Exploring Solar-Terrestrial Interactions via Multiple Observers (A White Paper for the Voyage 2050 long-term plan in the ESA Science Programme) (1908.04730v1)

Abstract: This paper addresses the fundamental science question: "How does solar wind energy flow through the Earth's magnetosphere, how is it converted and distributed?". We need to understand how the Sun creates the heliosphere, and how the planets interact with the solar wind and its magnetic field, not just as a matter of scientific curiosity, but to address a clear and pressing practical problem: space weather, which can influence the performance and reliability of our technological systems, in space and on the ground, and can endanger human life and health. Much knowledge has already been acquired over the past decades, but the infant stage of space weather forecasting demonstrates that we still have a vast amount of learning to do. We can tackle this issue in two ways: 1) By using multiple spacecraft measuring conditions in situ in the magnetosphere in order to make sense of the fundamental small scale processes that enable transport and coupling, or 2) By taking a global approach to observations of the conditions that prevail throughout geospace in order to quantify the global effects of external drivers. A global approach is now being taken by a number of space missions under development and the first tantalising results of their exploration will be available in the next decade. Here we propose the next step-up in the quest for a complete understanding of how the Sun gives rise to and controls the Earth's plasma environment: a tomographic imaging approach comprising two spacecraft which enable global imaging of magnetopause and cusps, auroral regions, plasmasphere and ring current, alongside in situ measurements. Such a mission is going to be crucial on the way to achieve scientific closure on the question of solar-terrestrial interactions.

• The paper proposes a mission concept leveraging multiple observers to address key science questions about how solar wind energy transfers and is modulated within Earth's magnetosphere.
• The proposed approach advocates for combining in situ spacecraft measurements with global geospace imaging, specifically highlighting a future mission capable of tomographic imaging via two spacecraft.
• Understanding these interactions is crucial for societal needs, enhancing space weather forecasting to predict and mitigate impacts on vulnerable technological systems.

Overview of the White Paper "Exploring Solar-Terrestrial Interactions via Multiple Observers"

The white paper, "Exploring Solar-Terrestrial Interactions via Multiple Observers," authored by Pollock et al., serves as a comprehensive proposal to enhance the understanding of solar wind interactions with Earth's magnetosphere. It focuses on the articulation of both practical and scientific implications arising from these interactions and presents a detailed mission concept to address open questions related to solar-terrestrial dynamics.

Key Science Questions

This work addresses how solar wind energy is transferred and modulated within Earth's magnetosphere. Several critical sub-questions underpin this investigation:

1. Mechanisms of energy transfer at the magnetopause.
2. Drivers of various magnetospheric regimes.
3. Dynamics of energy circulation through the magnetotail.
4. Hemispheric asymmetries in magnetospheric behaviors.
5. Sources and sinks of ring current and radiation belt plasma.
6. Influence of inner magnetospheric feedback on solar-terrestrial processes.

The need for a more profound and quantitative understanding of these interactions is emphasized by the societal dependency on technological systems that are vulnerable to space weather events.

Methodological Approach

The paper argues for a dual strategy in approaching these scientific questions:

1. In situ measurements through arrays of spacecraft (e.g., Cluster, THEMIS).
2. A broader observational approach, using missions that can globally image geospace, such as SMILE and LEXI.

The proposition of a future M-class mission capable of tomographic imaging via two spacecraft is highlighted. This mission aims to achieve a decisive understanding of the heliospheric processes influencing Earth's plasma environment by providing global imaging of the magnetosphere's critical boundaries and processes.

Core Themes

Energetics and Dynamics

The paper elaborates on dynamic processes within the magnetosphere, including the crucial role of magnetic reconnection, the formation and behaviors of the plasmasphere, radiation belts, and ring currents. It examines reconnection modes, variability in the dayside and nightside interaction processes, and the implications of asymmetric magnetic topology across hemispheres.

Technological Context

Technological advancements in space-based sensors, such as X-ray, FUV, and ENA imagers, and EUV sensors, are outlined as vital to observing these complex interactions. These instruments, coupled with in situ plasma and field measurements, provide a holistic picture of the energetic and magnetic configurations of Earth's space environment.

Future Mission Design

Key mission design concepts involve maintaining polar tandem orbits for continuous and stereo vision imaging across multiple spectral domains, allowing the enhanced 3-D reconstruction of the magnetosphere's structure. The proposed in situ measurements in both hemispheres and coordinated ground-based observations are fundamental for validating theoretical models and improving predictive capabilities.

Implications

The paper identifies numerous implications for both understanding solar-terrestrial physics and addressing societal needs for space weather forecasting. By deploying advanced measurement techniques and mission designs, the authors argue that the outlined mission can resolve ongoing questions about the energy transport processes and their modulations, enhancing our ability to predict and mitigate space weather impacts on technological systems.

Future Directions

Speculative advancements include integrated solar-magnetospheric modeling combining fluid and kinetic models, potentially augmented with AI methodologies. The speculated development and validation of empirical models will be considerably enhanced through the proposed comprehensive imaging techniques.

In summary, this white paper articulates the rationale and conceptual framework for a proposed mission designed to enhance our understanding of solar-terrestrial interactions. By leveraging advanced sensing technologies and multiple observational platforms, the research could significantly contribute to the field of space weather and solar-terrestrial physics.