Notes from MDI for use in preparing senior review of SOHO operations, data processing, data analysis, and science investigations for FY02-05

I. Contents

II. Previous Senior Review

The SOHO Prime Mission was from April 1996 through April 1998. The SOHO program was reviewed along with other operating missions in the NASA SEC Theme in June 1997. The result of that review was approval to continue SOHO operations and science analysis for what was called the SOHO Solar Maximum Science Program. Part of the reccommendation was for the instrument team co-investigators to be funded via an expanded Guest-Investigator program. While the SOHO instrument teams were funded at or near the necessary levels to accomplish the goals of the solar maximum program the Guest Investigator program was not adequately funded. As a result, a number of the analysis projects we counted on proceeded on shoestring budgets with fewer results than had been hoped. Nevertheless, we as a team, have made significant progress toward the goals outlined in 1997 and have made discoveries in areas not anticipated in the prior review. The near loss of SOHO in 1998 and resultant intermittent operations into Feb 1999 also caused a significant loss in momentum and a break in continuity that delayed some of the investigations requiring continuity such as the g-mode search and the cycle evolution of fields and flows.

The Previous Review Links contain the SOHO Solar Maximum Science Program proposal and the report and reccommendations of the Senior Review Panel. The proposal outlined major accomplishements for helioseismology as:

And it summarized the topics for SOHO Solar Maximum interval:

III. MDI Science Contributions

MDI successfully provided observations leading to discoveries and progress in understanding of a number of topics during the SOHO prime mission and extended phases. MDI data has contributed to at least 12 PhD dissertations, made significant contribution to at least 15 symposia and workshops with refereed proceedings, and provided data for at least 458 papers as of March 2001. Of the papers, there were 13, 43, 142, 98, 120, and 42 in 1996-2001 respectively.

Since the 1997 Senior Review MDI contributed to several new discoveries. There is not space here to review them all so only a few are listed here. The full list of papers is linked below.

Of the 20 items above, at least 13 were primarily accomplished or had significant contributions by Guest Investigators.

A number of MDI results have produced interesting visual results. Some of these are available in the MDI "Nice" Image Collection for use as needed by the MDI community.

IV. Proposed Investigations

There are many science investigation topics presently proceeding with the support of MDI observations. The range of topics presently under investigation is similar to the topics in the hundreds of papers published to date. Some sample studies that require continued MDI observations in the declining and near minimum phases of the present cycle are described here.

  • Geoeffectiveness of CMEs

    CMEs are only geoeffective when they contain or drive several hours of southward Bz when they arrive at Earth. Estimates of the orientation of fields pushed by CMEs show that the pre-existing field estimates for the overlying corona make good predictions of the Bz when the locations of Earth directed CMEs are known (e.g. Zhao & Hoeksema, 1997). Recent developments in processing of MDI magnetograms has led to the concept of "synoptic frame" where synoptic whole-Sun Carrington grids of magnetic field are suplemented by rapidly updated magnetic information for the visible disk. Initial analyses of these data are promising and may lead to better estimates of the sign and strength of the Bz component of the field carried by CMEs. Tools to use this data is presently being developed at UC Berkeley. See: sample use. The synoptic maps using the 96minute magnetograms are prepared daily for planning purposes. Some notes on the geo-effectiveness of CME's.

    Daily Synoptic Magnetic Map

  • Extended Cycle

    Evidence shows the visible part of the cycle is something like 18 years with a 6-8 year overlap between cycles. Altrock (Sol. Phys., 170, 411, 1997) reviews the literature and adds new evidence for the 19-20 year duration of each 11-year cycle. Each new cycle can be detected in magnetic polarity at high latitude just after max, both in ephemeral regions (e.g. Martin and Harvey) and in large scale measure of torriodal field (Schrauner & Scherrer). [gee it sure would be nice to update the WSO analysis. hmmm - ah, it would take a few days, but which few?] The extended cycle is also seen clearly in the large scale zonal rotation residuals also known as "torsional oscillations". We now see the zonal flows are in at least the top third of the convection zone (see e.g. Giles dissertation, and Howe et al. (ApJ, 533, L163-L166, 2000)) and can watch for the first time to see how they evolve and relate to the appearance of new cycle fields.

    Zonal Flows Deep in CZ

    This figure shows the residuals in rotation after removing a smooth equator-to-pole variation. The panels are centered at progressively deeper layers. From Howe et al.(ApJ 533, L163-L166, 2000).

    There are at least three aspects to the extended cycle that can be examined with continued MDI observations into the declining and minimum phases of the cycle.

  • Delayed Geomagnetic Cycle

    Many if not most 11-year cycles have a second peak or a delayed peak in geo-effective solar disturbances to the geomagnetic field. The 27-day recurring geomagnetic storms that are common in the declining toward minimum phase of the cycle are the result of low latitude extensions of the polar coronal holes apparently combined with the conditions to create southward Bz at the Earth. While perhaps not an MDI topic, the availability of EIT and LASCO data, combined with MDI magnetograms, can allow study of the solar side of this interesting phase of the cycle.

    Ap vs Sunspots

    This figure shows the number of days per year where the geomagnetic activity index "Ap" exceeded a value of 50. The Ap data is plotted over the sunspot number index. It can be seen that geoeffective solar events are more prevalent in the declining years of the sunspot cycle. Figure is from Joe Hirman at NOAA via Xue Pu Zhao

    V. MDI Instrument Status

    After 5 years of operation, MDI is basically working very well. MDI has made about 50 million images. After on-board computations, it has delivered about 8 million raw data images to the ground.

    In summary, with the possible exception of the recently detected shutter jitter, there is no known limit to MDI's useful life within the SOHO expected fuel life.

    VI. MDI Data Processing

    At the end of March 2001, the MDI data processing system, SSSC (SOI Science Support Center), had archived 1.015 million datasets containing 53.6 Terabytes of raw and processed data. The MDI data center has responded to more than 6000 individual requests for data amounting to about 8 Terabytes. Most requests are for multiple datasets. Requests for MDI data processed through the SOHO archives at GSFC and the remote SOHO archives in Europe are not shown here.

    MDI Data Requests

    Left: Requests for MDI Data exports processed since Sept 1997.

    Right: Cummulative volume of data exported from the MDI archive via the Web interface at

    VII. MDI Publication Record

    For Dissertations see: Dissertation List

    For list of Proceedings see: Conference Proceedings List

    For list of Papers see: Paper List

    VIII. MDI EPO Activities

    Education and Public Outreach are important adjunct activities of the MDI team. These activities include: