Jan 15, 1996 - simultaneous AE variations shown in the top panel of Plate 1 are ... lâ¢c silages noted ⢠Plate 1 â¢c clcâ¢l⢠appâ¢cnt â¢om ... all foâ¢d â¢1ow 1 â¢E altiâ¢dc.
GEOPHYSICALRESEARCHLETTERS,VOL. 23, NO. 2, PAGES129-132,JANUARY 15, 1996
Signaturesof impulsiveconvectionin the magnetosphericlobes D. C. Delcourt •, J.-A.Sauvaud 2, O. L. Vaisberg 3, L. A. Avanov 3, J. L. Burch 4, and J. H. Waite Jr.4
Abstract.We analyze theinjections oftailwardflowing0 + ions RE)until-23:00UT (Z- 8 RE).Thespacecraft thenencounters measuredby PROGNOZ-8 in the magnetospheric lobesusing theplasmasheetandultimatelytheradiationbelts. It is of interestto notethat the LIS occurrence patternand the three-dimensional single-particlecodes.These injectionsare AE variationsshownin the top panelof Plate 1 are shapedas "invertedVs" and unexpectedly well correlatedwith simultaneous AE variationsduringa time intervalof about7 hours.Sucha quite similar in shape.As a matterof fact, a cross-correlation correlation leads us to consider the effect of transient analysis-betweenthe AE magnitudeand the energy of the intensificationof the large-scalemagnetospheric convection. maximum O+ fluxin thespectra revealsa correlation coefficient Usinga simplemodelof time-varying electricfield,we showthat of-0.7 between13:00UT and 19:00UT with a time lag of the the source of the O+ lies nearthe dayside cusp.This source order of l0 minutes(the AE changepreceedingthe energy extendsovera narrow(a few degrees)latitudinalintervalin the change).This correlationsuggests that the occurence of LIS is vicinityof thelastclosedfield line, likely involvingionsexpelled linkedto globalchanges in the magnetosphere. Variationsof the into the magnetosphere after beingtransversely accelerated. We ionospheric currentsystemand henceof the AE index occurin demonstratethat, downstreamof the ejection site, impulsive response to reconnection at the daysidemagnetopause as well as convectionleads to prominent structuringof the tailward in response to plasmadynamics duringssubstorms. As the largestreaming particleswith abruptenergyvariationson smalllength scalemagnetospheric convection significantly variesduringsuch scales.A good agreementis obtainedbetweenthe numerical events[e.g.,Richmond et al., 1990],the purposeof thispaperis results and the observationswhich supportsour impulsive to revisit the resultsof Vaisberget al. [1995] using threeconvection basedinterpretation framework. dimensionalcalculationsof single-particletrajectoriesin the presence of a time-varying convection electricfield. Introduction
On-August27 1981, the PROGNOZ-8 spacecrafttraveling inbound in the magnetosphericlobe (northern hemisphere) recordedseveralinjectionsof ionswith energiesin the 200-eV to 1-keV range and propagatingin the antisolardirection.In a previousstudy,Vaisberget al. [1995] identifiedthesetailward flowingparticlesas cold beamsof oxygenions. Theseauthors discriminated betweenion speciesby notingthat, duringthese events,selectiveanalyzersonboardPROGNOZ-8showcounting ratesat thebackground levelforbothprotonsandalphaparticles, whichleavesoxygenionsas the mostprobablespecies.Vaisberg
Originof TailwardFlowingO+ In view of the goodagreementbetweenAE variationsand the observed injectionpattern,we startwith the assumption that the cross-polar cappotentialdropcanbe directlyrelatedto the AE magnitude.Such an assumptionclearly is oversimplified.In particular,largechangesin theAE magnitudeprovideevidences of modifications in the magnetospheric currentsystem,and the above assumptiondoes not explicitelytake into accountthe induced
