JOP 195: Characterization of Fast and Slow Solar Wind Source Regions

Version: 2007 September 08

Authors:

Mari Paz Miralles, Enrico Landi

Participating instruments and points-of-contact (POCs):

Scientific Objectives and Justification:

We propose to study the sources of fast and slow solar wind by investigating how the flux tubes change from a high-speed to a low-speed region. We will select a polar hole with a clearly-defined streamer region nearby and study both regions and the boundary between the polar coronal hole and the surrounding quiet Sun region from the limb to SOHO/UVCS heights. We aim to measure how the plasma physical properties change between the two wind regions, and with height, and how the flux tubes expand with heliocentric distance. In particular, this campaign will study the evolution of the transition from fast to slow wind source regions as a function of time and heliocentric distance from the limb and will provide important experimental constraints to theoretical models.

The present campaign will advance previous studies (e.g. Cranmer et al. 1999; Strachan et al. 2002; Landi et al. 2007) by examining the fast and slow source regions and its transition as follows:

• centering the field of view on the boundary between the coronal hole and the quiet Sun
• using a much larger set of spectral lines
• extending the study to 2-4 solar radii above the limb.

Operational Considerations

The target will be selected by M. P. Miralles, at least, 3 days prior to the start of the UVCS observation and will be communicated to the other instruments involved. E. Landi will be in Japan and will coordinate EIS and SUMER sequences.

SOHO/UVCS will run this campaign from Nov 6 to 17, 2007. We will run a joint SUMER/EIS/UVCS observation coincidental with this time period.

Detailed Observing Sequences:

SOHO/SUMER and Hinode/EIS will observe the same field of view at several positions outside the solar limb up to the maximum distance allowed by their pointing systems. Hinode/EIS observations will consist of several repetitions of a single sequence: a 25-step raster with the 2" slit that will observe the entire EIS wavelength range downloading the central 400" of the EIS slit. The exposure time is 150 s and this study (which lasts about 1 hour and has a data rate of ~53kbit/s) will be repeated at a few locations at different heliocentric distances from the solar limb. We expect to run it 7 times for a total of around 7 hours. The SOHO/SUMER sequence will also take around 7 hours to complete.

The SOHO/UVCS sequence will last longer. The center of the UVCS slit will be at the same position angle of the EIS and SUMER observations lower down. SOHO/UVCS will observe a set of temperature and outflow diagnostic lines (including O VI and H I Lyman alpha) with a range of exposure times at higher heights.

We are planning to repeat the Hinode/EIS and SOHO/SUMER sequences at least twice during the campaign between Nov 6 and Nov 17, 2007.