urn:ieda:metadataabout:10.15784-600152
eng
dataset
Dataset
Interdisciplinary Earth Data Alliance
web@usap-dc.org
http://www.usap-dc.org/static/imgs/header/usaplogo.png
logo graphic
pointOfContact
2018-05-17
ISO 19139 Geographic Information - Metadata - Implementation Specification
2007
Tomographic Imaging of the Velocity and Magnetic Fields in the Sun's Atmosphere
2016
publication
doi:10.15784/600152
Jefferies, Stuart M.
Maui Scientific Research Center, 590 Lipoa Pkwy, Ste 262, Kihei, HI, 96753, U.S.A.
stuartj@msrc.unm.edu
author
U.S. Antarctic Program (USAP) Data Center
publisher
Abstract: The ultimate goal of this project is to determine the structure and dynamics of the Sun's atmosphere, assess the role of MHD waves in heating the chromosphere/corona and driving the solar wind, and better understand how the Sun's atmosphere couples to the solar interior. As the solar atmosphere is 'home' to many of the solar phenomena that can have a direct impact on the biosphere, including flares, coronal mass ejections, and the solar wind, the broader impact of such studies is that they will lead to an improved understanding of the Sun-Earth connection.
Under the current award we have developed a suite of instruments that can simultaneously image the line-of-sight Doppler velocity and longitudinal magnetic field at four heights in the solar atmosphere at high temporal cadence. The instruments use magneto-optical filters (see Cacciani, Moretti and Rodgers, Solar Physics 174, p.115, 2004) tuned to the solar absorption lines at 422 nm (Ca I), 589 nm (Na D2), 770 nm (K) and 1083 nm (He). These lines sample the solar atmosphere from the mid-photosphere to the high-chromosphere.
A proof-of-concept run was made in the Austral summer of 2007/2008 using the Na and K versions of the instruments. Here we recorded over 40 hours of full-disk, intensity images of the Sun in the red and blue wings of the Na and K Fraunhofer lines, in both right- and left-circularly polarized light. The images were obtained at a rate of one every five seconds with a nominal spatial resolution of 4 arc-seconds. The run started at 09:44 UT on February 2, 2008 and ended at 03:30 UT on February 4, 2008.
Data Quality Assessment:
The temperature controls of the instrument housings were unable to fully compensate for the harse Antartic winds encountered during the observing run. This led to large (~15 C) temperature swings which adversely affected the instruments (and thus data quality) in two ways: 1) Crystals of Na and K were deposited on the magneto-optical filter windows leading to "hot spots" in the images. These "hot spots" come and go with time as the temperature changes. 2) The changing temperature caused the optical rails to contract and expand causing the final images to go in- and out-of-focus, thus reducing the resolution to greater than 4 arc-seconds. Both these effect are worse in the K data.
Despite these problems, the intensity images can be combined to provide magnetic images that show a very high sensitivity (< 5 Gauss in a 5 second integration).
Data Description:
The raw data are stored as a series of 1024x1024x4 FITS images. The format is: blue image (left circulary polarized light), blue image (right circularly polarized light), red image (left circulary polarized light), red image (right circularly polarized light).
The naming convention for the images is: Type_Instrument_Day_hour_minutes_seconds
where Type is I (intensity), F (flatfield), D (dark)
Instrument is 0 (Na), 1 (K)
Day is the day number from the beginning of the year where January 1 is day 0
For example, I_0_32_12_34_40.fits is an intensity image taken with the Na instrument at 12:34.40 UT on February 2, 2008.
Notes:
1) The flatfield images were acquired by moving a diffuser in front of the Sun during the integration. The resulting images therefore have to be corrected for residual low-spatial frequencies due to the non-flat nature of the light source.
2) Each FITS file header contains a variety of information on the observation, e.g.,
F_CNTO : number of summed frames in each 5 second integration (*)
FPS : Camera frame rate (Frames Per Second)
FLIP : Rate at which the half-wave rotator (magnetic switch) was switched
INT_PER : Integration time (in seconds)
MOF : Temperature of magneto-optical filter cell
WS : Temperature of wing selector cell
TEMP_0 : Temperature of camera 0
TEMP_1 : Temperature of camera 1
TEMP_2 : Temperature inside instrument (location 1)
TEMP_3 : Temperature of narrowband filter
TEMP_5 : Temperature of magnets surrounding MOF cell
TEMP_6 : Temperature inside instrument (location 2)
TEMP_7 : Temperature of housing for magnetic switch
(*) This is the frame count for the camera. The number of frames in each image for the two different polarization states, is half this number.
The measured temperatures are only coarse measurements.
3) Due to reflection in the final polarizing beam splitter (which separates the "red" and "blue" signals into the two cameras), the camera 1 data need to "reversed" along the x-axis (i.e. listed as [1024:1] instead of [1:1024])
4) Line-of-sight velocity and magnetic field images are generated from the observed intensity images. Doppler images as (red-blue)/(red+blue), magnetic images as the difference between the Doppler images
for right- and left-circularly polarized light.
funderName:NSF:GEO:PLR:Antarctic Astrophysics and Geospace Sciences
awardNumber:0632399
awardTitle:Tomographic Imaging of the Velocity and Magnetic Fields in the Sun's Atmosphere
Complete
Jefferies, Stuart M.
Maui Scientific Research Center, 590 Lipoa Pkwy, Ste 262, Kihei, HI, 96753, U.S.A.
pointOfContact
Antarctic Astrophysics and Geospace Sciences
program
Sun
subject
Satellite Remote Sensing
IEDA data type categories
IEDA integrated catalog keyword vocabulary
2017-10-11
creation
Antarctica
IEDA feature of interest
IEDA integrated catalog keyword vocabulary
2017-10-11
creation
Cosmos
IEDA topic
IEDA integrated catalog keyword vocabulary
2017-10-11
creation
US Antarctic Program Data Center (USAP-DC)
Data Center
Creative Commons Attribution-NonCommercial-Share Alike 3.0 United States [CC BY-NC-SA 3.0]
Creative Commons Attribution-NonCommercial-Share Alike 3.0 United States [CC BY-NC-SA 3.0]
eng
geoscientificInformation
2006-03-29
2010-03-31
http://dx.doi.org/10.15784/600152
WWW:LINK-1.0-http--link
Landing Page
Link to DOI landing page or data facility landing page if no DOI is assigned.
information
http://www.usap-dc.org/view/dataset/600152
WWW:LINK-1.0-http--link
landing page
Link to a web page related to the resource.
information
This metadata record was generated by an xslt transformation from a DataCite metadata record; The transform was created by Damian Ulbricht and Stephen M. Richard. 2017-11-15 these records include new IEDA keywords for geoportal facets Run on 2018-06-21T19:05:25-07:00
metadata curator
maintenance.contact@email.org
processor