STUDYING OF ANTI-HALE ACTIVE REGIONS IN THE SOLAR MINIMUM USING A SYNTHETIC CYCLE

During Solar Minimum, the Sun is perceived to be quite inactive with barely any spots emerging on the solar surface. Consequently, we observe a drop in the number of highly energetic events such as solar flares and coronal mass ejections (CMEs), which are often associated with active regions on the photosphere. However, our magnetofrictional simulations during the minimum period suggest that the solar corona could still be significantly dynamic while evolving in response to the large-scale shearing velocities on the solar surface. The non-potential evolution of the corona leads to the accumulation of magnetic free energy and helicity, which is periodically lost through eruptive events. Our study shows that these events can be categorised into two distinct classes. One set of events are caused due to full-scale eruption of low-lying coronal flux ropes and could be associated with occasional filament erupting CMEs observed during Solar Minimum. The other set of events are not driven by destabilisation of low-lying structures but rather by eruption from overlying sheared arcades. These could be linked with streamer blowouts or stealth CMEs. The two classes differ considerably in the amount of magnetic flux and helicity shed through the outer coronal boundary. We additionally investigate how other measurables such as current, open magnetic flux, free energy, coronal holes area, and the horizontal component of the magnetic field on the outer model boundary vary during the two classes of event. This study demonstrates and emphasises the importance and necessity of understanding the dynamics of the coronal magnetic field during Solar Minimum.

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Observations of the Quiet Sun during the Deepest Solar Minimum of the Past Century with Chandrayaan-2 XSM: Sub-A-class Microflares outside Active Regions

The Astrophysical Journal ◽

10.3847/2041-8213/abf0b0 ◽

2021 ◽

Vol 912 (1) ◽

pp. L13

Author(s):

Santosh V. Vadawale ◽

N. P. S. Mithun ◽

Biswajit Mondal ◽

Aveek Sarkar ◽

P. Janardhan ◽

...

Keyword(s):

Solar Minimum ◽

Active Regions ◽

Past Century ◽

Quiet Sun ◽

The Past

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Low-speed solar wind associations with active regions near solar minimum

Advances in Space Research ◽

10.1016/s0273-1177(99)00603-1 ◽

2000 ◽

Vol 25 (9) ◽

pp. 1893-1896 ◽

Cited By ~ 6

Author(s):

M. Kojima ◽

K. Fujiki ◽

K. Hakamada ◽

T. Ohmi ◽

M. Tokumaru ◽

...

Keyword(s):

Solar Wind ◽

Solar Minimum ◽

Active Regions ◽

Low Speed ◽

Speed Solar Wind

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Ephemeral active regions during solar minimum

Solar Physics ◽

10.1007/bf00151118 ◽

1979 ◽

Vol 64 (1) ◽

pp. 93-108 ◽

Cited By ~ 84

Author(s):

Sara F. Martin ◽

Karen L. Harvey

Keyword(s):

Solar Minimum ◽

Active Regions

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The behavior of the spotless active regions during the solar minimum 23-24

Proceedings of the International Astronomical Union ◽

10.1017/s1743921317004069 ◽

2016 ◽

Vol 12 (S328) ◽

pp. 137-139

Author(s):

Alexandre José de Oliveira e Silva ◽

Caius Lucius Selhorst

Keyword(s):

Solar Minimum ◽

Solar Surface ◽

Active Regions ◽

Physical Parameters ◽

Michelson Doppler Imager ◽

Heliospheric Observatory ◽

Doppler Imager

AbstractIn this work, we analysed the physical parameters of the spotless actives regions observed during solar minimum 23 – 24 (2007 – 2010). The study was based on radio maps at 17 GHz obtained by the Nobeyama Radioheliograph (NoRH) and magnetograms provided by the Michelson Doppler Imager (MDI) on board the Solar and Heliospheric Observatory (SOHO). The results shows that the spotless active regions presents the same radio characteristics of a ordinary one, they can live in the solar surface for long periods (>10 days), and also can present small flares.

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Clustering of Fast Coronal Mass Ejections during Solar Cycles 23 and 24 and Implications for CME–CME Interactions

10.5194/egusphere-egu21-3990 ◽

2021 ◽

Author(s):

Jenny Marcela Rodriguez Gomez ◽

Tatiana Podlachikova ◽

Astrid Veronig ◽

Alexander Ruzmaikin ◽

Joan Feynman ◽

...

