544 research outputs found
Observations of solar small-scale magnetic flux-sheet emergence
Aims. Moreno-Insertis et al. (2018) recently discovered two types of flux
emergence in their numerical simulations: magnetic loops and magnetic sheet
emergence. Whereas magnetic loop emergence has been documented well in the last
years, by utilising high-resolution full Stokes data from ground-based
telescopes as well as satellites, magnetic sheet emergence is still an
understudied process. We report here on the first clear observational evidence
of a magnetic sheet emergence and characterise its development.
Methods. Full Stokes spectra from the Hinode spectropolarimeter were inverted
with the SIR code to obtain solar atmospheric parameters such as temperature,
line-of-sight velocities and full magnetic field vector information.
Results. We analyse a magnetic flux emergence event observed in the quiet-sun
internetwork. After a large scale appearance of linear polarisation, a magnetic
sheet with horizontal magnetic flux density of up to 194 Mx/cm hovers in
the low photosphere spanning a region of 2 to 3 arcsec. The magnetic field
azimuth obtained through Stokes inversions clearly shows an organised structure
of transversal magnetic flux density emerging. The granule below the magnetic
flux-sheet tears the structure apart leaving the emerged flux to form several
magnetic loops at the edges of the granule.
Conclusions. A large amount of flux with strong horizontal magnetic fields
surfaces through the interplay of buried magnetic flux and convective motions.
The magnetic flux emerges within 10 minutes and we find a longitudinal magnetic
flux at the foot points of the order of Mx. This is one to two
orders of magnitude larger than what has been reported for small-scale magnetic
loops. The convective flows feed the newly emerged flux into the pre-existing
magnetic population on a granular scale.Comment: 6 pages, 5 figures, accepted as a letter in A&
Temporal relation between quiet-Sun transverse fields and the strong flows detected by IMaX/SUNRISE
Localized strongly Doppler-shifted Stokes V signals were detected by
IMaX/SUNRISE. These signals are related to newly emerged magnetic loops that
are observed as linear polarization features. We aim to set constraints on the
physical nature and causes of these highly Doppler-shifted signals. In
particular, the temporal relation between the appearance of transverse fields
and the strong Doppler shifts is analyzed in some detail. We calculated the
time difference between the appearance of the strong flows and the linear
polarization. We also obtained the distances from the center of various
features to the nearest neutral lines and whether they overlap or not. These
distances were compared with those obtained from randomly distributed points on
observed magnetograms. Various cases of strong flows are described in some
detail. The linear polarization signals precede the appearance of the strong
flows by on average 84+-11 seconds. The strongly Doppler-shifted signals are
closer (0.19") to magnetic neutral lines than randomly distributed points
(0.5"). Eighty percent of the strongly Doppler-shifted signals are close to a
neutral line that is located between the emerging field and pre-existing
fields. That the remaining 20% do not show a close-by pre-existing field could
be explained by a lack of sensitivity or an unfavorable geometry of the
pre-existing field, for instance, a canopy-like structure. Transverse fields
occurred before the observation of the strong Doppler shifts. The process is
most naturally explained as the emergence of a granular-scale loop that first
gives rise to the linear polarization signals, interacts with pre-existing
fields (generating new neutral line configurations), and produces the observed
strong flows. This explanation is indicative of frequent small-scale
reconnection events in the quiet Sun.Comment: 11 pages, 8 figure
Temporal evolution of the Evershed flow in sunspots. II. Physical properties and nature of Evershed clouds
Context: Evershed clouds (ECs) represent the most conspicuous variation of
the Evershed flow in sunspot penumbrae. Aims: We determine the physical
properties of ECs from high spatial and temporal resolution spectropolarimetric
measurements. Methods: The Stokes profiles of four visible and three infrared
spectral lines are subject to inversions based on simple one-component models
as well as more sophisticated realizations of penumbral flux tubes embedded in
a static ambient field (uncombed models). Results: According to the
one-component inversions, the EC phenomenon can be understood as a perturbation
of the magnetic and dynamic configuration of the penumbral filaments along
which these structures move. The uncombed inversions, on the other hand,
suggest that ECs are the result of enhancements in the visibility of penumbral
flux tubes. We conjecture that the enhancements are caused by a perturbation of
the thermodynamic properties of the tubes, rather than by changes in the vector
magnetic field. The feasibility of this mechanism is investigated performing
numerical experiments of thick penumbral tubes in mechanical equilibrium with a
background field. Conclusions: While the one-component inversions confirm many
of the properties indicated by a simple line parameter analysis (Paper I of
this series), we tend to give more credit to the results of the uncombed
inversions because they take into account, at least in an approximate manner,
the fine structure of the penumbra.Comment: Accepted for publication in A&
Runup and rundown generated by three-dimensional sliding masses
To study the waves and runup/rundown generated by a sliding mass, a numerical simulation model, based on the large-eddy-simulation (LES) approach, was developed. The Smagorinsky subgrid scale model was employed to provide turbulence dissipation and the volume of fluid (VOF) method was used to track the free surface and shoreline movements. A numerical algorithm for describing the motion of the sliding mass was also implemented.
To validate the numerical model, we conducted a set of large-scale experiments in a wave tank of 104m long, 3.7m wide and 4.6m deep with a plane slope (1:2) located at one end of the tank. A freely sliding wedge with two orientations and a hemisphere were used to represent landslides. Their initial positions ranged from totally aerial to fully submerged, and the slide mass was also varied over a wide range. The slides were instrumented to provide position and velocity time histories. The time-histories of water surface and the runup at a number of locations were measured.