electric
field
which
should result
from
concurrent
dynamicalreconfiguration of the magnetosphere. Still, we will et al. [1995]suggested thattheseO+ originate fromthe cusp seefromthe simulationresultsthat, as a farstapproximation, the region. The bottompanel of Plate 1 showsthe energy-time above assumptionis not unreasonable in the magnetospheric spectrogram recordedduringthis pass.In this panel, it can be lobesandthatit leadsto injectionsignatures whichare consistent seen that PROGNOZ-8 enters into the magnetosphere at with those observed. approximately 06:30 UT as identifiedby the intenseflux of As shownin Figure 1, we focuson the 10:00UT to 19:00UT energetictailward flowing particles in the plasma mantle sequence of the S/C pass.In orderto evaluatethe cross-polar cap adjoiningthe magnetopause. Subsequently, as the spacecraft potentialdrop(•) at anytime throughout this sequence, we farst travelsthroughthe lobein the vicinityof the midnightmeridian performed a splineinterpolation throughtheAE profiledisplayed plane,repeatedinjections arenoticeable whicharewell separated in Plate 1. At a giventime, we thenmodeled• in a nearlylinear in time and nearlyshapedas "invertedVs". In the following, manner with the instantaneousAE magnitude, imposing thesestructures will be referredto as LobeIon Structures (LIS). threshold values of 40 kV for AE _• 200 nT and 200 kV for AE • In Plate l, it canbe seenthat LIS occurfrom -12:00 UT (Z - 18
1CETP, Saint-Maur des Foss6s, France 2 CESR, Toulouse, France 3 SRI,Moscow, Russia 4 SwRI, SanAntonio, Texas
1000 nT. The ß variationsthusderivedare presentedin Figure la. Thesevariationsare in qualitativeagreement with previous detailedanalysisof the relationship betweenthe magnetospheric electricfield andthe currentin the ionosphere [e.g.,Kamideand Baumjohann,1985; Richmondet al., 1990]. Moreover, the resultingthree-houraveragedpotentialdrops(heavydashedline in Figurela) arecomparable to thosederivedusingtheMaynard and Chen [1975] equationand appropriatevaluesof the Kp
Copyright1996by theAmericanGeophysical Union.
parameter, viz.,Kp = 3+ from9:00UT to 12:00UT, Kp = 5+ from12:00UT to 18:00UT, andKp= 4+ from18:00UT to 21:00
Papernumber95GL03267
UT [Coffey,1981]. In orderto performtrajectorycalculations, we sortedout the
0094-8534/96/95GL-03267503.00
energy ofthemaximum O+ fluxduringeach4-minute scanofthe 129
11oo•
I
300•
' : : : : a•]
PROGNOZ-8
L o
lOOO
•
500
' ' •,{
AUGUST271981
1 oo
0.1
,
230 •' [ UT X Y
06
08
Z
}• 10 -18.01 -0.88
12
18.96
14 16 -17.23 -3 75 15.81
18
20 22 -15 41 -7.47 9.81
00
02 -12.77 -6.23
04
1601
06
i
'
16
17
5.87
Plate 1. (Top)• •dcx versust•c. (BoSom) color-coded cncrg7-t•c spcc•o• onAu•st 27 1981.
P•OGNOZ-8 spcc•omctcr.•c energyprofile •us ob•incd is sho• in Fig•c lc (hca• solidl•cs). •c repeated•vcdcd-V l•c silages noted• Plate 1 •c clc•l• app•cnt •om fi•c, •d •c• modulationaccord•g to •c • ma•dc is readilynoticeable by comp•son• Fi•c 1•. To idcnti•
ofig• of •c •ilw•d fio•g
O+, wc computed •ajcctofics
10
11
12
13
14 TIME
15 UT
18
19
