Mona Kessel, NASA HQ

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Science of NASAs Radiation Belt Storm Probes

• Mona Kessel, NASA HQ

Contributions by Jacob Bortnik, Seth
Claudepierre, Nicola Fox, Shri Kanekal, Kris
Kersten, Craig Kletzing, Lou Lanzerotti, Tony
Lui, Barry Mauk, Joe Mazur, Robyn Millan,
Geoff Reeves, David Sibeck, Sasha
Ukhorskiy, John Wygant
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Outline

• Short description of RBSP
• Mission
• Instruments

• Early Science Endeavors of RBSP
• EMFISIS
• EFW
• ECT
• RBSPICE
• RPS

• Coordinated Science
• BARREL
• THEMIS
• Theory Modeling

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The broad objectives of RBSP
Provide understanding, ideally to the point of
predictability, of how populations of
relativistic electrons and penetrating ions in
space form or change in response to variable
inputs of energy from the Sun.

• Which Physical Processes Produce Radiation Belt
  Enhancement Events?
• What Are the Dominant Mechanisms for Relativistic
  Electron Loss?
• How do Ring Current and other geomagnetic
  processes affect Radiation Belt Behavior?

The instruments on the two RBSP spacecraft will
measure the properties of charged particles that
comprise the Earths radiation belts and the
plasma waves that interact with them, the
large-scale electric fields that transport them,
and the magnetic field that guides them.
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Two spacecraft will target key radiation belt
regions with variable spacing

• 2 identically-instrumented spacecraft for
  space/time separation.
• Lapping rates (4-5 laps/year) for simultaneous
  observations over a range of s/c separations.

• 600 km perigee to 5.8 RE geocentric apogee for
  full radiation belts sampling.
• Orbital cadences faster than relevant magnetic
  storm time scales.
• 2-year mission for precession to all local time
  positions and interaction regions.
• Low inclination (10?) to access all magnetically
  trapped particles
• Sunward spin axis for full particle pitch angle
  and dawn-dusk electric field sampling.
• Space weather broadcast

Space Weather the White House
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Radiation Belt Storm Probes
Investigation Instruments PI
Energetic Particle Composition and Thermal Plasma Suite (ECT) Helium Oxygen Proton Electron Spectrometer (HOPE) Magnetic Electron Ion Spectrometer (MagEIS) Relativistic Electron Proton Telescope (REPT) H. Spence UNH
Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) Low-Frequency Magnetometer (MAG) High-Frequency Magnetometer and Waveform Receiver (Waves) C. Kletzing University of Iowa
Electric Field and Waves Instrument for the NASA RBSP Mission (EFW) Electric Field and Waves Instrument for the NASA RBSP Mission (EFW) J. Wygant University of Minnesota
Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) Radiation Belt Storm Probes Ion Composition Experiment (RBSPICE) L. Lanzerotti New Jersey Institute of Technology
Proton Spectrometer Belt Research (PSBR) Relativistic Proton Spectrometer (RPS) D. Byers NRO
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Comprehensive Particle Measurements
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Comprehensive E and B Field Measurements
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RBSP First Science Endeavors

1. What issues can be resolved about whistler mode
   interactions and their roles in electron
   energization and loss in the first 3 months?
2. What issues can be resolved about the large scale
   dynamics and structure with just the first few
   major geomagnetic storms?
3. What issues can be resolved about the source,
   structure, and dynamics of the inner (Llt2) ion
   and electron belts in the first 3 months?

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EMFISIS Science
Question 1
Understand correlations between various wave
modes using varying separations between the two
satellites. By start of normal operations (60
days after launch) the satellites should be well
separated.
Contribution by Craig Kletzing
Shprits et al., 2006
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Plasmaspheric Hiss 100Hz ? few kHz

• Confined primarily to high density regions
  plasmasphere, dayside drainage plumes.
• Generation mechanism not yet understood.

