propagate through the outer solar atmosphere and into interplanetary space.Hence the charge state composition ofin situsolar

wind is used to infer coronalelectron temperatures.

Fine time resolution charge statespectrafor solarwind iron ionshave been obtained with CELIASCTOFwhile itwasfully

operational.The rapid and consistentchangesin freezing-in temperature calculated fromthreedifferentpairsofiron charge

statesindicatesa patchy structureof the corona with length scalesof some 10⁴kmand revealsthe survivalof these structures

from a few solar radii to 1AU. These structures had not been seen previously, because the necessary temporal resolution was not

available before CTOF.

4. IN SITUSOLAR ENERGETIC PARTICLES

The COSTEP and ERNE experimentson board SOHO are designed to detectenergetic particlesfromseveralspeciesovera

range of energies.Electrons are recorded at energies from 44 keV to 50 MeV.Protons are recorded at energies from 44 keV to

over 100 MeV.Alphas are recorded from a fewMeV/nucleon to over 100 MeV/nucleon.Heavier elements, up to iron, can be

identifiedupto500MeV/nucleon.SuprathermalionchargestatecompositionsonSOHOaremeasuredbytheCELIAS

SuprathermalTime-of-Flight(CELIAS/STOF) sensor which measuresthe energy distribution of individualchargestatesof

variouselementsin the energy range 20 keV/e to 3 MeV/e.

The bestperformance parameter ofthe ERNE instrumentisthe achieved massresolution.

In ERNE/HED allelementsfrom

hydrogen to nickel have been observed.In ERNE/LED, due to much lower collecting power, the statistics of the rare elements

are still very low, but iron, e.g., can be clearly resolved.The full resolving power of various isotopes in both sensorsis still to

be demonstrated, but isotopes up to calcium have been observed in ERNE/HED.The "difficulty" has been the very low activity

of the sun in producing energetic particlesduring thissolar minimum, also emphasizing the galactic background.

During the firstyear ofSOHO operation,the Sun wasclose to minimumlevelsof activity.Asa result,the number ofsolar

particle eventswassmall.Nevertheless, there are already indicationsof differentacceleration mechanismsin differentflares.

Moreover, there are indications of chemical fractionation in the solar atmosphere, and, most important, an estimate of the time-

scale on which this fractionation operates.

Asregardsacceleration mechanismsin flares,itisalso clear thattheelectron/proton ratio variesfromoneflareto the next.

Quantitative modelling of the e/p ratios may help to identify which acceleration mechanismisdominant in each flare.More-

over,the ramp in the electron countsduring 1996 July 8 and July 9, prior to the sharp increase in electrons,hasno apparent

counterpartin the p or alphachannel.Thisramp suggeststhata super-thermalelectron population buildsup in the pre-flare

processfor a period of daysbeforethe flareoccurs.Key information aboutthe physicsof pre-flare heating will be obtained

froma study of these rampsin active regionsof varioustopology:thiswill become possible assolar activity increases.

5. IN SITUHELIOSPHERIC SCIENCE

Pickup IonsThe flux of pickup ions in the solar wind depends on the local atom densityand the ionization rate of the inflowing

neutral gas.The local atom density (except for the case of hydrogen) is affected by the gravitational force ofthe sun, which acts

asalensforfocusing theintensity ofthe gasin thedownwind side (relative to movementby theheliospherethroughthe

VLISM).The earth's orbit (and hence SOHO) passes through this higher density section once per year.The ionization rates are

affected by solar EUV fluxesand solarwind ion densities.These parametersarevariable on both a shorttermscale,due to

isolated solar activity, and on the longer time scale of the solar cycle.While CELIAS/CTOF measuresthe actualpickup ions,

importantinput parametersforthe pickup ion production rate are being simultaneously measured:CELIAS/PMprovidesthe

local solar wind density, the CELIAS/SEM provides thesolar EUV measurements, and the SOHO orbit provides the "seasonal

variation"-samplingthroughdifferentneutralgasdensitiesasafunctionofthegravitationalfocusingcone.Theseinput

parametersare important not onlyfor pickup ion studies performed by CELIAS/CTOF, but also for those studies being carried

outby time-of-flightspectrometerson the Ulysses, Wind, and(in the near future) ACE missions.

Shock AccelerationatCIRsThepickup ionsprovideasuprathermalion population in the heliosphere,whichmakesthem

candidate seed populations for shock-acceleration.It is now believed that He ⁺is a significant component of energetic ion events

associated with the forward and reverseinterplanetaryshocksthatbound corotating interaction regions(CIRs) in thesolar

wind.(These are structures in the heliosphere that develop due to the interaction of fast and slow solar wind.)The likely source

of accelerated He ⁺is from the pickup ion population, sincethe solar wind normally contains only negligible amounts of He ⁺ .In