The discovery of “EIT waves” after the launch of SOHO spacecraft sparked wide interest among the coronal mass ejection (CME) community since they may be crucial to the understanding of CMEs. However, the nature of this phenomenon is still being hotly debated between fast-mode wave explanation and non-wave explanation. Accumulating observations have shown various features of the “EIT waves”. For example, they tend to be devoid of magnetic neutral lines and coronal holes; they may stop near the magnetic separatrix between the source region and a nearby active region; they may experience an acceleration from the vicinity of the source active region to the quiet region, and so on. This paper is aimed to review all these features, discuss how these observations may provide constraints for the theoretical models, and point out their implication to the understanding of CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The majority of flare activity arises in active regions which contain sunspots, while CME activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions, flare related CMEs mainly occur in young active regions containing sunspots and as the magnetic flux of active region is getting dispersed, the filament-eruption related CMEs will become dominant. This is confirmed by statistical analyses.

All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions: (i) the strength of the magnetic field, the amount of possible free energy storage, (ii) the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, canceling flux), and (iii) the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

SCHWENN: About the spiral pattern in the U.Michigan animation: We saw such unwinding spirals. Question: what are they?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

A 2-dimensional Doppler coronagraph “NOGIS” (NOrikura Green-line Imaging System) at the Norikura Solar Observatory, NAOJ, is a unique imaging system that can provide both intensity and Doppler velocity of 2 MK plasma from the green coronal line emission $\lambda$5303 Å of Fe xiv. We present the first detection of a CME onset by NOGIS. The event was originally induced by a C9.1 confined flare that occurred on 2003 June 1 at an active region NOAA $\#$10365 near the limb. This flare triggered a filament eruption in AR 10365, which later evolved into a partial halo CME as well as an M6.5 flare at the same AR 10365 on 2003 June 2. The CME originated in a complex of two neighboring magnetic flux systems across the solar equator: AR 10365 and a bundle of face-on tall coronal loops. NOGIS observed i) a density enhancement in between the two flux systems in the early phase, ii) a blue-shifted bubble and jet that later appeared as (a part of) the CME, and iii) a red-shifted wave that triggered a periodic fluctuations in Doppler shifts in the face-on loops. These features are crucial to understand unsolved problems on a CME initiation (e.g., mass supply, magnetic configuration, and trigger mechanism) and on coronal loop oscillations (e.g., trigger and damping mechanisms). We stress a possibility that interaction between separatrices of the two flux systems played a key role on our event.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We investigated the complex subsurface magnetic rope structure of a super-active region NOAA 10488. With the set of twisted magnetic loop, knot and bifurcate configuration ,we could explain the complicated flux emerging, developing and disappearing by following Tanaka model (Tanaka, 1991). Based on Huairou photospheric vector magnetograms, we calculated the current helicity and found the dominant helicity sign is positive. We deduced that the whole active region might be one twisted magnetic rope.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The continuum energy distributions of R127 and R110 in the outburst phase are fitted by use of a optically envelope model. Both stars show two peaks in the continuum energy distributions in which one lies in the short-wavelength range (near 1250Å) and the other in the optical band. We suggest that the fluxes in the UV and optical bands may have different origins: the UV flux comes from the central star and the optical flux comes from the expanded optically envelope. We construct such a model for LBVs with the use of two LTE atmosphere models with different temperatures, and find it to be in satisfactory agreement with the observed spectral energy distributions of R127 and R110.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

We analyze the formation process of delta configuration in some well-known super active regions based on the photospheric vector magnetogram observations. It is found that the magnetic field in the initial developing stage of some delta active regions shows the potential-like configuration in the solar atmosphere, the magnetic shear develops mainly near the magnetic neutral line with the magnetic islands of opposite polarities, and the large-scale photospheric twisted field forms late gradually. Some results are obtained: (1) The analysis of magnetic writhe of whole active regions cannot be limited in the strong field of sunspots, because the contribution of the fraction of decayed magnetic field is non-negligible. (2) The magnetic model of kink magnetic ropes, proposed to be generated in the sub-atmosphere, is not consistent with the evolution of large-scale twisted photospheric transverse magnetic field and the relationship with magnetic shear in some delta active regions completely.

