Geomagnetic pulsation over conjugate locations during geomagnetic storms and substorm

Geomagnetic data collected during magnetic storm over magnetically conjugate pair (according to IGRF 2000) of high latitude stations viz., Maitri (70° 45′ S, 11° 42′ E) and Tromso (69° 40′ N, 18° 56′ E) reveal that amplitudes of Pc6 pulsation characteristically differ. The amplitude obtained from horizontal magnetic field for the Pc6 pulsation frequency range between 0.6 and 1.6 mHz significantly differs in time corresponding to peak amplitude. The relative differences in its time of occurrence found to gradually increase around initial phase of storm and remain exactly out of phase at peak amplitude of storm. Thence, it is found to be in agreement in phase gradually until storm unwinds. This indicates that simultaneous amplitude of Pc6 pulsation at conjugate pair of stations and its time of occurrence could be a key factor to infer storm arrivals somewhat prior to its peak effects. The emphasize remains on prediction of storm arrivals only by utilizing ground based magnetometer observations. However, it is necessary to understand differences on the basis of weak, moderate, strong, and super strong cases and more exactly how they behave along the line of magnetic Meridian. Nevertheless, the analysis implies that geo-effective magnetic ejecta/clouds/CIRs/sheaths/CMEs/ICMEs giving rise to geomagnetic storm can be predicted ahead of its peak effects by having magnetometer data over conjugate locations.     

Signatures of strong geomagnetic storms in the equatorial latitude

Ionosonde data from two equatorial stations in the African sector have been used to study the signatures of four strong geomagnetic storms on the height – electron density profiles of the equatorial ionosphere with the objective of investigating the effects and extent of the effects on the three layers of the equatorial ionosphere. The results showed that strong geomagnetic storms produced effects of varying degrees on the three layers of the ionosphere. Effect of strong geomagnetic storms on the lower layers of the equatorial ionosphere can be significant when compared with effect at the F2-layer. Fluctuations in the height of ionization within the E-layer were as much as 0% to +20.7% compared to −12.5% to +8.3% for the F2-layer. The 2007 version of the International Reference Ionosphere, IRI-07 storm-time model reproduced responses at the E-layer but overestimated the observed storm profiles for the F1- and F2-layers.     

Impact of geomagnetic variation over sub-auroral ionospheric region during high solar activity year 2014

The present work is an attempt to evaluate the impact of changing space weather condition over sub-auroral ionosphere during high solar activity year 2014. In view of this, the GPS based TEC along with Ionosonde data over Indian permanent scientific base “Maitri”, Antarctica (70°46′00″S, 11°43′56″E) has been utilized. The results suggested that the nature of ionospheric responses to the geomagnetic disturbances not only depended upon the status of high latitudinal electro-dynamic processes but also influenced by the seasonal variations. The results revel both negative and positive type of ionospheric response in a single year but during different seasons. The study suggested that the combination of equator-ward plasma transportation along with ionospheric compositional changes causes a negative ionospheric impact especially during summer and equinox seasons. However, the combination of pole-ward contraction of the oval region along with particle precipitation may lead to exhibit positive ionospheric response during the winter season. The plasma transportation direction has been validated with the help of convection boundary (HM boundary) deduced with the help of SuperDARN observations. The ground based ionosonde observations clearly provided the evidence of deep penetration of high energetic particles up to the E-layer heights which results a sudden and strong appearance of E-layer. The strengthening of E-layer is responsible for modification of auroral electrojet and field-aligned current system. Also, the sudden appearance of E-layer along with a decrease in F-layer electron density suggested the dominance of NO⁺ over O⁺ in a considered region under geomagnetic disturbed condition.     

Geomagnetic effects on mid-latitude railways: A statistical study of anomalies in the operation of signaling and train control equipment on the East-Siberian Railway

Intense geomagnetically induced currents (GIC) can hamper rail traffic by disturbing signaling and train control systems. GIC threats have been a concern for technological systems at high-latitude locations due to geomagnetic disturbances driven by substorm expansion electrojet or convection electrojet intensifications. However, other geomagnetic storm processes such as storm sudden commencement (SSC) and geomagnetic pulsations can also cause GIC concerns for technological systems. We present in this paper the first evidence based on statistical data for links between geomagnetic disturbances and faulty operations (anomalies) in the functioning of railway automatics and telemetry. We analyze anomalies of automatic signaling and train control equipment which occurred in 2004 on the East-Siberian Railway (corrected geomagnetic latitude _m = 46–51°N and longitude λ_m = 168–187°E). Our results reveal a seasonal effect in the number of anomalies per train similar to the one observed in geomagnetic activity (Kp, Ap, Dst indices). We also found an increase by a factor of 3 in the total duration of daily anomalies during intense geomagnetic storms (local geomagnetic index specific to Siberian Observatory A_max > 30), with a significant correlation between the daily sum of durations of anomalies with geomagnetic activity. Special attention was paid to failures not related to recognized technical malfunctions. We found that the probability of these failures occurring in geomagnetically disturbed periods was 5–7 times higher than the average anomaly occurrence.     

