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A Science Strategy for Space Physics: Part III
A Science Strategy for Space Physics
Part III
Research Strategy
Part III outlines the four common thrusts in the committees' recommended
strategy for future U.S. research in space physics, and it summarizes the more
specific research efforts recommended to address the five key scientific topics
that the CSSP and CSTR believe should be and will be at the forefront of
research in space physics during the next decade. Those five topics, discussed in
detail in Chapters 1 through 5, are listed in Box 3. Under each topic, the research
activities recommended by the committees are entered in the order of their
priority (i.e., the highest priorities are listed first).
RECOMMENDED RESEARCH ACTIVITIES
REPORT MENU
NOTICE In generating the prioritized lists of recommended research activities, the
MEMBERSHIP
CSSP and CSTR considered the following issues:
SUMMARY
PART I
PART II Importance. What is the importance of a particular research activity to
CHAPTER 1 answering the questions posed for the related major topic? Is the research effort
CHAPTER 2 highly likely to resolve one or more important issues? Does it address a major
CHAPTER 3 piece of the puzzle?
CHAPTER 4
CHAPTER 5
Timeliness. Is the technology necessary to conduct the activity in
PART III
APPENDIX hand or on the near horizon, and is the activity ripe for progress if initiated in the
coming decade? Is the activity time-critical or a unique opportunity? Does the
activity take advantage of the availability of new tools?
Breadth. Would the results of the research activity provide
fundamental understanding with broad applicability? Would the results be
applicable to other aspects of space physics, to space science in general, or to
other branches of science?
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A Science Strategy for Space Physics: Part III
Practical relevance. Is the research activity highly relevant to the issue
of the effects of solar variability on the Earth?
Balance. Would implementation of the activity help redress the current
imbalance1between "big" and "little" science and between planning,
development, and pure science activities in space physics?
It is important to use with care and common sense the priorities
recommended in this report. In many cases the activities are not really in direct
competition; they address different scientific issues, their funding agencies may
be different, and the amount of money needed may be very different. A priority
rank is not an absolute attribute; it is a function of the question being asked. If
one carries out only the highest-priority activity that addresses a particular
question, the question will not be answered unambiguously or completely. Lower-
priority activities can often be justified over higher-priority ones if they are more
affordable in the current environment or if they better meet some other goal such
as balance between subdisciplines, research techniques, institutions, or other
parameters that were not taken into account in the present study. Often two or
more lower-priority items taken together can be as important as a single higher-
priority item. Also to be factored in are new or unforeseen developments or
results in science and technology. But, other things being equal, the committees
believe that the scientific precedence for space physics research is that given in
Box 3.
RECOMMENDED RESEARCH EMPHASES
The recommended research activities listed in Box 3 are elements of the
overarching goal of achieving greater understanding of the physical processes
that underlie the observable phenomena of space physics. These rather detailed
lists of diverse research efforts incorporate four common elements that the CSSP
and CSTR consider to be the most important emphases for space physics
research in the next decade:
1. Complete currently approved programs. Successful completion of
the current programs is the committees' highest-priority objective, given that the
committees endorse the previous scientific strategies for which those programs
were proposed and approved. Successful completion of the current efforts will
provide the foundation to which new elements will be added to make scientific
progress. In making successful completion of current undertakings the first
priority, the committees emphasize that space physics programs do not end with
the launch of a spacecraft or the construction of a new facility. For an effort to be
worthwhile, the data must be acquired, carefully analyzed, and interpreted. Each
of those steps, followed by theoretical assimilation of the results, is necessary to
gain the insights needed to advance the science. Furthermore, giving increased
emphasis to data collection and interpretation will also help improve the balance
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between large- and small-scale efforts in space physics. It must also be
recognized, however, that the high priority given to successful completion of
established programs does not imply blanket endorsement of extended missions.
Each mission extension must compete on its own merits with other ways in which
the same resources could be spent. The committees' specific recommended
actions for experiment operation and data analysis and interpretation are as
follows:
a. Completing the diverse components of the International Solar-
Terrestrial Physics program. This includes the full-term support of mission
operations and data analysis, with effective coordination of the observational and
data-analysis campaigns involving the many spacecraft, both U.S. and foreign,
and supporting ground-based observatories. The flight projects should cooperate
with the several organizations or programs (GEM, STEP, and the IACG) that
have been put in place for that purpose.
b. Enhancing data analysis and interpretation efforts for other space
missions that have been launched recently or are currently in development.
