Newsletter
 Front Page
 Scientific Ops
 Engineering
 Software
 Results
 Gallery
 Atlas
 Press
 Links
 Project
 Newsletter
  » Latest
  » Science
  » Calibration
  » Operations
  » Past Issues
 Copyright
Issue 4: 12th December 2001
A Note from the Editor and Contents

Welcome to the CDS Newsletter. The goal of this Newsletter is to inform the CDS user community of
  • current CDS science topics
  • developments in CDS data analysis
  • instrumental matters
  • operational issues
The Newsletter is updated monthly. We invite your contributions on CDS-related matters: data analysis, science results, instrument calibration, software and questions on these topics. Your responses will influence the content of future issues. Please send newsletter inputs and correspondence to: fludra@cdso8.nascom.nasa.gov

This Month's Topics:

Quiet Sun Workshop Summary

Clare Parnell

Recently a workshop entitled 'The Quiet Sun: Transient Events and Coronal Heating' was held at MEDOC in Paris. Approximately, 25 known participants attended although on the first day we started off with a few extras! The aim of the meeting was to understand the relationships between the many reported quiet Sun transient events, e.g. explosive events, network flares, blinkers, etc. In particular, to determine whether all these types of phenomena are just manifestations of the same event detected by different techniques in different wavelength bands, or whether they are fundamentally different? To do this participants were encouraged to analyse particular named data sets. Each of the named data sets contained CDS data. Furthermore, since CDS can observe in chromospheric, transition region and coronal wavelengths it was particularly useful for comparing observations in these regions.

The results from the workshop strongly suggest that the SOHO/CDS EUV transient brightenings, blinkers, network and cell brightenings are all the same phenomena just observed using wide slit, rastered and single slit data, respectively. However, various members of the workshop have agreed upon a strategy to confirm (or deny) this.

There was also an animated discussion as to whether CDS blinkers were simply made up of many SUMER brightenings and SUMER explosive events. There was certainly some evidence that this may well be the case and work has started to find specific cases where a CDS blinker occurs directly above an explosive event observed in SUMER. Although there was a good data set where both SUMER and CDS were observing the same area, the SUMER slit, which was longer than the CDS slit, showed its greatest activity outside the CDS field of view!

A number of other discussions took place covering jetting phenomena and network flares/heating events/nanoflares. Further details of the workshop and the conclusions can be found on the following website.


Solar Cycle Observations with SOHO CDS - Implications for Coronal Heating

Carl Foley

A widely used diagnostic tool for coronal heating enthusiasts has been the measurement of the coronal temperature, and its variation with height in the corona and along coronal loops. Previous work has generally found that the coronal temperature increases as a function of height above the limb and along the loops. This has demonstrated a requirement for heating up to and including the maximum observed height range of almost 2 solar radii. More recently Aschwanden & Nitta., (2000) have demonstrated that heating at heights above the first gravitational scale height (a few x 10Mm) is not required, and the observed positive temperature gradient may simply be a result of the superposition of many flux tubes of different temperature which are heated at their base.

CDS now allows us to view the relative distribution of individual ions as function of height in the corona. This enables us to examine the distribution of plasma in many regions and structures. The Grazing Incidence Spectrometer (GIS) of CDS is operated in a photon counting mode. This allows events to be discriminated by pulse height, thereby allowing cosmic ray hits to be excluded from the accumulated spectra. The GIS is therefore able to obtain deep exposures relatively free of cosmic ray background far off limb.

In a recent paper (A&A in press) Foley, Patsourakos, Culhane, & Mackay 2001 we evaluate the relative abundance of Fe IX through Fe XV ions for coronal streamers observed close to the solar minimum and maximum of the current solar cycle (23), on 1996 July 8 and 1999 August 5 respectively. The most abundant (adjacent in Te) ions were then used to establish the best representation of the apparent temperature profile with height. The derived temperature profile and its variation from solar minimum to maximum are used to infer how the corona evolves and its associated energy requirements. For comparison we have also included solar maximum data for cycle 22 (1992, October 3) obtained from Yohkoh observations which were the basis of Priest et al., 1998, 2000. A figure from this paper is displayed below and highlights the difference in the coronal temperature between solar minimum and maximum.

The temperature of the cores of coronal streamers over the solar cycle.

Using SUMER data, Schuhle et al. (2000), found that the emission from the transition region (TR) increased by a factor of 2 from solar minimum to solar maximum. Classical models of the Transition region for the quiet Sun (e.g., Gabriel 1976) indicate that TR radiative losses are powered from the coronal conductive flux from the overlying corona. The enhanced transition region emission reported by Schuhle et al. (2000) is consistent with the increase of the coronal temperature over the solar cycle which we observe and present here.

