Figure 4 - uploaded by R. Kitai
Content may be subject to copyright.
Temporal variation of the area of pore + penumbra in the G-band (black diamond), pore + penumbra in Ca ii H (red triangle), and dark umbra in the G-band (black plus). The solid lines show smoothed variation with about a one hour width. The black arrows at the top of the plot indicate the timing of the frames in Figure 3. (A color version of this figure is available in the online journal.)
Source publication
We analyze the evolution of a pore in the active region NOAA 10940 using the data obtained by the Hinode satellite on 2007 February 3. The pore we analyzed showed the formation of a rudimentary penumbra structure, succeeded by an abrupt disappearance after about 5 hr. The pore had an approximate radius of 3.5 Mm and a total magnetic flux of 3.0 × 1...
Context in source publication
Context 1
... 3 and its contours demonstrate the effectiveness of our intensity threshold method. Figure 4 shows the plots of the area of the dark umbra and pore + penumbral area in both the G-band and Ca ii H. At first, only the naked pore was seen both in the G-band and Ca ii H, and area of this initial naked pore was almost the same in both the G-band and Ca ii H, i.e., 40 Mx 2 . ...
Similar publications
Aims. The main aim of the present analysis is to decipher (i) the small-scale bright features in solar images of the quiet Sun and active regions obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) and (ii) the ALMA correspondence of various known chromospheric structures visible in the H-alpha images of the Sun. Methods. Small-sc...
The solar filaments obtained from the daily Ca ii K3 observations at the Coimbra Astronomical Observatory, which is now called the Geophysical and Astronomical Observatory of the University of Coimbra (OGAUC), for the period 1929 – 1941 have been digitized and validated, and they are confirmed to be reliable for solar activity studies. We use these...
High-resolution observations of small-scale activity above the filamentary structure of a fast-rotating sunspot of NOAA Active Region 10930 are presented. The penumbral filament that intrudes into the umbra shows a central dark core and substructures. It almost approached another end of the umbra, like a light bridge. The chromospheric Ca ii H imag...
This work is a continuation of the author's studies,1,2,3 related to the elucidation of the physical nature of dark sunspots. They showed that the appearance of cold sunspots, the temperature of which is below the temperature of the photosphere, is incompatible with the second law of thermodynamics. Sunspots in the Sun's photosphere can only be hot...
The relationship between F2-layer critical frequencies (foF2), total sunspot number (Ri), northern hemisphere sunspot number (Rn) and southern hemisphere sunspot number (Rs) at station located in mid-latitudes on latitude near to latitude of Iraq (Rome station, lat.: 42 o N and lon.: 13 o E) and for 2003(the descending phase of solar cycle 23) were...
Citations
... Moat flow has been found around the decaying sunspots whose velocity decreased with the decay of sunspots. In addition, various studies have suggested that in the phase of sunspot decay the horizontal magnetic fields within the penumbra undergo a transformation, becoming vertical (Bellot Rubio, Tritschler, and Martínez Pillet, 2008;Watanabe, Kitai, and Otsuji, 2014;Verma et al., 2018)). As these penumbral magnetic fields rise towards the chromosphere due to buoyancy, the penumbra of the sunspot gradually diminishes in the photosphere. ...
In this study, we investigate the decay of sunspots in the active region NOAA 13229 using data from the ASO-S/FMG and SDO/HMI. We closely examine the decay patterns of sunspots S1 and S2, which reveal different decay rates and features due to the mechanisms of magnetic cancellation, dispersion, and the role of horizontal flows. Our analysis highlights the significant impact of magnetic flux changes, including the decrease of both the sunspot area and magnetic flux over time, which adheres to distinct decay laws. This study elucidates the complex interplay between magnetic submergence, cancellation, and dispersion in the sunspot decay process, contributing to our understanding of the underlying mechanisms driving these phenomena. Our results emphasize the importance of horizontal flow dynamics in shaping the decay characteristics of sunspots, providing insights for the role played by the magnetic and plasma processes in solar active regions.
... They suggested that a part of the penumbral magnetic field converts into an umbral field, and the penumbral field becomes more vertical. Watanabe et al. (2014) investigated the formation and decay of a penumbra around a pore and found that the penumbral magnetic field also becomes more vertical during the decay of the penumbra. They proposed that the recovery of a dark umbral area may be responsible for the change of the penumbral magnetic field inclination angle. ...
