Magnetospheric storm dynamics in terms of energy output rate

Planet. Space Sci., Vol. 40, No. 4, pp. 581--588, 1992 printed in Gz'catBritai~

0037.,...0633/92 $5.00 + 0.00 F-~l~,~lm Prcu plc

MAGNETOSPHERIC STORM DYNAMICS IN TERMS OF ENERGY OUTPUT RATE A. P R I G A N C O V / ~ Geophysical Institute, Slovak Academy of Sciences, 842 28 Bratislava, Czechoslovakia and Ya.l. F E L D S T E I N Institute of Terrestrial Magnetism, Ionosphere, and Radio Wave Propagation U.S.S.B.. Academy of Sciences, Troitsk, Moscow Region 142 092, U.S.S.B..

(Camera-ready copy received 26 November 1991) Abstract--Using hourly values of both the global magnetospheric disturbance characteristic DR, and AE index of auroral ionospheric currents during magnetic storm intervals, the energy output rate dynamics is evaluate~ for a magnetic storm maln/recovery phase and a whole storm interval. The magnetospheric response to the solar wind energy input rate under varying interplanetary and magnetospherlc conditions is considered from the temporal variability point of view. The peculiarities of the response are traced separately. As far as quantitative characteristics of energy output rate are concerned, the time dependence pattern of the ring current decay parameter is emphasized to be fairly important. It is pointed out the more close insight into the plasma processes, especially at L ffi 3 - 5 to be needed for the adequate evidence of the dependence mentioned.

time decay pattern. The magnetospheric response to the SW energy inNumerous studies on energy dissipation in the magne- put rate during intense magnetic storms is considered tosphere during magnetic storms give a useful clue to in tiffs analysis. An attempt is made to identify quanimprove our understanding of physical mechanisms of titatively the modification of the energy output rate for the solar wind-magnetosphere coupling processes (Aka- distinct r parameter models and to trace peculiarities sofu, 1981a; Akasofu, 1981b; Zwicld et al., 1987; Gon- of tile response separately for each of the models. zalez et al., 1989; Pisarskij et al., 1989 and references 2. T H E O R E T I C A L A P P R O A C H therein). The intensification of the ring current (RC) reflects both the solar wind-magnetosphere (SW-M) The analysis of the magnetospheric storm dynamics and magnetosphere-ionosphere {M-I) interaction pro- in terms of energy output rate UT is based on empiricesses, the ionosphere-neutral atmosphere interaction cally derived quantities: playing its role as well. The clear RC signature in the ground-based geomagU T = U D R dr UAj (I) netic field measurements makes it possible to follow the RC enhancement under storm conditions and its decay The R C energy injection rate UDR is a function of the magnetospheric characteristics D R and r: to the quiet time level later on. The RC development is directly related to the time decay parameter r which appears in no way to be con/-/DR = 0.74" 101° ~ ' - ' ~ + - , W (2) stunt (Akasofu and Olmsted, 1987; Feldstein et al., 1990). The option of r values drastically influences the where D R is a pressure-corrected Dst index in n T RC energy injection rate UoR and consequently the to- (Zwicld et aL, 1987; Feldstein et al., 1990) and r is tal energy output rate {IT (Zwickl et al., 1987). a time decay parameter in hours. Theoretical and experimental investigations give a For the calculation of the energy dissipation rat~ in growing amount of evidence as to both the r decay pa- the ionosphere UAj = Uj + UA, i.e. the sum of the ionorameter and R.C intensity dependence on a number of spheric Joule heating rate Uj and the energy dissipaparameters. Among them are the geocentric distance tion rate of aurora] particle precipitation U,~, empirical of RC belts (Akasofu, 1986), the particle concentration, relationships obtained in (Banmjohann and Kamide, energy and composition variations (Wrenn, 1989; Taka- 1984; Sphto et al., 1982) are used: hashi et al., 1990; Hamilton et al., 1989), which have to be taken into account for the adequate choice of the Uj -- 3.2.10SAE, W (3) 1. I N T R O D U C T I O N

581

582

A. PRIGANCOVAand YA. 1. FELDSTEIN

UA =

1.75

AE

1 - ~ + 1.6

) - 101o W .

