ISSN 0010�9525, Cosmic Research, 2013, Vol. 51, No. 1, pp. 46–53. © Pleiades Publishing, Ltd., 2013.Original Russian Text © R. Lukianova, A. Kozlovsky, 2013, published in Kosmicheskie Issledovaniya, 2013, Vol. 51, No. 1, pp. 53–61.4

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1. INTRODUCTION

Electrodynamic interaction between the solar wind(SW) energy and the Earth’s magnetosphere takesplace, in the main, in the boundary layers and themagnetosphere tail, which are conjugate in the geo�magnetic field lines with the high�latitude areas: theauroral oval, cusp, and the polar cap (PC). In the cir�cumterrestrial space, the polar cap boundary (PCB)can be considered as a boundary between geomagneticfield lines that are open to SW and closed onto theopposite hemisphere. Field lines going out of the polarcap are stretched into the magnetosphere tail and openfor penetration of SW plasma and the interplanetaryelectric field. It is a clear manifestation of the effects ofthe SW interaction with the magnetosphere, and ananalysis of the PCB dynamics enables one to trace thedevelopment of many magnetospheric processes.

In the Dungey cycle [1], during which the energy isinjected from the SW into the magnetosphere and ion�osphere, plasma convection is determined by recon�nection of magnetic field lines on the daytime magne�topause and in the magnetosphere tail. It has beenshown that, when day (night) reconnection domi�nates, as open magnetic flux increases (decreases), thepolar cap is expanded (compressed), and, accordingly,PCB is shifted to the equator (pole). The PC compres�sion–expansion also occurs in the substorm cycle [2–4]. The auroral oval and PCB are asymmetric about

the pole both along the noon–midnight meridian, andalong the dawn–dusk meridian. Midline of the auroraloval is approximately at 78° and 68° MLat, and theoval thickness is about 3° and 10° (at Кр = 3) on the dayand night sides, respectively [5]. This line, as well asPCB, is shifted to the equator with increasing geomag�netic activity [6]. The PCB shift along the dawn–duskmeridian is controlled by a sign of the IMF By, so thatin the northern hemisphere at By > 0 (By < 0), the polarcap as a whole is shifted to the dawn (dusk) side [7–9].In the southern hemisphere, the shift direction isopposite [10].

The PCB dynamics is complicated during geomag�netic storms. The main phase of a storm is usually ini�tiated by southern IMF of sufficiently large amplitude.According to an increase of the open magnetic flux inthe magnetosphere, the PCB is shifted to the equator.During the main phase a large amount of energy isaccumulated in the magnetosphere tail, and theoccurring dissipative processes are largely nonlinear[11]. Consequently, the PCB dynamics during thestorm can significantly differ from non�storm periods.A large number of images of the auroral oval made bythe IMAGE satellite and progress in the methods oftheir processing [12] allow one to perform in�depthanalysis the PCB evolution. In this paper, on the basisof the IMAGE measurements, the statistical depen�dences of PCB positions on the IMF parameters areobtained, and the PCB dynamics in different sectors

Dynamics of Polar Boundary of the Auroral Oval Derivedfrom the IMAGE Satellite Data

R. Lukianova1, 2 and A. Kozlovsky3

1 Arctic and Antarctic Research Institute, ul. Beringa 38, St. Petersburg, 199397 Russia2 Space Research Institute, Russian Academy of Sciences, Profsoyuznaya ul. 84/32, Moscow, 117997 Russia

3 Sodankyla@ Geophysical Observatory, University of Oulu, Finlande�mail: renata@aari.nw.ru, alexander.kozlovsky@oulu.fi

Received March 29, 2012

Abstract—Based on a new database on positions of the auroral oval boundaries including measurementsmade by the IMAGE satellite in 2000–2002 with correct determination of the glow boundaries, statistical esti�mations of the latitudinal position of the polar cap boundary (PCB) are obtained depending on the IMF Byand Bz, and the PCB evolution during a magnetic storm is analyzed. At zero IMF in the noon (midnight) sec�tor, PCB is located approximately at 80° (76°) CGMLat. The PCB displacement along the noon–midnightmeridian is controlled by the IMF Bz, and it is equal to 0.45° (0.15°) CGMLat when Bz changes by 1 nT inthe noon (midnight) sector. The PCB displacement along the dawn–dusk meridian depends on the IMF By,and it equals 0.1° CGMLat when By changes by 1 nT. Accordingly, the north polar cap as a whole is shifted tothe dawn (dusk) side at By > 0 (By <0). After northward turn of the IMF during the storm’s recovery phase onthe dayside, the PCB is shifted to the north practically without time delay. The night boundary requires 25 hor more in order to be shifted to the pole to a latitude corresponding to Bz > 0.

