What can He II 304 A tell us about transient seismic emission from solar flares?

C. Lindsey, A. C. Donea

Research output: Chapter in Book/Report/Conference proceedingConference PaperResearch


After neary 20 years since their discovery by Kosovichev and Zharkova, the mechanics of the release of seismic transients into the solar interior from some flares remain a mystery. Seismically emissive flares invariably show the signatures of intense chromosphere heating consistent with pressure variations sufficient to drive seismic transients commensurate with helioseismic observations-under certain conditions. Magnetic observations show the signatures of apparent magnetic changes, suggesting Lorentz-force transients that could likewise drive seismic transients-similarly subject to certain conditions. But, the diagnostic signatures of both of these prospective drivers are apparent over vast regions from which no significant seismic emission emanates. What distinguishes the source regions of transient seismic emission from the much vaster regions that show the signatures of both transient heating and magnetic variations but are acoustically unproductive? Observations of acoustically active flares in He II 304 A by the Atomospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO) offer a promising new resource with which to address this question.

Original languageEnglish
Title of host publicationFine Structure and Dynamics of the Solar Atmosphere
Subtitle of host publicationProceedings IAU Symposium No. 327, 2016
EditorsSantiago Vargas Domínguez, Alexander G Kosovichev, Patrick Antolin, Louise Harra
Place of PublicationCambridge UK
PublisherInternational Astronomical Union
Number of pages4
ISBN (Print)9781107170049
Publication statusPublished - 1 Jan 2016
EventInternational Astronomical Union Symposium 327, 2016: Fine Structure and Dynamics of the Solar Atmosphere - University of Cartagena, Cartagena de Indias, Colombia
Duration: 9 Oct 201614 Oct 2016

Publication series

NameProceedings of the International Astronomical Union
PublisherCambridge University Press
ISSN (Print)1743-9213


ConferenceInternational Astronomical Union Symposium 327, 2016
Abbreviated titleIAUS 327
CityCartagena de Indias
OtherThe scientific goal of this symposium is to discuss recent results on the processes shaping the structure of the solar atmosphere and driving plasma eruptions and explosive events. Activity of the solar atmosphere entails numerous multi-scale processes. State-of-the-art solar instrumentation is revealing the dynamics of the Sun with unprecedented temporal and spatial resolutions. Together with advanced numerical simulations these investigations are making new steps in our understanding of the complex dynamical structure of the solar atmosphere.

Major unsolved problems of astrophysics such as how the solar corona is heated and how the solar wind and heliosphere are powered have their roots in the origin of small-scale magnetic fields constituting the Sun's 'magnetic carpet' in the photosphere and appearing as 'magnetic canopy' in the chromosphere. The questions whether the small-scale fields of the quiet-Sun atmosphere represent remnants of the large-scale field generated by the global dynamo in the deep convection zone or these fields are a product of a near-surface local dynamo and how the energy of the small-scale field is transported through the chromosphere and converted into heat and high-speed flows in the chromosphere-corona transition regions have been topics of hot debates. While the numerical simulations have demonstrated in principle the existence of the local dynamo processes on the Sun their role in the small-scale magnetism of the solar atmosphere remains unclear. Recent discoveries from space missions, rocket experiments, and large-ground based telescopes of fine-scale magnetic loops result in the paradigm change in our understanding of the structure, energetics and dynamics of the solar atmosphere, transition region and corona. In the new picture emerging from the observations and numerical simulations the solar atmosphere appears as highly dynamical multi-scale conglomerate of interacting magnetic loops, magnetized vortex tubes and jets. The mean quiet-Sun field strength is only few Gauss, but locally in the small-scale structures it can reach the kilogauss strength dramatically affecting thermodynamic and dynamical properties of the photospheric and chromospheric plasma. In addition, substantial progress has been made in studying the fine structure of sunspots and active regions. The high-resolution observations reveal the sunspot dynamics in unprecedented details, and raised new questions about the role of the fine structuring in the formation and stability of large-scale magnetic structures. The new observations demonstrate that the atmospheric structure and dynamics of the quiet and active Sun are considerably more complicated than the traditional spectroscopic models.

The understanding of the fine structure and dynamics of the solar atmosphere requires a considerable coordinated effort of observers, theorists and experts in realistic numerical simulations. The proposed symposium is very timely and important. It will make an important step in the big international effort for our understanding of the solar atmosphere with large telescopes and detailed modeling. The Symposium will provide a forum for discussion of the recent advances, and a platform for developing new coordinated observing and theoretical programs. This Symposium will be of great interest also for the IAU Divisions studying stellar atmospheres, starspots, exoplanetary systems, and developing advanced observational techniques and theoretical models.
Internet address


  • Chromosphere
  • Helioseismology
  • Magnetic fields
  • Sun: Flares
  • UV radiation

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