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From page 37... ...
The three science themes -- interconnectedness, building blocks, and new environments -- capture and combine common threads within the field of solar and space physics. These themes are deliberately broad, mostly region or subdiscipline agnostic, and encompass a wide range of solar and space physics science in a balanced fashion.
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From page 38... ...
The local cosmos, dominated by the energy released by the Sun, provides an opportunity to study plasma and neutral interactions ranging from those deep in the Sun's interior, to those in the solar atmosphere, the solar wind, magnetospheres and atmospheres of planets and moons, and the farthest reaches of the solar system where the solar wind slams into the interstellar medium. All these natural systems, called "heliosystems" in this report, are vast reservoirs of plasmas, energetic particles, neutral gases, and electromagnetic fields that exhibit complex interactions within and amongst themselves.
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From page 39... ...
The Sun's magnetic dynamo produces magnetic fields that evolve in a complex and cyclic manner over a wide range of spatial and temporal scales. These magnetic fields structure the solar atmosphere and are drawn out into the solar wind.
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From page 40... ...
However, the in situ observations and remote observations from a single perspective during the propagation of any of these structures through the heliosphere leave major questions unresolved about the solar sources and generation processes of CMEs as well as their expansion into the heliosphere. Major challenges for the next decade are to understand the generation of magnetic fields inside the Sun, their emergence into the solar atmosphere, and how this magnetic field is carried by the supersonic solar wind to the outer heliosphere where it couples to the local interstellar medium.
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From page 41... ...
The energy that these structures carry powers explosive magnetic reconfiguration processes as well as particle energization processes -- such as magnetic reconnection -- enabling energy, momentum, and plasma transport from the solar wind into the planetary space environments (magnetospheres)
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From page 42... ...
FIGURE 2-4 The complexity of the combined effects of plasma physical processes associated with solar wind impacting Earth and the solar radiation effects, tides, gravity waves, and neutral winds in the neutral atmosphere. The interlinked systems generate a complex set of time-varying electric currents connecting the ionosphere to the high-altitude magnetosphere, upward and downward motion of electrons and ions, as well as upflow of atmospheric neutrals.
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From page 43... ...
Their role in the mass and energy budget of the corona and solar wind remains an active area of intense interest. Dominant Physical Processes Within System Interactions The Sun, the solar wind, and the planetary space environments are composed of distinct plasmas that each have their own characteristic composition and energy distribution, and these plasmas have their own dynamical evolution that is governed by different physical and chemical processes operating at various temporal and spatial scales.
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From page 44... ...
remote sensing observations revealed how the boundary responds to the pressures of solar wind from the inside and the very local interstellar medium (VLISM) from the outside.
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From page 45... ...
In addition, bow shocks form as a consequence of the interaction of the supersonic solar wind with the planetary magnetic fields, ionospheres, and atmospheres. However, not all boundaries in space plasmas are sharp transitions across a (rotational or tangential)
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From page 46... ...
These switchbacks reveal as yet unconfirmed evidence of the origin of the fast solar wind and interplanetary magnetic field in the solar corona. The several theories that have been proposed await confirmation from the continuing PSP mission to map them ever deeper into the atmosphere of the Sun and connect them to observed activity there.
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From page 47... ...
Understanding the control parameters of the energy transport processes at the magnetospheric (and other) boundaries requires a systems approach that addresses the transport of energy in both directions over the global surface and accounts for the state of the solar wind as well as that of the magnetosphere.
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From page 48... ...
This cross-tail structure of the transition region has critical implications for how energy and magnetic flux are delivered into the inner magnetosphere, how the ring current and radiation belts are built up via particle injections, how energy and momentum are deposited in the upper atmosphere across different scales, and how these phenomena are reflected in a variety of mesoscale auroral forms. Much of the current observational knowledge about the transition region and its interaction with the upper atmosphere has been derived from fortuitous, but rare and ad hoc, multispacecraft conjunctions (e.g., THEMIS mission, Van Allen Probes mission, MMS mission, Geotail satellite, Los Alamos National Laboratory geostationary satellites, Geostationary Operational Environmental Satellites [GOES]
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From page 49... ...
By the time the solar wind flow reaches the outer heliosphere, the solar magnetic field that is carried out with the wind wraps around the Sun and forms a tightly bound spiral. This spiral is disturbed by large solar eruptions that create both energetic particle bursts and plasma clouds that reach the outer fringes of the solar system.
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From page 50... ...
However, the local space environment is the only place where detailed plasma measurements are made in systems not limited by artificial boundaries. Magnetic Connections Across the Heliosystems This focus area has only one related topic: Magnetic Fields as Connectors.
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From page 51... ...
Such asymmetries arise from the position of the dipole field slightly away from the center of Earth, its inclination relative to Earth's rotation axis and to the ecliptic plane, and over shorter timescales from the orientation of the interplanetary magnetic field and solar wind flow. While it would be important to include such asymmetries in physics-based models, the lack of observations from the southern hemisphere limits the ability to quantify the asymmetries.
