NASA Scientific and Technical Aerospace Reports

We report further results from our ongoing assessment of magnetogram-based measures of active-region nonpotentiality
(magnetic shear and twist) and size as predictors of coronal mass ejections (CMEs). From a set of 36 vector magnetograms
of bipolar active regions (Falconer, Moore, & Gary 2004, ApJ, submitted), we have found that (1) each of our 5 measures of
active-region nonpotentiality has a 75-80% success rate in predicting whether an active region will produce a CME within 2
days after the magnetogram, (2) the correlation of each of these measures with CME production in this window is statistically
significant (confidence level greater than 95%), (3) our measure of active-region size has a 65% success rate in predicting
CMEs in this window, but (4) the correlation between active-region size and CME productivity is not statistically significant
(confidence level approximately 80%). As part of the work under our pending 2003 LWS TR&T proposal, we will double our
sample to approximately 70 active regions in order to demonstrate a statistically significant correlation between active-region
size and CME productivity, and to determine whether this correlation is a byproduct of any Sun-produced correlation between
magnetic twist and size of active regions. Since the 2002 LWS Science Workshop, we have found a measure of active-region
nonpotentiality (the length of strong-gradient neutral line) that can be measured from a line-of-sight magnetogram, and we
have generalized this measure and the corresponding measure from a vector magnetogram (the length of strong-shear neutral
line) so that they can be applied to multiple-bipole complex active regions as well as to bipolar active regions. Preliminary
results will be presented from application of these two generalized measures to our sample of bipolar active regions and to
a new sample of multiple-bipole active regions.
Author
Coronal Mass Ejection; Magnetic Signatures; Polar Regions
20040050559 Science Applications International Corp., San Diego, CA, USA, Massachusetts Inst. of Tech., MA, USA
A Search for Solar Sources of High-Speed Solar Wind Streams
Mikic, Zoran; December 16, 2002; 3 pp.; In English
Contract(s)/Grant(s): NAG5-7967; No Copyright; Avail: CASI; A01, Hardcopy
This report covers technical progress during the third and fourth years of Subcontract No. 5710000474, ‘A Search for
Solar Sources of High-speed Solar Wind Streams,’ between Science Applications International Corporation (SAIC) and the
Massachusetts Institute of Technology (MIT), covering the period November 2000 to December 2002. This is a subcontract
originating from NASA SR&T Contract NAG5-7967 with MIT. In the following sections we summarize our progress during
this reporting period.
Author
Solar Wind; Streams
20040050568 Science Applications International Corp., San Diego, CA, USA
Understanding the Solar Sources of In Situ Observations
Riley, Pete; Mikic, Zoran; Linker, Jon; Zurbuchen, Thomas H.; June 21, 2002; 5 pp.; In English; Proceedings of the Solar
Wind 10 Meeting, 16-21 Jun. 2002, Pisa, Italy; Original contains black and white illustrations
Contract(s)/Grant(s): NAG5-7967
Report No.(s): SAIC-02/8019:APPAT-308; Copyright; Avail: CASI; A01, Hardcopy
The solar wind can, to a good approximation be described as a two component flow with fast, tenuous, quiescent flow
emanating from coronal holes, and slow, dense and variable flow associated with the boundary between open and closed
magnetic fields. In spite of its simplicity, this picture naturally produces a range of complex heliospheric phenomena, including
the presence, location, and orientation of corotating interaction regions and their associated shocks. In this study, we apply a
two-step mapping technique, incorporating a magnetohydrodynamic model of the solar corona, to bring in situ observations
h m Ulysses, WIND, and ACE back to the solar surface in an effort to determine some intrinsic properties of the quasi-steady
solar wind. In particular, we find that a ’layer‘ of approx. 35,000 h n exists between the Coronal Hole Boundary (CHB) and
the fast solar wind, where the wind is slow and variable. We also- derive a velocity gradient within large polar coronal boles
(that were present during Ulysses rapid latitude scan) as a function of distance from the CHB. We find that nu = 713 km/s
+ 3.2 d, where d is the angular distance from the CHB boundary in degrees.
Author
Solar Corona; Solar Wind; In Situ Measurement; Magnetic Fields; Coronal Holes
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