The nature of electron density enhancement over a wide altitude range during ionosphere heating experiments at EISCAT

During the course of ionospheric heating experiments, researchers at the European Incoherent Scatter Scientific Association (EISCAT) observed an apparent electron density enhancement. The enhancement extended over a wide range of altitudes, above the reflection altitude of the high-frequency pump wave. However, whether this enhancement actually corresponds to a true enhancement in electron density remains an open question. When the dispersion relation of ion acoustic waves is followed, the frequency ratio of the enhanced ion line to the background ion line suggests that the profile of the effective ion mass may have remained unchanged. Furthermore, the solar radio flux and ion drift velocity indicate no significant changes in the ion species and their densities. In conclusion, the electron density enhancement observed at EISCAT should not, in fact, be considered a true enhancement.

Possible ion-acoustic soliton formation in the ionospheric perturbations observed on DEMETER before the 2007 Pu'er earthquake

The data of ionospheric perturbations observed on DEMETER before the 2007 Pu＇er earthquake are analyzed. The three-component plasma （ions, electrons and heavy ions） is studied in the fluid concept. The linear dispersion relation for ion-acoustic wave is found in the presence of heavy ions. The nonlinear dynamics is studied for arbitrary amplitude of the wave. The Sagdeev potential is calculated, which shows that solitary structure exists for Mach number within a range defined by the presence of heavy ions. The developed ion-acoustic solitons may be used as precursor for earthquake prediction.

Modelling of Geomagnetic Storm Effects in the Ionosphere of East Asia

This paper presents simulated results of the ionospheric behavior during few geomagnetic storms,which were occurred in the different seasons. The numerical model for ionosphere-plasmasphere coupling was used to interpret the observed variation of ionosphere structure. Reasons why the positive storms are dominant in the winter whereas the negative ones are dominant in the summer season present the special interest for the mid-latitude ionosphere. A theoretical analysis of the processes controlling the ionospheric response to the geomagnetic storms has showed a good agreement between the simulated results and measurements, as well as the crucial role of the neutral composition variations to fit the calculated and the observed ionospheric parameters.

DEMETER卫星离子浓度表征的电离层顶部结构季节变化特征

本文利用DEMETER卫星约6年的在轨观测O+离子浓度数据,控制电离层扰动空间尺度在t=20~300 s条件下,软件自动探测和识别117718个电离层扰动.去掉发生在Kp≥3的18169个扰动以消除磁暴对电离层的影响.对剩余的99549个扰动,按季节和发生当地时间进行分组.便于结果对比,只统计发生在夏季日侧、夏季夜侧、冬季日侧和冬季夜侧的四组电离层扰动.不同变化幅度和空间尺度扰动的全球分布图显示,冬季赤道电离异常(EIA)发育,表现为磁赤道两侧低的电离层扰动密度,南北半球磁纬15°左右突然增强.同时,日侧EIA异常主要表现为南北半球两侧边界扰动密度和空间尺度的同时增强,扰动空间尺度甚至超过200 s.单从空间尺度角度,t=120 s是一个分界点,空间尺度小于这个点的扰动发生在日侧的概率大于夜侧,而大于这个点时,结论相反.另外,大多数大空间尺度(t>200 s)的电离层扰动发生在日侧,尤其是夏季日侧,可能与强阳光照射引起电离层电离有关.除了夏季日侧,威德尔海异常(WSA)在其余时段均显示清晰的轮廓.在夏季日侧,在WSA地区的顶部电离层表现异常平静,没有变化幅度超过50%的正扰动和幅度超过100%的负扰动发生在这个区域.而在冬季夜侧,绝大多数幅度超过100%的正扰动发生在这个区域.

