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!!!A guide to accessing and analyzing EIS data
[{ALLOW edit EISMainUsers}]
[{ALLOW view Anonymous}]
%%(color:red;)__This page is still under construction. All of the information should be accurate, but some of the links are broken.__%%
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This guide describes how to access, calibrate and derive scientific results from the EIS instrument on Hinode. For a description of EIS and its observing modes please consult the instrument paper, [Culhane et al. (2007)|http://adsabs.harvard.edu/abs/2007SoPh..243...19C], and the [MSSL Science Centre webpage|http://msslxr.mssl.ucl.ac.uk:8080/SolarB/].
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!!!EIS data analysis guide
This guide describes how to access, calibrate and derive scientific results from the EIS instrument on Hinode. For a description of EIS and its observing modes please consult the instrument paper, [Culhane et al. (2007)|http://adsabs.harvard.edu/abs/2007SoPh..243...19C], and the [MSSL Science Centre webpage|https://vsolar.mssl.ucl.ac.uk/SolarB/].
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There are several methods for searching and downloading EIS data and these are summarized below. Follow the links to find more details.
Each country contributing to the Hinode mission provides access to the data through web portals. Each one offers different capabilities and so it is recommended that you try each to familiarize yourself with the methods for searching for data. The four data access points are given below and we also list an IDL-based tool for accessing data.
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[Hinode Science Data Centre Europe|SDCEurope] \\
Contains all of the Hinode data and has very flexible search tools.
[Hinode Science Data Centre (Europe)|http://elnath.uio.no/search/API] \\
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[MSSL Science Centre|MSSLArchive]\\
EIS/XRT/SOT data all available. View thumbnails/movies for EIS data set; uses SQL for flexible searches.
[MSSL Science Centre (UK)|https://vsolar.mssl.ucl.ac.uk/SolarB/]\\
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[Virtual Solar Observatory|VSOArchive]
[Hinode Data Centre, DARTS (Japan)|http://darts.isas.jaxa.jp/hinode]\\
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[EIS_CAT|EISCAT]
[Virtual Solar Observatory (US)|http://virtualsolar.org]
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[EIS_CAT (IDL tool)|EISCAT]
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{{{
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}}}
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an explanation of these keywords and a description of the calibration steps performed by eis_prep are available in [EIS Software Note No. 1|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_01.pdf].
an explanation of these keywords and a description of the calibration steps performed by eis_prep are available in [EIS Software Note No. 1|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/01_EIS_PREP/eis_swnote_01.pdf].
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{{{
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}}}
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After you have calibrated your data with eis_prep and had a quick-look at the contents you will be ready to do more detailed analysis from the IDL command line. There are two options:
A complete data-set is read into IDL as an object as follows:
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# Read all EIS data into an IDL object
# Read an individual wavelength window into an IDL structure ([EIS_GETWINDATA|EISGetWindata])
{{{
IDL> data=obj_new('eis_data',filename)
}}}
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Many of the EIS analysis routines make use of the EIS_GETWINDATA structures, and so this is generally recommended.
where 'filename' is the name of the level-1 file (a level-0 file can be read in the same way). The contents of the object can be read and manipulated through a large number of methods and an overview of some of the most useful methods is given below.
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[EIS object methods|EISmethods]
The routine [EIS_GETWINDATA|EISGetWindata] is also available if you want to extract a single EIS data window into an IDL structure. Some routines (e.g., EIS_AUTO_FIT) require as input the structures produced by EIS_GETWINDATA.
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The 1" and 2" slits return emission line spectra and a basic task for such data-sets is to fit Gaussians to the emission lines to return intensity, centroid and width information. Gaussian fitting routines available to EIS users are described below. Interpretation of centroids and widths is hampered by certain instrumental effects and these are dealt with in the sections below.
The 1" and 2" slits return emission line spectra and a basic task for such data-sets is to fit Gaussians to the emission lines to return intensity, centroid and width information. Gaussian fitting routines available to EIS users are described below. The routines correct for most instrumental effects, but users should familiarize themselves with some of these effects through the software notes listed below:
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* Warm and hot pixels (Software Notes 6 and 13)
* Orbital drift of line centroids (Software Note 5)
* EIS slit tilts (Software Note 4)
* EIS grating tilt (Software Note 3)
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!Intensity maps
Fitting a Gaussian function to an emission line yields measures of the line intensity, centroid (velocity) and width. Single Gaussian fits to individual lines are possible using [EIS object methods|EISmethods], while more sophisticated fitting options are available through the EIS_AUTO_FIT and SPEC_GAUSS_EIS routines available in Solarsoft. Documents describing these routines and giving examples are listed below.
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!Velocity maps
[Gaussian fitting for the Hinode/EIS mission|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/fitting/eis_auto_fit.pdf]\\
[Gaussian fitting examples using eis_auto_fit|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/fitting/eis_auto_fit_examples.pdf]
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!Line width maps
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Users should be aware that EIS line profiles can often take on non-Gaussian shapes which may contain valuable scientific information (e.g., [Chifor et al. 2008|http://adsabs.harvard.edu/abs/2008A%26A...481L..57C,], [De Pontieu et al. 2009|http://adsabs.harvard.edu/abs/2009ApJ...701L...1D,]).
