Trans-continental Coronal Observing Network

(including an appeal for collaborators on polarization observations)

From: Frederic Clette

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CONTACT PERSON: Frederic Clette (fred@oma.be)

INTITUTIONS: Royal Observatory of Belgium (ROB)

    Joint Organisation for Solar Observations (JOSO)

LOCATION: TECONet (Trans-European Coronal Observing Network): France to India

Reference stations :
- Niederbronn-les-Bains, France Long: -07d39m, Lat: +48d58m, Alt: 250m
- Rimnicu-Vilcea, Romania Long: -24d22m, Lat: +45d06m, Alt: 100m

ECLIPSE TIMES:

START : 10h20m UT

END : 11h40m UT for European segment, 12h35m UT for India

Reference stations :
- Niederbronn-les-Bains, France Mid-totality : 10h31m UT
- Rimnicu-Vilcea, Romania Mid-totality: 11h03m UT

GOAL OF OBSERVATIONS:

- absolute determination of the electron density distribution from 1 to 3-4 solar radii

- morphology of coronal magnetic fields

- temporal evolution of structures and of electron density in the low corona (flows, CMEs, rotational parallax)

- SOHO joint observations:

- comparison of plasma parameters (electron density, temperature) at the base of corona (with EIT).
- cross-calibration and extension to higher altitudes (with LASCO C2).
- dynamical studies, with determination of density changes: flows and CME evolution, if an event occurs in the 2-hour window covered by the network (with EIT and LASCO C2).

TYPE OF OBSERVATIONS:

- white-light polarimetry using photography and CCD cameras.

- coordinated observing network (about 25 stations) distributed in longitude, across Europe, and beyond, in Iran and India.

SOHO OBSERVATIONS REQUIRED:

- - EIT: synoptic images around totality time :

- minimum: two synoptics sets in all 4 bandpasses, around 10h30m UT and 11h30m UT
- if possible: full-resolution FeXII (195 A) images at 15-min cadence or better (down to 5 min), from 10h00m UT to 12h40m UT. If there are telemetry limitations, 2 by 2 binning should be used to keep a reasonable cadence. (Make sure that the telemetry buffer is almost empty before starting the "eclipse" sequence)

- - LASCO: C2 white-light polarization sequences (pB)

- minimum: two sets , around 10h00 UT and 11h00 UT
- if possible: additional sets at 12h00 UT and 14h00UT

- - MDI: full-disk magnetograms (hourly)

In France, we will be using a new 12-bit digital CCD camera, 1024^2 pixels, 8 im/s, for polarimetric measurements

For more details, see the JOSO TECONet page : http://joso.oat.ts.astro.it/htm/WG7-Activities.htm

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TECONet 99 - A trans-European Coronal Observing Network

An initiative of JOSO and the ROB (Royal Observatory of Belgium)

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At the occasion of the August 11, 1999 total solar eclipse, JOSO's Working Group 7 has initiated a new project which would make use of the international platform offered by JOSO to bring together all observing teams that are planning to carry out white-light polarimetric measurements during the 1999 August 11 total solar eclipse. WG7's action would consist in coordinating stations that are distributed along the whole path of totality across Europe and the Middle-East, and prompting the formation of an analysis working team that would take charge of the subsequent data-processing work.

WHO CAN PARTICIPATE TO THE OBSERVING NETWORK?

First, those who are already preparing a polarimetric experiment are invited to join the project, to extend the significance of their work. In addition, anyone who is willing to undertake this kind of scientific experiment is also welcome. This includes experienced amateur eclipse chasers as well as professional teams, or even a mix of both.

WHAT IS THE EXPECTED SCIENTIFIC RETURN?

Combining many observing stations basically means increasing the number of good data sets acquired under clear skies (which we wish to everybody !). Moreover, as the stations will be distributed along the totality band, the time differences between observations (up to 1 h 30 min) will allow coronal dynamics studies by tracking any change in the images over much longer durations than the 2-min totality experienced at a single location (3-D reconstruction by solar rotation, coronal mass ejections, flow speeds, etc.).

WHAT ARE THE BASIC INSTRUMENTAL REQUIREMENTS?

In order to keep the equipment simple, inexpensive and thus accessible to amateurs and professionals with limited budget, and also to ensure some homogeneity of the various data, some prerequisites have been defined :

Detector: black & white photography (Kodak Tmax 400) CCD camera (digital output)

Bandpass: white-light, broadband

Field of view: 1.0-1.15 to 2.5-4.0 solar radii for 35mm film: focal length between 0.7 and 1.2 meter for CCD chips: typically, focal length from 200 to 400mm

Spatial resolution: 10 arcsec or better

Polarimetry: linear polarisation filter on an indexed rotating mount (minimum of 3 positions 60 degrees apart), focal filter or full-aperture filter

Calibration: if possible, solar disc exposures outside totality through a metal-on-glass filter with a known transmittance. Very high-resolution images in unpolarized (total) intensity with the same spatial coverage can also be included. The above rules and principles should contribute to one of the primary aims of the network: producing data sets that can be directly compared in a quantitative way, using the same analysis procedure.

WHAT KIND OF HELP WILL BE PROVIDED BY JOSO?

JOSO will act as an information "node" for network coordination :

- - practical help:

- forwarding contact requests to the appropriate people

- searches for an observing site - support for custom clearance (intercession with local authorities)

- - technical help:

- observing tips, instrument design, equipment suppliers

- definition of a standard observing procedure

- delivery of identical film rolls, containing laboratory calibration pre-exposures, to all photographic teams.

JOSO will prompt the formation of a professional data analysis group, on a voluntary basis, as only the subsequent interpretation and publication of the data will make the whole TECONet concept meaningful. However, JOSO cannot provide funding or equipment to participating teams, except for polarizer sheet filters, when necessary, and rolls of film.

HOW TO CONTRIBUTE TO THE SCIENTIFIC ANALYSIS?

JOSO will prompt the formation of a professional data analysis group, on a voluntary basis, as only the subsequent interpretation and publication of the data will make the whole TECONet concept meaningful.

Two fundamental tasks must be emphasized:

- - the digitization of photographic material: scanning micro-densitometer devices are needed, as well as people to run them.

- - the reduction and merging of data from different origins.

This announcement is also a call for support in the analysis, in the solar physics community, who want to volunteer for this essential work, which will lead to joint publications with international authorship.

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