847 research outputs found
First ALMA Observation of a Solar Plasmoid Ejection from an X-ray Bright Point
Eruptive phenomena such as plasmoid ejections or jets are an important
feature of solar activity with the potential for improving our understanding of
the dynamics of the solar atmosphere. Such ejections are often thought to be
signatures of the outflows expected in regions of fast magnetic reconnection.
The 304 A EUV line of Helium, formed at around 10^5 K, is found to be a
reliable tracer of such phenomena, but the determination of physical parameters
from such observations is not straightforward. We have observed a plasmoid
ejection from an X-ray bright point simultaneously at millimeter wavelengths
with ALMA, at EUV wavelengths with AIA, in soft X-rays with Hinode/XRT. This
paper reports the physical parameters of the plasmoid obtained by combining the
radio, EUV and X-ray data. As a result, we conclude that the plasmoid can
consist either of (approximately) isothermal 10^5 K plasma that is optically
thin at 100 GHz, or else a 10^4 K core with a hot envelope. The analysis
demonstrates the value of the additional temperature and density constraints
that ALMA provides, and future science observations with ALMA will be able to
match the spatial resolution of space-borne and other high-resolution
telescopes.Comment: 10 page, 5 figures, accepted for publication in Astrophysical Journal
Letter. The movie can be seen at the following link:
http://hinode.nao.ac.jp/user/shimojo/data_area/plasmoid/movie5.mp
Photo-induced volume changes in selenium. Tight-binding molecular dynamics study
Tight-binding molecular dynamics simulations of photo-excitations in small Se
clusters (isolated Se ring and helical Se chain) and glassy Se networks
(containing 162 atoms) were carried out in order to analyse the photo induced
instability inside the amorphous selenium. In the cluster systems after taking
an electron from the highest occupied molecular orbital to the lowest
unoccupied molecular orbital a bond breaking occurs. In the glassy networks
photoinduced volume expansion was observed and at the same time the number of
coordination defects changed significantly due to illumination
EUV jets, type III radio bursts and sunspot waves investigated using SDO/AIA observations
Images from the Solar Dynamics Observatory (SDO) at 211A are used to identify
the solar source of the type III radio bursts seen in WIND/WAVES dynamic
spectra. We analyse a 2.5 hour period during which six strong bursts are seen.
The radio bursts correlate very well with the EUV jets coming from the western
side of a sunspot in AR11092. The EUV jet emission also correlates well with
brightening at what looks like their footpoint at the edge of the umbra. For
10-15 min after strong EUV jets are ejected, the footpoint brightens at roughly
3 min intervals. In both the EUV images and the extracted light curves, it
looks as though the brightening is related to the 3-min sunspot oscillations,
although the correlation coefficient is rather low. The only open field near
the jets is rooted in the sunspot. We conclude that active region EUV/X-ray
jets and interplanetary electron streams originate on the edge of the sunspot
umbra. They form along a current sheet between the sunspot open field and
closed field connecting to underlying satellite flux. Sunspot running penumbral
waves cause roughly 3-min jet footpoint brightening. The relationship between
the waves and jets is less clear.Comment: 4 pages, 7 figures, Accepted by A&A Letters. For associated gif
movie, see http://www.mps.mpg.de/data/outgoing/innes/jets/losb_304_211_rd.gi
Observations of a rotating macrospicule associated with an X-ray jet
We attempt to understand the driving mechanism of a macrospicule and its
relationship with a coronal jet. We study the dynamics of a macrospicule and an
associated coronal jet captured by multi-spacecraft observations. Doppler
velocities both in the macrospicule and the coronal jet are determined by EIS
and SUMER spectra. Their temporal evolution is studied using X-ray and He II
304 images. A blueshift of -120+/-15 km/s is detected on one side of the
macrospicule, while a redshift of 50+/-6 km/s is found at the base of the other
side. The inclination angle of the macrospicule inferred from a stereoscopic
analysis with STEREO suggests that the measured Doppler velocities can be
attributed to a rotating motion of the macrospicule rather than a radial flow
or an expansion. The macrospicule is driven by the unfolding motion of a
twisted magnetic flux rope, while the associated X-ray jet is a radial outflow.Comment: 4 pages, 3 figures, accepted for publication in A&
Effect of Frequency and Time of Cutting on the Production of Three Strains of Tropical Forage Legume \u3cem\u3eAeschynomene americana\u3c/em\u3e L. in Drained Paddy Field and Upland Field
The Dry Matter Yield and Nutritive Value of Wet Tolerant Tropical Forage Legumes in Single Cropping or Mixed Cropping with Gramineous Forage Crops in Drained Paddy Field
In Japan the production of rice has been controlled since the 1970\u27s and some parts of the paddy fields have been laid off for forage production. However, in poorly-drained fields or fields with high ground water table, forage species with high tolerance of wet conditions are required. The tropical forage legumes Aeschynomene americana cv. Glenn (Glenn) and Macroptilium lathyroides (L.) Urb. cv. Murray (phasey bean) have a high wet endurance (Bishop et al., 1985; Tobisa et al., 1999) and show high dry matter productivity (Skerman et al., 1988; Tobisa et al., 1999). The objective of this experiment was to evaluate the dry matter yield and nutritive value of Glenn and phasey bean in single cropping or mixed cropping with gramineous forage crops in drained paddy fields
