\

. . . . . . . . . ..-. ..d, u . . . . .-. —-. ..,, ,494, . ... !.

.’” Y*. ‘: ,f,, “1

1

Attenuation Distance of rJow Frequency WavegUp~troam of the Pre-Dawn Bow Shock:

0 GMY1’AIL and ISEE3 Comparison

‘r. Sugiyam~l, 7-’. Terasawal, H. Kawanol, T, Yama.motd, S. Kokubuna, L, A, Frank4,

K. Ackemon4) and. R. 7’, ‘J’mwutmi6

Roceivod _ _—; accepted —_______

* to be submitted to the Geoph@cd kwxmh l.dkrs, 1994,

Short title: BOW SHOCK [JPSI’REAM WAVES

—. . —- . . . . .-—

1 DEPP, the University of Tbk.,YcJ, Tokyo, Jama

21SAS) Kanaf@wa, &tPun

‘STEL, Nagoya University, 7 byokawa, Japan/’14Dept, of Physic~ find Astronomy, the University of 10WQ, Iowa

‘,Jet, Propulsion Laboratory, California lnotitute of Technology

.

), ..- . .

. . .

.,

- - --- --.4-. . . . . . . . , - 4.*4-AS —.. U* IhMffi

T2

Abstract, We have made a stat, ii%icd study of’ the spatial distribution of low

frequency waves (-0.01-0.1 Hz) in the region upstream of the prodmvn to dawn side

b o w shock (-51J F@ < X < 15 Re) using bc)th GIXM’ATL and IS1313-3 magnetomcle~

data. We have found that the wovc amplitude dependence cm D ad X,, where D is

s tho di6tamcc from the bow shock and X, the x-uuuxdinate position of shock foot point

of the IMF, can be de~cribed b.y u functional form of A exp(X./f,x - ~~/~D), with the

characte~istic attenuatiw distances, ],x w l,D N 50 Re.

Introduction.

. . . . . . . —---- .—— . . . . .

. .

Tho low frequency (< proton Larrnor frequerlcy) shock upstream waves have

been studied extensively in the ccmhxt of the wide-spread dissipation process at the

quasi-parrdlel shock [l%i~fickf, 1969; HoflJc et d,, 1981; l,e nmi $f?/ssell, 1992 and*refereuceti therein], At the shock front, suprat,hm-mal ions (> several keV) are injected

u~stream by the sperwlnr reflection process [Pa.sehmann et al., 1980] and/or the proceBs

intrinsically related to the shock formation procw6 itself [H%& et al., 1990; Scholer

and l?urgessj 1992], These ions then excite low frequency magnetic wtweti through the

ion-ion beam cyclotron instability [Bornc#, 1970; JVuhmulx urd ?’emsawuj 1981; W:nske

cmd Lcmv, 1985). Extensive studies of these wave utid ion properties, however, hmv?

been made mainly for the upfihwrm region of X >-10 Re, and ?hc study of upstream*Iegicm d X <-10 R&? is Qll!te hmited, In thlR letter, we prmerh the resdt of 6t at istical

study of wave amplit,tlde rlistribut ion in the wide region of -50< X < 1 S Rc, utilizing

the mngrmtic field data from both ISE12-3 rmd GEOrLAIL spacecraft,

Obwnwat ions.

Figure 1 shows the orbits oft heae two spacecraft projected onto t be GSE (gewxmtric

solar ecliptic) XY and X2 phmes. A dashed curve in Fig, 1 shows the nominal shockDlocation [Faificld, 1971], (Average solar wind abwraticm is assumed to be 40,) ‘l’he

ISEF>3 spacecraft traveled the ups~ream region of the pre-dawn bow ~hnck during the

period of 24-30 Septembw, 1983, Temsawa et d. [1985] riimussed the properties of

euergetiu ions (>30 keV) observed during this upRtream interval, and concluded that

the accekmtion of these ions mainly occurs in the near-earth upstream region, and that

the particle acceleration at tho di~tant bow chock is weak. In this pape~, we study the

. .._ . . . . . . .

