We have studied three Interplanetary Coronal Mass Ejections (ICMEs) having clear signatures of magnetic cloud (MC) arrival at 1 AU and their associated solar sources during 2011 to 2013. Comparing the axial magnetic field strength (B0) of the near-Sun coronal flux-ropes with that of the MC at 1 AU, we have found that the average inferred value of B0 at 1 AU assuming the self-similar expansion of the flux-rope is two times smaller than the value of B0 obtained from the results of MC fitting. Furthermore, by comparing the initial orientation of the flux-rope near the Sun and its final orientation at 1 AU we have found that the three CMEs exhibited more than 80° rotation during its propagation through the interplanetary medium. Our study suggests that although the near-Sun magnetic properties of coronal flux-ropes can be used to infer the field strength of the associated MC at 1 AU, it is difficult to estimate the final orientation of the MC axis in order to predict the geo-effectiveness of the ICMEs.

On 5-6 Aug. 2011 two short-time consecutive M-class solar flares led to profile of multiple Forbush Decreases showing the possible interaction of long-time passing of ICME.

The Global Muon Detector Network (GMDN) is composed by four ground cosmic ray detectors distributed around the Earth: Nagoya (Japan), Hobart (Australia), Sao Martinho da Serra (Brazil) and Kuwait city (Kuwait). The network has operated since March 2006. It has been upgraded a few times, increasing its detection area. Each detector is sensitive to muons produced by the interactions of ~50 GeV Galactic Cosmic Rays (GCR) with the Earth′s atmosphere. At these energies, GCR are known to be affected by interplanetary disturbances in the vicinity of the earth. Of special interest are the interplanetary counterparts of coronal mass ejections (ICMEs) and their driven shocks because they are known to be the main origins of geomagnetic storms. It has been observed that these ICMEs produce changes in the cosmic ray gradient, which can be measured by GMDN observations. In terms of applications for space weather, some attempts have been made to use GMDN for forecasting ICME arrival at the earth with lead times of the order of few hours. Scientific space weather studies benefit the most from the GMDN network. As an example, studies have been able to determine ICME orientation at the earth using cosmic ray gradient. Such determinations are of crucial importance for southward interplanetary magnetic field estimates, as well as ICME rotation.

We have studied the dynamics of the solar active region (AR) NOAA 12192 using full-disc continuum images and the vector magnetograms observed by the Helioseismic and Magnetic Imager (HMI) onboard Solar Dynamics Observatory (SDO). AR 12192 is the largest region of the solar cycle 24. It underwent a noticeable growth and produced 6 X-class, 22 M-class and 53 C-class flares during its disc passage. But the most peculiar fact of this AR is that it was associated with only one CME in spite of producing several X-class flares. In this work, we present the area evolution of this giant sunspot group during the first three rotations when it appeared as AR 12172, AR 12192 and AR 12209, respectively. We have also attempted to make a comparative study of the flare-related photospheric magnetic field and Lorentz force changes for both the eruptive and non-eruptive flares produced by AR 12192.

We present a database of 11 interplanetary shocks associated to coronal mass ejections (CMEs) observed by STEREO and Wind missions between 2006 and 2011 that show evidence of Type II radio burst. For all events, we calculated the principal characteristics of the shock driver, the intensity and geometrical configuration of the in-situ shock and checked for the existence of in-situ type II radio burst. We made a comparative analysis of two CME events (on 18 August 2010 and 4 June 2011), which are apparently associated to two or more magnetic structures which interact in space (i.e. CMEs, SIRs, CIRs). These events show varied shock configurations and intensities. We found evidence of in-situ type II radio bursts in one of the events studied, suggesting that the geometry of the shock (quasi-perpendicularity) is also critical for the generation and/or detection of radio emission in-situ.

Coronal mass ejections (CMEs) are the main source of intense geomagnetic storms when they are earthward directed. Studying their travel time is a key-point to understand when the disturbance will be observed at Earth. In this work, we study the CME that originated the interplanetary disturbance observed on 2013/10/02. According to the observations, the CME that caused the interplanetary disturbance was ejected on 2013/09/29. We obtained the CME speed and estimate of the time of arrival at the Lagrangian Point L1 using the concept of expansion speed. We found that observed and estimated times of arrival of the shock differ between 2 and 23 hours depending on method used to estimate the radial speed.

We report observations of a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in Active Region NOAA 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux rope, using three-dimensional zero–β MHD simulations. We consider a magnetic configuration whose photospheric flux distribution and coronal structure is guided by the observations and a potential field extrapolation. We find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux rope enters an unstable regime characterized by a strong acceleration. Our simulation thus suggests a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots.

The launch of STEREO spacecraft in October 2006 provided an opportunity to view filament eruptions from two viewpoints giving new insights into their three-dimensional (3D) geometry and true trajectory. The kinematical parameters (velocity and acceleration vectors), the rotation motion, non-radial motion and the helical twist around the filament axis in 3D space have been obtained for the first time. All these properties of erupting filaments are very important to our understanding of the physical phenomena triggering the eruption and their early evolution. In the present paper we review different reconstruction techniques of erupting filaments and the main results obtained using the STEREO observations.

