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.

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 Relationships between the AE, ap and Dst indices near solar minimum (1974) and at solar maximum (1979)

1997 ◽  
Vol 15 (10) ◽  
pp. 1265-1270 ◽  
Author(s):  
M. M. Fares Saba ◽  
W. D. Gonzalez ◽  
A. L. Clúa de Gonzalez
Keyword(s):  
Seasonal Variation ◽  
Solar Minimum ◽  
Ring Current ◽  
Geomagnetic Storms ◽  
Solar Maximum ◽  
Correlation Coefficients ◽  
The Sun ◽  
Yearly Average ◽  
First Time ◽  
Activity Indices

Abstract. Three-hourly average values of the Dst, AE and ap geomagnetic activity indices have been studied for 1 year's duration near the solar minimum (1974) and also at the solar maximum (1979). In 1979 seven intense geomagnetic storms (Dst <–100 nT) occurred, whereas in 1974 only three were reported. This study reveals: (1) the yearly average of AE is greater in 1974 than in 1979, whereas the inverse seems to be true for the yearly average of Dst, when a higher number of intense storms is present. These averages indicate the kind of activity occurring on the sun as shown in earlier work. (2) The seasonal variation of Dst is higher than that of ap and is almost negligible in AE. (3) The correlation coefficient of ap × AE is in general the highest, as the magnetometers that monitor both indices are close, and is surpassed only by the ap × Dst correlation during geomagnetic storms, when the influence of the ring current is dominant. The correlation of ap × Dst also shows a seasonal variability. (4) For the first time a study of correlation between ap and a linear combination of AE and Dst has also been made. We found higher correlation coefficients in this case as compared to those between ap × Dst and ap × AE.

scholarly journals Inflection point in the power spectrum of stellar brightness variations

2020 ◽  
Vol 636 ◽  
pp. A69 ◽  
Author(s):  
E. M. Amazo-Gómez ◽  
A. I. Shapiro ◽  
S. K. Solanki ◽  
N. A. Krivova ◽  
G. Kopp ◽  
...  
Keyword(s):  
Solar Activity ◽  
Power Spectrum ◽  
Solar Irradiance ◽  
Inflection Point ◽  
Solar Rotation ◽  
Light Curves ◽  
High Solar Activity ◽  
The Sun ◽  
Rotation Periods ◽  
Active Stars

Context. Young and active stars generally have regular, almost sinusoidal, patterns of variability attributed to their rotation, while the majority of older and less active stars, including the Sun, have more complex and non-regular light curves, which do not have clear rotational-modulation signals. Consequently, the rotation periods have been successfully determined only for a small fraction of the Sun-like stars (mainly the active ones) observed by transit-based planet-hunting missions, such as CoRoT, Kepler, and TESS. This suggests that only a small fraction of such systems have been properly identified as solar-like analogues. Aims. We aim to apply a new method of determining rotation periods of low-activity stars, such as the Sun. The method is based on calculating the gradient of the power spectrum (GPS) of stellar brightness variations and identifying a tell-tale inflection point in the spectrum. The rotation frequency is then proportional to the frequency of that inflection point. In this paper, we compare this GPS method to already-available photometric records of the Sun. Methods. We applied GPS, auto-correlation functions, Lomb-Scargle periodograms, and wavelet analyses to the total solar irradiance (TSI) time series obtained from the Total Irradiance Monitor on the Solar Radiation and Climate Experiment and the Variability of solar IRradiance and Gravity Oscillations experiment on the SOlar and Heliospheric Observatory missions. We analysed the performance of all methods at various levels of solar activity. Results. We show that the GPS method returns accurate values of solar rotation independently of the level of solar activity. In particular, it performs well during periods of high solar activity, when TSI variability displays an irregular pattern, and other methods fail. Furthermore, we show that the GPS and light curve skewness can give constraints on facular and spot contributions to brightness variability. Conclusions. Our results suggest that the GPS method can successfully determine the rotational periods of stars with both regular and non-regular light curves.

scholarly journals The Contribution of Geomagnetic Activity to Ionospheric foF2 Trends at Different Phases of the Solar Cycle by SWM

