Descriptions of each of the topical sessions can be found below.

Each session will include invited “scene-setting” talks followed by facilitated, open discussion on targeted science questions. This interactive format is intended to foster both broader and deeper collaboration and understanding amongst our community, to propel progress and enhance success by breaking down silos both within the high-energy solar physics and among solar and space physics in general.

Suggestions for discussion topics are solicited during registration.  Additional morning (EU) and afternoon (US) sessions will allow for presentations by early-career researchers, and posters from all interested attendees.


Topic 1: Energy storage and release – e.g., reconnection, eruption initiation

Leaders: Joel Dahlin (US), Alexander Warmuth (EU)

Solar Eruptive Events (SEEs), of which flares are a primary component, are understood to be powered by the release of magnetic energy stored in the solar corona. While reconnection is thought to play an important role in flare energy release, its role in the initiation of SEEs/flares remains hotly debated. A further challenge for present  models is the fundamental nature of so-called ‘confined’ flares that are unaccompanied by a coronal mass ejection. In this session, we aim to focus on recent and upcoming observations that can challenge and direct our modeling efforts, focusing on the following critical questions:

  • What recent or future observations can be used to test competing models for eruption initiation and fast energy release?
  • What observable parameters (e.g., magnetic configuration) influence the energy partition of solar eruptive events (e.g. flare vs. CME, thermal vs. nonthermal)?
  • How do observations constrain our understanding of reconnection energy release in flares (e.g., three-dimensional structure, turbulence, plasmoids, guide field)?
  • What signatures of “confined” vs. “eruptive” flares can direct modeling efforts to understand the fundamental physics governing whether a flare will be accompanied by a CME?


Topic 2: Energy conversion – e.g., particle acceleration (electrons and ions) and plasma heating

Leaders: Andy Inglis (US), Natasha Jeffrey (EU)

Particle acceleration is one of the fundamental physical processes occurring in the solar atmosphere, and provides key insight into the energy release process on the Sun. It is also closely associated with plasma heating and the generation of wave-like processes. Despite a wealth of research key questions regarding particle acceleration and plasma heating remain unanswered, such as:

  • When and how are particles accelerated during solar eruptions?
  • What is the connection between different accelerated particle populations (e.g., at the Sun and in-situ populations, different species)?
  • What is the balance between the energy in accelerated electrons versus accelerated ions?
  • What is the role and extent of direct heating of solar plasma versus heating via particle collisions?

This session aims to discuss these high-level fundamental questions and consider what new insights, observations, and models are needed to make progress towards definitive answers.


Topic 3: Energy transport – probing high energy solar phenomena using remote sensing and in situ diagnostics

Leaders: Sophie Musset (EU), Yeimy Rivera (US)

Solar energetic phenomena like flares and CMEs are the main sources of suprathermal particles linked to energetic particle events. However, there remain several key unanswered questions pertaining to the particle source region, and the physical mechanisms behind their acceleration and transport out of the corona. To fully capture and understand these underlying processes, it is necessary to examine and compare properties of the energetic particles at their acceleration site and throughout their propagation in the heliosphere. This session aims to discuss means of exploring and constraining drivers of high energy phenomena by integrating remote sensing and in situ measurements of energetic particles from coordinated measurements of heliospheric observatories to:

  • investigate their transport, evolution, and longitudinal extent across the heliosphere
  • probe the origin of their seed population and conditions of their acceleration region through chemical abundances, ionization states, and energetic particle spectra


Topic 4: Unified “systems science” – bridging high-energy and other solar subfields

Leaders: Bin Chen (US), Laura Hayes (EU)

This session aims to facilitate cross-disciplinary discussion between the high-energy solar physics community and other solar-heliospheric communities. Historically, high-energy sessions have often focused on X-ray and radio observations that probe energetic particles, although the community has long recognized the need for bridging other solar-heliospheric subfields to approach a unified “system science.” In light of recent developments that have utilized multi-wavelength/multi-messenger observations and data-constrained/data-driven numerical modeling, there is much opportunity to expand the scope. We encourage all contributions that address such cross-domain topics from observational, theoretical, and modeling standpoints. Some focused topics:

  • How remote-sensing observations at wavelengths other than X-ray/radio can help identify and constrain solar high-energy processes.
  • How in-situ observations from, e.g., SolO and PSP, can complement remote-sensing observations to achieve new insights into high-energy processes on the Sun and heliosphere.
  • How numerical modelings can be used in concord with observations to understand the high-energy processes.
  • How high-energy processes occur and evolve in the highly coupled solar atmosphere, solar wind, and heliosphere.
  • How high-energy processes are connected to space weather effects (e.g. ionospheric effects).


Topic 5: Plasma physics throughout the Universe – solar/astro and solar/planetary connections

Leaders: Astrid Veronig (EU), Julie Vievering (US)

In this session, we will explore the connections among high-energy phenomena in different plasma regimes throughout the universe, from the Sun and stars to planetary magnetospheres to extreme astrophysical environments. We will consider:

  • Processes: reconnection, shocks, turbulence, particle acceleration, heating, etc.
  • Conditions: density, temperature, magnetic field strength, etc.
  • What can be learned from each environment? 
    • Sun → spatially resolved structures, multiwavelength data sets
    • Planetary magnetospheres → in-situ measurements
    • Astrophysical objects → extreme environments not present within our heliosphere