DOI: 10.1134/S0010952513010061

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DYNAMICS OF POLAR BOUNDARY OF THE AURORAL OVAL DERIVED 47

of local time is analyzed during two geomagneticstorms.

2. METHODS OF PCB DETERMINATION

There are several methods for determining PCB.The PCB identification using the spectra of precipitat�ing particles is considered as the most reliable method[13, 14]. Precipitation events are observed by theDMSP satellites placed in polar orbits at an altitude ofabout 800 km. However, these measurements are notglobal, since consecutive satellite passages are sepa�rated from each other by approximately 100�minintervals. Ground�based optical photometers allowone to monitor continuously PCB by a jump in theemission intensity at a wavelength of 630 nm, whichoccurs at the boundary of closed lines [15, 16]. Suchobservations are limited by the photometer location,and they are possible only at night under the cloudlesssky. Using the data of the SuperDARN coherent scat�ter radars, PCB can be identified by increasing spectralwidth of the reflected signal [17]. But interpretation ofthe measurement data on the spectral width is oftenambiguous. For example, it is shown in [18] that thespectral width increases with intensification of theionospheric electric field, on whose background theionospheric irregularities are developed, and it is notassociated with PCB. More precise PCB location canbe obtained from measurement data on the electrontemperature and by sharp changes in the electron den�sity in the Е and F ionospheric regions with the help ofincoherent scatter radars [19]. However, these mea�surements were performed only in the course of spe�cial experiments.

Optical measurements of auroral emissions madeby the IMAGE satellite [20], which was in the high�polar orbit from March 2000 to December 2005, allowone to observe the entire oval for a long time. In thiscase, the PCB position is identified with the polar edgeof auroral glow. As a result of the satellite operation, alarge number (> 1 million) images were obtained takenevery 2 min with a 10�second exposure time.

3. DATA SET

In order to interpret the obtained images, manyprocedures were suggested for estimating the intensityand determining the position of the glow boundaries,including visual estimation [21] and various methodsof brightness gradation [22–25]. A comparison of thePCB position derived from the data on precipitatingparticles with the position determined by the polaredge of auroral glow has shown that the optical PCBregularly are slightly more equatorial, which wasexplained by insufficient spatial resolution of opticalinstruments [4, 26]. At automated processing of a largenumber of images, interpretation of the double ovalwas also found to be technically complex problem.Meanwhile, about 30% of the images showed a double

oval on the night side, and during disturbed periods afraction of these images was as high as 50%.

To determine more correctly the oval boundariesan improved method was developed for estimating theglow intensity and searching for threshold values of theintensity. It is based on the use of a combination of sin�gle and double Gaussian distributions [12]. Themethod has been automated in order to process a largenumber of images and create a database which con�tains more than million values of the auroral ovalboundaries. A comparison of the obtained opticalboundaries with the data on precipitating particlesfrom the DMSP satellites showed that the resultsobtained by the two methods are now in a much betteragreement. Thus, the polar boundary of glow bright�ness can be used as the PCB indicator.

In the period from May 2000 to December 2002,the IMAGE has the most favorable orbit to observehigh latitudes of the northern hemisphere. Themethod of identifying the boundaries of the auroraloval described in [12] was applied to the imagesobtained in this period. As a result, a database was cre�ated with more than 2 million 2�min values of geomag�netic latitudes of the polar and equatorial oval boundariesfor each MLT hour. The largest amount of data belongs tothe sector 16–06 MLT (~150000 points per hour), andthe smallest amount is for the sector of 10–13 MLT(~20000 points per hour). The data of three IMAGEinstruments are available at the British Antarctic Sur�vey site http://www.antarctica.as.uk/. In this paper, weuse the measurements of Wideband Imaging Camera(WIC) operating in the far�UV range of 140–190 nmand fixing emission in the N2 Lyman–Hopfield bandwith the resolution of 256 × 256 pixels [20]. Initial valuesof the PCB latitude were averaged in mean hourly values,provided that no less than 50% of 2�min data per hour wereavailable. As a result, about 12000 points were obtained foreach hour of the night sector (21–03 MLT), about 10 000for the dawn (05–07 MLT) and dusk (17–19 MLT) sec�tors, and 4000 points for the day (10–14 MLT).

