I) Executive Summary

The current Sun-Earth Connections complement of spacecraftprovides humanity with an unprecedented opportunity to under-

stand the Solar System in which we live. This understanding is essential if we are to understand the boundary conditions for the

developmentoflife and if we are to continue our expansion from the earth. While this proposal emphasizesthe importance of

the SOHO componentof thissystem,we mustuse the opportunity to obtain adequateresourcesfor the spacephysicscommu-

nity to continue our search forunderstanding of the Solar System.The elimination of or a major cutin any of the Sun-Earth

Connectionsmissionswillrepresentthe abandonmentof a unique opportunity to make major stridesin improving thatunder-

standing -- an opportunity unlikely to present itself again in the foreseeable future.

The scientific return fromSOHO

hasbeen spectacular even though we are justone year into the nominalmission. SOHO's

powerto shednewlighton solar-terrestrialdisturbanceswhen itsmeasurementsare combined with those from otherspace

physicsspacecrafthasbeenrealizedonly during thelastfew months.SeveraldiscoveriesfromSOHO arediscussed in the

Overview (Section II) and Summary (Section VII), below.

In order both to extend our understanding of the effects of the rise phase of the solar cycle on the solar interior, surface magnetic

fields,corona,and solarwind and to seizethe opportunity for jointsolar-terrestrialresearch provided by thecombination of

SOHO, GGS, Ulysses, andYohkoh, we propose a four-year re-use of the existing SOHO resources: the SOHO Solar Maximum

Scienceprogram.(The Scientific Programme Committee of ESA hasunanimously approved an extension of the SOHO mis-

sion, an ESA "Horizon 2000" cornerstone mission, into CY 2003.)

The SOHO Solar Maximum Science program would combine cost-effective operation of all the SOHO instruments at their full

scientificpotentialwhilesignificantlyincreasingtheavailability ofSOHOdataandthepoolofresourcestoallow theUS

research community to analyzethose data.Infact,the MDI and EIT PI'shaveannounced their intention toplacealltheir

instruments' data in the public domain assoon aspossible in a SOHO Solar MaximumScience program:therewould be no

proprietary data analysis period. The other SOHO PI's have similarly announced the public availability of a "solar variability"

data setthatwill also be placed in the public domain with a minimumof delay.

While aGuestInvestigator programisnotpartofthe baseline budgetproposal,a SOHOSolar MaximumScienceprogram

would only be able to achieve its potential for advancing our knowledge of the Sun-earth system if accompanied by a strong GI

program. Likewise,the benefitsof interdisciplinary sciencecan only be realized if an integrated GIprogramcoversthe entire

range of an extended ISTP program.

Finally, while SOHO has directed significant resources to public education and outreach activities with notable success, there is

much morewecould bedoing in thisarea,which iscrucialboth to our nation'scontinued leadership in technology and to

accountability to the taxpayers who make our scientific endeavor possible. We therefore propose a modest increase in education

and outreach funding to enlarge the scope and impactof these activities.

The following individuals were among those involved in the writing of this proposalon behalf of the SOHO Science Working

Team: A. Poland (GSFC), J. Gurman (GSFC), A. Title (LMMSC), J. Mariska (NRL), G. Brueckner (NRL), P. Scherrer (Stanford

U.), J. Kohl (SAO), J. Raymond (SAO), A. Galvin (U. Maryland), F. Ipavich (U. Maryland), and P. Martens (ESA)

Coverfigures

Upperleft:

Radial and latitudinal variations of sound speed, as determined from inverting SOHO-MDI observations, relative

to valuesfrom a "standard" solar model. Red corresponds to positive difference, blue/green to negative.

Upperright:Electron-scattering image of the corona to 30 R _Sun from the SOHO-LASCO C3 coronagraph, 1996 December 23.

The bright, extended objectjustabove the pylon to the southwest(lowerleft) ofthe occulting disk is sungrazing

comet SOHO-6. The background is the center of the Galaxy. The small, white circle in the center of the occulting

disk representsthe disk of the Sun.

Bottom:

Time seriesoffirstdifference imagesfrom SOHO-EITofa coronalMoreton wave expanding from the site ofa

small flare. The original images were obtained in the Fe XII emission line at 195 Å, formed at1.5 MK.