Solar and Space Physics A Science for a Technological Society (2013) / Chapter Skim
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1 Enabling Discovery in Solar and Space Physics
1 Enabling Discovery in Solar and Space Physics
Pages 15-37
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From page 15... ...
The research elements of solar and space physics span solar electromagnetic and radiative processes, the generation of solar magnetic fields, the solar wind and interplanetary magnetic fields, and their evolution, development, and interaction with planets and moons that 1 An astronomical unit (AU) is the mean distance between Earth and the Sun; it is approximately 150 million kilometers (km)
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Van Allen, that would make the first revolutionary discovery of the space age, namely, that 2 Earth's magnetosphere is formed by the interaction of the solar wind and our planet's intrinsic magnetic field.
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The programs, initiatives, and investments in the field that are outlined in this report are designed to make fundamental advances in current scientific knowledge of the governing processes of the space environment -- from the interior of the Sun, to the atmosphere of Earth, to the local interstellar medium. These advances also enable predictive capabilities to be improved to the point that highly reliable forecasts can be made regarding the state of the space environment, particularly the disruptive space weather disturbances that threaten society and the economy, and their important technical infrastructure.
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Now, in the early part of the 21st century, as the Sun is ramping up its activity in solar cycle 24, decision makers are asking: Has there been adequate preparation for severe space weather events, and what might be the consequences of worst-case events like that of the storm of 1859? 3 To evaluate the nation's capabilities for forecasting and monitoring storms in space and for coping with their effects on Earth, the Space Studies Board of the National Research Council invited representatives of industry, academia, and the government to participate in a workshop in 2008 on the impacts of severe space weather on society and the economy.
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• Spacecraft manufacturers draw on current scientific knowledge of the space environment in an attempt to cost-effectively design and build commercial spacecraft that can operate 24/7 under severe space weather conditions. Spacecraft operators factor space weather conditions into decision making about whether to launch or to perform certain on-orbit operations.
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div=AST; details about NASA missions are available at http://www.nasa.gov/topics/solarsystem/ sunearthsystem/main/Missions_Heliophysics. html.
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enumerate the scientific opportunities and priorities for the interval addressed by this decadal survey, 2013-2022; these provide detail and context for the survey committee's four key science goals. 5 NRC, Controlling Cost Growth, 2010.
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The latest NLS contract, NLS II, was announced on September 16, 2010, and includes launch vehicle offerings from four vendors.1 This contract was subsequently amended in 2012 through its "on-ramp" provision to add SpaceX's Falcon 9 and Orbital Sciences' Antares launch vehicles.2,3 Prior to this, NASA added the United Launch Services' Delta II launch vehicle -- long a workhorse for launching NASA science missions -- back to its NLS II contract. However, that contract modification was limited to a maximum of five Delta II purchases, as opposed to the indefinite procurement nature of the other contracts.4 Therefore, the Delta II is being phased out once again through attrition.
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1 See NASA, "NASA Awards Launch Services Contracts," press release, September 16, 2010, available at http://www.nasa.gov/home/ hqnews/2010/sep/C10-053_Launch_Services_Contract.html. NOTE: This contract was amended in May and June 2012, respectively, to add SpaceX's Falcon 9 and Orbital Sciences' Antares launch vehicles.
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These coronal mass ejections (CMEs) , when aimed at Earth, can reach our planet in less than a day at speeds more than five times that of the background solar wind, the expanding solar atmosphere that fills the entire solar system and heliosphere.
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When the entrained solar wind magnetic field encounters Earth's magnetic field where the two magnetic fields are pointing in opposite directions, they can annihilate through the process of magnetic reconnection. (See Figure 1.4.)
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Figure 1-4 combined Earth's upper atmosphere and ionosphere are a rich laboratory for the investigation of radiative processes and plasma-neutral coupling in the presence of a magnetic field. The behavior can be extraordinarily complex: plasma-neutral collisions and associated neutral winds drive turbulence that cascades to very small spatial scales and regularly disrupts communications.
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Anomalous and galactic cosmic rays penetrate into the inner solar system, posing a danger for humans and spacecraft traveling to locations beyond those afforded protection by Earth's magnetic field. The supersonic flow of the solar wind transitions to a subsonic flow that merges with the local interstellar medium at a distance of about 100 AU from the Sun.
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Key Science Goal 4 K ey Science Goal 4. Discover and characterize fundamental processes that occur both within the heliosphere and throughout the universe.
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Turbulence in the convection zone of the solar interior twists and transports magnetic fields and ultimately determines the large-scale solar dipolar magnetic field, which reverses polarity on average every 11 years. Similar dynamos produce magnetic fields in stars, magnetars, and even in galaxies, black holes, and other compact objects.
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In framing its recommendations for progress over the next decade, the survey committee identified five assets of the solar and space physics program as necessary to realize the full scientific potential of the field. They are the (cross-agency)
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It will be revolutionary in the capabilities it will provide to measure the dynamics of the magnetic field at the solar surface down to the fundamental density length scale. It will also be able to remotely sense coronal magnetic fields in locations where they have never been measured.
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In addition, there is a need for a means of funding midscale projects, many of which have been identified by this decadal survey committee as cost-effective additions of high priority to the overall program. These include the Frequency-Agile Solar Radiotelescope (FASR)
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The survey committee believes that an adequate cadence for Heliospheric Explorers is one mission every 2 to 3 years, a rate that was possible before the major reduction in 2005 in the Explorer program. The survey committee also notes that competition for the MIDEX class of Explorers, which historically has offered an opportunity to resolve the highest-level science questions, has not been possible under the current Explorer budget.
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mission, which is scheduled for launch in 2018. In its deliberations, the survey committee BOX 1.4 SURVEY PRIORITIZATION AND THE CATE PROCESS In September 2010, shortly after the present decadal survey commenced, the survey committee distributed widely to the solar and space physics community a request for information (RFI)
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In Chapter 4 the survey committee describes the next science target best addressed by the LWS program when the budget of the Heliophysics Division allows: a mission to understand how Earth's atmosphere absorbs solar wind energy, illustrated by the Geospace Dynamics Constellation (GDC)
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Solar Probe Plus will be the first spacecraft to enter the outer atmosphere of the Sun, 1, 4 repeatedly sampling solar coronal particles and fields to understand coronal heating, solar wind acceleration, and the formation and transport of energetic solar particles. Solar Orbiter will provide the first high-latitude images and spectral observations of the 1, 4 Sun's magnetic field, flows, and seismic waves, relating changes seen in the corona to local measurements of the resulting solar wind.
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Indeed, as summarized in Table 1.1, the survey committee anticipates a decade of transformative advances in scientific understanding and observational capabilities, both space- and ground-based, upon implementation of the existing program and execution of the recommended program. Throughout this report, the committee emphasizes the necessity of adopting a systems approach to achieve appropriately balanced progress in understanding an interconnected solar-heliospheric-terrestrial and planetary system.
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