4. AN ESTIMATION OF PCB SHIFT DEPENDING ON THE IMF By AND Bz

A large number of processed images of the auroraloval allows us to get statistical characteristics of the lat�itude PCB position in different sectors of the localtime and to estimate the degree of the PCB shiftdepending on the IMF magnitude and direction. Thebasic characteristic, which can be used as a zero refer�ence level for a quantitative estimation of the polar capshift, is the PCB positions at IMF ≈ 0. To determinethe zero PCB position of the entire database the timeperiods were selected, when the total IMF vector BТ =

did not exceed a value of 1 nT, and for eachMLT hour the average PCB latitude was calculated.The PCB shift with increasing IMF intensity sepa�rately for Bz and By components was determined by the

2 2z yB B√ +

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LUKIANOVA, KOZLOVSKY4

regression relations between the corresponding com�ponent and the PCB latitude and then averaged for 3�hour sectors centered at 0, 3, …, 21 MLT. In this case,the periods of magnetic storms (Dst < –50 nT) wereexcluded, and from remaining ones only sufficientlylong (≥1 hour) periods of stable sign of the IMF com�ponents were considered, since no special analysis oftime of the possible delay of the PCB shift at changingIMF orientation was performed. These limitationsreduced the amount of data by approximately 20%.Figure 1 shows an example of the statistical correlationbetween the IMF Bz (By is not specified) and the PCBlatitude for November 2000, MLT = 5. The correla�tion between the parameters is approximated by a lin�ear function, and the correlation coefficient is R =0.43.

Figure 2 shows MLT profiles of the PCB latitudinalposition at zero IMF (Fig. 2a), as well as the degree ofthe PCB shift at changing IMF By (Fig. 2b) and Bz(Fig. 2c). Figure 2 (a) shows that in the noon sector thezero PCB is located approximately at80° of correctedgeomagnetic latitude (CGMLat). As one passes to thenight side, the PCB is gradually moved away from thepole and located at 76° CGMLat in the midnight sec�tor. The graph in Fig. 2 (b), whose every point is tan�gent of the angle of inclination of the line of linearapproximation of the statistical correlation betweenthe PCB latitude and the IMF By intensity, shows byhow many degrees PCB is shifted under the action ofBy at a given MLT hour. According to this graph, thedegree of the polar cap shift along the dawn–duskmeridian is about 0.1° per 1 nT of the IMF By. In thenoon and midnight sectors, there is practically noPCB shift. The graph in Fig. 2 (c) shows a similardependence, but for the IMF Bz, from which it is seenthat under the action of Bz the largest PCB shift occurson the dayside, where it is characterized by the ratio of

0.45° CGMLat per 1 nT of Bz. In the midnight sector,the value of shift is about 0.15° per 1 nT of Bz.

Thus, quantitative estimations presented in Fig. 2,allow us to determine approximately the PCB locationfor arbitrarily given combination of values of the IMFBz and By. For every MLT hour, the PCB position inFig. 2 (a) is a zero reference level, and the additionalshift is calculated by the data of Figs. 2 (b) and 2 (c).In this case, it is necessary to take into account thatunder the action of Bz > 0 (Bz < 0), PCB is shifted to the

90

80

70

6020100–10–20

R = 0.43

Bz, nТ

CG

ML

at,

deg

Fig. 1. Statistical correlation between the IMF Bz and thePCB latitude for November 2000 at 05:00 MLT (1613points in total) and its linear approximation.

0.6

0.4

0.2

181260

Bz, nT

∆C

GM

Lat

/∆B

z, d

eg/n

T

MLT

c

0.2

0.1

0

–0.2

∆C

GM

Lat

/∆B

y, d

eg/n

T

b

–0.1

80

CG

ML

at,

deg

а

75

Fig. 2. The PCB latitude at the IMF ВТ < 1 nT (a); thedegree of the PCB latitude shift at varying IMF By (b) andBz (c) for different MLT hours. Values of parameters for 3�hour sectors centered at 0, 3, …, 21 MLT are shown bypoints; root�mean�square errors of regression are alsoshown for them. Points are connected by a line of spline�interpolation.

