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Barry Mauk,

Nicola Fox, David Sibeck,

Shrikanth Kanekal, Joseph Grebowsky, Ramona Kessel

RBSP Project Science Team

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Untangling complex processes within Earth’s radiation belts with the Radiation

Belt Storm Probes (RBSP) mission.

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The RBSP Mission is designed to:

• Impacts:

1. Understand fundamental radiation processes operating throughout the universe.

2. Understand Earth’s radiation belts and related regions that pose hazards to human and robotic explorers.

• Objective:

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.

Intensities of Earth’s dynamic radiation belts

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We have learned much about radiation belt physics but substantial & important mysteries remain

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Two types of RBSP Goals

• Better understand individual transport and energization mechanisms

– Understand the extent to which non-linearities modify the role that whistler mode waves play in exchanging energy with and scattering radiation belt electrons.

• Untangling complex processes: Better understand how these mechanisms act together to yield the complex behaviors that are observed.

– What is the relationship between processes that supply electron source populations and those that generate the Ultra Low Frequency waves that can help transport those particles? 

– What is the role of substorm injections in creating or modifying the global electric fields that transport and redistribute the injected plasma populations?

– How dependent is the wave activity that energizes radiation belt electrons on the global electric field that creates the conditions for wave generation?

5Mauk & McPherron, Phys. Fluids,1980

Example: What is the importance of EMIC waves

in the control (loss) of radiation belt particles?

Courtesy:A. (Sasha)Ukhorskiy

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It has been proposed that increases in helium concentrations stimulates EMIC wave generation

Young et al., 1981; Roux et al., Rauch et al., 1982

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Wave modifications are so profound that mass composition cannot be confidently determined

Mauk and McIlwain, JGR, 1993 Mauk & McPherron, Phys. Fluids,1980

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Global magnetosheric structure and transport generate the conditions for EMIC wave generation

Global convection likely plays a key role

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But, we remain profoundly ignorant of the configuration and dynamic of convective fields

Hori et al. 2005

Rowland & Wygant, 1998

1010Kivelson et al. 1979

Mauk and Meng, 1983a

Dynamic injections appear required to explain the transport

needed to population the regions of EMIC generation

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Understanding the importance of EMIC wave control or radiation belts requires:

• Improved understanding of the microphysics of wave generate.

• Improved understanding of the global electromagnetic transport processes to understand how the conditions for wave generation are created.

• Untangling complex processes within Earth’s radiation belts

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What is required to untangle complex processes?

• Simultaneous, multipoint sampling at various spatial scales reveals source and evolution of critical features.

• High quality, integrated measurements are needed to target key processes.

Lui et al., 1986300 MeV/Gauss Oxygen

3 4 5 6 7 8 9L (RE)

4

2

0

-2Lo

g [P

hase

Spa

ce D

ensi

ty]

(s

3 /km

6 )

T1

T1+31 hrs

Did this feature form locally or was it

transported Earthward?

Understandable motion

Mysterious “peak”

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Sun

• 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

Multiple spacecraft must target key radiation belt regions with variable spacing

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RBSP has unusually comprehensive particle and fields instrument measurement capabilities

electrons

protons

1eV 1keV 1MeV 1GeV

ioncomposition

Energy

DC Magnetic

DC Electric

AC Magnetic

~DC 10Hz 1kHz 1MHz

AC Electric

Frequency

Particle SensorsPSBR/RPSECT/REPT

ECT/MagEISRBSPICE

ECT/HOPE

Fields & WavesSensors

EMFISIS/MAGEMFISIS/Waves

EFW

HOPE

RBSPICE

RPS

MagEIS

REPT

EMFISIS FGM

EFW Perp 2DEFW Par 1D

EMFISIS WavesEFW E-field Spectra

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Coordinating RBSP with other missions helps greatly to untangle processes: Example: Themis

Courtesy of Sibeck & Ukhorskiy

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RBSP resolves important & universal science questions that have practical consequences

• RBSP advances NASA’s Strategic Plan and Heliospheric Science Objectives:– Fundamental science. – Determining effects of solar variability on technological systems. – Developing ability to predict extreme & dynamic space conditions.

• Much has been learned about radiation belt physics but our ignorance is profound in some areas:– Text book predictions about key observations are wrong.– Radiation belt dynamics is not understood.– Untangling the interaction of complex processes is needed.

• RBSP provides the needed multi-point sampling and integrated measurements to make transformational advances in understanding.

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