Atmosphere ◽  
2020 ◽  
Vol 11 (6) ◽  
pp. 616
Author(s):  
Haimeng Li ◽  
Jing-Song Wang ◽  
Zhou Chen ◽  
Lianqi Xie ◽  
Fan Li ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Temporal Variability ◽  
Solar Minimum ◽  
Time Lag ◽  
Maximum Level ◽  
Ionospheric Perturbations ◽  
Geomagnetic Activities

Solar activity dominates the temporal variability of ionospheric properties, which makes it difficult to identify and isolate the effects of geomagnetic activity on the ionosphere. Therefore, the latter effects on the ionosphere are still unclear. Here, we use the spectral whitening method (SWM)—a proven approach to extract ionospheric perturbations caused by geomagnetic activity—to directly obtain, in isolation, the effects of geomagnetic activity. We study its contribution to the ionosphere for different phases of the solar cycle. The time lag between the solar and geomagnetic activities provides an opportunity to understand the contribution of geomagnetic activity to the perturbation of the ionosphere. The results suggest that this contribution to the ionosphere is significant when geomagnetic activity is at its maximum level, which usually happens in the declining phase of the solar cycle, but the contribution is very weak at the solar minimum and during the ascending phase. Then, by analyzing the contributions in different months, we find that the role of geomagnetic activity is larger around winter but smaller around summer.

scholarly journals Solar Forcing for CMIP6 (v3.1)

2016 ◽  
Author(s):  
Katja Matthes ◽  
Bernd Funke ◽  
Monika E. Anderson ◽  
Luke Barnard ◽  
Jürg Beer ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Climate Variability ◽  
Solar Irradiance ◽  
Climate Models ◽  
Galactic Cosmic Rays ◽  
Radiative Properties ◽  
Transfer Model ◽  
Solar Forcing ◽  
Heating Rates ◽  
First Time

Abstract. This paper describes the solar forcing dataset for CMIP6 and highlights in particular changes with respect to the CMIP5 recommendation. The solar forcing is provided for radiative properties, i.e., total solar irradiance (TSI) and solar spectral irradiance (SSI), and F10.7 cm radio flux, as well as particle forcing, i.e., geomagnetic indices Ap and Kp, and ionisation rates to account for effects of solar protons, electrons and galactic cosmic rays. This is the first time that a recommendation for solar-driven particle forcing is provided for a CMIP exercise. The solar forcing dataset is provided at daily and monthly resolution separately for the CMIP6 Historical Simulation (1850–2014), for the future (2015–2300), including an additional extreme Maunder Minimum-like sensitivity scenario, as well as for a constant and a time-varying forcing for the preindustrial control simulation. The paper not only describes the forcing dataset, but also provides detailed recommendations for how to implement the different forcing components in climate models. The TSI and SSI time series are defined as averages of two (semi-) empirical solar irradiance models, namely the NRLTSI2/NRLSSI2 and SATIRE-TS. A new and lower TSI value is recommended: the contemporary solar cycle-average is now 1361.0 W/m2. The slight negative trend in TSI during the last three solar cycles in CMIP6 is statistically indistinguishable from available observations and only leads to a small global radiative forcing of −0.04 W/m2. In the 200–400 nm range, which is also important for ozone photochemistry, CMIP6 shows a larger solar cycle variability contribution to TSI than CMIP5 (50 % as compared to 35 %). The CMIP6 dataset is tested and compared to its CMIP5 predecessor using timeslice experiments of two chemistry-climate models and a reference radiative transfer model. The changes in the background SSI in the CMIP6 dataset, as compared to CMIP5, impact on climatological stratospheric conditions (lower shortwave heating rates (−0.35 K/day at the stratopause), cooler stratospheric temperatures (−1.5 K in the upper stratosphere), lower ozone abundances in the lower stratosphere (−3 %), and higher ozone abundances (+1.5 % in the upper stratosphere and lower mesosphere). Between the maximum and minimum phases of the 11-year solar cycle, there is an increase in shortwave heating rates (+0.2 K/day at the stratopause), temperatures (~1 K at the stratopause), and ozone (+2.5 % in the upper stratosphere) in the tropical upper stratosphere using the CMIP6 forcing dataset. This solar cycle response is slightly larger, but not statistically significantly different from that for the CMIP5 forcing dataset. CMIP6 models with a well-resolved shortwave radiation scheme are encouraged to use SSI, as well as solar-induced ozone signals, in order to better represent solar climate variability compared to models that only prescribe TSI and/or exclude the solar-ozone response. Monthly mean solar-induced ozone variations will also be incorporated into the CCMI CMIP6 Ozone Database for climate models that do not calculate ozone interactively. CMIP6 models with interactive chemistry are encouraged to use the particle forcing which will allow the potential long-term effect of particles to be addressed for the first time. The consideration of particle forcing has been shown to significantly improve the representation of reactive nitrogen and ozone variability in the polar middle atmosphere, eventually resulting in further improvements of the representation of solar climate variability.

