Van Allen Probes: Where We’ve Been and Where
We’re Going
Seth G. Claudepierre
The Aerospace Corporation
seth@aero.org
© 2015 The Aerospace Corporation
Funding Acknowledgment:
NASA Contract # NAS5-01072.
Outline
•
Van Allen Probes mission summary.
•
Van Allen Probes science.
•
Mission highlights.
•
Extended mission.
•
Van Allen Probes
Summary.
(credit: JHU/APL, NASA)
(credit: JHU/APL)
450 keV e-
The focus of this talk will be on Van Allen Probes observations.
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seth@aero.org
Van Allen Probes Mission
Science Questions
(credit: JHU/APL)
GTO orbit: 1.1 X 5.8 RE, 10○, T ~ 9 hrs
Package
Measurement
ECT
electrons and ions (particles)
EFW
electric and magnetic fields (waves)
EMFISIS
electric and magnetic fields (waves)
RBSPICE electrons and ions (particles)
RPS
protons (particles)
1. Which physical processes produce
radiation belt enhancements?
2. What are the dominant mechanisms for
relativistic electron loss?
3. How do ring current and other
geomagnetic processes affect radiation
belt behavior?
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Van Allen Probes Mission
Particle Instrumentation
(credit: JHU/APL)
Package
PI
ECT
Harlan Spence, UNH
ECT/HOPE
Herb Funsten, LANL
ECT/MagEIS Bern Blake, Aerospace
(Mauk et al., SSR, [2012])
ECT/REPT
Dan Baker, UC Boulder
RBSPICE
Lou Lanzerotti, NJIT
RPS
Joe Mazur, Aerospace
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(Stratton et al., SSR, [2013])
Van Allen Probes Mission
Fields and Waves Instrumentation
(credit: JHU/APL)
Package
PI
EFW
John Wygant, U Minnesota
EMFISIS
Craig Kletzing, U Iowa
(Mauk et al., SSR, [2012])
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(Stratton et al., SSR, [2013])
Van Allen Probes Mission
Timeline
(credit: JHU/APL)
• 2012 Aug 30: Launch
• 2012 Nov 01: Prime Mission Start
• 2014 Oct 31: Prime Mission End
• 2014 Nov 01: Bridge Phase Begin
• 2015 Oct 31: Bridge Phase End
• 2015 Nov 01: ?Extended Mission Begin?
PRIME
BRIDGE
450 keV e-
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Van Allen Probes Mission
Radiation Belt Science
(credit: JHU/APL)
Enhancement (53%)
Loss (19%)
No Change (28%)
(Reeves et al., GRL, [2003])
“The effect of geomagnetic storms on radiation belt fluxes are a
delicate and complicated balance between the effects of particle
acceleration and loss.” --Reeves et al., GRL [2003]
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Van Allen Probes Mission
Radiation Belt Dynamics
(credit: JHU/APL)
Adiabatic Invariants: (μ, K, L*)
• Gyro (μ): ~10-3 sec (kHz)
• Bounce (K): ~100 sec (Hz)
• Grad./Curv. Drift (L*): ~103
sec (mHz)
Flux
A. Non-adiabatic Transport:
One or more of (μ, K, L*) is
violated.
B. Adiabatic Transport:
μ, K, L* are all conserved.
Converting flux(E, α, L) → PSD(μ, K, L*) removes adiabatic effects
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PSD
Van Allen Probes Mission
Radiation Belt Dynamics
(credit: JHU/APL)
Adiabatic Invariants: (μ, K, L*)
• Gyro (μ): ~10-3 sec (kHz)
• Bounce (K): ~100 sec (Hz)
• Grad./Curv. Drift (L*): ~103 sec (mHz)
A. Non-adiabatic Transport: One or more of (μ, K, L*) is violated.
I. Radial Transport: μ, K conserved; L* violated.
II. Local Acceleration: μ violated; K, L* necessarily violated.
B. Adiabatic Transport: μ, K, L* are all conserved.
• Adiabatic acceleration:
1. Betatron acceleration.
2. Fermi acceleration.
Green et al., JGR, [2004]
What are the observational signatures of these processes?
