This project furthered the understanding of our dynamic Sun by investigating the nature of solar flares, which are transient bursts of light from the Sun.  Specifically, the project examined the smallest observable solar flares (“microflares”) via their X-ray emission to understand how similar, or not, these flares might be to larger, well understood flares.  We also compared flares on the Sun to violent, explosive events on young stars that are just forming their planetary systems.  We furthered solar flare research and educational goals by establishing citizen science projects to involve the public in analyzing the wealth of existing data on solar flares, particularly to identify jets of plasma emerging from the Sun.

A major result of this citizen science effort was the development, launch, and publication of results from the Solar Jet Hunter project.  This project is hosted on the Zooniverse platform, which allows members of the general public to join research projects that need a large number of volunteers to analyze data.  Our project was to identify jets of plasma emerging from the Sun’s corona.  Throughout the course of the project, volunteers spotted these jets and identified their locations, times, and durations for solar jets between 2011 and 2016.  The results of this broad survey were published in a paper by Musset et al. (2024) in Astronomy and Astrophysics.

We applied our knowledge of the Sun to study similar (but larger!) processes on other stars.  Young stellar objects are newly formed stars that are still forming their planetary systems.  We measured X-rays from flares from these young stars and found that the events are basically larger versions of flares that happen on the Sun – but scaled up by many orders of magnitude!  The interaction of flares with protoplanetary disks was evident from neutral iron fluorescence observed from the disk.  These results are published in Vievering et al. (2019) in The Astrophysical Journal and in the doctoral dissertation of Dr. Juliana Vievering.

The project team undertook a thorough study of very small solar flares (“microflares”) using the Nuclear Spectroscopic Telescope Array (NuSTAR) spacecraft.  NuSTAR is the most sensitive high-energy X-ray observatory ever crafted, but is not designed to observe the (relatively bright) Sun.  Fortunately, during solar quiet times and during very small solar flares, NuSTAR’s sensitivity can be leveraged to make unprecedented observations.  The project team undertook a thorough examination of all NuSTAR solar microflares (over 100 events) and performed several case studies of individual flares.  An important conclusion is that, despite their small size, solar microflares can be powerful particle accelerators (Glesener et al. 2020 in The Astrophysical Journal; Duncan et al. 2021 in The Astrophysical Journal; Cooper et al. 2024 in the Monthly Notices of the Royal Astronomical Society).  The high-energy particles accelerated by small flares can temporarily heat the lower layers of the solar atmosphere in ways that are consistent with the heating actually observed by other observatories (Polito et al. 2023 in Frontiers of Space Sciences).  Supporting work in these areas was also performed using focused hard X-ray data from the FOXSI sounding rocket experiment (Athiray et al. 2020 and Vievering et al. 2021, both in The Astrophysical Journal).  We also performed several solar X-ray studies in the time domain, a relatively poorly studied area in solar flare physics, finding that fast time variations are prevalent in some solar flares (Knuth & Glesener 2020 in The Astrophysical Journal), and that time variations can be used effectively to isolate the different plasma populations present in solar flares, which significantly augments the information that can be gleaned from flare spectroscopy (Setterberg & Glesener, in preparation).

Over the course of this project, the grant provided partial support for 7 graduate students, 4 postdoctoral researchers, and a large number of undergraduate students.  3 PhD dissertations were partially supported by the grant.  The graduate students and postdocs presented their work at several scientific conferences and workshops to disseminate the results to the community and to provide those early career researchers with networking and collaborative opportunities.

Last Modified: 01/06/2025
Modified by: Lindsay Glesener