temperature atthatheightin coronalholesisexpected to be lessthan 10⁶K.Similarly, in equatorialstreamers,v_1/e
along the LOSfor protonsand O⁵⁺become equalat4.7 R_Sun atvaluescorresponding to 1.3 x 10⁶K (protons) and
2.1 x 10⁷ K (O5^{+).In other}

words,notonly are the kinetic temperatureslarger for the higher massparticles,which iscontrary to most earlier theoretical

models, but also the velocities are extremely large.

The higher O5⁺velocities compared to protons in polar coronalholes can notbe explained by transverse wave motions caused

by MHD wave propagation through the corona.They are,however,consistent with theoreticalmodelsin which charged par-

ticles are accelerated about the coronal magnetic field through ion cyclotron resonant acceleration by relatively high frequency

MHD waves,which areassumed to exist.Further evidence for theion cyclotron resonanceprocessin the coronahasbeen

obtained by deriving the O ⁵⁺velocity distribution along the radial direction from the intensity ratio of the O VI 1032 and 1037

Å lines, which areformed by a combination of collisional excitation and resonantscattering.The radialvelocities,which are

expected to be parallel to the magnetic field lines in polar coronal holes, are at least a factor of 6 smaller than LOS values, which

areexpected tobe approximatelyperpendicularto themagnetic field in polar coronalholes.Theioncyclotron resonance

process appears to operate in both coronal holes and equatorial streamers.Thermalizing collisions may mask the evidence for

the process in the highest density regions.Work is continuing to determine to what degree coronal heating can be explained by

the ion cyclotron resonanceprocess,and to search for independentevidence forthe existence of the required high frequency

MHD waves.

Large-Scale Coronal Structure and Events

The vastly improved dynamic range of LASCO compared to previous coronagraphsand its 30 R _Sunfield of view are revolution-

izing our concept of the solar corona.Presented in movie form the LASCO data have, for the first time, revealed the small scale

jets,eruptions,and reconfigurationsassociated with both the gradualanddisruptive evolution of coronalstructures.Atlow

altitudes,beneath thehelmetstreamerstructure,the corona consistsof large-scale magnetic loopsassociated with the small

active regionspresentatthisphase of the solar cycle.LASCO movieshave shown thatthese loopsare continually expanding

outward.Thiscontinualexpansionappearstoprovidesufficientmassandenergytocompletelyregeneratetheequatorial

current sheet in a short period of time and to ultimately disruptthe streamer as a coronalmass ejection.

Coronal MassEjections.LASCO observationsarerevolutionizing our view of coronalevolution.

Earlier observationssug-

gested that the corona evolved on time scales of days, with disruptions by large-scale CME's.LASCO observations show that

coronalmassejectionsoccur ata rate thatisapparently more frequentthan during previoussolar minima.The CME's can be

large and asbrightasthose seen in the past,butin addition there are many smaller,lessmassive events.These observations

show that coronal structuresevolve continally in a manner consistent with the frequent generation of CME's with a large range

of sizes. UVCS spectroscopic observations of CME's have shown bulk Doppler velocitiesof up to 200 km s ^{- 1}.

Many oftheCME'sobserved with LASCO indicate thatalargeportion ofthesolarcoronamustbeinvolved inthe CME

process.These 'global CME's' are accompanied by small but obvious ejecta on the opposite limb.How the corona organizes

itself to generate such a global phenomenon is a major new problem for SOHO to attack.

Sources of the Solar Wind

It is well known that the large scale magnetic structure of the Sun determines the overall structure of the corona.Compact active

regionsgive rise to compactloops, which are imbedded in largerhelmet-shaped regions,which are capped by long streamers.

The low-speed solar wind originatesfromthese streamerbeltsand perhapsfrombetween the streamers.Much largerdiffuse

unipolar regionscan generateopen field regionsin the corona--coronalholes.These open regionsgive rise to the high speed

solar wind.While the locationsof these wind componentsare understood in a globalsense, only now isSOHO revealing the

mechanisms that power the wind and the specific locations of the acceleration regions.

Slow Speed Wind.Time-lapsesequencesof coronalimagesobtained with LASCO have yielded importantclueson the origin

and acceleration of the slow speed wind.Because ofLASCO's sensitivity, dynamic range, and field of view, bits and fragments

of material can be observed that appear to be torn off the tops of coronal streamers and carried passively outward like "leaves in

the terrestrial wind." The speed of the typical fragment doubles from 150 kms ^{- 1}at5 R _Sunto 300 km s^{- 1}at25 R _Sun.By tracking

the outward movementand assuming thatthe fragmentsare tracersofaflow field,a constantacceleration ofabout4 ms^{- 2}

through the coronagraph's 2-30 R _Sunfield of view is inferred.For a thermally driven wind, this implies that the coronal tempera-

ture doesnotfalloff rapidly with radialdistanceasit would for an adiabatic expansion,but remainsconstantatabout1.1 MK

outto 10-15 R_Sunand that the sonic point is near 5 R_Sun .

Proposal forSOHO SolarMaximum Science Program-

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