The secular modulation of solar rotation from 1943 to 1992 and its time-delayed correlation with the 55-year grand cycle of the 11-year solar cycle

Solar Physics ◽  
1993 ◽  
Vol 148 (1) ◽  
pp. 11-26 ◽  
Author(s):  
Hirokazu Yoshimura ◽  
Maspul Aini Kambry
Keyword(s):  
Solar Cycle ◽  
Solar Rotation

scholarly journals Hemispheric injection of magnetic helicity by surface flux transport

2019 ◽  
Vol 631 ◽  
pp. A138 ◽  
Author(s):  
G. Hawkes ◽  
A. R. Yeates
Keyword(s):  
Magnetic Field ◽  
Solar Cycle ◽  
Solar Rotation ◽  
Surface Flux ◽  
Magnetic Helicity ◽  
Solar Cycles ◽  
Flux Transport ◽  
Transport Models ◽  
Radial Magnetic Field ◽  
Helicity Injection

Aims. We estimate the injection of relative magnetic helicity into the solar atmosphere by surface flux transport over 27 solar cycles (1700–2009). Methods. We determine the radial magnetic field evolution using two separate surface flux transport models: one driven by magnetogram inputs and another by statistical active region insertion guided by the sunspot number record. The injection of relative magnetic helicity is then computed from this radial magnetic field together with the known electric field in the flux transport models. Results. Neglecting flux emergence, solar rotation is the dominant contributor to the helicity injection. At high latitudes, the injection is always negative/positive in the northern/southern hemisphere, while at low latitudes the injection tends to have the opposite sign when integrated over the full solar cycle. The overall helicity injection in a given solar cycle depends on the balance between these two contributions. This net injected helicity correlates well with the end-of-cycle axial dipole moment.

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 The 22-year cycle in the geomagnetic 27-day recurrences reflecting on the F2-layer ionization

2004 ◽  
Vol 22 (4) ◽  
pp. 1171-1176 ◽  
Author(s):  
E. M. Apostolov ◽  
D. Altadill ◽  
M. Todorova
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Activity Index ◽  
Solar Rotation ◽  
Rotation Period ◽  
Sunspot Cycle ◽  
Solar Cycles ◽  
Solar Radio Flux ◽  
Critical Frequency Fof2 ◽  
Northern And Southern Hemispheres

Abstract. Solar cycle variations of the amplitudes of the 27-day solar rotation period reflected in the geomagnetic activity index Ap, solar radio flux F10.7cm and critical frequency foF2 for mid-latitude ionosonde station Moscow from the maximum of sunspot cycle 18 to the maximum of cycle 23 are examined. The analysis shows that there are distinct enhancements of the 27-day amplitudes for foF2 and Ap in the late declining phase of each solar cycle while the amplitudes for F10.7cm decrease gradually, and the foF2 and Ap amplitude peaks are much larger for even-numbered solar cycles than for the odd ones. Additionally, we found the same even-high and odd-low pattern of foF2 for other mid-latitude ionosonde stations in Northern and Southern Hemispheres. This property suggests that there exists a 22-year cycle in the F2-layer variability coupled with the 22-year cycle in the 27-day recurrence of geomagnetic activity. Key words. Ionosphere (mid-latitude ionosphere; ionosphere- magnetosphere interactions) – Magnetospheric physics (solar wind-magnetosphere interactions)

scholarly journals Signature of the 27-day solar rotation cycle in mesospheric OH and H<sub>2</sub>O observed by the Aura Microwave Limb Sounder

2011 ◽  
Vol 11 (10) ◽  
pp. 28477-28498 ◽  
Author(s):  
A. V. Shapiro ◽  
E. Rozanov ◽  
A. I. Shapiro ◽  
S. Wang ◽  
T. Egorova ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Solar Minimum ◽  
Solar Maximum ◽  
Solar Rotation ◽  
Time Lag ◽  
Correlation Coefficients ◽  
Maximum Period ◽  
First Time ◽  
Zero Time

Abstract. The mesospheric hydroxyl radical (OH) is mainly produced by the water vapor (H2O) photolysis and could be considered as a proxy for the influence of the solar irradiance variability on the mesosphere. We analyze the tropical mean response of the mesospheric OH and H2O data as observed by the Aura Microwave Limb Sounder (MLS) to 27-day solar variability. The analysis is performed for two time periods corresponding to the different phases of the 11-yr cycle: from December 2004 to December 2005 ("solar maximum" period with a pronounced 27-day solar cycle) and from November 2008 to November 2009 ("solar minimum" period with a vague 27-day solar cycle). We demonstrate, for the first time, that in the mesosphere the daily time series of OH concentrations correlate well with the solar irradiance (correlation coefficients up to 0.79) at zero time-lag. At the same time H2O anticorrelates (correlation coefficients up to −0.74) with the solar irradiance at non-zero time-lag. We found that the response of OH and H2O to the 27-day variability of the solar irradiance is strong for the solar maximum and negligible for the solar minimum conditions. It allows us to suggest that the 27-day cycle in the solar irradiance and in OH and H2O are physically connected.

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.

scholarly journals Signature of the 27-day solar rotation cycle in mesospheric OH and H<sub>2</sub>O observed by the Aura Microwave Limb Sounder

2012 ◽  
Vol 12 (7) ◽  
pp. 3181-3188 ◽  
Author(s):  
A. V. Shapiro ◽  
E. Rozanov ◽  
A. I. Shapiro ◽  
S. Wang ◽  
T. Egorova ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Solar Minimum ◽  
Solar Rotation ◽  
Time Lag ◽  
Correlation Coefficients ◽  
High Solar Activity ◽  
First Time ◽  
Zero Time ◽  
Daily Time

Abstract. The mesospheric hydroxyl radical (OH) is mainly produced by the water vapor (H2O) photolysis and could be considered as a proxy for the influence of the solar irradiance variability on the mesosphere. We analyze the tropical mean response of the mesospheric OH and H2O data as observed by the Aura Microwave Limb Sounder (MLS) to 27-day solar variability. The analysis is performed for two time periods corresponding to the different phases of the 11-yr cycle: from December 2004 to December 2005 (the period of "high activity" with a pronounced 27-day solar cycle) and from August 2008 to August 2009 ("solar minimum" period with a vague 27-day solar cycle). We demonstrate, for the first time, that in the mesosphere the daily time series of OH concentrations correlate well with the solar irradiance (correlation coefficients up to 0.79) at zero time-lag. At the same time H2O anticorrelates (correlation coefficients up to −0.74) with the solar irradiance at non-zero time-lag. We found that the response of OH and H2O to the 27-day variability of the solar irradiance is strong for the period of the high solar activity and negligible for the solar minimum conditions. It allows us to suggest that the 27-day cycle in the solar irradiance and in OH and H2O are physically connected.

Solar rotation over solar cycle 21

1991 ◽  
pp. 241-245
Author(s):  
Elisabeth Ribes ◽  
Istvan Vince ◽  
Pierre Mein ◽  
Eduardo Neto Ferreira
Keyword(s):  
Solar Cycle ◽  
Solar Rotation
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