... For sunspot S2, the magnetic field of the penumbra becomes vertical, and the mean B z of the penumbra increases. This result is similar to those of previous studies (Wang et al. 2004;Watanabe et al. 2014). There are some possible interpretations, for instance, the submergence of the horizontal magnetic field in the penumbra (Peng et al. 2023), the reconstruction of the magnetic field caused by flares (Wang et al. 2012), or flux emergence (Verma et al. 2018). ...
The relationship between the decay of sunspots and moving magnetic features (MMFs) plays an important role in understanding the evolution of active regions. We present observations of two adjacent sunspots, the gap between them, and a lot of MMFs propagating from the gap and the sunspots' outer edges in NOAA Active Region 13023. The MMFs are divided into two types based on their magnetic field inclination angle: vertical (0° < γ < 45°) and horizontal (45° ≤ γ < 90°) MMFs (V-MMFs and H-MMFs, respectively). The main results are as follows: (1) the mean magnetic flux decay rates of the two sunspots are −1.7 × 10 ²⁰ and −1.4 × 10 ²⁰ Mx day ⁻¹ ; (2) the magnetic flux generation rate of all MMFs is calculated to be −1.9 × 10 ²¹ Mx day ⁻¹ , which is on average 5.6 times higher than the total magnetic flux loss rate of the sunspots; (3) the magnetic flux of V-MMFs (including a pore separated from the sunspots) is 1.4 times larger than the total lost magnetic flux of the two sunspots, and in a later stage when the pore has passed through the reference ellipse, the magnetic flux generation rate of the V-MMFs is almost the same as the magnetic flux loss rate of the sunspots; and (4) within the gap, the magnetic flux of V-MMFs is one-third of the total magnetic flux. Few V-MMFs stream out from the sunspots at the nongap region. All observations suggest that MMFs with vertical magnetic fields are closely related to the disintegration of the sunspot, and most of the MMFs from the gap may originate directly from the sunspot umbra.
... The former scenario is supported by a large number of observations. Numerous observational studies have suggested that the horizontal magnetic fields of the penumbra become vertical during the process of sunspot decay Watanabe et al. 2014;Verma et al. 2018). In this process, the horizontal magnetic fields of the penumbra would gradually rise to a higher atmosphere, eventually causing the disappearance of the penumbra in the photosphere. ...
... Brummell et al. (2008) proposed that the horizontal emerging fields could be dragged downward by magnetic pumping caused by the granular convection. A magnetic pumping model is suggested as a mechanism for the formation of a rudimentary penumbra (Watanabe et al. 2014). Once the external granular convection is enhanced, the sunspot is in an unstable state. ...
We present observations of the rapid decay of a penumbral sector associated with a strong light bridge (LB) in the active region NOAA 12680 by analyzing the scattered light-corrected Solar Dynamics Observatory/Helioseismic and Magnetic Imager data. At the beginning of penumbral decay, some dark structures gradually broke away from the umbra to which they were attached. The intensity, vertical field strength, and magnetic inclination of the dark structures are intermediate between those of the umbra and penumbra. And a strong LB formed in the umbra, which originated from the intrusion of neighboring penumbral filaments. With the formation of an LB, the total magnetic flux in the whole penumbra decreased, and a penumbral sector of the sunspot rapidly disappeared on one side of the LB. After performing a partition analysis of the penumbra, it was found that the decay rate in this region of the penumbral sector is significantly accelerated after the appearance of an outward motion of magnetic flux along the LB. The area of this penumbral sector decreased from 21–16 MSH in 4 hr. The reduction in area in this penumbral sector is accompanied by a large decay rate of the magnetic flux, 2.5 × 10 ¹⁹ Mx hr ⁻¹ . These results suggest that the rapid decay of the penumbral sector is associated with the LB. The appearance of dark structures in the penumbra and the strong LB in the umbra may offer a hint that the origin of massive flux migration from the sunspot umbra may have accelerated the decay of the sunspot.
... It is unclear what changes occur in the magnetic field parameters during decay. Observations suggest that the horizontal magnetic field of the penumbra would gradually rise and become vertical at the initial stage of sunspot decay (Bellot Rubio et al. 2008;Watanabe et al. 2014;Verma et al. 2018). As a result, the penumbra of the decaying sunspot would disappear in the photosphere. ...
