We studied the relationship between successive coronal mass ejections (CMEs) and a long-lived geomagnetic storm (LLGMS) by examining the 1998 May 4 event. Five successive CMEs from the same active region and four interplanetary shocks were found to be associated with this LLGMS. We investigated the effect of successive and interacting CMEs on the LLGMS.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We report on a Coronal Mass Ejection (CME) observed on June 27 1999 by the UltraViolet Coronagraph Spectrometer (UVCS) telescope operating on board the SOHO spacecraft. The CME was also observed by LASCO (SOHO). Emission of hot material has been recorded by UVCS propagating in front of an opening system of loops generated by the CME. The evolution of the UVCS structure is highly correlated to the evolution of the opening loop. The data reveal excess broadening of the O VI doublet lines and an enhancement in the intensity of the Si XII$\lambda 520.66$ and $\lambda499.37$ lines due to the motion of the expanding hot gas. The hot gas emission seems to be due to a shock wave propagating in front of a very fast gas bubble traveling along the opening loop system.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Bastille Day Event on July 14 2000, a major solar flare and a global coronal mass ejection (CME), is not a phenomenon of a single active region. Activation and eruption of a huge trans-equatorial filament is seen to precede the simultaneous filament eruption and flare in the source active region, AR9077, and the full halo-CME in the high corona. Evidence of reconfiguration of large-scale structures, manifested by SOHO EIT and Yohkoh SXT observations, is clearly seen. The large-scale magnetic composition related to the trans-equatorial filament and its sheared magnetic arcades appears to be the essential part of the CME parent magnetic structure. Estimations show that the filament-arcade system has enough magnetic helicityto account for the helicity carried by the related CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigate temporal fluctuations in the H$\alpha$ emission profiles of the RS CVn system HR 1099 from a monitoring using the MuSiCoS spectropolarimeter (Observatoire du Pic du Midi, France) in 2001, between December 01 and December 18. Part of the observed emission fluctuations is consistent with rotational modulation, which we interpret as the spectral signature of a dense and complex prominence system trapped in the magnetosphere of HR 1099 and forced to co-rotate with the binary system. The distribution of emitting material is mapped by means of Doppler tomography. We discuss the evolution of prominences over the observing window.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

This work reports direct observations of the magnetic reconnection site during an eruptive process occurring on November 18, 2003. The event started with a rapid expansion of a few magnetic arcades located over the east limb of the Sun and developed an energetic partial halo coronal mass ejection (CME), a long current sheet and a group of bright flare loops in the wake of the CME. It was observed by several instruments both in space and on ground, including the EUV Imaging Telescope, the Ultraviolet Coronagraph Spectrometer, and the Large Angle and Spectrometric Coronagraph experiment on board the Solar and Heliospheric Observatory, the Reuven Ramaty High Energy Solar Spectroscopic Imager, as well as the Mauna Loa Solar Observatory Mark IV K-coronameter. We combine the data from these instruments to investigate various properties of the eruptive process, including those around the current sheet. The composite of images from different instruments and the corresponding results specify explicitly how the different objects developed by a single eruptive process are related to one another.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The degree of polarization of Compton-scattered photospheric light observed in a coronagraph is dependent on the distance of the scattering electrons from the plane of the sky. Measurements of the polarization of light scattered by CME structures have been observed by LASCO C2. We have reduced and analyzed a month long sequence of such measurements which were taken at a cadence of 1 hour. The CME brightness has been distributed throughout a 3 dimensional cube and visualized at a variety of angles. Several CMEs are found to have considerable fine-structure consistent with expanding loop arcades. The analysis is subject to a variety of assumptions such as a lack of knowledge of whether a source is before or behind the plane of the sky. Nevertheless, the results obtained to date are intriguing.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A total of 266 type III bursts observed with the 2.6 - 3.8 GHz high temporal resolution dynamic spectrometer of NAOC during the 23rd solar cycle (from April in 1998 to January in 2003) are statistically analyzed in this present paper. The frequency drift rates (normal and reverse slop), durations, polarizations, bandwidth, starting and ending frequencies are analyzed in detail. From the statistical results of starting and ending frequencies we show that the regions of starting frequencies are very large, which are from less than 2.6 GHz to greater than 3.8 GHz; but the ending frequencies regions are relative concentration, which are from 2.82 GHz to 3.76 GHz. These phenomena mean that the sites of electrons acceleration are quite scatter, while the cutoff regions of the radio type III bursts are in the limiting domain. The bursts number with positive and negative drift rates are nearly equal. This correlation may interpret the suggest that a proportional number of electron beams in the directions of upward and downward are accelerated in the range of 2.6 - 3.8 GHz. The other statistical results are similar to those of decimetric type III bursts as statistics in previous literature. The emission mechanisms of microwave type III bursts are mainly caused by the plasma radiation and electron gyro-maser radiation.