These include Yohkoh, SAMPEX, FAST, ACE, SOHO, Galileo, and Cassini.
Adequate support is also required for the successful fulfillment of the objectives
of NSF's CEDAR, GEM, and SUNRISE programs.
c. Streamlining mission operations to help keep extended missions going
as well as minimize operations costs for new missions.
d. Carrying out extended missions for the uniquely placed Voyager (to the
greatest possible heliocentric distance) and Ulysses (through the solar polar
passes at solar maximum).
e. Continuing support of those ground- and space-based observations
that require improved statistics or the acquisition of data over a range of solar-
cycle conditions. At issue are (1) gap-free, space-based observations of the
variability of solar luminosity, (2) solar neutrino and helioseismological
observations, and (3) monitoring of the composition, dynamics, and temperature
of the middle and upper atmospheres to obtain a baseline for future studies of
climate changes, together with (4) monitoring and prediction of space "weather"
in support of a wide range of research and operational activities.
f. Enhancing the effectiveness of some of the longer-duration programs
by soliciting new ideas and analysis techniques from guest investigators and by
ensuring easy access to archived data resulting from the various programs for
use in "small science" research tasks.
2. Exploit existing technologies and opportunities to obtain new
results in a cost-effective manner. The technology is already in place to take
the next observational steps required to address many of the important questions
in space physics. Both spacecraft and instrument technology are available to
complement point-by-point in situ measurements of the magnetosphere with
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A Science Strategy for Space Physics: Part III
global imaging and to carry out a multi-spacecraft mission capable of establishing
a baseline for studies of changes in the middle and upper atmospheres while
separating spatial from temporal effects in those regions. Measurement of solar
irradiance variations can also be carried out using current instrument designs.
Other objectives can be addressed effectively by inclusion of instruments for
space physics research on missions of opportunity, such as NASA's planetary
missions and Department of Defense spacecraft, or through international
collaborations. On suborbital platforms such as rockets and balloons or on the
ground at new sites such as in the polar cap, operation of existing types of
instruments can allow unique studies of some aspects of magnetosphere-
ionosphere-atmosphere coupling. The advent of new networking, telescience,
and other collaboration methods allows real-time display of data from widely
separated sensors. Exploiting this technology allows experiments and
observations to be optimized while reducing costs.
3. Develop the new technology required to advance the frontiers of
space physics. We must continue to push the limits of technology in order to
achieve other high-priority objectives or to lower the cost of projects that are
already technically feasible. The technology required to approach the Sun ever
more closely will open one of the most exciting frontiers of space science. New
spacecraft using lightweight structures and miniaturized electronics, and balloon
technology allowing 8- to 20-day flights around the South Pole, should enable
some high-priority space physics measurements to be made inexpensively in the
near term. A good start has been made in the development of the new
technology required for the study of high-energy radiation and particles from
transient solar events with high angular and spectral resolutions and wide
spectral coverage. New techniques for fabrication of lightweight optics are
becoming available from the former Soviet Union. Advanced instruments for the
analysis of the rarest components of the cosmic radiation such as very heavy or
very energetic particles must continue to be developed and flight-tested on long-
duration balloons that can carry heavier payloads than are possible with current
balloons. Small, capable instruments must be developed to enable affordable in
situ measurements of the solar corona, the distant heliosphere, and some
regions of planetary magnetospheres. Advances are also required in (a) infrared
instrumentation and a large-aperture infrared-capable solar telescope, (b) second-
generation instruments for magnetospheric imaging with greater sensitivity,
energy and composition discrimination, and angular resolution, and (c)
instrumentation for exploring the regions between those altitudes reached by
balloons and by satellites.
As already mentioned, one of the conclusions of this report is that the
highest near-term priority for space physics is the successful completion of the
ISTP program and thorough correlation and analysis of the diverse sets of data
that it will generate. That recommendation is entirely consistent with the current
emphasis on the development of space technology that can be transferred to
other sectors of the economy. The operations and data analysis phase of ISTP is
a good opportunity for the development and use of new technology for
experiment operations, automated or remote operations of ground-based
scientific facilities, data distribution and archiving, and data visualization and
other aids to interpretation.