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seth@aero.org
Van Allen Probes Mission
Radiation Belt Dynamics
(credit: JHU/APL)
Adiabatic Invariants: (μ, K, L*)
• Gyro (μ): ~10-3 sec (kHz)
• Bounce (K): ~100 sec (Hz)
• Grad./Curv. Drift (L*): ~103 sec (mHz)
A. Non-adiabatic Transport: One or more of (μ, K, L*) is violated.
I. Radial Transport: μ, K conserved; L* violated.
a) Drift-resonance with monochromatic ULF waves.
b) Impulsive events.
c) Radial diffusion.
II. Local Acceleration: μ violated; K, L* necessarily violated.
B. Adiabatic Transport: μ, K, L* are all conserved.
• Adiabatic acceleration:
1. Betatron acceleration.
2. Fermi acceleration.
• Converting flux(E, α, L) → PSD(μ, K, L*) removes adiabatic effects.
Green et al., JGR, [2004]
What are the observational signatures of these processes?
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seth@aero.org
Van Allen Probes Mission
Radiation Belt Dynamics
(credit: JHU/APL)
Adiabatic Invariants: (μ, K, L*)
• Gyro (μ): ~10-3 sec (kHz)
• Bounce (K): ~100 sec (Hz)
• Grad./Curv. Drift (L*): ~103 sec (mHz)
A. Non-adiabatic Transport: One or more of (μ, K, L*) is violated.
I. Radial Transport: μ, K conserved; L* violated.
a) Drift-resonance with monochromatic ULF waves.
b) Impulsive events.
c) Radial diffusion.
II. Local Acceleration: μ violated; K, L* necessarily violated.
• Resonant wave-particle interactions with high frequency waves.
• e.g. gyroresonance between electrons and VLF chorus.
B. Adiabatic Transport: μ, K, L* are all conserved.
• Adiabatic acceleration:
1. Betatron acceleration.
2. Fermi acceleration.
• Converting flux(E, α, L) → PSD(μ, K, L*) removes adiabatic effects.
Green et al., JGR, [2004]
What are the observational signatures of these processes?
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seth@aero.org
Van Allen Probes Mission
Radiation Belt Dynamics: Loss
(credit: JHU/APL)
1. Adiabatic “Loss”/Dst effect:
Electrons move radially outward due to
ring current growth and diamagnetic
effect.
2. Non-adiabatic Loss
𝐿~
1
Φ
Kim and Chan, JGR, [1997]
What are the observational signatures of these processes?
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seth@aero.org
Van Allen Probes Mission
Radiation Belt Dynamics: Loss
(credit: JHU/APL)
1. Adiabatic “Loss”/Dst effect:
Electrons move radially
outward due to ring current
growth and diamagnetic effect.
(credit: Chia-Lin Huang)
2. Non-adiabatic Loss
a) Magnetopause shadowing.
Morley et al., PRSA, [2010]
MPShue
~350 keV e-
• Can explain rapid main phase dropouts.
• ULF-enhanced outward radial transport.
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What are the observational signatures of these
processes?
seth@aero.org
Van Allen Probes Mission
Radiation Belt Dynamics: Loss
Li et al., JGR, [2014]
1. Adiabatic “Loss”/Dst effect:
Electrons move radially outward due to
ring current growth and diamagnetic
effect.
2. Non-adiabatic Loss
a) Magnetopause shadowing.
• Can explain rapid main phase
dropouts.
• ULF-enhanced outward radial
diffusion.
b) Precipitation (resonant scattering via
WPI).
• Hiss scattering (most effective at
α = 90○).
• 10s keV in ~1 day
• 100s keV in ~10 days
• >MeV in weeks
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What are the observational signatures of these
processes?
seth@aero.org
(credit: JHU/APL)
Van Allen Probes Mission
Radiation Belt Dynamics: Loss
Li et al., JGR, [2014]
Adiabatic “Loss”/Dst effect: Electrons move radially
outward due to ring current growth and diamagnetic
effect.