... The change of the horizontal magnetic field in the penumbra is a significant process during the sunspot decay (Watanabe et al. 2014;Rempel 2015;Verma et al. 2018). According to the analysis of the sunspot in the AR 12662, it can be found that not only the horizontal magnetic field of the penumbra changes but also the magnetic field of the umbra changes during the decay of the sunspot. ...
The relationship between the continuum intensities and magnetic fields for stable and decaying sunspots is analyzed using the scattered-light-corrected data from the Helioseismic and Magnetic Imager. From our analysis, the main differences between stable and decaying sunspots are as follows. In the continuum intensity range from 0.35 I qs to 0.65 I qs , where I qs is the continuum intensity of the quiet solar surface, the relationship between continuum intensity and transverse magnetic field and the relationship between continuum intensity and inclination display a much higher scatter during the decaying phase of the sunspots. During and after the formation of the light bridge, the scatter plots show a bifurcation that indicates that the two umbrae separated by the light bridge have different thermodynamic properties. The continuum intensity of the umbra in a decaying sunspot is brighter than that of the stable sunspot, indicating that the temperatures in the umbra of decaying sunspots are higher. Furthermore, our results show that the mean continuum intensity of the umbra gradually increases during the decay of the sunspot, but the mean continuum intensity of the penumbra remains constant. Simultaneously, the vertical and transverse magnetic field strengths in the umbra gradually decrease, and the vertical magnetic field strengths in the penumbra gradually increase. The changes in the umbra occur earlier than the changes in the penumbra of the decaying sunspot, suggesting that the umbral and penumbral decay may be an interdependent process during the decay of the sunspot.
... Furthermore, some studies suggested that the horizontal magnetic fields of the penumbra would become vertical at the initial stage of sunspot decay (Bellot Rubio et al. 2008;Watanabe et al. 2014;Verma et al. 2018). As the penumbral magnetic field gradually rises to the chromosphere by buoyancy, the penumbra of the sunspot would disappear in the photosphere. ...
... These results imply that the magnetic field lines in the penumbra become more vertical during the decay of the sunspot. This result is in agreement with the ideas of Bellot Rubio et al. (2008) and Watanabe et al. (2014), who suggested that the horizontal magnetic field in the decaying penumbra would become vertical. The magnetic field in the penumbra becomes more vertical, and the magnetic flux will rise correspondingly. ...
To better understand the decay of different types of sunspots, we studied the decay of eight α -configuration sunspots by using the data that were acquired by the Helioseismic and Magnetic Imager on board the Solar Dynamic Observatory. We followed their decay for about four days and analyzed the evolution of their photospheric area and magnetic field parameters. We found that the area and total magnetic flux of α sunspots show a near-linear decrease during their decay. Meanwhile, the area decay rate of an individual sunspot is not constant. The area decay of a sunspot can be divided into two stages, a slow and a rapid decay process. Moreover, according to the difference of the area decay of the penumbra and umbra, the α sunspots decay can be classified in three ways: the penumbra and umbra decay synchronously, the penumbra decays first, and the umbra decays first. In addition, the flux decay of the penumbra is lagging behind the decay of the penumbral area. This finding suggests that the vertical magnetic field of the sunspot penumbra increases significantly in the early stage of sunspot decay.
... Jurčák et al. (2017) further analyzed the penumbral formation of a pore and confirmed the necessity of B stable ver for establishing a stable umbra-penumbra boundary (Jurčák et al. 2015). They found that the penumbra grew at the expense of the magnetic flux of the pore, which supports the result proposed earlier by Watanabe et al. (2014). When the rudimentary penumbral filaments formed, Watanabe et al. (2014) observed that the area of the dark umbra gradually decreased. ...
... They found that the penumbra grew at the expense of the magnetic flux of the pore, which supports the result proposed earlier by Watanabe et al. (2014). When the rudimentary penumbral filaments formed, Watanabe et al. (2014) observed that the area of the dark umbra gradually decreased. However, during the process of penumbral decay, they found that the horizontal penumbral field became vertical, resulting in the recovery of the umbral area. ...
... Conclusions on whether the penumbra developed at the expense of the umbral magnetic flux remain contradictory. Jurčák et al. (2015) proposed that the penumbra developed at the cost of the pore magnetic flux, which supports the result suggested earlier by Watanabe et al. (2014). They found that the umbral area of a sunspot decreased during the formation of its penumbra. ...
