Equilibria and evolutions in the coronal magnetic configurations due to the interactions among active regions are investigated. The magnetic structure includes a current-carrying flux rope that is used to model the prominence or filament. We use either two dipoles or four monopoles on the boundary surface to model active regions, and the change in the boundary conditions corresponds to either the horizontal motion of magnetic sources or decaying of the active regions. Both cases show the catastrophic behavior in the system's evolutions. The results have important observational consequences: most eruptive prominences that give rise to CMEs are driven by the interactions between two or more active regions. Such eruptions may not necessarily take place in the growing phase of the active regions, instead they usually occur at the decay phase.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A brief review is given on the progress made in the study of the catastrophe of coronal magnetic flux ropes with implication in coronal mass ejections (CMEs). Relevant studies have been so far limited to 2.5-D cases, with a flux rope levitating in the corona, either parallel to the photosphere in Cartesian geometry or encircling the Sun like a torus in spherical geometry. The equilibrium properties of the system depend on the features of the flux rope and the surrounding background state. Under certain circumstances, the flux rope exhibits a catastrophic behavior, namely, the rope loses equilibrium and erupts upward upon an infinitesimal variation of any control parameter associated with the background state or the flux rope. The magnetic energy of the system right at the catastrophic point may exceed the corresponding open field energy so that after the background field is opened up by the erupting flux rope, a certain amount of magnetic free energy is left for the heating and acceleration of coronal plasma against gravity. The flux rope model has been used to reveal the common features of CMEs and to simulate typical CME events, proving to be a promising mechanism for the initiation of CMEs. Incidentally, the Aly conjecture on the maximum magnetic energy of force-free fields places a serious constraint on 2.5-D flux models. Nevertheless, current sheets must form during a catastrophe on the Alfvén timescale, and magnetic reconnection across the newly formed current sheets may contribute to circumventing such a constraint. In this sense, the catastrophe simply plays a role of driver for the fast magnetic reconnection, and a combination of them is thus responsible for the initiation of CMEs.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

A coronal current-free field model, which applies the asymptotic condition of no field at infinity and the boundary condition on the solar surface specified, is presented. Some Applications of the method to practical solar events indicate that the extrapolated global magnetic field structures effectively demonstrate the case for the disk signature of the radio CME and the evolution of the radio sources during the CME/flare processes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Tokamak physics shows that there will be a neoclassical effect in current-carrying plasma loops. We apply the theory to solar coronal loops and hope to find a fast magnetic reconnection mechanism for understanding solar flares and CMEs.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

Based on the dynamics of charged particles in plasma with the two-fluid description, the equation for magnetic field generation and maintenance is derived. The nature of magnetic field in cosmic plasma and the generation can be understood from the equation. The ions and electrons are considered as two independent fluids with the collision connected. Due to the different viscosity between ions and electrons, there will be a velocity difference in ions and electrons. This causes a current in the plasma and generates magnetic field. IN the plasma system, the differential velocities and the viscous forces of the electrons are the source of magnetic field.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

A three-dimensional, time-dependent, magnetohydrodynamic (MHD) model is constructed for the study of active region (AR) evolution. The new physics included in this model is differential rotation, meridional flow, effective diffusion and cyclonic turbulence effects, which means, that the photospheric shear is automatically generated instead of prescribed as is usually done for modeling. To benchmark this newly developed model, we have used observed active region NOAA/AR-8100 (October 29 - November 3, 1997) to verify the model by computation of the total magnetic flux and magnetic field maps of that active region. Then, we apply this model to compute the non-potentiality magnetic field parameters for possible coronal mass ejection production. These parameters are: (i) magnetic flux content ($\Phi$), (ii) the length of strong shear, strong-field main neutral line, ($L_{ss}$), (iii) the net electric current ($I_N$) and (iv) the flux normalized measure of the field twist ($\alpha$ = $\mu$$\frac{I_N}{\Phi}$). These parameters are compared with the measured values which showed remarkable agreement.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

A distinctive characteristic of interplanetary magnetic clouds is their rope-like magnetic structure, i.e., their smoothly-varying helical field lines whose pitch increases from their core to their boundary. Because this regular structure helps to make MCs particularly geo-effective, it is important to understand how it arises.

We discuss recent work which relates the magnetic and topological parameters of MCs to associated solar active regions. This work strongly supports the notion that MCs associated with active region eruptions are formed by magnetic reconnection between these regions and their larger-scale surroundings, rather than simple eruption or entrainment of pre-existing structures in the corona or chromosphere. We discuss our findings in the context of other recent works on both the solar and interplanetary sides, including ion composition and various MHD models of magnetic cloud formation.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

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

We examine the energetics of the best examples of flux-rope CMEs observed by LASCO in 1996-2001. We find that 69% of the CMEs in our sample experience a driving power in the LASCO field of view. For these CMEs which are driven, we examine if they might be deriving most of their driving energy by coupling to the solar wind. We do not find conclusive evidence to support this hypothesis. We adopt two different methods to estimate the energy that can possibly be released by the internal magnetic fields of the CMEs. We find that the internal magnetic fields are a viable source of driving power for these CMEs.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

