scholarly journals The correlation between solar and geomagnetic activity – Part 3: An integral response model

2011 ◽  
Vol 29 (6) ◽  
pp. 1005-1018 ◽  
Author(s):  
Z. L. Du
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Decay Time ◽  
Response Model ◽  
Integral Response ◽  
Lag Times ◽  
The Relationship ◽  
Aa Index

Abstract. An integral response model is proposed to describe the relationship between geomagnetic activity (aa index) and solar activity (represented by sunspot number Rz): The aa at a given time t is the integral of Rz at past times (t'≤t) multiplied by an exponential decay factor of the time differences (e−(t−t')/τ), where τ is the decay time scale (~40 months). The correlation coefficient of aa with the reconstructed series based on this model (rf=0.85) is much higher than that of aa with Rz (r0=0.61). If this model is applied to each solar cycle, the correlation coefficient will be higher (rf=0.95). This model can naturally explain some phenomena related to aa and Rz, such as (i) the significant increase in the aa index (and its baseline) over the twentieth century; (ii) the longer lag times of aa to Rz at solar cycle maxima than at minima; and (iii) the variations in the correlations related to solar and Hale cycles. These results demonstrate that aa depends not only on the present Rz but also on past values. The profile of aa can be better predicted from Rz by this model than by point-point correspondence.

scholarly journals Solar Cycle Signals in the Pacific and the Issue of Timings

2012 ◽  
Vol 69 (4) ◽  
pp. 1446-1451 ◽  
Author(s):  
Indrani Roy ◽  
Joanna D. Haigh
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Aleutian Low ◽  
Positive Signal ◽  
Tropical Eastern Pacific ◽  
Sea Level Pressure ◽  
The Pacific ◽  
Strong Positive Signal ◽  
The Relationship ◽  
The Tropical Pacific

Abstract The solar cycle signal in sea level pressure during 1856–2007 is analyzed. Using composites of data from January–February in solar cycle peak years the strong positive signal in the region of the Aleutian low, found by previous authors, is confirmed. It is found, however, that signals in other regions of the globe, particularly in the South Pacific, are very sensitive to the choice of reference climatology. Also investigated is the relationship between solar activity and sea surface temperatures in the tropical eastern Pacific. A marked overall association of higher solar activity with colder temperatures in the tropical Pacific that is not restricted to years of peak sunspot number is noted. The ENSO-like variation following peak years that has been suggested by other authors is not found as a consistent signal. Both the SLP and SST signals vary coherently with the solar cycle and neither evolves on an ENSO-like time scale. The solar signals are weaker during the period spanning approximately 1956–97, which may be due to masking by a stronger innate ENSO variability at that time.

M(3000)F2 and IRI-2012 model at an equatorial latitude in the African sector

2021 ◽  
Vol 16 (3) ◽  
pp. 49-54
Author(s):  
A.O. Olawepo ◽  
J.O. Adeniyi ◽  
A. Afolabi
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Correlation Coefficient ◽  
High Solar Activity ◽  
Equatorial Latitude ◽  
Magnetic Declination ◽  
Two Peaks

We have used ionosonde data from Ouagadougou (Geo. Lat.12.40 N, Long. 358.50, Magnetic declination -5.1320) to study the morphology of M(3000)F2 and to investigate the performance of IRI-12 during 1991 and 1995, years of high and low solar activities respectively. Results show that M(3000)F2 exhibits diurnal and solar cycle characteristics with no distinctive monthly/seasonal features. The two peaks which characterize the diurnal M(3000)F2 during high solar activity (HSA) are reduced to just one (the sunrise peak) during low solar activity (LSA). The study also shows that IRI-12 gives good representations of the observed values of M(3000)F2 with high correlation coefficient, R ranging between 0.9 and 0.95 during LSA and 0.94 and 0.99 during HSA. The model gives its best performance in the months of April irrespective of the solar activity. It either under-estimates or over-estimates the observed values of M(3000)F2 during other months.

