• ROPA/REIMEI show ~300eV inverted-V type spatial structures

• Collocated with region of patches but not correlated with individual patches

• Low energy precipitation causing high altitude structures

• <100eV precipitation more field aligned

ROPA Launch Feb 12, 2007, 12:45:04 UT

UPWARD

DOWNWARD

ROPA Launch Feb 12, 2007, 12:45:04 UT

• Poker Flat Incoherent Scatter Radar observations of similar pulsating aurora on Jan 18 2007 show, in some directions, high altitude electron density enhancements that likely correspond to lower energy (<1keV) electron precipitation

ROPA Launch Feb 12, 2007, 12:45:04 UT

FAST study, Sato 2004

[Sato et al. 2004]

6 s pulsation

Accelerated electron flux enhancements (inverted-V): no clear correlation with the optical signatures.

Well correlated with temporal and spatial variations of the optical pulsating aurora.

• one-to-one correspondence between the downgoing, high energy (> 5 keV) electron flux and the optical pulsating aurora

• After “D-E”, the inverted-V structure appears to continue, although the > 5 keV flux is diminished: an inverted-V structure may not be a sufficient condition for producing a pulsating aurora.

COSPAR: current REIMEI study

Numerous direct observations by REIMEI show the pulsating aurora are caused by electrons repeatedly precipitating with energy dispersions and isotropic pitch angle distributions with a single loss cone. Some cases indicate that small inverted-V-type electron signatures are embedded between each of the pulsating electron components, which may suggest that the increase of the ionospheric conductivity by pulsating auroral precipitations restrains the growth of the inverted-V structures.

Marilia: brightness along REIMEI trajectory

COSPAR: current REIMEI study

Plan for exploring idea of secondaries

• SubkeV e- accelerated by parallel E?• E-field exists at some altitude• Distribution of secondary e- depends on altitude for <

around 600 km• Input primary, plasmasheet ~5keV precipitation• Model secondary e- distribution• Accelerated this modeled population through estimated

potential• Compare resulting secondary e- population to that

measured by ROPA• Can model secondary distribution for variety of altitudes• Are the subkeV e- really secondary/backscattered?• At what altitude is the acceleration region?