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. 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 Fit between measured and calculated Ey (mgse)

4. Ey (mgse) (mV/m) Corot. frame Note the good agreement between the calculated (VscXB) y + E corot.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. RBSP A June 16, 2013 11:00 -22:30 UT

5. From Mozer 1973 The Ionospheric Dynamo is due to the atmospheric tides, and the induced ionospheric motion due to collision with the neutral atmosphere We may want to include the ionospheric dynamo E field in the EFW calibrations in the future. 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, June 10, 2013 Out bound In bound 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. May 15 –July 24, 2013 Van Allen Probe A Density (cm -3 ) Out bound Ey-mgse (mV/m) Corotating frame Out-bound Density (cm -3 ) In bound Ey-mgse (mV/m) Corotating frame In-bound

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 Ey corot. frame 60-300 keV protons n flux Plasma Density 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

9. Ey Solar Wind Dst Ey – mgse Ey – mgse (5 min ave.) mV/m Ring current energy change rate (J/s) Dessler and Parker [1959] E = energy of ring current particles Em = energy of earth’s dipole above the surface Bo = surface B field intensity ΔB = disturbance field 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). (a) (b) (c) (d) (e)

10. Ey (mgse) (corotating frame) (mV/m) 60-300 keV Protons Dst 60-300 keV proton Pressure nPa L shell Plasma Density cm -3 Plasma density Van Allen Probe A Inbound May 26 - June 6, 2013 Ey 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)

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