The SOI-MDI Virgo Intercomparison Team

Team Leader: D. Gough
Local Coordinator: Todd Hoeksema

Introduction

This team's major goal is to measure the lowest frequency low-degree modes of solar oscillations possible. This will be accomplished by intercalibration of the VIRGO and SOI-MDI data and by joint analysis of the resulting data sets. A similar effort is underway in conjunction with the GOLF team on SOHO.

A poster paper was presented at the 181st IAU Colloquium in Nice, France in October, 1996 describing the current status of the data.

MDI averages full disk velocity and continuum intensity data into 180 bins each minute as part of the continuous structure (5K) program. These bins subdivide the 12 + 4 pixel VIRGO-LOI detector mask. The bins are symmetric about the equator and central meridian. There are 45 unique shapes in each quadrant; the number of CCD pixels in each of the 45 bins is given here. In addition, 24 hours of these data are stored on board and transmitted at each tape dump for increased continuity. This is the most continuous time series produced by SOI/MDI. During the 2-month SOI-MDI Dynamics program the circular LOI buffer is downlinked twice a day.

It took some time to determine and upload the proper scaling parameters in order to bring down the data with the proper precision. The current velocity parameters were uplinked on day 1215 (30 April 1996); preliminary intensity codes were uplinked on the same day and then updated on day 1238 (May 23). The proper scaling brings down the intensity data with 18 bits of precision rather than 16. The LOI Ic bins are corrected before averaging with the onboard flat field correction.

You can see sample daily plots of both quantities.

Early examples of the daily plots of the 180 pixels in Continuum Intensity are available for May 22 , May 21, and May 19, 1996. The noisy intervals on May 21 and 22 were due to a spacecraft roll and to a momentum management manouevre.

To retrieve data from the DSDS you may want to know that the 60s and 30s data product codes (DPCs) are 03027005 and 03427005 for velocity and 07057007 and 07457007 for intensity.

Report from the September 1995 SOI-MDI Team Meeting

The Virgo intercomparisons team did not meet separately at the SOI Team Meeting. However as a follow-on to the Virgo and GOLF Team meetings a couple of weeks before, proposals were flooding in.

Instrument intercomparisons are handled somewhat differently than other SOI/MDI proposals, since they must meet the requirements of each team and be approved by each of the involved PIs. However submission of proposals is the mechanism by which such investigations involving SOI/MDI data will be considered.

There are quite a number of proposals for good collaborative science as well as intercalibrations, but it is clear that some independent search for low frequency, low degree modes needs to be made by the SOI/MDI team.

**> If anyone is planning to work on this, proposals should be submitted soon.

We talked a little bit about forming a new SOI science team to consider just that topic [g modes and low-degree low-frequency p modes] but no conclusion was reached.

A list of the joint SOI/MDI & VIRGO proposals submitted through 13 October, 1995 follows. The Virgo Team designation/cross reference is provided where known.