Large- and middle-scale phenomena in the interplanetary medium: Prognoz 7, 8, 10 observations

Adv. Space Res. Vol.9, No.4, pp. (4)117—(4)121, 1989 Printed in Great Britain. All rights reserved.

0273—1177/89 S0.00 + .50 Copyright © 1989 COSPAR

LARGE- AND MIDDLE-SCALE PHENOMENA IN THE INTERPLANETARY MEDIUM: PROGNOZ 7,8,10 OBSERVATIONS G. N. Zastenker,* Yu. I. Yermolaev,* V. I. Zhuravlev,* N. L. Borodkova,* Z. Nemecek** and Ya. Safrankova**

5Space Research Institute, Academy ofSciences, Moscow, U.S.S.R. * * Charles University, Prague, Czechoslovakia

ABSTRACT Some interplanetary phenomena with time scales from several hours to several days are considered: (1) low speed solar wind regions with specific large scale fluctuations of h 8avy ions abundances, (2) large ion flux increases with large (up to 10—20 ) deflections from the solar direction and (3) plasma flows behind the interplanetary shocks (both isolated and combined into the series). The variations of elemental abundances and of charge states of various ions observed continuously within 2—3 days time intervals are used to evaluate the variations of chemical composition and electron temperature of the solar corona. Slow ion flux increases with sharp decreases and with strong changes of ion flow directions tend to be associated with interaction of flows with different velocities near the interplanetary magnetic field (IMF) sector boundaries. The main characteristics of the interplanetary disturbances by shocks - the dynamical pressure jumps and the time of motion are studied as a function of the total disturbance energy. INTRODUCTION The experiments made in 1978—1985 for studying interplanetary space on board the Soviet high—apogee Prognoz 7, 8 and 10 satellites contributed much to understanding some events in the interplanetary plasma which have a time scale from several days (large—scale) to several hours (middle—scale) /1—3/. VARIATIONS OF THE SOLAR WIND HEAVY ION FLUX Measurements of the elemental (mass) and charge composition of the solar wind ions are of special interest since they can provide the information about the composition and temperature of the solar atmosphere~/4,5/and, respectively, about the variability with various periods of thes~aiost significant characteristics. One of the methods for measuring heavy ion components, that is the energy analysis with electrostatic analyzers, has been successfully used in several solar wind experiments /4—6/, in particular, on board the Prognoz 7, 8 and 10 satellites /7/. It is significant that,in contrast to many other experiments, the Prognoz 7 measurements involved several long—term (up to 4 days) continy— ous and rather detailed observations of heavy ions which made it possible to study their variability /8/. The analysis of the data acquired from November 1978 to June 1979 showed that heavy ions are observed in the solar wind during 90% of time when the conditions are favorable for the use of the energy analysis method. For further studies six intervals were chosen which were characterized by the low velocities and low temperatures of protons and ~,—particles in the solar wind (see Table 1). Figure 1 shows, as an example, time series of hourly averaged observations for one of these events: the fluxes of oxygen, silicon, and iron (in terms of the detector count rate), the silicon and iron density with respect to oxygen, the estimations of oxygen, silicon, and iron ionization temperatures, hydrodynamical parameters of the flow — the ion density, proton and o~~~particle velocity and temperatures. The event shown in Figure 1 can be referred to the interstream flow (IS type) — the low—velocity flow between two high—velocity streams. Besides the above flow type the noncompressive density enhancement (NCDE) and high helium abundance (HHA) were also observed (4)117

(4)118

G. N. Zastenkeretal.

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Fig.1. Dynamics of the hourly—avera— ged values of oxygen, silicon, and iron abundances and ionization tempe— ratures, and proton and ~,—particle flow parameters.

I,~,I,.,,I.,”.,I 1~ /0 71

20

n,cin~

Fig. 2. Dependence of helium, oxygen, silicon, and iron abundances (with respect to a) oxygen and b) hydrogen~ on the solar wind ion density.

(see Table 1).

