SOI-MDI Newsletter
SOI-MDI Newsletter
These pictures are maps of motions in the solar photosphere - the visible surface of the Sun. Motions towards the observer are dark and the motions away are light colored.
The first frame is the first centered Dopplergram obtained with MDI. It was observed on December 21, shortly after the MDI protective door was opened. The large left-right variation is the signal from Solar rotation. The Sun rotates with a period near 27 days (the equator goes faster, the poles slower) which means the surface is moving at about 2km/s, or about 4500miles/hour. The "texture" is a combination of the motion from the sound waves that permeate the Sun and the large (Earth-size) convective cells called "super-granulation." The primary science of SOI will be accomplished by analysis of many months of such velocity maps, one observed each minute.
The second frame is the result of averaging 30 such velocity maps and subtracting the contribution from the Sun's rotation. The signature of the waves is nearly cancelled in this image since the wave periods are mostly about 5 minutes. The resulting image clearly shows the supergranulation pattern. The "smooth" area in the center is where the supergranules do not contribute to the signal since they consist of horizontal motion and MDI measures only the component of motion directed towards or away from SOHO. Close inspection shows that the supergranules show flow outwards from their centers so the edge toward the center are dark (motion toward SOHO) and the edge toward the Sun's limb are bright (motion away from SOHO). SOHO will allow a detailed study of such large scale convective motions.
The second image is an average of 3 High Resolution (0.6 arc-sec pixel) magnetograms. They were observed on 26 January 1996 at 20:18 UT.
As you are all well aware, SOHO was launched on 2 December. The MDI front cover was opened on 19 December and closed briefly for 2 spacecraft thruster firings for a mid-course correction and for the halo orbit insertion. The Halo orbit burn was accomplished on 14 Feb. We do not plan to close the door again. The initial test and calibration intervals have been labelled Block-2 and Block-3, (Block-1 was mostly before door opening). The Block-3 observations/calibrations are essentially complete and MDI seems to be functioning extremely well. At this point we are completing observations needed to fully calibrate the instrument and are preparing to do the observing sequences that would otherwise interrupt the Structure Program.
This is a good opportunity to bring to your attention the very fine efforts of the SOI-MDI EOF Team, Julia Saba, Craig DeForest, and Joe Covington, and the LPARL initial-ops and testing team led by Ted Tarbell and Igor Zayer. Significant essential efforts were contributed by LPARL participants Roger Chevalier, Craig Feinstein, Zoe Frank, Mike Levay, Dnyanesh Mathur, Mons Morrison, Roger Rehse, Larry Springer, and Jake Wolfson, and by Stanford participants Rock Bush, Todd Hoeksema, and Scott Williams.
We keep telling the EOF team that normal operations will not mean 7-day/week 12-hour days, but I am not sure they believe me... Their efforts have been examplary. They and we are all looking forward to the more relaxed normal operations to begin in a month.
The SOI-MDI experiment on SOHO is now operating and obtaining preliminary quick-look data that is already showing some intriguing possibilities for analysis. In the interest of allowing the further development of the various science investigations as quickly as possible we are making these data available for inspection and testing of algorithms.
There are several forms of data processing for MDI data. The High-Rate (160kbps) data comes to Earth via either SOHO Virtual Channel 2 or 3 (VC2 and VC3). The VC2 data are sent to the SOHO Experiment Operations Facility (EOF) at Goddard as soon as they are received by the Deep Space Network (DSN). The VC3 data (along with the VC2 data) are captured by DSN and sent on tapes by mail to Goddard where they are processed and sent by mail to Stanford. The VC2 data require substantial DSN-Goddard bandwidth so they cannot be available at all times.
The VC2 data are intended for monitoring MDI performance and for extracting near-realtime magnetograms for SOHO science planning. The bulk of the MDI high rate data will come only in the VC3 channel.
The SOI EOF workstation captures most of the VC2 data onto its local disks. These data are copied by "ftp" daily at the end of the UT day. They are referred to as Quick-Look data and are archived under the "mdi_eof" data program in the Data Storage and Distribution System (DSDS) database. In addition to instrument monitoring, the VC2 data are the source of many of the early calibration observations. To date, we have obtained far more data in VC2 than we had originally anticipated, and we have been able to proceed with calibration analysis even though we have not been promptly receiving the definitive data on tape due to government shutdown, weather delays, and processing delays. The VC2 data stream is subject to more dropouts than we expect in the definitive data and its continuity cannot be guaranteed. Nevertheless, the vast majority of the instrument data collected so far are being successfully captured this way.
Some of the VC2 data (and, we expect, early VC3 data once the processing gets up to date) contain observations that can be of immediate science analysis development use. Therefore, we want to make these data available to the team as quickly as possible. Remember that SOHO will not begin normal operations until early April. We do not expect level-1 calibrated data to be available until sometime in late March.
These data must be considered as uncalibrated, raw, unpublishable data made available solely for the purpose of developing science analysis programs and techniques that can later be applied to level-1 (calibrated) data. As such, the SOI data policy applies and science analyses developed with these data should be considered to be part of one of the SOI Science Working Groups. (This means that if you discover something really great with these data, you will have to agree to the rules of the appropriate working group for eventual publication of results re-obtained with level-1 released data).
Some of the data, e.g. 7.4 hour, 22 hour, and 38 hour sequences of full-disk Dopplergrams, have had some very preliminary processing done and some of us have found them quite interesting to look at. Much of the early data has been placed in the DSDS under the SOI program: Rsoi_eof", level:"lev0.5". More will be available there soon. Some movies of the data are also available via the Web by following the "http://soi.stanford.edu/test" path. If you are interested, please try the SOI Data Export method first (see below), then the "test" directory, then the phone.
