex, reflecting the changing of COSCO magnetotail magnetic layer. This paper introduces the existing research results of the jovian magnetosphere, extended with centrifugal force. Jupiter should the steady-state magnetic field model, and made a preliminary study on Jupiter's magnetosphere based on the magnetic field model. The specific region in the process of the formation of the Jovian auroral radiation controversial, we propose a simple and reasonable polar radiation causes one end of the magnetic disturbance COSCO magnetic distortion of.Hill et al. Proposed angular velocity Jupiter's magnetosphere differential rotation distribution, the larger magnetic tail angular velocity in COSCO between adjacent flux tubes disturbed easily distorted vortex structure. Through the simulation analysis shows that about 54Rj of the equatorial plane (Rj=71400km is the radius of Jupiter) disturbance caused by the formation of the vortex structure of hundreds of thousands of amperes of current injected into the polar region the ionosphere to the cylindrical region of 59Rj, polar radiation can form about half the size, so that the disturbance of different regions of the corresponding region of different radiation The light spot brightness reflects the severity of the distortion. Europa's aurora footprint is a focus of this study. Europa movement in Jupiter's magnetosphere, the formation of the Europa Jupiter in the aurora wake and fast interaction were transferred to Jupiter's magnetic field, the wake reflects the process of implantation on Jupiter ionospheric current flux continuous disturbance the magnetic flux tube. The tube connecting Europa relative magnetic layer scale is very small, so it can be used fine theoretical simulation movement caused by the evolution of Aurora Europa. Simulation results show that the upstream flux of undisturbed tube after about 720s hours in Europa under tension forming angle of approximately 4 degrees relative to the tensile and magnetic flux Ganymede two stationary tube, when the detachment in Europa magnetic tension under the effect of acceleration, then about 2160s acceleration time, magnetic flux tube speed gradually and magnetic background Close to the line. At the same time, the current magnetic flux tube into the ionosphere to Jupiter from 9 * 105A to 1/e gradually decreases to 0, the initial current that is observable wake limit Europa, Europa is wake only about one or two longitude, and the size of Europa wake Harbert telescope observed roughly the same. Considering from the perspective of energy, the total energy transfer from Europa wake is about 2.3 * 1013J, bimu Wei of the energy delivered one order, which is an important cause of the wake length is far less than IO, also found little effect of pressure on the groove near Europa can be ignored. The magnetic flux in the magnetic layer of the tube with Jupiter the complex motion in the solar wind pressure and centrifugal force, in the process of polar radiation we further analyze the sources of heavy magnetic flux coupling, but also found that the use of the model in low magnetic field Weft (a 50 DEG) magnetic field accorded with observation, and high latitude (lambda = 50) compared with the observed magnetic field expansion, especially in the distant magnetotail region expansion is more obvious, with experience, needs to optimize the configuration of the magnetic field. This paper first use of entropy to determine the stability of the magnetic layer, the entropy parameter PV5/3 is widely used in the analysis of transport problem in the plasma sheet magnetic layer, where P is the pressure, V is the unit of magnetic flux tube volume, through the distribution and change of entropy can determine the stability of the magnetic layer and reveal the dynamic process in the magnetosphere. The magnetosphere of Jupiter on the calculation results show that the magnetic layer in 55Rj entropy parameter increased, and then decreased, showed that the model in 55Rj is not stable, which also confirmed the high latitude magnetic field configuration needs to be optimized. At the same time entropy parameters distribution of imaginary magnetic unit magnetic flux contact after the measuring tube shows that the equatorial plane of COSCO The magnetotail magnetic reconnection is from the tail to the transport of magnetic flux tube tensile fracture reconnection. In subsequent work in order to optimize the configuration of the magnetic field, we keep the equatorial surface pressure distribution under the same conditions, using the coordinate transformation method, change the distribution of the magnetic vector potential, the long tail magnetic especially high latitude magnetic field to the equatorial magnetic field compression. After transformation compared with the original model, the low magnetic latitude position unchanged, high latitude is substantially reduced, more in line with the experience and knowledge.

【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：P185.4

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