Abstract: The physical mechanisms that give rise to the high temperatures observed in the solar chromosphere, transition region, and corona are not understood. Detailed measurements of the physical properties in these regions of the solar atmosphere are needed to provide constraints to theoretical models. The instruments on Hinode and SoHO provide a unique opportunity to make spatially resolved spectroscopic observations over a very wide range of temperatures. In this HOP we propose to combine EIS, CDS, SUMER, XRT, SOT, and AIA observations to probe the density and temperature structure of solar atmosphere and its relationship with the photospheric magnetic field.
Background: There have been numerous attempts to measure the density and temperature structure of the solar atmosphere. One significant limitation of most previous measurements has been a lack of adequate temperature coverage. Most previous EUV and UV spectrometers have not been able to properly sample the highest temperatures (>3 MK) with high spatial resolution. The EIS spectrometer on Hinode has the capability of observing high temperature, active region emission in the 3-5 MK range with Ca XIV-XVII and Fe XVII. This is in addition to the many lower temperature coronal emission lines (Fe VII-Fe XVI). EIS observations, however, do not cover the transition region (0.1-0.8 MK) and chromosphere (<0.1 MK) very well. The CDS and SUMER spectrometers on SoHO, in contrast, cover these temperatures regions very well. The primary objective of these coordinated observations will be to obtain data that can be used to construct differential emission measures over the broadest possible temperature range.
Such measurements will be combined with Hinode/XRT and SDO/AIA observations to cross calibrate the DEM capabilities of these imaging instruments. Such observations will also allow us to probe the highest temperature active region emission (>10 MK) by using the thick XRT filters and the AIA Fe XVIII 94 channel.
Since full spectral coverage and large fields of view are mutually exclusive to the spectrometers we propose taking a raster with carefully selected spectral windows as well as atlas data covering a small field of view. For completeness we request that these observations be run in both the quiet Sun and in a large active region. Several hours of observing on each target will be required to accumulate the necessary data. |
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