backed • t•c •om •c S/C l•ation. •csc compu•tions Figure 1. (a) Modelcross-polar cappotentialdrop,(b)AE index, wcrcc•cd outusing•c T•g•,•,ko [1987]m•cl (hcrc•affcr (c) energyof the maximum O+ flux, (d) ion pitchangleat rcfc•cd to asT-87) • a non-tiltedcollation co•cspond•gto PROGNOZ-8,(e) initial MLT, (/) initial ILAT, and(g) particle ß c average Kp levelincaskedon•at • (Kp= 4,4+).• F•st timeof flightversustime.The dashedline in (a) showsthethreeapprobation, •s level was kept cons•t • •c calculations. houraveragedpotentialdrop. At each •ajccto• step, •c l•a] •s••cous clcc•c field (essentiallydusted) was calculated ionosphere, bothin MLT (between-10.00 and-11.00 hours)and ionosphere,ass•g •at •c marctic field l•cs in ILAT (between-70ø and-80ø). It shouldbe stressedthat cquipmcntials. • •c ionosphere,a Foll•,• [1978] potential thesenumericalresultsare fairly sensitiveto the particlepitch dis•bution was used • a t•c-v•g cross-pol• cap angleat the S/C locationaswell asto the modeladoptedfor the pot•tial •op as descried a•vc. time-varying convection electric field. Trial and error • •c o•cr h•d, eachs•plc of •c energyprofile• Fi•c computations showedthat onlyparticlesnearlyalignedwith the
1c wasassi•cda testO+ •
co•cspond•g energy. As for
pitch •glc, it should• mentioned•at spcc•omctcrpo•ts mw•d S•. • •c ma•ctosphcficlo•, it •us recordsp•iclcs w•ch propagate • a d•cctionfa•17 close to •at of •c ma•cfic field (scc F•i•• •t •L [1995] for a defiled discussion of •c •s•cnt). • •s basis,wc ass•cd ß c p•iclcs to be ne•17 alined • •c marctic field (i.e., ne•17 zero marctic mom•t) • •c •id•g centerreference •c. Under such conditions,pitch •glcs rcfcr•cc •c •c css•tial17 ducm •c l•al •s••cous B •ff vcl•i•. •csc pitch •glcs wcrc fo•d •ccn 5o 15ø at •c S/C l•ation (Fig•c 1•, w•ch is consistent • F•st approbation • •c •s•cnt field of view. As for l•ation, it must be s•csscd •t
ma•ctopausc at-6:30 •
•c
S/C cnco•tcr
magneticfield anddriftingin an electricfield nearlyproportional to theAE magnitude originatefromthetopsideionosphere during the time intervalunderconsideration. Notwithstanding the fact that they are out of the angularrange of the PROGNOZ-8
instrument, test O+ with largepitch angleswere foundto originate from unrealistic sourcesin the magnetotaillobe, whereasdifferentmodelings of the convection electricfield led to unphysical cross-polar cappotentialdrops.
Furthermore, thevertical barsin Figurel c jointheO+ energy at the S/C locationandthe computed oneat mirrorpoint.These barsrevealenergiesat ionospheric heightsbetween-100 eV and severalhundredsof eV. On the whole, theseresultscorroborate
the suggestion madeby Vaisberget al. [1995]that the O+
(Z- 20 •E) •c•s somewhat lower
• Z hci•t • •c ma•ctopauscpositionfca•cd • T-87 (scc opensq•c • Fig•c 2•). •s differencewas fo•d to • of critical •po•cc when •ac•g •c oHg• of •c •ilw•d
PROGNOZ-8
20
•
-I -
fio•g O+ as it led to •calistic mapp•g•to •c ionosphere (e.g.,possibly 7icld•g a so•cc of energetic O+ • •c •-
..=..•.-•
ß
lati•dc pol• cap).• •c n•cfical calculations, wc adjusted modelma•ctopausc•d •c obsc•cd oneb• •crcas•g •c S/C
N
10
position bya•ut 1.5•E • Z, •t is• practice,
/
•
"
/
//
,•.(/../
18UT 15 UT
S/C orbitby about3.8 ho•s. •c
resets
of •c
calculations •c
sho•
•
Plate 2 w•ch
presents •c computed O+ •ajcctofics •til •c F•st•or cnco•tcrcd d•g
backed •ac•g. •csc •or
po•t
po•ts wcrc
•'•' •
0 ......... -10
-5
•' 0
12 UT
.................. 5
09UT 10
15
20
x (R,) all fo•d •1ow 1 •E alti•dc.•c •cc lowerp•cls ofFig•c 1 present •c O+ marctic l•al t•c (•T), •v•t lati•dc Plate 2. ModelO+ trajectories in the noon-midnight meridian
(•AT) •d t•c of fii•t at •or po•t. It c• • sccn• •csc p•cls •t mostof •c ionsoHg•atc •om a n•ow region
plane.The trajectories are color-coded according to the arrival time at PROGNOZ-8(heavysolidline).
