Solar Activity Minimum Research Articles

A 1000-year record of centennial-scale cyclical vegetation change from Maar Lake Sanjiaolongwan in northeastern China

To examine possible relationships between regional changes in vegetation and climate and fluctuations in solar activity, we obtained a high-resolution 1000-year pollen record from the Sanjiaolongwan Maar Lake (SJML) in northeastern China. An age model was established using analyses of 210Pb, 137Cs and AMS 14C. The pollen assemblages indicate that during the last millennium the vegetation of the study area was temperate coniferous and deciduous broadleaved mixed forest. Although Pinus is the most abundant pollen type in the record, various lines of evidence suggest that it is not especially temperature-sensitive. However, the analysis of the changes in pollen assemblages over the past 1000 years, and a comparison with pollen records from other lakes in the region, indicate that the Quercus frequencies can be used as a relatively sensitive temperature index for the study area. Several notable cold periods, with lower Quercus frequencies, occurred at approximately 1200 AD, 1410 AD, 1580 AD, 1770 AD and 1870 AD. These centennial-scale cold periods basically correspond to major minima in solar activity, suggesting that variations in solar activity may have been an important driver of climate and vegetation change in the study area during the last millennium.

Features of horizontal magnetic field intensity over northern island of Malaysia

This study utilized magnetic field records of the horizontal component obtained from magnetic data acquisition system at northern island of Malaysia to delineate the diurnal variations of SqH and their monthly mean MSqH for a period of 4 years. The results show that for the entire period of study, the daytime SqH amplitudes increase from $$\sim 20$$ to $$\sim 160$$ nT and their MSqH amplitudes increased from $$\sim 40$$ to about 135 nT in 2008 to 2013, respectively. These variabilities of SqH and MSqH reached peak amplitudes between 10:00 and 12:00 LT hrs. The standard deviation fairly responds to the daily variability of SqH with a phase shift in January 2008 and 2013 which may likely have connection to the sudden stratospheric warming event that occurred in these months. We observed the extension of eastward field that continued beyond the sunset (18:00 LT) hours is more prevalent with higher magnitudes during the deep minimum solar activity and the probable causes are discussed. The observed counter equatorial electrojet associated with late reversal of night-time westward electric field (WEF) shows inverse relationship with increasing solar activity and those that are not associated to late reversal of night-time WEF seems to indicate linear relationship exception of deep minimum solar activity year (2008). We also observed a gradual shift of ECEJ to the morning sector with increasing solar activity. Throughout the years, days with stronger morning counter equatorial electrojet magnitudes generally weaken the expected strong eastward current and shifted its peak to earlier local time. The annual and seasonal variations of SqH show semiannual variation with equinoctial maxima and solstitial minima. About 40% of the SqH shows positive night-time to pre-sunrise variations which suggest the existence of weak electric currents not necessarily of ionospheric origin with appreciable influence at this longitude sector. The extension of eastward field beyond the sunset hours suggests likely modification of the evening side ionosphere over this region.

Investigation of exceptional solar activity in September 2017: GLE 72 and unusual Forbush decrease in GCR

The exceptional solar activity in early September 2017 at minimum of solar cycle 24 is analyzed. Intensive solar-terrestrial disturbances was caused by Active Region AR2673, which produced four powerful eruptions class X, including the strongest flare X9.3 of Solar Cycle 24 on September 6, 2017, after which began G4 – Severe geomagnetic storm on 07-08.09.2017 with Ap = 96, and also the second strongest flare X8.2 of Solar Cycle 24 on September 10, 2017, which generated Ground Level Enhancement (GLE) of cosmic rays. This was GLE72 with increase of solar cosmic ray flux 6% in Oulu Station (Finland) (effective vertical geomagnetic cutoff rigidity: 0.8 GV), and increase 9% in DOMC Antartica and 14% in DOMB Antartica (in the latter case - lead free neutron monitors with effective vertical cutoff rigidity <0.01 GV). The GLE72 develops under the conditions of a deep Forbush decrease (around 15%) in South Pole cusp caused by September 7th Coronal Mass Ejection. The Forbush effect ends on September 11th (http://cosmicrays.oulu.fi). But cosmic ray measurements by flying balloons to the stratosphere over California show that after solar eruptions in September 2017 the radiation levels in stratosphere took more than two months to fully rebound to the conditions of minimal solar activity. This is interesting fact which deserves to be explored in detail. It is precisely the study and interpretation of this process that is concerned with this work.

