On November 2, the research by PhD candidate CHEN Yuhao, Prof. LIN Jun from Yunnan Observatories (YNAO), and other co-authors was published in The Astrophysical Journal Supplement Series. The study investigates the probability of the Parker Solar Probe (PSP) crossing the core region of energy release during solar eruptions, known as Coronal Mass Ejection (CME)-flare current sheets (CSs). Quantitative studies on the probability of traversal were conducted, assessing the dependence on the orbital parameters of PSP and similar spacecraft. This research provides theoretical backing for future in-situ detection of CME-flare CSs by the Solar Close Observations and Proximity Experiments (SCOPE).
Solar eruptions are among the most impulsive phenomena in the solar system. Prof. LIN Jun, in collaboration with his advisor Prof. Terry Forbes, established the Lin-Forbes model, which foresaw the presence of a CS between the CME and solar flare. Within the CS, magnetic reconnection serves as the core engine driving energy release during solar eruptions. While this model has gained broad recognition over the last two decades, supported by substantial observational evidence confirming the existence of CME-flare CS, our comprehension of magnetic reconnection processes inside the CSs remains limited. Classical theories indicate that CSs in the solar corona should be only tens of meters thick to facilitate rapid magnetic reconnection. However, observations have revealed that the actual thickness of CME-flare CSs can reach up to 104 kilometers, indicating a significantly more complex magnetic reconnection process than previously thought. To reveal the nature of magnetic reconnection within CME-flare CSs and resolve the thickness debate, the only viable approach is deploying a spacecraft for in-situ measurements. Presently, the Parker Solar Probe (PSP) stands as the sole spacecraft capable of this task, thanks to its close proximity to the solar corona, reaching as close as 10 solar radii.
Based on a simplified CS geometry, the researchers utilized observational data to construct a probability model to assess whether the PSP could traverse a CME-flare CS. They find that during the solar maximum, the PSP is expected to cross the CS approximately 1.4 times a year. However, it is challenging for the spacecraft to cross the CS at large angles, making it difficult for researchers to calculate the thickness of CS. To tackle this challenge comprehensively, YNAO proposed the space mission called SCOPE. According to calculations, an orbit closer to the Sun with a higher inclination would enhance CS detection. SCOPE is anticipated to approach as close as 5 solar radii with an orbit inclination of around 65°. During the solar maximum, it is estimated to traverse the CS 4 times per year, with higher probability of crossing it at larger angles.
This study offers theoretical support for the future in situ detection of CME-flare CSs, and we look forward to advanced solar observation/detection instruments enhancing our comprehension of this crucial star for humanity.
Contact:
CHEN Yuhao
Yunnan Observatories, CAS
E-mail: chenyuhao@ynao.ac.cn