Level 0.5 is a special level of processing not normally part of the reduction and analysis pipeline. It applies to Level 0 (uncalibrated) data that have been restored to image format and gathered together for the sake of level 2 analysis (remapping and transforms) by working groups in the same way that calibrated data would ordinarily be gathered into Level 1.5, but with many keywords remaining to be supplied or supplied in an ad-hoc way. That is why the data are (a) unpublishable and (b) subject to working-team analysis rules.
To use the SOI data export facility, go to the "Data Requests" link on the Web at http://soi.stanford.edu/sssc/datasets.html. It can also be found on the SOI home page under the "The SOI Science Support Center" heading listed as "Data Requests". Follow the path to data source "soi_eof" and then Processing Level Quick-Look : level 0.5 : High-Rate. We are aware that the descriptions of the data in soi_eof:lev0.5 are terse and are working on providing better visibility into the data available as well as the accomplished and planned observing sequences.
Now that SOHO has been successfully launched, and data is actually being received, the proper disposition of these proposals is a high-priority item in the SOI Project Office. PIs can expect to be contacted soon.
For a complete list of proposals received, please refer to the SOI Web page, SOI Proposals Received.
Please remember that the invitation to propose observational and analysis projects is open ended. Proposals continue to be welcome at "soiproposal@solar.stanford.edu".
There will be a SOI Team Meeting on 24-26 April 1996. This date was picked to roughly meet the plan outlined at the last Team Meeting in September 1995. SOHO reached Halo Orbit on 14 February (6 weeks early) and will begin normal operations shortly after the beginning of April. We now know that the 2-month Dynamics observation will begin on about 22 May and continue until about 20 July.
There are several objectives to accomplish at regular SOI meetings. These include reporting on investigation progress, accepting new investigations, setting observing and analysis priorities, and some opportunity for working group working sessions.
We picked the April dates without much consultation with you, with the understanding that there may be schedule conflicts. We do need to proceed with definitive plans for the May Campaigns however. (The April Campaigns are included in the nominal "First SOHO Month" and were discussed last September, at least in broad terms. Details will be handled at the March SOI Monthly - see below).
The SOHO SWT has now agreed that the SOHO Science Planning Working Group (SPWG) will meet at GSFC on a regular basis, on the third Friday of each month. Thus upcoming SPWG meetings are 15 March, 19 April, 17 May, etc. The SWT meetings will be quarterly the day before a SPWG meeting (next on 16 May). We have decided that the SOI Monthly Planning Meeting (as described in the plan of Sept 1994) will be held at Stanford on the Tuesday following the SPWG. Thus the next will be on 19 March then 23 April, etc. The purpose of the SOI Monthly meeting will be to select campaigns for the coming calendar month and to select priorities for the month after that to enable the development and testing of observing sequences. The actual campaigns run will generally depend on solar conditions, other SOHO constraints, etc., and will be decided at SOI Weekly planning meetings (held by telecon each Thursday afternoon just after the SOHO Weekly held at the EOF). Participation in the SOI Monthly and Weekly planning meetings is open to all SOI team members. Your presence is recommended if you are involved in complex Campaign observations.
Our intention is to schedule a larger SOI Team Meeting to be contiguous with every third or fourth SOI Monthly meeting. The date we announced quietly on the Web some time ago, 24-26 April nicely fits this goal.
I propose 31 July-2 August and 20-22 November as dates for other SOI Team Meetings this year. The July meeting should allow reporting of results from the campaigns run prior to the Dynamics interval and initial results from the first two months of the Structure Program. Last September, the global helioseismology working groups, the Rotation and Structure teams decided that their first results would be reported at the IAU-181 in Nice on 30 September. This will be just six months into the Structure Program and 2 months after the first Dynamics. It is likely that only preliminary analyses of Dynamics and Structure observations will be available by the time of the Nice meeting. It will be too early to have evaluated the 6-months of Structure that we decided was necessary prior to replanning the use of the 5-k telemetry. A goal for the November meeting would be to jointly agree on the future priorities for the bandwidth presently allocated to medium-l observations. A second goal would be to evaluate analysis procedures used for the Dynamics and to agree on plans for the second Dynamics interval presently scheduled to begin in April 1997.
I certainly expect and hope that there will be a number of working group meetings between these dates. I also fully understand that schedule conflicts will not allow full participation at all meetings. E.g. the July proposed dates conflict with the Brisbane dates. These conflicts are unfortunate, but MDI observes every day and with present funding has only about 740 days left.
- Phil Scherrer
The Solar Physics special issue (December 1995, Volume 162/1-2) includes lengthy reports from all the SOHO experiements, including "The Solar Oscillations Investigation - Michelson Doppler Imager" by P.H. Scherrer, et al. A limited number of bound volumes (containing the entire special issue) is available @ $50 each, from Margie Stehle.
Includes information about ISO, SOHO, and Cluster.
Pacific Grove, CA, 2-6 April 1995: ESA SP-376.
Includes "SOHO: Making Sense of the Moody Sun"
SOI-TN-130 Kosovichev et al. Simulation of Vector-Weighted Binning for the Medium-l Program SOI-TN-131 Hoeksema & Scherrer Precision of LOI Structure Program Calculations SOI-TN-132 Hoeksema Precision of the MDI Continuum Intensity
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This page last revised on 12 March 1996
