Morphological Properties of Slender Ca ${\rm{II}}$ H Fibrils Observed by Sunrise II

Gafeira, R.,Lagg, A.,Solanki, S. K.,Jafarzadeh, S.,Noort, M. van,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1

<P>We use seeing-free high spatial resolution Ca II H data obtained by the SUNRISE observatory to determine properties of slender fibrils in the lower solar chromosphere. In this work we use intensity images taken with the SUFI instrument in the Ca II H line during the second scientific flight of the SUNRISE observatory to identify and track elongated bright structures. After identification, we analyze theses structures to extract their morphological properties. We identify 598 slender Ca II H fibrils (SCFs) with an average width of around 180 km, length between 500 and 4000 km, average lifetime of approximate to 400 s, and average curvature of 0.002 arcsec(-1). The maximum lifetime of the SCFs within our time series of 57 minutes is approximate to 2000 s. We discuss similarities and differences of the SCFs with other small-scale, chromospheric structures such as spicules of type I and II, or Ca II K fibrils.</P>

THE FORMATION AND DISINTEGRATION OF MAGNETIC BRIGHT POINTS OBSERVED BY<i>SUNRISE</i>/IMaX

Utz, D.,del Toro Iniesta, J. C.,Bellot Rubio, L. R.,Jurč,á,k, J.,Martí,nez Pillet, V.,Solanki, S. K.,Schmidt, W. IOP Publishing 2014 The Astrophysical journal Vol.796 No.2

<P>The evolution of the physical parameters of magnetic bright points (MBPs) located in the quiet Sun (mainly in the interwork) during their lifetime is studied. First, we concentrate on the detailed description of the magnetic field evolution of three MBPs. This reveals that individual features follow different, generally complex, and rather dynamic scenarios of evolution. Next, we apply statistical methods on roughly 200 observed MBP evolutionary tracks. MBPs are found to be formed by the strengthening of an equipartition field patch, which initially exhibits a moderate downflow. During the evolution, strong downdrafts with an average velocity of 2.4 km s(-1) set in. These flows, taken together with the concurrent strengthening of the field, suggest that we are witnessing the occurrence of convective collapses in these features, although only 30% of them reach kG field strengths. This fraction might turn out to be larger when the new 4mclass solar telescopes are operational as observations of MBPs with current state of the art instrumentation could still be suffering from resolution limitations. Finally, when the bright point disappears (although the magnetic field often continues to exist) the magnetic field strength has dropped to the equipartition level and is generally somewhat weaker than at the beginning of the MBP's evolution. Also, only relatively weak downflows are found on average at this stage of the evolution. Only 16% of the features display upflows at the time that the field weakens, or the MBP disappears. This speaks either for a very fast evolving dynamic process at the end of the lifetime, which could not be temporally resolved, or against strong upflows as the cause of the weakening of the field of these magnetic elements, as has been proposed based on simulation results. It is noteworthy that in about 10% of the cases, we observe in the vicinity of the downflows small-scale strong (exceeding 2 km s-1) intergranular upflows related spatially and temporally to these downflows. The paper is complemented by a detailed discussion of aspects regarding the applied methods, the complementary literature, and in depth analysis of parameters like magnetic field strength and velocity distributions. An important difference to magnetic elements and associated bright structures in active region plage is that most of the quiet Sun bright points display significant downflows over a large fraction of their lifetime (i.e., in more than 46% of time instances/measurements they show downflows exceeding 1 km s(-1)).</P>

SILICON QUANTUM DOTS GROWTH IN SiNx DIELECTRIC: A REVIEW

A. K. PANCHAL,D. K. RAI,M. MATHEW,C. S. SOLANKI 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2009 NANO Vol.4 No.5

This paper reviews research works carried out on silicon quantum dots (Si-QDs) embedded in the silicon nitride (SiNx) dielectric matrix films with different fabrication techniques and different characteristics. The advantages of SiNx as a dielectric compared to silicon dioxide (SiO2) for Si-QDs from a device point of view are discussed. Various fabrication techniques along with different optimized deposition conditions are summarized. The typical results of structural characteristics of the films with Raman spectroscopy and Transmission Electron Microscopy (TEM) are discussed. The origin of photoluminescence (PL) from the films and the chemical compositional analysis such as X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR) and Secondary Ion Mass Spectroscopy (SIMS) analysis of the films are also made available in brief. The charge conduction mechanism in the films with metal–insulator–semiconductor (MIS) structure, with their electrical characterization like capacitance–voltage (C–V) and current–voltage (I–V) measurements are presented.

