本文選題：冕震學(xué) + 臘腸模�。� 參考：《山東大學(xué)》2016年博士論文

【摘要】：SOHO, TRACE, Hinode和SDO等衛(wèi)星升空后,在高度結(jié)構(gòu)化的太陽(yáng)大氣中發(fā)現(xiàn)了大量的低頻波動(dòng)和震蕩。波動(dòng)參數(shù)的測(cè)量,結(jié)合日冕磁結(jié)構(gòu)中集體磁流體波動(dòng)模式的理論,即可推測(cè)難以直接測(cè)量的關(guān)鍵日冕物理參數(shù),這就是“冕震學(xué)”的研究?jī)?nèi)容。冕震學(xué)推測(cè)對(duì)象中,Alfven速和大氣結(jié)構(gòu)的橫向密度梯度備受關(guān)注。然而,作為冕震學(xué)的理論出發(fā)點(diǎn),日冕磁結(jié)構(gòu)常被描述成靜態(tài)的、密度由內(nèi)到外是躍變的。本文利用解析和數(shù)值計(jì)算,較為系統(tǒng)地討論了磁結(jié)構(gòu)內(nèi)外流動(dòng)剪切、密度橫向不均勻性對(duì)若干主流冕震學(xué)診斷手段的影響。所取得成果具有如下主要?jiǎng)?chuàng)新點(diǎn)：(1)首次系統(tǒng)討論了流動(dòng)剪切對(duì)磁環(huán)中駐波的效應(yīng),發(fā)現(xiàn)該剪切可顯著影響環(huán)內(nèi)快扭曲�；ＶC模周期比,也可極大限制快臘腸駐波的可觀測(cè)性；(2)首次給出了具有任意橫向密度剖面的磁片結(jié)構(gòu)中快波的色散關(guān)系并對(duì)其做了系統(tǒng)討論,發(fā)現(xiàn)第一支扭曲波受密度分布細(xì)節(jié)影響不大,為以往的冕震學(xué)實(shí)踐提供了理論支撐；但臘腸模及高支扭曲模的特性敏感地依賴于密度分布細(xì)節(jié)；(3)首次探討了具有任意橫向密度剖面的磁環(huán)中脈沖激發(fā)的臘腸行波,其結(jié)果表明,某些活動(dòng)區(qū)磁環(huán)中臘腸行波信號(hào)不存在準(zhǔn)周期相,這與經(jīng)典結(jié)論有定性的區(qū)別。具體描述如下。觀測(cè)表明,不少震蕩的太陽(yáng)大氣磁環(huán)中存在多周期信號(hào)。在冕震學(xué)框架內(nèi),磁環(huán)中駐波基模周期(P1)與第一諧模周期(P2)之比在推斷磁環(huán)介質(zhì)的密度及磁場(chǎng)結(jié)構(gòu)化信息方面起著重要作用�；诠庾V測(cè)量的直接手段與基于冕震學(xué)思想的間接手段都表明磁環(huán)內(nèi)可能存在可觀的場(chǎng)向流。但迄今還少有研究來(lái)系統(tǒng)討論磁環(huán)內(nèi)外流動(dòng)剪切對(duì)周期比這一冕震學(xué)手段的影響。本文第二章數(shù)值求解了帶有流動(dòng)的磁環(huán)中波模的色散關(guān)系,設(shè)計(jì)了一種簡(jiǎn)單的圖形方法來(lái)構(gòu)造駐波,從而首次系統(tǒng)考察了周期比P1/2P2對(duì)磁環(huán)橫縱比(即半徑一環(huán)長(zhǎng)比)、環(huán)內(nèi)流速以及環(huán)內(nèi)外密度比的依賴。對(duì)于冕環(huán),我們發(fā)現(xiàn)流動(dòng)效應(yīng)對(duì)快扭曲模和臘腸模的影響都很大：對(duì)快扭曲模,流動(dòng)會(huì)使P1/2P2比靜態(tài)時(shí)顯著減��；對(duì)快臘腸模,流動(dòng)對(duì)P1/2P2的影響有限,但會(huì)極大縮小支持束縛臘腸駐波的冕環(huán)的參數(shù)范圍。對(duì)于光球磁環(huán),流動(dòng)對(duì)P1/2P2影響較弱,但考慮流動(dòng)效應(yīng)會(huì)為光球磁結(jié)構(gòu)中臘腸模多周期現(xiàn)象的觀測(cè)提供額外的理解方式。相對(duì)于磁環(huán)幾何,磁片幾何在解釋若干太陽(yáng)大氣磁結(jié)構(gòu)中集體波模(如白光觀測(cè)所發(fā)現(xiàn)的冕流波)的觀測(cè)方面更為適用。已有研究多假定磁片內(nèi)外密度呈階躍式變化。顯然密度的橫向連續(xù)變化更為現(xiàn)實(shí),但其效應(yīng)還少有研究。本文第三章在冷磁流體力學(xué)框架下,首次解析給出了具有任意橫向密度剖面的日冕磁片中集體快波所滿足的色散關(guān)系,并進(jìn)而系統(tǒng)討論了連續(xù)橫向密度分布對(duì)日冕磁片中駐立扭曲模和臘腸模色散特性的影響。此外還通過(guò)數(shù)值求解相應(yīng)的時(shí)變快波方程,說(shuō)明了我們所關(guān)注的解析色散關(guān)系的解有其明確的物理意義。我們發(fā)現(xiàn),至少對(duì)幾種常用的橫向密度剖面,對(duì)任意軸向波數(shù),第一支扭曲�？偸潜皇`在磁片內(nèi)。當(dāng)軸向波數(shù)的取值在觀測(cè)范圍內(nèi)時(shí),與階躍情形相比,引入密度剖面的連續(xù)分布所帶來(lái)的該支扭曲模周期的變化不超過(guò)13%。但軸向波數(shù)較小時(shí),臘腸模和其他支扭曲模是泄漏的,且其周期和衰減時(shí)間嚴(yán)重依賴于橫向密度分布的描述。只有在耀斑環(huán)這類高密度比的磁結(jié)構(gòu)中,這些模式的衰減才足夠弱,以至于可被觀測(cè)到�？傮w上看,對(duì)第一支扭曲模來(lái)說(shuō),階躍剖面的色散關(guān)系在計(jì)入橫向密度連續(xù)變化時(shí)仍大致適用；但對(duì)臘腸模和其他支扭曲模來(lái)說(shuō),其研究需要考慮橫向密度分布的細(xì)節(jié)。近期紫外、可見(jiàn)光及射電觀測(cè)表明,冕環(huán)中常出現(xiàn)準(zhǔn)周期行波。從直觀上講,行波的這類準(zhǔn)周期性可能來(lái)自激發(fā)源的準(zhǔn)周期行為。但事實(shí)上,由于磁環(huán)中集體模式的色散,脈沖源也可導(dǎo)致行波的準(zhǔn)周期性,此時(shí)集體模式軸向群速度(vgr)對(duì)角頻率(ω)的依賴決定了行波的時(shí)變特征。由于其強(qiáng)色散性,束縛臘腸模在這一機(jī)制中備受關(guān)注。已有研究往往假定磁環(huán)內(nèi)外密度呈階躍式變化,此時(shí)隨著ω的增加,束縛臘腸模的強(qiáng)先迅速下降繼而緩慢增加,而這一非單調(diào)性是行波信號(hào)中存在準(zhǔn)周期相的原因�；谖覀円酝镁哂腥我饷芏绕拭娴拿岘h(huán)中臘腸波的色散關(guān)系,本文第四章討論了橫向連續(xù)密度剖面對(duì)脈沖激發(fā)的臘腸行波的影響。對(duì)于拋物剖面,無(wú)論環(huán)內(nèi)外密度比以及密度橫向變化尺度如何,群速度vgr對(duì)ω的依賴與階躍剖面的經(jīng)典結(jié)果都定性類似。換言之,如果磁環(huán)密度剖面可用拋物剖面刻畫,那么脈沖激發(fā)的快臘腸行波信號(hào)總是包含準(zhǔn)周期相。對(duì)線性剖面,群速度vgr隨ω的變化對(duì)環(huán)內(nèi)外密度比以及密度橫向變化尺度有著復(fù)雜的依賴關(guān)系。對(duì)于較小的橫向密度尺度,無(wú)論密度比如何,vgr-ω曲線的總體行為總與階躍情形類似。但對(duì)于較大的橫向密度尺度(換句話說(shuō),較為彌散的冕環(huán)),當(dāng)密度比較小時(shí),vgr-ω曲線呈單調(diào)變化,此時(shí)脈沖激發(fā)的快臘腸行波信號(hào)中不再存在準(zhǔn)周期相。而當(dāng)密度比較大時(shí),vgr-ω曲線呈現(xiàn)多個(gè)極值。對(duì)同時(shí)存在一個(gè)極小和極大值的情形,我們的細(xì)致討論表明,此時(shí)準(zhǔn)周期相的持續(xù)時(shí)間、準(zhǔn)周期相中信號(hào)的時(shí)變與小波譜特征都與階躍情形不同�？傮w上說(shuō),對(duì)冕環(huán)中脈沖激發(fā)的快臘腸行波信號(hào)而言,冕環(huán)橫向密度剖面的描述及其細(xì)節(jié)有著重要的影響。反過(guò)來(lái)說(shuō),這意味著快臘腸行波信號(hào)的細(xì)致測(cè)量可用來(lái)推測(cè)冕環(huán)橫向密度剖面的細(xì)節(jié)。
