The Lifetime of Sunspot Tlatov, A. G.
Geomagnetism and Aeronomy,
12/2023, Letnik:
63, Številka:
8
Journal Article
Recenzirano
The lifetime of individual solar pores and sunspots is analyzed according to the data of the HMI/SDO space observatory observations in the 24th and 25th activity cycles. It is found that the lifetime ...of individual sunspots and pores
T
differs from the Gnevyshev–Waldmeier rule formulated for groups of sunspots. For regular sunspots, that is, spots with nuclei, there is a linear dependence on the maximum area
S
mx
:
T
sp
= –0.019(±0.2) + 0.027(±0.002)
S
mx
. For solar pores, the dependence of the lifetime on the area has a logarithmic form
T
por
= –0.24(±0.1) + 0.055(±0.014) log(
S
mx
). Possible mechanisms of disintegration of spots and pores are studied. The lifetime for regular spots is probably related to convective currents. It has been established that the average velocity of the matter flow, determined from observations of Doppler velocities, increases with a decrease in the area of sunspots. This can accelerate the decay rate of sunspots with a decrease in the area of sunspots. For solar pores, the lifetime can be determined by the heating mechanism.
Abstract
We use observations taken with a novel solar telescope spectroheliograph to investigate the association between the early filament rise and coronal mass ejections (CMEs). The instrument ...allows the H
α
full line profile to be registered in each pixel of the solar disk with a time cadence of about 1 minute. We analyze observations of three eruptive filaments in 2021 and show that patrol telescope measurements of the H
α
line profile with a spectral resolution
R
= 40,000 can be used to detect precursors of filament eruptions with an advance of several hours and to estimate the initial acceleration of CMEs. Our limited case study also suggests that while detecting an early filament rise may serve as an indicator of a possible eruption, the filament ascent alone is not a definite sign of a CME.
Our analysis of groups of sunspots since the year 1610 till indicates that the Gnevyshev–Ohl rule (GO) displays cycles of inversion with the period of 200years. The latest inversion occurred in the ...Hale double cycle 22–23. Due to that, in several subsequent double cycles the odd cycles should be weaker than their preceding even cycles. Gleissberg cycles with the period of about 100years and variations with the period of 200years are manifested in variations of physical parameters of sunspots and are interconnected. We suggested that the secular minima of the solar activity occur in the vicinity of the extreme points of the 200-year cycles of inversion of the GO rule. The peak of the next secular minimum is expected between the years 2025÷2035. We studied the variations of the physical parameters of sunspots in a Gleissberg cycle. At the maximum phase of the Gleissberg cycle, the average area of groups and the average number of spots in a group reach their maximum. According to our forecast, the amplitude of the 25th solar activity cycle will be somewhat lower than that of the 24th.
This paper presents a procedure for reconstructing the longitudinal magnetic field from observational data of the complete profile of spectral magnetic lines. The method is based on a fast search ...algorithm for curve fitting for complete profiles of magnetically sensitive lines 6301.5 Å and 6302.5 Å. The magnetic field is calculated as the distance between the centers of the
I
-profiles of different polarization components. The centers are defined as the midpoints of the Gaussians approximating the
I
+
V
,
I
–
V
profiles. This approach makes it possible to carry out calculations rather quickly. The presented method makes it possible to reduce the noise in maps of a large-scale magnetic field and improve the accuracy of measurements, primarily of weak fields. The method has been tested to reconstruct the large-scale magnetic field from observations with the STOP full-disk magnetograph telescope (Kislovodsk) in 2014–2022.
The Wang–Shelley–Arge (WSA) solar wind (SW) model is based on the idea that weakly expanding coronal magnetic field tubes are associated with fast SW sources and vice versa. The Flux-Tube Expansion ...factor (FTE) is used to determine the degree of expansion of magnetic tubes. The FTE is calculated based on a model of the coronal magnetic field, usually in the potential approximation. The second input parameter of the WSA model is the distance from the base of the magnetic tube on the photosphere to the boundary of the corresponding coronal hole (Distance to the Coronal Hole Boundary, DCHB). These two parameters of the coronal magnetic field are related empirically to the speed of the solar wind near the Sun. The WSA model has shortcomings and does not fully explain the mechanisms of SW formation. This paper presents an analysis of the degree of correlation of various parameters of the magnetic field (length of field lines, latitude of the base of field lines, etc.) with the observed velocity SW. The parameters are calculated in potential (PFSS) and nonpotential approximations based on three synoptic series of magnetographic observations: the Kislovodsk Solar Telescope for Operative Predictions (STOP), SDO/HMI, and WSO. We found that the FTE correlates relatively weakly with solar wind speed, in contrast to field line lengths and DCHB. We propose an alternative relation to the WSA model that relates the length of field lines, the DCHB, and the amplitude of the magnetic field at the source surface with the velocity SW. The presented relationship is not based on the FTE and shows a better correlation with observations compared to the WSA model. We also optimized the formula in the WSA model for the STOP magnetograph.