scholarly journals Solar irradiance at the Earth's surface: long-term behavior observed at the South Pole

2010 ◽  
Vol 10 (11) ◽  
pp. 25871-25908 ◽  
Author(s):  
J. E. Frederick ◽  
A. L. Hodge
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Solar Minimum ◽  
Austral Summer ◽  
Small Variation ◽  
Summer Solstice ◽  
South Pole ◽  
The South ◽  
Clear Sky

Abstract. This research examines a 17-year database of UV-A (320–400 nm) and visible (400–600 nm) solar irradiance obtained by a scanning spectroradiometer located at the South Pole. The goal is to define the variability in solar irradiance reaching the polar surface, with emphasis on the influence of cloudiness and on identifying systematic trends and possible links to the solar cycle. To eliminate changes associated with the varying solar elevation, the analysis focuses on data averaged over 30–35 day periods centered on each year's austral summer solstice. The long-term average effect of South Polar clouds is a small attenuation, with the mean measured irradiances being about 5–6% less than the clear-sky values, although at any specific time clouds may reduce or enhance the signal that reaches the sensor. The instantaneous fractional attenuation or enhancement is wavelength dependent, where the percent deviation from the clear-sky irradiance at 400–600 nm is typically 2.5 times that at 320–340 nm. When averaged over the period near each year's summer solstice, significant correlations appear between irradiances at all wavelengths and the solar cycle as measured by the 10.7 cm solar radio flux. An approximate 1.8 ± 1.0% decrease in ground-level irradiance occurs from solar maximum to solar minimum for the wavelength band 320–400 nm. The corresponding decrease for 400–600 nm is 2.4 ± 1.9%. The best-estimate declines appear too large to originate in the sun. If the correlations have a geophysical origin, they suggest a small variation in atmospheric attenuation with the solar cycle over the period of observation, with the greatest attenuation occurring at solar minimum.

scholarly journals Diurnal, seasonal, latitudinal and solar cycle variation of electron temperature in the topside F-region of the Indian zone ionosphere

2007 ◽  
Vol 25 (9) ◽  
pp. 1995-2006 ◽  
Author(s):  
M. Chamua ◽  
P. K. Bhuyan ◽  
P. Subrahmanyam ◽  
S. C. Garg
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Electron Temperature ◽  
Time Scale ◽  
Time Lag ◽  
Solar Flux ◽  
Activity Period ◽  
High Solar Activity ◽  
Solar Cycle Variation ◽  
Solar Cycle 23

Abstract. Electron temperature Te observed by the SROSS C2 satellite at equatorial and low latitudes during the low to high solar activity period of 1995–2001 at the height of ~500 km is investigated in terms of local time, season, latitude, solar sunspot number Rz and F10.7 cm solar flux. The satellite covered the latitude belt of 31° S–34° N and the longitude range of 40°–100° E. The average nighttime (20:00–04:00 LT) Te varies between 750–1200 K and then rises sharply in the sunrise period (04:00–06:00 LT) to the morning high from 07:00 to 10:00 LT and attains a daytime (10:00–14:00 LT) average of 1100–2300 K. The morning enhancement is more pronounced in the equinoxes. A secondary maximum in Te is also observed around 16:00–18:00 LT in the June solstice and in the equinoxes. Daytime electron temperature was found to be higher in autumn compared to that in spring in all latitudes. Between the solstices, the amplitude of the morning enhancement is higher in winter compared to that in summer. Both day and nighttime Te observed by the SROSS C2 satellite bears a positive correlation with solar activity when averaged on a shorter time scale, i.e. over the period of a month. But on a longer time scale, i.e. averaged over a year, the daytime electron temperature gradually decreases from 1995 till it reaches the minimum value in 1997, after which Te again continues to rise till 2001. The variations are distinctly seen in summer and in the equinoxes. The sunspot activity during solar cycle 23 was minimum in 1996 and maximum in 2000. Annual average electron temperature, therefore, appears to follow the variation of solar activity with a time lag of about one year, both at the bottom and top of solar cycle 23, indicating an inherent inertia of the ionosphere thermosphere regime to variations in solar flux.

