scholarly journals Evidence of a strong relationship between hemispheric asymmetry in solar coronal rotation and solar activity during solar cycle 24

2020 ◽  
Vol 499 (4) ◽  
pp. 5442-5446
Author(s):  
Jaidev Sharma ◽  
Anil K Malik ◽  
Brajesh Kumar ◽  
Hari Om Vats
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Rotation Rate ◽  
Hemispheric Asymmetry ◽  
Solar Rotation ◽  
Strong Relationship ◽  
Space Mission ◽  
Asymmetry Index ◽  
Coronal Rotation ◽  
Solar Coronal

ABSTRACT In this paper, we report evidence of a very strong and statistically significant relationship between hemispheric asymmetry in the solar coronal rotation rate and solar activity. Our approach is based on the cross-correlation of the hemispheric asymmetry index (AI) in the rotation rate with annual solar activity indicators. To obtain the hemispheric asymmetry in the solar rotation rate, we use solar full disc (SFD) images at 30.4-, 19.5- and 28.4-nm wavelengths for the 24th solar cycle, that is, for the period from 2008 to 2018, as recorded by the Solar Terrestrial Relations Observatory (STEREO) space mission. Our analysis shows that the hemispheric asymmetry in rotation rate is high during the solar maxima from 2011 to 2014. However, hemispheric asymmetry decreases gradually on both sides (i.e. from 2008 to 2011 and from 2014 to 2018). The results show that the AI leads sunspot numbers by ∼ 1.56 yr. This is a clear indication that hemispheric asymmetry triggers the formation of sunspots in conjunction with the differential rotation of the Sun.

scholarly journals Lower Thermosphere response to solar activity: an EMD analysis of GOCE 2009–2012 data

2020 ◽  
Author(s):  
Alberto Bigazzi ◽  
Carlo Cauli ◽  
Francesco Berrilli
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Dynamic Range ◽  
Solar Rotation ◽  
Lower Thermosphere ◽  
Space Mission ◽  
Solar Flux ◽  
Mission Design ◽  
Specific Response ◽  
Uv Spectrum

Abstract. Forecasting the Thermosphere (Atmosphere's uppermost layer, from about 90 to 800 km altitude) is crucial to many space-related applications, from space mission design, to re-entry operations, to space surveillance. Thermospheric dynamics is directly linked to the solar dynamics through the solar UV input, which is highly variable, and through the solar wind and plasma fluxes, impacting Earth's magnetosphere. The solar input is non-periodic and non-stationary, with long-term modulations from the solar rotation and the solar cycle, and impulsive components, due to magnetic storms. Proxies of the solar input exist and may be used to forecast the thermosphere, such as the F10.7 radio flux and the MgII EUV flux. They relate to physical processes on the Solar atmosphere. Other indices, such as the Ap geomagnetic index, connect with Earth's geomagnetic environment. We analyse the proxies' time series comparing them with in-situ density data from the ESA/GOCE gravity mission, operational from March 2009 to November 2013, therefore covering the full rising phase of solar cycle XXIV, exposing the entire dynamic range of the solar input. We use Empirical Mode Decomposition (EMD), an analysis technique appropriate to non-periodic, multi-scale signals. Data are taken at an altitude of 260 km, exceptionally low for a LEO satellite, where density variations are the single most important perturbation to satellite dynamics. We show that the synthesized signal from optimally selected combinations of proxies's basis functions, notably Mg II for the solar flux and Ap for the plasma component, shows a very good agreement with thermospheric data obtained by GOCE, during low and medium solar activity periods. In periods of maximum solar activity, density enhancements are also well represented. The Mg II index proves to be, in general, a better proxy than the F10.7 one, to model the solar flux, because of its specific response to the UV spectrum, whose variations have the largest impact over thermospheric density.

LASCO FeXIV and FeX observations of the solar coronal rotation during the recent solar activity minimum

1999 ◽  
Author(s):  
B. Inhester ◽  
G. Stenborg ◽  
R. Schwenn ◽  
N. Srivastava ◽  
B. Podlipnik
Keyword(s):  
Solar Activity ◽  
Solar Activity Minimum ◽  
Coronal Rotation ◽  
Solar Coronal

Study of Long-Term Variations in Hemispheric Asymmetry of Solar Activity

2018 ◽  
Vol 13 (S340) ◽  
pp. 259-260
Author(s):  
B. Ravindra ◽  
J. Javaraiah
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Hemispheric Asymmetry ◽  
Sunspot Area ◽  
Sunspot Activity ◽  
Phase Lag ◽  
Double Peak ◽  
Northern And Southern Hemispheres ◽  
Long Term Variations

AbstractSunspot activity exhibits hemispheric asymmetry. We study the long-term variations in the hemispheric sunspot area from Kodaikanal white-light data during 1921 – 2011. The results on the presence or absence of double peak in an individual solar cycle, dominant hemispheric activity, and phase lag between the activities of northern and southern hemispheres, etc., are presented.

