TITLE: Characterization of the EUV Counterparts to X-ray Bright Points

J.L.R.  Saba (MDI/Lockheed @SOHO EOF)
A. Fludra (CDS/RAL, JOP 23 leader)
R.J. Thomas (CDS & SUMER/ GSFC)
J.T. Hoeksema (MDI/Stanford)
T.D. Tarbell (MDI/Lockheed)
C.J. Wolfson (MDI/Lockheed)
K.L. Harvey (NOAO/Solar Phys. Res. Corp)
and other interested parties (to be determined).

ABSTRACT:
The proposed collaborative investigation uses high-cadence, high-resolution
(HR) MDI magnetogram, dopplergram, and intensity data, in combination with
data from coronal instruments on SoHO, Yohkoh, and, when available, TRACE,
to help identify and characterize the EUV counterparts to X-ray Bright
Points (BPs). Also sought is the more difficult goal of (a) determining the
conditions under which BPs evolve into emerging active regions, or 
(b) establishing that BPs and emerging active regions are two distinct
classes. The underlying photospheric magnetic structure and its evolution
may be key factors in BP character and persistence. Phase 1 of the project
concentrates on correlative studies of potential targets in common fields
of view, and spatial mapping and time histories of common sources in
different wavebands. In Phase 2, the spectral diagnostic power of CDS and
SUMER will be brought to bear on chosen BP targets (by use of near-realtime
commanding, or possibly by receipt of a location flag from EIT?, to move to
selected locations) to obtain plasma parameters such as density, temperature, 
emission measure, and composition. 
   This study supports SoHO JOP 23 and is complementary to JOP 1. 

TECHNICAL SUMMARY:

BACKGROUND:
X-ray Bright Points (BPs) are small (10-40 arcsecs) regions of enhanced X-ray 
emission associated with magnetic bipoles and with He I 10830 dark points 
[Harvey 1985], which have lifetimes ranging from minutes to one or more days.
About 20-30% of BPs appear to be associated with emerging flux [Webb et al.
1993], and most of the remainder with cancelling flux. Recently, 17 GHz
radio emission has been detected from some X-ray BPs, and some have been
observed to flare [Kundu et al. 1994]. 

DATA TO BE USED IN STUDY:
 - MDI data: High-resolution magnetograms, dopplergrams, and continuum 
intensity images.
 - CDS and SUMER image and spectroscopic data as specified in JOP 23.
 - Cospatial images from EIT, and TRACE when available. Images from Yohkoh 
SXT to identify X-ray BPs.
 - Supporting ground-based data (in particular, He I 10830 data to identify 
He I dark points), as specified in JOP 23.

REQUIREMENTS SUMMARY:
 - MDI data from program PLAGE, giving (full-resolution) HR magnetogram +
Dopplergram + intensity image every minute for Phase 1. Data should be 
simultaneous with coronal data due to ephemeral nature of BPs. Higher-cadence
(full-resolution) data for smaller field of view is desirable for Phase 2, 
to understand the role of flows.
 - Frequency TBD (when JOP 23 is run), Duration: 3-day intervals of about 8 
hours, if possible, but shorter periods (e.g., one 8-hr interval) also 
acceptable.
 - Solar conditions: This study should be made on a large sample of potential 
BP targets, in quiet Sun and coronal hole regions, during various levels of
activity, to see if overall solar conditions affect the results, and in a 
wide range of latitudes, to explore the distinction between active region 
and BP spatial distributions; study of BPs near active regions is also
desirable if possible. 

TYPE OF ANALYSIS:
 - Level-1 calibration of high-resolution Dopplergrams, magnetograms, and 
continuum images.
 - Potential (?) extrapolations of HR magnetograms into the corona. 
 - Coregistration of MDI data with data from other instruments. Correlative 
studies of features in different wavebands. Analysis of other data sets in 
parallel, as specified in JOP 23 (Phase 1: Morphology and time history studies; 
Phase 2: EUV plasma diagnostic studies.)

REFERENCES:
SoHO JOP 23: Bright Points (JOP leader: A. Fludra)
   (http://sohowww.nascom.nasa.gov/operations/JOPs)
Harvey, K.L., 1985 Austr. J. Phys. 38, 875.
Kundu, M. Shibasaki, K., Enome, S., & Nitta, N. 1994, ApJ 431, L155.
Webb, D.F., Martin, S.F., Moses, D., & Harvey, J.W. 1993 Sol. Phys. 144, 15.