2. Non-adiabatic Loss
a) Magnetopause shadowing.
• Can explain rapid main phase dropouts.
• ULF-enhanced outward radial diffusion.
b) Precipitation (resonant scattering via WPI).
• Hiss scattering (most effective at α = 90○).
• 10s keV in ~1 day
• 100s keV in ~10 days
• >MeV in weeks
• EMIC scattering
• Most effective >MeV, low pitch angles
• Loss times ~hours
• Can explain sudden losses of multi-MeV
electrons mirroring far off the equator
• Other scattering (chorus, magnetosonic,
bands/spikes, microbursts)
• Low altitude measurements critical (e.g.,
BARREL, POES, CubeSats).
1.
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What are the observational signatures of these
processes?
seth@aero.org
(credit: JHU/APL)
Van Allen Probes Mission
Radiation Belt Dynamics: Loss
Li et al., JGR, [2014]
1. Adiabatic “Loss”/Dst effect: Electrons move
radially outward due to ring current growth and
diamagnetic effect.
2. Non-adiabatic Loss
a) Magnetopause shadowing.
• Can explain rapid main phase dropouts.
• ULF-enhanced outward radial diffusion.
b) Precipitation (resonant scattering via WPI).
• Hiss scattering (most effective at α = 90○).
• EMIC scattering
• Other scattering (chorus, magnetosonic,
bands/spikes, microbursts)
• Low altitude measurements critical (e.g.,
BARREL , POES, CubeSats).
c) Drift-orbit expansion (L* violated, due to rapid
ring current growth and diamagnetic effect).
d) Drift-orbit bifurcation (K violated, leading to rapid
radial transport to MP).
16
What are the observational signatures of these
processes?
seth@aero.org
(credit: JHU/APL)
Van Allen Probes Mission
Where We’ve Been and Where We’re Going
(credit: JHU/APL)
Mission Highlights
• High profile discoveries/observations.
• Direct observations of wave-particle interactions.
• Potpourri
•
The role of the source/seed population.
•
“Time domain structures.”
•
Unexpected features in the inner zone.
•
Chorus as the source of hiss.
Extended Mission
• New phase of solar cycle.
• Orbital evolution.
• Science goals.
• Coordination with other observational assets.
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seth@aero.org
Mission Highlights
Remnant Outer Electron Belts
(credit: JHU/APL)
• Dual-belt outer-zone structure at
ultra-relativistic energies.
3.4 MeV
• Results from loss over a large
portion (but not the entirety) of
the outer zone, followed by
energization at higher L.
5.2 MeV
• Remnant belt at L=3 largely
unaffected by processes that
modulate the outer belt at L=4-6.
7.7 MeV
• Note that the “formation” of the
remnant belt is due to loss, and
not a fresh, localized injection
(e.g., March 1991).
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Baker et al., Science [2012]
Mission Highlights
Remnant Outer Electron Belts
(credit: JHU/APL)
3.4 MeV
• Many similar examples in the Van
Allen Probes era.
• Appear to form under similar
circumstances: loss over a large
portion of the outer zone,
followed by energization at
higher L.
5.2 MeV
7.7 MeV
• Ultra-relativistic particle lifetimes
are very long inside the
plasmasphere.
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seth@aero.org
Mission Highlights
Remnant Outer Electron Belts
(credit: JHU/APL)
3.4 MeV
• Many similar examples in the Van
Allen Probes era.
• Appear to form under similar
circumstances: loss over a large
portion of the outer zone,
followed by energization at
higher L.
5.2 MeV
7.7 MeV
• Ultra-relativistic particle lifetimes
are very long inside the
plasmasphere.
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seth@aero.org
Mission Highlights
Clear Evidence of Growing Peaks in Phase Space Density
(credit: JHU/APL)
Reeves et al., Science [2013]
Green et al., JGR, [2004]
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Mission Highlights
Clear Evidence of Growing Peaks in Phase Space Density
Li et al., JGR [2014]
See also Boyd et al., GRL [2014], Foster et al., GRL [2014]
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(credit: JHU/APL)
Mission Highlights
Discovery of Inner Zone “Zebra Stripes”
(credit: JHU/APL)
• Highly structured patterns
in inner zone electron
fluxes.
