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9 Report of the Panel on Solar Wind-Magnetosphere Interactions
9 Report of the Panel on Solar Wind-Magnetosphere Interactions
Pages 209-260
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From page 209... ...
For the coming decade, the Panel on Solar Wind-Magnetosphere Interactions (SWMI) identified a set of eight high-priority science goals for research in solar wind-magnetosphere interactions -- goals that follow naturally from the progress that has been made and will contribute substantially toward accomplishing the decadal survey key science goals for solar and space physics identified in Chapter 1 of this report.
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From page 210... ...
In this chapter, the SWMI panel advocates a coherent and balanced program of research in solar wind-magnetosphere interactions based on a prioritized set of imperatives that will enable a cost-effective approach to accomplishing the SWMI science goals. These imperatives are sorted into three categories: (1)
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From page 211... ...
4. Ensure strong continued support for existing satellite assets that can still contribute significantly to high-priority science objectives.
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From page 212... ...
Implementation of these imperatives will enable achievement of the exciting and high-priority science goals laid out in this report, providing a strong foundation for the accomplishment of the long-term actions described earlier in this decadal survey. To summarize, eight overarching SWMI science goals motivate sixteen prioritized, actionable imperatives that are required to enable the goals (these prioritized imperatives and their mapping to decadal categories from Part I are shown in Table 9.4 at the end of this chapter)
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From page 213... ...
"Magnetic reconnection" is the process by which energy stored in magnetic fields
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From page 214... ...
9.2.1.4 Space Weather and the Magnetosphere "Space weather" is the name given to the time-dependent conditions and changes that occur in near-Earth space to the magnetospheric plasmas and fields. These include changes in the plasma density, temperature, and spatial distributions, from the cold plasmasphere to the very energetic radiation belts.
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From page 215... ...
The following sections outline recent progress made toward addressing the fundamental questions raised by these motivations; indicate the outstanding problems where significant progress can be accomplished in the near future, leading to the identification of specific science goals for the coming decade; and lay out the SWMI panel's imperatives for actions that are needed to meet those goals. 9.3 SIGNIFICANT ACCOMPLISHMENTS OF THE PREVIOUS DECADE 9.3.1 Scientific Progression The science of solar wind-magnetosphere interactions was established near the dawn of the space age, only 50 years ago.
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From page 216... ...
Figure 9-2 Thanks to observations from new satellite missions, new analyses of data from previous missions, and improved numerical modeling capabilities, substantial progress has been made in the past decade to advance the field along the progression illustrated in Figure 9.2. Here the SWMI panel reviews some of these significant accomplishments.
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From page 217... ...
These results represent more than a huge leap forward in system-level knowledge of the ring current; they also offer a tantalizing hint of the dynamic magnetospheric behavior that could be uncovered with higher-resolution, continuous, and global imaging. 9.3.3 Processes 9.3.3.1 Magnetic Reconnection The recent decade has witnessed substantial progress in understanding how magnetic reconnection works.
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From page 218... ...
FIGURE 9.3 At the center is a schematic of the magnetosphere indicating the regions where magnetic reconnection usually occurs. The lower panel is a simulation result of the quadrupolar magnetic field topology in the ion diffusion region, and the left and right panels are observations of these field topologies by the Polar and the Wind spacecraft, respectively.
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From page 219... ...
Other studies quantified that the strength of geomagnetic storms depends on both the electrodynamic coupling between the solar wind and the magnetosphere and plasma loading of the magnetosphere, including both ionospheric and solar wind sources. Spacecraft observations and numerical simulations reveal that solar-wind plasma entry into the magnetosphere is surprisingly efficient under "quiescent" conditions of northward interplanetary magnetic field.
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From page 220... ...
Changes in the north-south component of the IMF were shown to trigger the aurora, ring current injections, and the commencement or cessation of plasmaspheric erosion. Numerical models and global ENA images showed that the ring current is highly asymmetric during the main phase of storms (Figure 9.6)
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From page 221... ...
Merkin, Influence Figure 2-10 and 9-5 of cusp O(+) outflow on magnetotail dynamics in a multifluid MHD model of the magnetosphere, Journal of Geophysical Research-Space Physics 115:A00J05, 2010.