(.I)

As is easily seen, Uj/UA ,-- 1.3 + 1.6 for disturbed conditions, Uj still prevailing UA until A E > ll0nT. Equations (2)-(4) show that the accuracy of the UT estimation depends on the adequate option of r parameter and the proper assessment of the Uj and UA quantities which as functions of the AE index are defined quite approximately (Akasofu, 1980). The another reason why these quantities suffer an inadequate estimation is that standard A E indices axe likely to be underestimated duriug the storm main phase (Sumaruk et al., 1990). The peculiarities of the AE(e) relationship for e > 5. 1 0 u w were pointed out in (Akasofu, 1980), which was interpreted as the ionosphere decoupring from the magnetosphere (Akasofu, 1980; Gonzalez et al., 1989). On the other hand, the indications of the A E becoming inadequate as an indicator of the M-I coupfing were noted in (Akasofu, 1989). It proves to be the case due to auroral oval shifting equatorwaxd during distu.tbed conditions which is the reason that auroral electrojet current effects remain undetected by the AE(12) network of stations (Banmjohann and Kanfide, 1984; Sumaruk et al., 1990). To overcome this inadequacy of the standard A E indices the recommendations given in (Sumaruk et al., 1990) were used in the analysis to rectify the standard A E indices during the storm main phase according to the relationship:

A E = -9.1 F,, + 326,

(5)

where A E is in nT and F,~, the injection function expressed in terms of interplanetary medium paran~eters, accounts for both the reconnection processes and viscous interaction in the SW-M coupling (Pisarskij et al., 1984): F,~ = -

8 . 2 . 1 0 - 3 V ( B . - 0.67a) 14.1.10-3(V - 300) + 9.4, nT/h.

(6)

The energy transfer into the magnetosphere is controlled by a number of S W parameters. Various combinations of them are suggested to control their relationship with an experimentally assessed RC energy injection rate F~p (Feldstein et al., 1990) given by the energy balance equation:

dDR

F=~ =

DR

d-S- + - - r

(7)

The previous investigations confirm that the reconstruction of the RC energization process requares the proper use of both the injection function and time decay parameter r. Some of the r models ate considered in this analysis. 3. D A T A A N D C A L C U L A T I O N The set of magnetic storms (n=72) within the 19671982 interval was considered. Seventeen intense storms

with DR, .... < -160 n7' were chosen from this set, The overview of them is presented in Table 1. T A B L E 1. L I S T OF INTENSE M A G N E T I C STORMS (DRmax - 1 6 0 nT) WITHIN THE 1 9 6 7 - 1 9 8 2 INTERVAL

Storm February

16-19, 1967

February 2-3, 1969 March 23-25, 1969 March 7-9, 1970 March 31-April 3, 1973 April 13-14, 1973 July 4-6, 1974 August 27-29, 1978 September 25-30, 1978 November 24-27, 1978 April 3-5, 1979 April 25-27, 1979 December 19-20, 1980 Jaly 24-26, 1981 October 20-21, 1981 October 22-23, 1981 March 1-2, 1982

<

D R,,~,~, nT -166

-217 -259 -308 -235 -169 -234 -258 -228 -161 -210 -172 -250 -193 -216 -190 -244

The analysis was carried out within the hourly time scale for the input data. The magnetospheric disturbance characteristic D R and A E index of auroral ionospheric currents for individual storm intervals were used. The SW arid IMF data were selected from the NSSDC Composite omnitape source. To study the magnetospheric response under varying interplanetary and magnetospheric conditions a package of computer algorithms was developed. The algorithms made it possible to follow the time profile of energy output rate UT, as well as UDn (its derivative term and RC decay term considered separately), Uj, and UA constituents of UT hour by hour within the storm interva], these quantities being calculated according (1)-(4). In addition, the relative contribution of individual constituents UDn/UAj into the total energy output rate was considered. The calculation was carried out for two alternatives, first using the standard A E indices (corresponding U~) are meant as original values) and second taking into account modified A E ' indices determined from equation (5) within the storm main phase interval only. Quantities mentioned and their relation to the injection function F,,, and energy coupling function ~ were considered for successive hours during the main phase of 17 intense storms analyzed. The average values of calculated quantities for individual storms were compared within the main phase interval and the storm interval as a whole. The comparative analysis was performed using different RC time decay paraaneter r models. Among them were the following ones:

