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Advances in Space Research 39 (2007) 1860–1866

EUV coronal pattern of complexes of solar activity

Elena E. Benevolenskaya

W.W. Hansen Experimental Physics Laboratory, Stanford University, CA, USA

Pulkovo Astronomical Observatory, St. Petersburg, 196140, Russia

Received 21 October 2006; received in revised form 13 April 2007; accepted 3 May 2007

Abstract

Studying of the coronal plasma associated with long-lived complexes of the solar activity is important for understanding a relation-ship between the magnetic activity and the solar corona changing during the solar cycle.

In the present paper, two long-lived complexes of the solar activity at the beginning of the current solar cycle 23 are investigated byusing the Extreme-Ultraviolet data (EUV) from SOHO/EIT. For this purpose the EIT limb synoptic maps during the CR1916–CR1919(11 November 1996–1 March 1997) are obtained.

The coronal temperature structures derived from the three lines 171A (Fe IX,X), 195A (Fe XII)and 284A (Fe XV) are investigated byapplying an algorithm developed by Zhang et al. [Zhang, J., White, S.M., Kundu, M.R. ApJ 527, 977, 1999]. Standard EIT software areused for the temperature estimation from the ratio of two lines of Fe IX,X and Fe XII.

The method of the rotational tomography with a correction for an inclination of the Earth’s orbit (B-angle) to the helioequator isapplied to obtain the three-dimensional (3-D) coronal structure of the complex of the solar activity. The results reveal difference in tem-perature structures related to multi-poles magnetic structures of the complex of solar activity and to the typical, the bipolar activitycomplex.� 2007 COSPAR. Published by Elsevier Ltd. All rights reserved.

Keywords: Solar EUV corona; Complexes of solar activity

1. Introduction

A complex of the solar activity persists at all levels of thesolar atmosphere and consists of sunspots and surroundingplages in photosphere and chromosphere with arcades ofloops visible in the corona in Extreme Ultraviolet Emissionand Soft X-ray. These loops may be tracers of lines of themagnetic field connected magnetic areas with oppositepolarities. Usually, they include two groups of sunspotswith a strong magnetic field (2000–4000 G), so-called, thepreceding (the leading) and the following parts. Sometimes,the following part is represented by plages.

The method of rotational tomography is successfullyused for the reconstruction of the 3-D structure of thesolar corona by many investigators (e.g. Aschwanden

0273-1177/$30 � 2007 COSPAR. Published by Elsevier Ltd. All rights reserv

doi:10.1016/j.asr.2007.05.006

E-mail address: elena@quake.stanford.edu

et al., 2000; Aschwanden, 2005; Frazin and Kamalabadi,2005). In the present paper, the method of the rotationaltomography is applied to the reconstruction of the 3-Dcoronal temperature pattern of long-lived activity com-plexes. For this purpose we have used synoptic observa-tions of the solar corona in EUV from the ExtremeUltraviolet Imaging Telescope (EIT) on SOHO (Delabou-diniere et al., 1995). The EIT images can provideestimates of coronal temperatures from 0.6 to 2.5 MK(Moses et al., 1997). The EIT estimates of the coronaltemperature are based on the ratio of intensities in differ-ent Fe lines. The temperature derived from Fe XII andFe IX,X lines identifies the coronal plasma heated upto 1.7 MK. This ‘standard’ temperature is calculatedusing the standard EIT software.

The estimated temperature derived from the three lines,Fe IX,X (171 A) and Fe XII (195 A) and Fe XV (284 A),produces a two-component solution: a low-temperature

ed.

E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866 1861

part (‘cool’ component) from 0.8 to 1.6 MK, and ahigh-temperature part (‘hot’ component) from 1.6 to2.6 MK (Zhang et al., 1999). The ‘averaged’ temperatureis represented by Tsum = (Tl Æ deml + Th Æ demh)/(deml +demh), where Tl and Th are the low- and the high-temper-ature, and corresponding differential emission measures aredefined as deml and demh.

Two long-lived complexes of the solar activity in lon-gitudinal zones of 150�–200� (A) and 220�–300� (B) inCarrington rotations from 1916 to 1919 (11 November1996–1 March 1997) at the beginning of the solar cycle23 are considered. They are depicted as red-blue areasin magnetic synoptic maps of the Wilcox Solar Observa-

90 180 270 360

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EIT Temp sum

EIT Temp Standard

WSO

Longitude

A B

Fig. 1. Upper panels: WSO low-resolution synoptic magnetic maps.Positive magnetic and negative polarity is drawn by red-blue in the rangeof [�50 50] Gauss. Middle panels: EIT ‘standard’ temperature maps fromthe lines of Fe IX,X and Fe XII. Bottom panels: EIT ‘averaged’temperature maps derived from the three lines Fe IX,X and Fe XII and FeXV from CR1916 to CR1919 (11 November 1996–1 March 1997). Thehottest areas are bright.

tory (WSO) (Fig. 1, upper panels). The correspondingcoronal temperature maps reveal these regions asextended bright areas (Fig. 1, middle and bottompanels).