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From page 52... ...
Multiple Drivers and Feedback Mechanisms This focus area has two related topics: Between the Heliosphere and Interstellar Matter and Between the Atmosphere and Space. Between the Heliosphere and Interstellar Matter Plasmas and magnetic fields in the interstellar medium act as a barrier to the expanding solar wind.
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From page 53... ...
Changes in the density of the thermosphere on multidecadal timescales have been observed, but it is not known what other consequences such slow composition variations may have, or how these variations may affect the response of this region to the solar wind and magnetospheric processes. Furthermore, it is not known how the changes in the lower atmosphere weather systems will alter the relative impact of the solar variability.
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From page 54... ...
large-scale coupling • Interactions at plasma- Magnetosphere: Combination of neutral transition regions multispacecraft in situ measurements, magnetospheric imaging, and numerical simulations. Upper atmosphere: Multiplane, multialtitude measurements of the auroral outflow processes, including plasma and neutral components.
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From page 55... ...
The nature and consequences of the coupling between ionized and neutral gases are only now beginning to be understood. A a orator n ace: TH EME Bu ld ng Bloc o nder tand ng o are t e e lo e G U ID ING Q ' S o do t e undamental How is the Sun's global enomena created and roce e go ern t e cro magnet c field created and d ated acro t e cale cou l ng and at are t e ma nta ned and at h el o ere and at are t e glo al ro ert e and causes its cyclical undamental roce e t at con e uence o t e e ar at on contr ute to t e energ roce e con er on Flo and field acro all nerg con er on n ro cale m l cat on o olar lat tude e lo e e ent magnet c reconnect on RESEARCH F O CU S AREAS n age o t e nter or field on e uence o t e ro cale cou l ng to t e glo al el o ere aggregat on o nd dual t roug nteract on e lo e e ent between magnetic ong tud nal ar at on o t e reconnect on tur ulence d namo and t e field Re on e o tem to oc a e art cle e lo e e ent nteract on and art cle accelerat on n ta l t e and a e t cro cale con e uence ature and con e uence o cou l ng et een on ed and neutral u d FIGURE 2-11 Guiding questions and research focus areas within Theme 2 -- A Laboratory in Space: Building Blocks of Understanding.
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From page 56... ...
In the context of the interplanetary medium, neutral gas, predominantly hydrogen, flows through the solar wind experiencing charge exchange and creating interstellar pickup ions that form the dominant thermal plasma component from about 20–30 astronomical units (AU) until the heliospheric boundary, the heliopause.
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From page 57... ...
. This final piece of the global dynamo puzzle is answered using direct observations of the flows and magnetic fields in the Sun's polar region.
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From page 58... ...
Energy Conversion in Explosive Events Magnetospheric substorms and solar flares are prototypical examples of explosive events. Each occurs when stored magnetic energy is released by magnetic reconnection and converted into other forms.
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From page 59... ...
Explosive events in the terrestrial magnetosphere often occur in response to solar wind driving. The solar wind energy enters Earth's magnetosphere through a series of boundaries such the bow shock and the magnetopause, which involves dissipative processes that allow the solar wind mass, momentum, and energy to be transported and energized across the boundaries.
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From page 60... ...
Cross-Scale Implications of Magnetic Reconnection On Earth, magnetic reconnection is a dominant process that allows solar wind to enter the magnetosphere through magnetospheric boundaries. The entering solar wind energy ultimately drives geomagnetic storms, substorms and ionospheric dynamics such as auroras.
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From page 61... ...
The energy conversion mechanisms at shocks have been directly measured, including such mechanisms as a cross-shock electrostatic potential, current-driven instabilities, magnetic reconnection in the shock transition region, other wave-particle interactions, and particle acceleration and reflection. The region in front of the bow shock (the foreshock)
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From page 62... ...
The Van Allen Probes made significant advances in the understanding of the dynamics of the inner magnetosphere, including the radiation belts and ring current, showing definitively that local acceleration by wave particle interactions occurs in the center of the radiation belts and are responsible for the formation, acceleration, and loss of energetic particle populations. Combined data from Van Allen Probes, CubeSats, and balloons, together with modeling, revealed that ordersof-magnitude depletions of the radiation belts can occur in a few hours or less, caused by a combination of magnetopause shadowing and precipitation into the atmosphere owing to interactions with plasma waves.
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From page 63... ...
The altitude, location, and timing of this transition is still unknown, as well as the processes and scales that govern it. The Atmospheric Waves Experiment and ground-based observations, along with the DYNAMIC mission, offer the opportunities to elucidate the mechanisms that govern the transition in chemical, dynamical, and thermal drivers across the ITM from ~100–200 km; determine how the gravity wave spectrum cascades throughout the thermosphere and impacts the ITM system; and determine how nonlinear coupling between mean neutral atmosphere circulation, tides, and planetary waves drives ITM variability.
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From page 64... ...
