19 research outputs found
Chain Reconnections observed in Sympathetic Eruptions
The nature of various plausible causal links between sympathetic events is
still a controversial issue. In this work, we present multi-wavelength
observations of sympathetic eruptions, associated flares and coronal mass
ejections (CMEs) occurring on 2013 November 17 in two close-by active regions.
Two filaments i.e., F1 and F2 are observed in between the active regions.
Successive magnetic reconnections, caused by different reasons (flux
cancellation, shear and expansion) have been identified during the whole event.
The first reconnection occurred during the first eruption via flux cancellation
between the sheared arcades overlying filament F2, creating a flux rope and
leading to the first double ribbon solar flare. During this phase we observed
the eruption of overlaying arcades and coronal loops, which leads to the first
CME. The second reconnection is believed to occur between the expanding flux
rope of F2 and the overlying arcades of the filament F1. We suggest that this
reconnection destabilized the equilibrium of filament F1, which further
facilitated its eruption. The third stage of reconnection occurred in the wake
of the erupting filament F1 between the legs of overlying arcades. This may
create a flux rope and the second double ribbon flare and a second CME. The
fourth reconnection was between the expanding arcades of the erupting filament
F1 and the nearby ambient field, which produced the bi-directional plasma flows
towards both upward and downward. Observations and a nonlinear force-free field
extrapolation confirm the possibility of reconnection and the causal link
between the magnetic systems.Comment: 37 pages, 17 figures, Accepted for publication in Ap
Interaction of Two Filament Channels of Different Chiralities
We present observations of interactions between the two filament channels of
different chiralities and associated dynamics that occurred during 2014 April
18 -- 20. While two flux ropes of different helicity with parallel axial
magnetic fields can only undergo a bounce interaction when they are brought
together, the observations at the first glance show that the heated plasma is
moving from one filament channel to the other. The SDO/AIA 171 A observations
and the PFSS magnetic field extrapolation reveal the presence of fan-spine
magnetic configuration over the filament channels with a null point located
above them. Three different events of filament activations, partial eruptions,
and associated filament channel interactions have been observed. The activation
initiated in one filament channel seems to propagate along the neighbour
filament channel. We believe that the activation and partial eruption of the
filaments bring the field lines of flux ropes containing them closer to the
null point and trigger the magnetic reconnection between them and the fan-spine
magnetic configuration. As a result, the hot plasma moves along the outer spine
line toward the remote point. Utilizing the present observations, for the first
time we have discussed how two different-chirality filament channels can
interact and show interrelation.Comment: 30 pages, 13 figures, Accepted for Publication in Ap
North South Asymmetry of Different Solar Activity Features During Solar Cycle 23
A study on North South (NS) asymmetry of different solar activity features
(DSAF) such as solar proton events, solar active prominences, H alpha flare
index, soft X ray flares, monthly mean sunspot area and monthly mean sunspot
number were carried out from 1996 to 2008. It is found in our result that solar
cycle 23 is magnetically weak compared to solar cycle 22. Study shows the
Southern dominance of DSAF during the time period of study. During the rising
phase of the cycle the numbers of DSAF approximately equal on the North and
South Hemisphere. However, these activities tend to shift from Northern
Hemisphere to Southern Hemisphere in between year 1998 to 1999. The statistical
significance of the asymmetry time series using a chi square test of goodness
of fit indicates that in most of the cases the asymmetry is highly significant,
i.e., the asymmetry is a real feature in the NS distribution of DSAF.Comment: In this manuscript total 19 pages including 7 figures and 3 table