1. Solar & Space Physics Decadal Survey Leading Principle: To make transformational scientific progress, the Sun, Earth, and heliosphere must be studied as a coupled system. Solar & Space Physics Decadal Survey Leading Principle: To make transformational scientific progress, the Sun, Earth, and heliosphere must be studied as a coupled system. Space Climate Initiative

2. Solar variability drives our space environment and upper atmosphere Solar variability drives our space environment and upper atmosphere Current and past Sun-Earth system model development has mainly focussed on space weather (goal of short term prediction) Current and past Sun-Earth system model development has mainly focussed on space weather (goal of short term prediction) Solar variability drives our space environment and upper atmosphere Solar variability drives our space environment and upper atmosphere Current and past Sun-Earth system model development has mainly focussed on space weather (goal of short term prediction) Current and past Sun-Earth system model development has mainly focussed on space weather (goal of short term prediction) Space weather affects geomagnetic fields (power grids) ionosphere (GPS/communications) thermosphere (satellite drag) radiation belt (satellite failure) galactic cosmic rays (astronaut safety) Our technological society requires reliable forecasting of our future “space climate” Our technological society requires reliable forecasting of our future “space climate” The proposed initiative will incorporate models developed for space weather, but for the first time examine longer-term, space climate variation by driving the system with solar dynamo models The proposed initiative will incorporate models developed for space weather, but for the first time examine longer-term, space climate variation by driving the system with solar dynamo models It will enable an improved assessment of how variable solar forcing affects climate modeling It will enable an improved assessment of how variable solar forcing affects climate modeling Our technological society requires reliable forecasting of our future “space climate” Our technological society requires reliable forecasting of our future “space climate” The proposed initiative will incorporate models developed for space weather, but for the first time examine longer-term, space climate variation by driving the system with solar dynamo models The proposed initiative will incorporate models developed for space weather, but for the first time examine longer-term, space climate variation by driving the system with solar dynamo models It will enable an improved assessment of how variable solar forcing affects climate modeling It will enable an improved assessment of how variable solar forcing affects climate modeling Our goal is to understand how extremes of solar variability affect space climate and climate by modeling the system from the Sun’s interior to the Earth’s atmosphere Our goal is to understand how extremes of solar variability affect space climate and climate by modeling the system from the Sun’s interior to the Earth’s atmosphere

3. Solar drivers of space climate and climate Total Solar Irradiance (TSI) is modulated by solar cycle (about.1% from minimum to maximum) EUV irradiance shows stronger modulation As does thermospheric neutral density. Radiation Recent minimum is unusually deep

4. Sunspots are associated with geomagnetic activity Solar drivers of space climate and climate Solar maxima are stormy Particles Fast solar wind streams in declining phase Heliospheric magnetic structure and activity differ from cycle to cycle Solar wind structure also drives geomagnetic activity

5. What is the range of possible solar radiative and particulate inputs to the Earth system? New advances in three-dimensional solar dynamo modeling enable controlled experiments in flux emergence to characterize the decadal variation of the Sun’s surface magnetic field. New advances in three-dimensional solar dynamo modeling enable controlled experiments in flux emergence to characterize the decadal variation of the Sun’s surface magnetic field. What is the range of possible solar radiative and particulate inputs to the Earth system? New advances in three-dimensional solar dynamo modeling enable controlled experiments in flux emergence to characterize the decadal variation of the Sun’s surface magnetic field. New advances in three-dimensional solar dynamo modeling enable controlled experiments in flux emergence to characterize the decadal variation of the Sun’s surface magnetic field. Babcock-Leighton Flux Transport dynamo -- 3D global simulations Photospheric magnetic boundary Magnetic flux emergence

6. Photospheric magnetic boundary Particulate inputs to magnetosphere and upper atmosphere community models Coronal and heliospheric magnetic models What is the range of possible solar radiative and particulate inputs to the Earth system? Using the magnetic field as a boundary condition, coronal and heliospheric models can be used to establish solar wind and geomagnetic proxies as inputs to upper atmospheric models Using the magnetic field as a boundary condition, coronal and heliospheric models can be used to establish solar wind and geomagnetic proxies as inputs to upper atmospheric models What is the range of possible solar radiative and particulate inputs to the Earth system? Using the magnetic field as a boundary condition, coronal and heliospheric models can be used to establish solar wind and geomagnetic proxies as inputs to upper atmospheric models Using the magnetic field as a boundary condition, coronal and heliospheric models can be used to establish solar wind and geomagnetic proxies as inputs to upper atmospheric models