Distribution of hemispheric solar activity during various phases of solar cycles

2018 ◽  
Vol 13 (S340) ◽  
pp. 261-262
Author(s):  
G. L. Jayalekshmi ◽  
P. R. Prince
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Hemispheric Asymmetry ◽  
The Other ◽  
Solar Dynamo ◽  
Solar Cycles ◽  
Periodic Behaviour ◽  
The Asymmetry ◽  
Very High ◽  
South Asymmetry

AbstractHemispheric asymmetry is one of the significant parameters related to the action of solar dynamo. Comparison of hemispheric activities during various phases are found out for solar cycles 12 to 23. Asymmetry of solar activity shows extremum values during the cycles 14 and 19. Lowest and highest levels of north-south asymmetry are mainly observed during minimum and maximum phases respectively of solar cycles. A change of phase is found to be existing between the asymmetries at solar maxima and the whole cycle, after solar cycle 15 and 18. Also, for cycles 17-19, the behaviour of the asymmetry is observed to be peculiar and different from that of the other cycles. Periodic behaviour of north-south asymmetry mainly occurs in 8.8 years and noticed very high during the cycles 18-22.

scholarly journals Solar Rotation over Solar Cycle 21

1991 ◽  
Vol 130 ◽  
pp. 241-245
Author(s):  
Elisabeth Ribes ◽  
Istvan Vince ◽  
Pierre Mein ◽  
Eduardo Neto Ferreira
Keyword(s):  
Solar Cycle ◽  
Differential Rotation ◽  
Rotation Rate ◽  
Meridional Circulation ◽  
Solar Rotation ◽  
Circulation Pattern ◽  
Rotation Rates ◽  
Grand Average ◽  
Order Of Magnitude ◽  
The Mean

Abstract Having measured the rotation rate of sunspots through solar cycle 21, from 1977 to 1983, we have found that the mean differential rotation averaged over this seven year record is similar to the grand average differential rotation determined by Howard et al. (1984) over the period 1921-1982. However, the rotation rate does change from year to year. These changes are evidenced by a steepening or a flattening of the mean differential rotation profile, as well as significant changes in the equatorial rate. The presence of a time-dependent pattern of azimuthal rolls inferred from the meridional circulation pattern of the sunspots offers a qualitative explanation of the observed rotation rates. The amplitude of the changes is almost one order of magnitude larger than that of the torsional oscillations found by Howard and LaBonte (1981).

scholarly journals Modelling variability of solar activity cycles

2018 ◽  
Vol 615 ◽  
pp. A38 ◽  
Author(s):  
L. L. Kitchatinov ◽  
A. V. Mordvinov ◽  
A. A. Nepomnyashchikh
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Transport Model ◽  
Magnetic Energy ◽  
Solar Rotation ◽  
Rotation Period ◽  
Poloidal Field ◽  
Flux Transport ◽  
Activity Cycles ◽  
Solar Activity Cycles

Context. Solar activity cycles vary in amplitude and duration. The variations can be at least partly explained by fluctuations in dynamo parameters. Aims. We want to restrict uncertainty in fluctuating dynamo parameters and find out which properties of the fluctuations control the amplitudes of the magnetic field and energy in variable dynamo cycles. Methods. A flux-transport model for the solar dynamo with fluctuations of the Babcock–Leighton type α-effect was applied to generate statistics of magnetic cycles for our purposes. The statistics were compared with data on solar cycle periods to restrict the correlation time of dynamo fluctuations. Results. A characteristic time of fluctuations in the α-effect is estimated to be close to the solar rotation period. The fluctuations produce asymmetry between the times of rise and descent of dynamo cycles, the rise time being on average shorter. The affect of the fluctuations on cycle amplitudes depends on the phase of the cycle in which the fluctuations occur. Negative fluctuations (decrease in α) in the rise phase delay decay of poloidal field and increase the cycle amplitude in toroidal field and magnetic energy. Negative fluctuation in the decline phase reduces the polar field at the end of a cycle and the amplitude of the next cycle. The low amplitude of the 24th solar cycle compared to the preceding 23rd cycle can be explained by this effect. Positive fluctuations in the descent phase enhance the magnetic energy of the next cycle by increasing the seed poloidal field for the next cycle. The statistics of the computed energies of the cycles suggest that superflares of ≥1034 erg are not possible on the Sun.

Influence of Magnetic Fields on Solar Hydrodynamics: Experimental Results

1977 ◽  
Vol 36 ◽  
pp. 143-180 ◽  
Author(s):  
J.O. Stenflo
Keyword(s):  
Solar Activity ◽  
Energy Balance ◽  
Magnetic Fields ◽  
Solar Atmosphere ◽  
General Problem ◽  
Solar Rotation ◽  
Active Regions ◽  
Physical Conditions ◽  
Dynamic Phenomena

It is well-known that solar activity is basically caused by the Interaction of magnetic fields with convection and solar rotation, resulting in a great variety of dynamic phenomena, like flares, surges, sunspots, prominences, etc. Many conferences have been devoted to solar activity, including the role of magnetic fields. Similar attention has not been paid to the role of magnetic fields for the overall dynamics and energy balance of the solar atmosphere, related to the general problem of chromospheric and coronal heating. To penetrate this problem we have to focus our attention more on the physical conditions in the ‘quiet’ regions than on the conspicuous phenomena in active regions.

Prominences and Solar Activity

1979 ◽  
Vol 44 ◽  
pp. 357-372
Author(s):  
Z. Švestka
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
List Type ◽  
Type Number ◽  
Flare Loops ◽  
Filament Activation

The following subjects were discussed:(1)Filament activation(2)Post-flare loops.(3)Surges and sprays.(4)Coronal transients.(5)Disk vs. limb observations.(6)Solar cycle variations of prominence occurrence.(7)Active prominences patrol service.Of all these items, (1) and (2) were discussed in most detail and we also pay most attention to them in this report. Items (3) and (4) did not bring anything new when compared with the earlier invited presentations given by RUST and ZIRIN and therefore, we omit them.

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