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DYNAMICS OF POLAR BOUNDARY OF THE AURORAL OVAL DERIVED 49

pole (equator) and under the action of Bу > 0 (Bу < 0) tothe dawn (dusk) side.

5. EVOLUTION OF THE POLAR BOUNDARY AT NORTHWARD TURN OF IMF DURING

RECOVERY PHASE OF MAGNETIC STORMS

The above estimations of the PCB position weremade for non�storm periods. During strong geomag�netic storms caused by solar flares and arrival to theEarth of interplanetary clouds with a large amplitudeof the southern IMF, a large amount of energy is deliv�ered to the magnetosphere, and the area of the polarcap increases. In the tail part of the magnetic cloud,IMF is often directed northward, and interaction ofthe magnetosphere with this structure determines theonset of the storm recovery phase. Both theory andexperiment predict that when the IMF turns north�ward the polar cap becomes smaller, and PCB isquickly shifted to the pole. However, under storm con�ditions, the development of this process can have anumber of specific features, which have not been ade�quately studied. An analysis of the PCB positionsimultaneously in all MLT sectors, which can be car�ried out based on the IMAGE database, allows one totrace comprehensively the dynamics of the polar capduring magnetic storms.

Two magnetic storms on August 17–18 andNovember 24–25, 2001 were chosen to solve thisproblem. The choice was dictated by the fact that inmagnetic clouds, which were the source of storms,there was a clearly defined IMF turn to the north, fol�lowed by a long period of the stable northward IMF,during which a value of the By IMF component wassmall. Figure 3 (plots I–VI) shows the characteristicsof storms on August 17–18 and November 24–25,2001: IMF Bz, By, and Dst index. Although the IMFvariation has its own features, during both storms onecan see the sharp IMF turn to the north (at 22:00 UTon August 17, 2001 and at 15:00 UT on November 24,2001) and a long period of Bz > 0 during the stormrecovery phase. Figure 3 (plots VII–X) shows the variationin the latitudinal PCB position in the day (10–14 MLT),night (22–02 MLT), dawn (04–08 MLT) and dusk(16–20 MLT) sectors of local time. Pairs of oppositesectors (day/night and dawn/dusk) are combined inone and the same plot.

Figure 3 (VII–X) shows that, in the main stormphase, the PCB latitude varies very rapidly generallyfollowing the IMF variation. At the beginning andduring the main phase with increasing southward IMFup to Bz ≈ –20 nT (about 12:00 UT on August 17 andNovember 24, 2001), the PCB is sharply shifted to theequator approximately by 10°. This is clearly seen inall MLT sectors in the event on November 24, 2001. Inthe event on November 17, 2001, the PCB is signifi�cantly shifted to the south in the day, night, and sawnsectors, and in the dusk sector practically there is noshift. This can be stipulated by the dominant influence

of the IMF By during 12–24 UT, when By ≈ +20 nT. Inthis case, since the cap is generally shifted to the dawnside, the effects of Bz < 0 and By > 0 are mutually com�pensated in the dusk sector.

The variation of the PCB position on the day andnight sides (Fig. 3, VII–VIII) significantly differs atthe recovery phase, when IMF turns to the north, thedayside PCB is almost immediately shifted to the pole,the night PCB continues to be considerably moreequatorial than the latitude, which corresponds to thevalue Bz > 0 existing at this time. Such dynamics ofPCB is typical for recovery phases of both storms onAugust 17–18 and November 24–25, 2001. Figure 4shows the difference between observed PCB positionand the position calculated by the data of Fig. 2 forcorresponding values of IMF separately for the night(Figs. 4a and 4b) and day (Figs. 4c and 4d) sectors.Thus, for the storm on August 17–18, 2001 from 22:00UT on August 17 to 24:00 UT on August 18, the aver�age value Bz ≈ +8.4 nT. At this IMF an estimation ofthe PCB position gives 83.6° (the day sector) and 78°(the night sector) CGMLat. For the storm on Novem�ber 24–25, 2001 from 15:00 UT on November 24 to24:00 UT on November 25, the average value Bz ≈ +9.5 nT,and the corresponding estimations give the PCB posi�tion at 84.1° (the day sector) and 78.6° (the night sec�tor) CGMLat. In Fig. 4 for better visualization thetwo�day time interval of each storm is divided in twoparts: the period before the beginning of the recoveryphase according to Dst (open circles) and the period ofstable northward IMF during the recovery phase(black points). It can be seen in Fig. 4 (a and b) that onthe night side after IMF turn to the north (22:00 UTon August 17 and 17:00 UT on November 24) PCB isobserved significantly more equatorial than the posi�tion, which is given by estimations for the correspond�ing values Bz > 0 based on statistics for beyond thestorm periods. The difference can reach 10° andremain sufficiently large (~4° for storms under consid�eration) during 20 hours or more. The linear approxi�mation of the PCB shift rate to the pole at the recoveryphase (inclined lines in Figs. 4a and 4b) gives a value of0.3°/h. In the day sector, as is shown in Fig. 4 (c andd), the difference of latitudes is small, alternating, andrarely exceeds 3°. This suggests that, in the noon sec�tor, PCB quickly takes a position corresponding to thestrength of the northward IMF.

