本文選題：準(zhǔn)垂直激波 + 準(zhǔn)平行激波　； 參考：《中國(guó)科學(xué)技術(shù)大學(xué)》2016年博士論文

【摘要】：無碰撞激波是宇宙空間中常見的物理現(xiàn)象,并且是有效的高能粒子加速器,特別是在宇宙中的大尺度高強(qiáng)度的無碰撞激波可以將帶電粒子加速到相當(dāng)高的能量,形成銀河宇宙射線、異常宇宙射線等等。在本文中,我們利用二維混合模擬研究了準(zhǔn)垂直激波和準(zhǔn)平行激波中波動(dòng)的激發(fā)、結(jié)構(gòu)的演化和粒子動(dòng)力學(xué)過程。具體結(jié)論如下：1.低馬赫數(shù)準(zhǔn)垂直激波情形下游粒子環(huán)狀速度分布低馬赫數(shù)準(zhǔn)垂直激波情形下,上游質(zhì)子穿越激波面后會(huì)形成環(huán)狀速度分布,環(huán)狀速度分布所帶來的平均速度的擾動(dòng),使得磁場(chǎng)也會(huì)產(chǎn)生對(duì)應(yīng)的擾動(dòng)來保證總壓力平衡。我們利用二維混合模擬得到了這樣的結(jié)果,并同時(shí)加入了4%的氮離子,來研究氮離子的環(huán)狀速度分布對(duì)磁場(chǎng)結(jié)構(gòu)的影響。發(fā)現(xiàn)由于粒子數(shù)比較小,氦離子并沒有對(duì)質(zhì)子的環(huán)狀速度分布和磁場(chǎng)結(jié)構(gòu)帶來明顯的影響：并且,由于氦離子的荷質(zhì)比較小，，氦離子在速度相空間中的環(huán)狀速度分布的半徑要比質(zhì)子的大,同時(shí)持續(xù)的時(shí)間要比質(zhì)子的更久。2.準(zhǔn)垂直激波下游波動(dòng)和粒子速度分布的演化利用二維混合模擬,我們研究了準(zhǔn)垂直激波下游波動(dòng)的激發(fā)。低馬赫數(shù)激波情形下,質(zhì)子和氦離子穿越激波面之后均會(huì)在相空間中形成環(huán)狀速度分布；質(zhì)子的環(huán)狀速度分布很快被磁場(chǎng)的擾動(dòng)所破壞,不能激發(fā)離子回旋波；而對(duì)于氦離子,其破壞過程較慢,直到較遠(yuǎn)的下游,氦離子才開始激發(fā)回旋波,這些波動(dòng)將氮離子自身散射成為球殼狀速度分布,并最終散射成為雙麥克斯韋分布；質(zhì)子和氦離子的等離子體β較小,所以沒有磁鏡波的激發(fā)。中等馬赫數(shù)激波情形下,質(zhì)子和氦離子穿越激波面后同樣出現(xiàn)了環(huán)狀速度分布,同時(shí)也出現(xiàn)了少量的反射質(zhì)子；質(zhì)子和氮離子均在激波面下游激發(fā)了離子回旋波,但是質(zhì)子是從激波面就開始激發(fā)離子回旋波,而氮離子直到較遠(yuǎn)的下游才開始激發(fā)離子回旋波,這些波動(dòng)將氮離子散射成為了球殼狀速度分布,并最終散射成為了雙麥克斯韋分布；同樣由于較小的等離子體夕,并沒有磁鏡波的激發(fā)。高馬赫數(shù)激波情形下,質(zhì)子和氮離子也同樣出現(xiàn)了環(huán)狀速度分布,但是很快即被破壞掉,同時(shí)也出現(xiàn)較大比例的反射粒子：質(zhì)子和氮離子均從激波面即開始激發(fā)離子回旋波；氮離子也同樣在下游被散射成為了球殼狀速度分布,并最終被散射成為了雙麥克斯韋分布,但是卻不能肯定是來自氦離子激發(fā)的離子回旋波的貢獻(xiàn),即不能肯定氮離子激發(fā)的離子回旋波在下游是占主導(dǎo)的；粒子在下游加熱較快,等離子體β增長(zhǎng)也較快,下游有磁鏡波的激發(fā)。3.二維準(zhǔn)平行激波中的粒子動(dòng)力學(xué)和下游高速流的產(chǎn)生準(zhǔn)平行激波中運(yùn)動(dòng)到上游的反射粒子與上游入射粒子相互作用可以激發(fā)上游低頻波動(dòng)。這些上上游波動(dòng)會(huì)與激波面相互作用,使得激波面變得并不平整,即布滿了漣漪。上游波動(dòng),或者說漣漪,使得沿著激波面的重構(gòu)過程并不協(xié)調(diào)統(tǒng)一,同時(shí)也使得沿激波面的粒子動(dòng)力學(xué)過程也變得不同。在激波面漣漪的兩側(cè),由于電磁場(chǎng)結(jié)構(gòu)的不同,粒子動(dòng)力學(xué)過程也不同,在漣漪的下半側(cè),會(huì)有較多的粒子被反射和加速,而在漣漪上半側(cè),粒子更傾向于直接穿越激波面,并形成下游冷的高速粒子束流。并且,從我們?cè)敿?xì)研究了我們模擬中出現(xiàn)的下游高速流,發(fā)現(xiàn)模擬中出現(xiàn)的下游高速流與地球舷激波磁鞘中觀測(cè)到的高速流的特征是相似的。4.二維準(zhǔn)平行激波中的粒子加速過程利用二維混合模擬,我們發(fā)現(xiàn),被激波反射的粒子首先會(huì)緊貼激波面運(yùn)動(dòng),并同時(shí)被加速,這是第一階段的加速；之后,粒子獲得了較大的能量,可以到達(dá)靠近激波面的上游,并被束縛在上游波動(dòng)和激波面之間被加速,這是第二階段的加速。經(jīng)過兩個(gè)加速階段,部分粒子運(yùn)動(dòng)到激波遠(yuǎn)下游,部分運(yùn)動(dòng)到遠(yuǎn)上游。還有部分粒子可經(jīng)歷第三個(gè)階段的加速過程,即粒子在上下游波動(dòng)之間來回彈跳并被加速,這一加速過程類似激波擴(kuò)散加速；經(jīng)過三個(gè)加速階段的粒子的最終能量是明顯大于經(jīng)過兩個(gè)階段加速的粒子能量的,并且經(jīng)過三個(gè)階段的粒子也有兩個(gè)部分,一部分運(yùn)動(dòng)到遠(yuǎn)下游,另一部分運(yùn)動(dòng)到遠(yuǎn)上游。
[Abstract]:Collisionless shock is a common physical phenomenon in cosmic space, and is an effective high-energy particle accelerator. In particular, large scale and high intensity collisionless shock waves in the universe can accelerate charged particles to quite high energy, form galactic cosmic rays, abnormal cosmic rays and so on. In this paper, we use two-dimensional mixed simulation. The excitation, structure evolution and particle dynamics process of quasi vertical shock and quasi