Loss Processes
D. Sibeck, R. Millan, H. Spence
Outline
• 1. Quantify magnetopause losses
– Magnetopause motion and shell splitting
– ULF waves
– Orbit bifurcation
– Ring current inflation
• 2. Quantify precipitation mechanisms
• 3. Quantify relative importance over solar
cycle
Losses and Magnetopause Motion
• Compression
• Rapid (1-2 min) increase in dayside field strengths
(betatron acceleration and flux increase),
• Gradual decrease in nightside equatorial field strengths
• Enhanced drift shell splitting
• 90° pitch angle particles on closed paths gain access to
magnetopause and are lost from outer magnetosphere.
Losses and Magnetopause Motion
• Causes of Magnetopause Motion
– Erosion (requires 30-60 minutes)
• No change in subsolar magnetic field strength
therefore no opening of drift paths.
• R1 currents gradually diminish dayside field strengths
while cross-tail currents gradually reduce nightside
equatorial magnetic field strengths 
• High energy 90° pitch angle particles conserve 1st ad.
inv. and move inward, low energy particles also
conserve 3rd ad. inv. and move outward, lose energy
but may not be lost to the magnetosphere.
Diffusion Driven By ULF Waves
• Diffusion resulting from ULF (and other) waves
requires
– ~1 hr [Shprits et al., 2006]
– days [Morley et al., 2010]
to remove electrons
from locations deep in
the magnetosphere. May
need some other process to
help [Ukhorskiy et al., 2009]
Bifurcation Enhanced Diffusion
• 1 MeV electrons at 4 times. Bifurcation moves
electrons both outwards to MP and inwards
Ring Current Inflation
Removes
Electrons
Ukhorskiy et al. [2015]
With ring current
Without ring current
1.25-1.5 MeV e 90° P. A.
P.A.
# Particles
Drift echoes
Adiabatic Cooling
Compressional
Energization
Tasks
• 1. Survey radiation belt responses to abrupt solar
wind pressure and IMF Bz variations.
• 2. Survey ULF wave activity and cf. radiation belt
behavior.
• 3. Look for enhanced losses on field lines subject
to bifurcation.
• 4. Look for ring current effects on loss from inner
magnetosphere.
• 5. Use MMS/THEMIS to survey losses at the
magnetopause, cf. with particle loss deeper in the
magnetosphere.
Quantify Precipitation Mechanisms
• 1. Quantify extent, significance of
– EMIC waves [Halford et al., 2010; Usanova et al.,
2014; Kersten et al., 2014].
– Chorus [Thorne et al., 2010]
not only as function of geomagnetic
indices or solar wind conditions, but of
storm phase.
• 2. Compare with precipitation patterns
(cubesats, BARREL).
Solar Cycle Variations
• More substorms and particle injections during
declining phase of solar cycle 
• More chorus waves 
• More particle loss?
• Work with MMS/ERG/THEMIS to determine
extent of wave fields, rate of loss, cf.
observations, compare at different stages of
solar cycle.