Hemispheric asymmetry of sunspot area in solar cycle 23 and rising phase of solar cycle 24: Comparison of three data sets

The characteristics of CMEs we studied are angular width, linear speed, and acceleration for all categories of CMEs such as narrow (W ≤20°), intermediate (20°< W<200°), wide (W ≥ 200°) and linear speed <500 km/s during the descending phase of solar cycle 23 and 24 and compared them. We have found that there are 1951 narrow CMEs during solar cycle 23 that is 1.9 times greater than in solar cycle 24 (1047). On the other side, the number of intermediate CMEs during solar cycle 24 (1571) is 1.14 times more than solar cycle 23 (1162). We observed no noticeable difference between the number of wide CMEs of solar cycle 23 (29) and 24 (36). The angular width of CMEs during the descending phase of solar cycle 23 and solar cycle 24, predominately distributed around 100-600. The fascinating result is that the angular width distributions for the descending phase of solar cycles are approximately identical. On comparing the results of linear speed of both solar cycle, we can say that, (i) 93.7% (1729) and 87.7% (908) of narrow CMEs, (ii) 97% (1328) and 94% (1479) of intermediate CMEs and (iii) 44% (13) and 42% (15) of wide CMEs have speed of <500 km s-1, respectively. Mostly the fractions of narrow and intermediate CMEs decline sharply at the speeds greater than 500 km s-1. The maximum speed observed during the 23rd cycle is 1994 km/s (wide CME) and the 24th cycle is 3163 km/s (wide CME) respectively. It was noticed that the speed of the 24th solar cycle CME is higher than the 23rd solar cycle CME. The major fraction of CMEs has acceleration in the range of -20 to 20 km s-2, all types of CMEs. The narrow and intermediate CMEs mostly show acceleration while wide CMEs show deceleration.

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Solar Flare Build-Up and Release

Solar Physics ◽

10.1007/s11207-020-01698-w ◽

2020 ◽

Vol 295 (10) ◽

Author(s):

Hugh S. Hudson

Keyword(s):

Magnetic Field ◽

Solar Cycle ◽

Waiting Times ◽

Active Regions ◽

Coronal Magnetic Field ◽

Sunspot Area ◽

Observational Evidence ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Event Magnitude

Abstract Flares and coronal mass ejections should follow a pattern of build-up and release, with the build-up phase understood as the gradual addition of stress to the coronal magnetic field. Recently Hudson (Mon. Not. Roy. Astron. Soc.491, 4435, 2020) presented observational evidence for this pattern in two isolated active regions from 1997 and 2006, finding a correlation between the waiting time after the event, and the event magnitude. In this article we systematically search for related evidence in the largest 14 active regions of Solar Cycle 24, chosen as those with peak sunspot area exceeding 1000 millionths of the solar hemisphere (MSH). The smallest of these regions, NOAA 12673, produced the exceptional flares SOL2017-09-06 and SOL2017-09-10. None of these regions showed significant correlations of waiting times and flare magnitudes, although two hinted at such an interval-size relationship. Correlations thus appear to be non-existent or intermittent, depending on presently unknown conditions.

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Ionospheric effects of two solar flares in the maximum of solar cycle 23 and in the minimum of solar cycle 24

Solar-Terrestrial Physics ◽

10.12737/stp-52201911 ◽

2019 ◽

Vol 5 (2) ◽

pp. 76-80

Author(s):

Владимир Смирнов ◽

Vladimir Smirnov ◽

Елена Смирнова ◽

Elena Smirnova

Keyword(s):

Solar Cycle ◽

Solar Flares ◽

Total Duration ◽

Rate Of Change ◽

Satellite Systems ◽

Solar Cycle 23 ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Using Data ◽

Total Electronic Content

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

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Ionospheric effects of two solar flares in the maximum of solar cycle 23 and in the minimum of solar cycle 24

Solnechno-Zemnaya Fizika ◽

10.12737/szf-52201911 ◽

2019 ◽

Vol 5 (2) ◽

pp. 82-88

Author(s):

Владимир Смирнов ◽

Vladimir Smirnov ◽

Елена Смирнова ◽

Elena Smirnova

Keyword(s):