The siphonic energy transfer between hot solar wind and cold martian ionosphere through open magnetic flux rope

A mechanism for energy transfer from the solar wind to the Martian ionosphere through open magnetic flux rope is proposed based on the observations by Mars Atmosphere and Volatile EvolutioN(MAVEN).The satellite was located in the dayside magnetosheath at an altitude of about 70o km above the northern hemisphere.Collisions between the hot solar wind protons and the cold heavy ions/neutrals in the subsolar region can cool the protons and heat the heavy ions.As a result,the magnetosheath protons are siphoned into the ionosphere due to the thermal pressure gradient of protons and the heated heavy ions escape along the open magnetic field lines.Although direct collisions in the lower-altitude region were not detected,this physical process is demonstrated by MAVEN measurements of enhanced proton density,decreased proton temperature and oppositely directed motions of hot and cool protons within the flux rope,which are very different from the observational features of the flux transfer events near the Earth's magnetopause.This mechanism could universally exist in many contexts where a collisionless plasma region is connected to a collisional plasma region.By reconstructing the magnetic geometry and the cross-section of the flux rope using the Grad-Shafranov technique,the ion loss rates are quantitatively estimated to be on the order of 1023 s-l,which is much higher than previously estimated.

Effect of Sodium Ion Concentration on Hydrogen Production from Sucrose by Anaerobic Hydrogen-producing Granular Sludge

This work evaluated the effects of sodium ion concentration, ranging from 0 to 16000mg·L^-1（Na^＋）, on the conversion of sucrose to hydrogen by a high-activity anaerobic hydrogen-producing granular sludge. At the optimum sodium ion concentration [1000-2000mg·L^-1（Na^＋）] for hydrogen production at 37℃, the maximum sucrose degradation rate, the specific hydrogen production yield and the specific hydrogen production rate were 393.6-413.1mg·L^-1.h^-1, 28.04-28.97ml·g^-1, 7.52-7.83ml·g^-1.h^-1, respectively. The specific production yields of propionate, butyrate and valerate decreased with increasing sodium ion concentration, whereas the specific acetate production yield increased, meanwhile the specific production yields of ethanol and caproate were less than 55.3 and 12.6mg·g^-1, respectively. The hybrid fermentation composition gradually developed from acetate, propionate and butyrate to acetate with the increase in sodium ion concentration.

A Comparison of SuperDARN-Derived Plasma Convection and DMSP Ion Drift Measurements

Recently several studies indicated possible deterioration of accuracy in the SuperDARN convection measurements at large distances （〉2 500 km）. In this study, the SuperDARN-derived convection was compared with ion drift measurements given by the DMSP satellites, focused on SuperDARN far-range measurements, to investigate the above-mentioned problem. Two different procedures of SuperDARN convection estimation were applied. An overall reasonable agreement between two observation systems were found though individual points in some passes show significant differences. Besides, a tendency is also clear that the SuperDARN-derived velocities were slightly smaller than those of DMSP ion drift measurements. Potential factors contributing to the velocity differences were explained.

Systematic variation in observing altitude of enhanced ion line by the pump near fifth gyroharmonic

The observation of ultra high frequency radar during an ionospheric experiment carrying out at the European Incoherent Scatter Scientific Association, demonstrates a systematic variation in the altitude of the pump enhanced ion line, which is quite remarkably dependent on the pump frequency, that is, when the pump frequency sweeps above the fifth gyroharrnonic, the altitude of the enhanced ion line is ～3 to ～6 kin lower than that at the pump frequency very close to the fifth gyroharmonic. The analysis shows that the systematic variation in the altitude of the pump enhanced ion line is principally dependent on the enhanced electron temperature, although the changes in the profile of the electron density brought about by the ionospheric heating are not independent of those systematic altitude variations.

