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Proposal ID Gopalswamy_161

Date of Proposal Apr 1 1998

firstname
Nat

lastname
Gopalswamy

institute
The Catholic University of America

address
Code 682.3, Bldg 26, Room G-1
NASA/GSFC
Greenbelt, MD 20771

email
gopals@fugee.gsfc.nasa.gov

phone
301-286-5885

fax
301-286-0264

proposal
The problem: Coronal holes are brighter than the quiet Sun in
cm-mm wavelength range. This is an enigmatic phenomenon with
no satisfactory explanation. We shall take advantage of the
high spatial and temporal resolution information available
from at radio and EUV wavelengths to understand the
structure and variability so that it can be related to other
dynamical processes in the coronal hole.

We shall derive the expected brightness temperature of the
elephant trunk coronal hole at 17 GHz from SOHO EIT and CDS
observations obtained during the
Whole Sun Month campaign in August - September, 1996 and compare
the results with the observed brightness
temperature by the Nobeyama Radioheliograph. We shall use the EIT
304 images to determine the location of the radio enhnacement with
respect to the structure seen in the upper chromosphere/transition
region. The results of the comparison will be used to evaluate the
models of the chromosphere and lower transition region that include
cross-field thermal conduction.

Bright points seem to be abundant in the coronal holes where
the radio enhancement is observed. We shall explore the possible
role of bright points in explaining the radio enhancement of
coronal holes as a possible signature of heating in the upper
chromosphere/lower transition
region. We shall use simultaneous observations obtained
by the Nobeyama radioheliograph and SOHO/CDS to study the
time variability of the radio enhancement and its correspondence
in the CDS data.

We shall use SOHO/MDI data to determine the magnetic structure
associated with the radio brightness enhancement. EIT 304 and
one or more of the coronal line (EIT 195, 171, 284)
to determine the vertical structure of the coronal holes,
starting from the photosphere (MDI) upper chromosphere (microwave), transition
region (EIT 304), and corona (EIT 195).

Co-Investigators:

K. Shibasaki (Nobeyama)
B. Thompson (NASA/GSFC)
J. Gurman (NASA/GSFC) and
C. DeForest (Stanford)

inside_collab
J. Gurman

consortium
no

topic
Coronal Holes

topic

title
Microwave Brightening in Coronal Holes: Structure and Variability


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