The PCB shift along the dawn–dusk meridian bothin beyond the storm periods and during storms ismainly controlled by the IMF By. This can be seen inFig. 5, where the differences between the PCB posi�tions in dawn and dusk sectors are presented togetherwith variation of the IMF By. In the main phase of thestorm on August 17, 2001 in the interval 12–24 UT, Byreaches +20 nT and more. Figure 5 (a) shows that atthis time the difference of dawn–dusk latitudes forPCB is on the average 4.5°, and in some hours reachesto 6–7°. In this case, the difference is negative, whichmeans a shift of the polar cap as a whole to the sawn

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LUKIANOVA, KOZLOVSKY4

00 00120012

Universal time, hours

Х)

–75

00 00120012–10

–80

–85

–70

–65

–90

IХ)

CG

ML

at,

deg

75

60

80

85

70

65

90

VII)

CG

ML

at,

deg

0

00 00120012

–100

–200 V)

Dst,

nT

20

0

–20III)

By,

nT

–40

40

20

0

–20I)

Bz,

nT

–40

40 August 17–18, 2001

II)November 24–25, 2001

IV)

VI)

00 00120012

VIII)

Fig. 3. Variation of the IMF By (I–II), Bz (II–IV), Dst index (V–VI), and time evolution of the PCB latitudinal position in thenoon and midnight sectors (VII–VIII) and in the dawn and night sectors (IX–X) of MLT. Mean hourly values of the PCB latitudein the midnight and dawn sectors, and in the noon and dusk sectors are designated as lines with full and open circles, respectively.

side by approximately 2°. During the main phase ofthe storm on November 24–25, the IMF By changessign three times: By ≈ +15 nT at 7–8 UT, –20 nT at10–12 UT, and +10 nT at 13–15 UT. Generally, fol�lowing variations of By the sign of the difference ofdawn–dusk PCB latitudes also varies, as is shown inFig. 5 (b). At By > 0, the polar cap is shifted to the dawn

side by 1.5–2°, then at By < 0 it moves to the dusk sideby 3–3.5°, and then again to the dawn side at By > 0.

6. DISCUSSION OF RESULTS

The PCB dynamics in the day and night sectors oflocal time is principally different. In the recovery

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DYNAMICS OF POLAR BOUNDARY OF THE AURORAL OVAL DERIVED 51

0

–5

00 00120012

c

0

–5

00 00120012

d

–10

10–14MLT

Universal time, hours

0

–5

b

–10

22–02MLT

November 24–25, 2001

0

–5

аAugust 17–18, 2001

∆C

GM

Lat

, d

eg

Fig. 4. Evolution of the difference Δ between the observed PCB latitude and its statistical estimation in the midnight (a, b) andnoon (c, d) MLT sectors.

5

0

–5

0012001200

а

0012001200

b

20

0

–20

Universal time, hours

CG

ML

at,

deg

ММ

П В

y, n

T

Fig. 5. Evolution of the difference between the PCB latitude on the dawn and dusk sides (full circles) and the variation of the IMFBy (vertical lines) for the storms on August 17–18 (a) and November 24–25, 2001) (b).

phase of the storm when IMF turns to the north andduring following long period of the northward IMF,the day PCB is practically immediately shifted to thepole, while the night PCB for many hours continues tobe located much more equatorial than the position,where it would have to be at the corresponding valueBz > 0. Fast, within 10–15 minutes, response of the

auroral structures on the dayside to the IMF variationwas observed when studying auroral arcs with the helpof radars [27]. At the same time, on the dusk side theevolution of the auroral arcs was slower [28]. The PCBposition on the night side during the storm on August12–13, 2000 was investigated in [29], where theboundary was determined using the DMSP satellite

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LUKIANOVA, KOZLOVSKY4

data. It was demonstrated that after a turn of the IMFto the north the shift process of the night PCB by 5° tothe pole continued for more than 12 hours. However,in the recovery phase of this storm in contrast to twostorms considered in this paper, a value of IMF Ву wassufficiently large. Because of this, additional energycould be delivered into the magnetosphere [30].