~

.,4

uptitlumn wave activities observed with IS1~F~3 mfign?tic tlcdd experiment [F%andscn et

●at., 19?8]. A decade afl,or (5 -9 August, 1993), the GEOTAll~ spacecraft went through

the upstrmm rcgicm of the pre-dawn bow shock on an orbit eimilar to ISl?i3-3’a but

clnsw to the nominal shock surface, Tho magnetometer experiment [Kohhm et al.,

1994J also showed tho exietonce of lorgc aw,plitude low frequency wave activity cluling

this upBtream period.

Figure 2 and 3 show tbe 6 mill avel~yxj of 3 twc magnetic field dat,fi from lSE13-3

and GEOTAIL, respectively, Panels show from the top the total magnetic field intermit y

E, the Iong!ttldinal angle 8, and the wimutha.1 angle ~ (in the GSE coordirmte8). The●

bottom pa.rwl.s show the normalized fluctuation arnplitudm $B1/l~l, where Jl?l k the

,5-rein standard deviation of the magmtic fieId fluctuation in the direction perpendiculti

to the averago magnetic flcld direction, To avoid the eflect of solar wir.d diwmtirmitlcs

or bow shock crossings on #~J., we have macle the followillg sdwtion: First, wc compare

~, ~, and ~ for successive 5-rnin ink~vak, of which the start times are shifter! by 1

min. If either ~, ~, or ~ changed more than 1 n’1’, 2“, or 4U, we exclude these intervals

● from the plots of 6B4/1~], as w?]] m from the following statistical analysi~, At the top

of Fig. 2 and 3, ~hadrd bars indicate Wheu the spacecraft were upstream of the bow

shock, Since G120TAIL cruised close to the ttomirIcJ bow shock location, it cromed moJe

frequerIt ly the shock front than ISEE-3 did, The ISEE-3 obsel vat ion clurhg the period

of 2526 Scptcmbcr 1983 iri not included, since th”ia iutelval wm affected by the passage

of a corotating solar wind stream [ THWUWU et al. 1985].

‘J’he rnague~ic fluctuation shown in the bottom pnnels of F@. 2 and 3, were kept

* at high level (*O. 1-0.8) throughout the N pst ream observation intervals except eomc

intermltterh disappenrmmes. ~kkam the inspection of the high time resolution maguetic

field data (6 HZ and 16 Hz srtmpling for ISFR3 rmd GEOTAIL), we have confirmed

that these large amplitude fluctuation indicated the existence of the upslMtmi wtives

of +0.01-0.1 Hz, F’@m 4 shows a typical example 01 the prover spectrum of the

pclperdiculw ahn~uuerit observed during the interval of 1 :x9-1 :4!? UT on 6 August,

1993. A broad peak around 0.05 Hz with a high frequency tail k similar to what i~

usually observed in the near-earth upstream region several W behind tbc ion foreshock

boundary [lx and Rudl, 1992], Since Z’emsowa ct cd, [1985] showed that the intensily.

of up~troam ions (> 30 koV) in the pre-drwm upstream qiou i~ maximized whe~ the

IMF ie in tho nominal Parker’s spiral directioti (d w 0° and @ *135” or 3150), we h~ve

checked how wave intensity dejwudti UII the IMF direction arid found riepnnclence simila~

to that found fol lh km iritcusity. ‘To make a Statisticrd slmiy, we have selected 163

(05) mm-overlapping 5-rein i-ntcrvds from ISFT’-3 (GkWTAIL) observations, during

which the IMF hnd # = [J” + 15° and ~ = 135 +. 30° or 315 & 30°, lhc normalized

filwt,uation amplitudes &Wl /1~[ for theao selected intcrvolo are shown in Figure 5a and.5b, where the a.bccima rcprcscnts the coordinate X,, which is tLe XCs~ coordinate of

the shock foot point of a. nominal IMF line (i,e, a field line with 0=0° and @135Q Or

316°) paining through each of Lhesu ~pacemft. The GBOTAIL obwwvmion on Aug. 5

1999 ia Hot iucluded in Fig. 5b, since the spacecraft position was >5 FM behind the

mmi.urd 6hock posltiou (Fig. 1).

