The morphology and velocity field of the large flare on the solar disc on July 14, 1980

The active region morphology and the features of solar radio bursts and sight-line velocity distribution of a flare of Importance 3B on the solar disc (AR 2562) on 1980 July 14 are introduced in this article.     

Coronal mass ejection interaction and particle acceleration during the 2001 April 14–15 events

Two successive solar energetic particle (SEP) events associated with fast and wide coronal mass ejections (CMEs) on 2001 April 14 and 15 are compared. The weak SEP event of April 14 associated with an 830 km/s CME and an M1.0 flare was the largest impulsive event of cycle 23. The April 15 event, the largest ground level event of cycle 23, was three orders of magnitude more intense than the April 14^th event and was associated with a faster CME (1200 km/s) and an X14.4 flare. We compiled and compared all the activities (flares, CMEs, interplanetary conditions and radio bursts) associated with the two SEP events to understand the intensity difference between them. Different coronal and interplanetary environments of the two events (presence of preceding CME and seed particles ahead of the April 15 event) may explain the intensity difference.     

The impact of coronal mass ejection on the horizontal geomagnetic fields and the induced geoelectric fields

This work investigates the influence of coronal mass ejection (CME) on the time derivatives of horizontal geomagnetic and geoelectric fields, proxy parameters for identifying GICs. 16 events were identified for the year 2003 from the CORONAS-PHOTON spacecraft. Five of the events (May 29, June 9, October 28, October 29, and November 4) were extensively discussed over four magnetic observatories, were analyzed using the time derivatives of the horizontal geomagnetic (dH/dt) and geoelectric (E_H) fields obtained from data of the INTERMAGNET network. It was observed that energy distributions of the wavelet power spectrum of the horizontal geoelectric field are noticed at the nighttime on both 29 May and 9 June 2003 across the stations. Daytime and nighttime intensification of energy distribution of the wavelet power spectrum of the horizontal geoelectric field are observed on both 28 and 29 October 2003 due to strong westward electrojet. The 4 November 2003 event depicts daytime amplification of energy distributions of the wavelet power spectrum across the stations. The highest correlation magnitude is obtained in the event of 4 November 2003 between dH/dt and E_H relationships during the intense solar flare of class X 17.4. We observed that the correlation magnitude between dH/dt and E_H increases with increase in CME activity. We concluded that the response of the surface impedance model for different stations plays a key role in determining the surface electric field strength, due to large electric field changes at different stations.     

等重量空心盘冷气布置方案

采用数值方法研究了双辐板涡轮盘(即空心涡轮盘)腔内的流动和换热结构.在空心涡轮盘与实心涡轮盘重量一定的前提下,按照转静腔和旋转腔冷气进气位置不同,提出几种组合进气方式的空心涡轮盘冷却结构,即:中心进气转静腔+中心进气旋转腔、中心进气转静腔+高位进气旋转腔、高位进气转静腔+中心进气旋转腔以及高位进气转静腔+高位进气旋转腔.计算结果表明:中心进气转静腔+高位进气旋转腔结构、高位进气转静腔+高位进气旋转腔结构与等重量实心盘及其它空心盘结构相比具有较好的换热效果,同工况下涡轮盘体积平均温度和最大径向温差在空心盘各结构中较低,但阻力损失较大.     

The flares of April, 1980

A brief report is given on the characteristics of solar flares from the active region Boulder 2372. It is interesting to note the morphological similarity (homology) between many of these events, most likely caused by the overall constancy of the magnetic field configuration. Under closer examination this first-order homology breaks down, a fact that may help us understand the basis of the flare mechanism.     

Coronal mass ejection detection using wavelets,curvelets and ridgelets: Applications for space weather monitoring

Coronal mass ejections (CMEs) are large-scale eruptions of plasma and magnetic field that can produce adverse space weather at Earth and other locations in the Heliosphere. Due to the intrinsic multiscale nature of features in coronagraph images, wavelet and multiscale image processing techniques are well suited to enhancing the visibility of CMEs and suppressing noise. However, wavelets are better suited to identifying point-like features, such as noise or background stars, than to enhancing the visibility of the curved form of a typical CME front. Higher order multiscale techniques, such as ridgelets and curvelets, were therefore explored to characterise the morphology (width, curvature) and kinematics (position, velocity, acceleration) of CMEs. Curvelets in particular were found to be well suited to characterising CME properties in a self-consistent manner. Curvelets are thus likely to be of benefit to autonomous monitoring of CME properties for space weather applications.     