Solar coronal holes and their geo-effectiveness

Solar corona as the outermost part of the Sun is constantly emanating solar wind consisting of charged particles. Coronal holes are rigidly rotating phenomena in the solar corona that are magnetically open to interplanetary space, which allow the solar wind particles to escape from the Sun. The study of coronal holes and their associated high speed solar wind streams is important because they are the sources of space weather disturbances during minimum solar activity. We present some results on the relationship between large solar coronal holes close to the central meridian and solar wind stream with the aim to analyse their geo-effectiveness. The analysis were carried out by considering geomagnetic and solar wind parameters such as total geomagnetic field, Bz component, proton density and plasma speed during Earth-side large solar coronal holes appearance. Using the data during declining phase solar activity we found that a solar coronal hole is geo-effective during and after its transit on the central meridian but not all of them can be the proxy of high speed solar wind.

Correlation of the Radial and Meridional Components of IMF and the Solar Wind Velocity: Dependence on the Time and the Fluctuation Frequency

The behavior of the correlation between the radial BR and normal BN components of the interplanetary magnetic field (IMF) in the dependence on the time, the flow type of the solar wind, and the frequency of fluctuations has been studied with consideration of the peculiarities in IMF sectors of different signs. Based on the data of the Wind spacecraft obtained in 1995−2011, it has been found that the correlation between BR and BN is strongest in the periods of the solar activity minima and that the annual averages of the correlation coefficient obey the rules CRN > 0 or CRN < 0 northward or southward of the heliospheric current sheet, respectively. During the solar cycle, the correlation coefficient changes almost similarly in slow and fast solar wind streams. The dependence of the correlation between BR and BN on the fluctuation frequency was analyzed in a range of 1.2 × 10−5 to 8.3 × 10−3 Hz; it has been found that the correlation is maximal at low frequencies and that it slowly decreases, starting from 10−4 Hz, with increases in the frequency. It has been also found that, fluctuations in the components of the solar wind velocity VR and VN correlate analogously to the IMP components BR and BN at frequencies around 10−4 Hz or higher.

Application of wavelet analysis to the analysis of geomagnetic field variations

Wavelet analysis is becoming more popular in geophysics. It is used for numerous researches, including tropical convection, the El Nino-Southern Oscillation, atmospheric cold fronts, temperature variations, the dispersion of ocean waves, and coherent structures in turbulent flows, number of sunspots etc. In this paper we research how informative is the application of wavelet analysis to the analysis of geomagnetic field variations at the mid-latitude observatory “Mikhnevo” of Institute of Geosphere Dynamics of Russian Academy of Science. We review continuous wavelet transform by focusing attention on such aspects as choice of mother wavelet, choice of scales, cone of influence, visualization of results, reconstruction of time series from wavelet transform and its application to estimate the Holder exponents and singularity spectra. In our work we use Morlet wavelet with frequency parameter of 6. In so doing, the reconstruction of the time series from the wavelet transform has a mean square error of 3.4%. The application of wavelet analysis made it possible to distinguish pronounced periodicities of the geomagnetic field with periods of 27, 13.5, 9, 6 days. In solar quiet-day variations is dominated by the 24- 12-, 8-, and 6-hour period components. An analysis of the modulus of the wavelet transform coefficients qualitatively indicates a scaling (close to the monofractal) character of the variations of the geomagnetic field in the diurnal range. Moreover, the intensity of periodic variations of geomagnetic variation isn’t constant in time. The application of the method of wavelet transform modulus maxima confirmed the monofractal character of the diurnal variation for any solar activity. In contrast to the 1-day variation, the 27-day variation and its harmonics show a higher degree of multifractality during a maximum of solar activity in comparison with the minimum of solar activity.