We observe in Fig. 5a and 5b that the wave rm~plitudeG show dependence on X,

increasing toward the shock subsolar point (at X8 - 14 Re), Fig. 5C shows the clist awe,

D along the IMF line from the nominal shock surface to the spacecraft, which we expect

to bc rmothcr controlling factor of the wave iu ixmsity. Sipce GEOTAIL was clom to

the bow Bhock, the dataset rieenm to have included large amplitude WRVPS tit.hin the

shock ~amp tegiou. III Fig. Sb, the nomird upstrwun intervaiR (open circles for 45

iIltm-val~) are discrirpinated from the near-shock intervals [dots for 20 intemls), within

30 min of which GEOTAT14 c.mssed the bow shock. Solid curves in Figure 6a and bb am

. the rt?mlt$ of the least-square fitting of the functioned form of A exp(X4/Lx - ~/~D)

to the combined data sets of MIX 3/G EO’l’AIL obaerwt ions, where the uetir-shwk

intcmala for G EOTAIL were omitted, The at teuuatiou dist auces are LX = 545- 9MP

6,

. . . . . . . . . . --— -. —- .- . . . . . . . -. —.

and ~JD = Gl k S2RC with A =- 0.404-0,04, Accounting t,hc riifhmnce in nurnbcrs of

5 ruin intervals, we have set the wmistical weights of ISIQL3 and GEOT.41L with a

ratio of 1:4. l’he above Matistic.al result shows Lx - I,D. ]nducling the GIKYI’A]L

nt?9T-~hock data, we obtain Lx = 554. JORn and LD = 36& 16Rc with A = 0.43A 0.04

(dashed curves in Fig. 5a and 5b). In this calculation LD is significantly smallw LhtiJ~

Lx, However, I.D ~ecms to bc undcrestirrmted here owing to the cuxm.mimtion of data*

within the shock-ramp region,

DiBcuBsioIl,

We have compared lAe upstream wave observations from ISEFW and GIN-WAIL,

whose acqubition times were separated over a dmwk. I@ such a compwison to be

possible, we should have a sirnilm Mar wind condition, The basic solar wind parameters

are tabulated in 7%ble la and lb [Rame et 01., 1978; Fhnk et d,, 1994], As seen in,

t,he tables, the sol%r wind conditions woro riot cornplctcly identical: The Alfv4n Mach

numbers MA in the G130TAIL period were generally larger than those ill the ISEE-3

period. (Note that thiB difference in h’fA is mainly caused by the higher number dmmif,im

in the latter period ~hau the former. The ranges of the mlar wind velocity themselves

overlapped, and were within the nominal variation width. ) Under the high J’fA condit io~

the bow shock surface L9 expected to shrink behind the norrijnal pooition, BO that the

actual ftedcl-filignwi distance D for GEO’I’AIL would be larger than th&t Bhown in Fig,.

%. The underestimation of D for GEOTAIL might have led us to overestimate the

attenuation chum ~D. ]]owevcr, the fact that we observed bow d.wck ul-omings cm

Aug. 7 indicates that the effect of high &f* on the shuck position was not subBtanti&l,

For complete discussion, we should use the fast rnagnetofionic MIMh number Ml,

hlSWid Of MA. uRfLIItUIItitdy, &fF’ fOr the I$~!F>~ p?TiOd is IiOt available, SkCC! tho ion

temperature wss not known. For the fnrther refinement of the estimation of LD rmd l.~,

we are m~j~,ing the compilation of the datamt frcm the another C130TAII, orbit in thee

7

. . . . . --- ----- . .- ” - - - - - - - - -—.- *mAa”.<..*a,

wxio,d of Jurle-July 1994 when the sImcccraft prosed through the region more upotrcrmi

. than those in Fi,gnre 1.

