Solar Activity

Bumba, V.

doi:10.1017/s0251107x00004491

Cited by 4 publications

(5 citation statements)

References 113 publications

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“…In skimming over Our magnetic and Doppler velocity maps of solar active regions, we noticed that the growth, renewal or decrease of spot-forming activity in active regions is locally related to the singularities of their magnetic field topologies (inclusions of opposite polarities, or just the boundary of both polarities, usually with large magnetic gradients) which develop very rapidly, as we have already demonstrated earlier (Bumba 1988). These magnetic singularities are accompanied by a specific situation in the distribution of line-of-sight motions, demonstrating that also the velocity field is strongly disturbed, or rather very active, in such locations.…”

Section: Introductionsupporting

confidence: 63%

“…As we have demonstrated earlier (Bumba 1988;Bumba et al 1993 and the new magnetic flux develops in the place, where at least opposite polarity magnetic fields malie contact and certain magnetic gradient exists. The magnetic situation can be more complicated, gradients large, the developing activity is then also very large.…”

Section: New Activity Is Related To Both the Magnetic And Motion Fielsupporting

confidence: 51%

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Doppler and proper motions accompanying formation of an additional magnetic flux in the mature solar active region (NOAA 7216)

Bumba

Klvana

Kalman

1996

Astron. Astrophys. Suppl. Ser.

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Abstract. -We document the evolution of an additional magnetic flux in the photosphere of a fully developed sunspot group, we measure longitudinal magnetic field, line-of-sight motions, and proper motions of sunspots in the group during this process. We demonstrate the close correlation of magnetic field, Doppler and proper motion singularities with the area in which additional magnetic flux appears and the new penumbrae and umbrae develop. We discuss the probable reasons for this fact and for the region's weak flare activity. There exist in the group about eight sunspots with the Evershed effect, differing in form, in dependence on the history of development of the spot in which it is observed.

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Section: Introductionsupporting

confidence: 63%

Section: New Activity Is Related To Both the Magnetic And Motion Fielsupporting

confidence: 51%

Doppler and proper motions accompanying formation of an additional magnetic flux in the mature solar active region (NOAA 7216)

Bumba

Klvana

Kalman

1996

Astron. Astrophys. Suppl. Ser.

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“…The persistence of the supergranulation and mesogranulation pattern during the formation of the BMR brings back memories to the observations reported many years ago by Bumba (1963Bumba ( , 1967 and Bumba & Howard (1965). According to these researchers, the growing magnetic fields of BMRs do not break down the pre-existing convectivevelocity field but come from below "seeping" through the network of convection cells.…”

Section: Discussionmentioning

confidence: 74%

The Origin and Early Evolution of a Bipolar Magnetic Region in the Solar Photosphere

Гетлинг

Buchnev

2019

ApJ

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Finding the formation mechanisms for bipolar configurations of strong local magnetic field under control of the relatively weak global magnetic field of the Sun is a key problem of the physics of solar activity. This study is aimed at discriminating whether the magnetic field or fluid motion plays a primary, active role in this process. The very origin and early development stage of Active Region 12548 are investigated based on SDO/HMI observations of 2016 May 20-25. Full-vector magnetic and velocity fields are analyzed in parallel. The leading and trailing magnetic polarities are found to grow asymmetrically in terms of their amplitude, magnetic flux, and the time variation of these quantities. The leading-polarity magnetic element originates as a compact feature against the background of a distributed trailing-polarity field, with an already existing trailing-polarity magnetic element. No signs of strong horizontal magnetic fields are detected between the two magnetic poles. No predominant upflow between their future locations precedes the origin of this bipolar magnetic region (BMR); instead, upflows and downflows are mixed, with some prevalence of downflows. Any signs of a large-scale horizontal divergent flow from the area where the BMR develops are missing; in contrast, a normal supergranulation and mesogranulation pattern is preserved. This scenario of early BMR evolution is in strong contradiction with the expectations based on the model of a rising Ω-shaped loop of a flux tube of strong magnetic field, and an in situ mechanism of magnetic-field amplification and structuring should operate in this case.

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“…The effects of the solar cycle on meteor rates were first studied by Bumba (1949), who reviewed visual meteor records from 1844 to 1943, and found that the rates peaked 5 years after maximum solar activity, and were lowest two years after solar minimum. However, it was not possible to rule out E-mail: margaret.campbell@uwo.ca changes in cloud cover, for example, and he found similar variations in the number of comets seen and meteorite falls and finds, all of which seem unlikely to be affected by atmospheric variations in the same way as meteors.…”

Section: Solar Activity Effects On Meteor Ratesmentioning

confidence: 99%

Solar cycle variation in radar meteor rates

Campbell-Brown

2019

Monthly Notices of the Royal Astronomical Society

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Sixteen years of meteor radar data from the Canadian Meteor Orbit Radar (CMOR) were used to investigate the link between observed meteor rates and both solar and geomagnetic activity. Meteor rates were corrected for transmitter power and receiver noise, and seasonal effects were removed. A strong negative correlation is seen between solar activity, as measured with the 10.7 cm flux, and observed meteor rates. This lends support to the idea that heating in the atmosphere at times of elevated solar activity changes the scale height and therefore the length and maximum brightness of meteors; a larger scale height near solar maximum leads to longer, fainter meteors and therefore lower rates. A weaker negative correlation was observed with geomagnetic activity as measured with the K index; this correlation was still present when solar activity effects were removed. Meteor activity at solar maximum is as much as 30% lower than at solar minimum, strictly due to observing biases; geomagnetic activity usually affects meteor rates by less than 10 percent.

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Solar Activity

Cited by 4 publications

References 113 publications

Doppler and proper motions accompanying formation of an additional magnetic flux in the mature solar active region (NOAA 7216)

Doppler and proper motions accompanying formation of an additional magnetic flux in the mature solar active region (NOAA 7216)

The Origin and Early Evolution of a Bipolar Magnetic Region in the Solar Photosphere

Solar cycle variation in radar meteor rates

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