The NASA Carruthers Geocorona Observatory seeks to answer these basic questions. The termination shock and heliopause are also influenced by the coupling of neutral and ionized components as neutrals entering the solar system are picked up by the out-bound solar wind.
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From page 65... ...
the corona and solar wind. How do fundamental • Energy conversion in Sun: High cadence spectroscopic Models spanning local processes create and explosive events imaging of solar flares.
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From page 66... ...
The anticipated return of humans to the Moon in the next decade is opening new doors to investigate space plasma processes and solar wind-lunar interactions. There is much to be learned about other moons and small bodies embedded in the continuous and ever-changing solar wind.
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From page 67... ...
Such measurements have revealed the physical processes that link activity on the surface of the Sun to variations in the solar wind that drive Earth's space environment and impact all planetary objects and beyond, out into the interstellar medium. The guiding questions and research focus areas for Theme 3 (Figure 2-17)
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From page 68... ...
Mass and Energy Flow Processes Driving Planetary Magnetospheres A major focus of this report is how Earth's magnetosphere and ionosphere respond as a system to the solar wind and interplanetary magnetic field. Exploration of the magnetospheres of other planets has shown that a similar system-wide response occurs; however, there are significant variations in this response (e.g., with distance from the Sun, strength and/or orientation of the magnetic field, and different plasma regimes)
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From page 69... ...
. This extreme tilt leads to radical changes in the geometry of the solar wind and interplanetary magnetic field interacting with Uranus's magnetosphere.
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From page 70... ...
UOP will provide ground truth relevant to the most abundant, similarly sized class of exoplanets." From a space science perspective, it is key that such a mission carry sufficient particles and fields instrumentation to fully explore the unique magnetosphere of Uranus. Interactions of Plasmas with Atmospheres and Solid Body Surfaces Until recently, the majority of the space science community embraced the idea that an intrinsic magnetic field was required to shield a planet from the solar wind eroding its atmosphere.
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From page 71... ...
, solar radiation (including X-rays and UV) , the solar wind, and energetic particles (energetic solar protons and galactic cosmic rays)
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From page 72... ...
ultraviolet spectrometer instrument detected far UV oxygen emissions on the dayside of Mars with detailed structures that suggest solar wind thermal electrons penetrate through the upper atmosphere but are directed by the strong crustal (remnant) magnetic fields to the footprints of the field lines.
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From page 73... ...
While the Sun is the only host that is known to harbor life, Sun-like stars are among the more abundant types of stars. While there are detailed observations about the Sun, the solar wind, and physical processes like solar flares and CMEs, these observations do not reveal what the Sun and heliosphere were like in the past, or what they will become in the future.
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From page 74... ...
While these rates are long compared to civilizations, they are short compared to geologic timescales. Similar to the interplanetary magnetic field in the solar system, stellar magnetic fields are frozen into their stellar winds.
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From page 75... ...
Increased collaboration between the solar/heliospheric and stellar astrophysics communities provide opportunities for progress on these science challenges. One of the guiding questions of the decadal survey for astronomy and astrophysics was "How Do the Sun and Other Stars Create Space Weather?
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From page 76... ...
Scherer, S.E.S. Ferreira, et al., 2020, "On the Diversity of M-star Astrospheres and the Role of Galactic Cosmic Rays Within," The Astrophysical Journal Letters 897(2)
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From page 77... ...
In a similar fashion, the interstellar medium continually buffets the heliosphere shielding, deflecting and focusing high-energy galactic cosmic rays from the habitable zone where Earth resides. The Voyager observations during traversal of the heliosheath (between the termination shock and the heliopause)
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From page 78... ...
radiation belts at Earth, Jupiter, and Uranus. These comparisons show the diversity of radiation belts at the magnetized planets.
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From page 79... ...
Progress relies on having space physics instrumentation onboard planetary missions as well as making remote sensing observations of planets with astronomical telescopes, which is achieved through the ongoing, strong cross-divisional collaboration and coordination within the NASA Science Mission Directorate. TABLE 2-3 New Environments: Exploring Our Cosmic Neighborhood and Beyond -- Theme 3 Guiding Questions, Research Focus Areas, and Observations Needed to Carry Out the Research Guiding Question Focus Area Observation Needs Model Needs What can we learn • Mass and energy Particles and fields measurements Magnetosphere models that from comparative flow processes throughout the magnetospheres of predict electromagnetic and studies of planetary driving planetary planets and their moons, ideally with particle fluxes under different systems?
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From page 80... ...
2019. "Highly Struc tured Slow Solar Wind Emerging from an Equatorial Coronal Hole." Nature 576:237–242.
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From page 81... ...
2023. "Solaris: A Focused Solar Polar Discovery-Class Mission to Achieve the Highest Priority Heliophysics Science Now." Community input paper submitted to the Decadal Survey on Solar and Space Physics.
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From page 82... ...
2020. "New Results Concerning Solar Wind Entry into the Magne tosphere." Eos.
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