• Observed regularly and
during all levels of
geomagnetic activity.
• Earth’s rotation induces
global diurnal variations in
electric and magnetic field.
• These fields drift-resonate
with inner belt electrons to
produce the observed
patterns.
Ukhorskiy et al., Nature [2014]
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Mission Highlights
Sharp Gradient at the Inner Edge of the Outer Belt
(credit: JHU/APL)
• Relativistic and ultrarelativistic electrons have not
penetrated L=2.8 in the Van
Allen Probes era.
• Very stable boundary that is
independent of activity.
• Likely results from the fact
that weak scattering losses
are dominant over even
weaker radial diffusion
transport.
• The gradient in flux versus L
is steeper/sharper at higher
electron energies.
Baker et al., Nature [2014]
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seth@aero.org
Van Allen Probes Mission
Where We’ve Been and Where We’re Going
(credit: JHU/APL)
Mission Highlights
• High profile discoveries/observations.
• Direct observations of wave-particle interactions.
• Potpourri
•
The role of the source/seed population.
•
“Time domain structures.”
•
Unexpected features in the inner zone.
•
Chorus as the source of hiss.
Extended Mission
• New phase of solar cycle.
• Orbital evolution.
• Science goals.
• Coordination with other observational assets.
25
seth@aero.org
Mission Highlights
Direct Evidence of Wave-Particle Interactions: ULF Waves
•
Residual flux oscillations clearly show:
1) Oscillation amplitude peak at ~60
keV.
2) 180 degree phase change across
the amplitude peak.
•
Signature of a drift-resonant interaction
between the electrons and
magnetospheric ULF waves.
•
The ULF wave is identified as the
fundamental poloidal mode.
•
Many similar cases in Van Allen Probes
(Dai et al, [2013] GRL; Foster et al.,
[2015] JGR; Hao et al., [2014] JGR).
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Claudepierre
et al., GRL [2013]
seth@aero.org
Mission Highlights
Direct Evidence of Wave-Particle Interactions: Chorus Waves
(credit: JHU/APL)
~20 keV electron flux bursts
coincident with upper-band
chorus wavebursts.
Following a plasma injection
postmidnight (~3 MLT).
Observed outside of the
plasmasphere by both Van Allen
Probes.
Eres estimated to be 15–35 keV
(from ne, fce, α).
Quasiperiodic nature (~minutes)
of the bursts is not understood.
Fennell et al., GRL [2014]
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Mission Highlights
Direct Evidence of Wave-Particle Interactions: Hiss Waves
(credit: JHU/APL)
Breneman et al., Nature [2015]
Simultaneous measurements of
structured radiation belt
electron losses and the hiss
phenomenon that causes the
losses.
Following a plasma injection
into the afternoon sector
plasmasphere.
Loss dynamics and hiss
dynamics are coherent over
large spatial scales (Van
Allen/BARREL separations ~3.5
L and ~6 hrs MLT).
ULF fluctuations in density and
magnetic field facilitate the loss
process by creating conditions
favorable for the growth of hiss
waves.
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seth@aero.org
Mission Highlights
Direct Evidence of Wave-Particle Interactions: EMIC Waves
(credit: JHU/APL)
Loss of relativistic/ultrarelativistic electrons
via pitch-angle scattering by EMIC waves.
Recovery phase of a moderate storm (11
October 2012).
EMIC waves observed in situ (Van Allen
Probes) and conjugately on the ground
(CARISMA).
Reductions in electron flux at 90° pitch
angle were not observed.
Computed pitch angle diffusion rates
demonstrate that rapid pitch angle diffusion
is confined to low-pitch angles (< 45°) and
cannot reach 90°.
seth@aero.org
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Usanova
et al., GRL [2014]
Mission Highlights
Direct Evidence of Wave-Particle Interactions: EMIC Waves
(credit: JHU/APL)
seth@aero.org
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Usanova
et al., GRL [2014]
Van Allen Probes Mission
Where We’ve Been and Where We’re Going
(credit: JHU/APL)
Mission Highlights
• High profile discoveries/observations.