• At high frequency (gt1kHz) and low L source could
  be lightning
• At typical frequencies (few 100 Hz) source is
  likely magnetospheric

Shprits et al., 2006
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Plasmaspheric Hiss 100Hz ? few kHz

• Confined primarily to high density regions
  plasmasphere, dayside drainage plumes.
• Generation mechanism not yet understood.

• At high frequency (gt1kHz) and low L source could
  be lightning
• At typical frequencies (few 100 Hz) source is
  likely magnetospheric

Why do we care?
Hiss depletes the slot region by pitch angle
scattering.
Shprits et al., 2006
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Whistler mode Chorus 100Hz ? 5 kHz
Why do we care?
Capable of emptying the outer belt in a day or
less.
Major potential mechanism for electron
acceleration.
Shprits et al., 2006
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EFW Science
Question 1
Explore the connection between large amplitude
whistler waves and microburst precipitation.
Contribution by John Wygant, Kris Kersten
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• Santolik, et al. (2003) - first report of large
  amplitude chorus elements
• Lower band chorus (lt0.5fce) wave electric fields
  approaching 30mV/m

• Brief (lt1s) increases in the flux of
  precipitating MeV electrons, first satellite
  observations by Imhof, et al. (1992).

• Usually observed near dawn, but may extend from
  near midnight past dawn.
• Most commonly observed from L46.

Contribution by John Wygant, Kris Kersten
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EFW Science
Question 1
Explore the connection between large amplitude
whistler waves and microburst precipitation.
Microburst precipitation occurrence
Large Amplitude Whistler Occurrence
Lorentzen et al., 2001
Cully et al., 2008
Statistically the connection is strong.
Contribution by John Wygant, Kris Kersten
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ECT Science
Question 2
Why do the radiation belts respond so differently
to different storms?
Some geomagnetic storms can (a) Cause dramatic
radiation belt enhancement (b) Deplete radiation
belt fluxes (c) Cause no substantial effect of
flux distributions
(b)
(a)
(c)
Reeves et al., 2003
Contribution by Geoff Reeves
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ECT Science
Question 2
Identify the processes responsible for the
precipitation and loss of relativistic and near
relativistic particles, determine when and where
these processes occur, and determine their
relative significance.
Expected Electron Distributions
Quick Science Study Comparison of theory and
observations for characteristic signatures of
EMIC waves
Compare PSD as a function of E and PA during a
dropout.
2D Energy-pitch angle diffusion model at fixed L
Do observations show expected signatures?
Contribution by Geoff Reeves
Li et al., 2007
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RBSPICE Science
Question 2
If we have some geomagnetic storms during the
first few months of RBSP operation, then we can
address the following question.

• How is current density from protons, helium ions,
  and oxygen ions compared during weak and strong
  geomagnetic storms?

Energy density of oxygen ions can dominate that
of protons during intense geomagnetic storms
H
O
Hamilton et al., 1988
Contribution by Tony Lui
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RPS Science
Question 3
Discovery What is the energy spectrum of the
inner belt protons?
Few satellites have spent significant time near
the magnetic equator and at the peak intensities
of the inner belt.
Example of the wide variation in modeled inner
belt spectra
The dominant source for protons above 50 MeV in
the inner belt is the decay of albedo neutrons
from galactic cosmic ray protons that collide
with nuclei in the atmosphere and ionosphere
(Cosmic Ray Albedo Neutron Decay, or CRAND).

• Ion energy spectrum is known to extend beyond 1
  GeV, but the spectral details are not well
  established shape, maximum energy, time
  dependence
• Electron spectrum unknown. How do electrons get
  to the inner belt?

AP8 MIN Sayer Vette 1976 AD2005 Selesnick,
Looper, Mewaldt 2007
Contribution by Joe Mazur
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BARREL Mission
The proposed investigation will address the RBSP
goal of, "differentiating among competing
processes affecting precipitation and loss of
radiation particles" by directly measuring
precipitation during the RBSP mission.

• Launch 20 balloons each in January 2013 and
  January 2014 from Antarctica.
• BARREL will simultaneously measure precipitation
  over 8-10 hours of magnetic local time.
• Combine the measurements of precipitation with
  the RBSP spacecraft measurements of waves and
  energetic particles.