Averaged parameters (solar wind) Period

Vp, km/s V

,

km/s

Table 1

(1) November 16—19, 1978

(2) November 24—26, 1978

(3) December 2—4, 1978

(4) December 10—13, 1978

(5) February 6—8, 1979

373÷32

452+20

319÷14

306+14

374÷14

298+12

348+47

363+31

464÷27

300+44

292+12

376÷17

287+12

343+57

3.1÷1.5

4.9÷1.9

Tp, eV

5.3÷2.0

10.0÷2.0 5.0÷3.0

3.1÷1.5

T~,eV

6.2+4.4

35.1÷33.7 5.7÷4.3

3.7÷3.1

n, cm~ Flux type

10.9±4.6 IS

7.3÷4.5 12.7÷6.5 17.4÷8.0 IS

IS

NCDE

5.0÷2.1

(6) June 4—6, 1979

Averaged over all the periods

26.5÷11.0 5.1÷2.2 13.3÷11.7 6.9÷1.5 HHA

17.5÷2.612.1÷4.3 NCDE

low—velocity wind

The analysis of heavy ion flux variations for all six intervals allows us to conclude, for a scale of several hours, (1) the ionization temperature for all ions remains approximatelly constant within the limits of their estimated uncertainty (~3D%); and (2) the oxygen, silicon, and iron fluxes and their relative abundances vary within the limits exceeding by several times the es— timated uncertainty. Tables 2 and 3 give large-scale variations of heavy ion parameters in intervals of several days. The estimates of the solar corona temperature (see Table 2) for silicon and iron lead to a value of (1.7 to l.B)~l0 K on the average, and are in good agreement with published data /4—9/

Large- and Middle-Scale Phenomena

6K)

Ionization tenperature estimate (lO ion type Period (1) (2) T (0) T (Si) T (Fe)

3.1÷0.6 1.8±0.3 1.6÷0.3

2.6±0.8 1.7÷0.2 —

Table 2 (3)

(4)

3.1÷0.4 1.8÷0.4 1.7±0.1

2.9÷0.6 1.6±0.2 1.6÷0.1

Estimate of the content of helium, oxygen, silicon, and iron Element

Period

(1)

(2)

(4)119

2.9±0.6 2.8÷0.6 1.9±0.4 1.9±0.4 1.8÷0.2 1.6÷0.3

Averag~ the periods 2.9±0.6 1.8÷0.3 1.7÷0.2

Table 3

He/U

46÷35

49÷54

32±23

28÷18

45÷33

38÷33

Si/0.102 Fe/0.102

12÷10 6±4

12÷5

11÷6 5÷3

12÷6 10±2

14±7 8÷4

10±3 11÷6

12÷6 8÷4

He/H.l02

2.1÷1.9

7.9÷5.2

0.6±0.5

—

1.7±1.2

(4)

(6)

Averaged over all all periods 39±31

2.4±2.5

(3)

(5)

0.8÷0.5

(5)

(6)

3.0÷2.8

0/H.l0~ Si/H.105

4.6 5.4

4.9 5.7

5.3 5.6

2.9 3.4

17.6 24.6

1.6 1.6

6.8±5.6 8.6÷6.2

Fe/H.105

3.0

—

2.8

2.8

14.2

1.8

5.5÷4.9

whereas the estimate for oxygen (2.9÷O.6Y1O6K is somewhat higher than the published values. The solar wind oxyge~, silicon, and i~on average abun~ances with respect to protons (0/H ~ 6.8~lO , Si/H ~ 8.6~lO , Fe/H~5.5~1O ), is in good agreement with the results obtained previously/4—9/.However, the heavy ions abundance as given in Table 3 varies more than 10 times from maximum to minimum /4—9/. As seen in Figure 2b, the relative abundance of the heavy ions and o~’—particles decreases with the proton density increase. Several experiments /10/ have already indicated this feature for c~.’—partic1es, i.e.their abundance with respect to protons decreases when the proton flux increases. As seen in Figure 2a, the ratio of helium, silicon, and iron fluxes to the oxygen flux is approximately constant for all intervals, i.e. the fluxes of heavy ions including o~’—particles vary in proportion to each other. As was supposed in /11/ the closed coronal magnetic field in a coronal streamer leads to two effects: (1) formation of slow, cold and dense flux in interplanetary space, and (2) selection of heavy ions due to their motion across magnetic field lines. (See Fig.3). Uualitative change of the ion density and relative helium abundances when spacecraft crosses a streamer region at 1 AU is presented in the right part of Figure 3. Fig.3. Schematic view of coronal streamer projection on the ecliptic plane and ,~ spatial structures of total helium abu~dances in the

DISTURBANCES DUE TO INTERPLANETARY SHOCKS The interplanetary space disturbances due to the passage of the shock waves are one of the most efficient and prolonged events /12, 13/. The significant question is the relationship of the main characteristics of this disturbance with the energetics of the event which causes. Therefore, it was interesting to make the comparison of numerical simulation of the shock motion with the estimates which had been obtained from the Prognoz 7 and B systematic observations of the interplanetary large-scale disturbances caused by the shock passage /14/. The disturbance energy was determined using the set of’ data far the event, integrated over their total duration for