Reconstruction of the Wolf Numbers Based on Radiocarbon Data from the Early 11th Century until the Middle of the 19th Century with Respect to Climate Changes

The results of the reconstruction of Wolf numbers from the 11th century until the middle of the 19th century A.D. based on radiocarbon data are presented. This time span includes the Oort, Wolf, Sporer, Maunder, and Dalton minima of solar activity, as well as the Medieval Solar Maximum (the 12th century and the first half of the 13th century A.D.) and the Late Medieval Maximum (the second half of the 14th century). It is known that the climate changed appreciably over the studied period: there were changes in the global temperature and in the concentration of carbon dioxide in the Earth’s atmosphere; more precisely, there was the Little Ice Age. This work differs from previous reconstructions of other authors in taking into account the influence of climate changes on the radiocarbon content in examined samples at that time span. During the reconstruction, changes in carbon dioxide content and changes in the regimen of carbon dioxide exchange between the ocean and the atmosphere are considered. It is especially important to consider changes in these parameters for the Little Ice Age, which was accompanied by significant changes in global temperature and the carbon dioxide content in the Earth’s atmosphere.

The Solar Wind and Heliospheric Current System in the Years of Maximum and Minimum Solar Activity

Within the axisymmetric MHD model of the solar wind, the magnetic field of the Sun has been analyzed in two phases of the solar cycle: the minimum activity, when the dipole magnetic field dominates and the maximum activity, when the quadrupole field predominates. It has been shown that during the period of maximum solar activity, the heliospheric current sheet acquires a conical shape and shifts to high latitudes up to 30° above the ecliptic plane. In the opposite hemisphere, at the same latitudes, a second current sheet of conical shape with an azimuth current of the opposite direction is established. It has been shown that the profiles of the main characteristics of the solar wind become steeper with distance from the Sun, and their amplitudes decrease, in this case, for the quadrupole field, the dependences of the main characteristics of the solar wind are more complex. A comparison of the results of the model with averaged characteristics of the solar wind shows a good match between the observed values and model parameters.

Evolution of the Solar Wind Speed with Heliocentric Distance and Solar Cycle. Surprises from Ulysses and Unexpectedness from Observations of the Solar Corona

An extensive analysis of Ulysses observations of the solar wind speed V from 1990 to 2008 is undertaken. It is shown that the evolution of V with heliocentric distance r depends substantially on both the heliolatitude and the solar activity cycle. Deviations from the predicted Parker's profile of V(r) are so considerable that cannot be explained by a scarcity of measurements or other technical effects. In particular, the expected smooth growth of the solar wind speed with r is typical only for the solar activity maximum and for low heliolatitudes (lower than +/-40deg), while at high latitudes, there are two V(r) branches: growing and falling. In the solar activity maximum, V increases toward the solar pole in the North hemisphere only; however, in the South hemisphere, it decreases with heliolatitude. In the minimum of solar activity, the profile of V(r) at low heliolatitudes has a local minimum between 2 and 5 AU. This result is confirmed by the corresponding data from other spacecraft (Voyager 1 and Pioneer 10). Unexpected spatial variations in V at low heliolatitudes can be explained by the impact of coronal hole flows on the V(r) profile since the flows incline to the ecliptic plane. To reproduce the impact of spatial variations of V in the polar corona on the behavior of V at low heliolatitudes, a stationary one-fluid ideal MHD-model is developed with account of recent results on imagery of the solar wind speed in the corona up to 5.5 solar radii obtained on the basis of combined observations from SOHO/UVCS, LASCO, and Mauna Loa.