After a brief overview of solar energetic particle (SEP) emission from coronal mass ejection (CME) shocks, we turn to a discussion of their transport and acceleration. The high energy SEP are accelerated near the Sun, and because of their well-known source location, their transport can be modeled quantitatively to obtain precise information on the injection function (number of particles emitted vs. time), including a determination of the onset time to within 1 min. For certain events, transport modeling also indicates magnetic topology with mirroring or closed field loops. Important progress has also been made on the transport of low energy SEP from very strong events, which can display exhibit interesting saturation effects and compositional variations. The acceleration of SEP by CME-driven shocks in the interplanetary medium is attributed to diffusive shock acceleration, but the spectrum of SEP production is typically modeled empirically. Recent progress has largely focused on using detailed composition measurements to determine fractionation effects of shock acceleration and even to clarify the nature of the seed population. In particular, there are many indications that the seed population is suprathermal (pre-energized) and the injection problem is not relevant to acceleration at interplanetary CME-driven shocks. We argue that the finite time available for shock acceleration provides the best explanation of the high-energy rollover.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Very large solar energetic particle (SEP) events occur at the rate of about 10 per year during solar maximum. The primary accelerators in these events are shocks driven by fast coronal mass ejections, in which speeds are greater than about 1000 km/s. Solar Cycle 23 probably produced the largest fluence of > 10 MeV/nucleon SEPs seen since the start of the Space Age. New instruments on Wind, ACE, SOHO, and other satellites have provided unprecedented detail on the energy spectra, elemental and isotopic composition, ionic charge states, and temporal evolution of these SEP events, as well as their associated CMEs and flares. In this talk, I will review some of the new insights provided by these data. A particular challenge in SEP studies has been the very large event-to-event variability in composition and spectral characteristics, particularly at energies above a few tens of MeV per nucleon. I will discuss recent efforts to understand this variability in terms of seed populations and shock geometry. I will also review recent studies of the time at which SEPs first appear on the Sun-Earth magnetic field line and the implications of these studies for the conditions under which SEP production was initiated.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Gradual solar energetic particle (SEP) events are now believed to be associated with CME-driven shocks. As the shock propagates out from the Sun, particles are accelerated diffusively at the shock front and some will escape upstream and downstream into the interplanetary medium. This is in contrast with “impulsive” events, which are believed to be due to solar flares. However, recent observations have found that in some gradual SEP events, the time intensity profile show a two peak feature, suggesting a mixture of particles from solar flares with particles from CME-driven shock. Furthermore, the observed spectra of large SEP events show tremendous variability. The $Fe/C$ ($Fe/O$) ratio behave oppositely in events which have similar solar progenitors. In this work, we use a numerical model to follow particle acceleration and transport at CME-driven shocks. We investigate a possible scenario for the re-acceleration of flare particles by CME-driven shocks and calculate the $Fe/O$ ratio for two exemple shocks. These simulations are helpful in interpreting observations of particle data obtained in situ at 1 AU by spacecraft such as ACE and WIND.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The solar sources of near-relativistic $(E > $30 keV) electron events observed at 1 AU are poorly understood. In general, the solar injection times deduced from the observed 1 AU onset times and assumed 1.2 AU travel distances yield injection times about 10 minutes after the associated flare impulsive phases and type III radio burst times. One interpretation is that the apparent delays occur in the interplanetary medium, probably due to scattering of the electrons. If the injection times are delayed from the impulsive phases, the electron acceleration might take place in CME-driven shocks. Here a large number of electron events observed with the UC/Berkeley 3DP detector on the Wind spacecraft are compared with CMEs observed by the Lasco coronagraph on SOHO and with type II bursts observed by the 40 to 800 MHz radio receiver at the Astrophysikalisches Institut Potsdam (AIP) and by the 20 kHz to 14 MHz WAVES instrument on the Wind spacecraft. The acceleration of at least some of the electron events is not consistent with the shock hypothesis.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Based on the solar energetic particle (SEP) data from ACE and GOES satellites, the acceleration of SEP by CME-driven shock in interplanetary space was investigated. The results showed that the acceleration process of SEP by the Bastille CME-driven shock ran through the whole space from the sun to the magnetosphere. The highest energy of SEP accelerated by the shock was greater than 100MeV. A magnetic bottle associated with the CME captured a lot of high energy particles with some of them having energy greater than 100MeV. Based on magnetic field data of solar wind observed by ACE data, we found that the the magnetic bottle associated with the Bastille CME was the sheath caused by the CME in fact.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

The Ulysses spacecraft has now completed its second orbit over the poles of the Sun. Energetic particles associated with CMEs were observed at the highest latitudes over both poles, quite unlike the first polar pass when virtually no CME or CIR accelerated particles were observed at the very highest latitudes. We present observations of solar energetic particle events observed in the energy range $\sim$1 MeV to $\sim$100 MeV made by the COSPIN instrument, when the spacecraft was at high heliographic latitude over the northern pole, above the current sheet, and immersed in high-speed solar-wind flow coming from the northern polar coronal hole. We discuss the rise to maximum, the onset time and the anisotropy of the energetic particles. We find that, unlike the events observed at mid and low latitudes, the particle angular distributions were almost isotropic, but with a net outward flow along the magnetic field lines. We compare these events with other events observed at lower latitudes.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html

Solar energetic particle (SEP) fluxes measured by the ULYSSES (ULS)/HI-SCALE experiment during its second polar orbit as well as by the identical ACE/EPAM experiment at 1 AU are utilized as diagnostics of the large-scale structure and topology of the Interplanetary Magnetic Field (IMF) embedded within Interplanetary Coronal Mass Ejections (ICMEs). Survey results are also reported.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html