The analysis of high-resolution spectra of the Fe I (522.5 nm, 557.6 nm) and Ca II K (393.3 nm) lines in the solar photosphere and chromosphere is presented. A dynamic coupling of the photosphere and chromosphere was

determined from the ratios of both the photospheric and chromospheric line characteristics. All results are discussed for quiet and plage regions. It is found that

inthe plage regionthe meanv alues of K1, K2, K3 intensities inCa II K are increased 2, 5 and 6 times, respectively, as compared to the quiet region. The mean values of Fe I line core intensities increased in plage only 1.32 and 1.64 times for the magnetic non-sensitive and magnetic sensitive line, respectively. The ranges of Fe I core intensity values are larger for the magnetic sensitive line than for the magnetic non-sensitive line

Brcheckceková, K.

Hanslmeier, A.

Kucheckcera, A.

Rybák, J.

Wöhl, H.

English

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IL NUOVO CIMENTO Vol. 25 C, N. 5-6 Settembre-Dicembre 2002Dynamics of the solar photosphere and chromosphere derivedfrom high-resolution Fe I and Ca II K spectra(∗)K. Brcˇekova´(1), A. Hanslmeier(2), A. Kucˇera(1), J. Ryba´k(1) and H. Wo¨hl(3)(1) Astronomical Institute of the Slovak Academy of Sciences - 05960 Tatranska´ LomnicaSlovakia(2) Institut fu¨r Geophysik, Astrophysik und Meteorologie - Universita¨tsplatz 58010 Graz, Austria(3) Kiepenheuer-Institut fu¨r Sonnenphysik - Scho¨neckstr. 6, 79104 Freiburg, Germany(ricevuto il 10 Giugno 2002; approvato il 24 Settembre 2002)Summary. — The analysis of high-resolution spectra of the Fe I (522.5 nm,557.6 nm) and Ca II K (393.3 nm) lines in the solar photosphere and chromo-sphere is presented. A dynamic coupling of the photosphere and chromosphere wasdetermined from the ratios of both the photospheric and chromospheric line char-acteristics. All results are discussed for quiet and plage regions. It is found thatin the plage region the mean values of K1, K2, K3 intensities in Ca II K are in-creased 2, 5 and 6 times, respectively, as compared to the quiet region. The meanvalues of Fe I line core intensities increased in plage only 1.32 and 1.64 times for themagnetic non-sensitive and magnetic sensitive line, respectively. The ranges of Fe Icore intensity values are larger for the magnetic sensitive line than for the magneticnon-sensitive line.PACS 95.75.Fg – Spectroscopy and spectrophotometry.PACS 01.30.Cc – Conference proceedings.1. – IntroductionSolar spectra with high spatial and spectral resolution are a good tool to diagnosethe physical conditions in the solar atmosphere. To achieve this aim, it is importantto choose suitable spectral lines which are formed at appropriate heights in the solaratmosphere. We selected two photosperic Fe I lines—557.6 nm and 522.5 nm, the formeris pure dynamic, the latter is magnetic sensitive. To investigate the connection betweendifferent layers of the solar photosphere in different levels of activity, we included the(∗) Paper presented at the International Meeting on THEMIS and the New Frontiers of SolarAtmosphere Dynamics, Rome, Italy, March 19-21, 2001.c© Societa` Italiana di Fisica 565566 K. BRCˇEKOVA´, ETC.Table I. – The parameters of spectral lines.line Wavelength (nm) Height of line core formation (km) Lande´ factor geffFe I 522.55 ∼ 370 2.5Fe I 557.61 ∼ 370 0.0Ca II K 393.36 ∼ 1500 1.17Ca II K line. This line is widely used as a probe of the solar chromosphere dynamics dueto its core variability.2. – Observations and data reductionThe Vacuum Tower Telescope (Observato´rio del Teide, Tenerife) was used to obtainthe high-resolution spectra analysed in this work. The spectra were taken on June 1,1993 in regions with different levels of solar activity. The spectra of three spectral regionswere taken simultaneously at each position on the solar disc. The main parameters ofthe spectral lines used are listed in table I. The exposure time was 0.2 s for Fe I linesand 2 s for Ca II K line, respectively. The spectra were taken with 1024×1024 pixelsCCD cameras with a binning of 2. The final reduced spectra are 512×512 pixels withthe spatial resolution 0.17′′ along the slit and the spectral resolution 3.5 × 10−4 nm perpixel for Fe I lines and 2.6×10−4 nm per pixel for Ca II K line. The spectrograph slit was150 µm wide and it was adjusted to be parallel with the meridian. The characteristicsof the used spectra are listed in table II. The data were reduced using IDL software:the dark current subtraction was applied and a special procedure was applied to removethe flat field [1]. To