parallel shock wave are studied. The concrete conclusions are as follows: 1. low Maher number quasi vertical shock waves in the case of low Maher number quasi vertical shock waves in the lower reaches of the downstream particles, when the upstream protons cross the shock surface will form a circular velocity distribution, and the annular velocity can be divided. The disturbance caused by the average velocity of the cloth makes the magnetic field produce corresponding disturbances to ensure the balance of the total pressure. We get this result by a two-dimensional mixed simulation and add 4% of the nitrogen ions to study the ring velocity distribution of nitrogen ions on the structure of the magnetic field. There is a significant effect on the annular velocity distribution and the structure of the magnetic field. And because the charge of helium ions is smaller, the radius of the annular velocity distribution of helium ion in the velocity phase is larger than that of the proton, while the lasting time is longer than the proton, and the evolution of the.2. quasi vertical shock wave and the particle velocity distribution is better than that of the proton. In the two-dimensional mixed simulation, we study the excitation of the downstream wave in the quasi vertical shock wave. In the case of low Maher number shock, the circular velocity distribution of the proton and helium ions across the shock surface will be formed in the phase space; the circular velocity distribution of the proton is quickly destroyed by the disturbance of the magnetic field and can not excite the ion cyclotron wave; and for the helium ion, The damage process is slow, until the farther downstream, the helium ions begin to excite the cyclotron wave, which scatters the nitrogen ions themselves into the spherical shell velocity distribution, and eventually scatters into a double Maxwell distribution; the plasma beta of the proton and helium ions is smaller, so there is no excitation of the magnetic mirror wave. In the middle Maher shock case, protons When the helium ions pass through the shock surface, there is a circular velocity distribution as well as a small amount of reflected protons. Both proton and nitrogen ion excite the ion cyclotron wave at the lower reaches of the shock surface, but the proton begins to excite the ion cyclotron wave from the shock surface, and the nitrogen ions start to excite the ion cyclotron waves until the farther downstream. The wave scatters the nitrogen ions into the spherical shell velocity distribution, and eventually scatters into a double Maxwell distribution; also because of the small plasma Eve, there is no excitation of the magnetic mirror wave. In the high Maher shock case, the proton and nitrogen ions also appear ring velocity distribution, but they are quickly destroyed and also appear more. A large proportion of the reflected particles: the proton and the nitrogen ion all start to excite the ion cyclotron wave from the shock surface, and the nitrogen ions are also scattered