【作者】 邢赞扬；

【导师】 吴振森； 杨惠根；

【作者基本信息】 西安电子科技大学 ， 无线电物理， 2013， 博士

【摘要】 太阳风能量和动量可以通过日侧极隙区直接注入到地球磁层，不同能量的沉降粒子可以沿着磁力线直接映射到极区电离层，激发出各种不同的瞬态极光现象。通过对日侧极光的光谱、强度和动力学特征的研究，寻找与磁层边界层之间的内在联系，进而可以反映日侧磁层的动力学过程。本文通过分析中国北极黄河站高分辨率的地基多波段极光观测数据，并结合太阳风和粒子的探测卫星和地基雷达的协同观测数据，详细研究了日侧极光的光谱、形态和运动特征，尤其详细阐述了“极向运动极光结构(PMAFs)”的观测特征及其产生机制。主要结果归纳如下：1)利用2003-2009年的北极黄河站极光观测，结合DMSP卫星粒子沉降探测，对磁正午附近的极光强度与沉降粒子沉降能量之间的关系进行了定量研究。统计结果表明，在10-13MLT，630.0nm的极光发光占主导，以低能粒子沉降为主；而在13-14MLT，I(630.0nm)/I(427.8nm)极光强度比值降低，沉降粒子能量较高。另外，利用极光强度与沉降电子的能通量以及极光强度比值与平均能量之间的函数关系，初步建立了北极黄河站磁正午附近极光强度与沉降粒子能量关系的反演参数模型，为空间天气的监测提供服务。2)联合地基极光、ESR和SuperDARN雷达等观测，研究了发生在2003年12月22日0900-1010UT时间段内极区电离层极光和等离子体的变化特征。结果表明，在不同行星际磁场（IMF）条件下，黄河站极光ASI均观测到了一系列PMAFs，且这些PMAFs都伴随有明显的粒子沉降特征。在IMF北向时，该粒子沉降能达到更低的电离层E区，而此时PMAFs相应位置的高纬电离层出现了一个典型反向对流涡，这是高纬（尾瓣）重联的典型特征之一，这些结果表明北向IMF条件下的这些PMAFs与高纬重联有关。而在IMF南向时，黄河站观测到的PMAFs可跨越更广的地磁纬度，表明其演化时间亦较长，其相应区域的电离层特征也表明该PMAFs由日侧磁层顶低纬磁重联所产生。3)利用北极黄河站6年高分辨率的地基多波段极光观测数据，统计研究了PMAFs与太阳风和IMF条件的依赖性关系。统计结果表明PMAFs大多发生在南向IMF条件下，并且大的IMF|Bx|更易触发PMAFs。从PMAFs发生率随MLT的分布以及对IMF的响应看，PMAFs在磁正午附近存在个弱的活动区，且呈现出与IMF By有关的午前-午后的不对性分布。我们首次发现这种与IMF By有关的午前-午后不对性在Bz正向比Bz负向时更明显，这可能与尾瓣重联有关。午前扇区和午后扇区的PMAFs的分布峰值在IMF时钟角90°和270°附近，这对应着午前/午后的反平行重联，而在磁正午扇区的PMAFs可能对应日下点的分量重联。统计结果还表明PMAFs不太可能是由太阳风动压脉动引起的，更可能是由脉动重联引起的。4)更进一步地，我们统计分析了稳定IMF条件下的PMAFs的位置分布与IMFBz和By分量的依赖性关系。我们发现大多数PMAFs发生在南向IMF条件下，而发生的地磁纬度也更低，且PMAFs呈现的与IMF By有关的午前-午后的不对性分布在Bz>0比Bz <0时更明显。在Bz <0时，PMAFs分布覆盖的MLT扇区更广泛，这些表明重联X线可能呈现“S”型分布；然而，在Bz>0，PMAFs在By>0时主要分布午前扇区，而在By <0时主要发生在午后，这可能与高纬重联的效应有关，这些结果与电离层对流的理论模型很大程度上是一致的。本文对PAMFs的观测特征和产生机制进行了系统研究，揭示了一些新特征，并对PMAFs的产生机制形成了一些新的认识。但是由于日侧PMAFs及其动力学过程的复杂性，PMAFs的精细结构，详细的演化过程以及伴随的极区电离层响应等仍有待进一步深入研究。更多还原