The photospheric current helicity density is a quantity reflected the local twisted magnetic field and relates to the remain of transfered magnetic helicity in the photosphere, even if the mean current helicity density brings the general chiral property in a layer of solar active regions. As the emergence of new magnetic flux in active regions, the changes of photospheric current helicity density with the injection of magnetic helicity into the corona from the sub-atmosphere can be detected. Because the injective rate of magnetic helicity and photospheric current helicity density contain the different means in the solar atmosphere, the injected magnetic helicity probably is not proportional to its remain (current helicity density) in the photosphere. A evidence is that the rotation of sunspots does not synchronize with the twist of photospheric transverse magnetic field in some active regions (such as, delta active regions) completely, as one believes that the rotation of sunspots reflects the magnetic one and connects with the injection of magnetic helicity. They represent different aspects of magnetic chirality. The synthetical analysis of the observational magnetic helicity parameters actually provides a relative complete picture of magnetic helicity and its transfer in the solar atmosphere.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronal heating is an important problem in solar physics. With the development of highly qualified instruments, such as TRACE, SOHO and Yohkoh, more and more observations about coronal loops have been obtained. The coronal loops' heating, being an important ingredient of coronal heating, has been paid particular attentions recently. But there are still some key issues about the structure and mechanism of the loops' heating unresolved. In this paper, after a brief review on the latest progress in both observations and modeling of coronal loops, we emphatically discuss the heating of hydrostatic loops and hydrodynamic loops based on the 1D model. The prospect of the subject is presented.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Coronal mass ejections (CME) from the solar corona are the most spectacular phenomena of solar activity. Solar physicists are tried to relate CME with other forms of solar activities. CMEs are the result of a large scale rearrangement of solar magnetic field and they are often observed as an eruption of twisted magnetic fields from the solar atmosphere. SOHO/LASCO detected (http://cdaw.gsfc.nasa.gov/CME_list) more than 7500 CMEs during 1996-2003 June. The catalog contains all the CMEs with primary characteristics e.g. linear speed, central position angle, and the angular width. We will use these characteristics to study the variations of CME within these periods. The period starts from the sunspot minimum to entire sunspot maximum range where the solar activity is high. Solar proton events ($E>10MeV$) were collected from NOAA website (http:/www.lep.gsfc.nasa.gov/waves) of the associated CMEs with halo CMEs. We find from CMEs data that the occurrence of average CME rate is 121.51 per month during June 1999 to June 2003 (sunspot maximum range) whereas the occurrence of average CME rate is 41.24 per month during January 1996 to May 1999 (sunspot minimum range), although during the year 1996 (when the average sunspot number is 8.6 per month) occurrence of average CME rate is 18.16 per month. The CME occurrence rate is also correlated with the sunspot numbers with high statistically significant level. The CME number is highest in 2002 but CME is higher in 2000 than in 2001. There is an overall similarity between sunspot number and CME rates but there are differences particularly from June 1999 which is the beginning of the sunspot maximum range. The CME rate peaks in September 2001 to October 2002, which is about 1.25 year after the sunspot maximum. Similarly the average speed of CME at the time of sunspot maximum range and sunspot minimum range are 575 km/sec. and 266 km/sec. respectively. This means that the average speed of CME increases from 1996 to June 2003. The CME speed is also correlated with the sunspot numbers with less significant level than the average rate of CME occurrence. The maximum monthly average speed is about 677.3 km/sec. at the time of April 2001, which is about 5 months earlier than the second sunspot maximum. From the preliminary list of halo CME events from SOHO/LASCO during January 1996 to June 2003 we find that the occurrence rate of average halo CME events during January 1996 to May 1999 is about 1.10 per month whereas during June 1999 to June 2003 is about 4.00 per month, during the year 1996 only two halo CMEs is occurred. We also find that the average speed of halo CME events during sunspot minimum range is 838 km/sec, whereas average speed of the halo CME events during sunspot maximum range is 1000 km/sec. Although during the year 1996 the average speed of halo CME events is 451 km/sec. From the characteristics of halo CMEs in years we find that the number of halo CME increases from 1996 to 2001 and the number of halo CME is maximum in the year 2001, after that number of halo CME decreases. In the 23rd solar cycle maximum solar activity occurred during June to September 2001 we call the time as 2nd sunspot maximum time. We also find that number of high speed ($>1000\,km/sec.$) halo CME is highest during 2nd sunspot maximum range (i.e., during 2001-2002). We find from the halo CME data that average halo CME speed increases from 1996 to 1998 and then decreases from 1998 to 2000 and again increases from 2000 to 2003 and we expect that the average speed of halo CME will decrease after 2003. We find 78 solar proton events ($E >10MeV$) from CME and about 43 of them are from halo CME during 1996 to 2003. We noticed that the maximum solar proton events occurred at the second sunspot maximum, which is occurred after $1\frac12$ sunspot maximum in the 23rd solar cycle. We find there exist 5 phases of solar proton events ($E >10MeV$) data in the 23rd solar cycle. The first phase is at the sunspot minimum, 2nd phase is after two years from the sunspot minimum, 3rd phase is at the time of sunspot maximum and 4th phase occurs just one and half year (usually it is about 2/3 years) after the sunspot maximum and 5th phase occurs 2/3 years before the sunspot minimum. We find six solar proton events ($E >10MeV$) data within 1999 to 2003 with 12900 to 31700 pfu which produced strong geomagnetic storms and all of them are very high-speed halo CME. It is known that very fast CMEs $(V_{p}> 1000$km/sec.) are capable of causing extremely intensive geomagnetic storm when $D_{st} $ index ${<}\,{ -}300nT$. We find that there is a significant correlation between the speed of the CME and solar proton events ($E>10MeV$) data. Solar radius measurement at Rio de Janeiro from 1997-2000 shows that the solar radius varies in phase with the solar cycle. Astrolabes of Antalya, Rio de Janeiro and Santiago suggest that the solar radius varies in phase with the solar cycle. From the detection of solar radius variations with MDI on board SOHO it is found that the solar radius increases with the number of sunspots[l]. It appears that solar radius variation and solar neutrino flux variation with the solar cycle is due to the variation of solar core pulsations and is mainly responsible for the variation of CME and its speed that is in phase with the solar cycle. We suggest that the above-mentioned characteristics are interrelated and that a pulsating solar core may be their common origin [2].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

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