Cluster observation of electron acceleration by ULF Alfvén waves. Above the auroral region at altitude of 5-6Re, periodic upward (sometimes downward) electron beams are often observed by CLUSTER. They are coincide with ULF Alfvén waves (E- and B- field disturbance) of few minutes. - PowerPoint PPT Presentation
Cluster observation of electron acceleration by ULF Alfvén waves • Above the auroral region at altitude of 5 -6Re, periodic upward (sometimes downwar d) electron beams are often observed by C LUSTER. • They are coincide with ULF Alfvén waves (E- and B- field disturbance) of few minu tes. • The coexistence of the beams and the ULF waves implies their close relationship. OUTLINE • CLUSTER observation above the nightside auroral re gion – High latitude (~70˚-80˚) – Altitudes: 5-6 R E – Periodic upward electron flux structures – Electric/Magnetic field disturbances at similar perio d – DMSP conjunction observation • Temporal/Spatial signatures by four S/C observatio ns – E/B ratio: Signatures of Alfvén waves – Downward Poynting flux comparable to electron’s energ y – Electron acceleration signatures shows time viabiliti es. – Wave forms do not look like structure. – Vortex structure.
• Above the auroral region at altitude of 5-6Re, periodic upward (sometimes downward) electron beams are often observed by CLUSTER.
• They are coincide with ULF Alfvén waves (E- and B- field disturbance) of few minutes.
• The coexistence of the beams and the ULF waves implies their close relationship.
OUTLINE• CLUSTER observation above the nightside auroral region
– High latitude (~70˚-80˚)– Altitudes: 5-6 RE
– Periodic upward electron flux structures– Electric/Magnetic field disturbances at similar period– DMSP conjunction observation
• Temporal/Spatial signatures by four S/C observations– E/B ratio: Signatures of Alfvén waves– Downward Poynting flux comparable to electron’s energy– Electron acceleration signatures shows time viabilities.– Wave forms do not look like structure. – Vortex structure.
summaryAbout 2 minutes oscillation of electron loss c
orn/upward electron beam and E-field, B-field have been observed at the plasmasheet boundary above the auroral region.They are coincide with …
Upward field aligned current regionUpward ion beam region.
E-, B- field disturbances are likely to be Alfvén waves, and the electrons are accelerated directly by the Alfvén waves.
• E/B ratio: Signatures of Alfvén waves• Downward Poynting flux comparable to electron’s energ
y• Electron acceleration signatures shows time viabilities.• Wave forms do not look like structure. • Several hundreds km of perpendicular wave length.• Vortex structure.
