Working Group Descriptions
Organizers: Bin Chen (CfA) and Stephen White (AFRL)
Radio and X-ray emissions are both sensitive to non-thermal electrons accelerated in solar flares. They complement each other in providing multifaceted diagnostics of the flare energy release, particle acceleration and transport processes. In recent years, solar radio observing techniques have been undergoing a major advance, evolving from either imaging at limited numbers of spectral channels or total-power dynamic spectroscopy toward true radio dynamic imaging spectroscopy, thanks to new instruments such as the impending completion of the Expanded Owens Valley Solar Array, the enhanced VLA, CSRH, ALMA, LOFAR, MWA and others. These radio observations, while combining with RHESSI’s imaging spectroscopic data in X-ray, provide exciting new insights into the physics of flares. This working group focuses on joint radio and X-ray analysis, both observational and theoretical. We encourage presentations that emphasize, but not limited to, the use of radio/X-ray imaging and spectroscopy data. We will also discuss outlooks for new scientific potentials and new challenges (in, e.g., data analysis and modeling) as the four-dimensional observational data are becoming available.
Organizers: Joel Allred (GSFC)
Flares increase emission in virtually all regions of the electromagnetic spectrum, and there is much to be learned by considering the mechanisms and locations where this increase is produced. For example, thermal X-rays in observed in many large flares indicate a significant amount of superhot (> 30 MK) coronal plasma, but it not yet known how this plasma is heated to such temperatures.
- Is plasma heating a result of direct heating by reconnection processes?
- If so, can that be used to constrain reconnection and acceleration models?
- How does the thermal response to flare-accelerated ions differ from that of flare-accelerated electrons?
- Are return currents important contributors to flare heating?
- What is their role in superheating the corona? Enhanced white light emission is seen in many flares and is likely formed deep in the solar atmosphere. How is flare energy transported to such depths?
- Similarly, what are possible mechanisms for the production of photospheric phenomena such as sunquakes?
- How does the chromosphere respond to flare heating?
- Are models for chromospheric evaporation consistent with observations?
- Can the cold thick-target model accurately account for these phenomena?
These questions are simply meant as examples of the types of investigations we will discuss in this working group. We invite both modeling- and observationally-driven contributions exploring the thermal response of the solar atmosphere to flare heating.
Organizers: Eduard Kontar (Glasgow U.) and Nicolas Bian (Glasgow U.)
Solar flares are efficient accelerators of electrons and ions. Hard X-ray, gamma-ray
and radio emission are main signatures of accelerated particles.
However, the details of acceleration mechanism(s) in flares are not understood.
The group aims to discuss the recent progress on diagnostics, theory and modelling of particle acceleration and solicits contributions aiming to improve our understanding of particle acceleration processes. Comparisons of models/theory with X-ray observations from RHESSI and radio observations are particularly encouraged.
Given sufficient interest, we plan to put existing acceleration models to test. Using plasma and magnetic field parameters from a well-observed flare (or a set of observations), the participants of 'acceleration challenge' will be invited to test their favourite acceleration model(s) to reproduce the observed properties of energetic particles emphasising assumptions required to explain X-ray and radio data.
Given sufficient interest, we plan to put existing acceleration models to test. Using plasma and magnetic field parameters from a well-observed flare (or a set of observations), the participants of 'acceleration challenge' will be invited to test their favourite acceleration model(s) to reproduce the observed properties of energetic particles emphasising assumptions required to explain X-ray and radio data.
Organizers: Albert Shih (GSFC) and Gerry Share (UMD)
Ions from solar eruptive events are observed directly in solar energetic particle events and indirectly through the secondary nuclear gamma-ray lines, pion-decay emission, and neutrons. This group will discuss these observations in the context of acceleration processes related to flares and CME shocks and theories of gamma-ray and neutron production. Contemporary gamma-ray data from RHESSI, Fermi, and INTEGRAL, as well as archival data from earlier missions, will be discussed, along with SEP observations. New observations by Fermi/LAT have revealed hours-long high-energy (>~100 MeV) emission in over 25 events whose origin is yet to be explained. Nuclear spectroscopy and imaging add crucial information to understand the origin of these events. We will also discuss recent observations of neutrons in the inner heliosphere and at 1 AU, energetic neutral atoms, and terahertz emission that relate to ion acceleration. We anticipate that these discussions will lead to new scientific objectives that will require new instrumentation and missions.
Organizers: Haimin Wang (NJIT) and Chang Liu (NJIT)
The magnetic field in the solar atmosphere is the ultimate energy source that powers solar flares and regulates their dynamic evolution. For example, it is believed that magnetic reconnection is the key process that converts the magnetic energy into thermal energy of the hot plasma and nonthermal energy of accelerated particles. How this process takes place remains puzzling. In the past decade, imaging and/or spectroscopic observations by RHESSI in X-rays, by SDO/AIA and Hinode/EIS in EUV, by OVSA/VLA in radio, together with instruments covering other wavelengths have provided us critical new clues to magnetic reconnection and the role of magnetic fields in solar flares in general. This session invites observational and modeling contributions on a broad range of phenomena that can link flare dynamics to the magnetic field variations in space and time. Examples include but are not limited to: (1) coronal X-ray, EUV, and radio emission in the vicinity of the magnetic reconnection region or current sheet, (2) microwave observations that can provide coronal magnetic field measurements, (3) magnetic field reconfigurations, from the corona to the photosphere, before, during, and after flares, and (4) the potential role of such reconfigurations in generating sun-quakes.
Organizer: Lindsay Glesener (UC/Berkeley)
What new instrumentation is needed in order to further investigate particle acceleration and energy evolution in solar flares? What novel technology and instruments are newly available, and which are on the horizon? This session invites abstracts concerning general technologies and specific instruments related to any of RHESSI’s primary science interests. This could include, for example, hard and soft X-ray or radio instruments for studying flares, but any instrument that could augment RHESSI’s science is welcome to the discussion. Depending on submissions, the session will be organized either as a series of talks or as a panel discussion. In either case, the opportunity to show slides will be given.