Solar Orbiter: Exploring the Sun-heliosphere connection (1207.4579v2)

Abstract: The heliosphere represents a uniquely accessible domain of space, where fundamental physical processes common to solar, astrophysical and laboratory plasmas can be studied under conditions impossible to reproduce on Earth and unfeasible to observe from astronomical distances. Solar Orbiter, the first mission of ESA's Cosmic Vision 2015-2025 programme, will address the central question of heliophysics: How does the Sun create and control the heliosphere? In this paper, we present the scientific goals of the mission and provide an overview of the mission implementation.

• The paper details the Solar Orbiter mission's scientific objectives, instrumentation, and architecture designed to explore the Sun-heliosphere connection.
• The mission uniquely combines in-situ and remote-sensing instruments with an orbit achieving close solar proximity (0.28 AU) and out-of-ecliptic views, including polar regions.
• Key goals include understanding the solar wind origin, transient impacts, energetic particle acceleration, and the solar dynamo to improve fundamental knowledge and space weather prediction.

Overview of "Solar Orbiter: Exploring the Sun-Heliosphere Connection"

The academic paper titled "Solar Orbiter: Exploring the Sun-Heliosphere Connection" provides an in-depth exploration of the Solar Orbiter mission, launched as part of the European Space Agency's Cosmic Vision 2015-2025 program. This paper delineates the scientific objectives and methodologies underlying the mission, highlighting its uniqueness in studying solar physics and heliospheric science.

The mission aims to address the fundamental question in heliophysics: how the Sun governs and interacts with the heliosphere. To this end, four primary scientific questions are posed:

1. What drives the solar wind, and where does the coronal magnetic field originate?
2. How do solar transients drive heliospheric variability?
3. How do solar eruptions produce energetic particle radiation throughout the heliosphere?
4. How does the solar dynamo operate and mediate the Sun-heliosphere connections?

Scientific Payload and Instrumentation

The Solar Orbiter carries a suite of both in-situ and remote-sensing instruments, coordinated between ESA and NASA. In-situ instruments include the Energetic Particle Detector (EPD), Magnetometer (MAG), Radio and Plasma Waves (RPW) analyzer, and Solar Wind Analyser (SWA). These tools collectively provide comprehensive measurements of solar wind particles, the heliospheric magnetic field, and wave emissions. The remote-sensing capabilities, such as the Extreme Ultraviolet Imager (EUI) and the Polarimetric and Helioseismic Imager (PHI), enable detailed solar observations in multiple wavelengths.

Mission Architecture and Design

The mission is structured to maximize the dual modalities of in-situ and remote-sensing observations, targeting regions as close as 0.28 astronomical units (AU) from the Sun. The heliographic latitude will be increased over time to provide multi-faceted views of solar phenomena. Using gravity assists from Earth and Venus, Solar Orbiter achieves a unique orbital inclination, allowing it to capture unexplored views of the Sun's polar regions.

Key Scientific Challenges and Goals

1. Solar Wind and Coronal Magnetic Fields: Understanding the origins of the solar wind and key magnetic regions involves identifying source regions and mechanisms of particle acceleration. The mission focuses on linking observational data of solar emissions and wind measurements to delineate these connections.
2. Heliospheric Dynamics from Solar Transients: The mission seeks to elucidate the interplay between CMEs (Coronal Mass Ejections) and their terrestrial impacts. This includes investigating how CMEs propagate and evolve from the corona through the heliosphere, highlighting the temporal-spatial dynamics influencing their eventual interaction with planetary bodies.
3. Energetic Particles and Space Weather: Investigating the mechanisms and locations of particle acceleration is crucial for understanding space weather phenomena. The paper emphasizes the distinction between flare-associated and CME-shock particle acceleration processes and examines the heliospheric distribution of energetic particles.
4. Solar Dynamo and Magnetic Activities: By examining high-latitude solar dynamics and magnetic field evolution, the mission aims to deepen the understanding of the solar dynamo processes. Particular focus is given to the transport and transformation of magnetic flux in polar regions, which are only partially understood under current models.

Implications and Future Prospects

The Solar Orbiter combines synchronized remote and in-situ measurements to achieve a comprehensive understanding of solar and heliospheric dynamics that has not been possible with previous missions. The data generated is expected to challenge and refine existing solar models, providing key insights into both fundamental plasma processes and accurate space weather prediction. As the mission matures, there will be continued collaboration and data exchange with NASA's Solar Probe Plus, enhancing the collective scientific yield and cementing the mission's place as a cornerstone in space physics research.

In conclusion, the Solar Orbiter mission is poised to significantly advance our understanding of the dynamic processes governing solar-terrestrial interactions through its targeted scientific inquiry and novel observational platform. This approach, uniquely combining close solar observation with out-of-ecliptic perspectives, represents a significant advancement in heliophysics.