H: The Chromosphere,
Bart De Pontieu (16)

Last Updated Fri Dec 5 16:24:42 2008

1: Tony Arber (t.d.arber@warwick.ac.uk), University of Warwick [I]
[soi] The photosphere and chromosphere are sufficiently cold that there is a significant fraction of neutral hydrogen in these layers. Collisions with these neutrals change the nature of the plasma resistivity in such a way that cross-field currents experience a resistivity which may be many orders of magnitude larger than the classical Spitzer resistivity of a fully ionized plasma. I am interested in the effect of these neutrals on flux emergence, wave propagation and chromospheric reconnection.
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2: Mats Carlsson (mats.carlsson@astro.uio.no), Institute of Theoretical Astrophysics, University of Oslo [I]
[soi] my interest is in how numerical models have improved our understanding of the chromosphere, current and future capabilities, what physical processes must be included and how approximate treatments can make the resulting problem computationally tractable.
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3: Gianna Cauzzi (gcauzzi@arcetri.astro.it), INAF - OAA Firenze, Italy [G]
[soi] I would like to present some of the recent chromospheric observations and results obtained with the Interferometric BIdimensional Spectrometer (IBIS), most notably in CaII 854.2 nm and Halpha. The technique of imaging spectroscopy is currently our best tool to address the fully 3-D nature of the solar chromosphere and the need of high resolution spectroscopic information within extended FOVs, and the complexity and variety of the resulting data is at times bewildering. Within the WG I would like to discuss how to best interpret these 'information rich' observations especially with respect to coupling of different parts of the solar atmosphere and wave propagation.
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4: Rebecca Centeno (rce@ucar.edu), High Altitude Observatory (NCAR) [J]
[soi] TITLE: The He I 10830 A triplet: a tool for understanding chromospheric magnetism ABSTRACT: The access to chromospheric magnetism is pretty much restricted to a few spectral lines whose region of formation can span up to several hundred kilometers and several scale heights in the solar atmosphere. The interpretation of their intensity and polarization signatures requires solving the non-linear problem that couples the statistical equilibrium and the radiative transfer equations in highly sophisticated model atmospheres. Although an appropriate modeling of the He 10830 triplet is as complex as for any other chromospheric line, the interpretation of its Stokes profiles happens to be relatively straightforward in comparison. Due to its particular formation mechanism (triggered by EUV coronal light) this IR triplet is generated in a shallow layer at the top of the chromosphere, thus having no
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5: Bart De Pontieu (bdp@lmsal.com), Lockheed Martin Solar & Astrophysics Lab [C]
[soi] The dynamics of the upper chromosphere
[poster] Estimating the Absorption of Transition Region Emission Most coronal loop models predict signficantly more transition region emission at the footpoints of loops than is observed. We use SUMER, EIS and STEREO data of moss regions to estimate how the TR emission is impacted by Lyman continuum absorption from neutral hydrogen and helium in chromospheric jets that occur at the same heights as the TR emission. We provide new constraints on the amount of absorption, which should allow loop modellers to narrow down their assumptions about filling factors or spatio-temporal variability of the heating function.
6: Alfred De Wijn (dwijn@ucar.edu), High Altitude Observatory [C]
[soi] MHD waves of all kinds have been observed ubiquitously in the chromosphere for some time. Recent studies have shown that the corona is also permeated with waves. Oscillations with periods longer than the acoustic cut-off were traditionally assumed to be evanescent, but it is now clear that, under some circumstances, such oscillations may propagate from the photosphere into higher layers. A lively discussion currently remains as to what mechanisms and what circumstances allow propagation to occur. In this context, it is important to study wave propagation using high-resolution diagnostics of photospheric and chromospheric Doppler signals. We present the results of such a study and discuss its implications.
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7: Na Deng (ndeng@csun.edu), California State University Northridge (CSUN) [H]
[soi] I will present a simultaneous Stokes polarimetric observation in both photosphere and chromosphere. The observation was made by Advanced Stokes Polarimeter in conjunction with the AO system at NSO. The MgI b2 517.27 nm spectral line was used to probe the magnetic and velocity field in the low chromosphere. The asymmetric properties of Stokes profiles will be compared between photosphere and chromosphere.
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8: Bernhard Fleck (bfleck@esa.nascom.nasa.gov), ESA [C]
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9: Lyndsay Fletcher (lyndsay@astro.gla.ac.uk), University of Glasgow [E]
[soi] The emphasis of observational and theoretical flare studies in the last decade or two has been on the flare corona, and attention has shifted away from the flare's chromospheric aspects. However, although the pre-flare energy is stored in the corona, the radiative flare is primarily a chromospheric phenomenon. This introductory presentation will review the chromospheric diagnostics for the flare energy release and the problems thrown up by the application of these diagnostics. I will discuss the importance for flare energy transport of the strong variation of plasma properties across the chromosphere, covering also current ideas about the possible modes of flare energy transport from corona to chromosphere. I will present a forward look for future flare imaging and spectroscopic observations, and discuss how the theoretical and simulation architecture, currently available to study the non-flaring chromosphere, can find application in flare problems.
