18,842 research outputs found
Chromospheric evaporation in sympathetic coronal bright points
{Chromospheric evaporation is a key process in solar flares that has
extensively been investigated using the spectroscopic observations. However,
direct soft X-ray (SXR) imaging of the process is rare, especially in remote
brightenings associated with the primary flares that have recently attracted
dramatic attention.} {We intend to find the evidence for chromospheric
evaporation and figure out the cause of the process in sympathetic coronal
bright points (CBPs), i.e., remote brightenings induced by the primary CBP.}
{We utilise the high-cadence and high-resolution SXR observations of CBPs from
the X-ray Telescope (XRT) aboard the Hinode spacecraft on 2009 August 23.} {We
discover thermal conduction front propagating from the primary CBP, i.e., BP1,
to one of the sympathetic CBPs, i.e., BP2 that is 60\arcsec away from BP1.
The apparent velocity of the thermal conduction is 138 km s.
Afterwards, hot plasma flowed upwards into the loop connecting BP1 and BP2 at a
speed of 76 km s, a clear signature of chromospheric evaporation.
Similar upflow was also observed in the loop connecting BP1 and the other
sympathetic CBP, i.e., BP3 that is 80\arcsec away from BP1, though less
significant than BP2. The apparent velocity of the upflow is 47 km
s. The thermal conduction front propagating from BP1 to BP3 was not well
identified except for the jet-like motion also originating from BP1.} {We
propose that the gentle chromospheric evaporation in the sympathetic CBPs were
caused by thermal conduction originating from the primary CBP.}Comment: 9 pages, 5 figure
Blobs in recurring EUV jets
In this paper, we report our discovery of blobs in the recurrent and
homologous jets that occurred at the western edge of NOAA active region 11259
on 2011 July 22. The jets were observed in the seven extreme-ultraviolet (EUV)
filters of the Atmospheric Imaging Assembly (AIA) instrument aboard the Solar
Dynamics Observatory (SDO). Using the base-difference images of the six filters
(94, 131, 171, 211, 193, and 335 {\AA}), we carried out the differential
emission measure (DEM) analyses to explore the thermodynamic evolutions of the
jets. The jets were accompanied by cool surges observed in the H line
center of the ground-based telescope in the Big Bear Solar Observatory. The
jets that had lifetimes of 2030 min recurred at the same place for three
times with interval of 4045 min. Interestingly, each of the jets
intermittently experienced several upward eruptions at the speed of 120450
km s. After reaching the maximum heights, they returned back to the
solar surface, showing near-parabolic trajectories. The falling phases were
more evident in the low- filters than in the high- filters, indicating
that the jets experienced cooling after the onset of eruptions. We identified
bright and compact blobs in the jets during their rising phases. The
simultaneous presences of blobs in all the EUV filters were consistent with the
broad ranges of the DEM profiles of the blobs (),
indicating their multi-thermal nature. The median temperatures of the blobs
were 2.3 MK. The blobs that were 3 Mm in diameter had lifetimes of
2460 s. To our knowledge, this is the first report of blobs in coronal jets.
We propose that these blobs are plasmoids created by the magnetic reconnection
as a result of tearing-mode instability and ejected out along the jets.Comment: 22 pages, 10 figure
Pre-flare coronal dimmings
In this paper, we focus on the pre-flare coronal dimmings. We report our
multiwavelength observations of the GOES X1.6 solar flare and the accompanying
halo CME produced by the eruption of a sigmoidal magnetic flux rope (MFR) in
NOAA active region (AR) 12158 on 2014 September 10. The eruption was observed
by the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamic Observatory
(SDO). The photospheric line-of-sight magnetograms were observed by the
Helioseismic and Magnetic Imager (HMI) aboard SDO. The soft X-ray (SXR) fluxes
were recorded by the GOES spacecraft. The halo CME was observed by the white
light coronagraphs of the Large Angle Spectroscopic Coronagraph (LASCO) aboard
SOHO.} {About 96 minutes before the onset of flare/CME, narrow pre-flare
coronal dimmings appeared at the two ends of the twisted MFR. They extended
very slowly with their intensities decreasing with time, while their apparent
widths (89 Mm) nearly kept constant. During the impulsive and decay phases
of flare, typical fanlike twin dimmings appeared and expanded with much larger
extent and lower intensities than the pre-flare dimmings. The percentage of 171
{\AA} intensity decrease reaches 40\%. The pre-flare dimmings are most striking
in 171, 193, and 211 {\AA} with formation temperatures of 0.62.5 MK. The
northern part of the pre-flare dimmings could also be recognized in 131 and 335
{\AA}.} To our knowledge, this is the first detailed study of pre-flare coronal
dimmings, which can be explained by the density depletion as a result of the
gradual expansion of the coronal loop system surrounding the MFR during the
slow rise of the MFR.Comment: 6 pages, 8 figures, to be accepted for publication by A&
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