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Solar and Space Physics: A Science for a Technological Society
334
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
electron beam along the magnetic field from a spacecraft in the equatorial magnetosphere and detecting
the location of the ionospheric foot point by optically imaging the airglow spot the beam produces.
This straightforward technique faces a number of technical issues. First, finding and imaging the beam
spot from the ground in the presence of auroral activity is challenging. Simply increasing the power of the
electron beam leads to a second challenge—preventing space charge within the beam and increased beam
divergence. The third challenge is perhaps the most severe: extracting negative charge from an ungrounded
spacecraft in the tenuous magnetosphere can lead to catastrophic spacecraft charging. A high-current
plasma contactor may provide a solution, but electron-beam pointing will degrade. Issues of optimizing
power-storage systems, accelerators, and plasma contactors for the spacecraft remain.
High-Resolution High-Cadence Infrared-Ultraviolet Imaging of the Solar Atmosphere (SHP)
Tracing the transformation of magnetic into kinetic and thermal energy in the solar atmosphere is
key to understanding processes that control heating and acceleration of flows and particles, as well as
large explosive phenomena with substantial impact on our space environment. Present detectors cannot
adequately measure these processes, which occur on spatial and temporal scales that push the observation
requirements to higher angular resolution (<0.1°) and faster cadence (<10 s). Imaging at the smallest scales
with the highest time resolution requires large-format, high-speed, high-efficiency detectors (advanced
charge-coupled devices, complementary metal-oxide semiconductors) and fast polarization modulators.
Design concepts exist, but implementation requires compromises between spatial and temporal
capabilities. Basic development must be followed by a staged approach with system integration and TRL
boosting. Synergism with ground-based development is possible in the visible spectrum.
High-Angular-Resolution Energetic Neutral Atom Imaging (SWMI and SHP)
Key magnetospheric processes associated with solar wind driving and ionospheric coupling occur from
global scales down to those of individual flux tubes, requiring both effective remote sensing and detailed
in situ measurements. Energetic neutral atom (ENA) imaging provides the global view, but currently with
insufficient spatial resolution, which would require ≈1° angular resolution and greater sensitivity. The
same advances will be sufficient for improving observations of the heliospheric boundary, for which 2-3°
is adequate.
Recent developments promising breakthrough improvements include ultra-thin foils for good statistics at moderately low energies, higher-efficiency electrostatic configurations for multiple-coincidence
measurements, sensor designs with intrinsic low sensitivity to visible and ultraviolet light, and improved
charged-particle rejection techniques. Important development steps include a system-level imager design
for an ultraviolet-blind detector, followed by TRL boosting.
Solar Flare Neutral Energetic Particle Imager (SHP)
Direct observations of neutral atoms at mega-electron-volt energies from solar flare regions provide
remote information about acceleration sites at the Sun, including spatial and temporal variations of the
acceleration processes (SHP3). Such particles have been observed serendipitously with the STEREO (Solar
Terrestrial Relations Observatory) High-Energy Telescope/Low-Energy Telescope, which was designed to
measure solar energetic ions. An optimized detector promises much greater sensitivity. This breakthrough
observation opens the door to another complementary flare diagnostic technique. Substantial advances
can be expected by optimizing proven techniques and applying them within the natural shield of Earth’s
Solar and Space Physics: A Science for a Technological Society
334
SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY
electron beam along the magnetic field from a spacecraft in the equatorial magnetosphere and detecting
the location of the ionospheric foot point by optically imaging the airglow spot the beam produces.
This straightforward technique faces a number of technical issues. First, finding and imaging the beam
spot from the ground in the presence of auroral activity is challenging. Simply increasing the power of the
electron beam leads to a second challenge—preventing space charge within the beam and increased beam
divergence. The third challenge is perhaps the most severe: extracting negative charge from an ungrounded
spacecraft in the tenuous magnetosphere can lead to catastrophic spacecraft charging. A high-current
plasma contactor may provide a solution, but electron-beam pointing will degrade. Issues of optimizing
power-storage systems, accelerators, and plasma contactors for the spacecraft remain.
High-Resolution High-Cadence Infrared-Ultraviolet Imaging of the Solar Atmosphere (SHP)
Tracing the transformation of magnetic into kinetic and thermal energy in the solar atmosphere is
key to understanding processes that control heating and acceleration of flows and particles, as well as
large explosive phenomena with substantial impact on our space environment. Present detectors cannot
adequately measure these processes, which occur on spatial and temporal scales that push the observation
requirements to higher angular resolution (<0.1°) and faster cadence (<10 s). Imaging at the smallest scales
with the highest time resolution requires large-format, high-speed, high-efficiency detectors (advanced
charge-coupled devices, complementary metal-oxide semiconductors) and fast polarization modulators.
Design concepts exist, but implementation requires compromises between spatial and temporal
capabilities. Basic development must be followed by a staged approach with system integration and TRL
boosting. Synergism with ground-based development is possible in the visible spectrum.
High-Angular-Resolution Energetic Neutral Atom Imaging (SWMI and SHP)
Key magnetospheric processes associated with solar wind driving and ionospheric coupling occur from
global scales down to those of individual flux tubes, requiring both effective remote sensing and detailed
in situ measurements. Energetic neutral atom (ENA) imaging provides the global view, but currently with
insufficient spatial resolution, which would require ≈1° angular resolution and greater sensitivity. The
same advances will be sufficient for improving observations of the heliospheric boundary, for which 2-3°
is adequate.
Recent developments promising breakthrough improvements include ultra-thin foils for good statistics at moderately low energies, higher-efficiency electrostatic configurations for multiple-coincidence
measurements, sensor designs with intrinsic low sensitivity to visible and ultraviolet light, and improved
charged-particle rejection techniques. Important development steps include a system-level imager design
for an ultraviolet-blind detector, followed by TRL boosting.
Solar Flare Neutral Energetic Particle Imager (SHP)
Direct observations of neutral atoms at mega-electron-volt energies from solar flare regions provide
remote information about acceleration sites at the Sun, including spatial and temporal variations of the
acceleration processes (SHP3). Such particles have been observed serendipitously with the STEREO (Solar
Terrestrial Relations Observatory) High-Energy Telescope/Low-Energy Telescope, which was designed to
measure solar energetic ions. An optimized detector promises much greater sensitivity. This breakthrough
observation opens the door to another complementary flare diagnostic technique. Substantial advances
can be expected by optimizing proven techniques and applying them within the natural shield of Earth’s