Investigation of the evolution of coronal bright points and magnetic field topology

ISSN 1063-7737, Astronomy Letters, 2014, Vol. 40, No. 8, pp. 510–518. c© Pleiades Publishing, Inc., 2014.Original Russian Text c© E.P. Minenko, N.V. Karachik, I. Sattarov, A.A. Pevtsov, 2014, published in Pis’ma v Astronomicheskiı Zhurnal, 2014, Vol. 40, No. 8, pp. 566–574.

Investigation of the Evolution of Coronal Bright Points and MagneticField Topology

E. P. Minenko1*, N. V. Karachik2**, I. Sattarov2***, and A. A. Pevtsov3****

1Ulugh Beg Astronomical Institute, Academy of Sciences of Uzbekistan, ul. Astronomicheskaya 33,Tashkent, 100052 Uzbekistan

2Tashkent State Pedagogical University, ul. Yusuf Xos Xojib ko‘chasi 103, Tashkent, 100070 Uzbekistan3National Solar Observatory, Sacramento Peak, 3010 Coronal Loop, Sunspot, NM 88349 USA

Received November 25, 2013

Abstract—Our investigation has been carried using the instruments onboard the Solar Dynamics Ob-servatory (SDO) providing a high resolution of images (AIA photographs and HMI magnetograms).We have investigated the structure and magnetic evolution of several coronal bright points and small-scale N–S polarity magnetic fluxes closely associated with them. We also compare the evolution of themagnetic polarities of elementary isolated sources of positive and negative fluxes (magnetic bipoles) andcoronal bright points. Tiny (“elementary”) coronal bright points have been detected. A standard coronalbright point is shown to be a group of “elementary” coronal bright points that flare up sequentially. Ourinvestigation shows that a change in the magnetic fluxes of opposite polarities is observed before the flare ofa coronal bright point. We show that not all cases of the formation of coronal bright points are described bythe magnetic reconnection model. This result has not been considered previously and has not been pointedout by other authors.

DOI: 10.1134/S1063773714080064

Keywords: Sun, coronal bright points, magnetic field.

INTRODUCTION

Coronal bright points (CBPs), also known as X-ray bright points (XBPs), are small-scale (with amaximum size from a few to 15–30 arcsec in di-ameter) transient structures usually observed at hightemperatures in the solar corona. XBPs were firstdetected in the X-ray images of the Sun obtained withan Aerobee sounding rocket in 1969 (van Speybroecket al. 1970). Subsequently, these coronal struc-tures were studied in detail with X-ray and ultraviolettelescopes in various orbital and suborbital missions(Golub et al. 1974; Hara and Nakakubo-Morimoto2003; McIntosh and Gurman 2005; Sattarov et al.2002). The identification of XBPs and CBPs asa single structure observed at various wavelengthswas proposed by Sattarov et al. (2002) and Webbet al. (1993). According to existing views, CBPs aredefined as small ejections in the lower corona with alifetime from a few minutes to several days, which, on

*E-mail: [email protected];[email protected]

**E-mail: [email protected]***E-mail: [email protected]

****E-mail: [email protected]

average, is approximately 8–9 h (Golub et al. 1974,1977; Priest et al. 1994). The total number of CBPsdecreases with coronal temperature (McIntosh andGurman 2005; Sattarov et al. 2004); this allowsthem to be attributed to low-corona structures. Inmost cases, CBPs are closely associated with small-scale (about 20 arcsec in diameter) magnetic bipolarand unipolar fields in the photosphere (Golub et al.1977; Harvey et al. 1975, 1985). Isolated elementarysources of positive and negative fluxes in the photo-sphere were first described by Frazier (1972). In fact,in the case of destruction of bipolar or unipolar struc-tures in the photosphere, XBPs resulting from mag-netic reconnection between a pair of fluxes of oppositepolarities (Priest et al. 1994) are commonly observedin the corona (Harvey et al. 1985). The model ofCBP formation as a result of repeated reconnectionbetween two previously unconnected magnetic poleswas subsequently proposed (Longcope and Kankel-borg 1999; Longcope et al. 2001; Longcope 1998).Whereas “elementary” magnetic reconnection in thecase of a single CBP is accompanied by the release ofa small amount of energy (∼5 × 1026 erg) (Longcopeand Kankelborg 1999), the combined effect of a large

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number of CBPs can be very significant in the totalenergy balance in the solar-corona heating.

