31 research outputs found
Observation and Modeling of Coronal "Moss" With the EUV Imaging Spectrometer on Hinode
Observations of transition region emission in solar active regions represent
a powerful tool for determining the properties of hot coronal loops. In this
Letter we present the analysis of new observations of active region moss taken
with the Extreme Ultraviolet Imaging Spectrometer (EIS) on the \textit{Hinode}
mission. We find that the intensities predicted by steady, uniformly heated
loop models are too intense relative to the observations, consistent with
previous work. To bring the model into agreement with the observations a
filling factor of about 16% is required. Furthermore, our analysis indicates
that the filling factor in the moss is nonuniform and varies inversely with the
loop pressure
Solar astronomy
An overview is given of modern solar physics. Topics covered include the solar interior, the solar surface, the solar atmosphere, the Large Earth-based Solar Telescope (LEST), the Orbiting Solar Laboratory, the High Energy Solar Physics mission, the Space Exploration Initiative, solar-terrestrial physics, and adaptive optics. Policy and related programmatic recommendations are given for university research and education, facilitating solar research, and integrated support for solar research
UV-optical from space
The following subject areas are covered: (1) the science program (star formation and origins of planetary systems; structure and evolution of the interstellar medium; stellar population; the galactic and extragalactic distance scale; nature of galaxy nuclei, AGNs, and QSOs; formation and evolution of galaxies at high redshifts; and cosmology); (2) implementation of the science program; (3) the observatory-class missions (HST; LST - the 6m successor to HST; and next-generation 16m telescope); (4) moderate and small missions (Delta-class Explorers; imaging astrometric interferometer; small Explorers; optics development and demonstrations; and supporting ground-based capabilities); (5) prerequisites - the current science program (Lyman-FUSE; HTS optimization; the near-term science program; data analysis, modeling, and theory funding; and archives); (6) technologies for the next century; and (7) lunar-based telescopes and instruments
Observations of Active Region Loops with the EUV Imaging Spectrometer on Hinode
Previous solar observations have shown that coronal loops near 1 MK are
difficult to reconcile with simple heating models. These loops have lifetimes
that are long relative to a radiative cooling time, suggesting quasi-steady
heating. The electron densities in these loops, however, are too high to be
consistent with thermodynamic equilibrium. Models proposed to explain these
properties generally rely on the existence of smaller scale filaments within
the loop that are in various stages of heating and cooling. Such a framework
implies that there should be a distribution of temperatures within a coronal
loop. In this paper we analyze new observations from the EUV Imaging
Spectrometer (EIS) on \textit{Hinode}. EIS is capable of observing active
regions over a wide range of temperatures (\ion{Fe}{8}--\ion{Fe}{17}) at
relatively high spatial resolution (1\arcsec). We find that most isolated
coronal loops that are bright in \ion{Fe}{12} generally have very narrow
temperature distributions ( K), but are not
isothermal. We also derive volumetric filling factors in these loops of
approximately 10%. Both results lend support to the filament models.Comment: Submitted to ApJ