support of space-plasma and solar research, preferably through budget line items for laboratory facilities, would be beneficial.

10.5.5.7 Interagency Planning for a Future L5 Mission

SHP Imperative: The SHP panel assigns high priority to the development by NASA, NOAA, and DOD of plans for a mission at the L5 Lagrangian point to conduct helioseismology studies and develop advanced capabilities to forecast space weather.

Justification: From L5, it is possible to forecast the arrival of Earth-directed CMEs with high precision, to observe emerging or developed active regions and corotating interaction regions about 4 days earlier than from Earth, and to measure photospheric magnetic fields over about 60° additional longitude, improving magnetic-field models of regions rotating toward Earth.45 In addition, stereohelioseismology studies combining L1 and near-Earth observations have the potential to enable even longer solar-activity forecasts (§10.3.1 and §10.5.2.5).

The SHP panel encourages NASA, NOAA, and DOD to study means of achieving an L5 orbit for minimal cost and to define the spacecraft, instrument, and mission requirements needed to optimize the scientific and operational opportunities from a future L5 mission.

10.6 CONNECTIONS TO OTHER DISCIPLINES

The SHP panel has interests that are connected to those of the Panel on Atmosphere-Ionosphere-Magnetosphere Interactions (AIMI) and the Panel on Solar Wind-Magnetosphere Interactions (SWMI). Solar photon radiation and energetic particle outputs are primary energy inputs into and thus drivers of dynamic processes in Earth’s atmosphere, ionosphere, and magnetosphere and those of other planets. The Sun varies on timescales of minutes (flares, CMEs, and SEPs), days (27-day solar rotation), years (11-year solar-activity cycle), and even longer. There are corresponding responses throughout the heliosphere, including at Earth and other planets. Successful space weather modeling and forecasting of magnetospheric and ionospheric events include continuous tracing through interplanetary space and monitoring of conditions upstream of Earth. Consequently, most SHP panel initiatives also support AIMI and SWMI goals. Robust observational and modeling programs of solar outputs and interactive collaborations among the SHP, AIMI, and SWMI communities are critically important for current and future heliophysics research and space weather operations.

10.6.1 Earth Science and Climate Change

Solar-irradiance variations in the near-ultraviolet, visible, and near-infrared have direct forcing on Earth’s climate change because of energy deposition in the lower atmosphere and at the surface and oceans. The solar-energy input and other indirect forcings, such as top-down coupling of solar ultraviolet heating and photochemistry in the stratosphere, and the possible influence of galactic cosmic rays, affect both global climate changes and regional changes that are due to subtle changes in the atmosphere, ocean circulation patterns, and cloud cover. Solar-irradiance observations and reconstruction and modeling of long-term variations, such as improved solar-dynamo models, are important support for the Earth science

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45 A. Vourlidas et al., Mission to the Sun-Earth L5 Lagrangian Point: An Optimal Platform for Heliophysics and Space Weather Research, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 273; N. Gopalswamy et al., Earth-Affecting Solar Causes Observatory (EASCO): A New View from Sun-Earth L5, white paper submitted to the Decadal Strategy for Solar and Space Physics (Heliophysics), Paper 99.



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