Midlatitude Pc1 Geomagnetic Pulsations: Results of Observations and Statistical Estimates

An algorithm is developed for automated detection of the short-period Pc1 geomagnetic pulsations (frequency band f = 0.2–3 Hz) from the continuous time series of digital recording during 1998–2014 at the midlatitude Borok station. A digital catalog with the indication of time intervals of the presence and main morphological characteristics of Pc1 pulsations is created. Based on this catalog, the annual, seasonal, and diurnal dynamics of the midlatitude Pc1 pulsation activity is studied for 1998–2014. It is shown that the annual variation of the Pc1 occurrence has a maximum in 2005, i.e., at the end of the solar cycle decay phase, just as in the previous cycles. It is found that the minimum of the cases of Pc1 occurrence is observed in 2009, i.e., not at the maximum, just was the case in the previous cycles, but during the deep minimum of solar activity, which testifies to the untypical conditions in the magnetosphere during the unusually long minimum of the 23rd cycle. The seasonal variation of the Pc1 occurrence has a summer minimum when the series of Pc1 pulsations occur almost thrice as rarely as in winter. Besides, there are relatively small maxima at equinox. The diurnal behavior of Pc1 pulsations has the maxima in the morning and midnight sectors of the magnetosphere. By the superposed epoch analysis technique it is established that the maximal number of the cases of occurrence of Pc1 pulsations at the Borok observatory is observed on the fourth day after the global geomagnetic disturbances. The statistical distributions of pulsations amplitude and duration are obtained.

Cosmic Rays and Clouds Variations Effect on the Climate is Insignificantly

It is believed that an increase in the area of the cloud cover in the lower atmosphere of the Earth caused by the influence grows of galactic cosmic rays in the period of the Grand minimum of solar activity lead to an increase the reflected part of incoming solar radiation back into space and by that to a cooling of the climate down to the Little Ice Age. We will try to estimate an inverse aspect of simultaneously influence of increase in the area of the cloud cover in to the narrowing of the transmission of the windows of atmospheric transparency, which practically compensates of this cooling by means of accumulation of energy. An increase in the reflection of the thermal radiation of the Earth surface and of the solar radiation reflected from it, as well as the significant amplification of the greenhouse effect, presents an important additional source of heating due to the increase in the area of the cloud cover in the lower atmosphere. The impact of the increase in the area of the cloud cover caused by the influence grows of cosmic rays on the climate is very small.

High resolution monsoon precipitation changes on southeastern Tibetan Plateau over the past 2300 years

Climate changes on Southeastern Tibetan Plateau have important impacts on social and economic development, as well as the ecosystem of southwestern China and Indo-China Peninsula. Here, we collected two stalagmites from Shenqi (Miraculous) cave in southern Sichuan, China. The stalagmite δ18O record shows good coherence with local instrumental rainfall record, as well as tree ring- and pollen-based moisture reconstructions from southeastern Tibetan Plateau during overlapped time periods. As a result, we reconstructed high-resolution (∼4.9 yrs) monsoon precipitation variations on southeastern Tibetan Plateau over the past 2300 years by using the combined stalagmite δ18O record.The result reveals an overall decreasing precipitation trend, with two most notable wet periods occurred in 60–280 AD and 370–510 AD. The most remarkably dry period is the recent 200 years. Some decadal scale wet and dry intervals were also identified. The abnormal drought during 1160–1245 AD might have accelerated Dali kingdom's demise at 1253 AD. Power spectrum analysis indicated significant 373-, 187-, 22-, 12- and 11- yr cycles in our stalagmite record, suggesting the impact of solar activity. Increased monsoon precipitation on southeastern TP was observed in solar activity minima during the last millennium. We further synthesized an integrated precipitation record for southwestern China and discussed spatial patterns of precipitation over China during the last two millennia. The comparisons confirm a "dry southern and wet northern" pattern in monsoonal China during the Medieval Warm Period and a "wet southern and dry northern" pattern during the Little Ice Age and Dark Age Cold Period. Solar activity, the strength of westerly jet and summer monsoon, as well as the SST of tropical Indo-Pacific might play important roles on the rainfall spatial patterns over monsoonal China during the last 2000 years.