lower ILAT (solid line). This phasingeffectcombinedwith the abovecurvature-related acceleration canprovidea mechanism for thewell-separated invertedV-like structures in Figure1c. This is illustrated in Figure 3 which shows the energy variationsobtainednumericallyalong the S/C pass assuming eithera constant (100-kV) cross-polar cappotentialdrop(Figure 3a) or a time-varying one(Figure3b). For simplicity,a 300-eV initial energywas considered in both cases.In the steadystate patternis obtainedexhibitinga andpitchangleof 90ø below1 RE altitude), ionconics locally case(Figure3a), a continuous energydecrease from-700 eV at 10:30UT downto produced via transverse heating[e.g., Waiteet al., 1986] are progressive
originatefrom the cusp region. In particular,the T-87 configuration usedin thesecalculations placesthelastfield line whichis closedin thedaysidesectornear75øILAT, andit canbe seenthattheionsdetected byPROGNOZ-8originatefromwithin a few degreeson either side of this last closedfield line. Significant waveactivityis knownto occurin thisregionof the high-latitudeionosphere [e.g., Lundin, 1988] and from the present results(i.e., characteristic energyof a fewhundreds of eV
likelyto be thesource of theobserved tailward flowingO+
-450
eV at 15:30 lyr.
These variations result from enhanced
field line curvaturein the outer cuspregion,and thus larger energizationfor particles launchedfrom lower ILATs. As ImpulsiveMagnetosphericConvection mentionedabove,this patternis incompatible with that observed An interesting featureof the LIS is the sharpinvertedV-like (light lines) even thoughthe averageenergyis fairly well structuring of the ion energy(see for instanceFigure lc). In reproduced. In contrast, in Figure3b,narrow O+ structures with energiesare noticeablefrom -13:00 particular,clear interruptionsare noticeablebetweentwo increasingand decreasing successive structures whichcannotbe interpretedsimplyfrom a lyr to -18:00 lyr, which resemble the observed LIS. In followstheAE variationquite geomagnetic massspectrometer effectin steady state.Indeed,gx particular,the energymodulation B driftin thepresence of a constant dawn-to-dusk potential drop well. This agreeanentis however only qualitativeas the smallerthanthat leadsto spatialdispersion of particles withdifferentenergies (or amplitudeof the energychangeis substantially masses) butin a continuous manner.Thiseffectis incompatibleobserved.This latter effectmay be due to the toorio-energetic with the dispersion patternobserved. To account for the abrupt character of the source considered. Before -13:00 LIT, the patternsharplydiffersfromthe observations. However, changes portrayed in Figurel c, one mustconsider temporal computed magnetic activity (KP= 3+)occurs variations withinthe geomagnetic massspectrometer. To do so, wenotethata fairlyweaker we performed numerical trajectory calculations forwardin time during this time period, which may correspondto distinct of theO+ outflow[e.g.,Yauet al., 1986].It may froma givensourcein the topsideionosphere and adoptinga characteristics time-varying potentialdropas shownin Figurela. In view of alsobe thatthis differencebetweenthe computedpatternandthe Figures l e andlf, weconsidered anionospheric source of O+ observationsis due to a movement of the magnetopause Thecloserto theboundary is the observation point,the locatedat 11.00MLT andextending over4* ILAT on eitherside boundary.
Theseionswill subsequently feedintothedistantplasmasheet.
of the last closedfield line. Test O+ were launchedfrom this line
highertheenergy of theO+ evenfora steady stategeomagnetic
In fact,examination of thePROGNOZ-8data sourceat distincttimes(by stepsof 10-minutes) throughout the massspectrometer. 10:00-19:00 UT interval. onAugust27 1981revealsseveralboundarycrossings beforethe that the Examples oftheO+ trajectories achieved aregivenin Figure2. last one shownin Plate 1 at -06:30 LIT. This suggests wasdynamicduringthistimeperiod. In thisfigure,oneofthetestionsis initialized at 76*ILAT (solid magnetopause it mustbe stressed that line)whiletheotheris launched 10minutes laterfroma higher Returningto the aRemoonsequence, ILAT (dashed line).It is apparent fromFigure2b that,in both the goodagreementdisplayedin Figure 3b was obtainedby cases, a significant energygain(from300 eV up to -600 eV) is shiRingthe numericalresultsby -15 minutestoward earlier
by considering that the O+ injections realized following a -1O-minute timeof flightastheO+ travels timesor, equivalently, respond to variations in the convection rate(AE magnitude) with a time delayof the orderof 15 minutes.Within the limitsof the model, this estimateis consistentwith that obtainedby direct comparison of the energyspectraand the AE variations(see phasing between theO+ orbitandthetime-varying convectionintroduction).This time delay is significantlysmallerthan the electricfield(Figure2d) leadsto substantial variations in thenet time of flight of the particlesfrom the ionosphereto the (of the orderof 40 minutes;seeFigure2), but it is particle path.Mostnotably, theO+ launched froma higher ILAT spacecraR
through a regionof enhanced fieldlinecurvature. As canbe seen by comparison with Figure2c, thisenergygainoccursin the paralleldirectionas a resultof curvature drift throughthe convection electricfield equipotentials. It is alsoapparentthat
to thetimerequired for an O+ to traveloverthe (dashed line)whichshould intercept thespacecraft at a latertime comparable anda lowerZ heightin thesteady stateapproximation, is actually distancebetweenthe region of enhancedfield line curvature In other recorded at a position similar tothatoftheO+ originating froma (wherethe gain in energyoccurs)and the spacecraR.
