非迁移潮作用下的电离层赤道异常区单峰现象及其经度分布

当喷泉效应较弱而双峰结构发展不充分的时候,可能在赤道异常区仅能够观测到一个电子密度的峰值,称之为单峰现象.本文利用CHAllenging Minisatellite Payload卫星在2001-2010年的电子密度数据给出了单峰的发生规律,单峰在地方时早上08：00-10：00和下午16：00-19：00发生率高,发生位置在经度上呈现多波数分布,尤其在10：00-18：00明显：在分季时多呈现四波,而在冬至季时以三波为主.单峰发生多的经度,正好对应着双峰的结构特征较弱之处.究其原因,是非迁移潮的DE2和DE3分量调制了背景风场和大气发电机电场,在电场和喷泉效应减弱的经度,双峰结构难以形成时,就会表现为单峰结构.本文扩展了对单峰现象的地方时、季节和经度分布等规律的了解,明确了非迁移潮在其中施加的影响,由此,单峰同双峰现象一样可以用于研究非迁移潮对热层-电离层的作用.

     

磁层源赤道电集流效应的地方时变化和地区影响

本文用亚洲、非洲7个低纬地磁台资料研究磁层大尺度扰动引起的赤道电集流效应,并与模式计算结果进行比较。在分析的1982年21个事件中,Dst持续下降均在5h以上,其间至少有一个小时的环电流能量增长指数及Rq,（?）q是相应月份5个国际磁静日内该小时Zq之均值。取R指数负值最大时为0h。对分布于不同经度的3个台站的21个事件ΔZ按地方时平均,与模式计算的赤道电集流随地方时的变化进行了对比;又比较了7个台站3小时序列的变化类型和模式所得之电集流演化形态,结果均有较好吻合。仅非洲一站出现了某种特殊性。这表明除磁层扰动效应外,地理和地质因素也起一定作用,其具体影响及有关机制尚待进一步考察。     

磁层源赤道电集流效应的地方时变化和地区影响

本文用亚洲、非洲7个低纬地磁台资料研究磁层大尺度扰动引起的赤道电集流效应,并与模式计算结果进行比较。在分析的1982年21个事件中,D_st持续下降均在5h以上,其间至少有一个小时的环电流能量增长指数及R<-25nT/h。分析中只用了各事件的-1h,0h和1h之ΔZ。ΔZ=Z-（?）_q,（?）_q是相应月份5个国际磁静日内该小时Z_q之均值。取R指数负值最大时为0h。对分布于不同经度的3个台站的21个事件ΔZ按地方时平均,与模式计算的赤道电集流随地方时的变化进行了对比;又比较了7个台站3小时序列的变化类型和模式所得之电集流演化形态,结果均有较好吻合。仅非洲一站出现了某种特殊性。这表明除磁层扰动效应外,地理和地质因素也起一定作用,其具体影响及有关机制尚待进一步考察。     

平流层爆发性增温期间赤道电集流中太阴潮汐的经度变化统计学研究

本文利用地磁台站和卫星磁场数据,对平流层爆发性增温(Sudden Stratospheric Warming,SSW)期间赤道电集流(Equatorial Electrojet,EEJ)中太阴半日潮汐的经度变化进行了统计学分析.结果显示,SSW期间秘鲁和印度扇区的EEJ中太阴半日潮汐明显增强,且存在显著的经度差异.秘鲁扇区的EEJ中太阴半日潮汐达到峰值的时间要早于印度扇区,进一步分析发现峰值时间的经度差异与太阳活动和准两年振荡相位有关.此外,SSW期间秘鲁扇区EEJ的太阴半日潮汐峰值强度比印度扇区高.对比不同经度带背景磁场的强度与太阴半日潮汐的峰值幅度的关系,可以看出SSW期间EEJ太阴半日潮汐峰值幅度的经度差异与背景磁场强度有关,但也存在其他物理过程的影响.     

极光电激流的地方时和季节变化特性研究: CHAMP卫星观测

极光电激流是极区电流系的重要组成部分.本文利用CHAMP卫星10年的高精度标量磁场数据研究了极光电激流的地方时和季节变化特征,并对卫星与地面台站观测到的极光电激流进行了对比分析.结果表明,日侧极光电激流主要受太阳辐射的影响,而夜侧极光电激流主要受亚暴的影响.极光电激流具有明显的年、半年变化特征.夏季东向电激流和日侧西向电激流强于冬季,而夜间西向电激流冬季强于夏季.东向电激流和日侧的西向电激流在两至点增强,夜侧的西向电激流则在两分点增强.西向电激流与AL、SML指数有较好的相关性,东向电激流与SMU指数有较好的相关性,而与AU指数有一定差异,这与地磁台站的有效探测范围有关.