The middle and bottom panels display two sets of thetemperature synoptic maps. Both sets detect the coronalplasma heated up to 1.7 and 2.6 MK, correspondingly.The comparison between the WSO magnetic and coronaltemperature synoptic maps shows the relationship betweenthe magnetic activity and coronal heating. Each magneticcomplex is surrounded by the areas of hot plasma in thecorona.

Using the EUV data and the method of the rota-tional tomography, it is possible to reconstruct coronalstructure above the complex of the solar activity in theinner corona up to the hight of about 1.3 solar radius(Rx).

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Altitude in solar radius

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tion

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gle

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tion

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gle

East limb West limbEIT 171A (FeIX,X)

Temperature

11.11.2

11.11.2

Fig. 2. Examples of limb maps for EUV emission of Fe IX,X and‘standard’ temperature maps obtained from the Fe IX,X and Fe XII lines.

1 1.05 1.1 1.15 1.2 1.250

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Altitude in solar radius

Fig. 3. Plots of intensity (left panels) and temperature (right panels) for the complex activity ‘B’ in CR1916, CR1917, CR1918 and CR1919 on the Westlimb. EUV emissions in 171A, 195A and 284A lines are marked by solid, dash and dash-and-dot lines, correspondingly. ‘Standard’ and ‘averaged’temperature is shown by dash and solid lines.

1862 E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866

1 1.05 1.1 1.15 1.2 1.25

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Altitude in solar radius

Fig. 4. Plots of intensity (left panels) and temperature (right panels) for the complex activity ‘A’ in CR1916, CR1917, CR1918 and CR1919 on the Eastlimb. EUV emissions in 171A, 195A and 284A lines are marked by solid, dash and dash-and-dot lines, correspondingly. ‘Standard’ and ‘averaged’temperature is shown by dash and solid lines.

E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866 1863

1864 E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866

2. Limb synoptic structure

Examples of the EIT limb maps as a function of sine ofthe position angle (P) (from the south to the north) and thealtitude in the solar radius (Rx) are represented in Fig. 2(upper panels). These maps corresponded the corona visi-ble on the East and the West limb 27 November 1996,when the longitude of the central meridian (Lc) was is161� in CR1916. The West limb map corresponds to thelongitude L = Lc + 90 at the position angle ‘P’ equals zero,the longitude of the East limb maps is L = Lc � 90 atP = 0.

The resolution of the map is 1� of the position angleand 0.01Rx of the altitude. Examples of the standardtemperature maps on the East and the West limb areshown in Fig. 2 (bottom panels). Temperature limb mapsmanifest the extended areas of hot plasma above thecomplex activity in the inner corona, which not directlycoincide with EUV maps. The EUV emission of the FeIX,X line displays the bright regions closely to the solarsurface.

The dependencies of the EUV emission and temperaturewith heights in CR1916–CR1919 are represented in Figs. 3and 4. Plots in Fig. 3 show distributions related to theactivity complex ‘B’, when it reaches the West limb (atthe longitude of the central meridian is about 160� and atthe latitude is about �30�). The EUV emissions in all threelines show maxima at heights between 1.01 and 1.05Rx

and rapidly decrease with an altitude for both complexesof the solar activity. The ‘standard’ temperature varies inthe range of 1.1–1.30 MK and shows a distribution of thecooler plasma compared with the ‘averaged’ temperature.The last temperature manifests the hotter plasma above

z zI

Y

Y I

x(x )I

E

B_angle

Fig. 5. A picture of the temperature synoptic map on the We

the extended and complicated complex of the solar activity‘B’ during the its development from CR1916 to CR1919. InCR1916 the temperature changes with heights in the innercorona from 1.45 to 2.1 MK and gradually decreases inCR1919 to values of about 1.4–1.75 MK. The plots ofthe EUV emission and temperature for the complex ofthe solar activity ‘A’, when it is seen on the East limb(at the longitude of the central meridian is about 260�and at the latitude is about �30�) are shown in Fig. 4.

The compact or the ‘typical’ activity complex ‘A’ mani-fests a small increasing of the ‘averaged’ temperature onthe East limb from the range of 1.25–1.5 MK in CR1916and to about of 1.3–1.6 MK in CR1919.

3. EUV limb maps and rotational tomography

Because of the inclination of Earth’s orbit, the positionangle coincides with the Carrington latitude if the B-angleequals to zero. The inclination of the Earth’s orbit(B-angle) to the helioequator is changing within the rangeof (±7.25�) with time during the year. If the B-angle is apositive (negative) the North (South) pole of the Sun isobserved. During the CR1916, the B-angle changed from3.15� to �0.22�.

