Copyright © National Academy of Sciences. All rights reserved.
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
187
launcher (in a manner similar to the launch and separation of the six COSMIC satellites on one launcher),
and operations and telemetry transmissions are very straightforward. If the estimated cost of the nominal
GDC configuration with six satellites falls outside of available budget limits, the panel also considered a
GDC constellation with only four satellites. In this case, the prime GDC science objectives can still be
met, yet in a less robust sense. Coverage becomes more regional and less local, because only eight local
time planes can be supported. Nevertheless, such an observing scenario would provide important strides
forward in understanding of the AIM system.
Expected Outcomes
The IT constellation proposed here will provide a major advance in the field of heliophysics, addressing fundamental physical processes and providing a new level of understanding of geospace. Specifically,
through its global and simultaneous measurements of interconnected state variables, GDC will provide
(1) breakthroughs in understanding of feedbacks between field-aligned currents, ion drifts (electric fields),
conductivities, neutral densities, and winds that result from the interaction between the atmosphereionosphere and the magnetosphere; (2) fundamental discoveries of global ion-neutral coupling and feedback processes active in the geospace-atmosphere system; (3) unprecedented knowledge about how the
ionosphere-thermosphere system at global, regional, and local scales responds to variations in solar EUV
irradiance, tropospheric forcing, and solar wind (magnetospheric) driving; and (4) the data required to
advance space weather models of the AIM system to the next level of sophistication.
8.5.1.2 DYNAMIC (Dynamical Neutral Atmosphere-Ionosphere Coupling) Mission (Moderate Class)
Overview
A highly compelling, complementary, and somewhat less expensive way to advance knowledge of
the AIM system would be to devote a mission to answering the question, How does lower-atmosphere
variability affect geospace? The primary goal of DYNAMIC is to address wave coupling with the lower
atmosphere, and to come to near-closure on understanding how lower-atmosphere variability drives neutral and plasma variability in the IT system. It concentrates on revealing and understanding the processes
(i.e., wave dissipation, mean-flow interactions) that underlie the transfer of energy momentum into the IT
system (especially within the critical 100- to 200-km-height regime) and the thermosphere and ionosphere
variability that these waves incur at higher altitudes.
Mission Configuration
The above science focus translates to a mission involving instruments that remotely sense the lower and
middle thermosphere while also collecting in situ data at higher altitudes. A key mission driver is the need
to address atmospheric thermal tides, which demand measurements over all local times. Since satellites
generally take weeks to months to precess through 24 hours of local time, one therefore must trade latitude
coverage against local time precession rate, or possibly consider multiple satellites. To include important
wave sources at high latitudes such as weather systems and stratospheric warmings, and moreover to separate aurorally generated waves from those originating in the lower atmosphere, a high-inclination (75°-90°)
satellite is required. However, for these orbital inclinations, 24-hour local time precession occurs over a
time period that exceeds that of important variability that needs to be captured. Taking these factors into
account, the preferable strategy is two identical satellites in 80° inclination orbits at 600-km altitude, with
their orbital planes spaced about 6 hours apart in local time. Assuming measurements are made at four
local times over all longitudes in one day, all zonal (longitudinal) components of the diurnal (24-hour) tide
would be fully characterized once per day, and semidiurnal (24-hour) tides as well as the diurnal mean
Solar and Space Physics: A Science for a Technological Society
REPORT OF THE PANEL ON ATMOSPHERE-IONOSPHERE-MAGNETOSPHERE INTERACTIONS
187
launcher (in a manner similar to the launch and separation of the six COSMIC satellites on one launcher),
and operations and telemetry transmissions are very straightforward. If the estimated cost of the nominal
GDC configuration with six satellites falls outside of available budget limits, the panel also considered a
GDC constellation with only four satellites. In this case, the prime GDC science objectives can still be
met, yet in a less robust sense. Coverage becomes more regional and less local, because only eight local
time planes can be supported. Nevertheless, such an observing scenario would provide important strides
forward in understanding of the AIM system.
Expected Outcomes
The IT constellation proposed here will provide a major advance in the field of heliophysics, addressing fundamental physical processes and providing a new level of understanding of geospace. Specifically,
through its global and simultaneous measurements of interconnected state variables, GDC will provide
(1) breakthroughs in understanding of feedbacks between field-aligned currents, ion drifts (electric fields),
conductivities, neutral densities, and winds that result from the interaction between the atmosphereionosphere and the magnetosphere; (2) fundamental discoveries of global ion-neutral coupling and feedback processes active in the geospace-atmosphere system; (3) unprecedented knowledge about how the
ionosphere-thermosphere system at global, regional, and local scales responds to variations in solar EUV
irradiance, tropospheric forcing, and solar wind (magnetospheric) driving; and (4) the data required to
advance space weather models of the AIM system to the next level of sophistication.
8.5.1.2 DYNAMIC (Dynamical Neutral Atmosphere-Ionosphere Coupling) Mission (Moderate Class)
Overview
A highly compelling, complementary, and somewhat less expensive way to advance knowledge of
the AIM system would be to devote a mission to answering the question, How does lower-atmosphere
variability affect geospace? The primary goal of DYNAMIC is to address wave coupling with the lower
atmosphere, and to come to near-closure on understanding how lower-atmosphere variability drives neutral and plasma variability in the IT system. It concentrates on revealing and understanding the processes
(i.e., wave dissipation, mean-flow interactions) that underlie the transfer of energy momentum into the IT
system (especially within the critical 100- to 200-km-height regime) and the thermosphere and ionosphere
variability that these waves incur at higher altitudes.
Mission Configuration
The above science focus translates to a mission involving instruments that remotely sense the lower and
middle thermosphere while also collecting in situ data at higher altitudes. A key mission driver is the need
to address atmospheric thermal tides, which demand measurements over all local times. Since satellites
generally take weeks to months to precess through 24 hours of local time, one therefore must trade latitude
coverage against local time precession rate, or possibly consider multiple satellites. To include important
wave sources at high latitudes such as weather systems and stratospheric warmings, and moreover to separate aurorally generated waves from those originating in the lower atmosphere, a high-inclination (75°-90°)
satellite is required. However, for these orbital inclinations, 24-hour local time precession occurs over a
time period that exceeds that of important variability that needs to be captured. Taking these factors into
account, the preferable strategy is two identical satellites in 80° inclination orbits at 600-km altitude, with
their orbital planes spaced about 6 hours apart in local time. Assuming measurements are made at four
local times over all longitudes in one day, all zonal (longitudinal) components of the diurnal (24-hour) tide
would be fully characterized once per day, and semidiurnal (24-hour) tides as well as the diurnal mean