Filter Results
113 results
Presentation in the frame of the Workshop Modern Solar Facilities - Advanced Solar Sience held in Göttingen from 27 - 29 September 2006. Fabry-Perot Interferometers (FPIs) have advantages over slit spectrographs, allowing fast two-dimensional, narrowband imaging and post factum image reconstruction of the spectropolarimetric data obtained. The resulting intensity, velocity and magnetic field maps are a fundamental base for the understanding of the dynamics of the solar atmosphere and its magnetic fields at smallest spatial scales. Efforts are undertaken to provide, with the Göttingen Fabry-Perot interferometer, an up-todate post-focus instrument for the German 1.5 m GREGOR solar telescope. Therefore a renewal of the spectrometer has been achieved during the first half of 2005. First observations at the German Vacuum Tower Telescope (VTT) reveal new scientific aspects and a very promising outlook for the future at GREGOR. In this contribution a general description of the upgraded spectrometer is given. Its final optical design at GREGOR is described and an optical analysis of the GREGOR FPI is outlined. Latest results with the new instrument obtained at the VTT are presented.
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• Video
The sequence shows the evolution of dynamic structures resembling tornadoes in the solar atmosphere. The red lines represent stream lines of the velocity field in the solar atmosphere. The contour shows the dynamic evolution of the $\beta=1$ layer.
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• Video
The Visible Tunable Filter (VTF) is a narrowband tunable filter system for imaging spectroscopy and spectropolarimetry based. The instrument will be one of the first-light instruments of the Daniel K. Inouye Solar Telescope that is currently under construction on Maui (Hawaii). The VTF is being developed by the Kiepenheuer Institut fuer Sonnenphysik in Freiburg as a German contribution to the DKIST. We perform end-to-end simulations of spectropolarimetric observations with the VTF to verify the science requirements of the instrument. The instrument is simulated with two Etalons, and with a single Etalon. The clear aperture of the Etalons is 250 mm, corresponding to a field of view with a diameter of 60 arcsec in the sky (42,000 km on the Sun). To model the large-scale figure errors we employ low-order Zernike polynomials (power and spherical aberration) with amplitudes of 2.5 nm RMS. We use an ideal polarization modulator with equal modulation coefficients of 3-1/2 for the polarization modulation We synthesize Stokes profiles of two iron lines (630.15 nm and 630.25 nm) and for the 854.2 nm line of calcium, for a range of magnetic field values and for several inclination angles. We estimated the photon noise on the basis of the DKIST and VTF transmission values, the atmospheric transmission and the spectral flux from the Sun. For the Fe 630.25 nm line, we obtain a sensitivity of 20 G for the longitudinal component and for 150 G for the transverse component, in agreement with the science requirements for the VTF.
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• Video
Biofield therapies have been reported to improve the quality of life as compared to other energy medicine. The aim of the study was to evaluate the impact of Mr. Trivedi’s biofield energy treatment on Pseudomonas fluorescens (P. fluorescens) for antimicrobial sensitivity, minimum inhibitory concentration (MIC), biochemical reactions, and biotype number. P. fluorescens cells were procured from MicroBioLogics Inc., USA in sealed packs bearing the American Type Culture Collection (ATCC 49838) number and divided in control and treated group. The effect was evaluated on day 10, and 159 after biofield treatment in lyophilized state. Further study was performed on day 5, 10, and 15 after retreatment on day 159 in revived state as per study design. All experimental parameters were studied using automated MicroScan Walk-Away® system. The 16S rDNA sequencing was carried out to correlate the phylogenetic relationship of P. fluorescens with other bacterial species after treatment. The results showed improved sensitivities and decreased MIC value of aztreonam, cefepime, moxifloxacin, and tetracycline in revived and lyophilized treated sample with respect to the control. Arginine, cetrimide, kanamycin, and glucose showed altered biochemical reactions after biofield treatment with respect to control. Biotype numbers were altered along with species in lyophilized as well as in revived group. Based on nucleotides homology and phylogenetic analysis using 16S rDNA gene sequencing, treated sample was detected to be Pseudomonas entomophila (GenBank Accession Number: AY907566) with 96% identity of gene sequencing data, which was nearest homolog species to P. fluorescens (Accession No. EF672049). These findings suggest that Mr. Trivedi’s unique biofield treatment has the capability to alter changes in pathogenic P. fluorescens even in the lyophilized storage condition and can be used to modify the sensitivity of microbes against antimicrobials.