Fig. 5 illustrates a position of the West limb map for the‘standard’ temperature compared to the Carrington coor-dinate system. Coordinates XI, YI and ZI correspond tothe Carrington coordinate system, coordinates of the limbmap is X, Y and Z. To obtain the correct Carrington lati-tude and longitude, we take into account that the positionof the solar limb depends on the B-angle. Applying theinterpolation to the sequence of the limb maps, the limb

CR1916

N

S

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st limb in CR1916 in the rectangular coordinate system.

EIT Temp Sum West Limb CR1916

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ude

100 150 200 250 300-40-20

02040

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ude

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-40-20

02040

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1

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2A B

Fig. 6. Limb synoptic maps at height of 1.05Rx (a) and at height of1.15Rx (b) for ‘averaged’ temperature from 1 to 2 MK.

Fig. 8. 3-D pattern of the coronal plasma in temperature for complexactivity within longitudinal zones of 150�–200� in CR1917.

E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866 1865

synoptic maps as a function of the Carrington latitude andlongitude are obtained at the different altitude.

Temperature synoptic limb maps at heights of 1.05 and1.15Rx are represented in Fig. 6. The synoptic maps showthat the area of hot plasma above the activity complex ‘B’strongly increases with the height. The difference in theheating plasma is probably related to topology of thesecomplexes. The activity complex ‘B’ within the longitudesof 220�–300� consists of several activity regions and dis-plays more complicated magnetic pattern compared withthe activity complex ‘A’.

Fig. 9. 3-D pattern of the coronal plasma in temperature for complex

4. 3-D structure of the complexes of solar activity

For investigation of the structure of coronal plasmasurrounding of the activity complexes the 3-D box of45 · 45 · 30 pixels (latitude, longitude, altitude) above

Fig. 7. 3-D pattern of the coronal plasma in temperature for complexactivity within longitudinal zones of 150�–200� in CR1916.

activity within longitudinal zones of 150�–200� in CR1918.

the solar photosphere are considered. The temperaturedistributions as a function of latitude, longitude and alti-tude for CR1916, CR1917 and CR1918 are presented inFigs. 7–9. During CR1916, when the activity complex ‘A’located within longitudes of 150�–200� reaches the Westlimb, we clearly see a pronounced connectivity (I)between magnetic region in South hemisphere near theequator and a small region about �20�. Also, the 3-Dtemperature pattern reveals a part of the hot streamer(II) extended with high (Fig. 7). During the CR1917the topology of the activity complexes is changing, andwe observe hot plasma cloud above this activity complexwith maxima of the temperature at the altitude about of1.15Rx (Fig. 8). During the following Carrington rota-tion, when the activity complex ‘A’ appears again onEast limb, the temperature is decreased and the plasmacloud is extended in space.

1866 E.E. Benevolenskaya / Advances in Space Research 39 (2007) 1860–1866

5. Conclusions

The method of rotational tomography (with B-angle cor-rection) is applied to reconstruction of the 3-D temperaturestructure of complexes of the solar activity using SOHO/EIT data. The hottest coronal plasma is closely related tothe complicated long-living complexes of activity. Thereconstructed temperature patterns reveal connectivityamong the complexes of solar activity and show the dynam-ics (from the hot loops and hot streamers to the hot plasmaclouds) associated with long-living complexes of solar activ-ity in the inner corona. The detailed coronal patterns of thecomplexes of the solar activity require the time series of theEUV images with better resolution in space and time.

This method can provide a good opportunity to investi-gate the coronal plasma structures associated with com-plexes of the solar activity during the future SDO mission.

References

Aschwanden, M.J., Alexander, D., Hurlburt, N., Newmark, J.S.,Neupert, W.M., Klimchuk, J.A., Gary, G.A. Three-dimensionalstereoscopic analysis of solar active region loops.II SOHO/EITobservations at temperatures 1.5-2.5 MK. ApJ 531, 1129,2000.

Aschwanden, M.J. 2D reature recongnition and 3D reconstrustion insolr EUV images, at temperatures 1.5-2.5 MK. Solar Phys. 228,339, 2005.

Delaboudiniere, J.-P., Artzner, G.E., Brunaud, J., et al. EIT: Extreme-ultraviolet imaging telescope for the SOHO mission. Solar Phys. 162,291, 1995.

Frazin, R.A., Kamalabadi, F. Rotational tomography for 3D reconstruc-tion of the white-light and EUV corona in the post-SOHO era. SolarPhys. 228, 219, 2005.

Moses, D., Clette, F., Delaboudiniere, J.-P., et al. EIT observations of theextrem ultraviolet Sun. Solar Phys. 175, 571, 1997.

Zhang, J., White, S.M., Kundu, M.R. Two-temperature coronal modelsfrom SOHO/EIT observations. ApJ 527, 977, 1999.