By studying the XBP orientation and investigat-ing the origin of the bipolar regions responsible forthe formation of XBPs, Ueda et al. (2010) foundthat about 24% of the XBPs are due to emergingbipoles, while the remaing 76% are due to chanceencounters of opposite polarities. An investigationof the correspondence between CBPs and magneticbipolar structures showed that most CBPs arise fromthe decay of such structures. It was also pointed outthat only a small fraction of CBPs are observed in-dependently of ephemeral active regions (Webb et al.1993). Previously, McIntosh and Gurman (2005) andSattarov et al. (2002) proposed to divide CBPs intotwo types: (1) CBPs associated with active regionsand (2) quiet-Sun CBPs. It was found that the CBPorientation corresponds to this model of two typesand that the CBPs associated with active regionsare biased to the E–W orientation, while the quiet-Sun CBPs are oriented more randomly (Ueda et al.2010). The latitudinal distribution of CBPs associ-ated with active regions is biased to active latitudesor activity zones (Sattarov et al. 2005a). The distri-bution of quiet-Sun CBPs points to the presence ofquantized distances within the size of supergranules,suggesting that the network of magnetic fields at theboundaries of a supergranulation cell can play a rolein the formation of this type (Sattarov et al. 2005b).In early studies (Golub et al. 1974), a change inthe number of CBPs in antiphase with the sunspotcycle was pointed out. This variant of the (anti)cyclewas initially explained by the visibility effect, whena brightening of the corona can make it difficult toidentify CBPs in periods of high solar activity (Haraand Nakakubo-Morimoto 2003; Nakakubo and Hara2000; Sattarv et al. 2002). On the other hand, theseparation of CBPs into two types based on theirbrightness showed that the number of “bright” CBPsvaries, while the number of “dim” CBPs changes inantiphase with the solar cycle (Sattarov et al. 2010).The fact that the number of CBPs anticorrelates withthe solar cycle is typical of the quiet-Sun latitudes.A shift of approximately two years was also found inthe local minima and maxima, suggesting a delay ofthe solar cycle from the cyclic curve of the numberof active-Sun CBPs (Sherdanov et al. 2012). Thisbehavior can serve as evidence that the cyclic changesin the number of CBPs can affect both physical pro-cesses, the solar activity variation and the visibilityeffect.

In several studies, it was pointed out that the totalnumber of CBPs in one image of the full solar diskis, on average, ∼300–400 (Longcope et al. 2001;Nakakubo and Hara 2000; Sattarov et al. 2002).Thus, the total mean energy released as a result of

all the emerging CBPs can be estimated as ∼2 ×1029 erg. Based on their study of sympathetic CBPs,Zhang and Ji (2013) assert that such ejections ofenergy and matter can be associated with chromo-spheric evaporation, which, in turn, is caused by ther-mal conduction originating from the primary CBP.However, it should be noted that CBPs usually haveno analog in chromospheric lines. Thus, the pos-sible processes described by Zhang and Ji (2013)are similar to chromospheric evaporation in the lowercorona. Observations show that the CBP heatingrate changes dramatically in short times, supportingthe models with magnetic reconnection as a possiblemechanism for the origin of CBPs (Kariyappa et al.2011).

In recent studies, a model has been presented inwhich a small bipolar magnetic region forms a loop-like structure in the coronal layer. The formation ofthis magnetic structure is associated with the pres-sure instability in different layers of the solar atmo-sphere and turbulence (Warnecke et al. 2013). Onthe other hand, Yoshimura (2012) points out that,despite the fact that coronal loops occasionally appearin the process of reconnection between photosphericmagnetic elements of opposite polarities in newlyemerging magnetic bipoles, their presence and theoccurring processes (the cancelation of fluxes, theirdestruction) do not affect the heating of coronal loops.The observed facts suggest that it is necessary tosearch for other mechanisms for the heating of coro-nal loops and, as a consequence, the coronal heating.

