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Proposal ID Metcalf_131

Date of Proposal



Lockheed Martin Solar and Astrophysics Laboratory

Lockheed Martin Missiles and Space
Advanced Technology Center
Dept. H1-12, Bldg. 252
3251 Hanover Street
Palo Alto, CA 94304




We would like to request joint observations with EIT during October 1997.

Alex Pevtsov is scheduled to observe at NSO/SP using the Advanced Stokes
Polarimeter from October 1 through October 12, 1997 (15:00 to 23:00 UT each
day). The goal of the project ("Separator Models of Coronal Loops" by
A.A. Pevtsov and D.W. Longcope) is to study temporal evolution of non-flaring
coronal loops and photospheric magnetic fields in conjunction with the
separator model of the coronal loops. In brief, we will use ASP vector
magnetograms (2 per hour) to compute separator field lines and study their
time evolution, energy output etc. We will compare these computed separators
with the coronal loops observed by Yohkoh and by EIT/SOHO. We intend to use
such a comparison to test the adequacy of the separator theory.

We propose the following EIT observations if possible:

During the period 15:00 to 23:00 each day during the Sac Peak observing run we
would like 171 and 195 subfield images of a selected active region with a 15
+\- 5 minute cadence

171,195 ... 15 minutes ... 195,171 ... 15 minutes ... 171,195 ... etc

The order of the 171,195 combination reverses each 15 minutes to minimize the
number of sector changes. We understand that this sequence will be
interrupted periodically for synoptic full disk observations.

The region to be observed will be selected during the campaign, but 24 hours
notice will be given. A new target may be selected each day, but the target
will remain the same throughout the day for ease of coordination with EIT and
SXT. The size of the EIT subfield should be sufficient to cover the selected
active region over the Sac Peak observing day.

The campaign will be organized by Alex Pevtsov and he will make the target
selections based on the magnetic field data. To test the separator model, we
need to make observations close to the disk center. So, the selected active
region will be within +/- 40 degrees from the central meridian. If there is
no active region, but, say, a weak bipolar magnetic field with an X-ray source
above, we will try to observe those. To observe a weak field without a sunspot
requires a correlation tracker, and very good atmospheric conditions. So, if
there is no active region and/or "seeing" is bad the observations for a day
may be cancelled.

The EIT data will be reduced and analyzed by Tom Metcalf and Jim Lemen at
Lockheed Martin Solar Astrophysics Lab (EIT co-I institution).

< br>Alex Pevtsov (
Dana Longcope (
Tom Metcalf (

Jim Lemen


Active Regions


Separator Models of Coronal Loops

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