COLLOQUIA
Mysteries of the magnetic Sun

Prof. Jack Harvey

Abstract

The Sun presents us with many unsolved mysteries. In this talk I discuss three of them that have intrigued me for the last 50 years. Solar flares are the most powerful explosions in space between here and the nearby stars. The only viable power source is stored magnetic energy. Yet definitive observations of changes in the magnetic field associated with flares have been lacking until recently. Measurements with the GONG network have helped to address this mystery and the results are surprising. Efforts to observe the weak magnetic fields in the solar photosphere date nearly to the discovery of magnetism on the Sun. Improvements in observational capabilities have made this area a 'hot' topic with many important contributions from people at the IAC. High resolution observations are clarifying many features. I will focus on the role played by lower resolution work in defining the uniformity of the still mysterious weak magnetic fields over large spatial and temporal scales. Physics changes from hydrodynamic to magnetic dominance as one moves upward from the photosphere to the chromosphere. This leads to significant and complicated changes in the magnetic field in both the active and quiet Sun. Observations of the chromospheric magnetic field show several unexpected and mysterious features. Solving these mysteries will be an exciting area as observational and spectral inversion capabilities develop.

About the talk

Mysteries of the magnetic Sun
Prof. Jack Harvey
National Solar Observatory, USA
Thursday April 29, 2010 - 0:00  (Aula)
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About the speaker

Professor Jack Harvery has more than 240 publications in refereed research journals and is the editor of three books. His Hirsch index is among the top 1% in solar physics.

He has more than 50 years of professional experience in solar research - mainly observational and instrumental and almost always in collaboration with others. His work on magnetic fields led to the discovery of the so-called internetwork field, the first direct proof that network fields are concentrated into kG flux tubes, the first Zeeman effect measurements of coronal magnetic fields and the creation of a 35-year archive of daily high-resolution solar magnetograms that are widely used in the community. He has also been heavily involved in the GONG and SOLIS instrument design and development.

In the area of solar velocity fields his work on differential solar rotation with R. Howard was a standard reference used for too many years. In helioseismology, he helped provide the first profile of solar rotation with depth over the bulk of the solar interior. One of the results from five observing trips to South Pole was the discovery that the latitude variation of rotation in the convection zone is very similar to what is observed at the surface. He led the team that designed the GONG instruments that are deployed around the world and which have collected solar oscillation data continuously since 1995 for the benefit of the community. His work on the solar chromosphere has lead to a 34-year archive of daily measurements of chromospheric features.

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