13 research outputs found
Kinematics and helicity evolution of a loop-like eruptive prominence
We aim at investigating the morphology, kinematic and helicity evolution of a
loop-like prominence during its eruption. We use multi-instrument observations
from AIA/SDO, EUVI/STEREO and LASCO/SoHO. The kinematic, morphological,
geometrical, and helicity evolution of a loop-like eruptive prominence are
studied in the context of the magnetic flux rope model of solar prominences.
The prominence eruption evolved as a height expanding twisted loop with both
legs anchored in the chromosphere of a plage area. The eruption process
consists of a prominence activation, acceleration, and a phase of constant
velocity. The prominence body was composed of left-hand (counter-clockwise)
twisted threads around the main prominence axis. The twist during the eruption
was estimated at 6pi (3 turns). The prominence reached a maximum height of 526
Mm before contracting to its primary location and partially reformed in the
same place two days after the eruption. This ejection, however, triggered a CME
seen in LASCO C2. The prominence was located in the northern periphery of the
CME magnetic field configuration and, therefore, the background magnetic field
was asymmetric with respect to the filament position. The physical conditions
of the falling plasma blobs were analysed with respect to the prominence
kinematics. The same sign of the prominence body twist and writhe, as well as
the amount of twisting above the critical value of 2pi after the activation
phase indicate that possibly conditions for kink instability were present. No
signature of magnetic reconnection was observed anywhere in the prominence body
and its surroundings. The filament/prominence descent following the eruption
and its partial reformation at the same place two days later suggest a confined
type of eruption. The asymmetric background magnetic field possibly played an
important role in the failed eruption.Comment: 9 pages, 8 figures, in press in A&
H\alpha\ spectroscopy and multiwavelength imaging of a solar flare caused by filament eruption
We study a sequence of eruptive events including filament eruption, a GOES
C4.3 flare and a coronal mass ejection. We aim to identify the possible
trigger(s) and precursor(s) of the filament destabilisation; investigate flare
kernel characteristics; flare ribbons/kernels formation and evolution; study
the interrelation of the filament-eruption/flare/coronal-mass-ejection
phenomena as part of the integral active-region magnetic field configuration;
determine H\alpha\ line profile evolution during the eruptive phenomena.
Multi-instrument observations are analysed including H\alpha\ line profiles,
speckle images at H\alpha-0.8 \AA\ and H\alpha+0.8 \AA\ from IBIS at DST/NSO,
EUV images and magnetograms from the SDO, coronagraph images from STEREO and
the X-ray flux observations from FERMI and GOES. We establish that the filament
destabilisation and eruption are the main trigger for the flaring activity. A
surge-like event with a circular ribbon in one of the filament footpoints is
determined as the possible trigger of the filament destabilisation. Plasma
draining in this footpoint is identified as the precursor for the filament
eruption. A magnetic flux emergence prior to the filament destabilisation
followed by a high rate of flux cancelation of 1.34 Mx s
is found during the flare activity. The flare X-ray lightcurves reveal three
phases that are found to be associated with three different ribbons occurring
consecutively. A kernel from each ribbon is selected and analysed. The kernel
lightcurves and H alpha line profiles reveal that the emission increase in the
line centre is stronger than that in the line wings. A delay of around 5-6 mins
is found between the increase in the line centre and the occurrence of red
asymmetry. Only red asymmetry is observed in the ribbons during the impulsive
phases. Blue asymmetry is only associated with the dynamic filament.Comment: Accepted by A&A, 18 pages, 16 figure
The Origin, Early Evolution and Predictability of Solar Eruptions
Coronal mass ejections (CMEs) were discovered in the early 1970s when space-borne coronagraphs revealed that eruptions of plasma are ejected from the Sun. Today, it is known that the Sun produces eruptive flares, filament eruptions, coronal mass ejections and failed eruptions; all thought to be due to a release of energy stored in the coronal magnetic field during its drastic reconfiguration. This review discusses the observations and physical mechanisms behind this eruptive activity, with a view to making an assessment of the current capability of forecasting these events for space weather risk and impact mitigation. Whilst a wealth of observations exist, and detailed models have been developed, there still exists a need to draw these approaches together. In particular more realistic models are encouraged in order to asses the full range of complexity of the solar atmosphere and the criteria for which an eruption is formed. From the observational side, a more detailed understanding of the role of photospheric flows and reconnection is needed in order to identify the evolutionary path that ultimately means a magnetic structure will erupt