compare images taken at different wavelengths, it was necessary toeliminate the influence of the atmospheric refraction. With regard to the fact that theslit was parallel to the meridian it was done by shifting images along the slit relative toeach other. The shift was assigned as a position of the maximum correlation coefficientsbetween the intensity fluctuations along the slit in the centers of Fe I lines and in theCa II K line wing. After this basic reduction the FFT noise depression, elimination of thecontinuum trend and calibration of the spectra to the real atlas continuum were done.3. – Spectral characteristicsWe used Doppler velocities (vd) and intensities in the centers of Fe I lines (I0), theintegrated intensity in the Ca II K line (a 1 A˚ interval with midpoint in the line center)and intensities at the K1, K2 and K3 positions in the Ca II K line, where the followingrelations were applied: I(K1) = [I(K1r) + I(K1v)]/2 and I(K2) = [I(K2r) + I(K2v)]/2.In the Ca II K spectrum of the quiet region genuine quiet scans were selected applyingTable II. – Characteristics of the spectra used.Number Time (UT) Disc location Level of activity1 08:01:01 µ ∼ 1 quiet2 08:28:31 0.97 > µ > 0.77 plageDYNAMICS OF THE SOLAR PHOTOSPHERE AND CHROMOSPHERE ETC. 567Fig. 1. – Mean scans (from selected scans only) of all investigated lines for both levels of activity.Solid lines stand for quiet, dash-dotted lines for plage, respectively.the condition Imax < 0.07IC , where Imax is the maximum intensity in particular scans.In [2] was found that enhanced chromospheric Ca II K emission can be produced bywave motion driven by the photospheric pistons. Using our condition we selected allscans which were not influenced by pistons at the moment of exposure. As “plageous”we understand the Ca II K scans with Imax > 0.25IC . Only the Ca II K spectral scansmeeting these constraints were used in our investigations together with correspondingscans from the Fe I lines spectra (quiet region—64 scans, plage—202 scans). Figure 1shows averaged spectral profiles (mean scans) of all three spectral lines.4. – Results and discussionThe properties of the photosphere were derived from the ratios of Fe I line character-istics. It is obvious that the correlations between intensities and velocities are similar forboth the Fe I lines (fig. 2). Due to the presence of magnetic fields the amplitudes of theintensity variations of magnetic sensitive Fe I 522.5 nm line are larger in plage regions(indicated by diamonds in fig. 2). Maybe the different values of the magnetic field occurthrough the active region and this caused the larger intensity dispersion. In the quietphotosphere the intensity I0 in Fe I is of about 0.25 IC for both lines, the value beingthe same for the whole range of velocities. This is not consistent with findings of [3]568 K. BRCˇEKOVA´, ETC.[ ]Fig. 2. – The dependences of the intensities on the velocities in the centers of Fe I lines for quiet(+) and plage (). Up-flows have negative velocities.(see fig. 3 in their work) where the correlation of the intensity I0 of Fe I 557.6 nm withthe velocity vd of Fe I 557.6 nm is evident. The lack of this feature in our analysis isprobably due to the fact that we have analysed the granular and intergranular patternstogether, while [3] distinguished between these two structures. More we selected onlythose scans which are related only to the moments of the “really quiet” atmosphere notinfluenced by pistons. In the quiet photosphere the positive (down-flow) velocities areslightly prevailing. In the photosphere under the plage we can see a shift of the coreintensities to higher values. The intensities I0 never fall below a fixed limit 0.27IC , i.e.the photosphere under the plage is heated to a higher temperature when compared tothe quiet region.The velocities in the photosphere under the plage are found to lie within a largerinterval than is the case for a quiet region. This interval exhibits an increase whenone goes to the negative velocities. Greater negative velocities tend to have smallerdispersion in the intensity values. The largest range of intensities is seen in scans featuringthe maximum positive velocities. This trend is more conspicuous in non-magnetic Fe I557.6 nm line, but it can be traced in Fe I 522.5 nm as well. Thus we conclude that thisFig. 