Contribution by Robyn Millan
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BARREL/RBSP Coordinated Science
Question 1
What is the loss rate due to precipitation versus
magnetopause losses?
Motivation Recent results of Turner et al., 2012
(magnetopause shadowing) vs earlier results from
e.g., Selesnick 2006, OBrien 2004
(precipitation).
Measurements

• RBSP measure changes in in-situ trapped electron
  intensity
• BARREL quantify precipitation at range of local
  times
• THEMIS magnetopause losses

Contribution by Robyn Millan
Figure courtesy of A. Ukhorskiy
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THEMIS/RBSP Coordinated Science
Question 2
First Planned Science Campaign Science Objectives

• What are the cause(s) of dawn-dusk differences in
  ion fluxes during geomagnetic storms?
• What role does the Kelvin-Helmholtz instability
  play in particle energization, transport, and
  loss?
• What are the relative roles of EMIC waves in the
  dusk magnetosphere, chorus waves in the dawn
  magnetosphere, and hiss deep within the
  magnetosphere?

THEMIS has 4-8-12 hours separation of the 3
satellites along the orbit.
Contribution by David Sibeck
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Question 1
Theory Simulation/RBSP Coordinated Science
Coincident observation of chorus and hiss on
THEMIS

• 1 inside plasmasphere, 1 outside plasmasphere
• Plasma wave instruments, recording simultaneously
• High resolution, correct frequency range
• Correct spatial regions, day side, equator
• Geomagnetic activity

Contribution by Jacob Bortnik
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Chorus - Hiss
Bortnik et al. 2009

• THEMIS-E discrete chorus, 600 Hz- 3 kHz, 0.2-0.5
  f/fce, y30-60

• THEMIS-D incoherent hiss, lt2 kHz

• Average spectral time-series, 1.2 1.6 kHz, high
  correlation!

Wave burst mode, 64-bin FFT, 20 Hz-4 kHz, every 1s
Contribution by Jacob Bortnik
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Numerical Ray tracing
Bortnik et al. 2008

• Ray trace all rays in allowable wave normal
  angles, Y
• Y -50 to -45, L6 waves reflect toward lower L
  and propagate into plasmasphere
• Timescale Y -48
• 1 s, enter plasmasphere,
• 2 s, 1st EQ crossing
• 3.2 s, magnetospheric reflection
• 7.7 s, second EQ crossing
• 20 s completely damped

Contribution by Jacob Bortnik
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Theory Simulation/RBSP Coordinated Science
Question 2
Effect of ULF waves on radiation belt electrons
Measurements

• ECT measure changes in in-situ trapped electron
  intensity
• EMFISIS measure magnetic field (FFT to generate
  ULF wave power)

Simulation

• Global MHD (LFM) simulate magnetospheric ULF
  waves driven by dynamic pressure fluctuations

Theory Modeling

• Radial Diffusion transport elecrons across
  drift shells

Contributions by Seth Claudepierre Sasha
Ukhorskiy
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Pressure fluctuations In High Speed Stream
excite magnetosphere (Pc 5 frequency range)
Kessel, 2007
Contribution by Mona Kessel
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LFM Simulation Driving frequency 10 mHz
Solar wind dynamic pressure fluctuations can
drive compressional ULF waves on the dayside
Contribution by Seth Claudepierre
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Solar Wind driven ULF waves lead to
non-diffusive transport
Non-diffusive Transport
Radial transport in MHD field model dominated by
drift resonant interactions, each producing large
coherent displacement of the distribution.
Radial transport across the outer belt can be
driven by a variety of ULF waves induced by SW
and ring current instabilities. Transport
exhibits large deviations from radial diffusion,
which may account for the observed nonlinear
response of electron fluxes to geomagnetic
activity even similar storms can produce vastly
different radiation levels across the belt .
Contribution by Sasha Ukhorskiy
Ukhorskiy 2009
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RBSP launch Aug 23, 2012
RBSP team and the science community ready to get
the data and change the theories.
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