Evolution of the sun in the EUV as recorded by the FSUN observations over the rise of the current solar cycle

The variation of the Sun's irradiance was covered in issue 1 of the CDS newsletter. To prodce the irradiance full sun spectral scans were obtained (FSUN) on a regular (monthly) basis. The evolution of the Sun as recorded in these observations are displayed above for Mg IX and Fe XVI. From these observations we can see that the major evolution of the sun in the EUV is associated with the active region emission. Over time the active regions emission appears to become more extended as more sunspots emerge and migrate to lower latitudes.

During this time period the magnetic field associated with these active regions is transported to the surrounding quiet sun (and ultimately the polar regions) by the Sun's meridional flow. This is illustrated below in the synoptic map produced from Kitt Peak magnetograms over the rise of the current solar cycle (courtesy of Duncan Mackay and Karen Harvey).

Synoptic map of Kitt Peak Magnetograms over the rise of the current solar cycle.

This process supplies and replenishes the quiet sun magnetic field and dictates the characteristic emergence of features over the solar cycle such as high latitude streamers and low latitude coronal holes.

GIS SPECT_1 observations of the quiet sun over the rise of the current solar cycle.

Synoptic observations of the quiet sun have been obtained on a regular basis with the Grazing Incidence Spectrometer. The dramatic effect of the transport of magnetic flux is characterised by more than an order of magnitude enhancement observed in the flux of Fe XV and XVI. This is consistent with the offlimb temperature measurements which we discuss above.

These observations together support the hypothesis that the positive temperature gradients which we observe are real and not due to the effect of supersition of different isothermal flux tubes with different scale heights. The solar cycle evolution of the transition region emission is a result of the increased energy deposition into the overlying corona over the cycle.




GIS Slit Anomaly - Alternative GIS Studies

Carl Foley

Whilst the problem with the slit mechanism is resolved it is still possible to perform observations with the GIS which do not move in the N-S direction, which are either sit and stare observations or simple E-W scans. A strength of using the GIS is that it is operated in a photon counting mode. This allows photon events to be discriminated by pulse height, thereby allowing cosmic ray hits to be excluded from the accumulated spectra. The GIS is therefore able to obtain deep exposures relatively free of cosmic ray background. An example of this is illustrated below for an offlimb observation made with both the NIS (top row), and GIS (bottom row) on the 5th August 1999. This observation was of the base of a coronal Streamer as delineated in the LASCO C2, MLSO, EIT 284 A, composite image.

(top panel) Composite image formed from (outer) LASCO C2, MLSO MK 4 Coronagraph, EIT 284 A - The region delineated illustrates the CDS region of interest
(middle panel- label NIS) NIS Spectral images of the base of the indicated streamer base
(bottom panel- label GIS) GIS Spectral images of the region above the NIS observations. The interesting feature in this plot is the
Fe XI which emission appears to dominate at the edge of the streamer where the field is expected to be open (arrowed)

I have summarized studies which are ok to run whilst the slit anomaly problem is resolved here. The GEWS3 studies, are ideal for off limb observations and can be used in sequence with careful pointing to map large off field regions as is illustrated in the figure above.