The effect of total solar eclipse of October 3, 2005, on the total electron content over Europe

GPS observations from EUREF permanent GPS network were used to observe the response of TEC (Total Electron Content) to the total solar eclipse on October 3, 2005, under quiet geomagnetic conditions of the daytime ionosphere. The effect of the eclipse was detected in diurnal variations and more distinctly in the variations of TEC along individual satellite passes. The trough-like variations with a gradual decrease and followed by an increase of TEC at the time of the eclipse were observed over a large region. The depression of TEC amounted to 3–4 TECU. The maximum depression was observed over all stations located at the maximum path of the solar eclipse. The delay of a minimum level of TEC with respect to the maximum phase of the eclipse was about 20–30 min.     

Ionospheric storm due to solar Coronal mass ejection in September 2017 over the Brazilian and African longitudes

Coronal mass ejection (CME) occurs when there is an abrupt release of a large amount of solar plasma, and this cloud of plasma released by the Sun has an intrinsic magnetic field. In addition, CMEs often follow solar flares (SF). The CME cloud travels outward from the Sun to the interplanetary medium and eventually hits the Earth’s system. One of the most significant aspects of space weather is the ionospheric response due to SF or CME. The direction of the interplanetary magnetic field, solar wind speed, and the number of particles are relevant parameters of the CME when it hits the Earth’s system. A geomagnetic storm is most geo-efficient when the plasma cloud has an interplanetary magnetic field southward and it is accompanied by an increase in the solar wind speed and particle number density. We investigated the ionospheric response (F-region) in the Brazilian and African sectors during a geomagnetic storm event on September 07–10, 2017, using magnetometer and GPS-TEC networks data. Positive ionospheric disturbances are observed in the VTEC during the disturbed period (September 07–08, 2017) over the Brazilian and African sectors. Also, two latitudinal chains of GPS-TEC stations from the equatorial region to low latitudes in the East and West Brazilian sectors and another chain in the East African sector are used to investigate the storm time behavior of the equatorial ionization anomaly (EIA). We noted that the EIA was disturbed in the American and African sectors during the main phase of the geomagnetic storm. Also, the Brazilian sector was more disturbed than the African sector.     

Coronal mass ejection speeds measured in the solar corona using LASCO C2 and C3 images

In this work we present height-time diagrams of 2 halo coronal mass ejections, observed on September 28th, 1997 and June 29th, 1999. The CMEs were observed by the Large Angle and Spectroscopic Coronagraph (LASCO), which observes the solar corona from 2 to 32 solar radii. To obtain these diagrams we divide the LASCO images of a given sequence in angular slices, transform them into rectangular slices (their width chosen proportional to the time distance to the next image) and place them side by side. Thus, the speed profile of any pattern moving in the particular latitudinal slice can be derived. With this method we were able to identify even minor speed changes in several angular positions for the chosen events. This technique is particularly appropriate to identify acceleration or deceleration of structures in halo CMEs.     

A homologous microwave flare on May 29, 1980

Two homologous solar bursts were recorded on May 29, 1980 at 1028 UT and at 1147 UT from the Hale region 16864. The measurements were done at 8 mm wavelength at the Metsähovi Radio Research Station using a 14 meter radio telescope. The time series of the bursts were similar even in the small details. The rise time of both bursts was about 10 seconds and the peak flux density was 3.3 sfu at 1028 UT and 1.2 sfu at 1147 UT. Both bursts were composed of several elementary spikes which were typically 3 seconds apart from each other. The maximum of the gyro-synchrotron type spectrum was close to 15 GHz. The time profile of the bursts, elementary spikes and the frequency spectrum indicated that the origin of these homologous microwave bursts was in a magnetic structure with several loops and that the same complex loop structure was producing energy during both bursts.     

Three dimensional simulation studies on bright points in the solar corona

The interaction phase of the Converging Flux Model (Priest et al., 1994) for the formation of coronal X-ray bright points is investigated self-consistently by means of magnetohydrodynamical simulations. In these simulations the three-dimensional dynamical evolution of two mutually approaching magnetic structures of opposite polarity is studied. During the ideal phase of the approach a current sheet forms in the region above the polarity inversion line and the low-β coronal plasma is compressed and heated locally. Stronger plasma heating on shorter time scales occurs due to magnetic reconnection as soon as a finite anomalous resistivity leads to a violation of the ideal Ohm's law. Both processes together might account for quasi-stationary soft X-ray emissivity of bright points, flaring of tiny filaments within X-ray bright points, and jet-like plasma flows in the vicinity of bright point features.     