scholarly journals Estimating the maximum of the smoothed highest 3-hourly <i>a</i><i>a</i> index in 3 d by the preceding minimum for the solar cycle

2020 ◽  
Vol 38 (6) ◽  
pp. 1237-1245
Author(s):  
Zhanle Du
Keyword(s):  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Sunspot Cycle ◽  
Maximum Amplitude ◽  
Maximum Intensity ◽  
Activity Intensity ◽  
Future Space ◽  
Cycle 24 ◽  
Ap Index ◽  
Aa Index

Abstract. Predicting the maximum intensity of geomagnetic activity for an upcoming solar cycle is important in space weather service and for planning future space missions. This study analyzed the highest and lowest 3-hourly aa index (aaH∕aaL) in a 3 d interval, smoothed by 363 d to analyze their variation with the 11-year solar cycle. It is found that the maximum of aaH (aaHmax) is well correlated with the preceding minimum of either aaH (aaHmin, r=0.85) or aaL (aaLmin, r=0.89) for the solar cycle. Based on these relationships, the intensity of aaHmax for solar cycle 25 is estimated to be aaHmax(25)=83.7±6.9 (nT), about 29 % stronger than that of solar cycle 24. This value is equivalent to the ap index of apmax(25)=47.4±4.4 (nT) if employing the high correlation between ap and aa (r=0.93). The maximum of aaL (aaLmax) is also well correlated with the preceding aaHmin (r=0.80). The maximum amplitude of the sunspot cycle (Rm) is much better correlated with high geomagnetic activity (aaHmax, r=0.79) than with low geomagnetic activity (aaLmax, r=0.37). The rise time from aaHmin to aaHmax is weakly anti-correlated to the following aaHmax (r=-0.42). Similar correlations are also found for the 13-month smoothed monthly mean aa index. These results are expected to be useful in understanding the geomagnetic activity intensity of solar cycle 25.

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 The burst of solar and geomagnetic activity in August–September 2005

2009 ◽  
Vol 27 (3) ◽  
pp. 1019-1026 ◽  
Author(s):  
A. Papaioannou ◽  
H. Mavromichalaki ◽  
E. Eroshenko ◽  
A. Belov ◽  
V. Oleneva
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Neutron Monitor ◽  
Cosmic Ray ◽  
High Energy ◽  
X Ray ◽  
Cycle Minimum ◽  
Short Period ◽  
Ray Density

Abstract. During the August–September 2005 burst of solar activity, close to the current solar cycle minimum, a significant number of powerful X-ray flares were recorded, among which was the outstanding X17.0 flare of 7 September 2005. Within a relatively short period (from 22 August to 17 September) two severe magnetic storms were also recorded as well as several Forbush effects. These events are studied in this work, using hourly mean variations of cosmic ray density and anisotropy, derived from data of the neutron monitor network. During these Forbush effects the behavior of high energy cosmic ray characteristics (density and anisotropy) is analyzed together with interplanetary disturbances and their solar sources, and is compared to the variations observed in geomagnetic activity. A big and long lasting (~6 h) cosmic ray pre-decrease (~2%) is defined before the shock arrival on 15 September 2005. The calculated cosmic ray gradients for September 2005 are also discussed.

scholarly journals Examination of the relationship between solar activity and earth seismicity during the weak solar cycle 23

2018 ◽  
Vol 30 ◽  
pp. 5-15
Author(s):  
Mohamed Semeida ◽  
Sara Khodairy ◽  
Mahmoud El Hadidy ◽  
Rabab Abdel Hamed ◽  
Shahinaz Youssef ◽  
...  
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Sunspot Number ◽  
Seismic Activity ◽  
Solar Proton ◽  
Inverse Relation ◽  
Direct Relation ◽  
Radio Flux ◽  
Solar Cycle 23 ◽  
The Relationship