Recent observations associate (at least some)CBPs with coronal jets that can accelerate the out-flow of matter from the lower corona, which providesa basis for the formation of the solar wind (Cirtainet al. 2007). Jiang et al. (2013) described severalloop-type jets with small bipoles developing at thecenter. Moore et al. (2011) found that many ofthe coronal jets associated with short-lived bipolesdemonstrating an expansion of the hot corona canprovide enough energy for complete or partial heatingof the corona. Thus, a study of the CBP phenomenoncan provide important information for a better under-standing of the coronal heating mechanism and theorigin of the solar wind.

THE DATA AND THE METHODS USED

Most of the previous studies of CBPs have beencarried out using coronal images and photosphericmagnetograms with a low spatial resolution and a lowcadence, which restricted the studies of the topolog-ical properties and fast evolution of such small-scalestructures as CBPs. At present, high-resolution datawith the necessary cadence can be obtained with the

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Fig. 1. Example of the development of CBP no. 1 in the AIA image (left) with the corresponding region with the lower-lyingN–S polarity magnetic fluxes on the HMI magnetogram (right).



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instruments onboard SDO (Pesnell et al. 2012). Us-ing the SDO data allows the properties of CBPs andthe small-scale magnetic fields associated with themto be studied in more detail. We used the dense datasets obtained with the AIA and HMI instruments overa period of 38 h (from 10:00 on December 31, 2012,to 23:59 on January 1, 2013). To trace CBPs in thecorona, we used the AIA images in the 193 A (FeXII/XXIV) line with a 12-s cadence and a spatialresolution of ∼0.6 arcsec per pixel. To monitor themagnetic flux of bipolar structures, we used photo-spheric HMI magnetograms of the full disk in the6173 A (Fe I) line with a spatial resolution of about0.6 arcsec and 45-s cadence. The AIA and HMI dataobtained were processed in accordance with the stan-dard processing procedure for each instrument. Weconsidered examples of ten visually selected CBPs invarious areas in the AIA images taken over the abovetime interval of 38 h. When choosing CBPs, we cutoff the areas immediately adjacent to the solar limband large active regions. We recorded the appearanceand disappearance of a specific CBP based on theadopted intensity threshold, i.e., CBP was deemeda disappearing one when the intensity at the CBPlocation dropped below the mean intensity with a 3σ

error (the standard deviation from the mean). Eachindividual image fragment centered at the coordinatesof a specific CBP (300× 300 pixels in size) was dupli-cated on magnetograms, revealing a bipolar and oftenunipolar structure in the photosphere. We tracedthe integrated parameters for each CBP, i.e., its area,mean intensity, maximum intensity, and the change inmagnetic bipolar fluxes for the lower-lying magneticelements during the CBP lifetime. Figure 1 showscomplex interactions between the concentration ofmagnetic fluxes with opposite polarities and CBP(designated as CBP no. 1) over the entire lifetime ofthe latter.

RESULTS OF MEASUREMENTSAND ANALYSIS

In Fig. 1, before the appearance of a CBP flare inthe corona, a sharp convergence of bipolar fluxes isrecorded, which is also clearly seen in Fig. 2, wherethe result of the flux convergence is a sharp jumpin maximum intensity. Subsequently, the fluxes arestabilized and again diverge; during all this time,CBP is observed higher in the corona. It should benoted that in the case under consideration, before theCBP disappearance, several peaks are observed on


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the intensity curve, and during its disappearance theCBP, as it were, breaks up into several separate flares.Before the disappearance of CBP no. 1, the fluxes arestabilized; subsequently, gradually decreasing, theflux of positive polarity disappears, while the flux ofnegative polarity (the leading flux in this hemisphere)remains. It is surmised that a new CBP develops asthe two poles of opposite polarities converge, but inthe case of CBP no. 1, a new CBP is observed whenthe poles diverge (Fig. 1).

