Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
239
9.5.2 Missions
One of the central elements in a robust program of scientific research in solar wind-magnetosphere
interactions must be an ongoing sequence of strategic missions obtaining in-space measurements targeted
at the highest-priority science objectives. Identification of new mission concepts to address the SWMI science objectives is an important element of this decadal survey. These new missions and the science they
address must be considered against the backdrop of accomplishments from past missions, as well as the
science that will be addressed by missions that are currently in development and missions that are still
operating. Below, the SWMI panel reviews expectations from missions currently under development or
still operating and considers the central role played by Explorers, PI-led missions that afford the maximum
agility in identifying new and exciting science. The panel then presents the new strategic mission concepts
that it found particularly compelling. Finally, some promising concepts are mentioned that will require
significant development efforts in the coming decade to enable their application to the outstanding SWMI
science problems of the future.
9.5.2.1 Missions Under Development
MMS
The Magnetospheric Multiscale Mission currently under development is designed to address key parts
of SWMI critical science goal 5, to “discover how magnetic reconnection is triggered and modulated.”
Earth’s magnetosphere provides one of the few opportunities to observe magnetic reconnection with in
situ measurements. Specifically, MMS will focus on the kinetic microphysics of magnetic reconnection
that occurs in tiny boundary layers at electron scales. Measuring these boundary layers requires multiple
spacecraft with unprecedented spatial and temporal resolution. MMS is poised to provide the first glimpse
of these electron layers and continues to be a high science priority for the coming decade.
RBSP/BARREL
The Radiation Belt Storm Probes mission currently in development directly addresses this decade’s
SWMI critical science goal 4, to “establish how energetic particles are accelerated, transported, and lost.”
To do so, RBSP’s mission objectives are threefold: (1) to discover the relative importance of various candidate mechanisms and when and where they act to accelerate and transport electrons and ions; (2) to
quantify the balance between competing acceleration and loss mechanisms that determine time-varying
radiation belt intensity and spatial distribution; and (3) to understand—to the point of predictability—how
the radiation belts change dynamically. The instruments on the two RBSP spacecraft will provide the measurements needed to characterize and quantify the processes that produce relativistic ions and electrons.
They will measure the properties of charged particles that comprise Earth’s 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, all of which are required to develop a predictive understanding of radiation belt dynamics.
The mission promises to make breakthrough discoveries and to rewrite the textbook on universal planetary
radiation belt physics.
Over the past decade, the importance of relativistic electron losses from Earth’s radiation belts has also
become increasingly clear. There is evidence that the radiation belts are emptied during the main phase
of geomagnetic storms before being refilled by newly accelerated particles. However, the relative importance of atmospheric precipitation losses versus magnetopause losses is not known, and the processes that
scatter relativistic particles into the atmosphere have not been experimentally validated. BARREL (Balloon
Array for RBSP Relativistic Electron Losses) will augment RBSP by providing a low-altitude component to
quantify electron precipitation. BARREL consists of several balloon campaigns during which an array of
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON SOLAR WIND-MAGNETOSPHERE INTERACTIONS
239
9.5.2 Missions
One of the central elements in a robust program of scientific research in solar wind-magnetosphere
interactions must be an ongoing sequence of strategic missions obtaining in-space measurements targeted
at the highest-priority science objectives. Identification of new mission concepts to address the SWMI science objectives is an important element of this decadal survey. These new missions and the science they
address must be considered against the backdrop of accomplishments from past missions, as well as the
science that will be addressed by missions that are currently in development and missions that are still
operating. Below, the SWMI panel reviews expectations from missions currently under development or
still operating and considers the central role played by Explorers, PI-led missions that afford the maximum
agility in identifying new and exciting science. The panel then presents the new strategic mission concepts
that it found particularly compelling. Finally, some promising concepts are mentioned that will require
significant development efforts in the coming decade to enable their application to the outstanding SWMI
science problems of the future.
9.5.2.1 Missions Under Development
MMS
The Magnetospheric Multiscale Mission currently under development is designed to address key parts
of SWMI critical science goal 5, to “discover how magnetic reconnection is triggered and modulated.”
Earth’s magnetosphere provides one of the few opportunities to observe magnetic reconnection with in
situ measurements. Specifically, MMS will focus on the kinetic microphysics of magnetic reconnection
that occurs in tiny boundary layers at electron scales. Measuring these boundary layers requires multiple
spacecraft with unprecedented spatial and temporal resolution. MMS is poised to provide the first glimpse
of these electron layers and continues to be a high science priority for the coming decade.
RBSP/BARREL
The Radiation Belt Storm Probes mission currently in development directly addresses this decade’s
SWMI critical science goal 4, to “establish how energetic particles are accelerated, transported, and lost.”
To do so, RBSP’s mission objectives are threefold: (1) to discover the relative importance of various candidate mechanisms and when and where they act to accelerate and transport electrons and ions; (2) to
quantify the balance between competing acceleration and loss mechanisms that determine time-varying
radiation belt intensity and spatial distribution; and (3) to understand—to the point of predictability—how
the radiation belts change dynamically. The instruments on the two RBSP spacecraft will provide the measurements needed to characterize and quantify the processes that produce relativistic ions and electrons.
They will measure the properties of charged particles that comprise Earth’s 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, all of which are required to develop a predictive understanding of radiation belt dynamics.
The mission promises to make breakthrough discoveries and to rewrite the textbook on universal planetary
radiation belt physics.
Over the past decade, the importance of relativistic electron losses from Earth’s radiation belts has also
become increasingly clear. There is evidence that the radiation belts are emptied during the main phase
of geomagnetic storms before being refilled by newly accelerated particles. However, the relative importance of atmospheric precipitation losses versus magnetopause losses is not known, and the processes that
scatter relativistic particles into the atmosphere have not been experimentally validated. BARREL (Balloon
Array for RBSP Relativistic Electron Losses) will augment RBSP by providing a low-altitude component to
quantify electron precipitation. BARREL consists of several balloon campaigns during which an array of