Long-Lasting Solar Coherent Radio Bursts and Implications for Solar–Stellar Connection

When (times in MT)
Wed, Nov 30 2022, 2pm - 1 hour
Event Type
Sijie Yu
Building & Room
Virtual & CG1-3131

Discoveries of exo-auroral radio emission in the last two decades have led to an ongoing paradigm shift––many highly circularly polarized intense radio bursts detected in a variety of low-mass stars are likely signatures of auroral activities rather than flare-driven magnetic activities. Such discoveries have opened a new window in probing the magnetic field in stellar/substellar/exoplanetary systems. One of the outstanding challenges in discerning the two scenarios is characterizing the aurora-generating magnetic topologies of the stellar/substellar objects despite their large distances. Thanks to its proximity, the Sun provides much of the detailed context to study radio bursts similar to those in the stellar/substellar regime. A recent imaging spectroscopy observation with the Jansky VLA reveals a new type of radio bursts near a sunspot, which resembles exo-auroral radio emission in the literature both temporally and spectrally. Unlike the planetary aurora scenario, the detected radio signature is identified as electron cyclotron maser (ECM) emission from a sunspot driven by energetic electrons accelerated in flare activities. Comprehensive observations of sunspot auroral radio emissions will not only advance our understanding of the fundamental physical processes of ECM emissions on the Sun but also impose broad implications on stellar/substellar physics and exo-space weather sciences. These efforts will require long-term monitoring by a solar-dedicated, broad bandwidth radio telescope capable of imaging the Sun in dual circular polarization with a high image dynamic range and subsecond time resolution, which is still lacking. In this talk, after a brief introduction to ECM emissions from stars and the Sun, I will discuss the technical requirements in order to make a leap forward in observations of aurora-type ECM emissions from the Sun, and the expected science returns from a superior broadband radio imaging spectropolarimetry capabilities of a next-generation radio heliograph, such as the Frequency Agile Solar Radiotelescope (FASR) concept.

About the Speaker

Dr. Sijie Yu received his B.Sc. in Geophysics from the University of Science and Technology of China in 2010, and completed his Ph.D. in Astrophysics from the National Astronomical Observatories, Chinese Academy of Sciences in 2015. Dr. Yu joined the solar radio group at the New Jersey Institute of Technology (NJIT) as a Postdoctoral Fellow in 2016. He was appointed as a Research Assistant Professor at NJIT in June 2020. Dr. Yu’s research interests focus on energy release in different solar activity levels. As a team member of the Expanded Owens Valley Solar Array (EOVSA), he is one of the main developers of EOVSA data calibration and imaging pipeline. He is also a key team member for commissioning Jansky VLA for solar observing at P and C band with ultrafast dump rates.