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Scott Thaller

Scott Thaller. Van Allen Probes EFW meeting University of Minnesota June 10-12, 2014. Electric field data quality “checklist”. The electric field data are spin fit The VscXB field is subtracted The field in the co-rotating frame is calculated and subtracted.

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Scott Thaller

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  1. Scott Thaller Van Allen Probes EFW meeting University of Minnesota June 10-12, 2014

  2. Electric field data quality “checklist” • The electric field data are spin fit • The VscXB field is subtracted • The field in the co-rotating frame is calculated and subtracted. • The antenna length correction is applied, but small ~1. • Data during eclipse times are removed • Data during charging intervals (Vsc < 0) are removed. • Data during spacecraft maneuvers and probe bias current sweeps are removed • The wave forms have been inspected for the storms to check for wake effect; wake effect intervals identified and removed • Probe bias currents for the interval are good.

  3. Fit between measured and calculated Ey (mgse) The Ey data for the fit is from Near Perigee: R < 2.0 RE Quiet times: -10 <Dst <10 From Sep 27, 2012 to Sep 1, 2013

  4. RBSP A June 16, 2013 11:00 -22:30 UT Note the good agreement between the calculated (VscXB)y + Ecorot.y and the actual measured Ey (mgse) field near perigee . Some residual is present, but we can still resolve some real E field, for example, there is some wave activity that appears to be present in this example. Ey (mgse) (mV/m) Corot. frame Ey (mgse) (mV/m)

  5. We may want to include the ionospheric dynamo E field in the EFW calibrations in the future. From Mozer 1973 The Ionospheric Dynamo is due to the atmospheric tides, and the induced ionospheric motion due to collision with the neutral atmosphere At low L there is an electric field ~0.5-0.8 mV/m due to atmospheric tides. This is comparable to the residual field at low L and so may need to be added to the calibration.

  6. Van Allen Probe A Ey-mgse (mV/m) Corotating frame In-bound Out bound Ey-mgse (mV/m) Corotating frame Out-bound In bound Density (cm-3) In bound Van Allen Probe A, June 10, 2013 Note the asymmetries between the in and out bound portions of the orbit. In bound electric fields do not appear to penetrate to as low L shells as during out bound passes. But densities seem to erode more significantly to lower L on the in-bound parts of the orbit. Note the residual E field at low L, <2 RE. Density (cm-3) Out bound May 15 –July 24 , 2013

  7. Kp 7 to 9- Kp 6,6+,7- Kp 4,4+,5- Kp 5,5+,6- Kp 3,3+,4- Kp 2,2+,3- Kp 1,1+,2- Kp 0,0+,1-

  8. Van Allen Probe A A region of strong dawn-ward electric field is observed at low L (<3 RE) in the post midnight sector during the major storm on June 1, 2013. This region of dawn-ward field corresponds to the sharp decrease in ring current proton number flux and the sharp boundary of the plasmapause. Such dusk-ward electric field could be shielding Eycorot. frame 60-300 keV protons n flux Plasma Density

  9. Solar wind dusk-ward electric field (a), enhancements in magnetosphereic waves (b) and dusk-ward convection field (c) enhance during the same interval, as well as the rate of ring current energization (d). mV/m (a) Ey Solar Wind Ey – mgse (b) mV/m (c) Ey – mgse (5 min ave.) mV/m Dessler and Parker [1959] Ring current energy change rate (J/s) (d) E = energy of ring current particles Em = energy of earth’s dipole above the surface Bo = surface B field intensity ΔB = disturbance field Dst (e)

  10. Van Allen Probe A Inbound May 26 - June 6, 2013 Ey Ey (mgse) (corotating frame) (mV/m) L shell The Ey (mgse) electric field in the co-rotating frame and corresponding plasmasphere erosion and ring current proton pressure increase. (the pressure shown here is a rough preliminary calculation) L shell Plasma Density cm-3 Plasma density 60-300 keVproton Pressure nPa L shell 60-300 keV Protons Dst

  11. Extras

  12. Coverage, or number of points per RE – Kp bin RBSP A Sep 27, 2012 – Apr. 15, 2014 Kp 7 to 9- Kp 6,6+,7- Kp 4,4+,5- Kp 5,5+,6- Kp 3,3+,4- Kp 2,2+,3- Kp 1,1+,2- Kp 0,0+,1-

  13. Figure courtesy John Wygant

  14. 40 mV/m Ey (mgse) (mV/m) Spatial integration of E and Ey along RBSP A trajectory for June 1, 2013 02:00-08:30 UT About 20 kV 4 km/s V spacecraft 25 kV 25 kV

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