Magnetospheric storm dynamics

•

583 r = 0.97

the r model suggested for intense storms (e.g., Feldstein et al., 1990) which is referred as the model h 12

r(F=) during the main phase 2.4 < r < 11.5 for 100 ->l Fm I>>_4 nT/h r , h --* r(DR) during the recovery phase 10.0< r < 11.5 for - 300< D R < - 1 0 nT,

,=i 4 i

•

20 2 0.5 0.25

• the r model as derived by Gonzalez etal., (1989) for intense storms - the model III:

r(D,t), h ~

4 0.5 0.25

D,I _> - 5 0 n T - 1 2 0 < D,t < - 5 0 n T D,t < - 1 2 0 nT,

I

12

3~5

j0 "105 IF,I, n r / l l

FIG. I. R E G R E S S I O N P L O T S F O R A V E R A G E V A L U E S O F THE TOTAL ENERGY OUTPUT R A T E U T VS T H E R C ENE R G Y I N J E C T I O N R A T E Fe~ P ( U P P E R P A N E L ) A N D INJECTION FUNCTION F m (BOTTOM PANEL) DURING THE MAIN

P.ASE (n = z2). ~0

1-(D,t), h --*

1

0.5

D,t > - 5 - 1 0 < D,t < - 5 - 3 0 < D,! < - 1 0 - 5 0 < D,t <_ - 3 0 - 7 0 < D,t < - 5 0 - 1 0 0 < D,t < - 7 0 - 1 5 0 < D,t < - 1 0 0 - 2 5 0 < D,t <_ - 1 5 0 D,I < - 2 5 0

.//

,5

• another T(D,t) model (model IV) derived for the analysis as multistep function of the type: 50 25 10 6.5 4.5 3 1.5

I

60 90 IF,~I. n f / h

r = 0.97

• _< 1 0 n w 10 n < e < 5 . 1 0 it IV 5 . 1 0 n < e _ < 10I1 W 10 li < e < 5- 10I2 W e > 5.1012 W,

1

-+

I

30

the r model as a step function of the S W energy input parameter e, introduced by Akasofu (e.g., Zwicld etal., 1987) - the model Ih

) 4

/

30

40

50

60

-i

i

nT

'

nT nT tiT

nT

) hours

nT

nT nT

nT,

7- being an hour greater for the recovery phase. The results of the analysis are displayed in a number of plots and tables.

10 ~a4/

'

~0 "

;i~,.'" "

30 '

40 "

'

50

60

'

'

50

60

"

=

i °4 '21

i i i

> hours

4. R E S U L T S A N D D I S C U S S I O N As follows from (1)-(4) the total energy output rate in the magnetosphere is determined by the RC injection rate UDR and influenced by the energy dissipation rate in the amoral ionosphere UAj. A more detailed analysis of the UAj relative importance in the energy dissipation during intense storms is provided below. Obviously," the amount of UT is tightly correlated with the RC energy injection rate F , ~ . This correlation can be demonstrated using data of the set of 72 magnetic storms within the 1967-1982 interval. In Fig. 1 the total energy output rate average values evaluated for the storm main phase are presented in relation to associated quantities ]ee=p and ~P,~. Here the r model I was used and modified values of A E index were taken

10

~0

~2~ o

i

t 13t

/

i

30

40

' ....

...........

,v

' ...................................

I

, ) hours AUQUS[ ~7-29, lg78 maqneUc s t e m FIG. 2, T I M E

PROFILES OF THE CONSTITUENTS.

UDR TWO

A solid line c o r r e s p o n d s to t h e deriva.tive t e r m dDR/dt and u dotted Une is for t h e RC decry t e r m D R / r d e v e l o p m e n t during the A u g u s t 27-29, 1978 m ~ g u e t i c s t o r m for r m o d e l s I, II, IV. On u horizontal axis h o u r s from t h e s t o r m beginning are indicated. T h e solid line nt the b o t t o m of each

psnel corresponds to the m~in phase duration.