[Abstract]:After the SOHO, TRACE, Hinode and SDO satellites are lifted, a large number of low frequency fluctuations and oscillations have been found in the highly structured solar atmosphere. Measurement of the fluctuation parameters and the theory of the wave mode of the collective magnetic fluid in the coronal magnetic structure can be used to speculate the key coronal physical parameters which are difficult to be measured directly. This is the study of "coronal earthquake". In the conjecture of coronal seismology, the Alfven velocity and the transverse density gradient of the atmospheric structure are concerned. However, as the starting point of the coronal seismology, the coronal magnetic structure is often described as static, and the density is leaped from inside to outside. In this paper, the internal and external shear and transverse density of the magnetic structure are systematically discussed by analytical and numerical calculations. The effect of inhomogeneity on the diagnostic methods of several mainstream coronal seismology. The results obtained are as follows: (1) the effect of the flow shear on the standing wave in the magnetic ring is discussed for the first time. It is found that the shear can significantly affect the periodic ratio of the basic mode harmonic mode in the ring, and can greatly limit the observability of the fast sausage standing wave; (2) the first time The dispersion relation of the fast wave in the magnetic sheet structure with arbitrary transverse density profile is given and a systematic discussion is given. It is found that the first twisted wave is less influenced by the details of density distribution, which provides theoretical support for the previous practice of coronal seismology; but the characteristics of the sausage mold and the high branch distortion die are sensitive to the details of the density distribution; (3) first. The results show that there is no quasi periodic phase in the traveling wave signal of the sausage in some active region magnetic rings, which is qualitatively different from the classical conclusion. The detailed description is as follows. The observations show that there are many periodic signals in many oscillating solar magnetic rings. The ratio of the base mode period (P1) and the first mode period (P2) in the magnetic ring plays an important role in inferring the density of the magnetic ring and the structural information of the magnetic field. The direct means based on the spectrometric measurement and the indirect means based on the theory of coronal seismology indicate that there may be a considerable field flow in the magnetic ring. But there are few studies to date. In the second chapter, a simple graphical method is designed to construct a standing wave. In this paper, a simple graphical method is designed to construct a standing wave, and for the first time, the cycle ratio of the P1/ 2P2 to the magnetic ring is investigated. For the coronal ring, we find that the flow effect has a great effect on the fast twisting die and the sausage mold: the flow will significantly reduce the P1/2P2 than the static mode for the fast warping die; the effect of the flow on the P1/2P2 is limited, but it will greatly reduce the parameters that support the coronal ring that supports the shackle of the sausage standing wave. The effect of flow on P1/2P2 is weak, but considering the flow effect will provide an additional understanding of the observation of the multiple periodic phenomena of the Dachshund model in the magnetic structure of the sphere. In the third chapter, the dispersion relation of the group fast wave in the coronal magnetic sheet with arbitrary transverse density profiles is given for the first time in the frame of cold magnetic fluid mechanics. Furthermore, the influence of the continuous transverse density distribution on the