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4. Support strongly the theory and modeling activities vital to space
physics. As emphasized in previous reports,2-5 theory and modeling
complement data analysis as vital components of all the subdisciplines of space
physics research. In the coming decade, special attention or emphasis should be
given to the following:
a. Recognizing that synergy between observations, modeling, and theory
provides the optimum way of addressing the principal questions in space physics;
b. Making numerical simulations of space physics systems more realistic
by extending them to three dimensions, longer time durations, and a greater
range of scale sizes, and including additional interacting physical and chemical
processes;
c. Ensuring that space physicists have ready access to state-of-the-art
computational facilities, given that modeling relevant processes will require an
order-of-magnitude increase in computer throughput;
d. Exploiting new insights gained from theory, especially the theory of
nonlinear processes. Such work has already been started, with the development
of new ways of looking at nonlinearities. Some problems, such as understanding
the solar dynamo, require totally new theoretical insights, as opposed to
extended modeling or simulations. It is possible that such insights might result
from plasma-physics experiments performed in terrestrial laboratories; and
e. Revisiting earlier efforts to predict solar activity, such as coronal mass
ejections and flares, using simulations combined with solar observations.
Although the four areas of emphasis summarized above are in priority
order, it is absolutely essential that progress be made in all four. The space
physics community must reap the benefits of what has already been built and
paid for. Space physicists must take advantage of existing capabilities to make
new types of measurements in a cost-effective way. Researchers must also
develop and use the technology required for future progress. Finally, space
physicists must continuously digest the new data, decide what those data mean,
and keep fine-tuning and reviewing the scientific questions that drive the
research.
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A Science Strategy for Space Physics: Part III
Box 3
Prioritized Listing of Research Activities in Five Topics Identified as Key
Areas for Study in the Next Decade
Mechanisms of Solar Variability
Use helioseismology to study the structure and dynamics of the solar
surface and interior over a full solar cycle.
Assure continuity of total and spectral irradiance measurements,
supported by spatially resolved spectrophotometry, to investigate correlations
between solar magnetic activity and solar output variations.
Measure high-energy radiation and particles from flares and coronal mass
ejections with good angular resolution, good spectral resolution, and wide
spectral coverage to determine what drives each of these phenomena and
how they contribute to the solar output at high energies.
Observe surface magnetic fields, velocities, and thermodynamic
properties with enough spatial resolution (<150 km, with an ultimate goal of
<100 km) to study small-scale structures such as flux tubes.
Make global-perspective measurements of the solar surface magnetic and
velocity fields and solar oscillations to measure the three-dimensional
structure and long-term evolution of active regions and to detect weak but
coherent global oscillations.
Measure active regions with angular resolution of ~1 arc sec and temporal
resolution of ~10 min for a duration of ~10 days without nighttime gaps to
determine their magnetohydrodynamic history of emergence, development,
and decay.
The Physics of the Solar Wind and the Heliosphere
Continue to obtain and synthesize the data from the present constellation
of heliospheric spacecraft (Voyager, Ulysses, Wind, and ACE) and from the
interplanetary cruise phases of planetary missions in order to characterize the
global and solar-cycle-dependent properties of the heliosphere and its
interaction with the interstellar medium.
Carry out in situ observations of the solar corona to explore and
characterize the region of acceleration of the solar wind plasma and the
physical processes responsible for that acceleration.
Obtain new types of data required to reveal the mechanisms responsible
for the transport of energy from the solar surface into the chromosphere and
corona to understand how these are heated.
Carry out stereo imaging of the solar corona to reveal the three-
dimensional structure of coronal features without the ambiguity caused by
integration along the line of sight.
Develop and use techniques for the remote sensing of the coronal
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magnetic field in order to improve knowledge of the acceleration of the solar
wind and of the initiation of coronal mass ejections.
Make in situ measurements of the outer heliospheric boundaries and the
interstellar medium with instruments specifically designed for those purposes.
