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On-board Moments Calculation and Beacon Data for PLASTIC

This article explains the on-board moments calculation process for PLASTIC, using data from CLUSTER/CODIF and PLASTIC/IMPACT/SWEA. It discusses the density calculation and implementation, as well as the accumulation of separate sets of moments. It also mentions the higher order moments and provides an example of beacon data on the SSC web site.

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On-board Moments Calculation and Beacon Data for PLASTIC

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  1. PLASTIC On-board Moments Calculation and Beacon Data Lynn M. Kistler Space Science Center UNH

  2. Moments The on-board moments calculation is based on that done for CLUSTER/CODIF, and for PLASTIC/IMPACT/SWEA. They are simple sums (not fits) over the available data. Density is given by: Where  is the polar (deflector) angle and  is the azimuthal (position) angle.

  3. Density Calculation We can pull out the constants in the sums, to get So what is actually performed on-board is: With the constants added later on the ground.

  4. Density Calculation • These sums are implemented using an array of counts of ions classified as H+ that fall in the solar wind sector. This arrays is passed to the moments routine for each ESA step and added to the sums. • Two separate sets of moments are accumulated: one for S-channel and one for non-S-Channel • The velocity and trigonometric functions are stored in tables for each of the 32 Position bins, 32 deflection steps, and 128 ESA steps. • Because of processing limitations, the whole 32Px32D array is not sent used. Instead, a 16P x 8D array is sent. • The D bins are centered on the peak. The 16P’s cover the full 45 degrees, using every other bin.

  5. Higher Order Moments The other moments (velocity, temperature, heat flux) are performed in a similar manner, using the appropriate velocity and and trigonometric functions.

  6. PLASTIC SSD-side Priority RatesFeb 11-12, 2007 Spacecraft A Spacecraft B SW H+ SW He++ SW Heavies SW Other WAP H+, He++ WAP Other

  7. SC/A Energy spec SC/B Energy spec SC/A deflection SC/B deflection

  8. A - black B - blue On-board moments n Sunward direction vx Position direction vy vz Deflection direction Txx Tyy Tzz Feb 11 Feb 12

  9. S/C B - 10 days March 15-24 SW H+ S/C B still not observing standard solar wind SW He++ SW Heavies SW Other WAP H+, He++ WAP Other

  10. S/C B - 2 days March 15-16 S/C B still not observing standard solar wind SW H+ Deflection (polar)

  11. Issues • Final Calibrations are not yet incorporated - density is currently off by ~x2 • S/C B is still in sheath, so densities low. • Still validating the ecliptic angle.

  12. On-board moments

  13. On-board moments

  14. Example of Beacon data on SSC web site

  15. The End

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