Solar cycle variation of simple and complex active regions

2020 ◽  
Author(s):  
Shabnam Nikbakhsh ◽  
Eija Tanskanen ◽  
Maarit Käpylä ◽  
Thomas Hackman
Keyword(s):  
Solar Cycle ◽  
Space Weather ◽  
Active Regions ◽  
Weather Forecast ◽  
Solar Cycle Variation ◽  
Magnetic Structures ◽  
Latitudinal Band ◽  
Second Peak ◽  
Northern And Southern Hemispheres

<p>Solar active regions (ARs) emerge on the Sun’s photosphere and they frequently produce flares and coronal mass ejections which are among major space weather drivers. Therefore, studying ARs can improve space weather forecast.</p><p>The Mount Wilson Classification has been used since 1919 in order to group groups ARs according to their magnetic structures. In this study, we investigated the magnetic classification of 4797 ARs and their cyclic variation, using our daily approach for the period of January 1996 to December 2018.</p><p>We show that the monthly number of the simple ARs (SARs) attained their maximum during first peak of the solar cycle, whereas more complex ARs (CARs) reached their maximum roughly two years later, during the second peak of the cycle. We also demonstrate that the total abundance of CARs is very similar during a period of four years around their maximum number. We also studied the latitudinal distributions of SARs and CAR in northern and southern solar hemispheres and show that the independent of the complexity type, the distributions are the same in both hemispheres.</p><p>Furthermore, we investigated the earlier claim of increase in number of CARs due to the decrease in ARs latitudinal band. Here we show that, contrary to this claim, CARs attained their maximum number before the latitudinal band started to decrease in both northern and southern hemispheres.</p>

scholarly journals The design of solar synoptic chart for space weather forecast

2015 ◽  
Vol 11 (S320) ◽  
pp. 324-329 ◽  
Author(s):  
Qiao Song ◽  
Jing-Song Wang ◽  
Xue-Shang Feng ◽  
Xiao-Xin Zhang
Keyword(s):  
Public Education ◽  
Space Weather ◽  
Coronal Holes ◽  
Active Regions ◽  
Weather Forecast ◽  
The Sun ◽  
The Public ◽  
The Past ◽  
The Earth ◽  
Synoptic Chart

AbstractThe Sun drives most events of space weather in the vicinity of the Earth. Because the activities of the Sun are complicated, a visualized chart with key objects of solar activities is needed for space weather forecast. This work investigates the key objects in research during the past forty years and surveys a variety of solar observational data. We design the solar synoptic chart (SSC) that covers the key objects of solar activities, i.e., active regions, coronal holes, filaments/prominences, flares and coronal mass ejections, and synthesizes images from different heights and temperatures of solar atmosphere. The SSC is used to analyze the condition of the Sun in March 2012 and October 2014 as examples. The result shows that the SSC is timely, comprehensive, concise and easy to understand. It has the potentiality for space weather forecast and can help in improving the public education.

scholarly journals Carrington Longitudinal and Solar Cycle Distribution of the Super Active Regions From 1976 to 2018

2021 ◽  
Author(s):  
MIng-Xian Zhao ◽  
Guiming Le ◽  
Yonghua Liu ◽  
Tian Mao
Keyword(s):  
Solar Cycle ◽  
Space Weather ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Active Regions ◽  
Ground Level ◽  
Weather Events ◽  
Flare Index ◽  
Statistical Results ◽  
Extreme Space Weather Events

Abstract We studied the Carrington longitudinal and solar cycle distribution of the super active regions (SARs) from 1976to 2018. There were 51 SARs during this period. We divided the SARs into SARs1 and SARs2. SARs1 refers tothe SARs that produced extreme space weather events including ≥X5.0 flares, ground level events (GLEs) andsuper geomagnetic storms (SGSs: Dst≤ −250 nT), while SARs2 did not produce extreme space weather events.The total number of SARs1 and SARs2 are 32 and 19, respectively. The statistical results show that 34.4%, 65.6%and 78.1% of the SARs1 appeared in the ascending phase, descending phase and in the period from two yearsbefore to the three years after the solar maximum, respectively, while 52.6%, 47.4% and 100% of the SARs2appeared in the ascending phase, descending phase and in the period from two years before to the three years aftersolar maximum, respectively. The Carrington longitude distribution of the SARs1 shows that SARs1 in thelongitudinal scope of [0,150°] produced ≥X5.0 flares and GLEs, while only the SARs1 in the longitude range of[150°,360°] not only produced ≥X5.0 flares and GLEs, but also produced SGSs. The total number of SARsduring a SC has a good correlation with the SC size. However, the largest flare index of a SAR within a SC has apoor correlation with the SC size, implying that the number of SARs in a weak SC will be small. However, aweak SC may have a SAR that can produce very strong solar flare activities.