Solar Cycle ◽

Solar Flares ◽

Total Duration ◽

Rate Of Change ◽

Satellite Systems ◽

Solar Cycle 23 ◽

Solar Cycle 24 ◽

Cycle 24 ◽

Using Data ◽

Total Electronic Content

Using data from the GPS and GLONASS navigation satellite systems, we analyze the responses of the mid-latitude ionosphere to the extreme solar flares that occurred at the maximum of solar cycle 23 (October 28, 2003) and at the minimum of solar cycle 24 (September 6, 2017) during the same season at close solar zenith angles. To obtain the response, we use the rate of change of the total electronic content, which is practically independent of characteristics of equipment and is determined only by parameters of a propagation medium (the ionosphere in our case). The ionospheric response is shown to be almost independent of the total duration of the flare. In both cases, the duration of the main response at a level of 0.5 is about 1.5–2 min, whereas the total duration of the response is about 10 min and fairly independent of solar flare importance.

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Long-Term Cosmic Ray Variability and the CME-Index

Advances in Astronomy ◽

10.1155/2012/607172 ◽

2012 ◽

Vol 2012 ◽

pp. 1-8 ◽

Cited By ~ 5

Author(s):

Helen Mavromichalaki ◽

Evangelos Paouris

Keyword(s):

Standard Deviation ◽

Solar Cycle ◽

Cosmic Ray ◽

Heliospheric Current Sheet ◽

Angular Width ◽

Cosmic Ray Intensity ◽

Cosmic Ray Modulation ◽

Solar Cycle 23 ◽

Solar Cycle 24 ◽

Cycle 24

The cosmic ray modulation in relation to solar activity indices and heliospheric parameters during the period January 1996–October 2011, covering the solar cycle 23 and the ascending phase of solar cycle 24, is studied. The new perspective of this contribution is that the CME-index, obtained from only the CMEs with angular width greater than 30 degrees, gives much better results than in previous works. The proposed model for the calculation of the modulated cosmic ray intensity obtained from the combination of solar indices and heliospheric parameters gives a very satisfactory value of the standard deviation. The best reproduction of the cosmic ray intensity is obtained by taking into account solar and interplanetary indices such as sunspot number, interplanetary magnetic field, CME-index, and heliospheric current sheet tilt. The standard deviation between the observed and calculated values is about 6.63% for the solar cycle 23 and 4.13% for the ascending part of solar cycle 24.

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Low frequency radio observations of the ‘background’ corona during the declining phase of solar cycle 24

2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) ◽

10.23919/ursiap-rasc.2019.8738381 ◽

2019 ◽

Author(s):

M. Vrunda ◽

R. Ramesh ◽

C. Kathiravan ◽

M. Rajesh

Keyword(s):

Solar Cycle ◽

Low Frequency ◽

Radio Observations ◽

Solar Cycle 24 ◽

Cycle 24

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Regression Analysis of Sunspot Numbers for the Solar Cycle 24 in Comparison to Previous Three Cycles

JOURNAL OF ADVANCES IN PHYSICS ◽

10.24297/jap.v4i2.2030 ◽

2014 ◽

Vol 4 (2) ◽

pp. 477-483

Author(s):

Debojyoti Halder

Keyword(s):

Regression Analysis ◽

Solar Cycle ◽

Sunspot Number ◽

The Sun ◽

Sunspot Numbers ◽

Solar Cycle 24 ◽

Current Cycle ◽

Cycle 24

Sunspots are temporary phenomena on the photosphere of the Sun which appear visibly as dark spots compared to surrounding regions. Sunspot populations usually rise fast but fall more slowly when observed for any particular solar cycle. The sunspot numbers for the current cycle 24 and the previous three cycles have been plotted for duration of first four years for each of them. It appears that the value of peak sunspot number for solar cycle 24 is smaller than the three preceding cycles. When regression analysis is made it exhibits a trend of slow rising phase of the cycle 24 compared to previous three cycles. Our analysis further shows that cycle 24 is approaching to a longer-period but with smaller occurrences of sunspot number.

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