We have found that the characteristic attenuation dickamcce aloIig the IMF, L~,

and along the shock surface, Lx, arc N 60 Re. These attenuation distamm we much

longer than that obtnir,cd in the near-earth upstream ~eg,iou (*15 Re, Fuirfield, [1969])

mid that for the discrete wave packets (N2- 3 Rc, Le and llusscil, [1992]). 7 ‘he difference

in attenuation distauces may reflect different ph~icd processes working in the difhrcmt

PULU uf the upstream region: The shortmt distance from I~e and Russell suggcmts thatv

the whistler wave packet, prrdmbly disperse very rapidly, Fair+ eld)B number eeem8 to

simply represent the distance fox which tho ions can travel before their isotropizaion by

the self-excited waves (SW+ o,g, Mitchell ct al, [1983]). ‘The wavm diacumed iu this paper

have had more time to evolve spatially and tempotall.y tlmu waves treated in two earlier

papcm. Since the particle observation (hmti of >30 keV) suggests thfit there is not a

lot of additional free emxgy in the pre da,w~l upstream region [ lkrumwa et oL, 1985],

Lhe large scale size there would imply that the waves are not rapidly damped, However,w

to study the variation of the mailable free energy, we should wait for the observational

stndy of wwers-1 -30 keV ions in this region, which wc shall plan to start in near fum~e,

Aekuowlcdgments. We am gJ ateful 60 all GEOTAII, and ISEE-3 science rrie.mbrm

for their collbhoratio~. portions of this work weie doue at the Jet Propulsion Laboratory,

C!alifomia I.mtitutc of lhehnolo~, undar contract wiLh NASA.

●

. . . . . . . . . . - .—.. . . . . . . . ,. . . . . . . ../. —-- —- —.-—.7..—

. . . .

References

Brmm, S. J., J. R, Aflbridge, H, E, Fdhaueu, J, P, Glore, H, L. Hawk, and ,?, Chavez, lSEE-C

solar wind plmma expetimcut, XEIW ~uwr. Geo~ci, Mectr., GE-16, 160, 1978.

● lhrnc~, A., !l%eory of gener~tiou of bow-shock-awxiated hydromagnetic waves in the

upotrcrm interplanetary mediutr[, C’om& Elcctwlyn. ?, 90, 1970.

k’aidleld, D. Il., Bow shock aseociatad waves obmved in the J’ti upstrwrn interplanetary

medium, J, Geoph~s. Ra4. ?~,3641-8tW3, 1969.

Mrfidd, D. H,, Average and unum,ral locatione of the c(uth’s magnetopause and bow elioclx,

J. (;mfihya, Res. 76, 6700671%, 1971.

handfwn, A. M. A., R V. Chnnor, J. van Amerafoor+, and E. J. Smith, The ISEEC vector

helinm rnagndometer, IEEE !7kms. Ceo#ci. &’lectmn., (W-16, 196, 1 9 7 8 .,

I%nk, L, A,, K, L, Ackmeon, W, R. Paterson, J. A. Loo, M. R, English, end G, L, Pickctt,

The comprehensive plasma imtrtmwntation (CPI) for tho GEO1’AIL epoccoraft, 3.

Geomag. Geoelectr, 46, 23-37, 1 WM.

Iioppe, M. M,, (1 T. Russell, L. A. Wink, “1’. R. Wwtman, and E. W. Grwmtadt, Upstrcmn

hydromagnetlc waves and their amociatkm with Iwckstrearr,{ng ion populations: ISIW

1 id 2 ubwrvatlor18, J. Geophya. Re8.8ti, 4471.44! )2, I!JR1.

Kokubun, S,, T. Yau.uuwto, M. H. Acufla, K, Haymhi, K, Shiokawa, and H. Kawano, The.

G130TAIL maguetic fielcl experiment, J, Geomoj, Geoelectr. /6, 7-21, 1994.

Le, G,, and C, T, Rumell, A Btudy of ULF wave foreshock morphology -11: Sp~tird variation

of ULF wave6, I%nct. $paw SCi., ~0, 1215-1225, 1992.