Galactic Cosmic-Ray Anisotropy in the Northern Hemisphere from the ARGO-YBJ Experiment during 2008–2012

Abstract This paper reports on the observation of the sidereal large-scale anisotropy of cosmic rays using data collected by the ARGO-YBJ experiment over 5 years (2008–2012). This analysis extends previous work limited to the period from 2008 January to 2009 December, near the minimum of solar activity between cycles 23 and 24. With the new data sample, the period of solar cycle 24 from near minimum to maximum is investigated. A new method is used to improve the energy reconstruction, allowing us to cover a much wider energy range, from 4 to 520 TeV. Below 100 TeV, the anisotropy is dominated by two wide regions, the so-called “tail-in” and “loss-cone” features. At higher energies, a dramatic change of the morphology is confirmed. The yearly time dependence of the anisotropy is investigated. Finally, no noticeable variation of cosmic-ray anisotropy with solar activity is observed for a median energy of 7 TeV.

The expected fluxes observed by STIX during low solar activity

The Spectrometer Telescope for Imaging X-rays (STIX) is one of the instruments installed onboard Solar Orbiter mission which will be launched in February 2020. After 1.5 years of cruise phase it will start to gather scientific data from the orbit with perihelion distance about 0.28 au. It means that STIX will operate also during the next solar minimum. In the paper we estimate flux measured by the instrument during periods of low solar activity. For this purpose we used solar observations which were recorded by the Solar Photometer in X-rays (SphinX) during the last minimum of solar activity. The estimation was obtained for instruments overlapping energy range from 4 to 15 keV. Presented results indicate that STIX instrument will provide efficient imaging the solar emission even during low level of solar activity (B1 GOES class).

Global Variations in Critical Frequency of the F2 Layer in Various Models of Solar EUV Radiation

The paper presents the results of modeling ionospheric parameters using the Global Self-Consistent Model of the Thermosphere, Ionosphere, and Protonosphere (GSM TIP) of the Earth. Numerical experiments have been performed for three variants of the solar EUV spectrum data: the Nusinov model, EUVAC, and generalized solar flux measurements (SOLID). The calculations have been carried out on March 22, 2009 (F10.7 ~ 68) and March 22, 2014 (F10.7 ~ 154). The maximum ionization rate and, correspondingly, the critical frequency of the F2 layer have been obtained using the Nusinov model for low and high solar activities. The lowest ionization rates and values of foF2 have been obtained using the EUVAC model. Simulations with the SOLID spectrum show the better agreement of foF2 with the empirical model IRI-2007 at the maximum solar activity. At the same time, at the minimum solar activity, all models of the spectrum provide an underestimation of the values of the critical frequency of the F2 layer.

A study of the geomagnetic indices asymmetry based on the interplanetary magnetic field polarities

