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Comparison of STAFF-SA and WBD

Magnetic components of intense whistler-mode chorus

Prepared by Ondrej Santolik

14th CAA Cross-Calibration meeting, York, 5-7 Oct 2011

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Context

• No comparisons between STAFF SA and WBD using magnetic component had ever been presented. An action was pending:

• CC8 – AI-45 STAFF :To carry out a cross-calibration study between STAFF-SA and WBD as they appears to be not in good agreement with WBD above 700 Hz while WBD/Whisper shows moderately good agreement. O. Santolik was in charge of this action, to be done during the summer.

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Power spectrogram of the electric field fluctuations. (WBD)

Power spectrogram of the magnetic field fluctuations.(STAFF-SA)

Parallel component of the Poynting vector normalized by its standard deviation.(STAFF-SA)

Electromagnetic planarity.(STAFF-SA)

SOURCESOURCE

// Bo

\// Bo

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ZOOM on SOURCE REGIONZOOM on SOURCE REGION

Selected intervals of WBD magnetic-filed measurements 08:44:55- 8:53:48, compared with the STAFF-SA onboard analyzed data

• WBD • BY component in the spinning spacecraft system (10s ~every 50s when Whisper is active)• FFT of time series corresponding to STAFF-SA 4-s analysis intervals • Power is averaged in frequency intervals of 27 STAFF-SA frequency channels

• STAFF-SA • despun sunward component, analyzed onboard

WBD

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WBD and STAFF-SA data in 56 time intervals of 4 s and 27 freq. steps

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STAFF-SA Band A

But low power in band A

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STAFF-SA Band B

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STAFF-SA Band C

Better, but intense waves

Best

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A B C

Noise Low waves Strong waves

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Results• Large differences of obtained PSD at low frequencies < 60 Hz,

probably linked to the WBD high-pass filters. -> low signal, and no same sensitivity

• Median power ratio for f > 60 Hz is 1-5. STAFF-SA shows higher levels than WBD. (bands B & C)

• Large variations (~one order of magnitude)

• Very intense waves with PSD> 10-7 nT 2/Hz give similar values for STAFF-SA and WBD.

• Proper comparison is difficult, WBD samples one single spinning component, STAFF-SA gives onboard despun data.