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From page 222... ...
show the partial ring current whose pressure distorts the solar wind forcing field that erodes the plasmasphere. SOURCE: Adapted from J
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From page 223... ...
In this section, the SWMI panel takes stock of where we are in the progression shown in Figure 9.2, and identifies the high-priority science goals that must be pursued in the coming decade. After describing each science goal, the panel discusses how their accomplishment relates to the achievement of the four decadal survey key science goals identified in Chapter 1 (see Box 9.1)
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From page 224... ...
MacDowall, and A Lecacheux, The reversal of the rotational modulation rates of the north and south components of Saturn kilometric radiation near equinox, Geophysical Research Letters 37:L24101, doi:10.1029/2010GL045796,2-7 and 9-7 2010 American Geophysical Union.
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From page 225... ...
In sum, scientists do not know the instantaneous global and mesoscale structure of each of the various regions, nor how it evolves with time and solar wind driving. To understand how the system as a whole behaves in response to variations in the solar wind driver requires a better view of the simultaneous evolution of the various parts of the system, leading to the first SWMI science goal for the coming decade.
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From page 226... ...
226 SOLAR AND SPACE PHYSICS: A SCIENCE FOR A TECHNOLOGICAL SOCIETY TABLE 9.1 Expected Level of Contribution of Each SWMI High-Priority Science Goal to Accomplishing the Decadal Survey Key Science Goals of Chapter 1 Decadal Key Science Goals Understand the dynamics and Discover and coupling of Earth's characterize Determine the origins magnetosphere, Determine the fundamental processes of the Sun's activity ionosphere, and interaction of the Sun that occur both within and predict the atmosphere and their with the solar system the heliosphere variations in the space response to solar and and the interstellar and throughout the SWMI Science Goals environment terrestrial inputs medium universe Determine how the global and mesoscale structures in the magnetosphere respond to variable solar wind forcing Identify the controlling factors that determine the dominant sources of magnetospheric plasma Understand how plasmas interact within the magnetosphere and at its boundaries Establish how energetic particles are accelerated, transported, and lost Discover how magnetic reconnection is triggered and modulated Understand the origins and effects of turbulence and waveparticle interactions Determine how magnetosphereionospherethermosphere coupling controls system-level dynamics Identify the structures, dynamics, and linkages in other planetary magnetospheric systems Contribution to Action Major Large Significant Some Minimal
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From page 227... ...
While touching on decadal survey key science goals 1, 3, and 4, this thrust is aimed squarely at decadal survey key science goal 2. This problem is one of the most challenging scientific problems remaining in the realm of geospace, and one of the most important to solve toward the goal of providing the capability to predict the effects of solar variability on the environment and on society.
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From page 228... ...
Multiple observations at the magnetopause have demonstrated that reconnection between the geomagnetic field and the IMF controls solar wind entry into the magnetosphere. However, fundamental questions on this process remain.
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From page 229... ...
These issues must be resolved in order to develop a predictive understanding of the ionospheric response to solar wind forcing; their resolution also has strong links to decadal survey key science goals 2 and 4. Identifying the factors that control solar wind and ionospheric contributions to magnetospheric populations is fundamental to determining the dynamics of the magnetosphere, ionosphere, and atmosphere, their coupling, and the response to solar wind variability.
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From page 230... ...
This goal directly addresses decadal survey key science goal 2, with significant contributions to understanding fundamental processes (key science goal 4) and enabling prediction of magnetospheric variability (key science goal 1)
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From page 231... ...
It is expected that RBSP will provide definitive answers to many of the outstanding questions in this area, but since it has not yet launched, the SWMI panel reiterates the enduring importance of those questions and endorses anew the science objectives of the RBSP mission. Predicting the variability of the highly energetic and thus hazardous populations of our space environment is a central part of decadal survey key science goal 1.
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How fast does reconnection happen in these more complex three-dimensional geometries? The questions outlined above, while specifically addressing decadal survey key science goal 4, also contribute to decadal survey key science goal 2.
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From page 233... ...
. Turbulence in both the magnetosheath and the magnetotail provides unique opportunities to discover and characterize fundamental processes that occur here and throughout the universe (decadal survey key science goal 4)
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From page 234... ...
