Flying through the Venus magnetotail: The Dungey-V mission for the ESA F3 call

The Venus magnetotail is highly dynamic, much more so than was previously expected. Indeed, many scientists in this field still consider it to be relatively stable; however, our measurements by the Analyzer of Space Plasmas and Energetic Atoms (ASPERA-4) instrument, developed by the Swedish Institute of Space Physics (IRF) on Venus Express (VEX), along with many other instruments on VEX, Solar Orbiter, BepiColombo, and Parker Solar Probe, reveal its dynamic nature. While ions in the magnetotail generally flow away from the planet, ASPERA-4 frequently measured a "return flow", a global ion flow pattern in the tail directed toward Venus. The plasma process that alters the flow direction is still unknown. Magnetic reconnection and its associated phenomena were identified experimentally, but the link to the return flow is another key open question to understand convection in the Venusian magnetotail. No global numerical model has reproduced this large-scale convection in the induced magnetotail of Venus, emphasizing the lack of current knowledge about this phenomenon

The Dungey-V mission concept aims to answer the following science questions.

• How does the ion return flow impact the global energy, momentum, and mass flow at Venus?
• What is the fate of the ions in the return flows and reconnected magnetic flux?
• How does the magnetic reconnection process work with the draped field?

The Dungey-V spacecraft will be inserted into a heliocentric orbit and conduct at least 10 flybys of Venus. A flyby mission concept would prove more beneficial than an orbiter for multiple reasons:

• Controlled flybys will allow exploration of various tail regions in the magnetotail, not easily achieved with an orbiter.
• Observing dynamic processes requires advanced instrument suites capable of high-time resolution measurement (~100 ms). Such measurements will create a large data volume; however, the flyby mission provides opportunities for data downlink when the spacecraft is close to Earth, simplifying telemetry requirements.
• A flyby mission, with no orbit insertion or maintenance, requires significantly less delta-V than an orbiter. This makes it possible to use a smaller, simpler and, hence, cheaper platform.

The Dungey-V instrument suite will include ion spectrometers, electron spectrometers, a magnetometer, electromagnetic wave analyzers, and a nightglow camera, subject to future trade-off. The innovation of this mission concept is the very high time resolution for plasma measurements, never achieved before near Venus. This capability is comparable to that of state-of-the-art terrestrial magnetospheric missions (e.g., MMS), which have provided extensive insight into Earth’s magnetosphere. Given the unique nature of Venus as the only truly non-magnetized terrestrial magnetosphere, we expect similarly significant scientific insights from Dungey-V.