The origin of 3He-rich solar energetic particles

• Applicant: Dr. Radoslav Bucik, Ph.D.
• Subject Area: Astrophysics and Astronomy
• Term: from 2015 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 278164843

Hydrogen and 4He, the most abundant elements in the Sun, are poorly accelerated in solar flares. Instead, very rare elements, the lighter helium isotope 3He and ultra-heavy nuclei, get easily accelerated. For example, energetic 3He is tremendously enhanced up to four orders of magnitude. These 3He-rich solar energetic particles (SEPs) present one of the most extreme fractionation examples in astrophysics. The production of these puzzling particles and their escape from the Sun is the issue we want to address in this project. Extreme ultraviolet (EUV) jets, recently associated with some 3He-rich SEP events, suggest that reconnection between closed magnetic loops and adjacent open field lines is the primary mechanism responsible for the particle acceleration and escape into interplanetary space. The observed monotonic heavy-ion enhancement increase with mass-to-charge ratio is in conflict with the enhancement of the lighter helium isotope, 3He, and is not sufficiently explained. Gyro-resonant interaction with different plasma waves, generated directly by magnetic reconnection and by electron beams is the most plausible ion acceleration mechanism. To achieve the goal of this project we will employ a unique approach, possible only in recent years, since multiple spacecraft and full-Sun, high-cadence EUV images became available along with in-situ energetic-ion observations. Specifically, with multi-point remote-sensing and in-situ observations aboard the twin STEREO and the near-Earth ACE and SDO spacecraft we will examine for the first time (1) the temporal properties of 3He-rich SEP sources when multiple spacecraft are consecutively connected to the same region on the Sun; (2) the spatial properties of 3He-rich SEP sources when multiple spacecraft are simultaneously connected to the same solar region via interplanetary and coronal field lines.

• DFG Programme: Research Grants
• International Connection: USA
• Cooperation Partners: Glenn M. Mason; Dr. Mark E. Wiedenbeck