     

磁偏角和热层风对中纬电离层TEC经度分布的影响

本文利用北美、南美和大洋洲三个地区的电离层TEC数据,分析了磁偏角为零的经度线两侧中纬电离层TEC的差异.结果表明,在2001年至2010年的几乎所有季节,在磁偏角为零的经度东西两侧,北美、南美和大洋洲中纬电离层TEC都存在规则性的差异;中纬电离层TEC的这种经度差异显著地依赖地方时,对季节和太阳活动水平也有不同程度的依赖.地磁场影响下电离层与热层动力学耦合的分析表明,磁偏角的经度变化和热层风的地方时变化两者的共同作用是引起磁偏角为零的经度两侧中纬电离层TEC差异的重要原因之一.     

磁层-电离层-热层耦合的模式计算和分析

对磁层-电离层电动耦合和电离层发电机两种效应进行了模式计算,并对所得的一些耦合现象作了综合讨论.结果表明,在中低纬和赤道区的电离层和地磁研究中必须考虑磁层-电离层耦合效应向中低纬区的穿透和屏蔽;潮汐发电机效应对极光区（电导率增高时）的作用也值得重视.这两效应的特征和相对重要性随磁暴的发展阶段而异,在高低纬区也各不相同,但都有明显的晨昏不对称性.此外,弱磁扰对中低纬电离层形态的影响也不容忽视.     

磁层-电离层-热层耦合的模式计算和分析

对磁层-电离层电动耦合和电离层发电机两种效应进行了模式计算,并对所得的一些耦合现象作了综合讨论.结果表明,在中低纬和赤道区的电离层和地磁研究中必须考虑磁层-电离层耦合效应向中低纬区的穿透和屏蔽;潮汐发电机效应对极光区（电导率增高时）的作用也值得重视.这两效应的特征和相对重要性随磁暴的发展阶段而异,在高低纬区也各不相同,但都有明显的晨昏不对称性.此外,弱磁扰对中低纬电离层形态的影响也不容忽视.     

磁层源赤道电急流的模式研究

本文用数值计算方法对极盖区边界变化、其上驱动电势突然增减以及粒子沉降边界随时间变化等情况下,中低纬电离层电位分布及赤道电急流变化进行了研究。结果表明,赤道电急流明显地受到磁层-电离层电动耦合的影响。在白天到午夜的大部分时间内,当驱动势增强和扰动源向低纬扩展时,产生扰时附加东向赤道电急流;反之,有较强的磁层源西向电急流。计算结果解释了观测的主要现象,也表明观测结果的复杂性可能与过程不同阶段上电急流位相变化有关。     

磁层源赤道电急流的模式研究

本文用数值计算方法对极盖区边界变化、其上驱动电势突然增减以及粒子沉降边界随时间变化等情况下,中低纬电离层电位分布及赤道电急流变化进行了研究。结果表明,赤道电急流明显地受到磁层-电离层电动耦合的影响。在白天到午夜的大部分时间内,当驱动势增强和扰动源向低纬扩展时,产生扰时附加东向赤道电急流;反之,有较强的磁层源西向电急流。计算结果解释了观测的主要现象,也表明观测结果的复杂性可能与过程不同阶段上电急流位相变化有关。     

Subsolar elevation of the equatorial electrojet

The subsolar elevation of the equatorial electrojet has been produced from satellite solstitial data available from 09 to 15 hr LT using a new approach with the general style of the overhead equivalent current system. It shows the bunching of the current around the dip equator; the return currents of the equatorial electrojet close to the flanks of the dip equator; the fast growth of the electrojet to its diurnal peak followed by a slow decay; and the contraction of its latitudinal extent around the meridian of its highest intensity. Comparison with the results of other workers using ground data suggests that the elevation from satellite data agrees better with that from ground data when the worldwideSq is removed from the ground data.     

CSES卫星观测的赤道电集流特征

本文利用2018年8月到2019年12月期间我国张衡一号电磁监测试验卫星(CSES)所观测的地磁数据,反演了赤道电集流(EEJ)电流密度的纬度剖面;通过选取的4729个清晰的EEJ事件,分析了在地方时(LT)14:00附近的EEJ特征.研究结果表明：在地磁平静期间,CSES卫星观测的EEJ电流密度的峰值位于磁赤道附近,其平均幅度约为27 mA·m^-1.该幅度小于CHAMP和Swarm卫星的观测结果,这与2018—2019年期间太阳活动水平较低(平均F_10.7指数约为70 sfu)有关,此外也与CSES轨道所处的地方时相关.平均而言,EEJ的主瓣宽度约为4°,主瓣和旁瓣的峰值电流密度之比约为2.7;在本文所关注的事件中,东向EEJ事件约占83%,西向EEJ事件约占17%;这个比例与CHAMP卫星的观测结果稍有不同,与14:00 LT附近西向EEJ出现的概率较低有关.东向EEJ的峰值电流密度对经度、季节和太阳辐射水平有显著的依赖性.EEJ峰值密度随经度变化呈现明显的4波结构,可归因于低层大气非迁移潮汐的作用.EEJ峰值电流密度有明显的季节依赖,其幅度在春秋分较大,冬夏季较小.在2018—2019年期间,尽管太阳活动水平较低,EEJ峰值密度随太阳辐射水平的增加而增加.