584

A. PmGANCOVAand YA. I. FELDSTEIN

into account. The well-organized relationship UT(ll~'ezp) is strongly evident. The total energy output rate also manifests a sbnilarly tfigh correlation (r = 0.97) with interplanetary conditions described quantitatively by the injection function Fm calculated accordingly (6). It is worthy to add that the tight correlation persists during the whole storm interval, r being ~ 0.80 during the recovery phase. Further analysis is now underta&en to consider intense magnetic storms presented in Table 1. The deeper insight into the RC injection rate quantity reveals the essential role of the v model chosen. Actually, the time decay values drastically influence the RC decay term DR/r in comparison with the derivative term dDR/dt (Zwickl et al., 1987). In Fig. 2 the unsmoothed profdes of two constituents of U~ are displayed. The individual panels correspond to r models I, II, IV. TABLE 2. THE

UT

CORRELATION

It is clearly evident that the derivative term represents the background of RC variability. The gross contribution to the UDn quantity is supplied by the RC decay term. The values of the RC decay term ate directly related to the 7" set values. The most smoothed profde of its variability is characteristic for the multistep r model IV, for wlfich r values change with D,t mo,lotonically. "]'he energy output rate UT for intense storms reveals a good correlation with both the energy input rate and energy injection function F,, as can be seen in Table 2. It is evident, that the best correlation model and corresponding v model criteria are interrelated. Actually, the UT(F,,) correlation for the main phase is the highest for the model I, for which the r set values are defined by the F,~ criterion. The UT(~) relation manifests the best correlation for the r model II for which

FOR

THE RELATIONSHIP OF THE ENERGY OUTPUT RATE RATE ~ AND INJECTION FUNCTION AVERAND THE WIIOLE STORM INTERVAL OF INTENSE MAGNETIC STORMS ARE CONSIDERED USING r MODELS I THROUGH IV (a = 17) BOTII TIIE ENERGY DURING THE MAIN

VERSUS AGE VALUES

Interval Main phase

~

Model

I

Y(x) \ UT(F)

storm

II

UT(F)

0,674.0.13

UT(Fm)

0,824.0.08

r=0.85

r= 0.70

13£

i -- ... I'.. *• :~...

~10[

~h.'.

•

n=163

~\ .'"

• . . i. r

x

: ~---

n=l~ l ,

.

lEO

I 75

""

, n=163 150

[i ~ 0

J

t 75

I

.'.'" n = 163 l , I 150 225

,

I, nT/h " "

.~.

/

--

0

ANALYZED:

FOR

--~ 190

.... ,

0

:

,

~'"

U.•: •,..:.

~=167

,"

75

I

,

150

--

SUCCESSIVE

HOUR

SHIFT

(BOTTOM

n=16:

l

'~ ", " 0

225

75

150

225

I E." I, .'rib

I ~I~" I, ,,'rlh

WITHOUT

SHIFT

~c 'I --. • . .:..~- ~ , ~

~380

"

g':.'::..'

225

Fezp(Fm) R E L A T I O N S H I P STORMS

.-

570

I r~.;'~ I, ,,T/h

MAGNETIC

"

~]--2" •

225

~ - 100 ~";$"

I!l~ .:v.

r'= 0.74

200

0

THE

.•

•

_= 65

3.

° • . -

300

13(

FIG.

/

[ F,,, 1, n'J'/h

:: . /

• ...

"'/

r= 0.6t

r= 0.60

195

INTENSE

~ .

75

' 150 225 I, nT/h

r=0.62

--

.. ; ' , . •,. °'~, °.1 • .~,:"

20C

F.

0.754.0.11

IV

30£

I

0.774-0.10

II

195

/5

IV

0.934-0.03 0.914.0.04 0.894-0.05 0.90-40.05

I

- 65

llI

0.714-0.12 0.814-0.08 0.784-0.10 0.744.0.11 0.944-0.03 0.804-0.09 0.824.0.08 0.854-0.07

UT(Fm)

interval

Frn,

INPUT PHASE

VALUES

(UPPER

DURING

PANELS)

THE

AND

PANELS).

The individual columns are related to the models I, II, IV.

WITH

MAIN

PHASE

AN

HOUR.