ALMA Discovery of Solar Umbral Brightness Enhancement at {\lambda}=3 mm
We report the discovery of a brightness enhancement in the center of a large
sunspot umbra at a wavelength of 3 mm using the Atacama Large
Millimeter/sub-millimeter Array (ALMA). Sunspots are amongst the most prominent
features on the solar surface, but many of their aspects are surprisingly
poorly understood. We analyzed a {\lambda}=3 mm (100 GHz) mosaic image obtained
by ALMA, which includes a large sunspot within the active region AR12470 on
December 16, 2015. The 3 mm map has a field-of-view and spatial resolution,
which is the highest spatial-resolution map of an entire sunspot in this
frequency range. We find a gradient of 3 mm brightness from a high value in the
outer penumbra to a low value in the inner penumbra/outer umbra. Within the
inner umbra, there is a marked increase in 3mm brightness temperature, which we
call an umbral brightness enhancement. This enhanced emission corresponds to a
temperature excess of 800 K relative to the surrounding inner penumbral region
and coincides with excess brightness in the 1330 and 1400 {\AA} slitjaw images
of the Interface Region Imaging Spectrograph (IRIS), adjacent to a partial
lightbridge. This {\lambda}=3 mm brightness enhancement may be an intrinsic
feature of the sunspot umbra at chromospheric heights, such as a manifestation
of umbral flashes, or it could be related to a coronal plume since the
brightness enhancement was coincident with the footpoint of a coronal loop
observed at 171 {\AA}.Comment: 16 pages, 5 figures, accepted for publication in ApJ Lette
A window to the amygdala: concurrent encoding of choice preference in multi-unit activity in the amygdala and in eye movements
Jets in coronal holes: Hinode observations and 3D computer modelling
Recent observations of coronal hole areas with the XRT and EIS instruments
onboard the Hinode satellite have shown with unprecedented detail the launching
of fast, hot jets away from the solar surface. In some cases these events
coincide with episodes of flux emergence from beneath the photosphere. In this
letter we show results of a 3D numerical experiment of flux emergence from the
solar interior into a coronal hole and compare them with simultaneous XRT and
EIS observations of a jet-launching event that accompanied the appearance of a
bipolar region in MDI magnetograms. The magnetic skeleton and topology that
result in the experiment bear a strong resemblance to linear force-fee
extrapolations of the SOHO/MDI magnetograms. A thin current sheet is formed at
the boundary of the emerging plasma. A jet is launched upward along the open
reconnected field lines with values of temperature, density and velocity in
agreement with the XRT and EIS observations. Below the jet, a split-vault
structure results with two chambers: a shrinking one containing the emerged
field loops and a growing one with loops produced by the reconnection. The
ongoing reconnection leads to a horizontal drift of the vault-and-jet
structure. The timescales, velocities, and other plasma properties in the
experiment are consistent with recent statistical studies of this type of
events made with Hinode data.Comment: 10 pages, 4 figures. Revised version submitted to ApJ Letter
Observations of a pulse driven cool polar jet by SDO/AIA
Context. We observe a solar jet at north polar coronal hole (NPCH) using SDO
AIA 304 {\deg}A image data on 3 August 2010. The jet rises obliquely above the
solar limb and then retraces its propagation path to fall back. Aims. We
numerically model this observed solar jet by implementing a realistic (VAL-C)
model of solar temperature. Methods. We solve two-dimensional ideal
magnetohydrodynamic equations numerically to simulate the observed solar jet.
We consider a localized velocity pulse that is essentially parallel to the
background magnetic field lines and initially launched at the top of the solar
photosphere. The pulse steepens into a shock at higher altitudes, which
triggers plasma perturbations that exhibit the observed features of the jet.
The typical direction of the pulse also clearly exhibits the leading front of
the moving jet. Results. Our numerical simulations reveal that a large
amplitude initial velocity pulse launched at the top of the solar photosphere
produces in general the observed properties of the jet, e.g., upward and
backward average velocities, height, width, life-time, and ballistic nature.
Conclusions. The close matching between the jet observations and numerical
simulations provides first strong evidence for the formation of this jet by a
single velocity pulse. The strong velocity pulse is most likely generated by
the low- atmospheric reconnection in the polar region which results in
triggering of the jet. The downflowing material of the jet most likely vanishes
in the next upcoming velocity pulses from lower solar atmosphere, and therefore
distinctly launched a single jet upward in the solar atmosphere is observed.Comment: 8 pages, 4 figures, A&
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