     

Seasonal characterization of the equatorial electrojet height rise over Brazil as observed by the RESCO 50 MHz back-scatter radar

In this paper, we present the seasonal characteristics of the post-noon rise of the equatorial electrojet 3-m irregularities scattering region observed over São Luís, Brazil (2.3S, 44.2W, dip:-0.5). The study is based on a 1 year data set collected by the 50 MHz coherent back-scatter radar (also known by the acronym RESCO), that started operation in 1998. Using a method to estimate the moments from each individual back-scattered power profiles that constitute the standard range–time–intensity (RTI) maps we were able to determine the following representative parameters of the electrojet: the total power back-scattered by the electrojet irregularities (EJP), the thickness of the electrojet back-scattered power profile (EJT), the height of the center of the back-scatter region, that is, the power profile, (EJC), and the noise level corresponding to each power profile (EJN). The parameterization was applied to all selected daily RTI maps from 2002. The analysis was carried out by grouping the data according to the radar beam angle (tilted 30 westward or eastward), the magnetic disturbance indices K_p and the season, which enables us to quantify the differences in the parameters on these bases. The results are presented and discussed here focusing on the post-noon ascent of the EJC. We will also present results on the east–west asymmetry in the radar back-scattered echo power confirming our previous results, and on the appearance of a scattering region after sunset during magnetically quiet conditions around the southern summer solstice.     

赤道电射流的影响范围

本文收集了１９８２年３月印度、中国、菲律宾低纬地区９个地磁台的静日月均值资料。经分析对比后绘出了Ｓｑ（Ｈ），Ｓｑ（Ｚ）变幅与离磁赤道距离的关系图。结果显示赤道电射流对Ｓｑ（Ｚ）的影响可达５００ｋｍ，对Ｓｑ（Ｈ）的影响范围小于４００ｋｍ。这个结果与ＰＡＲＫＩＮＳＯＮ（１９８３）书中的论述基本一致。离磁赤道远达１０００ｋｍ的琼中台资料没受赤道电射流的影响，广州台资料则更不可能受影响。     

中国低纬地区地磁变化与赤道电射流

根据资料分析了中国低纬地区地磁场Ｈ分量的静日变化规律。结果表明，Ｈ分量日变幅在中午１２点左右达到最大值，在夜间达到最小值，而且，这种受赤道电射流影响的现象还随着季节和太阳活动变化而变化。     

Equatorial ionization anomaly of the total electron content and equatorial electrojet of ground-based geomagnetic field strength

Measurements from ground-based receiver chains of the global positioning system (GPS) and magnetometers of the Circum-pan Pacific Magnetometer Network (CPMN) in the west Pacific region during 1999–2003 are examined. The ionospheric total electron content (TEC) derived from the GPS receivers is used to observe the strength, location, and occurrence time of the equatorial ionization anomaly (EIA) crests, which resulted from the equatorial plasma E×B drift fountain. The magnetic field strength of CPMN is employed to monitor the equatorial electrojet (EEJ), and to further estimate the effectiveness of the E×B drift to the EIA crests. Results show that the strength and location of the EIA crests are proportional to the EEJ strength.     

Equatorial electrojet as part of the global circuit: a case-study from the IEEY

Geomagnetic storm-time variations often occur coherently at high latitude and the day-side dip equator where they affect the normal eastward Sq field. This paper presents an analysis of ground magnetic field and ionospheric electrodynamic data related to the geomagnetic storm which occured on 27 May 1993 during the International Equatorial Electrojet Year (IEEY) experiment. This storm-signature analysis on the auroral, mid-latitude and equatorial ground field and ionospheric electrodynamic data leads to the identification of a sensitive response of the equatorial electrojet (EEJ) to large-scale auroral return current: this response consists in a change of the eastward electric field during the pre-sunrise hours (0400–0600 UT) coherently to the high-, mid-, and equatorial-latitude H decrease and the disappearance of the EEJ irregularities between the time-interval 0800–0950 UT. Subsequent to the change in hF during pre-sunrise hours, the observed foF2 increase revealed an enhancement of the equatorial ionization anomaly (EIA) caused by the high-latitude penetrating electric field. The strengthening of these irregularities attested by the Doppler frequency increase tracks the H component at the equator which undergoes a rapid increase around 0800 UT. The H variations observed at the equator are the sum of the following components: S_R, DP, DR, DCF and DT.     

Contribution to geomagneticSq-field and equatorial electrojet from the day/night asymmetry of ionospheric current under dawn-to-dusk electric field of magnetospheric origin

If the earth and its ionosphere are immersed in a large-scale dawn-to-dusk electric field (of the order of 0.5 mV/m), the resultant dawn-to-dusk ionospheric currents are much stronger on the dayside than on the nightside. These asymmetric currents over the earth produce a magnetic field detectable on the ground, which will contribute to a considerable extent to theSq-field and equatorial electrojet.This paper was presented at the IAGA General Assembly meeting (Session 9.1) held in Vancouver, Canada, during August 1987.