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Welcome to the VARIFORC download page

VARIFORC: A software package for advanced processing of first-order reversal curves

VARIFORC is the first software package dedicated to advanced processing of first-order reversal curves (FORC). It offers state-of-the-art processing tools, such as weighted polynomial regression, heteroscedastic error calculations, variable smoothing for optimal noise suppression, manual/automatic handling of problems related to high-resolution features (ridges, rectangular hysteresis loops with very steep flanks), as well as special tools for coercivity analysis and central ridge processing.

VARIFORC is a set of modules dedicated to standard processing tasks (e.g., import single/multiple measurement sets, correct drift and outliers, calculate the FORC diagram), customized plotting (contour lines, significance tests), and modeling (e.g., linear combination of FORC datasets/diagrams, ridge extraction). All processing parameters can be stored for later use on similar datasets.

VARIFORC runs with Wolfram Mathematica and Mathematica PlayerPro. Previous knowledge of Mathematica is not required. Mathematica PlayerPro is recommended for users not interested in Mathematica applications, because of the reduced licensing costs (ca. 240 US$ or 190 € plus taxes). See the user manual about installation and further details.

The new version (version 2) comes with several important improvements and downloadable application examples. Each example focus on specific materials that can be processed in the same manner (magnetofossil-bearing sediments, volcanic rocks with pseudo-single-domain signatures, etc.), or on specific processing problems (correction of first measurement points, magnetic viscosity, etc.). Each application example provides sets of VARIFORC processing parameters that can be used to analyze FORC measurements of similar materials.

The following VARIFORC modules are currently available for download, along with detailed instructions and working examples:

ImportFORC (import and correct single/multiple FORC measurements)

• Supports all known FORC data formats generated by PMC MicroMag magnetometers • Correct measurement drift, transient instabilities, and outliers • Check and optionally corrects pro­blems with first and last measurement points • Manage field/magnetization units and normalize measurements by mass, volume, and area • Average mul­tiple measurements for noise reduction • Calculate hysteresis parameters with manual or automatic paramagnetic corrections • Plot and export corrected FORC measurements and measurement differences for further processing.

CalculateFORC (calculate and plot FORC diagram matrices)

• Free choice of the FORC region to be calculated, including measurement points located outside the standard rectangular FORC space • Automatic/manual choice of the output grid on which the FORC function is computed (for seamless combination with other FORC data) • Weighted and unweighted polynomial regression • Conventional FORC processing with constant smoothing factors • Advanced FORC processing based on variable smoothing for optimal noise suppression • Processing options for challenging datasets (e.g. vertical ridge, central ridge, very squared hysteresis)  • Mean field correction (new in version 2.0)  • Heteroscedastic error calculation and significance estimates • Automatic calculation of FORC-derived magnetizations and coercivity distributions • Export FORC matrices and coercivity distributions with metadata for further processing with VARIFORC or third-party software.

PlotFORC (plot high-quality FORC diagrams)

• Choose the FORC region to be plotted and zoom on details such as the central ridge region • Use specially developed color scales for optimal representation of high- and low amplitude details • Draw contour lines automatically or manually at any specified level and exclude small contour loops generated by measurement noise • Draw contours enclosing significant regions of the FORC diagram • Plot FORC diagrams with normalized vertical profiles for estimating the vertical width (useful for interaction field reconstruction and a selection tool for absolute paleointensity determinations) • Export publishing-quality FORC diagram images (vector and raster formats).

IsolateCR (process central ridges)

• Isolate central ridges from other FORC contributions • Plot the central ridge and other FORC contributions individually with corresponding heterosce­dastic error estimates • Calculate the central ridge coercivity distribution and plot it together with other two FORC-derived coercivity distributions • Export FORC components and coercivity distributions for further processing with VARIFORC or third-party software.

LinearCombineFORC (calculate linear combinations of FORC data)

• Calculate any linear combination of an arbitrary number of FORC datasets (corrected measurements or FORC matrices) • Average measurements obtained with different FORC protocols • Subtract a background (e.g. sample holder) • Isolate the contribution of specific minerals by calculating measurement differences upon selective magnetic/chemical extraction.

News and Updates

The Conrad Observatory homepage will be upgraded. After this upgrade, examples with large source files will be available.

20.05.2014: Version 1.00 released with processing examples based on a pelagic carbonate.

25.05.2015: Version 2.00 released. VARIFORC processing examples have been added. Due to download size limitations, large source files are not available.

02.06.2015: Version 2.01 update. Minor bugs removed from ImportFORC (hysteresis loop calculation and first/last point correction). Missing installation file for LinearCombinedFORC has been added.

03.06.2015: Version 2.02 update. Bug removed from LinearCombineFORC (corrected measurement import/export). PlotFORC has been modified for plotting FORC matrices with missing supplementary data (as produced by LinearCombineFORC when a master file has not been chosen).

28.09.2015: Version 2.03 update. Bugs removed from IsolateCR (vertical range checking and single profile plots).

 

Contact

Ramon Egli (ramon.egli@zamg.ac.at). Please report bugs (see instructions in Chapter 2 of the user manual), which will be corrected as soon as possible. Suggestions for improving VARIFORC and adding new functionalities are welcomed.

 

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