Keyword(s):

Space Weather ◽

Coronal Mass Ejections ◽

Solar Minimum ◽

Geomagnetic Storms ◽

Active Regions ◽

Solar Cycles ◽

Characteristic Energy ◽

Time Index ◽

Threshold Time ◽

Large Flare

Coronal Mass Ejections (CMEs) and their interplanetary counterparts (ICMEs) are the major sources for strong space weather disturbances. We present a study of statistical properties of fast CMEs (v&#8805;1000 km/s) that occurred during solar cycles 23 and 24. We apply the Max Spectrum and the declustering threshold time methods. The Max Spectrum can detect the predominant clusters, and the declustering threshold time method provides details on the typical clustering properties and timescales. Our analysis shows that during the different phases of solar cycles 23 and 24, fast CMEs preferentially occur as isolated events and in clusters with, on average, two members. However, clusters with more members appear, particularly during the maximum phases of the solar cycles. During different solar cycle phases, the typical declustering timescales of fast CMEs are&#160;&#964;c =28-32 hrs, irrespective of the very different occurrence frequencies of CMEs during a solar minimum and maximum. These findings suggest that &#160;&#964;c &#160; for extreme events may reflect the characteristic energy build-up time for large flare and CME-prolific active regions. Statistically associating the clustering properties of fast CMEs with the disturbance storm time index at Earth suggests that fast CMEs occurring in clusters tend to produce larger geomagnetic storms than isolated fast CMEs. Our results highlight the importance of CME-CME interaction and their impact on Space Weather.

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Source Regions of Coronal Mass Ejections

Symposium - International Astronomical Union ◽

10.1017/s0074180900219542 ◽

2001 ◽

Vol 203 ◽

pp. 362-373

Author(s):

K. P. Dere ◽

P. Subramanian

Keyword(s):

Active Region ◽

Coronal Mass Ejections ◽

Solar Minimum ◽

Active Regions ◽

The Other ◽

Small Scale ◽

Minimum Phase ◽

Michelson Doppler Imager ◽

Doppler Imager ◽

Source Regions

Observations of the solar corona with the LASCO and EIT instruments on SOHO provide an unprecedented opportunity to study coronal mass ejections (CMEs) from their initiation through their evolution out to 30 R⊙. The objective of this study is to gain an understanding of the source regions from which the CMEs emanate. To this end, we have developed a list of 32 CMEs whose source regions are located on the solar disk and are well observed in EIT 195 Å data during the solar minimum phase of January 1996-May 1998. We compare the EIT source regions with photospheric magnetograms from the Michelson Doppler Imager (MDI) instrument on SOHO and the NSO/Kitt Peak Observatory and also with Hα data from various sources. The overall results of our study show that 59% of the CME related transients observed in EIT 195 Å images are associated with active regions without prominences, 22% are associated with eruptions of prominences embedded in active regions and 19% are associated with eruptions of quiescent prominences. We describe 3 especially well observed events, one from each of these 3 categories. These case studies suggest that active region CMEs are associated with active regions with lifetimes between 11-80 days. They are also often associated with small scale emerging or cancelling flux over timescales of 6-7 hours. CMEs associated with active region prominence eruptions, on the other hand, are typically associated with old active regions with lifetimes ~ 6-7 months.

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Synoptic Charts of the Solar Eclipses of 1990 and 1991

International Astronomical Union Colloquium ◽

10.1017/s0252921100025963 ◽

1994 ◽

Vol 144 ◽

pp. 517-521

Author(s):

Z. Mouradian ◽

G. Buchholtz ◽

G. Zlicaric

Keyword(s):

Solar Limb ◽

Active Regions ◽

Solar Eclipses ◽

Coronal Structures

AbstractThe synoptic charts of solar rotations 1831 and 1844 have been drawn up, corresponding to the eclipses of 22 July 1990 and 11 July 1991. These charts contain the active regions and the filaments, and show the position of the solar limb, at the time of the eclipse. They are for use in studying the coronal structures observed during these eclipses. The variation of these structures is given in the table. The last section of the article contains a formula for identifying the structures out of the limb.

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