Large Solar Energetic Particles (SEPs) are closely associated with coronal mass ejections (CMEs). The significant correlation observed between SEP intensity and CME speed has been considered as the evidence for such a close connection. The recent finding that SEP events with preceding wide CMEs are likely to have higher intensities compared to those without was attributed to the interaction of the CME-driven shocks with the preceding CMEs or with their aftermath. It is also possible that the intensity of SEPs may also be affected by the properties of the solar source region. In this study, we found that the active region area has no relation with the SEP intensity and CME speed, thus supporting the importance of CME interaction. However, there is a significant correlation between flare size and the active region area, which probably reflects the spatial scale of the flare phenomenon as compared to that of the CME-driven shock.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By using the observations of the Extreme-UV Imaging Telescope (EIT), we studied three major solar eruptions from the same super active region NOAA 10486 during the interval of October 26 to November 04, 2003. The three eruptions took place when the active region located on the eastern hemisphere, near the central meridian and on the western limb, respectively. In the first event (Oct 26 event), the coronal disturbance (indicated as an EIT wave) in EUV images was limited east to the central meridian, and there were no solar energetic particles (SEPs) detected. The second event (Oct 28 event) accompanied a nearly entire disk disturbance and very large and prompt SEP enhancements. For the last event (Nov 04 event), there was no obvious coronal disturbance on the disk, and the SEP enhancements were much more gradual. From these observational features, we suggest that different coronal disturbances correspond to different acceleration and propagation histories. A large-scale, cross-disk coronal disturbance may open quite a lot of magnetic field lines in the low corona, facilitating the direct access of flare accelerated SEPs to the Sun-Earth connected interplanetary magnetic field lines. Subsequently the SEP intensity will exhibit a very prompt enhancement.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We studied the association between SEP events during 1977-2003 and related CMEs and found each GLE event was associated with a primary CME, which was faster (average speed $\sim$1762 $km \cdot s^{-1}$) and wider (average angle width of $317^{0}$) than an average CME . All SEP-related CMEs distributed within solar source regions of latitude strip of S$30^{0}$-N$40^{0}$, while 11 (85%)GLE-related CMEs originated from the western hemisphere. These fast halo CMEs (75% full-halo and 25% partial-halo) were associated with type II radio bursts in the decameter hectometer (DH) wavelengths.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We studied the solar proton differential energy spectra with energy range of 1$\sim$500 MeV at several time intervals during the 2000 July 14 solar flare. The results showed that before flare the spectra could be described by a power law function and after flare the power law spectra still existed above 30 MeV although spectra became softer with time. There was a spectral “knee” occurring at $\sim$30 MeV. We constructed a solar proton differential spectrum from 30 MeV to 3 GeV at peak flux time 10:30 UT and fitted it in the same manner. On the basis of a supposition of having the same power law spectrum in higher energy, we calculated the solar proton integrated fluxes in energy range of from 500 MeV to 20 GeV and compared them with other results obtained from experimental, modeling and theoretical calculations in other big historic SEP events.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

On acceleration of relativistic electrons by any means, the coherent pinch effect brings the relativistic electrons together. The inclusion of a suitable number of positive ions, preferentially heavy ions would stabilize the beam. The heavy trapped nuclei would have to go with the electrons, thus acquire relativistic speeds. The electron beam may be divided into small bunches. This mechanism can accelerate positive nuclei to GeV and TeV energies during solar flares, stellar and galactic high energy events. During the acceleration of 1000 GeV electron bunches, the energy gained by trapped positive nuclei is estimated to reach 10$^{15}$ eV per nucleon. Higher energies can be achieved by head on collision as the energy gained by the target nucleus is proportional to $\gamma^{2},$ however fission reactions and very high energy gamma rays may occur. The principle of this mechanism is applied in electron-ring accelerators.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Heliospheric models of Coronal Mass Ejection (CME) propagation and evolution provide an important insight into the dynamics of CMEs and are a valuable tool for interpreting interplanetary in situ observations. Moreover, they represent a virtual laboratory for exploring conditions and regions of space that are not conveniently or currently accessible by spacecraft. In this review I summarize recent advances in modeling the properties and evolution of CMEs in the solar wind. In particular, I will focus on: (1) the types of ICME models; (2) the boundary conditions that are imposed; (3) the role of the ambient solar wind; (4) predicting new phenomena; and (5) distinguishing between competing CME initiation mechanisms. I will conclude by discussing what topics will likely be important for models to address in the future.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Magnetic clouds are extended and magnetized plasma structures that travel from the Sun toward the outer heliosphere, carrying an important amount of magnetic helicity. The magnetic helicity quantifies several aspects of a given magnetic structure, such as the twist, kink, and the number of knots between magnetic field lines, the linking between magnetic flux tubes, etc. Since the helicity is practically conserved in the solar atmosphere and the heliosphere, it is a useful quantity to compare the physical properties of magnetic clouds to those of their solar source regions. In this work we describe a method that, assuming a cylindrical geometry for the magnetic cloud structures, allows us to calculate their helicity (per unit length) content directly from the observed magnetic field values. We apply the method to a set of 20 magnetic clouds observed by the WIND spacecraft. To test its reliability we compare our results with the helicity computed using a linear force-free field model under cylindrical geometry (i.e. Lundquist's solution).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