500 2OO
800 t
c
200 •'
lO
5
250 .,., _.•
d
150 5O
o
-lO
-5
o
5
lO
x (RE)
15
20
25
0
10
20
30
40
50
TIME OF FLIGHT (minutes)
Figure2. (a) ModelO+ trajectories. (b) Totalkineticenergy, (c) minuteslaterfrom77øILAT. Closedcirclesin (a) depictthetime parallelenergyand(d) cross-polar cappotentialdropversustime of flight (by stepsof 10 minutes).Panel(a) alsoshowsthe S/C of flight.Thesolidlinecorresponds to a testO+ launched from passwith themagnetopause crossing denoted by an opensquare. 11.00MLT and76øILAT, thedashed lineto an O+ launched 10
:
ILl
:
CONSTANT P•TEN•IAL ' ' ,
0.1
;
.... 1.0
useda simplemodelof time-varying convection electricfieldto trackparticlessincetheir ejectionfrom the ionosphere. The interpretation frameworkdevelopedhere is a simplified description of particletransport duringsucheventsof impulsive
:
convection. However,there are clear indications that impulsive convection is at workandis indeedresponsible for the observed
,
•
:,
::
b.
LIS, namely: (1) numerical modeling of LIS placesthe source of thetailwardpropagating ionsin thevicinityof thedayside cusp,
i.e.,in a region known tobeanactive source ofO+ outflow, and
z
•
' : :-^-•
TI E-VA'RYIN • PO•:E TIA,'L 0.11
;
;
80
•
75
..... ILl:
7o
,
,
i
•
i
,
180
!
i
i
'
:
:
:
:
.
:
•
•
: :
• 17o •
field variationson shorttime scales.It may be that part of the electricfield intensification is of inductivenaturebut the present
,
-•
=O
'
: i
d
ß
,
' ,
10 11 12 13 14 15 16 1'7 1'8 19 TIME
Fi8ure 3, Computed O+ c•c•
(2) steady-state plasmaconvection cannotleadto a dispersion patterncompatible with the observations. In contrast,the repeated injection structures aswellasthefluxdropouts between themare adequately reproduced if oneconsiders largeelectric
UT
V•atio•s at •OGNO•-8
studylumpsthisinduction effectwiththelarge-scale convection. Therapidchanges oftheconvection electric fieldleadto phasing effectsduringtransport; hence,a highlyvariableenergization of theparticles asfeatured in theobserved LIS. Aclmowledgments. Supportfor OLV and LAA camefrom ISF grant MQ8000, RFFI grant94-02-04232,and from INTAS grantINTAS-932031.
References Coffey,H. E., Geomagnetic andsolardata,J. Geophys. Res.,86, 11,470,
(•ca• solid]•cs) versus timeass•8 ci•c• (,) co•s•t o• (b) 1981. t•c-v•8 c•oss-po]•cap•tc•tia] •op. • •csc p•c]s, ]J•t Kamide,Y., andW. Baumjoham•Estimation of electricfieldsandcurrents study magnetometer data for the solid]•cs s•ow•c obsc•cdc•c•syof •c ••• O+ Qux from internationalmagnetospheric
(see•i•c
]c). •c]s
(c) •d (• •cs•ctivc]ys•ow•c O+
•fia] •T •d pJtc••8]c. •c Jo•s•c ]a•c•cd • 300 cV •c• (•o•o•] •s•cd ]•c • (,) •d (b)) •om a so•cc cxtcM•8 ovc•4ø•T o• ci•c• sideof •c lastclosedfidd ]•c (locatedat 75• •T • T-87;•o•o• •s•cd ]•c • (c)). words,thenumerical resultssuggest thattheobserved LIS donot
resultfroma temporal modulation of theO+ source in thecusp
CDAW 6 intervals: Implications forsubstorm dynamics, J. Geophys. Res., 90, 1305, 1985.