scholarly journals Solar forcing for CMIP6 (v3.2)

2017 ◽  
Vol 10 (6) ◽  
pp. 2247-2302 ◽  
Author(s):  
Katja Matthes ◽  
Bernd Funke ◽  
Monika E. Andersson ◽  
Luke Barnard ◽  
Jürg Beer ◽  
...  
Keyword(s):  
Solar Cycle ◽  
Climate Variability ◽  
Solar Irradiance ◽  
Climate Models ◽  
Time Varying ◽  
Solar Forcing ◽  
Heating Rates ◽  
First Time ◽  
Ozone Variations

Abstract. This paper describes the recommended solar forcing dataset for CMIP6 and highlights changes with respect to CMIP5. The solar forcing is provided for radiative properties, namely total solar irradiance (TSI), solar spectral irradiance (SSI), and the F10.7 index as well as particle forcing, including geomagnetic indices Ap and Kp, and ionization rates to account for effects of solar protons, electrons, and galactic cosmic rays. This is the first time that a recommendation for solar-driven particle forcing has been provided for a CMIP exercise. The solar forcing datasets are provided at daily and monthly resolution separately for the CMIP6 preindustrial control, historical (1850–2014), and future (2015–2300) simulations. For the preindustrial control simulation, both constant and time-varying solar forcing components are provided, with the latter including variability on 11-year and shorter timescales but no long-term changes. For the future, we provide a realistic scenario of what solar behavior could be, as well as an additional extreme Maunder-minimum-like sensitivity scenario. This paper describes the forcing datasets and also provides detailed recommendations as to their implementation in current climate models.For the historical simulations, the TSI and SSI time series are defined as the average of two solar irradiance models that are adapted to CMIP6 needs: an empirical one (NRLTSI2–NRLSSI2) and a semi-empirical one (SATIRE). A new and lower TSI value is recommended: the contemporary solar-cycle average is now 1361.0 W m−2. The slight negative trend in TSI over the three most recent solar cycles in the CMIP6 dataset leads to only a small global radiative forcing of −0.04 W m−2. In the 200–400 nm wavelength range, which is important for ozone photochemistry, the CMIP6 solar forcing dataset shows a larger solar-cycle variability contribution to TSI than in CMIP5 (50 % compared to 35 %).We compare the climatic effects of the CMIP6 solar forcing dataset to its CMIP5 predecessor by using time-slice experiments of two chemistry–climate models and a reference radiative transfer model. The differences in the long-term mean SSI in the CMIP6 dataset, compared to CMIP5, impact on climatological stratospheric conditions (lower shortwave heating rates of −0.35 K day−1 at the stratopause), cooler stratospheric temperatures (−1.5 K in the upper stratosphere), lower ozone abundances in the lower stratosphere (−3 %), and higher ozone abundances (+1.5 % in the upper stratosphere and lower mesosphere). Between the maximum and minimum phases of the 11-year solar cycle, there is an increase in shortwave heating rates (+0.2 K day−1 at the stratopause), temperatures ( ∼  1 K at the stratopause), and ozone (+2.5 % in the upper stratosphere) in the tropical upper stratosphere using the CMIP6 forcing dataset. This solar-cycle response is slightly larger, but not statistically significantly different from that for the CMIP5 forcing dataset.CMIP6 models with a well-resolved shortwave radiation scheme are encouraged to prescribe SSI changes and include solar-induced stratospheric ozone variations, in order to better represent solar climate variability compared to models that only prescribe TSI and/or exclude the solar-ozone response. We show that monthly-mean solar-induced ozone variations are implicitly included in the SPARC/CCMI CMIP6 Ozone Database for historical simulations, which is derived from transient chemistry–climate model simulations and has been developed for climate models that do not calculate ozone interactively. CMIP6 models without chemistry that perform a preindustrial control simulation with time-varying solar forcing will need to use a modified version of the SPARC/CCMI Ozone Database that includes solar variability. CMIP6 models with interactive chemistry are also encouraged to use the particle forcing datasets, which will allow the potential long-term effects of particles to be addressed for the first time. The consideration of particle forcing has been shown to significantly improve the representation of reactive nitrogen and ozone variability in the polar middle atmosphere, eventually resulting in further improvements in the representation of solar climate variability in global models.