SUNRISE: INSTRUMENT, MISSION, DATA, AND FIRST RESULTS

Solanki, S. K.,Barthol, P.,Danilovic, S.,Feller, A.,Gandorfer, A.,Hirzberger, J.,Riethmü,ller, T. L.,Schü,ssler, M.,Bonet, J. A.,Pillet, V. Martí,nez,del Toro Iniesta, J. C.,Domingo, V. IOP Publishing 2010 ASTROPHYSICAL JOURNAL LETTERS - Vol.723 No.2

Kinematics of Magnetic Bright Features in the Solar Photosphere

Jafarzadeh, S.,Solanki, S. K.,Cameron, R. H.,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Pillet, V. Martí,nez,Su&aacut American Astronomical Society 2017 The Astrophysical journal Supplement series Vol.229 No.1

<P>Convective flows are known as the prime means of transporting magnetic fields on the solar surface. Thus, small magnetic structures are good tracers of turbulent flows. We study the migration and dispersal of magnetic bright features (MBFs) in intergranular areas observed at high spatial resolution with SUNRISE/IMaX. We describe the flux dispersal of individual MBFs as a diffusion process whose parameters are computed for various areas in the quiet-Sun and the vicinity of active regions from seeing-free data. We find that magnetic concentrations are best described as random walkers close to network areas (diffusion index, gamma = 1.0), travelers with constant speeds over a supergranule (gamma = 1.9-2.0), and decelerating movers in the vicinity of flux emergence and/or within active regions (gamma = 1.4-1.5). The three types of regions host MBFs with mean diffusion coefficients of 130 km(2) s(-1), 80-90 km(2) s(-1), and 25-70 km(2) s(-1), respectively. The MBFs in these three types of regions are found to display a distinct kinematic behavior at a confidence level in excess of 95%.</P>

Transverse Oscillations in Slender Ca ii H Fibrils Observed with Sunrise/SuFI

Jafarzadeh, S.,Solanki, S. K.,Gafeira, R.,Noort, M. van,Barthol, P.,Rodrí,guez, J. Blanco,Iniesta, J. C. del Toro,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, D. Orozco American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1

<P>We present observations of transverse oscillations in slender Ca II H fibrils (SCFs) in the lower solar chromosphere. We use a 1 hr long time series of high- (spatial and temporal-) resolution. seeing-free observations in a 1.1 angstrom wide passband covering the line core of Ca II H 3969 angstrom from the second flight of the SUNRISE balloon-borne solar observatory. The entire field of view, spanning the polarity inversion line of an active region close to the solar disk center, is covered with bright, thin, and very dynamic fine structures. Our analysis reveals the prevalence of transverse waves in SCFs with median amplitudes and periods on the order of 2.4 +/- 0.8 km s(-1) and 83 +/- 29 s, respectively (with standard deviations given as uncertainties). We find that the transverse waves often propagate along (parts of) the SCFs with median phase speeds of 9 +/- 14 km s(-1). While the propagation is only in one direction along the axis in some of the SCFs, propagating waves in both directions, as well as standing waves are also observed. The transverse oscillations are likely Alfvenic and are thought to be representative of magnetohydrodynamic kink waves. The wave propagation suggests that the rapid. high-frequency transverse waves,. often produced in the lower photosphere, can penetrate into the chromosphere. with an estimated energy flux of approximate to 15 kW m(-2). Characteristics of these waves differ from those reported for other fibrillar structures, which, however, were observed mainly in the upper solar chromosphere.</P>

Solar activity over nine millennia: A consistent multi-proxy reconstruction

Wu, C. J.,Usoskin, I. G.,Krivova, N.,Kovaltsov, G. A.,Baroni, M.,Bard, E.,Solanki, S. K. Springer-Verlag 2018 Astronomy and astrophysics Vol.615 No.-

