BACK 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

BACK Contents  Introduction  Handling the data  Selection strategy  Results  Instrumental effects  Conclusions

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

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

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

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

BACK Electric Field and Wave experiment  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

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

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

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

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

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

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

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

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

BACK  Contents  Introduction  Handle data  Sel. Strategy  Results  Instr. effects  Conlusions 500 zero crossings (Jan-May, ) 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 Catagories

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

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

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

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

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

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

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

BACK Conclusions  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

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