Space weather in Japan

In Japan, Communications Research Laboratory engages in operational space environment information services as National Forecasting Center and Regional Warning Center of ISES. Data from local observations and data collected via internet from domestic and foreign institutes are used for the daily operational forecast. Fundamental research on space weather issues has been carried out at several institutes and universities, including STE Laboratory and NASDA. In this presentation, an overview of current space weather forecast operations and a system for information outreach in Japan will be presented. Current and future observation programs from ground-base and space will be also briefly reviewed.     

A new approach to solar cycle forecasting

We describe a novel approach for determining the timing of the solar cycle and tracking its evolution relative to other cycles. This method also has predictive capability for forecasting the cycle “onset.” Based on current trends, we expect that Cycle 23 will be about 1 year longer than the previous two cycles.     

影响卫星故障的空间天气分析

基于美国国家地球物理数据中心(NGDC) 2384例和中国19颗卫星的263例卫星故障信息, 结合1963-2012年小时平均的多种空间环境数据, 定量分析了三种卫星故障发生期间的空间要素特征, 探讨单粒子锁定(SEU)、表面充电致静电放电(ESD)和内部深层充电所致电子引起的电磁脉冲(ECEMP)与空间天气事件的可能联系, 得出以下主要结论. (1)大部分SEU和ECEMP发生于空间天气平静时, 但在其前后3日内地磁活动达到了磁暴水平, 相对来说比例最大的发生在Dst_min之后第3日 (48～72h). (2) ESD受地磁活动和高能电子通量影响明显. 与磁暴、相对论电子通量增强事件的季节性相对应, 两分点附近ESD和ECEMP的发生率高; 93.6% 的 ESD发生前后72h内地磁活动达到磁暴水平, 故障发生时间均匀分布在 Dst_min前0～48h 和后0～24h; 54.9%的ESD 发生时处于地磁暴期(Dst <-30nT), 以-50～-30nT的小磁暴水平居多; 40.6%的ESD发生于高能电子通量高水平期(≥ 10³pfu, 1pfu =1cm^-2·s^-1·sr^-1), 81.9%的ESD发生前后72h 内高能电子通量峰值≥ 10³pfu, 发生率最高时段为电子通量峰值前 48～72h. (3)高能电子对中国同步轨道卫星的SEU影响明显, 42.5% 故障发生 时高能电子通量≥ 10³pfu, 故障在峰值前48～72h和峰值后48～72h 的发生概率相当, 约为23.0%. (4)同步轨道卫星SEU受太阳质子事件的影响相对较大, 22.5%的中国同步轨道卫星故障发生前后72h内发生了太阳质子事件, 季节性不明显.     

Effects of space weather on the ionosphere and LEO satellites’ orbital trajectory in equatorial,low and middle latitude

We study the effects of space weather on the ionosphere and low Earth orbit (LEO) satellites’ orbital trajectory in equatorial, low- and mid-latitude (EQL, LLT and MLT) regions during (and around) the notable storms of October/November, 2003. We briefly review space weather effects on the thermosphere and ionosphere to demonstrate that such effects are also latitude-dependent and well established. Following the review we simulate the trend in variation of satellite’s orbital radius (r), mean height (h) and orbit decay rate (ODR) during 15 October–14 November 2003 in EQL, LLT and MLT. Nominal atmospheric drag on LEO satellite is usually enhanced by space weather or solar-induced variations in thermospheric temperature and density profile. To separate nominal orbit decay from solar-induced accelerated orbit decay, we compute $r\text{,}h$ and ODR in three regimes viz. (i) excluding solar indices (or effect), where $r=r_0\text{,}h=h_0$ and $\mathit{ODR}={\mathit{ODR}}_0$ (ii) with mean value of solar indices for the interval, where $r=r_m\text{,}h=h_m$ and $\mathit{ODR}={\mathit{ODR}}_m$ and (iii) with actual daily values of solar indices for the interval ($r\text{,}h$ and ODR). For a typical LEO satellite at h?=?450?km, we show that the total decay in r during the period is about 4.20?km, 3.90?km and 3.20?km in EQL, LLT and MLT respectively; the respective nominal decay ($r_0$) is 0.40?km, 0.34?km and 0.22?km, while solar-induced orbital decay ($r_m$) is about 3.80?km, 3.55?km and 2.95?km. h also varied in like manner. The respective nominal ${\mathit{ODR}}_0$ is about 13.5?m/day, 11.2?m/day and 7.2?m/day, while solar-induced ${\mathit{ODR}}_m$ is about 124.3?m/day, 116.9?m/day and 97.3?m/day. We also show that severe geomagnetic storms can increase ODR by up to 117% (from daily mean value). However, the extent of space weather effects on LEO Satellite’s trajectory significantly depends on the ballistic co-efficient and orbit of the satellite, and phase of solar cycles, intensity and duration of driving (or influencing) solar event.     

