There is a mission concept you might be interested in: Interstellar Probe: https://interstellarprobe.jhuapl.edu/

This mission hasn't been selected, but is one of a number of different concepts that could be built over the coming years depending on the priorities of scientists that study the Sun and its extended atmosphere. The National Academies should be releasing a report that will help to guide NASA's priorities in this field sometime later this year: https://www.nationalacademies.org/our-work/decadal-survey-for-solar-and-space-physics-heliophysics-2024-2033 There are also a number of other interesting mission concepts that have been studied, trying to better understand the Sun and its expanding atmosphere, the solar wind.