Understanding the dynamic behavior of the coupled system is central to completing decadal survey key science goal 2 and undergirds the ability to make quantitative predictions about the space environment, making this goal also relevant to decadal survey key science goal 1. Furthermore, understanding system-level dynamics will help advance knowledge of the fundamental processes that couple the regions of geospace, providing a connection to decadal survey key science goal 4 as well.
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From page 235... ...
These discoveries are universal, applicable to all four decadal survey key science goals, but in particular, comparative magnetospheric studies document the variety of ways that the Sun interacts with the solar system (3) and enable exploration of fundamental processes over a broad range of conditions inaccessible at Earth (4)
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From page 236... ...
Achieving these eight SWMI science goals will contribute significantly to accomplishing the decadal survey key science goals (see Table 9.1)
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As amply demonstrated by the sampling of scientific accomplish ments from the past decade presented above, major progress toward the SWMI panel science goals
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From page 238... ...
These relatively small, investigator-led studies enable researchers to exploit the data from missions and connect them to relevant theoretical frameworks. The SWMI panel strongly supports the survey committee's conclusion that the key science goals identified in this decadal survey can be most effectively accomplished with a well-balanced program that uses the full spectrum of implementation options.
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From page 239... ...
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)
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From page 240... ...
Solar Probe Plus and Solar Orbiter These missions, while aimed directly at solar and heliospheric science objectives, are also likely to shed light on fundamental physical processes that are high on the list of science objectives for SWMI, namely, particle acceleration, reconnection, turbulence, and wave-particle interactions. Insights gained about how these processes work near the Sun can potentially help advance understanding of how they operate in near-Earth space, thereby helping address SWMI critical science goals 4 through 6.
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From page 241... ...
9.5.2.4 New Strategic Missions Analysis of the rich set of data derived from ongoing missions and missions in development, combined with new approaches that will emerge from the Explorer and other smaller mission lines, will provide a firm foundation for accomplishing the SWMI critical science goals outlined in this chapter for the coming decade. However, attaining those goals will also require crucial new observations that have previously been impossible.
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From page 242... ...
MEDICI's science questions address how the magnetosphere-ionosphere-thermosphere system is coupled and responds to solar and magnetospheric forcing. In particular, this mission concept directly addresses SWMI critical science goals 1 and 4, with very significant contributions as well to science goals 2 and 3 (Table 9.2)
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From page 243... ...
Goal 5: Establish how energetic particles are accelerated, transported, and lost. Goal 6: Discover how magnetic reconnection is triggered and modulated.
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From page 244... ...
Using ENA imaging, the ring current and near-Earth plasma sheet are captured with sufficient temporal and spatial resolution (1 minute, 0.5 RE) to retrieve the electrical current system that distorts the magnetic field and that connects through the ionosphere producing the electric field.
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From page 245... ...
The likely long duration of the MEDICI mission will allow it to provide a transformative framework into which additional future science missions can naturally fit. Table 9.2 summarizes MEDICI's expected level of contribution to the SWMI science goals.
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From page 246... ...
This concept directly addresses SWMI critical science goals 2 and 4, with additional contributions to goals 3 and 7. Although the science addressed by this mission is of high merit, the panel is aware that budget realities will likely prevent its initiation as a strategic mission in the coming decade.
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From page 247... ...
The primary objective of the MISTE mission concept is to quantify the amount of ionospheric outflow given a particular intensity of electromagnetic or particle energy input to the upper atmosphere. Therefore, the primary instrumentation of MISTE is the in situ thermal and suprathermal particle detectors and the electric and magnetic field instruments.
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From page 248... ...
The SWMI panel believes that these contributions would enable great progress toward the applicable objectives, but in recognition of probable budget constraints over the coming decade, the panel developed the following SWMI imperative: SWMI Imperative: If resources permit, initiate a strategic mission like MISTE to simultaneously measure the inflow of energy to the upper atmosphere and the response of the ionosphere-thermosphere system to this input, in particular the outflow back to the magnetosphere.