During an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection.

Magnetic clouds (MCs) are objects of extreme importance in the heliosphere. They have a major role on releasing magnetic helicity from the Sun (with crucial consequences on the solar dynamo), they are the hugest transient object in the interplanetary medium, and the main actors for the Sun-Earth coupling. The comparison between models and observations is beginning to clarify several open questions on MCs, such as their internal magnetic configuration and their interaction with the ambient solar wind. Due to the decay of the solar wind pressure with the distance to the Sun, MCs are typically in expansion. However, their detailed and local expansion properties depend on their environment plasma properties. On the other hand, while it is well known that the solar cycle determines several properties of the heliosphere, the effects of the cycle on MC properties are not so well understood. In this work we review two major properties of MCs: (i) their expansion, and (ii) the magnetic flux and helicity that they transport through the interplanetary medium. We find that the amount of magnetic flux and helicity released via MCs during the last solar minimum (years 2007-2009) was significantly lower than in the previous one (years 1995-1997). Moreover, both MC size and mean velocity are in phase with the solar cycle while the expansion rate is weakly variable and has no relationship with the cycle.

The large burst of complex type which occurred at the metric, decimetric and microwave wavelengths from 0203 to 0304 UT on 2004 November 10 is analyzed in this present article, some prominent features of this event are obtained from the correlative analysis of this event with the Hα flare and coronal mass ejection (CME) and the radiation process of this event is discussed based on these observational features.

We apply single- and multi-spacecraft techniques to search for currents sheets in the solar wind during the ICME event of 21 January 2005, using the Cluster magnetic field data. Two large-scale currents sheets are detected at the leading boundary of the ICME ejecta using the single-spacecraft technique, which exhibit physical characteristics typical of magnetic reconnection exhausts in the solar wind.

We report on two off-limb radio sources of microwave emission which were detected in one-dimensional RATAN-600 solar scans of the post-eruptive loops: on December 2, 2003 (off west limb) and January 25, 2007 (east limb). The microwave spectra showed that the thermal emission was predominant at the early stage of the arcade formation with a small contribution of non-thermal emission. There were no high-energy particles in these events. The microwave spectra of the radio sources associated with the tops of postflare loops show the predominant thermal emission during one hour after the eruption. In case of a small contribution from accelerated particles to the microwave emission, there is a large amount of hot plasma in the region of the loop tops after the eruption.

The Forbush effects associated with far western and eastern powerful sources on the Sun that occurred on the background of unsettled and moderate interplanetary and geomagnetic disturbances have been studied by data from neutron monitor networks and relevant measurements of the solar wind parameters. These Forbush effects may be referred to a special sub-class of events, with the characteristics like the event in July 2005, and incorporated by the common conditions: absence of a significant disturbance in the Earth vicinity; absence of a strong geomagnetic storm; slow decrease of cosmic ray intensity during the main phase of the Forbush effect. General features and separate properties in behavior of density and anisotropy of 10 GV cosmic rays for this subclass are investigated.

Forbush decrease (or, in a broader sense, Forbush effect) - is a storm in cosmic rays, which is a part of heliospheric storm and very often observed simultaneously with a geomagnetic storm. Disturbances in the solar wind, magnetosphere and cosmic rays are closely interrelated and caused by the same active processes on the Sun. Thus, it is natural and useful to investigate them together. Such an investigation in the present work is based on the characteristics of cosmic rays with rigidity of 10 GV. The results are derived using data from the world wide neutron monitor network and are combined with relevant information into a data base on Forbush effects and large interplanetary disturbances.

We examine the source properties of X-class soft X-ray flares that were not associated with coronal mass ejections (CMEs). All the flares were associated with intense microwave bursts implying the production of high energy electrons. However, most (85%) of the flares were not associated with metric type III bursts, even though open field lines existed in all but two of the active regions. The X-class flares seem to be truly confined because there was no material ejection (thermal or nonthermal) away from the flaring region into space.

A numerical simulation with ENLIL+Cone model was carried out to study the propagation of the shock driven by the 2005 May 13 CME. We then conducted a statistical analysis on a subset of similar events, where a decameter-hectometric (DH) type II radio burst and a counterpart kilometric type II have been observed to be associated with each CME (DHkm CME). The simulation results show that fast CME-driven shocks experienced a rapid deceleration as they propagated through the corona and then kept a nearly constant speed traveling out into the heliosphere. Two improved methods are proposed to predict the fast CME-driven shock arrival time, which give the prediction errors of 3.43 and 6.83 hrs, respectively.

Recent studies show that the cone model with a circular cross section can be used to determine the geometrical and kinematical properties only for a class of halo CMEs with the semi-minor axis of the elliptic halo threading the solar disk center. This work shows how to use an improved cone model with an elliptic cross section to determine the geometrical and kinematical properties for another class of halo CMEs with the semi-major axis threading the solar disk center.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

The sporadic solar radio emission of patrol solar radio observations within the periods 1980, 1984–1989 and of observations with high temporal and spectral resolution in 1989 are used to find the manifestation of pre CMEs activity.To search for other articles by the author(s) go to: http://adsabs.harvard.edu/abstract_service.html