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Joan Burkepile

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Joan Burkepile Powered By Docstoc
					Joan Burkepile is a Project Scientist III. She received her degree in Physics from the University of Colorado, Boulder
in 1983 and joined the High Altitude Observatory in July 1983. She studies Coronal Mass Ejections (CMEs), and the
evolution of the solar corona. She is the Instrument Scientist for the Mauna Loa Solar Observatory

Current Research:




  Changes in the total mass, brightness, and structure of the corona are due to changes in the energy
  deposited into the atmosphere by the Sun’s magnetic field. Changes in the energy input into the lower
  solar atmosphere over the solar activity cycle, drive changes in the base density and temperature of the
  corona which in turn account for the variations in the structure , brightness and mass in the corona
  between activity minimum and maximum. At left: Plot of estimated mass in the low corona (1.2 to 2.2
  solar radii) as a function of time over nearly 3 solar cycles as recorded by the Mauna Loa Mk3 and Mk4
  K-coronameters. The coronal mass peaks during times of maximum solar activity (~1990, ~2000). At
  right: two images of the solar corona recorded by the Mauna Loa K-coronameters; one at solar
  maxiumum activity in 2000 (left), and one at solar minimum activity (at right) in 2009.




Publications:

1. Burkepile, J.T., Science Requirements of the COSMO K-coronagraph, 2010, COSMO Tech Note
#16.
This technical note describes the scientific requirements of the K-coronagraph which is part of
the COronal Solar Magnetism Observatory (COSMO). COSMO is a proposed facility dedicated to
studying coronal and chromospheric magnetic fields and their role in driving solar activity such
as coronal mass ejections (CMEs). COSMO is comprised of 3 instruments: a 1.5 m coronagraph
to study coronal magnetic fields; a chromospheric and prominence magnetometer; and a K-
coronagraph designed to study the formation of CMEs and the density structure of the low
corona. To meet these goals, the COSMO K-coronagragh needs to acquire images of the white
light corona in polarization brightness down to 1.05 solar radii (R‫ )סּ‬with a time cadence of 15
seconds to brightness levels of 10-9 B‫ סּ‬at a signal-to-noise level of one. This technical note
outlines the science drivers for the K-coronagraph. The major goals are: 1) to understand the
formation of coronal mass ejections (CMEs) and their interaction with surrounding coronal
structures and related activity (e.g. flares, prominence eruptions and shock waves); 2) identify
Earth-directed CMEs (e.g. halos) in realtime, 3) determine the density distribution of the corona
over solar cycle time scales; and 4) measure the radial brightness gradients beyond 1.5 R ‫ סּ‬in
magnetically open regions. The COSMO K-coronagraph will replace the aging Mauna Loa Solar
Observatory (MLSO) K-coronameter which has been in operation since 1980.



2. Thompson, W.T., K. Wei, J.T. Burkepile, J.M. Davila, O.C. St.Cyr, 2010, Background Subtraction
for the SECCHI/COR1 Telescope Aboard STEREO, Solar Phys., 262, 213

Abstract: COR1 is an internally occulted Lyot coronagraph, part of the Sun Earth Connection
Coronal and Heliospheric Investigation (SECCHI) instrument suite aboard the twin Solar
Terrestrial Relations Observatory (STEREO) spacecraft. Because the front objective lens is
subjected to a full solar flux, the images are dominated by instrumental scattered light which
has to be removed to uncover the underlying K corona data. We describe a procedure for
removing the instrumental background from COR1 images. F coronal emission is subtracted at
the same time. The resulting images are compared with simultaneous data from the Mauna Loa
Solar ObservatoryMk4 coronagraph.We find that the background subtraction technique is
successful in coronal streamers, while the baseline emission in coronal holes (i.e. between
plumes) is suppressed. This is an expected behavior of the background subtraction technique.
The COR1 radiometric calibration is found to be either 10 – 15% lower, or 5 – 10% higher than
that of the Mk4, depending on what value is used for the Mk4 plate scale, while an earlier study
found the COR1 radiometric response to be ∼20% higher than that of the Large Angle
Spectroscopic Coronagraph (LASCO) C2 telescope. Thus, the COR1 calibration is solidly within
the range of other operating coronagraphs. The background levels in both COR1 telescopes
have been quite steady in time, with the exception of a single contamination event on 30
January 2009. Barring too many additional events of this kind, there is every reason to believe
that both COR1 telescopes will maintain usable levels of scattered light for the remainder of the
STEREO mission.
 Figure Caption: A Comparison of polarized brightness measurements made by the MLSO Mk4
 (black) with those from COR1-A (red) and COR1-B (blue), as a function of position angle at
 various radial distances. Each scan is an average over 0.2 solar radii. The dashed lines
 represent fits to the COR1 data to best match the Mk4 values over most of the range. The fits
 have been smoothed for ease of reading. Sample error bars represent the radiometric
 uncertainty for each telescope.