Effect of Sodium Ion Concentration on Hydrogen Production from Sucrose by Anaerobic Hydrogen-producing Granular Sludge

This work evaluated the effects of sodium ion concentration, ranging from 0 to 16000mg·L-1(Na+), on the conversion of sucrose to hydrogen by a high-activity anaerobic hydrogen-producing granular sludge. At the opti- mum sodium ion concentration [1000—2000mg·L-1(Na+)] for hydrogen production at 37℃, the maximum sucrose degradation rate, the specific hydrogen production yield and the specific hydrogen production rate were 393.6— 413.1mg·L-1·h-1, 28.04—28.97ml·g-1, 7.52—7.83ml·g-1·h-1, respectively. The specific production yields of propionate, butyrate and valerate decreased with increasing sodium ion concentration, whereas the specific acetate production yield increased, meanwhile the specific production yields of ethanol and caproate were less than 55.3 and 12.6mg·g-1, respectively. The hybrid fermentation composition gradually developed from acetate, propionate and butyrate to acetate with the increase in sodium ion concentration.

Incoherent scatter radar (ISR) observations of high-frequency enhanced ion and plasma lines induced by X/O mode pumping around the critical altitude

Analysis of Incoherent Scatter Radar(ISR)data collected during an experiment involving alternating O/X mode pumping reveals that the high-frequency enhanced ion line(HFIL)and plasma line(HFPL)did not appear immediately after the onset of pumping,but were delayed by a few seconds.By examining the initial behaviors of the ion line,plasma line,and electron temperature,as well as ionosphere conditions,we find that(1)the HFIL and HFPL were delayed not only in the X mode pumping but also in the O mode pumping and(2)the HFIL was not observed prior to enhancement of the electron temperature.Our analysis suggests that(1)leakage of the X mode to the O mode pumping may not be ignored and(2)spatiotemporal uncertainties and spatiotemporal variations in the profiles of ion mass and electron density may have played important roles in the apparent failure of the Bragg condition to apply;(3)nevertheless,the absence of parametric decay instability(PDI)cannot be ruled out,due to our inability to match conditions caused by the spatiotemporal uncertainties.

极盖区等离子体云块近十年研究进展

极盖区等离子体云块是一种经常出现在极区电离层F层的高密度块状结构,其电子密度一般是背景电子密度的两倍及以上,水平尺度约为100~1000 km.极盖区等离子体云块的产生及演化过程可以示踪磁层-电离层/热层耦合过程中的能量及动量传输过程.同时,这种电子密度不均匀体(尤其是其边沿区域)对跨极盖区的无线电波传播具有很强的干扰,经常影响无线电通讯导航定位等应用.因而,极盖区等离子体云块研究不仅是空间物理领域的热点问题,而且也是空间天气监测及准确预报等应用的重要基础.本文简述了近十年来极盖区等离子体云块的研究进展,主要内容包括:概括了极盖区等离子体云块几种可能的形成机制;提出了极盖区冷/热等离子体云块的分类研究;统计了极盖区等离子体云块的时空分布特征及其对外部条件的依赖性;追踪了极盖区等离子体云块的完整演化过程;最后,讨论了极盖区等离子体云块引起的离子上行现象及电离层闪烁效应.

用于电离层离子探测的多路微弱电流检测电路设计

针对电离层离子探测传感器对电流检测电路的需求,设计了一种适用于阻滞势电位分析仪和离子漂移计复用传感器的多路微弱电流检测电路。在放大模块设计中,分析并仿真对比了T型电阻网络和跨阻式电阻网络的噪声及直流偏置水平,研究了不同反馈电容下的噪声、带宽和时延等特性。为降低电路噪声水平,提高电路整体性能,设计了滤波模块、采集模块和高精密电源模块。实验结果证明:该电路系统具有良好的准确性、一致性、稳定性和实际应用性,可推广应用于电离层微弱信号检测领域。

Effect of temporal variation rate of cross polar cap potential on the equatorial ionospheric vertical drift: A statistical study