The size of the polar cap can remain large for a longtime at the northward IMF. On the dayside, the PCBdynamics is determined by the direct SW interactionwith the magnetosphere during the reconnection pro�cess at the magnetopause, which practically stopswhen IMF turns to the north. The night PCB is pro�jected into sufficiently inertial plasma sheet in the tail.The dynamics of the night boundary is affected notonly by the current strength of IMF, but by the state ofthe magnetosphere in the previous period of the mainphase of a storm, by the energy accumulated in thetail, and by the reconnection continued there. Estima�tions of the energy accumulated in the tail and thenreleased were derived using the data on dynamics ofthe polar cap boundaries with the help of the methodof magnetogram inversion [31, 32]. These estimationsshowed that the energy accumulated in the tail duringthe main phase of the storm is sufficient to provide forthe major part of expenditure in the recovery phase.

The PCB shift along the dawn–dusk meridian ismainly determined by a sign and magnitude of theIMF By. An estimation of the PCB shift according tothe model developed for beyond the storm periods(Fig. 2b) gives a value of about 0.1° per 1 nT of By vari�ation. At the same time, parameters of the current sys�tem of the magnetosphere and ionosphere depend notonly on IMF, but also on parameters of the plasmasheet (distribution of the magnetic field and plasmadensity gradient). In a detailed comparison of Figs. 2and 5, it can be seen that actually the shift of the polarcap to the dawn or dusk sides are not fully controlledby alternating values of the IMF By. In the main phaseof the storms (at 12–22 UT on August 17 and at 06–18 UT on November 24), the By influence on the dif�ference of the PCB latitudes on the dawn and dusksides is characterized by values of 0.27° and 0.43° per1 nT of the By variation, which is close to the modelestimations, but slightly exceeds them. A similar rela�tion averaged over the time of recovery phases ofstorms, when By value becomes close to zero (see Fig. 3)gives 2.1° and 1.76° per 1 nT of By, respectively, whichis much higher than the model estimations. In thiscase, the north–south asymmetry of the plasma sheetrelative to the neutral sheet can be an additional factorinfluencing the difference of the PCB latitudes on thedawn and dusk sides [33].

CONCLUSIONS

The statistical estimations of the latitudinal posi�tion of the polar cap boundary (PCB) are madedepending on the IMF By and Bz. At zero IMF in the

noon (midnight) sector, PCB is located at approxi�mately 80° (76°) CGMLat. Under the action of Bz onthe dayside, the largest PCB shift occurs, which ischaracterized by a value of 0.45° CGMLat per 1 nT ofBz. In the midnight sector, the shift is about 0.15° per1 nT of Bz. Under the action of By > 0 (By < 0), thenorthern polar cap is shifted as a whole to the dawn(dusk) side. The shift along the dawn–dusk meridianis characterized by a values of 0.1° CGMLat per 1 nTof By.

It has been shown that when IMF turns to thenorth at the recovery phase of two magnetic storms onthe dayside, PCB is shifted to the pole practicallywithout time delay. The night boundary needs morethan 25 hours to be shifted to the pole at the latitudecorresponding to a value of the IMF Bz > 0. The PCBshift along the dawn–dusk meridian is controlled,mainly, by the IMF By and occurs practically simulta�neously with changes of the By sign.

ACKNOWLEDGMENTS

This work was supported by the Academy of Finland(grant no. 260478). The authors would like to thank thegroup of researchers from the British Antarctic Survey,which created the database of positions of the auroral ovalboundaries by the IMAGE satellite measurements andmade it available in http://www.antarctica.ac.uk/bas_research/our_research/az/magnetic_reconnection/auroral_boundary_data.html. The data on IMF and Dstindex are obtained from the Goddard Center website(http://omniweb.gsfc.nasa.gov).

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SPELL: 1. Feldstein, 2. Sotirelis, 3. Lorentzen, 4. Lukianova