From the statistics of microwave type III bursts and associated coronal mass ejections (CMEs), it is found that the 36% of type III bursts (97) are corresponding to the CMEs for occurring time and site. The correlation between the type III bursts and CMEs is not close, and most type III bursts are occurred in the time regions of 26 – 30 minutes before CMEs. This means that the partial microwave type III bursts may be a precursor of the CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By using the plasma composition data from SOHO/CELIAS/MTOF, charge states data from ACE/SWICS, combining with the remote sensing observations from SOHO/LASCO white-light image and WIND/WAVES radio emission, we describe a coronal mass ejection (CME) observed on 2001 October 19 16:50 UT to show how the effect of CME interaction appears in the in situ measurements. A new narrow shock is formed while the rear CME passing through the core region of the preceding one, which moves faster than the surrounding part and has a new type II radio burst associated with it. Because of its distinguished elemental abundance and unusual low charge states, we connect a density hump observed by MTOF/PM with the preceding CME core. By comparing the relative abundances of minor ions in shock compressive region, ICME region and CME core region with respect to that in upstream slow solar wind, we indicate mass-per-charge dependence of minor thermal ions may be an important imprint of the characteristic velocity of distant acceleration region.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A helical structure in the coronal mass ejection (CME) of 12 September 2000 was observed by the Ultraviolet Coronagraph Spectrometer (UVCS) aboard the Solar and Heliospheric Observatory (SOHO) at heliocentric distances of 3.5 and 6 R$_{\odot}$. A difference of 300 km sec$^{-1}$ in line-of-sight velocities for two segments of the helix obtained from Doppler measurements implies expansion and allows one to distinguish which segment was closest to the observer. The tilt of the segment then determines the handedness. Observed Ly$\alpha$ and C III line emissions indicate that the helix was threaded with filament plasma of varying density. While the helix constituted the bright core of filament plasma, the helix itself was most likely not the pre-existing filament structure.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Due to the optically thin nature of the white light emission, all measurements of the energetics and dynamics of a CME are based on sky-plane projected quantities. The extent and distribution of the CME material along the line of sight is unknown. Thus, CME measurements have an inherent degree of uncertainty. In this paper, I identify the various (possible) sources of errors associated with measurements of CME mass and energy (e.g., instrumental, random, projections effects, etc) and give an error budget for the final measurements. I apply these errors to the statistics of mass and energy for several thousand CMEs observed with LASCO in 1996-2003.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronal mass ejections (CMEs) are intrinsically associated with magnetic structures and evolutions in the solar photosphere. Based on the analysis of vector magnetic field data, we found that: 1, magnetic flux cancellation is the most universal magnetic change in the course of CME onset; 2, new flux emergence also plays an important role in CME origination; 3, interaction and reconnection of flux systems with opposite sign helicity is another key element in the magnetism of CME initiation.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Solar radio fine structures (FSs) may be as an important diagnostics stool to draw the evolution map of the flare loop in the initial phase of solar flares. Also, it may be an important signature of the initial phase of CMEs. Here we analyzed a series of solar radio bursts with drift pulsation structures (DPS) and FSs during the former part of the 23rd solar activity cycle. Found they were associated with CMEs, and got some important statistic conclusions.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Two–and–half–dimensional reconnection is examined for a compressible plasma: Exact solution of jump relations in the system of discontinuities is used to investigate how the outflowing jet and the conditions in the intermediate region depend on the characteristics of the inflow. The most significant implications concerning large-scale eruptive phenomena of solar atmosphere are presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using a 2.5-D, time-dependent ideal MHD model in spherical coordinates, we carry out a numerical study of the equilibrium properties of coronal magnetic flux ropes in a quadrupolar background magnetic field. For such a flux rope system, a catastrophic occurs: the flux rope is detached from the photosphere and jumps to a finite altitude with a vertical current sheet below. There is a transversal current sheet formed above the rope, and the whole system stays in quasi-equilibrium. We argue that the additional Lorentz force provided by the transversal current sheet on the flux rope plays an important role in keeping the system in quasi-equilibrium in the corona.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We present observations of a spectacular eruption of a huge quiescent prominence, which was clearly associated with a coronal mass ejection (CME). The CME consisted of a typical three-part structure: a bright loop-like leading edge, a dark cavity and a bright core. The prominence exhibited a very symmetrical loop-like eruption in low corona and matched well with the bright CME core trailing the CME leading edge. By combining the $H_{\alpha}$, 17GHz and EUV observations with white-light coronagraphs observations, the bright CME core was conclusively identified as the erupting cool, dense prominence material.