Simulation of the magnetic structure of the inner heliosphere by means of a non-spherical source surface

Abstract

LABORATORY OPERATIONSThe Laboratory OperatIons of The Aerospace CorporatIon lS conductmg expenmental and theoretIcal mvestIgahons necessary for the evaluatIon and apphcatIon of sClentIftc advances to new mlhtary concepts and systems Versahhty and flexlblhty have been developed to a hlgh degree by the laboratory personnelln deahng With the many problems encountered ln the nahon's rapldly developlng space and mlsslle systems Experhse m the latest sClenhflC developments lS vltal to the accomphshment of tasks related to these problems The laboratorles that contrlbute to th,s research are AerophyslCS Laboratory Launch and reentry aerodynamlcs, heat transfer, reentry physlcs, chemlcal kmehcs, structural mechamcs, fhght dynarrllcB, atrrlOsphenc pollutlOn, and hlgh-power gas lasers.Chemlstry and PhYS1CS Laboratory Atmosphenc reactions and atmospherIc optics, chemical reactions In polluted atmospheres, chenucal reactIons of excIted speCIes In rocket plumes, chemIcal thermodynamIcs, plasma and laser-mduced reactions, laser chemlstry, propulslOn chemlstry, space vacuum and radlahon effects on materials, lubricabon and surface phenomena, photosensltIve materlals and sensors, hlgh preC1Slon laser rangmg, and the apphcahon of phYS1CS and chemlstry to problems of law enforcement and b,omed,c,ne ElectroniCS Research Laboratory Electromagnetic theory, devlces, andpropagatIon phenomena, mcludmg plasma electromagnetIcs, quantum electronlcs, lasers, and electro-optics, conununlcahon SCIences, apphed electronics, semIconductIng, superconductIng, and crystal devlce physlcs, optIcal and acoustical lmagmg, atmospherlc pollutIon, mllhmeter wave and far-mfrared technology Matenals SClences Laboratory Development of new materlals, metal matrIX composItes and new forms of carbon, test and evaluation of graphIte and ceramlCS ln reentry, spacecraft matenals and electromc components ln nuclear weapons enVlronment, apphcatton of fracture mechaniCS to stress carrOSlOn and fatIgue-lnduced fractures ln structural metals Space SClences Laboratory Atmosphenc and lonosphenc phYS1CS, rad,atIon from the atmosphere, denslty and compoBlhon of the atmosphere, aurorae and alrglow, magnetospherIC phYSICS, cosmIc rays, generatIon and propagatIon of plasma waves m the magnetosphere, solar phYSiCS, studies of solar magnetic f,elds, space astronomy, x-ray astronomy, the effects of nuclear exploslOns, magnetlc storms, and solar actIvlty on the earth's atmosphere, lOnosphere, and magnetosphere, the effects of optIcal, electromagnetIc, and partIculate radlatIons ln space on space systems ACKNOWLEDGMENTSWe would like to thank Dr. R. Munro for assistance in the interpretation of I~O Skylab coronagraph data.

Non-spherical source-surface model of the heliosphere: a scalar formulation

“…For now this is just a working hypothesis to be tested against future Ulysses data. However, Levine et al (1982) found that a similarly (although parametrically more cumbersome) intermediate shape between k 0 and k 1 could account quite well not only for the MHD field configuration obtained by Pneuman and Kopp (1971a,b) in the dipolar test case, but also for a more complicated coronal and interplanetary B-field configuration encountered not far from solar maximum.…”

“…The goal in choosing a nonspherical source surface is to arrange for the region(s) of minimal source-surface curvature to straddle the inner edge(s) of any heliospheric current sheet(s). The choice of a surface of constantF as source surface shows some promise in this regard (Schulz et al, 1978;Levine et al, 1982; and in the present work) but is not guaranteed to achieve the desired configuration. However, the purpose is likely to be defeated altogether (especially near solar maximum, whenB is quite complicated and multiple heliospheric current sheets are possible) if some fixed shape is assigned to the source surface, regardless of the form ofB.…”

“…(1) is made (as nearly as possible) perpendicular to a prolate source surface in the model of Schulz et al (1978) and Levine et al (1982) by minimizing the variational quantity (1b). This procedure seems simple enough in concept, but its implementation in general has led to page-long equations and correspondingly long computation times (Levine et al, 1982).…”

“…Ulysses observations by Smith and Balogh (1995) have confirmed this (the latitude-independence of r 2 B r ) as a desirable result. Levine et al (1982) applied the concept of Schulz et al (1978) ) between the photosphere and the non-spherical source surface was again separated into contributions due to currents at r in the work of Levine et al (1982) ) a bilinear variational quantity equal to the mean-square tangential component of B over the source surface. (The goal of this procedure was to make B as nearly as possible normal to the source surface from the inside.)…”

On the uniqueness of the determination of the coronal potential magnetic field from line-of-sight boundary conditions

“…F 1 is generally taken to be a sphere of radius r~ (r~ being a free parameter, sometimes taken infinite to further simplify the model) (Semel, 1967;Newkirk et al, 1968;Schatten et aL, 1969;Altschuler and Newkirk, 1969;Adams and Pneuman, 1976;Riesebieter and Neubauer, 1979;Sakurai, 1982;Bogdan, 1986). However, new models have been recently proposed in which F1 has a more complicated shape, determined by using an extra physical criterion (Schulz etaL, 1978;Levine et aL, 1982). In all those simple 'potential models', what is just required in principle for computing B is, F1 being fixed, the value at all the points of Fo of the component B l of B/Fo along some direction l'(r).…”