3a,4,5,6,7,8,8a-Heptahydro-3-(4-chlorophenyl)cyclohept[d]isoxazole

Hathaway, Bruce A.; Mueller, R.

doi:10.3390/m122

Cited by 5 publications

(9 citation statements)

References 2 publications

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“…Both simple and complex regions have the same latitudinal dependence on solar cycle, indicating that they arise from the same reservoir of flux in the solar interior. One might expect complex, monolithic magnetic structures to occur uniformly throughout the solar cycle, but if the majority of complex ARs are produced by the collision of separate systems of emerging flux, more complex ARs should occur during the declining phase of the cycle when the latitudinal width of the activity band decreases (Hathaway 2015). A larger fraction of complex classes should also be seen in stronger cycles where more flux emergence is occurring, but the bias introduced by increasing spatial resolution makes this difficult to support.…”

Section: Discussionmentioning

confidence: 99%

The Magnetic Classification of Solar Active Regions 1992–2015

Jaeggli

Norton

2016

ApJL

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The purpose of this letter is to address a blind-spot in our knowledge of solar active region statistics. To the best of our knowledge there are no published results showing the variation of the Mount Wilson magnetic classifications as a function of solar cycle based on modern observations. We show statistics for all active regions reported in the daily Solar Region Summary from 1992 January 1 to 2015 December 31. We find that the α and β class active regions (including all sub-groups e.g. βγ, βδ) make up fractions of approximately 20% and 80% of the sample respectively. This fraction is relatively constant during high levels of activity, however, an increase in the α fraction to about 35% and and a decrease in the β fraction to about 65% can be seen near each solar minimum and is statistically significant at the 2-σ level. Over 30% of all active regions observed during the years of solar maxima were appended with the classifications γ and/or δ, while these classifications account for only a fraction of a percent during the years near the solar minima. This variation in the active region types indicates that the formation of complex active regions may be due to the pileup of frequent emergence of magnetic flux during solar maximum, rather than the emergence of complex, monolithic flux structures.

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Section: Discussionmentioning

confidence: 99%

The Magnetic Classification of Solar Active Regions 1992–2015

Jaeggli

Norton

2016

ApJL

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“…Automatic detection of PEs from these images has already been reported (Gopalswamy et al 2015a). We use the Synoptic Optical Long-term Investigations of the Sun (SOLIS) magnetic data to study the poleward surges of unipolar flux (Hathaway 2015).…”

Section: Observationsmentioning

confidence: 99%

Unusual Polar Conditions in Solar Cycle 24 and Their Implications for Cycle 25

Gopalswamy

Yashiro

Akiyama

2016

ApJL

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We report on the prolonged solar-maximum conditions until late 2015 at the north-polar region of the Sun indicated by the occurrence of high-latitude prominence eruptions (PEs) and microwave brightness temperature close to the quiet-Sun level. These two aspects of solar activity indicate that the polarity reversal was completed by mid-2014 in the south and late 2015 in the north. The microwave brightness in the south-polar region has increased to a level exceeding the level of the Cycle 23/24 minimum, but just started to increase in the north. The northsouth asymmetry in the polarity reversal has switched from that in Cycle 23. These observations lead us to the hypothesis that the onset of Cycle 25 in the northern hemisphere is likely to be delayed with respect to that in the southern hemisphere. We find that the unusual condition in the north is a direct consequence of the arrival of poleward surges of opposite polarity from the active region belt. We also find that multiple rush-to-the-pole episodes were indicated by the PE locations that lined up at the boundary between opposite-polarity surges. The high-latitude PEs occurred in the boundary between the incumbent polar flux and the insurgent flux of opposite polarity.

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“…The probable reason for this synchronization is that random forcing of the quadrupolar dynamo mode is modulated by oscillations of the dipolar toroidal field. The phase locking may be the explanation for the observation that "two hemispheres never get very far out of phase with each other" (Hathaway 2015).…”

Section: Phase Lockingmentioning

confidence: 99%

Dynamo Model for Nort-South Asymmetry of Solar Activity

Kitchatinov¹,

Observatory²,

Nepomnyashchikh³

2019

Proceedings of the 23rd All-Russia Conference on Solar and Solar-Terrestrial Physics

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Observations reveal a relatively small but statistically significant North-South (NS) asymmetry in sunspot activity varying on a time scale of several solar cycles. This paper proposes a dynamo model for the phenomenon of long-term NS asymmetry. The model separates dynamo equations for magnetic fields of dipolar and quadrupolar equatorial parity. The NS asymmetry results from the superposition of dipolar and quadrupolar fields. Model computations confirm the formerly proposed excitation of the quadrupolar dynamo mode by a dominant dipolar mode mediated by the equator-symmetric fluctuations in the α-effect as a mechanism for the long-term NS asymmetry. An analytically solvable example of oscillations excited by short-term random forcing is given to justify the numerical result of NS asymmetry coherent on a time scale of several (about 6 in the present model) solar cycles resulting from random variations in the α-effect on a time scale of one solar rotation. The model computations show the phase locking phenomenon of dipolar and quadrupolar fields oscillating predominantly in phase (northern type asymmetry) or in antiphase (southern type asymmetry) with relatively short irregular transitions between these two states. Large asymmetry in the simulated Grand minima is found and explained by weak magnetic quenching of the α-effect during the minima. The possibility of polar field asymmetry in activity minima as a precursor of sunspot asymmetry in the following activity cycles is discussed based on the dynamo model and observations.

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3a,4,5,6,7,8,8a-Heptahydro-3-(4-chlorophenyl)cyclohept[d]isoxazole

Abstract: To a solution of 4-chlorobenzaldehyde oxime ( 0.40g) in CH2Cl2 (10 mL) in a large test-tube were added 1.0 mL of cycloheptene and 3 drops of triethylamine.[...]

Cited by 5 publications

References 2 publications

The Magnetic Classification of Solar Active Regions 1992–2015

The Magnetic Classification of Solar Active Regions 1992–2015

Unusual Polar Conditions in Solar Cycle 24 and Their Implications for Cycle 25

Dynamo Model for Nort-South Asymmetry of Solar Activity

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