STATISTICAL COMPARISON BETWEEN PORES AND SUNSPOTS BY USING<i>SDO</i>/HMI

Cho, Kyung-Suk; Cho, K.-S.; Bong, Su-Chan; Lim, Eun-Kyung; Kim, R.-S.; Choi, Seonghwan; Kim, Y.-H.; Yurchyshyn, Vasyl

doi:10.1088/0004-637x/811/1/49

Cited by 23 publications

(16 citation statements)

References 51 publications

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“…They related this to the changes in the relative fraction of small and large sunspots in each cycle (i.e., larger the fraction of large sunspots in selected solar cycle -steeper the H vs. S dependence for this cycle). (Kuklin, 1973(Kuklin, , 1980Nagovitsyn et al, 2012;Cho et al, 2015;Muñoz-Jaramillo et al, 2015;McClintock and Norton, 2016;Kostyuchenko, 2017;Nagovitsyn et al, 2018;Tlatov et al, 2019, and references therein). Nagovitsyn et al (2012) suggested that the two populations could represent the action of two spatially separated dynamos: one operating at the base/bulk of the convection zone, and the other -near the surface (see also, Clette and Lefèvre, 2012).…”

Section: Magnetic Flux Vs Areamentioning

confidence: 99%

Long-term studies of photospheric magnetic fields on the Sun

Pevtsov

Bertello

Nagovitsyn

et al. 2021

J. Space Weather Space Clim.

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We briefly review the history of observations of magnetic fields on the Sun, and describe early magnetograps for full disk measurements. Changes in instruments and detectors, the cohort of observers, the knowledge base etc may result in non-uniformity of the long-term synoptic datasets. Still, such data are critical for detecting and understanding the long-term trends in solar activity. We demonstrate the value of historical data using studies of active region tilt (Joy's law) and the evolution of polar field and its reversal. Using the longest dataset of sunspot field strength measurements from Mount Wilson Observatory (1917-present) supplemented by shorter datasets from Pulkovo (1956--1997) and Crimean (1956--present) observatories we demonstrate that the magnetic properties of sunspots did not change over the last hundred years. We also show that the relationship between the sunspot area and its magnetic flux can be used to extend the studies of magnetic field in sunspots to periods with no direct magnetic field measurements. Finally, we show how more recent full disk observations of the vector magnetic field can be used to study the long-term (solar cycle) variations in magnetic helicity on the Sun.

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Section: Magnetic Flux Vs Areamentioning

confidence: 99%

Long-term studies of photospheric magnetic fields on the Sun

Pevtsov

Bertello

Nagovitsyn

et al. 2021

J. Space Weather Space Clim.

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“…They are smaller than the traditional sunspots. However, their magnetic field strength on the photospheric level can vary between 600 G to 1700 G, which approximately corresponds to the sunspot magnetic field strength (Sütterlin, Schröter, and Muglach, 1996;Giordano et al, 2008;Cho et al, 2015). Solar faculae are similar bright and small atmospheric features.…”

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confidence: 99%

Identifying 8 mm Radio Brightenings During the Solar Activity Minimum

2020

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Strong solar radio brightenings have been extensively studied in the past, and their correlation to the sunspots and active regions are already well known. But even when the Sun is ostensibly quiet, there is practically always some activity that can be detected in the radio domain. In this article we investigate these semi-active features at 8 mm using the radio telescope at Aalto University Metsähovi Radio Observatory. The observations were made between May and September 2019 when the solar activity was very low, and for our detailed study we chose dates when no active regions were identified on the solar surface by the National Oceanic and Atmospheric Administration. The brightness temperature of these radio regions during this quiescent period of solar activity is at maximum approximately 250 K above the quiet-Sun level. We compared our millimeter data with data taken in extreme ultraviolet, and we found that these weak radio brightenings are mostly related to coronal hole features and magnetic bright points. We also found that there are two different categories of bright points: those with and without flux tube structure. The formation of the weak radio brightenings is comparable to the stronger radio brightenings: the rising fluxes from the weak photospheric features can be detected as a radio source. Keywords Chromosphere, quiet • Solar cycle, observations 1. Introduction Even when the Sun is ostensibly quiet and there are no visible, classified active regions (ARs) on the solar disk, there is often some activity, such as coronal holes and magnetic bright points. Also solar radio observations practically always detect some activity. During B J. Kallunki

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“…Hagenaar et al 2003). Therefore pores appear both near the sunspots and in isolation (Keil et al 1999), even though it seems that in the space of fundamental parameters, pores and sunspots depict distinct groups (Cho et al 2015) so one cannot simply say that a pore is a "small sunspot". Yet, it is believed that pores are manifestations of rising flux tubes in the same way as sunspots are.…”

Section: Purpose Of the Present Work And Methodologymentioning

confidence: 99%

Polar cap magnetic field reversals during solar grand minima: could pores play a role?

Švanda

Brun²,

Roudier

et al. 2016

A&A

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We study the magnetic flux carried by pores located outside active regions with sunspots and investigate their possible contribution to the reversal of the global magnetic field of the Sun. We find that they contain a total flux of comparable amplitude to the total magnetic flux contained in polar caps. The pores located at distances of 40-100 Mm from the closest active region systematically have the correct polarity of the magnetic field to contribute to the polar cap reversal. These pores can be found predominantly in bipolar magnetic regions. We propose that during grand minima of solar activity, such a systematic polarity trend, which is akin to a weak magnetic (Babcock-Leighton-like) source term, could still be operating but was missed by the contemporary observers because of the limited resolving power of their telescopes.

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STATISTICAL COMPARISON BETWEEN PORES AND SUNSPOTS BY USINGSDO/HMI

Cited by 23 publications

References 51 publications

Long-term studies of photospheric magnetic fields on the Sun

Long-term studies of photospheric magnetic fields on the Sun

Identifying 8 mm Radio Brightenings During the Solar Activity Minimum

Polar cap magnetic field reversals during solar grand minima: could pores play a role?

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