空间物理学最新进展与展望

空间物理学是人类进入空间时代后迅速发展的一门新兴交叉学科,特别是进入新世纪后国内外都取得了辉煌的成就.本文简要介绍空间物理领域近年来取得的重要进展、重要成果、国内外发展趋势,以及未来发展的重点方向.     

Magnetic storm cessation during sustained northward IMF

Times of sustained strong northward IMF can interrupt the magnetic storm development and lead to lower levels of geomagnetic activity for many hours. During 1997–2000 we have found two events of this kind observed on November 8, 1998 and October 13, 2000. In both cases, the storms started as usual after arrival of ejecta with a southward IMF component from the Sun to the Earth, but ceased after several hours due to the onset of sustained northward IMF leading to the faster recovery process. After the passage of this so-called positive domain, the storm development started again. The heliospheric magnetic field intensity remained enhanced and nearly constant. The solar origins of the geomagnetic storm interruptions have been investigated. Tentatively they may be related to strong nonlinear Alfvйn type solitary waves excited by non-stationary coronal current variations with a characteristic time-scale of about a day.     

2000年7月空间天气大事件对地磁场的影响

2000年7月空间大事件对地磁场产生了巨大影响,7月15日至18日发生大磁暴（K=9）.磁暴为急始型,在我国地区初相期变幅有200-300 nT,主相最大幅度有500-600nT,为多年来所罕见.在行星际磁场B_z由北向转向南向时,磁暴主相开始;南向分量达到最大值后大约2 h,地磁H分量达到最小值,恢复相开始.并且,这次磁暴与太阳风也存在一定的对应关系.     

A Review on the Ionospheric Research:Chinese Works During 2006—2008

This paper reviews various progresses on the ionospheric studies by the scientists in China during the last two years.The main contents concern the 4 aspects of the ionospheric re-search:(1) ionospheric weather and coupling with magnetosphere(polar and auroral ionosphere,ionospheric response to substorms,ionospheric storms);(2) mid-and low-latitude ionospheric clima-tology(ionospheric properties,yearly variations and solar activity dependence,long term variation);(3) ionospheric coupling with neutral atmosphere(gravity waves,tides,planetary waves,background upper atmosphere,and ionospheric response);and(4) ionospheric diagnostics(observation,modeling,and prediction).     

A Review on the Ionospheric Research： Chinese Works During 2006-2008

This paper reviews various progresses on the ionospheric studies by the scientists in China during the last two years.The main contents concern the 4 aspects of the ionospheric research:(1)ionospheric weather and coupling with magnetosphere(polar and auroral ionosphere,ionospheric response to substorms,ionospheric storms);(2)mid-and low-latitude ionospheric climatology(ionospheric properties,yearly variations and solar activity dependence,long term variation);(3)ionospheric coupling with neutral atmosphere(gravity waves,tides,planetary waves,background upper atmosphere,and ionospheric response);and(4)ionospheric diagnostics(observation,modeling,and prediction).     

全球空间天气路线图及对中国的启示

随着科技的发展,空间天气对电力系统、通信导航系统和航天资产等遍布全球的技术基础设施的影响越来越深.需要加强对空间天气事件过程的理解,提升空间天气的预报能力,优化基础设施设计,从而减缓空间天气对社会造成的影响.基于这些需求,国际空间研究委员会（COSPAR）联合国际与日共存计划（ILWS）共同成立专家组,研究制定了全球2015-2025空间天气发展路线图.本文对该路线图进行介绍和解读,讨论该路线图对中国空间天气发展的启示.     

伴随磁层稳态对流的磁暴及磁暴期间环电流的特征

参考活跃的磁层稳态对流标准,选取了2001—2017年12个伴随磁层稳态对流的磁暴,研究发现这些磁暴存在以下共性：有长达约10h的漫长主相;其SYM-H存在一个最小值的平台期,约持续3～10h;这些磁暴发生时,部分环电流持续位于昏侧,其持续时间和行星际磁场分量B_z的稳定南向驱动时间相等.此外,这些磁暴发生时,其平台期的环电流离子的寿命为2.4～5.5h,比一般的大磁暴事件中离子寿命长,且其寿命与平台期长短没有明显关系.伴随稳态对流的大磁暴发生时,环电流离子寿命长,环电流衰减慢,推测是稳态对流期间能量持续而稳定注入磁层导致的.