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In recent times, there has been keen interest in understanding Sun-Earth connection events, such as solar flares, CMEs and concomitant magnetic storms. Magnetic storms are the most dramatic and perhaps important component of space weather effects on Earth. Super-intense magnetic storms (defined here as those with Dst $<$ −500 nT, where Dst stands for the disturbance storm time index that measures the strength of the magnetic storm) although relatively rare, have the largest societal and technological relevance. Such storms can cause life-threatening power outages, satellite damage, communication failures and navigational problems. However, the data for such magnetic storms is rather scarce. For example, only one super-intense magnetic storm has been recorded (Dst=−640 nT, March 13, 1989) during the space-age (since 1958), although such storms may have occurred many times in the last 160 years or so when the regular observatory network came into existence. Thus, research on historical geomagnetic storms can help to create a good data base for intense and super-intense magnetic storms. From the application of knowledge of interplanetary and solar causes of storms gained from the spaceage observations applied to the super-intense storm of September 1-2, 1859, it has been possible to deduce that an exceptionally fast (and intense) magnetic cloud was the interplanetary cause of this geomagnetic storm with a Dst −1760 nT, nearly 3 times as large as that of March 13, 1989 super-intense storm. The talk will focus on super-intense storms of September 1-2, 1859, and also discuss the results in the context of some recent intense storms.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

In order to explain the different average speeds between halo and limb CMEs, we investigate the relationship between the brightness and speed for 17 halo CMEs. It is found that faster CMEs tend to be brighter, which implies that many halo CMEs with slow speeds are missed in observation owing to the limited sensitivity of LASCO detectors or identifications. As a result, the statistical average speed of halo CMEs turns to be much larger than that of limb CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The main drivers of strong geomagnetic activity at the Earth are interplanetary manifestations of coronal mass ejections. A magnetic storm can be caused by compressed sheath fields before the CME, by the CME ejecta or by the combination of these two structures. The most geoeffective subset of CMEs are magnetic clouds. When observed near 1 AU magnetic clouds are characterized by monotonous rotation of magnetic field direction through a large angle, high magnetic field magnitude, low temperature and low plasma beta. We have investigated the magnetic structure and the geomagnetic consequences of magnetic clouds identified from WIND and ACE data for the years 1997-2003. The geomagnetic response of a certain magnetic cloud depends greatly on its magnetic structure and orientation of sheath fields. We have investigated drivers of intense magnetic storms (Dst ¡ −100 nT) during the interval of 1997-2002, i.e. rising, maximum and early declining phases of solar cycle 23. Sheath regions and post-shock streams caused nearly half of all intense storms. Importance of sheath regions as storm drivers even increased as the level of the storm increased. In 2003 two most intense geomagnetic storms of the solar cycle 23 took place. Both of these were driven by southward fields embedded in a magnetic cloud that had axis highly inclined to the ecliptic plane. Though sheath regions alone efficiently drive intense Dst storms (¡ −100 nT) the largest storms (Dst ¡ −300 nT) require exceptionally long-time and intense southward magnetic fields that presumably only magnetic clouds can provide. High solar wind dynamic pressure seems to be important in generating extremely intense Dst storms. As an example we show solar wind condition during Nov 19-20, 2003 magnetic cloud that caused the largest storm of the solar cycle 23.

Magnetic clouds have smoothly changing magnetic field direction combined with low solar wind dynamic pressure. Sheath regions typically have rapidly varying magnetic field direction and high dynamic pressure. Thus, these two solar wind drivers put magnetosphere under different type of driving. We also studied the responses of the Dst index that aims to measure the strength of the equatorial ring current and the Kp index that records more global and higher latitude activity than Dst to different storm drivers. We found that in general sheath regions generate higher Kp activity when compared to the level of the the Dst disturbance than magnetic clouds. In some cases rapidly fluctuating magnetic field in the sheath region caused very strong high-latitude activity (Kp 8-9) though the Dst index was significantly less enhanced. This suggest that magnetospheric current systems have different responses to different solar wind drivers.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Statistics analysis of decimetric type III bursts, coronal mass ejections (CMEs) and H$\alpha$ flares are carried out. The relevant radio events observed from the 625-1500MHz spectrograph at the Yunnan Observatory during the 23rd solar cycle. It is found that the relation between the decimetric type III bursts and CMEs is not closer than that between the type II radio bursts and CMEs; All H$\alpha$ flares generated decimetric type III bursts and correlated with CMEs are all gradual flares. The higher the energy of the flare correspond to the faster the initial velocity of the CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Based on Nançay Radioheliograph (NRH) observations, we have identified 4 Type I noise storm continua sources associated with the Bastille Day flare/CME event. Two of them were stable and closed to active regions. Their outskirts covered AR9077 and 9082, respectively. One source was over the south-west limb and in the high corona, it was stable for hours. All the Type I storm sources weren't observed simultaneously before 10:20 UT at the onset of the global CME, which indicated the intrinsic association of Type I noise storm and CME initiation. The wide span of the Type I storm sources and burst sources clearly implied that the Bastille Day flare/CME involves large or even global magnetic interaction.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html