Rearrangements of Open Magnetic Flux and Formation of Polar Coronal Holes in Cycle 24

Golubeva, E. M.; Мордвинов, А. В.

doi:10.1007/s11207-017-1200-6

Cited by 12 publications

(8 citation statements)

References 39 publications

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“…For the period for which we have processed CH data, from just before the maximum of SC 21 (1980) to the start of SC 24 (2009), this demonstrates well how the dual cells of opposite-polarity in the higher latitudes of each hemisphere track each other through each SC, and how consistent the offset is between the higher-latitude open and closed regions and the lower latitude closed regions (sunspots and plage). These largescale rearrangements of the open flux in unipolar areas and the formation of the polar CHs in SC 23 and 24 have recently been studied by Golbeva and Mordvinov (2017). These large-scale motions are somehow tied to the internal fluid dynamics of the Sun, and must be accounted for in dynamo models.…”

Section: Solar-cycle Evolution Of Closed and Open Magnetic Structuresmentioning

confidence: 99%

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

Webb

Gibson

Hewins

et al. 2018

Front. Astron. Space Sci.

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The McIntosh Archive consists of a set of hand-drawn solar Carrington maps created by Patrick McIntosh from 1964 to 2009. McIntosh used mainly Hα, He-I 10830 Å and photospheric magnetic measurements from both ground-based and NASA satellite observations. With these he traced polarity inversion lines (PILs), filaments, sunspots and plage and, later, coronal holes over a ∼45-year period. This yielded a unique record of synoptic maps of features associated with the large-scale solar magnetic field over four complete solar cycles. We first discuss how these and similar maps have been used in the past to investigate long-term solar variability. Then we describe our work in preserving and digitizing this archive, developing a digital, searchable format, and creating a website and an archival repository at NOAA's National Centers for Environmental Information (NCEI). Next we show examples of how the data base can be utilized for scientific applications. Finally, we present some preliminary results on the solar-cycle evolution of the solar magnetic field, including the polar field reversal process, the evolution of active longitudes, and the role of differential solar rotation.

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Section: Solar-cycle Evolution Of Closed and Open Magnetic Structuresmentioning

confidence: 99%

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

Webb

Gibson

Hewins

et al. 2018

Front. Astron. Space Sci.

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“…The SOHO/EIT instrument (Delaboudinière et al, 1995) takes images of the Sun in four passbands that are centered on intense emission lines of the solar EUV spectrum. He II (304 Å), Fe XI/Fe X (171 Å), Fe XII (195 Å), and Fe XV (284 Å) lines provide temperature diagnostics in the range from 6 × 10 4 K to 3 × 10 6 K. These different wavelengths represent solar layers at different altitudes.…”

Section: Previous Euv Synoptic Map Datasetsmentioning

confidence: 99%

“…Synoptic maps provide a convenient way to display the evolution and/or distribution of various physical quantities and features on the entire solar surface. For example, synoptic maps have been used to study coronal holes (CH) (Karna et al, 2015;Golubeva and Mordvinov, 2017;Hamada et al, 2018), photospheric and coronal magnetic fields (Virtanen and Mursula, 2016), and long-lived active regions (ARs). Solar synoptic maps can also be used to study the nonuniform structure of the EUV corona in both longitude and latitude, reflecting the nonuniform distribution of the large-scale magnetic field (Benevolenskaya, Kosovichev, and Scherrer, 2001).…”

Section: Introductionmentioning

confidence: 99%

New Homogeneous Dataset of Solar EUV Synoptic Maps from SOHO/EIT and SDO/AIA

2019

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Synoptic maps of solar EUV intensities have been constructed for many decades in order to display the distribution of the different EUV emissions across the solar surface, with each map representing one Carrington rotation (i.e. one rotation of the Sun). This article presents a new solar EUV synoptic map dataset based on full-disk images from the Solar and Heliospheric Observatory/Extreme Ultraviolet Imaging Telescope (SOHO/EIT) and Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA). In order to remove the significant and complicated drift of EIT and AIA EUV intensities due to sensor degradation, we construct the synoptic maps in standardized intensity scale. We describe a method of homogenizing the SOHO/EIT maps with SDO/AIA maps by transforming the EIT intensity histograms to AIA levels. The new maps cover the years from 1996 to 2018 with 307 SOHO/EIT and 116 SDO/AIA synoptic maps, respectively. These maps provide a systematic and homogeneous view of the entire solar surface in four EUV wavelengths, and are well suited, e.g., for studying long-term coronal hole evolution.

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“…Polar fields of either hemisphere reversed near to the maximum of the solar cycle 23. Growth of the reversed field was however prohibited by poleward surges of fields of old polarity that occurred in both hemispheres (Mordvinov et al 2015;Golubeva & Mordvinov 2017). The surges originated from active regions with non-Joy tilts.…”

Section: Why Is the Current Activity Cycle Low?mentioning

confidence: 99%

Modelling variability of solar activity cycles

Kitchatinov

Мордвинов

Nepomnyashchikh

2018

A&A

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Context. Solar activity cycles vary in amplitude and duration. The variations can be at least partly explained by fluctuations in dynamo parameters. Aims. We want to restrict uncertainty in fluctuating dynamo parameters and find out which properties of the fluctuations control the amplitudes of the magnetic field and energy in variable dynamo cycles. Methods. A flux-transport model for the solar dynamo with fluctuations of the Babcock-Leighton type α-effect was applied to generate statistics of magnetic cycles for our purposes. The statistics were compared with data on solar cycle periods to restrict the correlation time of dynamo fluctuations. Results. A characteristic time of fluctuations in the α-effect is estimated to be close to the solar rotation period. The fluctuations produce asymmetry between the times of rise and descent of dynamo cycles, the rise time being on average shorter. The affect of the fluctuations on cycle amplitudes depends on the phase of the cycle in which the fluctuations occur. Negative fluctuations (decrease in α) in the rise phase delay decay of poloidal field and increase the cycle amplitude in toroidal field and magnetic energy. Negative fluctuation in the decline phase reduces the polar field at the end of a cycle and the amplitude of the next cycle. The low amplitude of the 24th solar cycle compared to the preceding 23rd cycle can be explained by this effect. Positive fluctuations in the descent phase enhance the magnetic energy of the next cycle by increasing the seed poloidal field for the next cycle. The statistics of the computed energies of the cycles suggest that superflares of ≥ 10 34 erg are not possible on the Sun.

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Rearrangements of Open Magnetic Flux and Formation of Polar Coronal Holes in Cycle 24

Cited by 12 publications

References 39 publications

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

Global Solar Magnetic Field Evolution Over 4 Solar Cycles: Use of the McIntosh Archive

New Homogeneous Dataset of Solar EUV Synoptic Maps from SOHO/EIT and SDO/AIA

Modelling variability of solar activity cycles

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