Hi again,

 

     I've received several requests for the IDL routine that does the ICSI correction described in the paper I sent earlier. Here it is.

The inputs are the arrays of intensity and wavelength of the original data. The outputs are an array of corrected intensity at the original spectral resolution, and arrays of intensity and wavelength at a finer spectral resolution (based on spline interpolation). If you are doing some sort of fit (e.g., single or multiple Gaussian), you should apply the fit to the corrected intensities at the original resolution. If you are computing blue-red asymmetries, for example, you may find it useful to use the fine resolution data. Please let me know if you have any questions.

 

Cheers,

Jim

 

From: Klimchuk, James A. (GSFC-6710)
Sent: Monday, June 29, 2015 8:55 AM
To: (Loops@solar.physics.montana.edu)
Subject: new spectroscopic analysis tool

 

Hi everyone,

 

    You might be interested in a new tool that Spiros, Durgesh, and I have developed for analyzing spectra. It can be downloaded from http://lanl.arxiv.org/abs/1506.08102.  The abstract is below.

 

Hope to see many of you at Loops VII,

Jim

 

The detailed shapes of spectral line profiles provide valuable information about the emitting plasma, especially when the plasma contains an unresolved mixture of velocities, temperatures, and densities. As a result of finite spectral resolution, the intensity measured by a spectrometer is the average intensity across a wavelength bin of non-zero size. It is assigned to the wavelength position at the center of the bin. However, the actual intensity at that discrete position will be different if the profile is curved, as it invariably is. Standard fitting routines (spline, Gaussian, etc.) do not account for this difference, and this can result in significant errors when making sensitive measurements. Detection of asymmetries in solar coronal emission lines is one example. Removal of line blends is another. We have developed an iterative procedure called Intensity Conserving Spline Interpolation (ICSI) that corrects for this effect. As its name implies, it conserves the observed intensity within each wavelength bin, which ordinary fits do not. Given the rapid convergence, speed of computation, and ease of use, we suggest that ICSI be made a standard component of the processing pipeline for spectroscopic data.

 

 

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James A. Klimchuk

NASA Goddard Space Flight Center

Solar Physics Lab, Code 671

Bldg. 21, Rm. 158

Greenbelt, MD  20771

USA

 

Phone:  1-301-286-9060

Fax:      1-301-286-7194

E-mail:  James.A.Klimchuk@nasa.gov

Homepage:  http://science.gsfc.nasa.gov/sed/index.cfm?fuseAction=people.jumpBio&&iPhonebookId=15844

 

No endorsement by NASA is implied for any correspondence related to my official role in professional organizations.

 

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