Proposed Joint Observing Program 006

Ester Antonucci, 1994 June 3

Mass, Energy, and Momentum Input tn the Solar Wind

JUSTIFICATION

The primary scientific goals of the observing program are the following:

to identify and characterize the coronal sources of the solar wind, and
to identify and understand the dominant physical processes that accelerate the solar wind.

The first goal of the investigation is to identify definitively the sources of non-transient high speed wind and of low speed wind, and to characterize the physical conditions of the different sources of solar wind at the base of the corona, as well as their evolution throughout the corona up to a few solar radii. The recent Ulysses data on solar wind are clearly showing a strong variations of the wind properties as a function of latitude, as expected, and a peculiar wind speed behavior above the streamer belt. Active regions have been recently proposed as possible sources of wind by Uchida et al. (1992) on the basis of the observations of the Soft X-ray Telescope on Yohkoh which suggest a continuous expansion of the coronal loops with a non negligible mass and magnetic field contribution to the wind. It is therefore crucial to obtain a detailed description of the physical conditions of the wind and its boundary conditions at the solar surface in correspondence to high-latitude sources such as coronal holes, to streamers at middle latitude and their interface region with the surrounding atmosphere, to the quiet sun and to active regions.

The second goal consists in using the physical parameters of the solar wind region and its boundary at the solar surface to identify the dominant acceleration mechanisms, for example to determine the roles of thermal pressure gradients (Parker type wind), wave-particle interactions, and non-thermal electrons in accelerating the solar wind in the different regions. We also aim to distinguish between the effects of waves which damp in the lower corona (acoustic waves, fast mode MHD waves) and waves which survive to heat and accelerate the solar wind beyond the critical point.

In summary, this program is aimed to:

determine the mass input and energy and momentum deposition in the solar wind for:
- Coronal Holes
- Streamers
- Quiet Sun
- Active Regions
test the hypothesis/observation of Uchida of mass input from Active Regions, and
distinguish between thermal models and models requiring momentum deposition in the extended corona.

OBSERVABLES

extended corona (UVCS, LASCO)
- determine electron temperature, kinetic temperature (non-thermal + thermal broadening of line profiles) for protons and heavier ions, electron density, outflow velocity of the corona from the limb up to 3 solar radii, in the solar wind region.
inner corona (CDS, EIT, SUMER, MDI) - determine :
- electron density and temperature
- differential emission measure on disk near the limb and possibly up to 1.4 R_Sun
- non-thermal velocity maps in
  - transition region
  - coronal lines
- fine (2") magnetic structures in the potential solar wind sources (at least at the beginning of the tracing of the target).

It is desirable to begin to observe the target regions, in the inner corona, a few days before arrival at the limb, to fully characterize the potential solar wind sources. The coronagraphs shall start the joint observation when the target is approaching the west limb, continuing for the period of visibility at the west limb.

Targets:			CH, AR, Streamers, QS (West limb)
Other Satellites:		YOHKOH/SXT
Ground Based:			white light coronagraphs, polarization
				in the corona, radio

PROPOSED UVCS OBSERVATIONS

The UVCS observations consists of two rasters A and B in sequence, to be repeated.

RASTER A

Channel I: Ly a profile

Channel II: OVI, Si XII intensity

Channel III: VL polarized 4500-6000 .

To determine electron density, proton kinetic temperature, outflow velocity.

Initial instantaneous F.O.V. 40' x 14" at 1.5 R

to the limb

centered at the target latitude

Pixel 14" x 14" Ly a channel

60" x 60" OVI channel

Spectral resolution 0.28 , Ly a channel

0.74 , OVI channel

Average dwell time

(variable with height)

F.O.V. stepped by 4 x 14"

up to 3.24 R

Total time 5 h

RASTER B

Channel I: e scattered Ly a profile (wings), Fe XII profile

Channel II: OVI, Si XII profile, Mg X, Ly a

Channel III: VL polarized 4500-600

To determine e temperature, kinetic temperature, density, outflow velocity.

Initial instantaneous F.O.V. 40' x 1.4' at 1.5 R

to the limb

centered at the target latitude

Pixel 5' x 1.4' Ly a channel

5" x 7" OVI channel

Spectral resolution 1.65 , Ly a channel

0.1 , OVI channel

Dwell time 1 h

F.O.V. stepped by 0.4 R

up to 3.0 R

Total time 5 h

Total time Raster A + B 10 h

Repeat Raster A + B.