<P><I>Aims.</I> The solar activity in the past millennia can only be reconstructed from cosmogenic radionuclide proxy records in terrestrial archives. However, because of the diversity of the proxy archives, it is difficult to build a homogeneous reconstruction. All previous studies were based on individual, sometimes statistically averaged, proxy datasets. Here we aim to provide a new consistent multi-proxy reconstruction of the solar activity over the last 9000 yr, using all available long-span datasets of <SUP>10</SUP>Be and <SUP>14</SUP>C in terrestrial archives.</P><P><I>Methods.</I> A new method, based on a Bayesian approach, was applied for the first time to solar activity reconstruction. A Monte Carlo search (using the <I>χ</I><SUP>2</SUP> statistic) for the most probable value of the modulation potential was performed to match data from different datasets for a given time. This provides a straightforward estimate of the related uncertainties. We used six <SUP>10</SUP>Be series of different lengths (from 500-10 000 yr) from Greenland and Antarctica, and the global <SUP>14</SUP>C production series. The <SUP>10</SUP>Be series were resampled to match wiggles related to the grand minima in the <SUP>14</SUP>C reference dataset. The stability of the long data series was tested.</P><P><I>Results.</I> The Greenland Ice-core Project (GRIP) and the Antarctic EDML (EPICA Dronning Maud Land) <SUP>10</SUP>Be series diverge from each other during the second half of the Holocene, while the <SUP>14</SUP>C series lies in between them. A likely reason for the discrepancy is the insufficiently precise beryllium transport and deposition model for Greenland, which leads to an undercorrection of the GRIP series for the geomagnetic shielding effect. A slow 6-7 millennia variability with lows at ca. 5500 BC and 1500 AD in the long-term evolution of solar activity is found. Two components of solar activity can be statistically distinguished: the main component, corresponding to the “normal” moderate level, and a component corresponding to grand minima. A possible existence of a component representing grand maxima is indicated, but it cannot be separated from the main component in a statistically significant manner.</P><P><I>Conclusions.</I> A new consistent reconstruction of solar activity over the last nine millennia is presented with the most probable values of decadal sunspot numbers and their realistic uncertainties. Independent components of solar activity corresponding to the main moderate activity and the grand-minimum state are identified; they may be related to different operation modes of the dynamo.</P>

Solar total and spectral irradiance reconstruction over the last 9000 years

Wu, C.-J.,Krivova, N. A.,Solanki, S. K.,Usoskin, I. G. Springer-Verlag 2018 Astronomy and astrophysics Vol.620 No.-

<P><I>Context.</I> Changes in solar irradiance and in its spectral distribution are among the main natural drivers of the climate on Earth. However, irradiance measurements are only available for less than four decades, while assessment of solar influence on Earth requires much longer records.</P><P><I>Aims.</I> The aim of this work is to provide the most up-to-date physics-based reconstruction of the solar total and spectral irradiance (TSI/SSI) over the last nine millennia.</P><P><I>Methods.</I> The concentrations of the cosmogenic isotopes <SUP>14</SUP>C and <SUP>10</SUP>Be in natural archives have been converted to decadally averaged sunspot numbers through a chain of physics-based models. TSI and SSI are reconstructed with an updated SATIRE model. Reconstructions are carried out for each isotope record separately, as well as for their composite.</P><P><I>Results.</I> We present the first ever SSI reconstruction over the last 9000 years from the individual <SUP>14</SUP>C and <SUP>10</SUP>Be records as well as from their newest composite. The reconstruction employs physics-based models to describe the involved processes at each step of the procedure.</P><P><I>Conclusions.</I> Irradiance reconstructions based on two different cosmogenic isotope records, those of <SUP>14</SUP>C and <SUP>10</SUP>Be, agree well with each other in their long-term trends despite their different geochemical paths in the atmosphere of Earth. Over the last 9000 years, the reconstructed secular variability in TSI is of the order of 0.11%, or 1.5 W m<SUP>−2</SUP>. After the Maunder minimum, the reconstruction from the cosmogenic isotopes is consistent with that from the direct sunspot number observation. Furthermore, over the nineteenth century, the agreement of irradiance reconstructions using isotope records with the reconstruction from the sunspot number by Chatzistergos et al. (2017, A&A, 602, A69) is better than that with the reconstruction from the WDC-SILSO series (Clette et al. 2014, Space Sci. Rev., 186, 35), with a lower <I>χ</I><SUP>2</SUP>-value.</P>

Oscillations on Width and Intensity of Slender Ca ii H Fibrils from Sunrise/SuFI

Gafeira, R.,Jafarzadeh, S.,Solanki, S. K.,Lagg, A.,van Noort, M.,Barthol, P.,Rodrí,guez, J. Blanco,del Toro Iniesta, J. C.,Gandorfer, A.,Gizon, L.,Hirzberger, J.,Knö,lker, M.,Suá,rez, American Astronomical Society 2017 The Astrophysical journal, Supplement series Vol.229 No.1