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• Video
Several mechanisms may heat the solar chromosphere: acoustic waves, magnetoacoustic waves (slow, fast, and Alfven waves), and small-scale magnetic reconnections. Based on observations in the Ca II 854.2 nm line, the contribution of acoustic waves to the heating of quiet and plage regions in the chromosphere is discussed. The point is to compare the energy released by radiative losses with the energy deposited by acoustic waves. Radiative losses are computed using a grid of semi-empirical chromospheric models. The deposited acoustic flux is calculated using power spectra of Doppler oscillations measured in the Ca II line core. The comparison shows that the spatial correlation of maps of radiative losses and acoustic flux is 72 %. The deposited acoustic flux covers only 15 % of radiative losses in quiet chromosphere but 23 % in network and 54 % in plage areas. This estimate is a lower limit of the real acoustic energy flux.
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• Video
The collaborative project "SpaceInn - Exploitation of Space Data for Innovative Helio- and Asteroseismolgy" is funded under the European Union’s Seventh Framework Programme from January 2013 – December 2016. The European Helio- and Asteroseismology Network (HELAS) has initiated this project with the mission to build on the existing European strength in the field of time-domain stellar physics. In the last three years SpaceInn activities aimed to secure optimal use of the existing and planned data, from space and from the ground, in helio- and asteroseismology in order to improve access and scientific exploitation of the existing data. The main goals of the project include: -Establish coordinated archives of space- and ground-based data, as well as of the results of the analyses of these data. This includes tools for efficient data access. -Secured long-term preservation of these, often unique, data. -Coordinated utilization of the data, resulting in a much improved understanding of solar structure, dynamics and activity, as well as of stellar structure and evolution -An increased awareness of the field, amongst the general public and at all levels of the educational system, throughout Europe. In this talk I will present all these activities and the main outcome of the project.
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• Video
The differences between the oscillation frequencies and uncertainty estimates of a star derived by different fitters can be large, sufficiently large so that, were one to find a stellar model that fitted one frequency set ($\chi^2\sim 1$), it does not fit an alternative set. I give 21 examples, comparing frequency sets in common between the Kepler Legacy project and frequency sets from Appourchaux et al (2014) and Davies et al (2015). For 16CygA\andB the differences are large; the $\chi^2$ of the fit of Legacy to Davies's values ranging from 1.64 to 11.47 for 16CygA and 1.62 to 1.79 for 16CygB, depending on which error estimates are used. I analyse both stars in some detail applying my own mode fitting code to both the Legacy and Davies's power spectra and find reasonable agreement with Davies's full frequency sets and very good agreement between values for modes with signal/noise > 1 ($\chi^2 = 0.06, \chi^2_B=0.03$). But the difference with the Legacy values remains large even for modes with S/N>1. I also examine the effects of different power spectra (weighted and unweighted) using the kasoc light curves for Q6-17.2 and Q7-Q16, the effect of different mode height ratios and different rotational splitting and inclination.
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• Video
The HELioseismic Large Regions Interferometric Device (HELLRIDE) installed at the Vacuum Tower Telescope (VTT) in Izana, Tenerife has entered scientific mode in 2015. The instrument is a tunable filter that allows scanning sequentially through up to 32 spectral lines within short times delivering two-dimensional filtergrams of the Sun. In this talk I will summarize the capabilities of the instrument and present first results obtained during the 2015 observing campaigns.
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• Video
The long-time photometric surveys in a few young open clusters allowed to identify the light variability in stars located between the well defined  Scuti variables and Slowly Pulsating B-type stars (Mowlavi et al, 2013, 2015). The period of these changes is in the range of about 0.1 - 0.7 [d] corresponding to the frequencies of about 1.4 - 10 [d-1]. Several objects of this type were suggested also from the analysis of the Kepler data (Balona et al. 2015a). Assuming the pulsational origin of this variability, we test a few hypotheses. Because all these open clusters are very young, we consider only the ZAMS models with the metallicity Z=0.015.
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• Video
Increase in the Balmer continuum radiation during solar flares was predicted by various authors, but has never been firmly confirmed observationally using ground-based slit spectrographs. We developed a new post-focal instrument, the image selector, with which the Balmer continuum flux can be measured from the whole flare area, in analogy to successful detections of flaring dMe stars. The system was put into operation at the horizontal solar telescope HSFA2 of the Ondřejov Observatory. We measure the total flux by a fast spectrometer from a limited but well-defined region on the solar disk. Using a system of diaphragms, the disturbing contribution of a bright solar disk can be eliminated as much as possible. Light curves of the measured flux in the spectral range 350 - 440 nm are processed, together with the Hα images of the flaring area delimited by the appropriate diaphragm. The spectral flux data are flat-fielded, calibrated, and processed to be compared with model predictions. Our analysis of the data proves that the described device is sufficiently sensitive to detect variations in the Balmer continuum during solar flares. Assuming that the Balmer-continuum kernels have at least a similar size as those visible in Hα, we find the flux increase in the Balmer continuum to reach 230 - 550 % of the quiet continuum during the observed X-class flare. We also found temporal changes in the Balmer continuum flux starting well before the onset of the flare in Hα.
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• Video
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