To better understand the formation and decay of sunspot penumbrae, we studied the evolution of sunspots in three regions of the active region NOAA 12673 in detail. The evolution of sunspots in the three regions was involved in the interaction of two magnetic field systems: the preexisting magnetic field system and the later-emerging magnetic field system. Through analyzing the photospheric magnetic field properties, it is found that the formation of the penumbra originated from newly emerging magnetic bipoles that were trapped in the photosphere. The change in magnetic field in a penumbra from horizontal to vertical can cause the disappearance of the penumbra. A transformation of the magnetic field between the umbra and the penumbra is found, and the outward moat flow around the sunspot gradually decreased and vanished during decay of the sunspot. In addition, we found that the mean longitudinal magnetic strength in the penumbra decreased and the mean transverse magnetic strength in the penumbra increased with the increasing penumbral area during the formation of sunspots. However, during the decay of sunspots, the mean longitudinal magnetic strength in the penumbra increased, and the mean transverse magnetic strength in the penumbra decreased with decreasing penumbral area. Comparatively, the dependence of the area and the mean transverse/longitudinal magnetic field strength in the umbra is not remarkable. These results reveal that the formation and decay process of umbra are different from penumbra.
... The birth of sunspots is associated with successive emergence of magnetic flux, and it often initially appeared as naked umbra (also refers to pore) when the flux just rises through the convection zone to the solar surface (Leka & Skumanich 1998). When the pore has grown to sufficient total magnetic flux, the magnetic field at its outer edge becomes more inclined to the vertical, further interacts with the surrounding granular convection, and eventually leads to the production of penumbra (Leka & Skumanich 1998;Watanabe et al. 2014). Jurčák et al. (2017) also reported a case in which, when the vertical magnetic field was not strong enough, a small pore could completely transform to an orphan penumbra due to the predominantly vertical field becoming horizontal. ...
Sunspot structures can be significantly affected by major flares. In this study, we reported a large penumbral area experiencing two kinds of transformations during the flare SOL2013-11-03T05:22 (M5.0). One penumbral segment decayed and transformed into a small pore when swept by the flare ribbon. At the same time, an adjacent penumbral segment expanded, permeating the granular area along the flaring magnetic polarity inversion line. EUV and X-ray observations indicated that the penumbral enhancement area was close to the flare center, while the penumbral decay area was on the relatively outer side. By tracking the magnetic motions and local magnetic field changes, we found that the magnetic transformations within two regions were totally different during the flare. The central penumbral enhancement area was accompanied by the field collapsing down, whereas the outer penumbral decay area was associated with the field lifting up toward the upper flare center. Particularly, following the uplift motion of the magnetic fields in the outer region, the magnetic flux in the decaying penumbra decreased and that in the forming pore subsequently increased. These results implied that the rearrangement of the magnetic field during the flare would be the action that resulted in the variations of sunspot structures.
... The newly formed penumbra sector developed at the expense of the umbra. As mentioned above, penumbral formation requires sufficient magnetic flux, which can be supplied by the emerging region or umbrae (Leka & Skumamich 1998;Lim et al. 2013;Watanabe et al. 2014;Zuccarello et al. 2014;Jurčák et al. 2017). At the first stage of new penumbral formation, from 17:48 to 20:24 UT, the magnetic flux of the new penumbra sector increased during this period, and the additional magnetic flux was provided by the emerging region. ...
We present a particular case of the formation of a penumbra sector around a developing sunspot in the active region NOAA 12574 on 2016 August 11 by using the high-resolution data observed by the New Solar Telescope at the Big Bear Solar Observatory and the data acquired by the Helioseismic and Magnetic Imager and the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory satellite. Before the new penumbra sector formed, the developing sunspot already had two umbrae with some penumbral filaments. The penumbra sector gradually formed at the junction of two umbrae. We found that the formation of the penumbra sector can be divided into two stages. First, during the initial stage of penumbral formation, the region where the penumbra sector formed always appeared blueshifted in a Dopplergram. The area, mean transverse magnetic field strength, and total magnetic flux of the umbra and penumbra sector all increased with time. The initial penumbral formation was associated with magnetic emergence. Second, when the penumbra sector appeared, the magnetic flux and area of the penumbra sector increased after the umbra's magnetic flux and area decreased. These results indicate that the umbra provided magnetic flux for penumbral development after the penumbra sector appeared. We also found that the newly formed penumbra sector was associated with sunspot rotation. Based on these findings, we suggest that the penumbra sector was the result of the emerging flux that was trapped in the photosphere at the initial stage of penumbral formation, and when the rudimentary penumbra formed, the penumbra sector developed at the cost of the umbra. © 2018. The American Astronomical Society. All rights reserved..
