Solar Physics at UCLan

1. Solar Physics at UCLan Dr Barbara Bromage Centre for Astrophysics University of Central Lancashire CDS meeting September 2005

2. Robert Walsh Mike Marsh (postdoc) Jane Noglik (Ph.D.student) Barbara Bromage Steve Higgins (postdoc) Stephen Chapman (Ph.D.student) Martin Birch (part-time Ph.D.student) Current Players CDS meeting September 2005

3. Two main areas of study at UCLan: • Loops/Active Regions are Hot Stuff! • Coronal Holes are Cool! But far from inactive… movie by EIT instrument team

4. Coronal Holes are Cool! • They are the source of the fast solar wind and also some slow solar wind near the boundaries. • They exhibit plume structures (very cool!) and macrospicules (cooler). • They contain many bright points (not cool). • They present us with some puzzles…. CDS meeting September 2005

5. Some of the Puzzles • How can the large N-S-aligned coronal holes rotate “rigidly” when the field lines in the corona have their footpoints in the differentially rotating photosphere? • How does the open field of a polar coronal hole move from one pole to the other during the solar cycle when the underlying magnetic flux moves from equator to pole? • What happens at polarity reversal to complete the establishment of the new polar holes and does the total open flux remain constant at this time? • What mechanism generates the fast solar wind? CDS meeting September 2005

6. Topics of Interest • Magnetic reconnection between open and closed field lines. This will leave the same number of field lines but the connectivity between footpoints changes, resulting in the replacement of closed field regions by open field (coronal hole) and v.v. Does this explain “rigid rotation” ? • Polarity reversal and changes in open flux. How does the total flux change from cycle to cycle? • Plumes, interplume regions and the solar wind. • How does the coronal hole solar cycle relate to the magnetic cycle? CDS meeting September 2005

7. The Differing Corona near Times of Solar Minimum & Solar Maximum CDS meeting September 2005

8. Recent/Current Work • Statistical study of coronal hole boundary regions (Raju, Bromage, Chapman and Del Zanna, A&A ,2005). CDS meeting September 2005

9. 24 Observations of Coronal Hole Boundaries CDS meeting September 2005

10. Recent/Current Work • Statistical study of coronal hole boundary regions (Raju, Bromage, Chapman and Del Zanna, A&A ,2005). • Study of coronal hole area using SYNOP, with new method of estimating the background. • Modelling of large-scale evolution of coronal holes (with Duncan Mackay). • Short-timescale study of the boundaries to measure quasi-instantaneous rotation period, and to compare the transition region network structure to the evolution of the boundary (JOP176), looking for effects of magnetic reconnection. • Use of JOP176 together with EISCAT observations of ensuing geomagnetic effects. CDS meeting September 2005

11. Trans-equatorial Coronal Holes – Skylab (1973) and Soho (1996) • In the approach to solar minimum, coronal holes such as these are long-lived, rotating quasi-rigidly at the equatorial rotation rate. It is possible to predict when they will cross the meridian (and become geo-effective). The associated fast solar wind streams compress the magnetopause and initiate geomagnetic substorms. CDS meeting September 2005

12. So, What Do We Need CDS For? • Looking for effects of magnetic reconnection, such as temperature enhancements and flows. • Looking at variation in structure at different temperatures/heights in the solar atmosphere. • Determining abundances/FIP effects as a tracer of solar wind CDS meeting September 2005