The GPS measured SITEC caused by the very intense solar flare on July 14, 2000

This work studies the sudden increases in total electron content of the ionosphere caused by the very intense solar flare on July 14, 2000. Total electron content (TEC) data observed from a Global Positioning System (GPS) network are used to calculate the flare-induced TEC increment, δTEC_f, and variation rate, dTEC_f/dt. It is found that both dTEC_f/dt and δTEC_f are closely related with the solar zenith angles. To explain the observation results, we derived a simple relationship between the partial derivative of the flare-induced TEC, ∂TEC_f/∂t, which is a good approximation for dTEC_f/dt, and the solar zenith angle χ, as well as the effective flare radiation flux I_f, according to the well-known Chapman theory of ionization. The derived formula predicted that ∂TEC_f/∂t is proportional to I_f and inverse proportional to Chapman function ch(χ). This theoretical prediction not only explains the correlation of dTEC_f/dt and δTEC_f with χ as shown in our TEC observation, but also gives a way to deduce I_f from TEC observation of GPS network. Thus, the present work shows that GPS observation is a powerful tool in the observation and investigation of solar flare effects on the ionosphere, i.e., the sudden ionospheric disturbances, which is a significant phenomenon of space weather.     

The 1980 April 12 flare and transient: Report on progress in interpretation

A multidisciplinary study of this solar-interplanetary event is summarized by two main points: this flare was an incident in a process that began days before the flare, and continued after the flare; and the chain of events can be interpreted most simply in terms of energy input over scales of time and space that are large compared to the flare seen in the light of Hα. In support of these points, 5 aspects of the flare are described here: (1) hours before the flare, slow changes in coronal structure were associated with radio continuum emission, suggesting large-scale magnetic-field changes and the presence of energetic electrons; (2) long-lived X-ray loops require sustained energy input for at least an hour after the flare start; (3) interplanetary disturbance near earth is probably related to this limb flare, although the (expected) absence of a shock makes identification uncertain; (4) the coronal mass ejection overlay decaying magnetic field; (5) speed derived from frequency drift of the type II radio burst in the low corona, and from the travel time of the disturbance to 1 a.u., are about twice as great as the observed speed of the coronal mass ejection and of the disturbed solar-wind speed.     

VHF radio response of the near Earth space during solar activity growth in October, 2003

The analysis of observations of very high frequency radio noise intensity at the middle latitude on a frequency f = 500 MHz from 14th till 26th of October, 2003 is presented. These data are compared with the solar radio bursts in the range of frequencies 1–14 MHz registered by RAD2 receiver of the WAVES device installed on board the WIND spacecraft.     

The dose rate observed on 19-21 October 1989 and its modulation by geophysical effects.

The Liulin dosimeter-radiometer on the MIR space station detected the 19 October 1989 high energy solar proton event. These results show that the main particle increase contains protons with energies up to about 9 GeV. After the main particle onset the Liulin dosimeter observed a typical geomagnetic cutoff modulation of the dose rate from the solar particles as the MIR space station traversed magnetic latitudes. When the interplanetary shock and associated solar plasma enveloped the earth on 20 October between 14 and 17 UT the radiation exposure increased significantly due to the lowering of the geomagnetic cutoff. The analysis of this event shows how various geophysical phenomena can significantly modulate the dose rate encountered by earth-orbiting spacecraft.     

Report on COSPAR/SCOR/IUCRM symposium—oceanography from Space,Venice, Italy, 26–30 May 1980

A brief summary is given of the results of oral and poster sessions and informal discussions in the various topics in “Oceanography from Space” discussed at the Venice meeting.     

The ion energy and mass analyzer on board the ‘Intercosmos-Bulgaria-1300’ satellite

An original instrument for ion energy distribution measurement in ionospheric plasma above the F-layer was designed and launched on board the ‘INTERCOSMOS-BULGARIA-1300’ satellite. The instrument performs differential energy analysis of ion species within the two energy ranges of 1 – 27 eV/q and 0.2–8keV/q.     

1998年10月18---19日磁暴主相的行星际源分析

采用高时间分辨率的地磁指数SYM-H, 同时考虑日地连线引力平衡点(L1点)太阳风地磁效应的滞后性, 精确分析了1998年10月18---19日大磁暴主相的行星际源. 分析结果表明, 磁暴主相的行星际源仅为行星际激波和行星际日冕物质抛射之间的太阳风(Sheath), 磁云对磁暴主相没有贡献. 这个磁暴事例的研究表明, 行星际磁场南向分量与太阳风动压的乘积是影响磁暴主相发展的关键参数.