Parallel electric fields in space Observations by Cluster satellites inside the auroral

1. Parallel electric fields in space Observations by Cluster satellites inside the auroral zone at altitudes above the main acceleration region Presentation of Master Thesis by Erik Bergman Dept.: Astronomy and Space Physics Instructor: Andris Vaivads Examiner: Annika Olsson

2. Introduction Handling the data Selection strategy Results Instrumental effects Conclusions Contents

3. Contents Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Discrete auroras Auroral oval Potential models Predictions of U andO-potentials EFW instrument Introduction

4. Contents Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Discrete auroras • Discrete auroral arcs: • Caused by electrons accelerated by parallelE-fields usually at 1-2 RE • North-South, 100 m – 80 km, typically 5 km • Mapped to Cluster altitude (~4.5 RE) this equals 50 km • At Cluster speed (~5 km/s) the size of parallel E-fields would be ~10 seconds

5. Contents Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Potential models

6. Contents Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Predictions of U and O-pot perp para 10 s Northern hemisphere

7. Contents Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Four identical probes Voltage mode, to measure electric fields, only in spinplane Current mode, to measure density and temperature of plasma Electric Field and Wave experiment

8. Contents  Introduction Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Coordinate systems Calculations and assumptions Filtering Handling the data

9. Contents  Introduction Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Coordinate systems

10. Contents  Introduction Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Calculations and assumptions

11. Contents  Introduction Handle data  Sel. Strategy  Results  Instr. effects  Conlusions Filtering

12. Contents  Introduction  Handle data Sel. Strategy  Results  Instr. effects  Conlusions Orbits Quicklook plots Overview plots Catagories Selection strategy

13. Contents  Introduction  Handle data Sel. Strategy  Results  Instr. effects  Conlusions Orbits o o Middle of March

14. Contents  Introduction  Handle data Sel. Strategy  Results  Instr. effects  Conlusions Quicklook Plot

15. Contents  Introduction  Handle data Sel. Strategy  Results  Instr. effects  Conlusions Overview Plot

16. Contents  Introduction  Handle data Sel. Strategy  Results  Instr. effects  Conlusions Catagories • 500 zero crossings (Jan-May, 2001-2002) • 57 events selected for closer inspection • Divided into four sub catagories • 16 – No activity • 23 – No perpendicular activity • 5 – Too active • 13 – Good events • 5 events selected from the good

17. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Parallel DC electric fields Double layers and solitary waves Waves Results

18. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Parallel DC electric fields

19. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Parallel DC electric fields All electric fields are upwards

20. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Double layers and solitary waves

21. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Accompanied by a decrease in plasma density DL and SW theory

22. Contents  Introduction  Handle data  Sel. Strategy Results  Instr. effects  Conlusions Waves

23. Contents  Introduction  Handle data  Sel. Strategy  Results Instr. effects  Conlusions Wake effects Physical Potential Offsets Interference from WHISPER Instrumental effects

24. Contents  Introduction  Handle data  Sel. Strategy  Results  Instr. effects Conlusions Possible interpretations of the results Upward ~1 mV/m parallel E-fields Too small, could be instrumental effects Could be U associated (not likely at this altitude) Could be lower part of O U on top of O (not probable) Lack of downward parallel E-fields Cluster measure above O, too high altitude Downward fields associated with O should be ~0.1 mV/m at this altitude, i.e. not measurable Conclusions

25. Thank you for listening The End

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27. 2002-01-10

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31. 2002-02-06

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