Based on the equatorial vertical ion drift measured by DMSP and cross polar cap potential （Фcpc） from AMIE output during 2001 to 2003, this paper investigates the relationship of Фcpc and its temporal variation rate （△Фcpc） with the disturbed ion velocity （△Vx） which is the difference between the disturbed days （Kp〉4） and quiet days （Kp〈2）. The statistical analysis shows： （1） The △Vx correlates better with AФcpc than with Фcpc, indicating that the electric field penetration is more easily to occur when solar wind input rapidly varies with time. （2） The optimal delay time of electric field penetration from the high-latitude magnetosphere to equatorial ionosphere has local time dependence which is longer on the nightside than on the dayside. It may be due to more complicated electrodynamic process on the nightside. （3） With the linear relationship between △Фcpc and △Vx, it is obtained that the penetration efficiency is about 4.5%-13.9% at day and 31%-42% at night, coinciding well with former studies.

Morphology of polar ionospheric O^+ ion upflow: FAST observations during quiet time

With energetic ion measurements on FAST satellite, the morphologic features of quiet-time ionospheric O+ ion upflowing at altitudes of 2000 to 4000 km are drawn out for the first time. The pre-noon cusp/cleft is the predominant region of upflowing occurrence for O+ with lower energy. Meanwhile the pre-dawn sector near the equatorward edge of the plasma convection dominates the occurrence for the higher energy O+ ions. No matter whether the energy is lower or higher, the upflows occur often over a wide MLT range of lower latitudes outside the auroral oval. The upflowing within the pre-midnight (21:00― 22:00 MLT) auroral oval carrys larger energy fluxes, with extremely large fluxes for higher energy O+ appearing near the polar cap boundary. For altitudes of 2000―4200 km under observation, the ion conics occur much more frequently than ion beams. Ion beams are rarely found below 3000 km, while the conics occur uniformly over the observed altitudes.

基于张衡一号卫星监测的2021年青海玛多7.4级地震前电离层效应

本次研究围绕张衡一号(ZH-1)卫星监测到的2021年青海玛多Ms7.4地震前的电离层效应,采用上下四分位距法和小波变换法处理ZH-1卫星朗缪尔探针(LAP)探测到的电子密度N。和等离子体分析仪(PAP)探测到的离子密度N:(He+和O+)数据,经分析发现Ne、He+密度和0+密度在震前7天(2021年5月14日)和5天(2021年5月16日)出现同步异常。在此基础上,基于地球物理异常多项证据,分析认为2021年玛多Ms7.4地震孕育过程包括应力扩张早期、应力扩张晚期和临震加速期,该地震可能通过岩石圈一大气圈一电离层耦合模型的声重波、电磁波通道影响了电离层。

Distribution of ionospheric O^+ ion in synchronous altitude region

Based on satellite observation data, using dynamics equation, the ionospheric O+ ions distribution in the synchronous altitude region for different geomagnetic activity index Kp is studied by theoretical modeling and numerical analyzing, and semi-empirical models for the O+ ions den-sity and flux versus longitude in the synchronous altitude region for different Kp are given. The main results show that in the synchronous altitude region: (i) The O+ ions density and flux in day-side are larger than those in nightside. (ii) With longitude changing, the higher the geomagnetic activity index Kp is, the higher the O+ ions density and flux, and their variation amplitude will be. The O+ ions density and flux when Kp ≥ 6 will be about ten times as great as that when Kp = 0. (iii) When Kp = 0 or Kp ≥ 6, the O+ ions density reaches maximum at longitudes 120°and 240°respectively, and minimum in the magnetotail. When Kp = 3—5, the O+ ions density gets to maxi-mum at longitude 0°, and minimum in the magnetotail. However, the O+ ions flux reaches maxi-mum at longitude 120°and 240°respectively, and minimum in the magnetotail for any Kp value.

