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Issue 6: 14th May 2002
Latest News

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
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:

This Month's Topics:

MEDOC Campaign

Medoc Campaign #9 will take place 20 May - 02 June. CDS will support several observing programmes, listed on the SOHO monthly calendar at:

CDS Planning from RAL

At present, new CDS planners who are non-US citizens require an escort at GSFC, which can be restrictive both for the planner and the local GSFC personnel.

Anyone who wishes to be a CDS planner outside the periods of the Medoc campaigns, may consider planning from RAL as an alternative to travelling to GSFC. This could be a particularly convenient and cost-saving option for UK-based scientists. All first-time planners are provided training at RAL before their planning week, and local support will be given during the planning week.

Please contact Andrzej to inquire about the current planning schedule and to arrange dates.

In my experience, being a planner during your own campaign or joint observing programme offers a considerable advantage in that it affords you direct control over target selection and pointing, in response to current solar conditions. I would like to encourage everybody, particularly PhD students and post-docs, to consider this hands-on way of acquiring data for your research projects. - Andrzej Fludra

CDS User Guide

This is a reminder that the CDS User Guide is available at:


Users who find things they don't understand, or that don't work, or information that is missing, should contact a member of the RAL CDS team (for example, Dave or Andrzej). Your feedback is very important to us, as we cannot solve problems we do not know about. We will endeavour to solve any problem that is brought to our attention. - Andrzej Fludra

SOHO Archives

The User Guide also contains information on browsing and retrieving CDS data, in particular, links to SOHO archives at RAL, in the USA and France.

Here are direct addresses of these archives: - RAL - USA - France

Please note that the RAL archive and the USA archive have different interfaces. They are reasonably intuitive and include links to their respective Help files. Should you encounter an insurmountable problem when accessing the archives, please email your questions to the local archive administrator listed on each website. - Andrzej Fludra

Oscillations Above Sunspots

N. Brynildsen, P. Maltby, T. Fredvik, and O. Kjeldseth-Moe, 2002, Solar Phys., in press.

The 3 min oscillations in the sunspot atmosphere are discussed, based on joint observing with the Transition Region And Coronal Explorer - TRACE and the Solar and Heliospheric Observatory - SOHO. We find that the oscillation amplitude above the umbra increases with increasing temperature, reaches a maximum for emission lines formed close to 1 - 2x10^5 K, and decreases for higher temperatures. Oscillations observed with a high signal to noise ratio show deviations from pure linear oscillations. The results do not support the sunspot filter theory, based on the idea of a chromospheric resonator. Whereas the filter theory predicts several resonant peaks in the power spectra, equally spaced ~1 mHz in frequency, the observed power spectra show one dominating peak, close to 6 mHz. Spectral observations show that the transition region lines contribute less than 13 percent to the TRACE 171 A channel intensity above the umbra. The 3 min oscillations fill the sunspot umbra in the transition region. In the corona the oscillations are concentrated to smaller regions that appear to coincide with the endpoints of sunspot coronal loops, suggesting that wave propagation along the magnetic field makes it possible for the oscillations to reach the corona.
The manuscript is available from:

A Comparison Between Coronal Emission Lines From an Isothermal Spectrum Observed With CDS and CHIANTI Emissivities

E. Landi, U. Feldman and K.P. Dere, 2002, ApJ, in press (July 2002 issue).

The present paper compares off-disk spectral observations of the solar corona in the ranges 307-379 A and 513-633 A with theoretical emissivities calculated using the CHIANTI database. The observed spectra were recorded by the Coronal Diagnostic Spectrometer instrument on board the Solar and Heliospheric Observatory using the Normal Incidence portion of the instrument.
Using line ratio techniques, we first measure the electron temperature and density in the emitting region, verifying that it is nearly isothermal. Next, we use an emission measure analysis to compare measured spectral line intensities with predictions from the CHIANTI database.
This comparison allows us to assess the quality of the CHIANTI data for the brightest coronal lines in the 307-379 A and 513-633 A spectral ranges. As a result, we were able to 1) select lines and ions for which the agreement between theory and observation is good; 2) identify a few lines which are blended and 3) stress inconsistencies between a few lines and theory, thus showing where improvements to atomic data and transition probabilities are necessary.

Underflight Calibration of SOHO CDS by SERTS-97

R. Thomas, 2002, Proceedings of ISSI Workshop on SOHO Inter-Calibration, in press.

Flights of the SERTS sounding rocket were made in 1997, 1999, and 2000 to provide updated radiometric and wavelength calibrations for several experiments on the SOHO satellite mission. Just before or after each of these flights, end-to-end radiometric calibrations of the rocket payload were carried out using an EUV transfer standard light-source specially re-calibrated against the primary standard of BESSY I. These measurements established the absolute SERTS responsivity within a relative uncertainty of 17% over its bandpass of 30 nm to 36 nm. During the flights, SERTS and SOHO CDS observed the same solar locations, as demonstrated by subsequent data co-registration with simultaneous SOHO EIT images, allowing the SERTS calibrations to be directly applied to both CDS and EIT. Following is a brief summary of the SERTS-97 radiometric calibration and the underflight cross-calibration that it provided for the CDS NIS channels at a time shortly before SOHO's temporary loss of pointing control in 1998.

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 (22/Jan/2019) at 15:07.