7. Photospheric magnetic boundary Radiative inputs to upper atmosphere and climate community models Radiative magnetohydrodynamic modeling What is the range of possible solar radiative and particulate inputs to the Earth system? HAO supercomputer simulations of sunspots and radiative magnetohydrodynamics are yielding new insight into how the Sun’s surface magnetism affects its spectral radiation -- a key input to climate models. HAO supercomputer simulations of sunspots and radiative magnetohydrodynamics are yielding new insight into how the Sun’s surface magnetism affects its spectral radiation -- a key input to climate models. What is the range of possible solar radiative and particulate inputs to the Earth system? HAO supercomputer simulations of sunspots and radiative magnetohydrodynamics are yielding new insight into how the Sun’s surface magnetism affects its spectral radiation -- a key input to climate models. HAO supercomputer simulations of sunspots and radiative magnetohydrodynamics are yielding new insight into how the Sun’s surface magnetism affects its spectral radiation -- a key input to climate models.

8. As an initial extreme, motivated by the recent “quiet” solar minimum and possible long-term changes in sunspots, experiments will be run to assess: What happens to the solar atmosphere and heliosphere, and, by extension, the Earth's space environment and climate, if flux emergence occurs only on scales too small to form sunspots? As an initial extreme, motivated by the recent “quiet” solar minimum and possible long-term changes in sunspots, experiments will be run to assess: What happens to the solar atmosphere and heliosphere, and, by extension, the Earth's space environment and climate, if flux emergence occurs only on scales too small to form sunspots? During the Maunder Minimum, few or no sunspots were observed for nearly 70 years, a time period corresponding to the “Little Ice Age” in Europe. While questions remain as to whether these events are causally linked, such a “Grand Minimum” must have had profound effects on the Earth’s space environment.

9. The 1859 “Carrington event” was a superstorm that occurred “on the eve of a below-average solar cycle.” It did arise from a sunspot of unusual size and complexity, however. Thus, we are motivated to run experiments to assess: What sort of flux emergence is likely to foster superstorms such as the 1859 “Carrington flare”? Thus, we are motivated to run experiments to assess: What sort of flux emergence is likely to foster superstorms such as the 1859 “Carrington flare”?

10. Summary We will run dynamo-driven, physically self-consistent experiments that vary flux emergence. We will run dynamo-driven, physically self-consistent experiments that vary flux emergence. We will utilize and expand upon existing empirically-constrained parameterizations that connect the resulting photospheric magnetic boundaries with solar wind and irradiance models. We will utilize and expand upon existing empirically-constrained parameterizations that connect the resulting photospheric magnetic boundaries with solar wind and irradiance models. We will design and enact community upper atmosphere and climate model runs incorporating the resulting radiative and particulate inputs (TIME-GCM; WACCM-X). We will design and enact community upper atmosphere and climate model runs incorporating the resulting radiative and particulate inputs (TIME-GCM; WACCM-X). By focusing on specific science questions (sun without sunspots, conditions fostering superstorms) we enable an effective multidisciplinary collaboration; however, the methodology that will be set up may be used to examine a broad range of potential space climate conditions. Summary We will run dynamo-driven, physically self-consistent experiments that vary flux emergence. We will run dynamo-driven, physically self-consistent experiments that vary flux emergence. We will utilize and expand upon existing empirically-constrained parameterizations that connect the resulting photospheric magnetic boundaries with solar wind and irradiance models. We will utilize and expand upon existing empirically-constrained parameterizations that connect the resulting photospheric magnetic boundaries with solar wind and irradiance models. We will design and enact community upper atmosphere and climate model runs incorporating the resulting radiative and particulate inputs (TIME-GCM; WACCM-X). We will design and enact community upper atmosphere and climate model runs incorporating the resulting radiative and particulate inputs (TIME-GCM; WACCM-X). By focusing on specific science questions (sun without sunspots, conditions fostering superstorms) we enable an effective multidisciplinary collaboration; however, the methodology that will be set up may be used to examine a broad range of potential space climate conditions.