【Abstract】 Solar wind energy and momentum can access the magnetosphere via the daysidepolar region, where field lines map directly to the dayside magnetopause and boundarylayers and various auroral transients occur with different spectrum, luminosity anddynamics. These dynamic processes manifest the intrinsic relation between the auroralcharacteristics and magnetospheric boundary layers.Based on the high temporal resolution auroral observation data obtained from thethree-wavelength all-sky imagers at Yellow River Station in the Arctic, together with thesatellites’ observations for particles and solar wind and the radars’ observations, westudy the dayside poleward moving auroral forms (PMAFs) as well as its generationmechanisms. PMAF is one of the primary auroral forms in the magnetic local time(MLT) range of0900-1500MLT. The main results are summarized as follows:1) We investigated the quantitative relationship between the auroral intensities and theenergy features of the precipitated particles near magnetic noon by using auroraldata and particles data from DMSP satellites. Our statistical results indicated thatthe soft auroral electron precipitation was dominated during10-13MLT,corresponding to630.0nm auroral emissions. The auroral intensity ratioI(630.0nm)/I(427.8nm) decreased as the intensity of427.8nm increased over13-14MLT, suggesting the energy of the precipitated particles increased. In addition, theintensity of427.8nm depended on the total energy flux of the precipitating electronsand the I(630.0nm)/I(427.8nm) ratio related to the average energy. We have built aparameter model of auroral emissions and particle precipitation near magnetic localnoon at YRS, which may benefit monitor the space weather service in the future.2) Using auroral data at YSR together with the ESR radar and SuperDARN radars, weinvestigated the dayside PMAFs and the associated plasma features in the polarionosphere under different interplanetary magnetic field (IMF) conditions, between0900and1010UT on22December2003. Simultaneous optical and ESRobservations revealed that all of these PMAFs were clear associated with pulsedplasma precipitations. During northward IMF, the plasma can precipitate into loweraltitudes and reach the ionopheric E-region, and there is a reverse convection cellassociated with these PMAFs, which is one of the typical signatures in the polarionosphere of the dayside high-latitude (lobe) reconnection. These results indicatethat the PAMFs may due to the high-latitude reconnection. During southward IMF,the PAMFs observed at YRS show larger latitudinal motion, indicating a longermean lifetime, and the associated ionopheric features indicate that the PMAFs were generated by the dayside magnetopause low-latitude reconnection.3) We examined the dependence of the PMAF occurrence on solar wind conditions inthe MLT range of0900-1500MLT. It was found that most PMAF events occurredduring southward IMF and the PMAFs show a tendency to occur preferentiallyunder large IMF|Bx|conditions. The MLT dependence of PMAFs presents aremarkable tendency of decreasing in the midday sector, showing a clear IMFBy-related prenoon-postnoon asymmetry. For the first time, we found, however,that the asymmetry is more evident during conditions of Bz>0than Bz <0,suggesting the importance of the effect of the lobe reconnection. It is worth notingthat the PMAFs occurrence maximized when the IMF clock angle was near90°inthe prenoon and near270°in the postnoon, which might due to theprenoon/postnoon anti-parallel reconnection. We also found that62.12%PMAFsoccurred during the clock angle of90°-270°in the midday sector, which might dueto component reconnection.The dependence of PMAFs in the midday sector mightdue to component reconnection. Our statistical results suggest that the PMAFs arenot caused by the solar wind pressure pulses, but by bursts of magneticreconnection.4) Further, we statistically investigated the dependence of location of PMAFs on theIMF Bz and By components as a function of MLT and MLAT under stable IMFconditions. It was found that more PMAFs occurred in lower latitude for Bz <0andthere was less evident IMF By-related prenoon-postnoon asymmetry for Bz>0than for Bz <0. We found that the PMAFs distributed over a wide range of MLTwhen Bz <0, which indicates that the reconnection X-line might spread like an ‘S’shape. However, during northward IMF, PMAFs were observed predominantlyprenoon for IMF By>0and postnoon for IMF By <0associating with the effect ofthe high-latitude reconnection, which is highly consistent with the theoreticalconvection model.In this thesis, the features and mechanism of the PAMFs have been systematicallystudied. We revealed some new features and formed some new understanding aboutPMAFs. It is so complicated for the dayside PMAFs and their dynamic effect that thefine structures, detailed evolution and the associated polar ionosperic responses stillneed to be further studied.更多还原