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Filtering by: Creator Mathioudakis, Mihalis Remove constraint Creator: Mathioudakis, Mihalis

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  • T722hd33d?file=thumbnail
    Article
    Mathioudakis, Mihalis
    The Rapid Oscillations in the Solar Atmosphere instrument reveals solar atmospheric fluctuations at high frequencies. Spectra of variations of the G-band intensity (IG ) and Ca IIK-line intensity (IK ) show correlated fluctuations above white noise to . . .
  • Work
    Conference paper or proceedings
    Mathioudakis, Mihalis
    We study properties of intensity fluctuations in NOAA Active Region 11250 observed on 13 July 2011 starting at UT 13:32. Included are data obtained in the EUV bands of the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO/AIA) . . .
  • 2514nq43g?file=thumbnail
    Article
    Antolin, Patrick
    We present observational evidence of compressible MHD wave modes propagating from the solar photosphere through to the base of the transition region in a solar magnetic pore. High cadence images were obtained simultaneously across four wavelength band . . .
  • Q524js434?file=thumbnail
    Article
    Keenan, Francis P.
    The Rapid Oscillations in the Solar Atmosphere (ROSA) instrument is a synchronized, six-camera high-cadence solar imaging instrument developed by Queen's University Belfast. The system is available on the Dunn Solar Telescope at the National Solar Obs . . .
  • 0c483n81x?file=thumbnail
    Article
    Keys, Peter H.
    We use images of high spatial and temporal resolution, obtained with the Rapid Oscillations in the Solar Atmosphere instrument at the Dunn Solar Telescope, to reveal how the generation of transverse waves in Type I spicules is a direct result of longi . . .
  • 3n2042673?file=thumbnail
    Article
    Vennes, Stephane
    We report the detection of a new late-type spectroscopic binary, EUVE J224415.9 (HD 215341) using the 0.6 meter Coude auxiliary telescope and Hamilton echelle spectrograph at Lick observatory.
  • 8336h537w?file=thumbnail
    Article
    Keenan, Francis P.
    Magnetic bright points (MBPs) are among the smallest observable objects on the solar photosphere. A combination of G-band observations and numerical simulations is used to determine their area distribution. An automatic detection algorithm, employing . . .
  • W6634701r?file=thumbnail
    Article
    Mullan, D.J.
    Dynamo activity in stars of different types is expected to generate magnetic fields with different characteristics. As a result, a differential study of the characteristics of magnetic loops in a broad sample of stars may yield information about dynam . . .
  • 6d570075k?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We present observations of a strong flare from EUVE J0613-23.9B, a source serendipitously detected with the EUVE Deep Survey Telescope 2.5' south of HD 43162. Optical spectroscopy revealed EUVE J0613-23.9B to be an active dM3.5e star. A dM4e star was . . .
  • Bg257j673?file=thumbnail
    Article
    Keenan, Francis P.
    High-cadence, multiwavelength observations and simulations are employed for the analysis of solar photospheric magnetic bright points (MBPs) in the quiet Sun. The observations were obtained with the Rapid Oscillations in the Solar Atmosphere (ROSA) im . . .
  • 70795b94d?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We investigate if the super-saturation phenomenon observed at X-ray wavelengths for the corona exists in the chromosphere for rapidly rotating late-type stars. Moderate resolution optical spectra of fast-rotating EUV- and X-ray-selected late-type star . . .
  • 8w32r870s?file=thumbnail
    Article
    De Moortel, I.
    We use images of high spatial, spectral, and temporal resolution, obtained using both ground- and space-based instrumentation, to investigate the coupling between wave phenomena observed at numerous heights in the solar atmosphere. Analysis of 4170 � . . .
  • 2b88qg50d?file=thumbnail
    Article
    Milligan, R.O.
    The Extreme Ultraviolet Variability Experiment (EVE) on the Solar Dynamics Observatory obtains extreme-ultraviolet (EUV) spectra of the full-disc Sun at a spectral resolution of ~1 Å and cadence of 10 s. Such a spectral resolution would normally be co . . .
  • Work
    Conference paper or proceedings
    Lawrence, John K.
    Using the Rapid Oscillation in the Solar Atmosphere (ROSA) instrument at the Dunn Solar Telescope we have found that the spectra of fluctuations of the G-band (cadence 1.05 s) and Ca ii K-line (cadence 4.2 s) intensities show correlated fluctuations a . . .
  • N009w575g?file=thumbnail
    Article
    Mackay, S.
    Sunspots on the surface of the Sun are the observational signatures of intense manifestations of tightly packed magnetic field lines, with near-vertical field strengths exceeding 6,000 G in extreme cases1. It is well accepted that both the plasma dens . . .
  • Z029p818z?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We present far ultraviolet and optical spectroscopy of the Extreme Ultraviolet Explorer (EUVE) survey source EUVE J0702+129 revealing a composite K0 star plus DA white dwarf spectrum. The International Ultraviolet Explorer spectra show continuum emiss . . .