At first glance, the CBP emerges oriented along anarbitrary line connecting the two poles. However, oncloser examination, the CBP has several connectionswith the main negative pole and the weak positivepolarity above the negative flux. Figure 2 shows aCBP for which the nature of the intersection of themagnetic field lines with the photospheric surface isnot completely clear. In this case, the CBP mostlikely consists of several loops. Presumably, the P1–N1 and P2–N2 fluxes produce a larger loop, N1–P3 produces a smaller loop, but actually the distri-bution of magnetic field lines has a more complexstructure. If CBP is associated with a magnetic pairof P–N polarity, then its development should implythe final instant of this “interaction.” This contra-dicts the universally accepted model, in which thebeginning of magnetic interactions between the two

poles gives rise to a CBP in the corona. Initially, theCBP (Fig. 2) flares up above the region between twonegative and one positive fields (see the fragments ofmagnetograms). However, based on its orientationand location, we can assume that it can be associatedwith a pair of fluxes with opposite polarities. On theother hand, the observed evolution of the magneticfluxes shows that before the development of a CBPand after its disappearance, the flux of positive polaritymoves toward the nearest flux of negative polarity.

Over the entire period of observations, small, witha lifetime of no more than two minutes, CBPs flaredup and disappeared for each detected bright pointwithin a limited region. We arbitrarily call these smallCBPs “elementary” ones. Two fluxes of negative andpositive polarities, showing no appreciable changebefore the CBP appearance or disappearance, wereoften located under them.

The observed CBPs revealed a cluster of N–Spolarity fluxes under themselves, not a simple bipolarstructure (except for some “elementary” points). Fig-ure 3 shows an example of a short-lived “elementary”CBP (the lifetime is, on average, about 13–14 minin the set of all the preceding flares) and an exampleof the magnetic topology of opposite-polarity fluxes(top right). The graph shows the temporal variationin the positive and negative magnetic fluxes as well as



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Fig. 4. Example of the development of CBP no. 9 in the AIA image (top) with the corresponding region with the lower-lyingN–S polarity magnetic fluxes on the HMI magnetogram (bottom).


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the area and maximum brightness of an “elementary”bright point (CBP no. 3). The CBP flared up at thisplace three times (at 19:42, 20:28, and 21:00); thelast, longer-duration flare in this region showed moreextensive and three separate bright flares in a rapidsequence. Over the period included in our analysisof CBP no. 3, the magnetic field (of both polarities)showed a small increase followed by a gradual de-crease (see Fig. 3) as well as short-term oscillations.On the other hand, no appreciable decrease in thepositive and negative fluxes (above the level of reg-ular oscillations) is observed, suggesting a possiblecancelation in the case of reconnection. For a CBPforming as a result of magnetic reconnection, onemight expect significant correlation changes of themagnetic flux and brightness.

The examples presented in Figs. 1–3 are indica-tive of the difficulties in selecting CBPs with appro-priate specific magnetic poles. To solve this problem,we obtained the magnetic flux using a small areacentered on each CBP and calculated the magneticflux for all magnetic elements in this area withoutattempting to determine the exact intersections ofthe magnetic field lines of the fluxes with the pho-tosphere. We included only the pixels with a mag-netic flux above 10 G in these calculations. Thisthreshold was chosen by analyzing the errors of lat-itudinal HMI magnetograms (Liu et al. 2012). Theexamples of CBPs we considered clearly demonstrate

the potential difficulties that can arise in identifyingthe magnetic bipolar structures lying at the base ofCBPs at the photospheric level and in elucidating thenature of the evolution of magnetic fluxes and CBPs.Having examined our coronal AIA movies visually,we established that the CBP selected for this studyare either pointlike structures (“elementary” brightpoints) or clusters of such structures (see Figs. 1–3).