• Direct observations of wave-particle interactions.
• Potpourri
•
The role of the source/seed population.
•
“Time domain structures.”
•
Unexpected features in the inner zone.
•
Chorus as the source of hiss.
Extended Mission
• New phase of solar cycle.
• Orbital evolution.
• Science goals.
• Coordination with other observational assets.
31
seth@aero.org
Mission Highlights
The Role of the Seed/Source Population
(credit: JHU/APL)
(E ~ 200 keV)
(E ~ 1.5 MeV)
“Source” (10s keV)
-> wave growth (e.g., chorus)
“Seed” (100s keV)
-> accelerated to >1 MeV
S’ward
IMF
Boyd et al., in preparation
seth@aero.org
32
substorm injections
(source – 10s keV)
chorus waves
substorm injections
(seed – 100s keV)
MeV electrons
Mission Highlights
The Role of the Seed/Source Population
(credit: JHU/APL)
GOES showed an extended (~10 days),
and rather unexpected, anti-correlation
of solar wind speed with GEO
relativistic electron fluxes (not shown).
S’ward
IMF
substorm injections
(source – 10s keV)
chorus waves
substorm injections
(seed – 100s keV)
MeV electrons
Jaynes et al., JGR [2015]
seth@aero.org
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Mission Highlights
The Role of the Seed/Source Population
(credit: JHU/APL)
Chorus wave activity inferred
from POES
S’ward
IMF
substorm injections
(source – 10s keV)
chorus waves
substorm injections
(seed – 100s keV)
MeV electrons
Jaynes et al., JGR, in review
seth@aero.org
34
Mission Highlights
The Role of the Seed/Source Population
(credit: JHU/APL)
S’ward
IMF
substorm injections
(source – 10s keV)
chorus waves
substorm injections
(seed – 100s keV)
MeV electrons
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seth@aero.org
Jaynes et al., JGR, in review
Mission Highlights
The Abundance of “Time-Domain Structures”
(credit: JHU/APL)
Mozer et al., GRL [2015]
• Intense electric field spikes,
duration >1 ms.
• Significant parallel electric field.
• Associated with plasma injections.
• At least 5 different types
observed:
electrostatic/electromagnetic
double layers,
electrostatic/electromagnetic
electron holes, nonlinear
whistlers.
• May be associated with
production of seed electrons
and/or electron precipitation.
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seth@aero.org
Mission Highlights
Unexpected Features in the Inner Zone (1)
(credit: JHU/APL)
Fennell et al., GRL [2015]
MagEIS does not detect any MeV
electrons in the inner zone.
AE9 inaccurate in the inner zone.
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seth@aero.org
Mission Highlights
Unexpected Features in the Inner Zone (2)
(credit: JHU/APL)
Turner et al., GRL [2015]
•
47 substorm-related electron injections
to very low L (L<4, Lmin=2.5).
•
First nightside season of Van Allen
Probes (2012 Dec to 2013 Sep).
•
All observed at <250 keV.
•
Important source for inner zone.
450 keV e-
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Mission Highlights
Unexpected Features in the Inner Zone (3)
(credit: JHU/APL)
3 Types of Pitch-Angle Distributions Identified (L<4)
Normal
Cap
90 min
•
Pitch-angle distributions with
flux minimum at 90 degrees
regularly observed in the
inner zone.
•
“Cap” PADs likely caused
due to pitch-angle scattering
via hiss waves.
•
90 degree minimum PADs
currently lack satisfactory
theoretical explanation.
Zhao et al., GRL [2014]
Zhao et al., JGR [2015]
seth@aero.org
ECT/MagEIS 450 keV electrons
39
Mission Highlights
Intriguing Relationship Between Chorus and Hiss
(credit: JHU/APL)
Li et al., GRL [2015]
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seth@aero.org
•
Chorus as the source of
hiss?