3. Frazin, Richard A., Alberto M. Vasquez, William T. Thompson, Philippe Lamy, Antoine
Llebaria, Joan Burkepile, David Elmore, Russ Hewett, Farzad Kamalabadi, Intercomparison of
the STEREO, SOHO and MLSO Coronagraphs and the POISE Eclipse Instrument, Submitted to
Solar Phys., 2011

Abstract. Shown are quantitative comparisons between polarized brightness (pB) and total
brightness (B) images taken by the following white-light coronagraphs: COR1 and COR2 on
STEREO, C2 on SOHO, and the ground-based MLSO-Mk4. Both the initial and final calibrations of
C2 are discussed. The data for this comparison were taken on April 16 2007, when both STEREO
spacecraft were still within 3.1◦ of Earth’s heliographic longitude, affording essentially the same
view of the Sun for all of the instruments. Generally, the agreement between the instruments is
best in bright streamer structures due to the difficulties of estimating stray light backgrounds in
COR1 and COR2 and the sky polarization in Mk4. The background subtraction is more effective
for pB than it is for B in COR1, while the opposite is true for COR2.




 Figure Caption: LEFT: The coronagraph images used for the intercomparisons are presented here. Upper
 left: C2, upper right: Mk4, middle left: COR1-A, middle right: COR1-B, lower left: COR2-A, lower right:
 COR2-B. In each, the log of the pB value is displayed, and the inner and outer radii are shown in Table I.
 The COR1 and COR2 images are time-averages of 7 images and 3 images respectively, taken over a 60
 minute span. RIGHT: Plots of polarization brightness at 4 coronal heights from Mauna Loa Mk4 and
 STEREO COR1 A & B inner coronagraphs.




4. McIntosh, Scott W., Joseph B. Gurman, Robert J. Leamon, Jean-Philippe Olive, Joan Burkepile,
Robert S. Markel, Leonard Sitongia, The Hightest Cosmic Ray Fluxes Ever Recorded: What
Happened to the Earth’s Deflector Shield?, Submitted to Astrophys. J., 2011

Abstract: The summer of 2009 saw the largest cosmic ray flux ever measured at 1 AU. Observed
by neutron monitors, this solar minimum flux was 6% larger than that of the last solar minimum
in 1996 and 4% larger than the previous high of the space age. Clearly, something dramatically
affected the cosmic ray ‘deflector shield’ of the Earth this time around, but what was it? Using a
combination of serendipitous observations made by the solid state recorder of the SOHO
spacecraft, an analysis of SOHO/MDI magnetograms, combined with SOHO/EIT and SDO/AIA
coronal imaging, we deduce that a pronounced north-south asymmetry in the meridional
circulation flow resulted in the evolution of the photospheric magnetic field into a prolonged
prevalence of negative magnetic polarity in the equatorial region that was the root cause of the
observed cosmic ray flux increase. The regional dominance of the Sunward-pointing field,
weakness and the low rigidity of the interplanetary magnetic field enabled more cosmic rays of
the energy range measured at Earth to enter our atmosphere since systematic measurements
began in the 1950s.




Figure Caption: The coronagraph images used for the intercomparisons are presented here. Upper left: C2, upper right:
Mk4, middle left: COR1-A, middle right: COR1-B, lower left: COR2-A, lower right: COR2-B. In each, the log of the pB value is
displayed, and the inner and outer radii are shown in Table I. The COR1 and COR2 images are time-averages of 7 images
and 3 images respectively, taken over a 60 minute span. RIGHT: Plots of polarization brightness at 4 coronal heights from
Mauna Loa Mk4 and STEREO COR1 A & B inner coronagraphs.


4. McIntosh, Scott W., Joseph B. Gurman, Robert J. Leamon, Jean-Philippe Olive, Joan Burkepile, Robert S. Markel,
Leonard Sitongia, The Hightest Cosmic Ray Fluxes Ever Recorded: What Happened to the Earth’s Deflector Shield?,
Submitted to Astrophys. J., 2011

Abstract: The summer of 2009 saw the largest cosmic ray flux ever measured at 1 AU. Observed by neutron
monitors, this solar minimum flux was 6% larger than that of the last solar minimum in 1996 and 4% larger than
the previous high of the space age. Clearly, something dramatically affected the cosmic ray ‘deflector shield’ of the
Earth this time around, but what was it? Using a combination of serendipitous observations made by the solid
state recorder of the SOHO spacecraft, an analysis of SOHO/MDI magnetograms, combined with SOHO/EIT and
polarity in the equatorial region that was the root cause of the observed cosmic ray flux increase. The regional
dominance of the Sunward-pointing field, weakness and the low rigidity of the interplanetary magnetic field
enabled more cosmic rays of the energy range measured at Earth to enter our atmosphere since systematic
measurements began in the 1950s.

				
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