<P>We report the detection of oscillations in slender Ca II H fibrils (SCFs) from high-resolution observations acquired with the SUNRISE balloon-borne solar observatory. The SCFs show obvious oscillations in their intensity, but also their width. The oscillatory behaviors are investigated at several positions along the axes of the SCFs. A large majority of fibrils show signs of oscillations in intensity. Their periods and phase speeds are analyzed using a wavelet analysis. The width and intensity perturbations have overlapping distributions of the wave period. The obtained distributions have median values of the period of 32 +/- 17 s and 36 +/- 25 s, respectively. We find that the fluctuations of both parameters propagate in the SCFs with speeds of 11(-11)(+49)+ km s(-1) and 15(-15)(+34) km s(-1), respectively. Furthermore, the width and intensity oscillations have a strong tendency to be either in anti-phase. or, to a smaller extent, in phase. This suggests that the oscillations of both parameters are caused by the same wave mode and that the waves are likely propagating. Taking all the evidence together, the most likely wave mode to explain all measurements and criteria is the fast sausage mode.</P>

Recent variability of the solar spectral irradiance and its impact on climate modelling

Ermolli, I.,Matthes, K.,Dudok de Wit, T.,Krivova, N. A.,Tourpali, K.,Weber, M.,Unruh, Y. C.,Gray, L.,Langematz, U.,Pilewskie, P.,Rozanov, E.,Schmutz, W.,Shapiro, A.,Solanki, S. K.,Woods, T. N. Copernicus GmbH 2013 Atmospheric chemistry and physics Vol.13 No.8

<P>Abstract. The lack of long and reliable time series of solar spectral irradiance (SSI) measurements makes an accurate quantification of solar contributions to recent climate change difficult. Whereas earlier SSI observations and models provided a qualitatively consistent picture of the SSI variability, recent measurements by the SORCE (SOlar Radiation and Climate Experiment) satellite suggest a significantly stronger variability in the ultraviolet (UV) spectral range and changes in the visible and near-infrared (NIR) bands in anti-phase with the solar cycle. A number of recent chemistry-climate model (CCM) simulations have shown that this might have significant implications on the Earth's atmosphere. Motivated by these results, we summarize here our current knowledge of SSI variability and its impact on Earth's climate. We present a detailed overview of existing SSI measurements and provide thorough comparison of models available to date. SSI changes influence the Earth's atmosphere, both directly, through changes in shortwave (SW) heating and therefore, temperature and ozone distributions in the stratosphere, and indirectly, through dynamical feedbacks. We investigate these direct and indirect effects using several state-of-the art CCM simulations forced with measured and modelled SSI changes. A unique asset of this study is the use of a common comprehensive approach for an issue that is usually addressed separately by different communities. We show that the SORCE measurements are difficult to reconcile with earlier observations and with SSI models. Of the five SSI models discussed here, specifically NRLSSI (Naval Research Laboratory Solar Spectral Irradiance), SATIRE-S (Spectral And Total Irradiance REconstructions for the Satellite era), COSI (COde for Solar Irradiance), SRPM (Solar Radiation Physical Modelling), and OAR (Osservatorio Astronomico di Roma), only one shows a behaviour of the UV and visible irradiance qualitatively resembling that of the recent SORCE measurements. However, the integral of the SSI computed with this model over the entire spectral range does not reproduce the measured cyclical changes of the total solar irradiance, which is an essential requisite for realistic evaluations of solar effects on the Earth's climate in CCMs. We show that within the range provided by the recent SSI observations and semi-empirical models discussed here, the NRLSSI model and SORCE observations represent the lower and upper limits in the magnitude of the SSI solar cycle variation. The results of the CCM simulations, forced with the SSI solar cycle variations estimated from the NRLSSI model and from SORCE measurements, show that the direct solar response in the stratosphere is larger for the SORCE than for the NRLSSI data. Correspondingly, larger UV forcing also leads to a larger surface response. Finally, we discuss the reliability of the available data and we propose additional coordinated work, first to build composite SSI data sets out of scattered observations and to refine current SSI models, and second, to run coordinated CCM experiments. </P>