新疆于田7.2级地震前的电离层电磁扰动

利用法国DEMETER卫星观测的电磁、等离子体等参量的观测数据分析了2008年3月21日新疆于田7.2级地震前离子温度(T_i)、离子密度(N_i)、甚低频(VLF)磁场等出现的异常变化.T_i分析显示震中区上空出现的突变信号在更大空间多次重复出现,作为地震异常的信度不高.通过多次重访轨道对比发现H^+离子密度整体变化形态一致,但夏秋季节的峰值变化幅度是冬春季节的1倍.通过把2008年的数据与2007年和2006年同期的重访轨道数据进行对比,发现2008年在于田地震前1个月左右N_i在峰值区呈现了显著增强的变化趋势,并一直持续到地震前,2008年2月以后的峰值幅度是其他两年同期的1倍多.对于磁场频谱数据,抽取了震中区域上空2000km范围内多个轨道的单频(400Hz)信息,并在研究区域统一纬度空间(0～60°N)进行了时间序列对比,结果发现地震前2日内震中区域上空400Hz谱密度增加了近一个数量级,反映空间存在明显的VLF电磁辐射现象.对于3月20日极低频段(ELF)三分量电磁场的矢量分析显示观测时段内存在一些左旋极化电磁信号,反映了空间电离层离子密度变化伴随ELF电磁辐射信息.综合分析认为,这次地震前各参量的变化过程与目前地震孕育及电离层耦合机理相吻合.

极区顶部电离层离子上行—DMSP卫星观测

本文利用DMSP卫星离子漂移速度测量数据,对高纬顶部电离层离子整体上行进行研究,主要考察平静时和磁暴期间离子上行强度与发生率随MLT(晨昏两侧)分布规律的变化；以及磁暴期间强的离子上行与等离子体对流及其剪切之间的关系。研究发现,磁暴期间强上行事件的发生率比平静期高近2倍,发生率的晨昏不对称性出现逆转,由平静时昏侧发生率较大变为磁暴期间晨侧发生率较大；磁暴期间晨侧离子上行速度的分布向速度高端加权,平均速度大于昏侧,最大上行速度远大于昏侧；强的离子上行往往与强对流剪切或强对流本身相伴随。

电磁监测试验卫星阻滞势分析器探测技术

依据电磁监测试验卫星的任务要求,自主研发了等离子体分析仪,首次实现电离层等离子体原位探测.作为等离子体分析仪的重要组成部分,阻滞势分析器主要用于探测电离层等离子体的密度、沿轨道方向漂移速度、温度以及成分等参数.阻滞势分析器传感器栅网材料选用铍铜,表面镀金处理,并通过仿真验证了多层栅网总透过率与理论计算的一致性.依据技术指标,详细设计了阻滞势分析器传感器的窗口半径、收集极半径、有效高度及扫描电压等参数.在电子学电路设计时通过前放电路三个可调量程的设计,保证了电路测量精度.在此基础上,借助意大利国家天体物理研究院行星际物理研究所的地面等离子体环境,完成了阻滞势分析器的等离子体环境测试.测试结果表明,该阻滞势分析器的性能指标满足设计要求,能够实现电磁监测试验卫星的任务需求.

电离层上行O^+离子沿不同经度处的磁力线向磁层的传输

根据解析求解引导中心近似的动力学方程得到的离子分布函数 ,研究了不同Kp指数条件下起源于不同电离层区域的上行O+离子通量密度沿不同经度处的磁力线的定态分布 ,并研究了上行O+离子向不同磁层区域传输的特性 .主要结果为 :( 1 )起源于向阳面极光带外侧及更低纬区的电离层离子基本上传输到向阳面磁层区 ;起源于背阳面极光带及更低纬区的电离层离子基本上传输到背阳面磁尾等离子体片区和闭合磁力线区 ;起源于极盖区及向阳面极光带内侧的电离层离子基本上传输到等离子体幔区和磁瓣区 .( 2 )上行离子主要分布在近地空间 ,其通量密度相对于地心距离呈负梯度 .( 3)地磁活动指数Kp 增高时上行离子进入磁层的概率增大 ,因而上行离子起动力学作用的地球空间范围增大 .所得结果可解释有关地顶的观测特征 。