The Structure and Dynamics of Magnetospheres and Their Coupling to
Adjacent Regions
Reap the full scientific potential of the International Solar-Terrestrial
Physics program and its coordinated programs to advance understanding of
the transport of mass, momentum, and energy throughout the solar wind, and
the magnetosphere and ionosphere systems.
Simultaneously image the plasma and energetic particle populations in the
aurora, plasmasphere, ring current, and inner plasma sheet to study the
global structure and large-scale interactions of magnetospheric and
ionospheric regions during different levels of solar and geomagnetic activity.
Maintain the full complement of particle and field instruments on current
and future planetary missions to gain increased understanding of the
formation and dynamics of diverse magnetospheres and ionospheres.
Further develop and exploit ground-based facilities that image the
ionospheric manifestations of solar wind/magnetosphere coupling processes
to complement the magnetospheric imaging initiative aimed at studying the
global properties of the magnetosphere.
Explore Mercury's magnetosphere to understand the role of an ionosphere
in coupling between the solar wind and planetary magnetospheres.
Target localized regions that require greater understanding of the small-
scale physical processes occurring there with high-resolution, multispacecraft
measurements that take advantage of new smaller, lighter, more capable
instruments and more sophisticated data-compression schemes.
The Middle and Upper Atmospheres and Their Coupling to Regions Above
and Below
Exploit the exciting new capabilities of UARS, FAST, and CEDAR to
provide the foundation for future advances in our understanding of the middle
and upper atmospheres.
Investigate the reaction of the middle and upper atmospheres to upward
propagating waves and energy inputs from space so that the sources of
important features such as the quasi-biennial and semiannual oscillations and
the causes of mesosphere/lower-thermosphere structure and variability can
be understood.
Study the long-term variations in the middle and upper atmospheres using
a combination of consistent long-term satellite and ground-based
measurements together with three-dimensional radiative-chemical-dynamical
modeling to understand natural and anthropogenic changes in these regions.
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Develop methods to observe the time-dependent electrodynamics
operating on microscales to global scales, both in the upper atmosphere-
ionosphere-magnetosphere coupling regions so that feedback processes can
be characterized, and in the regions above thunderstorms so that the effects
of electrified clouds on the "global circuit" and on middle atmosphere
chemistry and energetics can be characterized.
Take advantage of opportunities to include carefully chosen, appropriate
instruments on planetary orbiter missions to make measurements critical to
understanding planetary aeronomy and its relation to terrestrial aeronomic
processes.
Plasma Processes That Accelerate Very Energetic Particles and Control Their
Propagation
Complete the observations from the current and planned network of
interplanetary spacecraft to study particle acceleration, fractionation, and
transport.
Extend direct composition measurements to 1015 eV to probe the limits of
acceleration and trapping mechanisms.
Measure abundances of radioactive isotopes above 1 GeV/nucleon to
search for evidence of an extended galactic magnetosphere and wind.
Measure the spectra of positrons (10 MeV to 100 GeV) and antiprotons
(100 MeV to 100 GeV) to determine where those particles are created and
how they are accelerated.
Measure isotope abundances for nuclei heavier than nickel and elemental
abundances through the actinides to probe the plasma regions where the
nuclei are synthesized and to measure the time scales involved.
REFERENCES
1. Board on Atmospheric Sciences and Climate and the Space Studies
Board, National Research Council, A Space Physics Paradox: Why Has
Increased Funding Been Accompanied by Decreased Effectiveness in the
Conduct of Space Physics Research?, National Academy Press, Washington,
D.C., 1994.
2. Space Studies Board and the Board on Atmospheric Sciences and
Climate, National Research Council, Assessment of Programs in Solar and
Space Physics—1991, National Academy Press, Washington, D.C., 1991.
3. Space Science Board, National Research Council, Solar-System
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A Science Strategy for Space Physics: Part III
Space Physics in the 1980's: A Research Strategy, National Academy of
Sciences, Washington, D.C., 1980.
4. Space Science Board, National Research Council, The Role of Theory
in Space Science, National Academy Press, Washington, D.C., 1983.
5. Space Science Board, National Research Council, An Implementation
Plan for Priorities in Solar-System Space Physics, National Academy Press,
Washington, D.C., 1985.
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