OF

17

AHEAD

Magnetospheric storm dynamics

585

the e criterion was used. It is directly attributed to the UDR(T,,) and Uzm(~) relationships for which the r model option plays and important role. The feature mentioned can be illustrated by means of the F~p(Fm) relationship considered for the r models I, II, IV and displayed in Fig. 3. The plots for the model III are not illustrated because of similarity with the model IV. The scatter of values for successive ) hours hours during the nlain phase of the storm set analyzed I0 ~0 30 40 50 60 (Table 1) is much greater for the model IV in com6-i parison with the model I. An hour ahead shift of the controlling parameter gives just the opposite pattern, as can be seen in Fig. 3. This is due to the improvement of the model IV criterion for the 1" option via a more adequate D,t index, which is not the case for the models I and II. The same is true for the F~F(e) relationship. The option of the ,- model, which defines the ) hours amount of/IDa and UT respectively, controlls indirectly 10 20 30 40 50 69 the relative importance of energy dissipation rate in the auroral ionosphere with respect to UvR. It seems that one of the proper and universal criteria of the *- model option is to keep an adequate ratio between UDa and UAs constituents of UT by means of an adequate option ff 9"/' /,,_ of r values. Fig. 4 illustrates the time profiles of the relative coil.~' > hours tribution of the UT constituents during the August 27August 27-29. 1978 magnetic storm 29, 1978 magnetic storm for the 7" models I, II, 1V. The ratio UDR/UAj is different for the models considF I G . 4 . T I M E P R O F I L E S OF THE UDR/UAJ Q U A N T I T Y . The difference for the standard AE index (a dotted llne) ered and changes in a broad range. While ULm domiand modified AE' index (a solid line) used is evident. (For nates UAj 8olely during the storm main phase for the 7" model I, the predominance being more striking for more details see the caption of Fig. 2). the standard AE index alternative, the relative impor•r= 0.55 ~r= 0.27 tance of the UAs quantity is considerably suppressed 2220 for the models II and IV. For these models the value of Uvn/UAs is preferably defined by the value of Uva, which is extremely high. The discrimination of the UAj contribution in the estimation of global energy flow rate from the magneto~pllere to the ionosphere is due, paztly to the fact <<" n= 163 that the AE index is not an accurate quantity to be 6o 18o ~.I0", W used for this purpose (Akasofu, 1989). The insufliencles inherent in the construction of the AE (12) index •r= O,fi5 ~ r = 0.08 mentioned above are most clearly illustrated when the 2220i " , ; dependence AE(*) is considered for standard AE and modified AE' indices. It is fairly evident from Fig. 5 uJ 1480 • •. that the energy input rate , is likely to fail to be a guide for the auroral electrojet current intensity which is quantified by A E index. ',~F Z " ~ n = 163 The plots displayed are obtained for successive hours 60 "l~O "180 during the main phase of intense magnetic storms ana~'-".10"o W lyzed. The scatter of A E values within a broad range F I G , 5 . T H E STANDARD AE INDEX (A S T R A I G H T F I T LINE is evident for the energy input rate e > 5 . 1011W which IS D O T T E D ) AND M O D I F I E D AE' INDEX (A S T n A I G H T F I T was earlier indicated to be critical in the AE(*) LINE IS SOLID) D E P E N D E N C E ON ENERGY I N P U T RATE *. relationship (Akasofu, 1980). It means that standard T H E VALUES FOrt S U C C E S S I V E H O U R S D U R I N G T H E MAIN PHASE O F 1 7 n q T E N S E M A G N E T I C S T O R M S (t~ = 1 6 3 ) A n E AE index appeazs to be a proper quantity only for weak C O N S I D E R E D W I T H O U T S H I F T ( U P P E R PANEL) AND WITH and moderatd storms, becoming unreliable for intense AN H O U r i AHEAD S H I F T ( B O T T O M P A N E L ) , storms (Akasofu, 1980; Sumaruk et al., 1990). This is •

10 ,

20 - ~,

30 .

•

Jl

!

.

40 ,

.

,

•

x

..............

.

50 .

,

60 ,

.