We describe a study of the compositional properties of heliospheric ICME ejecta within the context of solar CME observations. In this study, we examine CME-ICME pairs with an associated flare. For each of these pairs several in situ quantities are averaged over the event and compared with flare magnitude. We find that Mg/O, He/O, and He/H are clearly correlated with flare magnitude suggesting that larger flares provide the CMEs with increased access to the low corona. We also find flare magnitude is positively correlated with velocity and negatively correlated with density, indicating that CMEs which are related to large flares are more likely to experience over-expansion during their propagation to 1 AU.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

From all the transient events identified in interplanetary space by in-situ measurements, Magnetic Clouds (MCs) are among the most intriguing ones. They are a special kind of Interplanetary Coronal Mass Ejections (ICMEs), characterized by a well-defined magnetic field configuration. We use a list of 40 MCs detected by Ulysses to study bidirectional flows of protons in the $\sim$0.5 MeV energy range. Solar wind ions are also analysed in order to compare cloud to non-cloud ICMEs.

The enhancement in freezing-in temperatures inside the clouds, obtained with data from the SWICS instrument, provides insights into processes occurring early during the ejection of the material and represents a complementary tool to differentiate cloud from non-cloud ICMEs. At higher energies, directional information for protons obtained with the EPAC instrument allows a comparison with previous results concerning bidirectional suprathermal electrons. The findings are qualitatively comparable. Apparently, the portion of bidirectional flows inside magnetic clouds is neither heavily dependent on distance from the Sun nor on parameters obtained from a flux rope model.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

An analytical method is used to model a magnetic field distribution in the vicinity of a large interplanetary or solar flux rope. The field is a sum of the pre-existing one and an additional current-free part. An example using real data is shown.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The paper describes our approach to simulations of real interplanetary events, consisting of four steps: (i) determination of background solar wind, (ii) parameterization of a model flux rope, (iii) launching it into the solar wind, and (iv) calculating its propagation and evolution.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

It is an important subject of space weather to forecast accurate arrival time of interplanetary coronal mass ejections (ICMEs) at the Earth. Determination of initial speeds of CMEs is an important factor for this. Here, we estimated the initial speeds of CMEs using solar wind observations near 1 AU and compared these speeds with CME speeds measured by the SOHO coronagraph.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Observations of the low solar corona, in particular in the EUV, are an effective means of identifying the solar sources of coronal mass ejections (CMEs). SOHO/EIT, with its continuous 24 hours per day coverage, is well suited to perform this task. Source regions and start times of frontside full and partial halo CMEs (that may be geoeffective) can thus be determined. The most frequent EUV signatures of CMEs are coronal dimmings. EIT waves, eruptive filaments and post-eruption arcades are also reliable signatures. Frontside halo CMEs with source regions close to the solar disc center have the strongest chance to hit the Earth. The inspection of the EIT data together with photospheric magnetograms may give an idea about the ejected interplanetary flux rope magnetic field and, in particular, about the presence or absence of southward (geoeffective) field. If a source region is situated close to the solar limb, the corresponding CME also may be geoeffective, as the CME-driven shocks have large angular extent. In this case the storm can be produced by the sheath plasma behind the shock, provided it contains strong enough southward interplanetary magnetic field. Some implications for the operational space weather forecast are discussed. EIT and LASCO are capable to identify the solar sources of the most of geomagnetic storms. In some cases, however, the identification is uncertain, so the observations by the future STEREO mission will be needed for the investigation of similar events.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