3. – The dependences of the velocities in the centers of Fe I lines.DYNAMICS OF THE SOLAR PHOTOSPHERE AND CHROMOSPHERE ETC. 569Fig. 4. – The ratios of the intensities in Ca II K line against the Fe I line core intensities.trend has its probable origin in the dynamic properties of the atmosphere and it mapsthe different conditions of up-flowing and down-flowing plasma in the granulation.Figure 3 shows the ratios of the velocities in both photospheric lines under the quietand plageous atmosphere separately. The dependence is the same in both levels ofactivity. The range of values in the quiet region is slightly different from [3]. Their rangeof velocities in the positive values (up to 0.5 km/s) is the same as ours, but in the negativevelocities they report the values up to −0.63 km/s and our values amount to −0.3 km/sonly. This discrepancy can be a consequence of the choice of strictly quiet-atmosphereregion and the fact that our data were not corrected for oscillatory fluctuations unlike [3].570 K. BRCˇEKOVA´, ETC.Fig. 5. – The ratios of the integrated intensities in Ca II K against the intensities in the centersof Fe I lines.The range of values in the photosphere under the plage is larger, mostly in negative valuesand exhibits a greater dispersion as well.The coupling of the photosphere and chromosphere is demonstrated by the ratios ofcharacteristics in fig. 4. There is no link between the K1, K3 intensities and those of Fe Iin quiet region. It seems as if the quiet photosphere and chromosphere did not affecteach other, but we can see a coupling effect between K2 and Fe I core intensities. TheK2 intensities slightly increase with increasing Fe I intensities (in both lines). We alsoinvestigated the intensities in K2v and K2r separately, but almost no difference in thedependence was found. In the region of plage all intensities increased significantly. Themean values of K1, K2, K3 intensities increased 2, 5 and 6 times, respectively, according tothe quiet region. The mean values of Fe I line core intensities increased too but only 1.32and 1.64 times for the magnetic non-sensitive and magnetic sensitive line, respectively.The ranges of Fe I intensity values are larger for the magnetic sensitive line than for themagnetic non-sensitive line. The dependence on the Fe I intensity is apparent just inthe K1 intensity, because the K1 minimum in the Ca II K line is formed in the heightsaround 500 km, relatively close to the height of the formation of the photospheric lines(370 km). The most intensive increase of Ca II K intensities in plage is found in K2 (5times) and K3 (6 times), which are formed in a higher atmosphere and are considered asindicators of the chromospheric activity.The dependence of the Ca II K integrated intensity on the intensity in Fe I lines (fig. 5)has nearly the same shape as in fig. 4 for the K2 peak. This means that the integratedintensity is mostly influenced by the K2 intensity. Our values of the integrated intensitiesare smaller in quiet region and larger in plage than those found in [4].The derived relations of the photospheric and chromospheric line characteristics canbe used as the check of the available semi-empirical 1D hydrostatic models of the solarplage atmosphere [5-7]. Our selection of the typical quiet and plage scans can be a goodtool for verification of these basic models.∗ ∗ ∗This work was supported by GA SAV (grant VEGA 2/7229/20) and the internationalcollaboration with the Austrian Academy of Sciences. AH thanks the Austrian Fonds zurFo¨rderung der wiss. Forschung (Proj. 13308). AK, JR and HW thank the DFG GrantDYNAMICS OF THE SOLAR PHOTOSPHERE AND CHROMOSPHERE ETC. 571436 SLK 113/7/0-1. The Vacuum Tower Telescope is operated by the Kiepenheuer-Institut fu¨r Sonnenphysik, Freiburg at the Observato´rio del Teide of the Instituto deAstrof´ısica de Canarias.REFERENCES[1] Kucˇera A., Hanslmeier A., Ryba´k J. and Wo¨hl H., this issue, p. 703.[2] Carlsson M. and Stein R. F., Astrophys. J., 440 (1995) L29.[3] Berrilli F., Florio A., Consolini G. et al., Astron. Astrophys., 344 (1999) L29.[4] Lemaire P., Chouco-Bruston M. and Vial J. C., Solar Phys., 90 (1984) 63.[5] Vernazza J. E., Avrett E. H. and Loeser R., Astrophys. J. Suppl., 45 (1981) 635.[6] Ayres T. R., Testerman L. and Brault J. W.,, Astrophys. J., 304 (1986) 542.[7] Kucˇera A. and Baranovsky E. A., in Infrared Solar Physics, in Proceedings of the IAUSymposium, No. 154, edited by Rabin D. M. et al. (Netherlands) 1994, pp. 29-33.

Dynamics of the solar photosphere and chromosphere derived from high resolution Fe I and Ca II spectra

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Dynamics of the solar photosphere and chromosphere derived from high resolution Fe I and Ca II spectra

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