11. Resources needed: Many NCAR scientists are working on fundamental science underlying the various physical regimes that make up the coupled Sun-Earth system. The proposed initiative seeks to unite and coordinate these efforts with complementary activities ongoing in the community in order to most effectively study the system as a whole. We expect to need resources on the level of four NCAR FTEs and four external collaborator FTEs, plus shared postdoctoral associates and graduate students, for a period of 4-5 years.

12. Expected impact: The proposed effort will establish for the first time the response of space climate to extremes in solar variability better quantify how such extremes are likely to affect climate Consistent with NCAR’s mission, this advances fundamental science of the coupled Sun-Earth system. It enables our nation to build resilience and infrastructure to appropriately prepare for extreme space climate conditions.

13. Extra Slides

14. Open questions: Dynamo and flux emergence How much flux is necessary to form a sunspot? Under what conditions can the dynamo continue to cycle without sunspots? How will cycle lengths, amplitudes, and asymmetries (longitudinal, hemispheric), be affected by the lack of sunspots? Under what conditions will "standard" sunspot cycles return? Solar surface and atmosphere How would total and spectral irradiance be affected by a lack of sunspots? What will the distribution of closed vs. open flux in the corona look like, including longitudinal and hemispheric asymmetries? How will magnetic flux distribution and associated radiative properties affect solar wind acceleration? How will magnetic energy build up in the corona, and what sorts of flares/CMEs are likely to ensue (are Carrington events more likely?) Heliosphere and space environment How will galactic cosmic rays be affected by changes in coronal/heliospheric magnetic structure and activity? How will space environment (aurorae, radiation belts, thermosphere) be affected by changes in coronal/heliospheric structure and activity? Climate How will Earth's upper atmosphere be affected by changes in TSI and SSI, galactic cosmic rays, aurorae and radiation belts? How will lower atmosphere and oceans be affected? What role will interactions/feedbacks between these

15. Details of Proposed Methodology: Our investigation would incorporate the following elements (bullets progress from minimum to ideal level of development) 1) Three-dimensional cyclic dynamo model mean-field dynamo (non-axisymmetric) non-kinematic dynamo (including effects of e.g. torsional oscillations, meridional flow into active regions, tachocline instabilities) fully convective dynamo model 2) Flux emergence process connecting interior to surface (using output of 1) "Spot-maker": A 3D formulation of the Babcock-Leighton mechanism that mimics the destabilization, rise, and emergence of toroidal flux tubes buoyantly-rising flux tubes of varying sizes within global simulations modeling full emergence of flux tubes through the photosphere 3) Coronal magnetic field model from time-evolving magnetic boundary (using output of 2) Potential field extrapolation MHD model (sequence of quasi-static equilibria; e.g. solution for each rotation) - give evolution of open/closed field MHD model (with memory of evolving boundary - e.g. magnetofrictional) - could give frequency and strength of CME 4) Model SSI and TSI from time-evolving magnetic boundary (output of 1-2) Use existing empirical relationships between sunspot group number (based on flux concentration threshold) and total magnetic flux and TSI Use magnetic distribution to identify regions as sunspot, faculae/plage, active network, and quiet sun; apply models for spectral emission for each category; integrate to obtain both TSI and SSI Use radiative MHD forward modeling of spectral emission

16. 5) Solar wind modeling (using outputs of 3-4)  Use existing empirical relationships between magnetism and solar wind  MHD model with more complete energy equation  MHD model with energy equation coupled to magnetic flux distribution/radiative properties (implicitly incorporate chromosphere) 6) Space environment modeling (using outputs of 3-5)  Geomagnetic index and TSI proxies  Time varying solar wind velocity, magnetic field  Cosmic ray modeling/proxies 7) Climate modeling (using outputs of 4-6)  Upper atmosphere responses to particulate and radiative environment  Lower atmosphere/ocean responses  Coupling between these regions