Figure 4 shows an example of CBP No. 9 con-sisting of several elementary points that flare up ini-tially sequentially and then simultaneously. At 22:00on December 31, 2013, no flares were observed inthe corona, but a gradual increase in the magneticfluxes of opposite polarities in the photosphere andthe beginning of their gradual convergence can benoted. At about 03:00 on January 1, 2013, a brightflare was recorded in the corona, a possible resultof the preliminary sharp convergence of the poles.The same picture can be observed on the curve ofN–S polarity fluxes below (Fig. 5). The next sharpchange in the fluxes (see Figs. 4 and 5) gave a secondshort-lived flare in the corona with a slightly lowerintensity at 05:00. Subsequently, an increase in thefluxes was again observed, but no flares were observedin the corona (Fig. 4, the time of the images 06:00and 06:30). The magnetograms in this period ex-hibit an increase in the fluxes and the formation ofa unipolar structure. The intensity curve in Fig. 5shows several short-lived peaks at the beginning of



development of CBP no. 9. These peaks representthe flares of “elementary” bright points. These flareswere followed by the flare of the main CBP consistingof a cluster of “elementary” bright points, as hasbeen noted above. This behavior is characteristic ofnonuniform reconnection. On the other hand, just asin the example presented in Fig. 3 (CBP no. 3), nodecrease in the field strength pointing to the cancela-tion of magnetic fluxes was observed. In the case of acluster of “elementary” bright points within the mainCBP, a sharp change in the fluxes of opposite polar-ities (their convergence and growth) was observed,which subsequently was stabilized and terminated bythe cancelation of one of the fluxes. In the case ofCBP no. 9, the unipolar structure lying lower in thephotosphere changes the leading polarity before theappearance of a flare (see Fig. 5) in the corona and inthe end just the positive polarity is canceled.

DISCUSSION AND CONCLUSIONS

We investigated the evolution of the examples ofCBPs in the corona and the corresponding magneticfluxes in the photosphere. We showed that it is of-ten rather difficult to determine the exact nature ofmagnetic reconnection for CBPs. In some cases, thedevelopment of CBPs cannot fit into the traditionalpicture of “flux cancelation.” We considered exam-ples of CBPs developing between opposite polarities,the magnetic interactions during the reconnection ofwhich can entail the disappearance of CBP, withoutbeing the cause of its emergence. Yoshimura (2012)pointed out that some other mechanisms of energyrelease other than magnetic reconnection between apair of magnetic fluxes with opposite polarities in thecase of a flare and a sharp increase in the intensityof some bright points could exist. We also showedan example of CBPs that could emerge above theregion between two polarities, where one polarity canbe drawn into the cancelation of fluxes, while theother one cannot. Therefore, we can surmise thatreconnection originates during the formation of theCBP itself and can be determined by other factors,which are affected by the closeness of the magneticpoles or the changes during their divergence. Theidea that a large-scale magnetic field can affect theCBP orientation and location was proposed previ-ously (Nelson et al. 2000). The CBP intensitycurves clearly show the peaks of maximum intensitythat correspond to the flaring of “elementary” brightpoints. However, the magnetic field data show noconsiderable decrease in the magnetic flux (above thelevel of regular variations) that could point to thecases of cancelation. This absence of manifestationsof flux cancelation can be the result of our approach incalculating the fluxes above the expanded region near

the CBPs considered. However, on the other hand,in the case of a CBP consisting of a cluster of smallelementary bright points, there is a sharp change inthe polarity and an increase in the concentration ofmagnetic fluxes before a flare. To better estimatethe changes in the magnetic fluxes, a modification ofour approach to identifying the latter will possibly berequired. Based on the above examples, we can saythat such a determination will be a difficult problem.

REFERENCES

1. J. W. Cirtain, L. Golub, L. Lundquist, A. van Bal-legooijen, A. Savcheva, M. Shimojo, E. DeLuca,S. Tsuneta, T. Sakao, K. Reeves, M. Weber, R. Kano,N. Narukage, and K. Shibasaki, Science 318, 1580(2007).