By investigating ten typical magnetic clouds (MCs) associated with large geomagnetic storms (Dst $\leq-100$ nT) from 2000 to 2003, the geoeffectiveness of MCs with various orientations is addressed. It is found that the Dst peak values during the geomagnetic storms are well estimated by applying flux rope model to these magnetic clouds. A high correlation between estimated and observed Dst values is obtained. Moreover, the effect of orientations of MCs on intensities of geomagnetic storms is studied. It is found that the favorable orientations of MCs are approximately at $\theta\sim70^{\circ}$ and $\phi\sim40^{\circ}$ in GSE coordinates to cause large geomagnetic storms. Further, by analyzing solar observations of four associated erupted filaments, the question who determine the orientations of MCs is studied. The likelihood of predicting the intensities of a geomagnetic storms several tens hours before their occurrences is also discussed.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Shocks driven by energetic coronal mass ejections and other interplanetary transients are mainly responsible for large disturbances in geomagnetic field of Earth and play a key role in producing a geomagnetic storm or substorm. A geomagnetic storm is a global disturbance in Earth's magnetic field usually occurred due to abnormal conditions in the IMF and solar wind plasma emissions caused by various solar phenomenon. Identifying intense geomagnetic storms with Dst decrease more than/or equal to 300 nT occurred during 1981-2001, a correlative study has been performed to analyze the associated solar and interplanetary causes of these 09 events using solar wind plasma, IMF and solar geophysical data. It is observed statistically that 55% storms have occurred during solar maximum and 45% occurred during minimum phase of solar cycles. Further, study reveals that 77% intense storms are associated with CMEs, which confirms earlier findings.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 Geospace Double Star Project (DSP) contains two satellites operating in the near-earth equatorial and polar regions respectively. The tasks of DSP are: (i) to provide high-resolution field, particle and wave measurements in several important near-earth magnetosphere active regions which have not been covered by existing ISTP missions in the geospace, such as the near-earth plasma sheet and its boundary layer, the ring current, the radiation belts, the dayside magnetopause boundary layer, and the polar region; (ii) to investigate the trigger mechanisms of magnetic storms, magnetospheric substorms, and magnetospheric particle storms, as well as the responses of geospace storms to solar activities and interplanetary disturbances; (iii) to set up the models describing the spatial and temporal variations of the near-earth space environment. To complete the mission, there are eight instruments on board the equatorial satellite and the polar satellite, respectively. The orbit of the equatorial satellite with a perigee at 565.5km and an apogee at 78959.9km, and the inclination is 28.17 ; while the orbit of the polar satellite is proposed with a perigee at 700km and an apogee at 40000km, as well as an inclination about 90. The equatorial satellite has been launched successfully in December 2003. Now the equatorial satellite (TC-1) and instruments operate normally. Payloads have provided good quality of data of fields and particles. Already very good conjunction in the dayside magnetopause and magnetotail with Cluster, CME effects could be investigated. The first results of data analysis have already shown great interesting. The polar (TC-2) satellite has been launched successfully in July 2004. Now the satellite operates normally. The commissioning of the payload has started since the end of July 2004 and will be finished in the middle of Sep.2004. The instrument has been normally operation and downlink the data.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Using data from ACE and low-altitude polar orbit satellite of NOAA, we investigate the possible sources of the enhancements of relativistic electrons in the magnetosphere. The observations from NOAA for the different geomagnetic activity periods show that substorms injections provide seed electrons for MeV electron enhancement associated with geomagnetic storms and the energetic electrons in the solar wind provide an alternative source for the relativistic electrons in the magnetosphere during the SEP events.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Solar prominences can be viewed as pre-eruptive states of coronal mass ejections (CMEs). Eruptive prominences are the phenomena most related to CMEs observed in the lower layers of the solar atmosphere. The most probable initial magnetic configuration of a CME is a flux rope consisting of twisted field lines which fills the whole volume of the dark cavity stretched in the corona along the photospheric polarity inversion line. Cold dense prominence matter accumulates in the lower parts of helical flux tubes, which serve as magnetic traps in the gravitation field. Coronal cavity is rather inconvenient feature for observation owing to reduced emission, so prominences and filaments are the best tracers of the flux ropes in the corona long before the beginning of eruption. Thus, the problem of the CME prediction can be reduced to the analysis of the filament equilibrium and estimation of the stability store. The height of a prominence (or a filament when observed against the disk) increases with its age and the death of a filament is usually an eruption which is followed by a CME. The filament height, then, can be a measure of its age and its readiness for eruption. In inverse-polarity models the equilibrium height of a filament is related to the value of the filament electric current. The stronger the electric current, the greater the height of the filament. However, the equilibrium and stability of a filament depend not only on its current but also on the characteristics of the external magnetic field. In order to estimate the probability of eruption, we should therefore compare the observed prominence height with a value characterizing the photospheric magnetic field. This value is the critical height, which can be found in the distribution of the magnetic field vertical gradient above the polarity inversion line. We had analyzed three dozens of filaments and found that eruptive prominences were near the limit of stability a few days before eruptions. We believe that the comparison of the real heights of prominences with the calculated critical heights could be a basis for predicting filament eruptions and following CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html