Based on the method of averaging the shape of sunspots identified in the HMI/SDO images in the 2010–2022 period, an analysis was made of the relative position of sunspot nuclei during their passage ...across the solar disk. To do this, in different ranges of sunspot areas, we constructed averaged boundaries of the photosphere-penumbra and the core-penumbra. We then tracked changes in sunspot shape at various distances from the center of the disk in the eastern and western hemispheres. A shift of the boundary of sunspot nuclei to the western edge of the sunspot has been observed. The relative value of the shift increases with the area of sunspots. We estimated the value of the Wilson depression for sunspots of various sizes. The magnitude of the depression varies from 100 km for small sunspots to 1000 km for large sunspots. There is some imbalance of the Wilson depression near the eastern and western boundaries of the core-penumbra, depending on the area of the sunspots and their latitude.
—
The possibilities for organizing a solar activity observation service for space weather forecasting are considered. At this stage, the most promising approach is the establishment of a ground-based ...observation network. This network should include solar magnetographs for observing large-scale magnetic fields of the Sun and patrol optical telescopes for detecting coronal mass ejections and solar flares. Magnetographic observations provide data for assessing recurrent solar wind streams. Patrol telescopes operating in continuous mode make it possible to detect eruptive moments and determine parameters of coronal mass ejections at the initial stage. The network can be complemented by other types of observations in radio and optical bands. The article discusses the composition of observation tools as well as methods and models of forecasting.
This paper considers the indices characterizing the minimum activity epoch, according to the data of large-scale magnetic fields and polar activity. Such indices include: dipole–octopole index, area ...and average latitude of the field with dominant polarity in each hemisphere, polar activity seen in polar faculae and Ca
ii
K line bright points, coronal emission line intensity (5303 Å) and others. We studied the correlation between these indices and the amplitude of the following sunspot cycle, and the relation between the duration of the cycle of large-scale magnetic fields and the duration of the sunspot cycle. The obtained relationships allow us to presume that the polar field is formed from the sources of both preceding and the current activity cycles during the decay phase and at the activity minimum. The balance in these sources would therefore determine the features of the following sunspot cycle. The prediction for the 24th activity cycle using these results leads to
W
=102±13.
The lifetime of individual sunspots and pores is analyzed according to
Solar Dynamics Observatory/Helioseismic and Magnetic Imager
(SDO/HMI) data from the period 2010 – 2022. It is found that the ...lifetime of individual sunspots and pores differs from the Gnevyshev–Waldmeier rule formulated for groups of sunspots. The dependence of the lifetime has a different pattern for different types of spots. For pores, the lifetime does not depend on the polarity of the magnetic field and has a logarithmic dependence on the area
T
pr
=
0.24
(
±
0.01
)
+
0.55
(
±
0.14
)
log
(
S
mx
)
. For regular sunspots with a developed penumbra, the dependence on the area has a linear form, but depends on the polarity of the magnetic field. For sunspots with a magnetic field of the leading polarity
T
ld
sp
=
−
0.62
(
±
0.2
)
+
0.036
(
±
0.002
)
S
mx
. For sunspots of trailing polarity
T
tr
sp
=
0.95
(
±
0.1
)
+
0.01
(
±
0.001
)
S
mx
. The decay time and the total lifetime of sunspots is related to the rate of flow in sunspots. The average vertical speed in sunspots decreases with their increasing area. Moreover, the flow rate in the sunspots of the trailing polarity is higher than in the sunspots of the leading polarity. This difference in the velocity explains the difference in the lifetime of the sunspots of the leading and trailing magnetic polarity.
Aims. We investigate the long-term change in coronal large-scale structure at periods of minimum solar activity from 1878 to 2008. Methods. A parameter γ that characterizes the angle between ...high-latitude boundaries of the large coronal streamers at a distance of 2 R⊙ is used to quantify the large-scale coronal structure at minimum solar activity. The comparative analysis of the solar corona during the minimum epochs in activity cycles 12 to 24 shows that the index has been slow and steadily changing during the past 130 years. Results. The maximum value of the index occurred during activity cycles 17 to 19, i.e. around 1950, which was the period when the global magnetic field of the Sun was closest to a dipole configuration. During activity minima close to the years 1900 and 2000, the large-scale coronal structure corresponded to a quadrupole configuration. The reasons for the variations in the solar coronal structure and its relation with long-term variations in the geomagnetic indices and Gleissberg cycle are discussed.
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