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!!Slot data (40", 266" slits)
Some emission line ratios are sensitive to the electron density, and software is available to take the line fit structures output by EIS_AUTO_FIT and convert them to electron density maps. The density then allows the emitting column depth of the plasma to be determined which in turn allows the filling factor of the plasma to be estimated. The document below describes how this done, making use of atomic data from the [CHIANTI database|http://www.chiantidatabase.org].
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The EIS slots produce images rather than spectra, and the most common application will be to produce movies from the slot rasters in a range of emission lines. Diagnostics are possible with the slots, however, by taking ratios of images and temperature and density diagnostics are described below.
Deriving densities from Hinode/EIS data
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!Making movies
!Emission measure
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!Temperature diagnostics
When line intensities are available from several different ions, then an emission measure (EM) or differential emission measure (DEM) distribution can be constructed. No specific EIS software is available for doing this and so users are referred to software in the CHIANTI database, in particular:
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!Density diagnostics
integral_calc.pro: computes an EM value from a single line intensity\\
chianti_dem.pro: computes a DEM distribution from multiple line intensities
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!!Pointing and co-alignment
Another popular DEM code is available within the [PINTofALE|http://hea-www.harvard.edu/PINTofALE/] software package.
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Most EIS users will be analyzing data-sets from multiple instruments and so it is necessary to determine where an EIS raster is positioned relative to the other instruments. Usually the pointing information within an EIS file will not be good enough to accurately co-align data-sets and so cross-correlation will be necessary.
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!How to get the most accurate EIS coordinates
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!EIS and IDL maps
!!Slot data (40", 266" slits)
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The set of [IDL map software|http://beauty.nascom.nasa.gov/~zarro/idl/maps/maps.html] of D. Zarro is a popular means for handling solar image data. The situation is more complicated for EIS than imaging instruments as an image can be an intensity, velocity or line width map. EIS maps are generated from EIS data objects as follows (in the case of a velocity map from Fe XII 195.12):
The EIS slots produce images rather than spectra, and the most common application will be to produce movies from the slot rasters in a range of emission lines. Diagnostics are possible with the slots, however, by taking ratios of images and temperature and density diagnostics are described below.
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IDL> obj=obj_new('eis_data', filename)\\
IDL> m=obj_new('eis_moment',obj,iwin=195.12)\\
IDL> mmap=m->mk_eis_map(195.12,/vel)
!Making movies
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The output mmap is in the standard format accepted by the map software.
!Temperature diagnostics
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To generate an intensity map use keyword /int and for a line width map use /wid. When the 'eis_moment' object is created (step 2) a widget will pop up allowing you to define the spectral region containing the emission line. Moments are used to generate the velocity and line widths which ensures quick results. You can use Gaussian fitting by giving the additional keyword fit='gauss' in step 2 for the eis_moment call.
!Density diagnostics
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!Cross-correlation with SOT and XRT
!!Pointing and co-alignment
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!Cross-correlation with EIT and TRACE
Most EIS users will be analyzing data-sets from multiple instruments and so it is necessary to determine where an EIS raster is positioned relative to the other instruments. Usually the pointing information within an EIS file will not be good enough to accurately co-align data-sets and so cross-correlation will be necessary.
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* [Obtaining pointing information from EIS data|EISPointing]
* [Creating an IDL map from EIS data|EISMaps]
* [Cross-correlating EIS and SOT images|EISSOTcoalign]
* [Cross-correlating EIS and XRT images|EISXRTcoaling]
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[Software Note No. 1|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_01.pdf] - eis_prep\\
[Software Note No. 2|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_02.pdf] - Radiometric calibration\\
[Software Note No. 1|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/01_EIS_PREP/eis_swnote_01.pdf] - eis_prep\\
[Software Note No. 2|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/02_RADIOMETRIC_CALIBRATION/eis_swnote_02.pdf] - Radiometric calibration\\
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[Software Note No. 4|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_04.pdf] - Slit tilts\\
[Software Note No. 4|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/04_SLIT_TILT/eis_swnote_04.pdf] - Slit tilts\\
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[Software Note No. 6|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_06.pdf] - Hot and Warm pixels\\
[Software Note No. 6|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/06_HOT_WARM_PIXELS/eis_swnote_06.pdf] - Hot and Warm pixels\\
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[Software Note No. 9|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_09.pdf] - EIS Pointing\\
[Software Note No. 10|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_10.pdf] - Dark Current\\
[Software Note No. 11|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_11.pdf] - JPEG Compression\\
[Software Note No. 12|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_12.pdf] - Stray Light \\
[Software Note No. 13|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/eis_swnote_13.pdf] - Interpolation of missing EIS data\\
[Software Note No. 9|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/09_POINTING/eis_swnote_09.pdf] - EIS Pointing\\
[Software Note No. 10|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/10_DARK_CURRENT/eis_swnote_10.pdf] - Dark Current\\
[Software Note No. 11|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/11_JPEG_COMPRESSION/eis_swnote_11.pdf] - JPEG Compression\\
[Software Note No. 12|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/12_STRAY_LIGHT/eis_swnote_12.pdf] - Stray Light \\
[Software Note No. 13|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/13_INTERPOLATION/eis_swnote_13.pdf] - Interpolation of missing EIS data\\
[Software Note No. 14|https://hyperion.nascom.nasa.gov/svn/eis/release/doc/eis_notes/14_BP_TRIGGER/eis_swnote_14.pdf] - The EIS Bright Point Trigger\\
This page (revision-28) was last changed on 18-Apr-2021 19:17 by PeterYoungTop