into the spherical shell velocity distribution in the downstream, and eventually scattering into the double Maxwell distribution, but it is not sure that the contribution of the ion cyclotron waves from the helium ion excitation is not sure. The ion cyclotron waves excited by nitrogen ions are dominant in the lower reaches; the particles are heated downstream faster, the plasma beta increases faster, and the downstream magnetic mirror waves are excited by the.3. two-dimensional quasi parallel shock wave and the downstream high-speed flow produces the interaction between the reflected particles moving to the upstream and the upstream incident particles in the quasi parallel shock wave. The upstream fluctuations can stimulate the low frequency fluctuations in the upstream. These upstream waves interact with the shock surface, making the shock surface uneven, that is, ripples. The upstream fluctuations, or ripples, make the process of the reconstruction of the shock surface uncoordinated and the particle dynamics along the exciting surface becomes different. On both sides of the ripples, the particle dynamics process is different because of the difference in the structure of the electromagnetic field. In the lower half of the ripples, more particles will be reflected and accelerated, and in the upper half of the ripples, the particles tend to cross the shock surface and form the downstream cold high speed particle beam. And we have studied the bottom of our simulation in detail. It is found that the characteristics of the high velocity flow of the downstream high velocity flow in the simulation and the high velocity flow observed in the earth's starboard shock magnetic sheath are similar to the particle acceleration in the.4. two-dimensional quasi parallel shock wave. We find that the particles reflected by the shock wave first adhere to the excited wave surface and are accelerated at the same time. This is the first stage. After that, the particle gets greater energy and reaches the upstream of the shock surface and is bound between the upstream wave and the shock surface is accelerated. This is the acceleration of the second stage. After two acceleration stages, some particles move to the far downstream of the shock wave, and the part moves to the far upstream. And some particles can go through third stages. The acceleration process, that is, the particle bounces back and forth between the upstream and downstream waves, and is accelerated. This acceleration is similar to the acceleration of shock wave diffusion; the final energy of the particles passing through the three accelerating stages is obviously larger than the particle energy that is accelerated by the two stages, and there are two parts of the particles passing through the three stages, and a part of the particles moving far away. Downstream, the other part moves to the far upper.
【學(xué)位授予單位】：中國(guó)科學(xué)技術(shù)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：P353

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