1,720,965 research outputs found
Statistical Properties of Synthetic Nanoflares
No full textStatistical properties of flares are a powerful tool for addressing the upper solar atmosphere heating problem.We
simulate time series of synthetic flares by means of a dynamic model of the atmospheric magnetic field in which
magnetic loop footpoints are controlled by photospheric flows computed through a n-body algorithm. The n-body
simulation reproduces the behavior of a system where large spatial organization scales (i.e., mesogranulation) occur
from the interaction of small-scale advection flows (i.e., granulation). The frequency function of the emitted magnetic
energies obtained from the simulation is well approximated by a power law with index 2:4, while the frequency
function of the waiting times between emissions shows a Poisson-like behavior with a deviation for longer times. The
flare model yields a fairly intuitive interpretation ofmagnetic reconnection processes as magnetic field reconfigurations
triggered by passive advection of magnetic footpoints through photospheric space-temporal correlated flows
The Void Probability Distribution Observed in High-Resolution Hinode/SOT and SDO Magnetograms
No full textA new searching algorithm to find voids in high resolution magnetograms is described. This algorithm permits the investigation of spatially intermittent nature of magnetic field emerging when solar surface is observed at high spatial resolution. Actually, at these small scales, the connected patterns, forming magnetic network, show aligned or clustered magnetic features producing a highly branched and fractal pattern embodying magnetic elements. High resolution Hinode/SOT and SDO magnetograms confirmed the presence of multiscale underdense (voids) magnetic regions. Preliminary Void Probability Distribution (VPD), measured in such high-resolution magnetograms, are presented and briefly discussed
MISMA Interpretation of Stokes V Asymmetries Measured by HINODE in Internetwork and Network Regions
No full textIBIS 2D Spectropolarimetry: Analysis of G-band Bright Points
No full textWe present the results derived from the analysis of the first spectropolarimetric (SP) data obtained through the Interferometric BIdimensional Spectrometer (IBIS) at the Dunn Solar Telescope (NSO). The analysis is focused on 103 G small scale ( ̃100 km) magnetic field concentrations observed, in a quiet Sun region, as bright points in G-band filtergrams. The combination of high spatial and temporal resolution of both SP and G-band datasets allowed us to analyze in detail the magnetic properties of bright points over different spatial scales (from ̃eq. 0.4" up to 2"- 3") and temporal scales (from 10 min up to > 60 min) and, beside this, to focus on the dependence of significant physical quantities (i.e., magnetic field strength and filling factor derived from Stokes profile inversion) in relation with such evolutions.
We present two main results of our analysis: i) evolution of bright points over small spatial scales and short time intervals (by considering the coalescence of small and faint bright points into a single high brightness one); ii) magnetic properties of bright points over large spatial scales (by examining a small network patch). Our study indicates an interesting correlation between G-band brightness and magnetic filling factor fluctuations. On the contrary, we have not observed any correlation between G-band brightness and magnetic field strength. Such a result can help us to conclude on the possible fine structuring of kG concentrations in the solar photosphere which produce brightness enhancement in G-band filtergrams
The photospheric structure of a solar pore with light bridge
Full text linkContext. Pores are among the photospheric features that form when the magnetic field emerges onto the solar surface. In pores or sunspots, light bridges are bright features that separate umbral areas into two or more irregular regions. Aims. We study the structure of a solar pore (AR10812) with a light bridge. Methods. We analyzed both broad-band and narrow-band images acquired with the Interferometric BI-dimensional Spectrometer at the adaptive optics channel of the NSO/Dunn Solar Telescope. Narrow-band images acquired in the photospheric Fe I 709.04 nm line were used to determine the line-of-sight velocity field. Results. The roundish shape of the pore allows us to derive the radial profiles of both intensity and vertical velocity. The pore has a downward velocity, of about -200 m s, and is surrounded by an annular downflow structure with an average velocity of about -300 m s with respect to the nearby quiet sun. The light bridge shows a long narrow dark structure running along its axis. Corresponding to this dark lane, we measure a weak upflow of about 70 m s, flanked by a downflow of about 150 m s with respect to the pore. The topology of this velocity structure resembles a convective roll. The anticorrelation between continuum intensity and photospheric velocity may be due to the higher gas pressure in a photospheric field-free cusp, above the light bridge, located between two magnetic walls. We present an analytical model capable of reproducing the observations
Imaging Spectropolarimetry with IBIS: Evolution of Bright Points in the Quiet Sun
Full text linkWe present the results from first spectropolarimetric observations of the solar photosphere acquired at the Dunn Solar Telescope with the Interferometric Bidimensional Spectrometer. Full Stokes profiles were measured in the Fe I 630.15 nm and Fe I 630.25 nm lines with high spatial and spectral resolutions for 53 minutes, with a Stokes V noise of 3 × 10-3 the continuum intensity level. The data set allows us to study the evolution of several magnetic features associated with G-band bright points (BPs) in the quiet Sun. Here we focus on the analysis of three distinct processes, namely the coalescence, fragmentation, and cancellation of G-band BPs. Our analysis is based on an SIR inversion of the Stokes I and V profiles of both Fe I lines. The high spatial resolution of the G-band images combined with the inversion results helps to interpret the undergoing physical processes. The appearance (dissolution) of high-contrast G-band BPs is found to be related to the local increase (decrease) of the magnetic filling factor, without appreciable changes in the field strength. The cancellation of opposite-polarity BPs can be the signature of either magnetic reconnection or the emergence/submergence of magnetic loops
Magnetic Bright Points in the Quiet Sun
Full text linkWe present a visual determination of the number of bright points (BPs) existing in the quiet Sun, which are structures though to trace intense kG magnetic concentrations. The measurement is based on a 0″.1 angular resolution G-band movie obtained with the Swedish Solar Telescope at the solar disk center. We find 0.97 BPs Mm-2, which is a factor 3 larger than any previous estimate. It corresponds to 1.2 BPs per solar granule. Depending on the details of the segmentation, the BPs cover between 0.9% and 2.2% of the solar surface. Assuming their field strength to be 1.5 kG, the detected BPs contribute to the solar magnetic flux with an unsigned flux density between 13 G and 33 G. If network and inter-network regions are counted separately, they contain 2.2 BPs Mm-2 and 0.85 BPs Mm-2, respectively
Interpretation of HINODE SOT/SP asymmetric Stokes profiles observed in the quiet Sun network and internetwork
No full textStokes profiles emerging from the magnetized solar photosphere and observed by SOT/SP aboard the HINODE satellite exhibit a variety of complex shapes. These are indicative of unresolved magnetic structures that have been overlooked in the inversion analyses performed so far. Here we present the first interpretation of the Stokes profile asymmetries measured in the Fe
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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