Comparisons between the numerical results and experimental data are presented only for wedge shape slides. Very good agreement is shown for the time histories of runup and generated waves. The detailed three-dimensional complex flow patterns, free surface and shoreline deformations are further illustrated by the numerical results. The maximum runup heights are presented as a function of the initial elevation and the specific weight of the slide. The effects of the wave tank width on the maximum runup are also discussed
Models and Observations of Sunspot Penumbrae
The mysteries of sunspot penumbrae have been under an intense scrutiny for
the past 10 years. During this time, some models have been proposed and
refuted, while the surviving ones had to be modified, adapted and evolved to
explain the ever-increasing array of observational constraints. In this
contribution I will review two of the present models, emphasizing their
contributions to this field, but also pinpointing some of their inadequacies to
explain a number of recent observations at very high spatial resolution. To
help explaining these new observations I propose some modifications to each of
them. These modifications bring those two seemingly opposite models closer
together into a general picture that agrees well with recent 3D
magneto-hydrodynamic simulations.Comment: 9 pages, 1 color figure. Review talk to appear in the proceedings of
the International Workshop of 2008 Solar Total Eclipse: Solar Magnetism,
Corona and Space Weather--Chinese Space Solar Telescope Scienc
緑茶中のビタミンB12濃度に与えるアスコルビン酸の影響
急須を用いて乾燥茶葉から抽出された緑茶抽出液中のビタミンB_濃度は849±35pg/100ml,缶入りおよびペットボトル入り緑茶飲料5種の平均濃度は280±45pg/100mlであり,急須で入れた場合の方が3倍高い結果となった。ビタミンB_が後者で低かった理由として製造工程中にアスコルビン酸が添加されたためである可能性が考えられる。アスコルビン酸はビタミンB_と共存する場合にビタミンB_を分解することが既に報告されている。そこでアスコルビン酸を測定したところ,急須による緑茶抽出液5.87±0.66m/100ml,缶入りおよびペットボトル入り緑茶飲料5種の平均濃度は35.22±8.27mg/100mlであり,後者が前者の6倍の値であった。アスコルビン酸の添加によってビタミンB_濃度が影響を受けるのかを検討するために,急須を用いた抽出の際にアスコルビン酸を添加し,ビタミンB_濃度への影響を確認した。しかし,その影響は,緑茶抽出液のビタミンB_濃度の7%の減少に留まっていた(緑茶飲料では67%減少していた)。さらにアスコルビン酸添加後の加圧加熱(120℃)の影響も調べたが,影響は見られなかった。これらの結果から,極めて微量ながらも緑茶からビタミンB_が摂取できる可能性が示され,それは緑茶飲料より急須で乾燥茶葉から抽出した場合の方がより効率がよいことが示された。The vitamin B_ concentration in the green tea extract poured out from the teapot was measured to be 849±35 pg/100ml. The average concentration of 5 different green tea beverages from the markets was 280±45 pg/100ml. The lower content of vitamin B_ in the tea beverages may be due to the supplemented ascorbic acid added in the process of manufacture since the content of vitamin B_ in the solution was reported to decrease in coexistence with ascorbic acid. In fact the concentration of ascorbic acid in the tea beverages, 35.22±8.27mg/100ml in average, was six times higher than that of the poured tea, 5.87±0.66mg/100ml. Then we examined the effect of ascorbic acid added during the tea extraction on the vitamin B_ concentration. However, the addition of ascorbic acid at the same concentration of the tea beverages decreased only 7% of the vitamin B_ concentration in the poured tea compared to 67% decrease observed in the tea beverages. Moreover, the effect of heating at 120°C under pressure after the addition of ascorbic acid was examined and no difference was observed by heating. The result indicated that the green tea poured out from the teapot, though in a small quantity, was a better source for vitamin B_ than the tea beverages on markets
Against mass media trends: Minority growth in cultural globalization
We investigate the collective behavior of a globalized society under the influence of endogenous mass media trends. The mass media trend is a global field corresponding to the statistical mode of the states of the agents in the system. The interaction dynamics is based on Axelrod’s rules for the dissemination of culture. We find situations where the largest minority group, possessing a cultural state different from that of the predominant trend transmitted by the mass media, can grow to almost half of the size of the population. We show that this phenomenon occurs when a critical number of long-range connections are present in the underlying network of interactions. We have numerically characterized four phases on the space of parameters of the system: an ordered phase; a semi-ordered phase where almost half of the population consists of the largest minority in a state different from that of the mass media; a disordered phase; and a chimera-like phase where one large domain coexists with many very small domains
Comparative analysis on strains in asphalt pavement design using linear elastic and viscoelastic theories
In Colombia it is common to design pavements using the AASHTO 93 method and to complement it with an elastic analysis of the deformations that cause fatigue and rutting; this has repercussions on the behavior of the structure since it does not take into account the viscoelastic behavior of the asphalt mixtures, In this research, a comparison of three structures at different velocity ranges is made to compare the variation in fatigue and rutting concerning the traditional method of analysis in Colombia and to analyze the differences that may occur in linear elastic analysis and viscoelastic analysis of rutting and fatigue
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