The relations between sunspot number, sunspot areas, and solar 10.7 cm radio flux, solar proton events and earthquakes of magnitude M ≥ 5 and M ≥ 8 during the interval from 1996 to 2008 of the solar cycle 23 have been analyzed in this work. We have found that there is a direct relation between solar activity and Earth seismic activity for M ≥ 5 and M ≥ 8, near the maximum of the solar cycle 23, and an inverse relation between them at the descending phase of the cycle.

scholarly journals Geomagnetic activity recurrences for predicting the amplitude and shape of solar cycle N. 25

2021 ◽  
Author(s):  
Piero Diego ◽  
Monica Laurenza
Keyword(s):  
Solar Activity ◽  
Solar Cycle ◽  
Geomagnetic Activity ◽  
Space Weather ◽  
Climate Data ◽  
Activity Prediction ◽  
Successful Prediction ◽  
Physical Phenomena ◽  
Maximum Sunspot

The prediction of solar activity is one of the most challenging topics among the various Space    Weather and Space Climate issues. In the last decades, the constant enhancement of Space Climate    data allowed to improve the comprehension of the related physical phenomena and the statistical    bases for prediction algorithms. For this purpose, we used geomagnetic indices to provide a pow erful algorithm (see Diego et al 2010) for the solar activity prediction, based on the evaluation of    the recurrence rate in the geomagnetic activity. The aim of this paper is to present the validation    of our algorithm over solar cycle n. 24, for which a successful prediction was made, and upgrade    it to forecast the shape and time as well as the amplitude of the upcoming cycle n. 25. Contrary    to the consensus, we predict it to be quite high, with a maximum sunspot number of 205  ±  29,  that should be reached in the first half of 2023. This prediction is consistent with the scenario in    which the long-term Gleissberg cycle has reached its minimum in cycle n. 24 and the rising phase  is beginning.

scholarly journals Predicting the maximum <i>aa</i>/<i>Ap</i> index through its relationship with the preceding minimum

2020 ◽  
Author(s):  
Zhanle Du
Keyword(s):  
Correlation Coefficient ◽  
Geomagnetic Activity ◽  
Rise Time ◽  
Sunspot Cycle ◽  
Maximum Amplitude ◽  
Peak Time ◽  
Future Space ◽  
Cycle 24 ◽  
Ap Index ◽  
Aa Index

Abstract. Predicting the strength and peak time of geomagnetic activity for the ensuing cycle 25 is important in space weather service for planning future space missions. The minimum aa geomagnetic index around the solar minimum has been often used to predict the maximum amplitude of sunspot cycle, but seldom used to directly predict the maximum aa index. This study analyzed the relationships between the maxima and minima of both the geomagnetic aa and Ap indices for the 11-year cycle. The maximum aa index is found to be well correlated to the preceding minimum with a correlation coefficient of r = 0.860. As a result, the maximum aa index for the ensuing cycle 25 is predicted to be aamax(25) = 26.9 ± 2.6. This value is equivalent to Apmax(25) = 17.3 ± 1.8 ± 1.2 if employing the high correlation between aa and Ap (r = 0.939). The maximum Ap index is also found to be well correlated to the preceding minimum with a correlation coefficient of r = 0.862. Based on this correlation, the maximum Ap index is predicted to be a slightly higher value of Apmax(25) = 19.0 ± 1.6. The rise time of the aa (Ap) index for the 11-year cycle is found to be nearly uncorrelated to the following maximum, r = −0.16 (−0.17). If the data point for cycle 24 (which is far from others) were not considered, the rise time of the Ap index for the 11-year cycle would be weakly correlated to the following maximum, r = −0.404 at a confidence level of 62 %. The rise time for cycle 25 would be roughly estimated to be 89.9 ± 31.6 (months), implying that the geomagnetic activity for the ensuing cycle 25 would peak around April 2025 ± 32 months.

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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