Mitchell; D. G., E. C. Roelof, T, R, %nderson, R, RA&rd, and K.-P, Wenzel, ISEE/lMY

obwn-vatiom of simultrmeoue upgtrearn iou events 3, GcophY8. Re&48, 5635-6644, 1983,

Pamhrnann, G., N. Sckopkc, J, R, Aebridge, S. J, Ihrue, and J, T, Gu~lirqL Energlzation o f

solar wind ione by rdection from the earth’s bow shock, J. Gcuphuu. Re8,85, 4689-4693,

. 1980.

Scholer, M., and D, Burgam, The role of up~tream wrwea in mpercritical quasi-parallel shock

r~tbr-rmtion, J. Geophps. Re~.97, 8319-8326, 10!I2.

. . . . . . . ..- .._—— . .. -.-.....” -*.—

. ..

lMMawa, T., M .

%mdereon,

Scholer, k’, M. lpvich} D, Hoveetadt, B. Kleckor, G. Gloocklcr, ‘I’, R.

K,-P, Wenzel, and M J. !hith, Particles upBtream of the pre-dcwn bow

hock: ISI$E-S obmvations, Gcophv~. A!M. ML If!, 37S-97%, 1986.

WaLwdw, Y,, and T. Tkrmawa, C)X1 the excitation rnm!baninm of the low-frequency upstream

wavet+ J, GcrJphya, Rea,89, 6623-0030, 1984,

WinBke, D., and M. M, Leroy, l)iffu~e ioxm produced by ehxtmrnagnetic ion t-mm instability,●

J. Geophpa. Rc8.89, 2(?73-2086, 1984,

Winake, D., N, Ornidi, K, D, Quesl, ad V, A. Thom~, IUformixlg supercritical qlwmi-parallel

chocks, 2, Meclmniam foI wave geuaatlon and flont re-formation, J, f%!oph~~. Rm. 96,

18821-18832, 1990,

—._.This manuscript WM prepared with the AGU 14~ macros vS.0,

..- —.. — ----- —— . . . . . , ,.-. .

10

●

Figure 1. UH3E-3 and GEOI’AIL orbits timing

t he perioch on the GSEXY plrmc, bctwoon 28

September and 1 octobar, 1983, and bctwccn 4 and

10 August, 1993, respectively. The X% projection

(panel x, top) and the XY projection (pmol b,

bottom) are RhOwn. Mm show the poaitioas at

00 UT of each day. A daRhacl c~we in panel b●

abowa the IIOmintd bow ahmk fNltffLC6.

Figure 2. ISDD-3 observablou o f the rmignctlc

~old. T h e inttity fi, +e latitudimd IU.U@ d,

the aabnuthrd angle & the normallzxxl fluutuution

amplitude (WC text) &e ehowri from the top.

Figure $. GEX)TAIL obecmtion of the magnetic

field with the MUM format m Fig. 2,

F@m 4. The power apcctrum of the rrmgnc.tdc

field fluctuation perperidieular to the avemgcd field●

rtirwtirm. (’The spectrum i~ caleulatod from 4$00

point Fourier ttra.n~thrmation with 5 degree~ of

freedom,) Obsemmtinn WAR made between 1:39 and

1:48 UT’ on 6 AWu~t, 1.LW3. ‘John dot line is proton

cyclotron tkequency.

------- ------ . . ..— . . . . . . . . . .

b

.

Figure 5. Pnnela a and b show the normalized

amplitudes of the lqmtxeam traruwerse ma~otic

field fluctuation ohwrwl by ISEIL9 (top) ~,nd

GEOTAIL (middle), req-wthdy. Panel c

(bottom) ahovm the distance~ 11 from the nomird

bvw shock tm.rface to the spruxcraft. ‘1’hR cllrves

in pa~wlM a and b are the result of the exponential

flmctiuu fitting (see text).

--— -—. -—-— ----- -——.——... . . .. .