... This height dependence was derived by comparing the magnetic field obtained from the infrared lines Fe i 1078.3 nm and Si i 1078.6 nm. Watanabe et al. (2014) observed formation and decay of a rudimentary penumbra in a protospot (Leka & Skumanich 1998), where the penumbra developed at the expense of umbral magnetic flux. While the penumbra decayed, they observed that the penumbral field became vertical resulting in the recovery of umbral area, i.e., penumbral decay leads to rearrangement of magnetic field lines. ...
Aims. Combining high-resolution spectropolarimetric and imaging data is key to understanding the decay process of sunspots as it allows us to scrutinize the velocity and magnetic fields of sunspots and their surroundings.
Methods. Active region NOAA 12597 was observed on 2016 September 24 with the 1.5-meter GREGOR solar telescope using high-spatial-resolution imaging as well as imaging spectroscopy and near-infrared (NIR) spectropolarimetry. Horizontal proper motions were estimated with local correlation tracking, whereas line-of-sight (LOS) velocities were computed with spectral line fitting methods. The magnetic field properties were inferred with the “Stokes Inversions based on Response functions” (SIR) code for the Si I and Ca I NIR lines.
Results. At the time of the GREGOR observations, the leading sunspot had two light bridges indicating the onset of its decay. One of the light bridges disappeared, and an elongated, dark umbral core at its edge appeared in a decaying penumbral sector facing the newly emerging flux. The flow and magnetic field properties of this penumbral sector exhibited weak Evershed flow, moat flow, and horizontal magnetic field. The penumbral gap adjacent to the elongated umbral core and the penumbra in that penumbral sector displayed LOS velocities similar to granulation. The separating polarities of a new flux system interacted with the leading and central part of the already established active region. As a consequence, the leading spot rotated 55° clockwise over 12 h.
Conclusions. In the high-resolution observations of a decaying sunspot, the penumbral filaments facing the flux emergence site contained a darkened area resembling an umbral core filled with umbral dots. This umbral core had velocity and magnetic field properties similar to the sunspot umbra. This implies that the horizontal magnetic fields in the decaying penumbra became vertical as observed in flare-induced rapid penumbral decay, but on a very different time-scale.
... Some pores evolve into mature sunspots with a penumbra, while others do not. Despite many statistical (Collados et al. 1987;Keppens & Martínez Pillet 1996;Suetterlin 1998;Padinhatteeri 2013;Tlatov & Pevtsov 2014) and observational studies (Zuccarello et al. 2009;Schlichenmaier et al. 2010;Rezaei et al. 2012;Shimizu et al. 2012;Lim et al. 2013;Louis et al. 2013;Watanabe et al. 2014) of penumbra formation, the key condition that is required for a sunspot to develop a penumbra is still not well understood. The classification and statistical study of the physical properties of pores, transitional sunspots, and mature sunspots using a homogeneous data set is required in order to increase our comprehensive understanding of the dynamics and evolution of a vertical magnetic flux tube. ...
We carried out an extensive statistical study of the properties of pores and sunspots, and investigated the relationship among their physical parameters such as size, intensity, magnetic field, and the line-of-sight (LOS) velocity in the umbrae. For this, we classified 9881 samples into three groups of pores, transitional sunspots, and mature sunspots. As a result, (1) we find that the total magnetic flux inside the umbra of pores, transitional sunspots, and mature sunspots increases proportionally to the powers of the area and the power indices in the three groups significantly differ from each other. (2) The umbral area distribution of each group shows a Gaussian distribution and they are clearly separated, displaying three distinct peak values. All of the quantities significantly overlap among the three groups. (3) The umbral intensity shows a rapid decrease with increasing area, and their magnetic field strength shows a rapid increase with decreasing intensity. (4) The LOS velocity in pores is predominantly redshifted and its magnitude decreases with increasing magnetic field strength. The decreasing trend becomes nearly constant with marginal blueshift in the case of mature sunspots. The dispersion of LOS velocities in mature sunspots is significantly suppressed compared to pores. From our results, we conclude that the three groups have different characteristics in their area, intensity, magnetic field, and LOS velocity as well in their relationships. © 2015. The American Astronomical Society. All rights reserved.