,

586

A. PRIGANCOVAand YA. I. FELDSTEIN

TABLE

3. AVERAGE UDH/'U-Aj RATIO VALUES FOrt THE STORM MAIN PHASE OF INDIVIDUAL INTENSE STORMS.

AE and modified AE I

Time decay r models I through IV are considered using standard

indices for calculation U--(~ and U'AJ quantities, respectively. Storm March '23-25, 1969

~ Model Ratio ~ \

I

UDn/UA3 "UDR/-O'~A)j

0.88 1.50

-UDR/-UAj -UDR/U'U'(A)

July 4-5, 1974

November 24-27, 1978

April 3-5, 1979

7.04

1.57

11.97

2.70

1.09

6.16 1.46 8.56

"UDR/'UAj

0.43

1.14

3.08

1.21

~R/~;~

046

1.23

330

129

UDR/'UAj

0.81

2.37

7.43

1.65

DRIteAj

0.89

2.59

8.13

1.81

,~o)

4. T H E INTEGRATED AMOUNT OF THE ~ C RATE

INPUT

1.89 3.21

2.77

OUTPUT

ENERGY

IV

1.04

TABLE

AND

11I

1.45

~-

UT

11

2.04

ENERGY INJECTION RATE UDR ~ TOTAL ENERGY

RATE ¢ CALCULATED INTENSE STORMS.

FOR

THE

MAIN

PHASE

OF

INDIVIDUAL

Time decay r models I through IV are considered.

Storm

Main phase ~ M o d e l integrated . ~, 'N~ - " - ~ . energy parameter, 10 ll kJ

March 23-25, 1969

July 4-6, 1974

November 24-27, 1978

April 3-5, 1979

I

I1

III

IV

fUDndt J UTdt fed| fUDndt fUTdt f~dt

171.07 364.61 532.22

365.04 558.58 532.22

1361.66 1555.20 532.22

306.72 500.26 532.22

105.55 212.54 619.06

207.50 311.62 619.06

640.37 744.48 619.06

152.35 256.46 619.06

f UDRdt f UTdt f edL f UDRdt f UTdt fedt

137.16 462.24 757.08

367.20 687.96 757.08

987.12 1307.88 757.08

387.72 708.48 757.08

183.46 409.97 985.14

536.80 763.31 985.14

1683.40 1909.91 985.14

374.40 600.91 985.14

even more convincing when e vahles axe an hour aheaxl w i t h respect to tile AE index as seen in the b o t t o m panel of Fig. 5. T h i s p o o r c o r r e l a t i o n becomes strikingly improved w h e n modified AE' index is used. T h e best fit regression line shows t h a t t h e modified AE' indices d u r i n g the m a i n p h a s e of an intense s t o r m can be p r e d i c t a b l e o n t h e basis of the a d v a n c e d energy i n p u t r a t e • values according to t h e linear relationship:

AE' = ( 9 . 2 0 : k 0 . 8 6 ) e ( - 1 ) + ( 7 4 6 + 3 4 ) ,

r = 0.654-0.05,

where e is in 1011W emd AE' in n T . For i n d i v i d u a l s t o r m s this r e l a t i o n s h i p is even closer, which is consist e n t w i t h results o b t a i n e d by S u m a r u k et al. (1990).

T h i s m e a n s t h a t d u r i n g the m a i n phase of i n t e n s e m a g n e t i c stornls, the energy i n p u t rate e is a p r o p e r governing q u a n t i t y for the energy d i s s i p a t i o n r a t e in the auroral ionosphere when modified AE' indices axe used.

T h e i n a d e q u a c y of AE indices u n d e r e x t r e m e l y dist u r b e d c o n d i t i o n s was confirmed by empirical estimations of the Joule h e a t p r o d u c t i o n ( B a n m j o h a n n a n d Kaznide, 1984). T h i s quantity, empirically assessed, is likely to c o n s t i t u t e the fairly considerable energy sink, a n d a p p e a r s occasionally to b e of equal or even greater i m p o r t a n c e t h a n the RC energy c o n s u m p t i o n ( B a u m j o h a t m a n d Kaxaide, 1984). Moreover, t h e Uj