Study NameNo.VardurStudy Name
GIMCP_1 1134.0000GIS MCP TEST PART 1
GIMCP_2 2134.0000GIS MCP TEST PART 2
TEST1_I 413649.00GIS FIRST LIGHT TEST
TEST1_II5110033.0GIS FIRST LIGHT TEST - 2ND PART
TEST1CH15210033.0CORONAL HOLE FIRST LIGHT TEST
TEST1III61661.000GIS FIRST LIGHT TEST - 3RD PART
TEST1_S2813649.00COMMISSIONING TEST USING SLIT 2
TEST1AR282407.000GIS TEST1 ACTIVE REGION
TEST1CH220110031.0GIS TEST1 CORONAL HOLE
ICAL2_1 281673.000INTERCAL 2 PART 1
TGRAD_1N5012035.00TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 1, NEW
TGRAD_1N502335.000TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 1, NEW
TGRAD_2 51118033.0TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 2
TGRAD_2 5121833.00TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 2
TGRAD_3 52140021.0TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 3
TGRAD_1X5412035.00TEMP GRADIENT IN CH PHASE 1 - MODIFIED
TGRAD_2X62118033.0TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 2, 2X240 SLIT
TGRAD_2X6221833.00TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 2, 2X240 SLIT
TGRAD_3X64140021.0TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 3, 2X240 SLIT
TGRAD_3X6424021.00TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 3, 2X240 SLIT
TGRAD_3X6438021.00TEMPERATURE GRADIENT IN A CORONAL HOLE - PHASE 3, 2X240 SLIT
TEST1_I26811829.00GIS SIT-AND-STARE 4''X4''
GLONG 6911829.00GIS SIT-AND-STARE 2X240''
CHROM_G47314211.00CHROMOSPHERIC OSCILLATIONS : ALL CHANNELS GIS
BROAD 80110126.0LINE BROADENING WITH ALTITUDE
GIBOUND 8412549.00GI LONG SLIT CH BOUNDARY STUDY
GISAT44S8426149.00GIS LONG SLIT ATLAS - 4X4 ARCMINUTES
HTBNDWE 851541.000CORONAL HOLE BOUNDARY STUDY (W-E)
HTBNDWE 852542.000CORONAL HOLE BOUNDARY STUDY (W-E)
G2AL 9112035.00GIS ACROSS THE LIMB, 4X4 SLIT
G2AL 9128035.00GIS ACROSS THE LIMB, 4X4 SLIT
GEAST 9214021.00GIS CORONA ABOVE THE EAST LIMB, 2X240 SLIT
GWEST 9314021.00GIS CORONA ABOVE THE WEST LIMB, 2X240 SLIT
CHMAP_A 981173.000POLAR CORONAL HOLE MAPPING - PART A
CHMAP_A 982175.000POLAR CORONAL HOLE MAPPING - PART A
G2AL4 9836082.00GIS ACROSS THE LIMB, 4X4 SLIT, 240''X4'' AREA
G2AL4 98412082.0GIS ACROSS THE LIMB, 4X4 SLIT, 240''X4'' AREA
HTBNDSS11001690.000POLAR CORONAL HOLE BOUNDARY - SIT & STARE
HTBNDSS11002691.000POLAR CORONAL HOLE BOUNDARY - SIT & STARE
EWSCAN 10513023.00GIS E-W SCAN, 40''X4'', 4X4 SLIT
EWSCAN 10521023.00GIS E-W SCAN, 40''X4'', 4X4 SLIT
EWSCAN 1053323.000GIS E-W SCAN, 40''X4'', 4X4 SLIT
GISAT_S 1191522.000GIS LONG SLIT ATLAS
GEAST2 12814010.00GIS CORONA ABOVE THE EAST LIMB, 2X240 SLIT V.2
GEAST3 12914010.00GIS CORONA ABOVE THE EAST LIMB, 2X240 SLIT V.3
GIS2SIN 1311212.000GIS SINGLE EXPOSURE 4''X4''
GIS2SIN 1312512.000GIS SINGLE EXPOSURE 4''X4''
GIS2SIN 13131012.00GIS SINGLE EXPOSURE 4''X4''
GWEST3 15314010.00GIS CORONA ABOVE THE WEST LIMB, 2X240 SLIT V.3
GWEST2 15414010.00GIS CORONA ABOVE THE WEST LIMB, 2X240 SLIT V.2
GWEST2S 15614010.00GIS CORONA ABOVE THE WEST LIMB, 2X240 SLIT V.2 (SOUTH 120 ARCSEC)
EWGSCAN2158112046.0W-E 120X4 ARCSEC SCAN WITH SLIT 4X4 ALL LINES GIS
GLOW_1 170114410.0GIS LOW TELEMETRY MODE STUDY - OFF LIMB
HRBNDWE 17911106.00CORONAL HOLE BOUNDARY STUDY (W-E), HIGH RATE
SITNSTAR1821540.000SIT 'N STARE AT ONE POINT
GIS_TEST202111660.0GIS LONG DURATION TEST
HTGIWE 21412089.00CORONAL HOLE BOUNDARY STUDY (W-E), MEDIUM RATE
GEXSNS 216112.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216220.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216330.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216440.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216550.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216650.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216740.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216820.0000GIS EXTENDED CORONA SIT N STARE
GEXSNS 216912.0000GIS EXTENDED CORONA SIT N STARE
G2EW3 22214583.00GIS EAST-WEST, 4X4 SLIT, 180''X4'' AREA
O_SPOT1022512750.00SUNSPOT 3-MINUTE OSCILLATIONS
GSS250W 22613995.00GIS TIME SERIES, 250 EXPOSURES
POINT_EW2381101.000E/W POINTING TEST
GIWEMT1 2431550.000SIT-AND-STARE AND MOVE STUDY (W-E)
GIWEMT2 24411060.00SIT-AND-STARE AND W-E SCAN
CDSCD 2501325.000CDS CORONAL DYNAMICS
CDSCD 2502321.000CDS CORONAL DYNAMICS
GCD5 2511145.000GIS CORONAL DYNAMICS
GEWS3 2521360.000GIS EAST-WEST SCAN (SLIT3)
GEWS3 2522660.000GIS EAST-WEST SCAN (SLIT3)
GEWS3 2523960.000GIS EAST-WEST SCAN (SLIT3)
GEWS3 25241260.00GIS EAST-WEST SCAN (SLIT3)







From the CDS Operations Management Team in the Space Science & Technology Department at CCLRC Rutherford Appleton Laboratory
Site maintained by John Rainnie.
Last revised on Tuesday (11/Dec/2001) at 22:57.