Large-scale patterns and ‘active longitudes’

Обридко, В. Н.

doi:10.1017/s1743921309992699

“…A particularly important question is how long they persist. There are estimates of lifetimes ranging from several solar rotations up to as many as 10 sunspot cycles (Benevolenskaya et al, 1999;Bumba et al, 2000;Usoskin et al, 2007;Obridko, 2009;Hathaway, 2015;Mandal et al, 2017) as well as evidence of both uniform and differential rotation of active longitudes (Berdyugina et al, 2006;Plyusnina, 2010). Families of MHD Rossby waves in the solar tachocline have strong potential for producing such persistence of longitude-dependent features.…”

Section: Progress In Forecasting Space Weather By Data Assimilationmentioning

confidence: 99%

Space Weather Challenge and Forecasting Implications of Rossby Waves

Dikpati

¹

,

McIntosh

²

2020

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Rossby waves arise in thin layers within fluid regions of stars and planets. These global wave‐like patterns occur due to the variation in Coriolis forces with latitude. In the past several years observational evidence has indicated that there are also Rossby waves in the Sun. Although Rossby waves have been detected in the Sun's photosphere and corona, they most likely originate in the solar tachocline, the sharp shear layer at the base of the solar convection zone, where the differential rotation driven by convection transitions to the solidly rotating radiative interior. These waves differ from their Earth's counterparts by being strongly modified by toroidal magnetic fields in the solar tachocline. Recent simulations of magnetohydrodynamics of tachocline Rossby waves and magnetic fields are demonstrated to produce strong “tachocline nonlinear oscillations,” which have periods similar to those observed in the solar atmosphere—enhanced periods of solar activity, or “seasons”—occurring at intervals between six months and two years. These seasonal/subseasonal bursts produce the strongest eruptive space weather events. Thus, a key to forecasting the timing, amplitude, and location of future activity bursts, and hence space weather events, could lie in our ability to forecast the phase and amplitude of Rossby waves and associated tachocline nonlinear oscillations. Accurately forecasting the properties of solar Rossby waves and their impact on space weather will require linking surface activity observations to the magnetohydrodynamics of tachocline Rossby waves, using modern data assimilation techniques. Both short‐term (hours to days) and long‐term (decadal to millennial) forecasts of space weather and climate are now being made. We highlight in this article the potential of solar Rossby waves for forecasting space weather on intermediate time scales, of several weeks to months up to a few years ahead.

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Active longitudes and the structure of the large-scale magnetic field at solar minimum

Grigoryev,

Ermakova

2023

Solar-Terrestrial Physics

0

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We have studied deep minima of 11-year solar activity cycles 13–14, 14–15, 22–23, 23–24, 24–25, using the RGO and USAF/NOAA sunspot group catalogs. All of them have a large number of spotless days. Nonetheless, active longitudes as preferred zones, where sunspots occur, appear at this solar cycle phase. Analysis of synoptic maps and WSO daily magnetograms reflecting the structure of a weak large-scale field shows a non-axisymmetric component of the solar magnetic field. At solar minimum in the structure of the large-scale magnetic field, there are regions of the magnetic field of positive and negative polarity elongated along the meridian and crossing the equator. The most pronounced of them are located in the zone of active longitudes and are often connected with the polar magnetic fields. We discuss the possible nature of the meridional structures of the large-scale field during solar minimum. This might be due to giant convection cells with a banana cell structure.

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Active longitudes and the structure of the large-scale magnetic field at solar minimum

Grigoryev,

Ermakova

2023

Solnechno-Zemnaya Fizika

0

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We have studied deep minima of 11-year solar activity cycles 13–14, 14–15, 22–23, 23–24, 24–25, using the RGO and USAF/NOAA sunspot group catalogs. All of them have a large number of spotless days. Nonetheless, active longitudes as preferred zones, where sunspots occur, appear at this solar cycle phase. Analysis of synoptic maps and WSO daily magnetograms reflecting the structure of a weak large-scale field shows a non-axisymmetric component of the solar magnetic field. At solar minimum in the structure of the large-scale magnetic field, there are regions of the magnetic field of positive and negative polarity elongated along the meridian and crossing the equator. The most pronounced of them are located in the zone of active longitudes and are often connected with the polar magnetic fields. We discuss the possible nature of the meridional structures of the large-scale field during solar minimum. This might be due to giant convection cells with a banana cell structure.

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Large-scale patterns and ‘active longitudes’

Cited by 3 publications

References 34 publications

Space Weather Challenge and Forecasting Implications of Rossby Waves

Space Weather Challenge and Forecasting Implications of Rossby Waves

Active longitudes and the structure of the large-scale magnetic field at solar minimum

Active longitudes and the structure of the large-scale magnetic field at solar minimum

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