(4)120

G. N. Zastenker eta!.

the kinetic, thermal, potential, and magnetic energy of the plasma. For comparison the results of /15/ were taken. These results were obtained by numerical simulation and represent the dependences of the plasma dynamical pressure jump at the interplanetary shock front on the energy of the initiating pulse in the solar corona. Figure 4 shows the comparison. It is seen that trend (the increase of the pressure jump with the disturbance energy growth) is observed though the variations of the values are very great. The observed energy of the large—scale distrubance~ 1associat~with the passage of the interplanetary shocks ranged from llO to 41~ erg~or the e~ents discussed. The respective pressure jumps are from 10 to 10 dyne/cm . However, the comparison with the calculated curves given in Figure 4 shows that, as a rule, the pressure jumps measured are significantly lower than those calculated for the same distrubance energy. The comparison of the observed plasma dynamical pressure jump with the calculated dependence /15/ shows that the simulating procedure /15/ may have to be computed utilizing some dissipation processes which in the interplanetary medium can lead to decreasing the pressure jump and the motion velocity. However, this conclusion requires more data to be verefied. THE SOLAR WIND NEAR THE STRUCTURAL BOUNDARIES

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I

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-

I ~

Jo’

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I

1~Y~’ U_~LL__~_ T0141 diVIUT IF (N(~f0!’,4~f~/

f

;jh

)

7h

~

z~ ‘.

Fig. 4. Dependence of plasma dynamical pressure jump at the shock front on large—scale distrubance energy. Solid lines are dependences calculated using /15/. Experimental values ar~ divided into groups: 0 — = 0 to 30 , • —~°=30to6O ,O— ~76O,x— — series events.

i~~4~,4

It

Fig. 5. Strong disturbance of solar wind flux and interplanetary magne— tic field.

One of the most interesting features is the deflection of the solar wind flow observed in some cases. From systematic observations on Prognoz 10 (~pri~—N~— vember 1985) we found 7 e~ents w~th the flux increasing up to l.5~l0 cm s and the deflection from 7 to 20 . Their duration was several9hour~. ~igure 5 shows the most intense event. The flux increases up to 2.2l0 cm s . This increase begin rather gradually then the flux is nearly constant during about hour and then falls sharply (during -.-‘ 5 mm) . Simultaneously with this increase the flux deflection changes in two planes: the flux is turned southward from the ecliptic plane by an angle of 200 and concurrently eastward from the

,

Large- and Middle-Scale Phenomena

(4)121

direction to the Sun by an angle of 18°. This flux deflection (27°) exceeds significantly the typical values in interplanetary space. The comparison of the flux and magnetic field variations shows that the flux increase described above is attended by prolonged and rather large (up to 10—15 nT) growth of the field value and by significant turning of its direction. The sharpest turning of the field (during 1—3 mm) occurs near the boundary at which the flux jump is observed. The analysis of long—term (several days) variations of the magnetic field shows that the event discussed occurs near the boundary of the interplanetary field sector at which the antisolar field direction changes to the direction toward the Sun. As has been shown /16/ such flux change (sharp fall after a gradual increase) was observed in the region of the two flux interaction near the sector boundary. REFERENCES 1. 2.

Problems of the solar activity and space system Prognoz (in Russian), Nauka, Moscow (1977) Study of the solar activity and space system Proqnoz (in Russian), Nauka, Moscow

(1984)

3.

Intershock project issue, Kosmich. Issled. (in Russian) 24,

~ 2(1986)

4.

3. Geiss, in: Future Missions in Solar, Heliospheric and Space Plasma Physics, Garmisch—Partenkirchen, Germany, ESA SP—235 (1985)

5.

Yu. I. Yermolaev, Preprint Pr—l2Bl (in Russian), Space Research Institute, USSR Academy of Sciences (1987)

6.

S. 3. Bame et al., 3. Geophys. Res. 75, 6360 (1970)

7.

G. N. Zastenker, Yu. I. Yermolaev, Planet. Space Sci. 29, 1235 (1980)

B.

L. Avanov et al., Czechoslovak J. Phys. 37, 759 (1987)

9.

P. Bochsler, Physica Scripta 18, 55 (1987)

10.

M. Neugebauer, Fundamentals of Cosmic Physics 7, 131 (1981)

11.

3. T. Gosling et al., 3. Geophys. Res. 86, ~ 7, 5438 (1981)

12.

M. Dryer, Space Sd. Rev. 32, # 2, 277 (1975)

13.

A. K. Richter et al., in: Collisionless Shocks in the Heliosphere Geophysical Monograph 38, AGU, 33 (1985)

14.

N. L. Borodkova et al., Adv. Space Res. 6, # 6, 327 (1986)

15.

Z. Smith, M. Dryer, in: STIP Symposium,

16.

3. T. Gosling et al.

3ASR 9/4—I

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#

4, 1401 (1978)