# Presentation: 614705

## Analysis of IMS Data

- By Ed Sittler
- CAPS Team Meeting #28
- Marseille, France
- July 26-28, 2004

## Analysis of TOF Data

- Purpose:
- Determine ion composition
- Revise calibration parameters for FM
- Peak shifts
- Peak Amplitudes and widths
- Algorithm
- Read routine which sums bcycle data in 2D arrays for ST & LEF.
- Use highest data rate modes (I.e., 4, 8, 16 kbps).
- Set start and stop times.
- Store data in file.
- Read file from previous step.
- Make 2D color spectrograms.
- Make line plots of TOF data for specific estep.
- Perform non-linear least-squares fit to TOF data.
- Can do up to 10 ions. Use line profile parameters as given. Only adjust ion counts.
- Presently we can shift the ion peaks manually. We also fit simultaneously to the background.
- First do manual fit.
- Then do non-linear fit. Compute chisqr.
- Plot Results.
- Further generalizations being considered.

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## ST TOF Spectrum 182(23:24) No Shift

## ST TOF Spectrum 182(23:24) Shifted

## LEF TOF Spectrum 182(23:24)

## ST TOF Spectrum 182(18:24) No Shift

## ST TOF Spectrum 182(18:24) Shifted

## LEF TOF Spectrum 182(18:24)

## ST TOF Spectrum 182(18:24) E = 30 eV

## LEF TOF Spectrum 182(18:24) E = 30 eV

## Summary of TOF Analysis Results

- Composition of H+, N+, Water Group Ions & O2+. Detection of H2+ ?
- Shift ~ 16 channels (2048) seems to be required.
- With no shift H3O+ tends to dominate, C+ more important and N+ less important.
- With shift H2O+ tends to dominate, N+ more important and C+ less important.
- LEF data shows H+, N+ and Water Group Ions. No C+ seen. O2+ can produce peak near N+ peak, but to shorter TOF. Therefore, less favored by data. Although O2+ is present it is not sufficiently intense.
- LEF data set ideal for detection of N+ since O+ has low sensitivity in LEF data (I.e., O+ tends to want electrons).
- ST O- peak shoulder to lower TOF not understood.
- Electronic peaks? Remove bad data (I.e., revise script pgm).

## Analysis of Ion Data

- Purpose:
- Determine ion composition.
- Determine distribution functions of individual ion species.
- Compute ion moments.
- Study performance of SAM algorithm and Group Tables.
- Incorporate revised FM cal parameters into ion analysis. Reconstruct ion counts from data. Required high rate data (4, 8 and 16 kbps)
- Procedure
- Read level0 data products for period 182(18:24). Sum data for various ion species as function of estep and angular sector.
- Study statistical properties and search for systematic effects as function of estep and angular sector.
- Plot data in appropriate format.
- Apply non-linear fitting algorithm which uses revised FM cal data derived from analysis of TOF data. Reconstruct true ion counts for all ion species. Manually, we have already been doing this.

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## Summary of Ion Data Analysis

- Overall ion data looks good.
- But, RTIU problem, especially within inner magnetosphere caused us to throw away a lot of the data. Script program helped but then bad data leaked into results. Localized spikes in data. Needs further work.
- Definite anti-correlations with estep between OH+ & H2O+
- Interpolation between esteps may cause systematic effects.
- If there were no systematic effects than anti-correlations would go away by summing over many spectra.
- Adding nearby esteps may remove some of the problem.
- Going to hardware binning should definitely fix the problem.
- Summing water group ions together removes anti-correlations. This was expected.
- Signal peaks in sector 2 as expected. Enhancement in sector 8 indicated pressure anisotropy effect?
- We will next need to apply non-linear fitting algorithm to reconstruct ion counts. Here, we would use revised FM cal parameters from analysis of TOF data.