Evolution of the Sunspot Number and Solar Wind B $B$ Time Series

Cliver, E. W.; Herbst, K.

doi:10.1007/s11214-018-0487-4

Cited by 12 publications

(9 citation statements)

References 139 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…They used the data for the period covering cycles 14-23. Cliver and Herbst (2018) discussed the recent developments in the floor of HMF and reported that the floor level could have gone well below around 1.5 nT during the Maunder minimum period. Further, it is interesting to note, as seen from Figure 3c that, in cycle 24, the B HMF by the year 2018 has already approached the value of the floor level of 4.6 nT about 2 years prior to the minimum of cycle 24.…”

Section: Heliospheric Magnetic Field (Hmf)mentioning

confidence: 99%

Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25

Janardhan

Ananthakrishnan

2020

JGR Space Physics

View full text Add to dashboard Cite

We examine the temporal changes in both solar polar magnetic field (PMF) at latitudes ≥45° and heliospheric magnetic field (HMF) at 1 AU during solar cycles 21–24 with emphasis on the recent activity changes after July 2015, the so called “mini solar maximum” of cycle 24. While unsigned PMF shows solar cycle modulations in cycles 21 and 22, it shows an anti‐correlation with solar cycle variation in cycle 24. In addition, the floor level of the HMF (of 4.6 nT), that is, the value that the HMF returns to at each solar minimum, is breached about 2 years prior to cycle 24 minimum, indicating a reduced HMF floor level of 3.2 ± 0.5 nT in the upcoming cycle 24 minimum. In light of the change of unsigned PMF and the availability of a revised smoothed sunspot number (SSN V2.0) after July 2015, we revisit the correlation of unsigned PMF and HMF at solar minimum. The correlation is used to estimate values of the HMF at the cycle 24 minimum and the amplitude of the upcoming cycle 25. The updated prediction is 134 ± 11 or 131 ± 11 on the revised SSN V2.0 scale assuming the cycle 24 minimum to occur in 2020 or 2021, respectively. The SSN values indicate that the cycle 25 will be stronger than cycle 24 and a little weaker than cycle 23, even if the current solar cycle minimum occurs in 2021 instead of 2020. This implies that we will witness another mini solar maximum in the upcoming cycle 25.

show abstract

Section: Heliospheric Magnetic Field (Hmf)mentioning

confidence: 99%

Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25

Janardhan

Ananthakrishnan

2020

JGR Space Physics

View full text Add to dashboard Cite

show abstract

“…These two series differ from one another before ≈1885. However, in the past century, they are similar, except for the period of very high solar activity (see Figure 2 of Cliver & Herbst 2018). The use of different reconstructions will lead to different results.…”

Section: Introductionmentioning

confidence: 96%

“…Over the past two decades, there has been much debate about different reconstructions of the SSN. There are mainly two sunspot records: the Wolf SSN, and the group SSN (see, e.g., Cliver & Herbst 2018). These two series differ from one another before ≈1885.…”

Section: Introductionmentioning

confidence: 99%

“…Several solar minima have been even quieter than the minimum of 2009/2010, and it is generally accepted from indirect observations that during the Maunder Minimum of 1645-1710, solar activity almost ceased (see, e.g., Riley et al 2015;Cliver & Herbst 2018, and references therein). These solar and heliospheric variations may therefore allow us to extrapolate the cosmic-ray intensity back for the last 400-500 yr. No systematic solar observations are available before that time.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Correlation of Long-term Cosmic-Ray Modulation with Solar Activity Parameters

Caballero─López

Engelbrecht

Richardson

2019

ApJ

View full text Add to dashboard Cite

In this work, we analyze the long-term cosmic-ray modulation observed by the Hermanus neutron monitor, which is the detector with the longest cosmic-ray record, from 1957 July. For our study we use the force-field approximation to the cosmic-ray transport equation, and the newest results on the mean free paths from the scattering theory. We compare the modulation parameter (f) with different rigidity (P) dependences: P, P 2 , and P 2/3. We correlate them with solar and interplanetary parameters. We found that (1) these rigidity dependences properly describe the modulation, (2) long-term cosmic-ray variations are better correlated with the magnitude of the heliospheric magnetic field (HMF) than the sunspot number, solar wind speed, and tilt angle of the HMF, and (3) the theoretical dependence of the parallel mean free path on the magnetic field variance is in agreement with the modulation parameter and therefore with the neutron monitor record. We also found that the force-field approximation is not able to take into account the effects of three-dimensional particle transport, showing a poor correlation with the perpendicular mean free path.

show abstract

“…Before such modern observations, the time series of the solar wind has been controversially reconstructed on the basis of multiple proxies such as the sunspot number, coronal structure, magnetic indices, and cosmogenic isotopes (Lockwood et al, 1999;Svalgaard and Cliver, 2005;Owens et al, 2017;Usoskin, 2017;Cliver and Herbst, 2018), including that of the Maunder Minimum (Cliver et al, 1998;Svalgaard and Cliver, 2007;McCracken and Beer, 2014;Riley et al, 2015;Usoskin et al, 2015;Owens et al, 2017). It is however challenging to extend its reconstruction before the onset of sunspot observations due to the limit of direct scientific observations (Vaquero and Vazquez, 2009;Owens, 2013), while ratio of the cosmogenic isotope show us its variability in lower time resolution on the basis of the anti-correlation between the solar-wind magnetic field and the source galactic cosmic rays (e.g., Beer et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Three case reports on the cometary plasma tail in the historical documents

Hayakawa

Fujii

Murata

et al. 2021

J. Space Weather Space Clim.

View full text Add to dashboard Cite

Cometary tails visually manifest the solar wind and became a first hint for its discovery. While the solar wind is being directly monitored with satellites, its time series before the space age has been controversially reconstructed with multiple proxies. Recently, cometary plasma tail observations have been subjected to consideration to indirectly measure the solar wind but brought conclusion that no plasma tail has been reported prior to 1769 probably due to their brightness. However, historical records have occasionally reported comets with two tails even before 1769 and these cases have been tentatively associated with visual reports of cometary plasma and dust tails. Therefore, we examined three such cases (C/1577 V1, 1P/837, and 1P/760), compared the descriptions in historical records with calculated direction of their plasma tails. Our comparisons show that the records and calculations agree in these cases and plasma tails were visually recorded corresponding to these three great comets. These cases certify the capability of plasma tail observations with the unaided eye even before 1769, qualitatively imply their extreme brightness, proximities with the Sun and the Earth, and relative enhancements of UV radiations and interaction of cometary neutral atmosphere with solar wind plasma and magnetic field, while the lack of their detailed length or kink hinders us from their quantitative measuring. Further investigations will probably lead to the re-discovery of even more visual evidence of cometary plasma tail and, hence, improve our understanding on past space climate.

show abstract

Evolution of the Sunspot Number and Solar Wind B $B$ Time Series

Cited by 12 publications

References 139 publications

Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25

Another Mini Solar Maximum in the Offing: A Prediction for the Amplitude of Solar Cycle 25

Correlation of Long-term Cosmic-Ray Modulation with Solar Activity Parameters

Three case reports on the cometary plasma tail in the historical documents

Contact Info

Product

Resources

About