  • Nv9355980?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We present high-resolution optical spectra of EUV-selected late-type stars. We have detected seven new spectroscopic binaries, including a pair of F stars and an RS Canum Venaticorum candidate. Many of the stars in our sample show remarkable H? emissi . . .
  • 0p096990p?file=thumbnail
    Article
    Hauschildt, P.H.
    We present high-resolution VLT UVES observations of the active K dwarf GJ 117. 6Li enhancement has been shown for energetic solar events, one chromospherically active binary, and several dwarf halo stars. Our analysis reveals the detection of 6Li on t . . .
  • Rv042x37m?file=thumbnail
    Article
    Keenan, Francis P.
    Using data obtained by the high temporal and spatial resolution Rapid Oscillations in the Solar Atmosphere instrument on the Dunn Solar Telescope, we investigate at an unprecedented level of detail transverse oscillations in chromospheric fine structu . . .
  • 70795b74x?file=thumbnail
    Article
    Keenan, Francis P.
    High-cadence, multiwavelength, optical observations of solar magnetic bright points (MBPs), captured at the disk center using the ROSA and IBIS imaging systems on the Dunn Solar Telescope, are presented. MBPs manifesting in the Na i D1 core are found . . .
  • 1v53k1188?file=thumbnail
    Article
    Keenan, Francis P.
    We present high-cadence observations and simulations of the solar photosphere, obtained using the Rapid Oscillations in the Solar Atmosphere imaging system and the MuRAM magnetohydrodynamic (MHD) code, respectively. Each data set demonstrates a wealth . . .
  • Qf85nf30t?file=thumbnail
    Article
    Keenan, Francis P.
    In this paper we investigate the validity of the optically thin assumption in the transition region of the late-type star AU Mic. We use Far-Ultraviolet Spectroscopic Explorer (FUSE) observations of the C iii multiplet and Ovi resonance lines, hence y . . .
  • Sq87bx66f?file=thumbnail
    Article
    Mathioudakis, Mihalis
    Detection of 6Li has been shown for energetic solar events, one chromospherically active binary, and several dwarf halo stars. We had previously found a 6Li / 7Li � 0:03 0:01 for active K dwarf GJ 117 using VLT UVES observations. Here we present high . . .
  • F7623g474?file=thumbnail
    Article
    Keenan, Francis P.
    We present far-UV and UV spectroscopic observations of Proxima Centauri obtained as part of our continued investigation into the optically thin approximation assumed for the transition regions of late-type stars. Significant opacity is found in the C . . .
  • Pn89d942h?file=thumbnail
    Article
    Keenan, Francis P.
    Context. Radiative transfer calculations have predicted intensity enhancements for optically thick emission lines, as opposed to the normal intensity reductions, for astrophysical plasmas under certain conditions. In particular, the results are predic . . .
  • 4q77fv248?file=thumbnail
    Article
    Thorstensen, John R.
    We present x-ray, ultraviolet, and optical observations of the mysterious EUV/soft x-ray source EUVE J0356-336 (= MS0354.6-3650). Initial Einstein observations identified this source with a cluster of galaxies, but the relatively high source count rat . . .
  • N009w5304?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We study the temporal evolution of the Na i D1 line profiles in the M3.9 flare SOL2014-06-11T21:03 UT, using observations at high spectral resolution obtained with the Interferometric Bidimensional Spectrometer instrument on the Dunn Solar Telescope c . . .
  • C534fr702?file=thumbnail
    Article
    Mathioudakis, Mihalis
    The Extreme Ultraviolet Explorer (EUVE) Right Angle Program (RAP) obtains photometric data in four bands centered at 100 (Lexan/B), 200 (Al/Ti/C), 400 (Ti/Sb/Al), and 550 (Sn/SiO) during pointed spectroscopic observations. RAP observations are up to 2 . . .
  • 8c97kt35x?file=thumbnail
    Article
    Mathioudakis, Mihalis
    We present the serendipitous detection of an extreme-ultraviolet flare on EUVE J0613-3.9B. The flare showed over a 200-fold increase above the quiescent emission in the DS/Lexan 60-200 A wavelength band. Optical spectroscopy revealed that the event wa . . .
  • 6h440w202?file=thumbnail
    Article
    Lee, Jeongwoo
    The He I D3 line has a unique response to a flare impact on the low solar atmosphere and can be a powerful diagnostic tool for energy transport processes. Using images obtained from the recently digitized films of the Big Bear Solar Observatory, we re . . .
  • Work
    Conference paper or proceedings
    Lawrence, John K.
    Rapid Oscillations in the Solar Atmosphere (ROSA) instrument (Jess et al. 2010, Solar Phys, 261, 363) at the Dunn Solar Telescope. This can produce simultaneous observations in up to six channels, at different heights in the photosphere and chromosphe . . .
  • Qv33s015r?file=thumbnail
    Article
    Keenan, Francis P.
    Aims. High temporal and spatial resolution observations from the Rapid Oscillations in the Solar Atmosphere (ROSA) multiwavelength imager on the Dunn Solar Telescope are used to study the velocities of small-scale H? jets in an emerging solar active r . . .