scholarly journals Solar cycle variations of stratospheric ozone and temperature in simulations of a coupled chemistry-climate model

2006 ◽  
Vol 6 (6) ◽  
pp. 12121-12153 ◽  
Author(s):  
J. Austin ◽  
L. L. Hood ◽  
B. E. Soukharev
Keyword(s):  
Solar Cycle ◽  
Vertical Profile ◽  
Climate Model ◽  
Solar Rotation ◽  
Stratospheric Ozone ◽  
Sea Surface ◽  
Sea Surface Temperatures ◽  
Surface Temperatures ◽  
Solar Phase ◽  
First Time

Abstract. The results from three 45-year simulations of a coupled chemistry climate model are analysed for solar cycle influences on ozone and temperature. The simulations include UV forcing at the top of the atmosphere, which includes a generic 27-day solar rotation effect as well as the observed monthly values of the solar fluxes. The results are analysed for the 27-day and 11-year cycles in temperature and ozone. In accordance with previous results, the 27-day cycle results are in good qualitative agreement with observations, particularly for ozone. However, the results show significant variations, typically a factor of two or more in sensitivity to solar flux, depending on the solar cycle. We show for the first time good agreement also between the observed 11-year cycle and model results for the ozone vertical profile, which both indicate a minimum in solar response near 20 hPa. In comparison, simulations of the model with fixed solar phase (solar maximum/solar mean) and climatological sea surface temperatures lead to a poor simulation of the solar response in the ozone vertical profile. The results indicate the need for variable phase simulations in solar sensitivity experiments and the role of sea surface temperatures is discussed.

scholarly journals Solar irradiance at the earth's surface: long-term behavior observed at the South Pole

2011 ◽  
Vol 11 (3) ◽  
pp. 1177-1189 ◽  
Author(s):  
J. E. Frederick ◽  
A. L. Hodge
Keyword(s):  
Solar Cycle ◽  
Solar Irradiance ◽  
Solar Minimum ◽  
Austral Summer ◽  
Small Variation ◽  
Summer Solstice ◽  
South Pole ◽  
The South ◽  
Clear Sky

Abstract. This research examines a 17-year database of UV-A (320–400 nm) and visible (400–600 nm) solar irradiance obtained by a scanning spectroradiometer located at the South Pole. The goal is to define the variability in solar irradiance reaching the polar surface, with emphasis on the influence of cloudiness and on identifying systematic trends and possible links to the solar cycle. To eliminate changes associated with the varying solar elevation, the analysis focuses on data averaged over 30–35 day periods centered on each year's austral summer solstice. The long-term average effect of South Polar clouds is a small attenuation, with the mean measured irradiances being about 5–6% less than the clear-sky values, although at any specific time clouds may reduce or enhance the signal that reaches the sensor. The instantaneous fractional attenuation or enhancement is wavelength dependent, where the percent deviation from the clear-sky irradiance at 400–600 nm is typically 2.5 times that at 320–340 nm. When averaged over the period near each year's summer solstice, significant correlations appear between irradiances at all wavelengths and the solar cycle as measured by the 10.7 cm solar radio flux. An approximate 1.8 ± 1.0% decrease in ground-level irradiance occurs from solar maximum to solar minimum for the wavelength band 320–400 nm. The corresponding decrease for 400–600 nm is 2.4 ± 1.9%. The best-estimate declines appear too large to originate in the sun. If the correlations have a geophysical origin, they suggest a small variation in atmospheric attenuation with the solar cycle over the period of observation, with the greatest attenuation occurring at solar minimum.

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