HAO 2010 PROFILES IN SCIENCE: Dr. Philip Judge
Contact
303-494-1502
judge@ucar.edu
Dr. Philip Judge is a Senior Scientist in the High Altitude Observatory. His research interests include spectroscopy and spectropolarimetry of the solar atmosphere, with emphasis on understanding the free energy available to the solar chromosphere and corona. From October 2009-2010 he has focussed on the physical structure of strongly magnetized regions of the solar chromosphere, the diagnosis of coronal electron temperatures, and coronal structure during the extended sunspot minima of 1901 and 2009.
Professional Website(s): Phil Judge
Publication:
(1) Judge, Philip G. 2010, The Astrophysical Journal, 708, 1238 Coronal Emission Lines as Thermometers.
Abstract:
Coronal emission-line intensities are commonly used to measure electron temperatures using emission measure and/or line ratio methods. In the presence of systematic errors in atomic excitation calculations and data noise, the information on underlying temperature distributions is fundamentally limited. Increasing the number of emission lines used does not necessarily improve the ability to discriminate between different kinds of temperature distributions.
Publication:
(2) Judge, Philip G. 2010, ArXiv e-prints The chromosphere: gateway to the corona, or the purgatory of solar physics?
Abstract:
In the paper the author argued that one should attempt to understand the solar chromosphere not only for its own sake, but also if one is interested in the physics of: the corona; astrophysical dynamos; space weather; partially ionized plasmas; heliospheric UV radiation; the transition region. Curious observations were presented which the author found puzzling and deserving of attention.
Publication:
(3) Judge, P. G., Burkepile, J., de Toma, G., & Druckmüller, M. 2010, Astronomical Society of the Pacific Conference Series, 428, 171 Historical Eclipses and the Recent Solar Minimum Corona.
Abstract:
We have studied the corona as seen at the eclipses of 1878, 1900, 1901, and others. These eclipses occurred during extended sunspot minimum conditions. We compare these data with those of the recent solar minimum corona, using data from the eclipses of July 22, 2009 and August 1, 2008. An attempt to characterize the global solar magnetic fields is made. We speculate on the origin of the non-dipolar structure seen in the 2008 and 2009 eclipse images.
Publication:
(4) Judge, Philip G. & Carlsson, Mats 2010, The Astrophysical Journal 719, 469 On the Solar Chromosphere Observed at the LIMB with Hinode.
Abstract:
Broadband images in the Ca II H line, from the Broadband Filter Imager (BFI) instrument on the Hinode spacecraft, show emission from spicules emerging from and visible right down to the observed limb. Surprisingly, little absorption of spicule light is seen along their lengths. We present formal solutions to the transfer equation for given (ad hoc) source functions, including a stratified chromosphere from which spicules emanate. The model parameters are broadly compatible with earlier studies of spicules. The visibility of Ca II spicules down to the limb in Hinode data seems to require that spicule emission be Doppler shifted relative to the stratified atmosphere, either by supersonic turbulent or organized spicular motion. The non-spicule component of the chromosphere is almost invisible in the broadband BFI data, but we predict that it will be clearly visible in high spectral resolution data. Broadband Ca II H limb images give the false impression that the chromosphere is dominated by spicules. Our analysis serves as a reminder that the absence of a signature can be as significant as its presence.
Publication:
(5) Judge, Philip, Knölker, Michael, Schmidt, Wolfgang, & Steiner, Oskar 2010, The Astrophysical Journal 720, 776 A Chromospheric Conundrum?
Abstract:
We examine spectra of the Ca II H line, obtained under good seeing conditions with the VTT Echelle Spectrograph in 2007 June, and higher resolution data of the Ca II 8542 line from Fabry-Perot instruments. The VTT targets are areas near disk center that include quiet Sun and some dispersed plage associated with small pores. Bright chromospheric network emission patches expand little with wavelength from line wing to line center, i.e., with increasing line opacity and height. We argue that this simple observation has implications for the force and energy balance of the chromosphere, since bright chromospheric network emission is traditionally associated with enhanced local mechanical heating that increases temperature and pressure. Simple physical considerations then suggest that the network chromosphere may not be able to reach horizontal force balance with its surroundings, yet the network is a long-lived structure. We speculate on possible reasons for the observed behavior. By drawing attention to a potential conundrum, we hope to contribute to a better understanding of a long-standing unsolved problem: the heating of the chromospheric network.