dispersion characteristics of the stationary distortion mode and the sausage model in coronal magnetic disc is discussed. In addition, the corresponding time-varying fast wave equation is solved by numerical calculation. It is shown that the solution of the analytical dispersion relation we have concerned has its clear physical meaning. We find at least several common transverse density profiles. For any axial wave number, the first twist die is always bound to the magnetic sheet. When the value of the axial wave number is in the range of observation, the variation of the period of the branch of the branch caused by the continuous distribution of the density profile is not more than 13%., but the axial wave number is less than the axial wave number, and the sausage die and the other branches of the branch are leaked. The period and time of attenuation depend heavily on the description of the distribution of transverse density. Only in the magnetic structure of the high density ratio of the flare ring, the attenuation of these modes is so weak that it can be observed. In general, the dispersion relation of the step section is still generally applicable to the first twist mode when the transverse density is taken into account. But for the dachshunds and other branches of the warp, it is necessary to consider the details of the distribution of transverse density. In the near future, UV, visible and radio observations show that quasi periodic traveling waves often occur in the coronal rings. The dispersion, the pulse source can also lead to the quasiperiodicity of the traveling wave. At this time, the dependence of the collective mode axial group velocity (vGr) on the angular frequency (omega) determines the time-varying characteristic of the traveling wave. Due to its strong dispersion, the bound sausage die has attracted much attention in this mechanism. In the fourth chapter, the effect of the transverse continuous density profile on the pulse excited sausage waves is discussed in the fourth chapter. On the parabolic profile, the dependence of the group velocity vGr on Omega is similar to the classical results of the step section, regardless of the density ratio and the lateral density. In other words, if the magnetic ring density profile can be depicted with a parabolic profile, the pulse excited fast sausage traveling wave signal always contains quasi periodic phase. The degree vGr has a complex dependence on the density ratio of the inner and outer density and the scale of the density. For the smaller transverse density scale, the overall behavior of the vgr- Omega curve is similar to the step situation regardless of the density ratio. But for the larger transverse density scale (in other words, the more dispersed coronal rings), when the density is smaller When the vgr- Omega curve is monotonically changing, the quasi periodic phase is no longer in the fast salami traveling wave excited by the pulse. And when the density is large, the vgr- Omega curve presents multiple extremes. For the case of a minimum and maximum value, our detailed discussion shows that the duration of the quasi periodic phase and the time variation of the signal in the quasi periodic phase are shown at this time. The characteristics of the small wave spectrum are different from the step conditions. In general, the description and details of the transverse density profile of the coronal ring have an important influence on the fast sausage traveling wave signals excited by the coronal rings. In turn, this means that the careful measurement of the fast sausage traveling wave signal can be used to speculate on the details of the transverse density profile of the coronal ring.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P182

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