2. E. N. Frazier, Solar Phys. 26, 130 (1972).3. L. Golub, A. S. Krieger, J. W. Harvey, and G. S. Va-

iana, Solar Phys. 53, 111 (1977).4. L. Golub, A. S. Krieger, J. K. Silk, A. F. Timothy, and

G. S. Vaiana, Astrophys. J. 189, L93 (1974).5. H. Hara and K. Nakakubo-Morimoto, Astrophys.

J. 589, 1062 (2003).6. K. L. Harvey, Austral. J. Phys. 38, 875 (1985).7. K. L. Harvey, J. W. Harvey and S. F. Martin, Solar

Phys. 40, 87 (1975).8. Y. Jiang, Y. Bi, J. Yang, H. Li, B. Yang, and R. Zheng,

Astrophys. J. 775, 132 (2013).9. R. Kariyappa, E. E. Deluca, S. H. Saar, L. Golub,

L. Dam’e, A. A. Pevtsov, and B. A. Varghese, Astron.Astrophys. 526, A78 (2011).

10. Y. Liu, J. T. Hoeksema, P. H. Scherrer, J. Schou,S. Couvidat, R. I. Bush, T. L. Duvall, K. Hayashi,X. Sun, and X. Zhao, Solar Phys. 279, 295 (2012).

11. D. W. Longcope, Astrophys. J. 507, 433 (1998).12. D. W. Longcope and C. C. Kankelborg, Astrophys.

J. 524, 483 (1999).13. D. W. Longcope, C. C. Kankelborg, J. L. Nelson, and

A. A. Pevtsov, Astrophys. J. 553, 429 (2001).14. S. W. McIntosh and J. B. Gurman, Solar Phys. 228,

285 (2005).15. R. L. Moore, A. C. Sterling, J. W. Cirtain, and

D. A. Falconer, Astrophys. J. 731, L18 (2011).16. K. Nakakubo and H. Hara, Adv. Space Res. 25, 1905

(2000).17. J. L. Nelson, D. W. Longcope, and A. A. Pevtsov, Bull.

Am. Astron. Soc. 32, 1289 (2000).18. W. D. Pesnell, B. J. Thompson, and P. C. Chamberlin,

Solar Phys. 275, 3 (2012).19. E. R. Priest, C. E. Parnell, and S. F. Martin, Astro-

phys. J. 427, 459 (1994).20. I. Sattarov, A. A. Pevtsov, A. S. Hojaev, and

C. T. Sherdonov, Astrophys. J. 564, 1042 (2002).21. I. Sattarov, A. A. Pevtsov, N. V. Karachek, and

C. T. Sherdanov, Multi-Wavelength Invest. Solar Ac-tiv. 223, 667 (2004).


518 MINENKO et al.

22. I. Sattarov, A. A. Pevtsov, N. V. Karachik, andB. J. Sattarova, Large-Scale Struct. Their Role SolarActiv. 346, 395 (2005a).

23. I. Sattarov, A. A. Pevtsov, N. V. Karachik, andB. J. Sattarova, Large-Scale Struct. Their Role SolarActiv. 346, 363 (2005b).

24. I. Sattarov, A. A. Pevtsov, N. V. Karachik, C. T. Sher-danov, and A. M. Tillaboev, Solar Phys. 262, 321(2010).

25. C. T. Sherdanov, E. P. Minenko, A. M. Tillaboev,and I. Sattarov, Astrophys. Space Sci. Proc. 30, 197(2012).

26. L. P. van Speybroeck, A. S. Krieger, and G. S. Vaiana,Nature 227, 818 (1970).

27. K. Ueda, R. Kano, S. Tsuneta, and H. Shibahashi,Solar Phys. 261, 77 (2010).

28. J. Warnecke, I. R. Losada, A. Brandenburg, N. Klee-orin, and I. Rogachevskii, Astrophys. J. 777, L37(2013).

29. S. F. Webb, D. F. Martin, D. Moses, and J. W. Harvey,Solar Phys. 144, 15 (1993).

30. K. Yoshimura, ASP Conf. Ser. 454, 245 (2012).31. Q. M. Zhang and H. S. Ji, Astron. Astrophys. 557, L5

(2013).

Translated by G. Rudnitskii


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Investigation of the evolution of coronal bright points and magnetic field topology