turn,ithasbeen recently proposed thatthe accelerated pickup ionsin CIRs become the seed population for the further shock

acceleration at the heliospheric termination shock, thereby creating the anomalous cosmic ray (ACR) component.

The CIReventsin 1996 (sincethe launch ofSOHO) havebeen relatively weak events.

However,CELIAS/STOFhasmade

measurement of the He ⁺content of CIR energetic ions for some selected intervals.The comparison of the CIR observations by

SOHO, WIND and Ulysses (spacecraft at different locations) will provide spatial gradient information that will tightly constrain

theoriesof shock acceleration and injection mechanisms.The resultsshould help establish the origin of the ions aspredomi-

nantly solarwind ionsorinterstellarpickup ions,the differenceinthe efficiency ofshockacceleration attheforwardand

reverse shocks, and whether the spatial gradients and energy spectra are related asrequired by current theory.

Planetary Science:Venus Tail RaysIn 1996 June, Venus passed through a very close inferior conjunction with the Sun. At that

time CELIAS/CTOFwasmeasuring heavy ionsin the solar wind~4.5x10⁷kmdownstreamof Venus.During the passage of

SOHO throughthe Venus wake, three encounters were made with unusual fluxes of O ⁺and C ⁺ions.Their energy distributions

resembled those of the tail rays known to originate in the Venus nightside ionosphere.The C ⁺abundance was ~10%of O ⁺.The

observed O⁺speed wasvery close to the simultaneoussolar wind speed and the O⁺temperaturewasa cool5600 K/amu.The

flux densitiesfor the three eventswere (2.1-4.4)x10³cm ^{- 2} s ^{- 1}.

6. The Sun-Earth Connection

Asan example of how theISTPsystemisworking, we summarizea very recentSun-Earth Connection event:

coronal mass ejection of April7, 1997.

the flare and

An ISTP case study:The 1997 April 7-11 eventOn 1997 April 1, and again on 1997 April 7, SOHO-EIT was able to observe

supersonic blast waves propagating outward from the site of a modest flare, across nearly the entire surface of the Sun in 1.5 MK

coronalplasma.SOHO-MDIhasbeen able to observe changesin the longitudinalfield atthe footpoints of these events.The

soft x-ray signature of the flare was observed by SOHO-SEM and by GOES-8,9.The WIND-WAVESinstrument detected Type

III emissions at13:59 UT on April7, consistent with the SOHO observationsof the flare.The April7 eventapparently led to

two CME's:one directed away fromthe Sun-earth line,and a halo event.Since launch,SOHO-LASCO has observed several

halo CMEs. TheseareCMEsthatappear asa halo around the entireocculting disk, indicating thatthe eventisdirected either

toward or away from Earth.As the April 7 event left the LASCO field of view, WAVESbegan tracking the progress of the event

using TypeII radio emissions.This type II emission, associated with the CME shock, was tracked from a fraction of a solar radii

to ~10-12 solar radiiand representsthe firstoccassion thatWAVES and LASCO/EIT havebeen ableto makesimultaneous

observations.

The flare produced a solar energetic particle event (SEP) that was observedin situby SOHO/ERNE beginning on April 7.The

interplanetary shock observed bySOHO-CELIAS/PMat~13 UTon April10 isassociatedwith asmallpeakin the ERNE

particle intensity (1.6-3.2 MeV), and a large increase in the SOHO-CELIAS/STOF suprathermal helium flux (85-540 keV).The

STOF composition indicates that interstellar pick up ions (He ⁺) are one of the important seed populations for the particles being

locally accelerated at the shock, in fact a remarkable He ⁺/He⁺²ratio of ~1 is observed!

On April11, the most intense auroralevent(K of 8) since the launch of SOHO or POLARoccurred.Throughoutits four-day

evolution,the ISTP observatory effectively remained in observationalcontactwith theeruption,collaborating with ground-

basedandgeosynchronoussatellitesto capturethe origin,propagation,geospaceimpact,and dissipation oftheevent.We

believe thatwe havenow, for the firsttime andby combining observationsin nearrealtime from SOHO,WIND,and POLAR,

observed a solar-terrestrialstormfromitsinception in the lower coronato its impacton the magnetosphere.While the initial

newsmedia coverage ofthiseventwasoutof proportion to the probableseriousnessofitsterrestrialeffects,the enormous

response from both media and private citizens to the media coverage indicate that there is widespread interest in solar-terrestrial

physics.

Coordination and dissemination of data sets for Sun Earth Connection Events are being done through ISTP workshops and the
World Wide Web (which allowsgreateraccessto awideruser group).The eventof 1997 April7-11 isdescribed at:
http://www-spof.gsfc.nasa.gov/istp/event_apr97/andhttp://sohowww.nascom.nasa.gov/gallery/current/.

Proposal forSOHO SolarMaximum Science Program-

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