scholarly journals Magnetic Helicity as a Predictor of the Solar Cycle

2017 ◽  
Vol 13 (S335) ◽  
pp. 20-22
Author(s):  
G. Hawkes ◽  
M. A. Berger
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Differential Rotation ◽  
Strong Predictor ◽  
Active Regions ◽  
Magnetic Helicity ◽  
Poloidal Field ◽  
Northern And Southern Hemispheres

AbstractIt is known that the poloidal field is at its maximum during solar minima, and that the behaviour during this time acts as a strong predictor of the strength of the following solar cycle. This relationship relies on the action of differential rotation (the Omega effect) on the poloidal field, which generates the toroidal flux observed in sunspots and active regions. We measure the helicity flux into both the northern and southern hemispheres using a model that takes account of the omega effect, which we find offers a strong quantification of the above relationship. We find that said helicity flux offers a strong prediction of solar activity up to 5 years in advance of the next solar cycle.

scholarly journals Solar cycle variation of helicity characteristics indicated by SP/Hinode

2012 ◽  
Vol 8 (S294) ◽  
pp. 149-150
Author(s):  
Juan Hao ◽  
Mei Zhang
Keyword(s):  
Solar Cycle ◽  
Active Regions ◽  
Field Measurements ◽  
Second Phase ◽  
Solar Cycle Variation ◽  
Cycle Variation ◽  
Phase Cycle ◽  
Solar Cycle 24 ◽  
Cycle 24 ◽  
Weak Fields

AbstractHelicity characteristics in active regions (ARs) are studied, using so far the most accurate vector magnetic field measurements obtained with SP/Hinode. Our sample includes all ARs observed by SP/Hinode, up to June 2012. The sample is divided into three sub-samples: Cycle 23 (from 2006.11 to 2008.06), Cycle 24a (from 2008.10 to 2010.09) and Cycle 24b (from 2010.10 to 2012.06). We confirm our previous findings that the usual hemispheric helicity sign rule is not obeyed in the descending phase of solar cycle 23 and is obeyed in the ascending phase of solar cycle 24. And we find that the second phase of the solar cycle 24 (Cycle 24b) shows an even stronger evidence of the usual hemispheric helicity sign rule than its first phase (Cycle 24a). It is also found that our previous finding that the strong and weak fields possess the opposite helicity signs is not followed in Cycle 24b, whereas it is weakly followed in Cycle 24a and strongly followed in the descending phase of Cycle 23. This means that this rule also has a solar cycle variation, in addition to the solar cycle variation of the usual hemispheric helicity sign rule, and there is a roughly 2-years time delay between the two.

scholarly journals Solar Cycle

2020 ◽  
Author(s):  
Lidia van Driel-Gesztelyi ◽  
Mathew J. Owens
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Solar Cycle ◽  
Space Weather ◽  
Large Scale ◽  
Solar Interior ◽  
Polar Field ◽  
Interstellar Space ◽  
Dynamo Action ◽  
Solar Cycle Variation

The Sun’s magnetic field drives the solar wind and produces space weather. It also acts as the prototype for an understanding of other stars and their planetary environments. Plasma motions in the solar interior provide the dynamo action that generates the solar magnetic field. At the solar surface, this is evident as an approximately 11-year cycle in the number and position of visible sunspots. This solar cycle is manifest in virtually all observable solar parameters, from the occurrence of the smallest detected magnetic features on the Sun to the size of the bubble in interstellar space that is carved out by the solar wind. Moderate to severe space-weather effects show a strong solar cycle variation. However, it is a matter of debate whether extreme space-weather follows from the 11-year cycle. Each 11-year solar cycle is actually only half of a solar magnetic “Hale” cycle, with the configuration of the Sun’s large-scale magnetic field taking approximately 22 years to repeat. At the start of a new solar cycle, sunspots emerge at mid-latitude regions with an orientation that opposes the dominant large-scale field, leading to an erosion of the polar fields. As the cycle progresses, sunspots emerge at lower latitudes. Around solar maximum, the polar field polarity reverses, but the sunspot orientation remains the same, leading to a build-up of polar field strength that peaks at the start of the next cycle. Similar magnetic cyclicity has recently been inferred at other stars.

The Hemispheric Sign Rule of Current Helicity during the Rising Phase of Cycle 23

2000 ◽  
Vol 179 ◽  
pp. 303-306
Author(s):  
S. D. Bao ◽  
G. X. Ai ◽  
H. Q. Zhang
Keyword(s):  
Solar Cycle ◽  
Southern Hemisphere ◽  
Northern Hemisphere ◽  
Active Regions ◽  
Hemispheric Preference ◽  
Current Helicity

AbstractWe compute the signs of two different current helicity parameters (i.e., αbestandHc) for 87 active regions during the rise of cycle 23. The results indicate that 59% of the active regions in the northern hemisphere have negative αbestand 65% in the southern hemisphere have positive. This is consistent with that of the cycle 22. However, the helicity parameterHcshows a weaker opposite hemispheric preference in the new solar cycle. Possible reasons are discussed.

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