Magnstospheric storm dynamics production together with the UA production represent important parameters in the energy budget of the magnetosphere-ionosphere-neutral atmosphere system according to empirical results (Baumjohann and Kamide, 1984; Spiro et al., 1982). This is consistent with our results obtained for the model I, when modified AE' index is used. In Table 3, the relative importance of Una and UAj constituents of UT is considered as averaged for the storm main phase, using UAj calculated on the AE I basis and It(°) WAJ calculated on the AE basis. According to the model I, the UAj production is not less important than the Uva quantity even during intense storms. On the other hand, the extreme UAj suppression, even for AE' indices exploited, is most remaxkable for the model III. Nevertheless, the extreme UnR superiority appears to be far from the realistic values. In Table 4 the integrated energy parameters fUDRdt, fUTdt and f~dt calculated for the storm main phase are illustrated for individual storms. The integrated energy injection rate and consequently the total energy output rate displays significant differences for the models considered. These is due to the r set values option in view of UDR "" 1/r and U~, ~ 1/r. Finally, if the fUTdt quantity is compared with the integrated energy input rate fedt the different efficiency of energy transfer is remarkable from storm to storm which ranges approximately between 50-90 %. Afterall, for individual storms, when various models are considered, the integrated energy output rate can be judged from the energy conservation point of view by comparing fUTdt and fedt quantities. The violation of this essential principle can be attributed to the r model option. This way of judgment confirms the model II to be most adequate. The r set values of models I and IV appear to be fairly acceptable in the sense of the energy conservation principle. The violation of energy conservation was noted for the constant time decay r parameter (Akasofu and Olmsted, 1987).As can be seen in Table 4, the variable step-like r, its values being small enough, can also lead to drastic violation of energy conservation. Actually, the integrated energy output rate remarkably enhances the integrated energy input rate for the model III. It appears to be due to the unrealistically chosen r set values. A range of r values is broad. The great flexibility of time decay parameter is associated with the particle lifetime which depends on the RC particle population dynamics (e.g., Akasofu, 1980), on origin of current carriers, on the processes of charge exchange, Coulomb collision and wave-particle interaction (Akasofu, 1989; Sumaruk et al., 1990). The energy input rate and RC injection rate axe at the background of these processes which take place at L = 3 - 5. The validity of r sets exploited has occasionally been a point of contention (Zwickl etal., 1987). It seems to be reasonable to con-

587

trol whether the r model adopted yidds the acceptable results in view of energy conservation. This criterion is likely to give the lowest limit for r parameter values. 5. C O N C L U S I O N Magnetospheric storm dynamics in terms of the energy output rate UT was considered for 72 magnetic storms within the 1967-1972 interval. The UT quantity was compared with the energy injection rate during the main/recovery phase and storm interval as a whole. The a~nalysis has succeeded in tracing how the RC time decay parameter option influences the value of the total energy output rate for the set of intense magnetic storms with DRm~z < - 1 6 0 nT. In the r models chosen, the criteria of the time decay dependence on the energy transfer rate e, RG energy injection function F~, and RC intensity variations (DR and D , ) were applied, the differences in r values for the storm main and recovery phases being taken into account in two of the models (I and IV) considered. Thus, the models tested axe likely to summ~,'ize the present status in the RC time decay option. On hourly time scale, the relative importance of the RC injection rate Ups and the energy dissipation rate in the auroral ionosphere UAj is assessed using both the standard AE indices and modified AE' indices. These were derived on the basis of the model injection function F,,, according to which the energy transfer into the magnetosphere is not restricted to reconnection processes only, but viscous interaction is being taken into account. The ratio UDR/Uaj calculated for models chosen reveals that the UA~ contribution is masked by the UvR value, which crucially depends on the r model option. Thereafter, the extreme supression of the UAj production by the UnR quantity is likely to be artificial due to the inadequate option of r values. Moreover, to identify the r parameter properly the criterion of energy conservation principle appears to be account for which is likely to give the lowest limit for r values. Such an approach prevents the integrated energy output rate to be higher than the intergated energy input rate. It was shown that during the storm main phase the energy input rate e is a proper governing quantity for the energy dissipation rate in the auroral ionosphere if modified AE' indices axe used. The limited efficiency of the energy transfer process is confirmed as well. It differs from storm to storm, being on average ~ 70%. The reconstruction of the RC energization on the basis of time-dependent pattern of the r parameter shows that the deeper insight is needed into the dynamics of plasma processes at L = 3 - 5 which comprise various mechanisms controlling the particle lifetime. Acknowledgments. The gratitude is expressed to the NSSDC through the WDC-A for R&S for interplanetary medium omnltape data, to b. Bitt6 for his thoroughness in computer processing of data, and to D. Pavllkovl. for the

technical preparing of the manuscript.

588

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