•
Chorus observed at high L
(~9.8).
•
Coordinated campaign
between THEMIS and Van
Allen Probes.
Van Allen Probes Mission
Where We’ve Been and Where We’re Going
(credit: JHU/APL)
Mission Highlights
• High profile discoveries/observations.
• Direct observations of wave-particle interactions.
• Potpourri
•
The role of the source/seed population.
•
“Time domain structures.”
•
Unexpected features in the inner zone.
•
Chorus as the source of hiss.
Extended Mission
• New phase of solar cycle.
• Orbital evolution.
• Science goals.
• Coordination with other observational assets.
41
seth@aero.org
Extended Mission
New Solar Cycle Phase
(credit: JHU/APL)
Li et al., JGR [2011]
“Quantify the processes governing the Earth’s radiation belt and ring
current environment as the solar cycle transitions from solar maximum
through the declining phase.”
[Van Allen Probes extended mission proposal, B. H. Mauk]
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Extended Mission
New Solar Cycle Phase
(credit: JHU/APL)
~2019?
(credit: NASA MSFC)
seth@aero.org
1995
43
2007
Extended Mission
End of Life
(credit: JHU/APL)
Van Allen Probes Prime
Bridge
Extended
End of Life
Probe A: 2019-May ± 3 months
Probe B: 2019-Jun ± 3 months
~2019?
(credit: NASA MSFC)
seth@aero.org
1995
44
2007
Extended Mission
End of Life (EOL)
(credit: JHU/APL)
Van Allen Probes Prime
Bridge
Extended
EOL (no change)
EOL (separate)
A: 2019-May ± 3 mo.
B: 2019-Jun ± 3 mo.
A: 2019-Feb ± 3 mo.
B: 2019-Mar ± 3 mo.
2018-Jun
~2019?
(credit: NASA MSFC)
seth@aero.org
1995
45
2007
2018-Jun
Extended Mission
End of Life (EOL)
(credit: JHU/APL)
Van Allen Probes Prime
Bridge
Extended
EOL (no change)
EOL (separate)
A: 2019-May ± 3 mo.
B: 2019-Jun ± 3 mo.
A: 2019-Feb ± 3 mo.
B: 2019-Mar ± 3 mo.
2018-Jun
2018-Jun
• Lapping rate: 76 days → 24 days.
• Large increase in radial conjunctions.
(credit: NASA MSFC)
seth@aero.org
1995
46
2007
Foster et al., JGR [2015]
Extended Mission
Science Goals
Particle acceleration
• The relative roles of local versus transport
mechanisms.
• The role that nonlinear mechanisms play in
the acceleration processes.
Hudson et al., JGR [2015]
Particle loss
• The relative importance of precipitation and
magnetopause losses.
• More definitive information about the causes
and consequences of precipitation.
Gkioulidou et al., JGR [2014]
Injections
• The relative roles of global-scale transport
processes and mesoscale dynamic
injections.
• Their respective roles in the production of
geoeffective waves.
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Extended Mission
Coordination with Other Observational Assets
(credit: JHU/APL)
• Burst mode coordination and campaigns
• High activity levels
• Wave-growth
• Close approaches
• Additional assets:
• THEMIS, Cluster, ACE/DSCOVR
• MMS
• ERG
• DSX
• CubeSats (CeREs, FIREBIRD,
AeroCube, ELFIN)
• Ground (SuperDARN, imagers,
riometers, SuperMAG, HAARP)
• BARREL
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seth@aero.org
Summary
Van Allen Probes Mission: Where We’ve Been and Where We’re Going
(credit: JHU/APL)
• New, intriguing observations and discoveries,
some of which will require new/modified
theory and modeling.
• A growing number of clear observations of
direct wave-particle interactions: ULF, chorus,
hiss, EMIC, and magnetosonic.
• Opportunities for new science in the next
phase of the solar cycle.
• A truly impressive fleet of spacecraft and
instrumentation to observe the coupled
geospace system.
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