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Key magnetospheric measurements for a Uranus mission would include magnetic field, plasma waves, plasma, energetic particles, dust and neutral mass spectra, and global images 7 National Research Council, Vision and Voyages for Planetary Science in the Decade 2013-2022, The National Academies Press, Washington, D.C., 2011.
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In particular, the SWMI panel's highest priority in planetary magnetospheres is a mission to orbit Uranus. 9.5.2.5 Future Strategic Missions Determining how mesoscale and global structures in the magnetosphere respond to variable solar wind forcing and understanding how plasmas interact within the magnetosphere and at its boundaries both require observations that match these scales.
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From page 251... ...
that make magnetic field plus plasma and energetic particle distribution function measurements at multiple points simultaneously with relatively rapid cadence. The mission requires a significant number of spacecraft, 36 in the concept the SWMI panel evaluated, to achieve mesoscale spacing while filling a significant fraction of the near-Earth space using orbits with perigees in the 7-8 RE range and apogees dispersed uniformly up to 25 RE with low inclination.
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From page 252... ...
9.5.3.1 Solar Wind Monitor Knowledge of upstream solar wind conditions, the interplanetary magnetic field, and solar energetic particles is required in essentially all of the programs that would address the SWMI science objectives. Currently, instruments on the ACE8 spacecraft, which orbits around the L1 libration point approximately 1.5 million km from Earth, provide these data.
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From page 253... ...
The SWMI panel therefore strongly encourages the agencies to enhance the funding of R&A programs. In a constrained funding environment, this is one of the most cost-effective ways to ensure that the high-priority science objectives outlined in this decadal survey will be accomplished.
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From page 254... ...
A number of the science goals outlined in Section 9.4 involve connecting phenomena and signatures that occur in the ionosphere with their corresponding phenomena and signatures in the magnetosphere. Because this connection occurs primarily via the geomagnetic field, which is strongly distorted and highly variable due to currents flowing within the magnetosphere itself, an accurate mapping between the ionosphere and magnetosphere for all relevant conditions is lacking.
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From page 255... ...
However, to enable research on basic plasma physics that will be of greater utility to SWMI science objectives, the panel supports the creation of an interagency joint laboratory astrophysics program. This program should be competed on a regular basis, include selection criteria that focus on issues relevant to space physics, contain a mechanism for outside investigators to have access to supported facilities, and be open to proposals from any institution.
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From page 256... ...
9.5.4 Space Weather As suggested by its title, the long-term goal of this decadal survey is to have the knowledge to ensure the well-being of a society dependent on space. Actionable knowledge of space environment effects involves the ability to characterize conditions anywhere in the system at any time in the past, as well as to predict future conditions with good fidelity.
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From page 257... ...
Achieving the key science goals of this decadal survey requires identifying the optimum set of operational observations to drive models that will enable specification and prediction of the environment throughout the magnetosphere. This effort may ultimately require an operational "great observatory" of satellites in appropriate orbits for monitoring crucial aspects of the input from and response to solar wind variability.
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From page 258... ...
12 Encourage the creation of a complete architecture for the National Space Weather Program that would coordinate joint research, commercial, and operational space weather observations and define agency roles for producing, distributing, and forecasting space weather products. In addition the SWMI panel encourages all agencies to foster interactions between the research and operational communities and to identify funding for maintaining a healthy research-to-operations and operations-to-research program.
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From page 259... ...
The panel's prioritization -- which informed the survey committee but does not carry its imprimatur -- is based on the overarching objective to identify initiatives that will most costeffectively enable the science of the future. Accordingly, the SWMI panel adopted the following criteria: • General considerations for prioritization -- Focus on elements that are directly relevant to the enumerated SWMI science goals.
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From page 260... ...
9.6.3 Planetary Science The magnetospheres of other planets display not only certain close similarities, such as the formation of bow shocks and radiation belts, but also many processes that are markedly different, such as the source of charged particles within the radiation belts, which can vary from a mixture of the solar wind and ionosphere at Earth, to lava volcanoes and water geysers on small moons at Jupiter and Saturn. This rich diversity has provided surprising discoveries of the breadth of expression of fundamental physical processes that play important roles in the acceleration of charged particles and the generation of magnetic fields in planetary magnetospheres.
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