●

12

fihlc la. Solar wind paremctcro for tho ISEE-3

upstream interval

-——._._—. _______ ., ___ ----- -- . . . ..— —. —

date v e l o c i t y dermity lllag~t%k hj*

yyJIMAl (b/B] (1/cm3) f i e l d (nT)_. . . ..-

83092? 510.630 2-4 6-7 6-7

830928 4f@-600 3 . 6 6-7 &8

830929 42r)-4fKl %5 b-6 8-9

830930 3s0-390 2-b S-6 4-7— - . . . -—— —

.

Thble lb. Solar wind parameters fcm the

GEX3TA1L upRtraam interval

. ——. . .—— ___

dato velocity dcneity rI’lb~rLetk hf~

yymrndd (lcm/s) (l/crnl) f i e l d ( I I T )

930806 421-465 N.16 7-8 8.11

9S0807 387-438 7-13 7 ‘7-1 1

930808 462-303 3-8 b.? 6-11

990809 468-487 &9 7 “(-1 u. . . . — — .

b

.— -- . . . . . . . . . . . . . . . . . . . . .-— -m..,.. ,,-,s,x—*—

. .

. .

GEOTAILL._ +10#l!.__~”- “ - ~ ’ - - * _ _—-*-._--.t~_..~_ -

‘+

—--- .*.-.+ _..*,:j:m_:---- ~--t’”---t ——t———GSE-X (FIe)

-, “22*—--{.—ISEE-3 “lo’

GSE-Z (Re)

GSE-X (Re)~ ._.____+_ .._l____

-80 -60

‘ “w

-–--1

1- ‘- “1 ‘--- ““i -—-+- —--+———

-40 .20

\ \ \ . \\\\\

)\I

—.1

/I

/,’t

.’,’t

)’,

30

-60

--l

+20

r’ . . 1GSE-Y (Re)

ma)a’)l--

C9I

UJLUU)

FM

. .._ _ . ----- — -—-—---—.

—— .--ap

I

.

,.,.

%

1

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dlW

—

.-—

—

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co0-)ml

Qa)

CAC!&

Cic1)mt-OJ

,.

. .,:

::

,..!

,.

,)

‘(.I.,,, ,!‘!1.., I

.. .

ccl,.rJ~’)

. ..0“‘A,–., ,,

. ..T<

, . .

GFOTA!L Magnetic Field 1993

Upstream region

I

5 Aug. 6 Aug. 7 Aug. 8 Aug. 9 Aug.

30

0

0

-1 018.0.0

.’.

1 .8+0

N-ZN

1-S

1(3 0*

1.0-2

1 e-3

1,0-4

1 e-5

. . ------

Spectrum6.Aug 1993. I :39+ .48

i

;i

\

0.001 0.010 0,100 1,000

Frequf?ncy [Hz],-

-... .-. — ..-. -—- . . . . . . . ---- .—-—---~.,●

0 8.

06m

04●

0 28

0 0●

T —.— ———-———_

00

0

/

ISEE-3

.;

i

23● ——

CLE

1a-1---~-r—---t-————~r—————— ‘&——r———

-50 -40 -30 -20 -10 0 10 20

0 8●

0 6e

0 4m

0 2.

0 0m

——-.—-— . .

CiEOTA

●

Q 0 0 6 6

0 -$ ;n~~.,. ..;”2-0 i

8 0 ‘c) ~j. ,.!.+~w ~o. . . . . . . . . . . . . . . . ..-.— - - - w J f ’ -

0- .0 0

!?i

Eia

i

--l~-—’—--l-—————r”——+———

20-i ———~-— -—-.——.--.— —

100

.10

-i. . . . . . . . . . . . I

/--———--””-’-- ‘~. . . . . . . . . . . . \. . . . . . . . . . . . . . . . . . . . . . . . . . . . . - . . . . . . . . . . . . . L

I

~--—,~-—-,— l-+-———l————1J

1-,.-.. “ T

-30 +() -1 () o 10 20

Xs