JOINT CDS/MDI/SUMER PROGRAMME

Connection between Transition Region Lines and the Photospheric Magnetic Field

Per Maltby & Olav Kjeldseth-Moe ITA, University of Oslo, Richard A. Harrison, RAL, Klaus Wilhelm, MPI-Ae, & Philip H. Scherrer, Stanford University.


Scientific Justification:
The state of the solar plasma located in the transition region, is likely to be controlled by the magnetic field penetrating the region. Knowledge about the magnetic field in the transition region is scanty and confined to the sunspot region. Accordingly, the connection between transition region line characteristics and the magnetic field thus has to be based on measurements of the magnetic field at photospheric heights.

It has been argued Schrijver (1990) that a point to point comparison of transition region line intensities and the photospheric magnetic field is not physically meaningful. Recently, Brynildsen, Kjeldseth-Moe, & Maltby (1994, 1996) have studied the quiet Sun relation between the C IV resonance line parameters and the photospheric magnetic field with a spatial resolution of 1''x 1''. They ordered the material into groups according to the magnitude of the magnetic flux density |B|, calculated conditional probabilities and found that redshifted profiles with either high intensity, large Doppler shift, or large line broadening occupy an increasing fraction of the area when |B| increases. These results were contrasted by blueshifted profiles which indicated a slight decrease with increasing magnetic flux density.

Further studies of the connection between transition line parameters and the photospheric magnetic field are required in order to explore the potential of the conditional probability calculations and study in detail the connection between transition region lines and the photospheric magnetic field, both in the quiet Sun and in active regions.

References:
Brynildsen, N., Kjeldseth--Moe, O., & Maltby, P. 1994, Proc. Third SOHO Workshop, ESA SPC--373, 413
Brynildsen, N., Kjeldseth--Moe, O., & Maltby, P. 1996, ApJ (in press)
Schrijver, C. J. 1990, A & A, 234, 315


No additional text was submitted for this proposal.