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10: Hiroaki Isobe (isobe@kwasan.kyoto-u.ac.jp), Kyoto University [E]
[soi] I am interested in magnetic reconnection in the chromosphere. Namely the effects of Hall and ambipolar terms in chromospheric reconnection, its role in chromospheric dynamics and coronal heating, and relation to small scale horizontal fields found by Hinode/SOT. I am also interested in particle acceleration in different kinds of reconnection-related events (flares, microflares, eruptive events in quiet sun, and reconnection in magnetosphere). Comparative studies of similar events in different plasma environments may reveal how particle acceleration is scaled with plasma parameters.
[poster] We present a comparative study of electron acceleration in solar corona and Earth magnetosphere. Non-thermal electrons are commonly observed in solar flares but not in the eruptive events in the quiet sun. This may be simply due to the weak magnetic/electric fields in the quiet sun. However, non-thermal electrons with similar energy to flares are commonly observed in magnetospheric reconnection events (related to substorms), though the magnetic/electric fields are orders of magnitude weaker. We try to measure the efficiency of electron acceleration by the ratio of the energy contents of high energy (say, E>10kT) electrons to thermal electrons. Our preliminary analysis shows that magnetosphere is stronger accelerator than the quiet sun, but weaker than the intense flares.
11: Stuart Jefferies (stuartj@ifa.hawaii.edu), Institute for Astronomy, University of Hawaii [C]
[soi] I am interested in the role MHD waves play in transporting energy throughout the chromosphere and corona
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12: Philip Judge (judge@ucar.edu), HAO, NCAR [G]
[soi] I am interested in the basic physics of the chromosphere and how it presents thermal and magnetic conditions to the corona.
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13: Scott McIntosh (mscott@ucar.edu), NCAR/HAO [B]
[soi] I am interested in the coupling of waves and magnetic structure in the chromosphere, transition region and corona, their impact in mass loading and heating of the atmosphere and wind. I have been investigating these phenomena using a host of observing platforms and techniques to build a consistent physical picture of this complex interface between high and low beta plasmas.
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14: Neil Murphy (neil.murphy@jpl.nasa.gov), Jet Propulsion Laboratory [H]
[soi] I am interested in the measurement and characterization of waves in the chromosphere and am working on the development of Doppler/magnetograph instrumentation
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15: Thomas Straus (straus@oacn.inaf.it), INAF - OAC, Napoli, Italy [H]
[soi] I am actually working on the contribution of acoustic-gravity waves to the energy balance of the chromosphere (see poster abstract)
[poster] We revisit the dynamics and energetics of the solar atmosphere, using a combination of high-quality observations and 3D numerical simulations of the overshoot region of compressible convection into the stable photosphere. We discuss the contribution of acoustic-gravity waves to the energy balance of the photosphere and low chromosphere. We demonstrate the presence of propagating internal gravity waves at low frequencies (< 5mHz). Surprisingly, these waves are found to be the dominant phenomenon in the quiet middle/upper photosphere and to transport a significant amount of mechanical energy into the atmosphere outweighing the contribution of high-frequency (> 5mHz) acoustic waves by more than an order of magnitude. We compare the properties of high-frequency waves in the simulations with results of recent high cadence, high resolution Doppler velocity measurements obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in conflict with the simple picture of upward propagating sound waves. We discuss the implications of our findings on the energy flux estimate at high-frequencies.
16: Han Uitenbroek (huitenbroek@nso.edu), Nastional Solar Observatory/Sacramento Peak [C]
[soi] I am interested in discussing the feasibility of measuring magnetic fields in the chromosphere through the zeeman effect in the CaII 854.2 nm line. I will illustrate possible requirements for such measurements with two-dimensional magneto-staitic models of small scale magnetic field concentrations that extend into the chromospehere. These models are created by solving consistently for the magnetostatic equations in a Wilson-depressed flux concentrations and radiative transfer in Hydrogen, to get a proper estimate of electron densities at chromospheric levels. Forward calculation of polarized radiative transfer in such models provides a first estimate of the polarization accuracy and sensitivity that is needed to detect the associated magnetic fileds, which turn out to be rather stringent.
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Second Choice

William Abbett, Thomas Berger, Roberto Casini, Na Deng, Yong Lin, Neil Murphy, Aimee Norton, Hardi Peter, Fatima Rubio da Costa, Pavol Schwartz, Gerald Share, Thomas Straus, Yang Su, Ted Tarbell, Luca Teriaca, Pia Zacharias,