Lundin,R., On the magnetospheric boundarylayerand solarwind energy transferintothemagnetosphere, Space$ci.Rev.,48, 263, 1988. Mauk,B. H., Quantitative modeling ofthe"convection surge"mechanism of ionacceleration, J. Geophys.Res.,91, 13,423,1986. Maynard, N. C., and• J. Chen,Isolated coldplasma regions: Observations andtheirrelationto possible production mechanisms, J. Geophys. Res., 80, 1009, 1975.
Richmondet al., Global measures of ionospheric electrodynamic activity inferredfromcombined incoherent scatterradarandgroundmagnetometer observations,,/. Geophys.Res.,95, 1061, 1990.
region(which would take too long to propagatedown to PROGNOZ-8)butfromthetime-varying convection electricfield actinguponthe particlesduringtransport.This mechanism is Tsyganenko, N. •, Globalquantitative models of thegeomagnetic fieldin reminiscent of thatdiscussed byMauk [1986]in the innerplasma thecislunarmagnetosphere for differentdisturbance levels,Planet.Space $ci., 37, 1347, 1987. sheetwherebyphasingbetweena surgingelectricfield andthe of plasmain the magnetospheric tail lobes, particlelongitudinal motionleadsto repeated injection patterns. Vaisberget al., Measurements Finally, it shouldbe pointedout that, due to the strong Adv. SpaceRes.,in press,1995.
variability oftheO+ driftpathswithtime(seeforinstance Figure
Volland,H., A modelof the magnetospheric convection electricfield, or.
Geophys.Res.,83, 2695, 1978. 2a), temporary flux dropouts areobtained in Figure3b whichare Waiteet al., Ionenergization in upwelling ionevents, in IonAcceleration in consistent with thoseobserved. Thesedropouts call for a limited
theMagnetosphere and Ionosphere, Geophys. Monogr.$er., vol. 38,
extension ofthesource regionin theionosphere. Indeed, it canbe editedby T. Chang,AGU, Washington, D.C., 1986. seeninFigure3cthateachinjection involves O+ originating from Yau et al., Acceleratedauroral and polar-capions: Outflow at DE-1
lowerILATs dueto the intensifying magnetospheric convection altitudes,in Ion Accelerationin the Magnetosphereand Ionosphere, (notein Figure3d thatthe ionshavepitchanglesin therangeof Geophys. Monogr.$er.,vol.38, editedby T. Chang,AGU,Washington, the PROGNOZ-8instnmaent). In contrast,after eachinjection, D.C., 1986. the upperlatitudinallimit set on the sourceregion(79ø ILAT) D.C. Delcourt, Centre d'•tude des EnvironnementsTerrestre et prohibits particletransport fromhigherILATsto thespacecraft. Plan6taires, 4 AvenuedeNeptune,Saint-MaurdesFoss6s, F-94107,France. (e-mail:delcourt(•cetp.ipsl.fr) J.-• Sauvaud, Centred'EtudeSpatialedesRayonnements, 9 Avenuedu cnes.fr) Using numericaltrajectorycalculations, the purposeof this ColonelRoche,Toulouse,F-31029,France.(e-mail:sauvaud•cesr. O. L. Vaisberg,L. • Avanov, Space ResearchInstitute,84/32 paper was to provide quantitativeinsight into the tailward St., 117810Moscow,Russia.(e-mail:ovaisber%esoc 1.bitnet injectionsof O+ ions observedby PROGNOZ-8in the Profsojuznaja •frmop 11.cnusc.fr) magnetospheric lobe.These injections which werefertoasLobe J. L. Burch,and J. H. Waite Jr., SouthwestResearchInstitute,6220 Ion Structures (LIS) exhibita uniquepatternof repeated inverted CulebraRoad,San Antonio,TX 78228. (e-mail:hunter•swri.space.swri.
Summary
Vs. A clear correlation was found between the observed LIS and
edu)
themagneticactivity(asdetermined fromthe,dEvariation).This suggeststhat suddenenhancements in the magnetospheric(Received: June5, 1995;revised: August22, 1995;
convection rateaffecttheO+ duringtransport. Onthisbasis,we
accepted: October9, 1995.)