Data of geomagnetic indices (aa, Kp, Ap, and Dst) recorded near 1 AU over the period 1967–2016, have been studied based on the asymmetry between the interplanetary magnetic field (IMF) directions above and below of the heliospheric current sheet (HCS). Our results led to the following conclusions: (i) Throughout the considered period, 31 random years (62%) showed apparent asymmetries between Toward ( $\mathbf{T}$ ) and Away ( $\mathbf{A}$ ) polarity days and 19 years (38%) exhibited nearly a symmetrical behavior. The days of $\mathbf{A}$ polarity predominated over the $\mathbf{T}$ polarity days by 4.3% during the positive magnetic polarity epoch (1991–1999). While the days of $\mathbf{T}$ polarity exceeded the days of $\mathbf{A}$ polarity by 5.8% during the negative magnetic polarity epoch (2001–2012). (ii) Considerable yearly North–South (N–S) asymmetries of geomagnetic indices observed throughout the considered period. (iii) The largest toward dominant peaks for $aa$ and $Ap$ indices occurred in 1995 near to minimum of solar activity. Moreover, the most substantial away dominant peaks for $aa$ and $Ap$ indices occurred in 2003 (during the descending phase of the solar cycle 23) and in 1991 (near the maximum of solar activity cycle) respectively. (iv) The N–S asymmetry of $Kp$ index indicated a most significant away dominant peak occurred in 2003. (v) Four of the away dominant peaks of Dst index occurred at the maxima of solar activity in the years 1980, 1990, 2000, and 2013. The largest toward dominant peak occurred in 1991 (at the reversal of IMF polarity). (vi) The geomagnetic indices (aa, Ap, and $Kp$ ) all have northern dominance during positive magnetic polarity epoch (1971–1979), while the asymmetries shifts to the southern solar hemisphere during negative magnetic polarity epoch (2001–2012).

THE INFLUENCE OF GEOGRAPHICAL LATITUDE ON THE NUMBER OF HOSPITALIZATIONS FOR CARDIOVASCULAR DISEASE IN YEARS WITH LOW AND HIGH GEOMAGNETIC ACTIVITY

The aim of this work was to establish the relationship between the dynamics of geomagnetic activity during 1998-2009 y.y. and dynamics of hospitalizations for cardiovascular diseases in the countries of Northern, Central and Southern Europe. In our study statistical data about hospitalizations for overall cardiovascular disease, ischemic heart disease and cerebrovascular disease were taken from the European health for all database. For the evaluation of geomagnetic activity values daily indices of geomagnetic activity were taken from the site of the Space weather prediction center. A direct relationship between the planetary geomagnetic activity and the number of hospitalizations for ischemic heart disease (IHD) in countries of Northern and Central Europe has been revealed. In addition, in the Nordic countries in a year with maximum solar activity, the number of hospitalizations for IHD was signifi cantly higher than in a year with minimal solar activity. In the countries of Southern Europe, there was no correlation between the solar activity and the number of hospitalizations for the studied cardiovascular diseases. It can be concluded that geomagnetic storms cause increase in the number of hospitalizations for IHD in the countries of Northern Europe. The infl uence of geomagnetic disturbances on the number of hospitalizations for IHD decreases with the decrease in geographical latitude.

Galactic Cosmic Ray Intensity in the Upcoming Minimum of the Solar Activity Cycle

During the prolonged and deep minimum of solar activity between cycles 23 and 24, an unusual behavior of the heliospheric characteristics and increased intensity of galactic cosmic rays (GCRs) near the Earth’s orbit were observed. The maximum of the current solar cycle 24 is lower than the previous one, and the decline in solar and, therefore, heliospheric activity is expected to continue in the next cycle. In these conditions, it is important for an understanding of the process of GCR modulation in the heliosphere, as well as for applied purposes (evaluation of the radiation safety of planned space flights, etc.), to estimate quantitatively the possible GCR characteristics near the Earth in the upcoming solar minimum (~2019–2020). Our estimation is based on the prediction of the heliospheric characteristics that are important for cosmic ray modulation, as well as on numeric calculations of GCR intensity. Additionally, we consider the distribution of the intensity and other GCR characteristics in the heliosphere and discuss the intercycle variations in the GCR characteristics that are integral for the whole heliosphere (total energy, mean energy, and charge).

Holocene climate aridification trend and human impact interrupted by millennial- and centennial-scale climate fluctuations from a new sedimentary record from Padul (Sierra Nevada, southern Iberian Peninsula)

Abstract. Holocene centennial-scale paleoenvironmental variability has been described in a multiproxy analysis (i.e., lithology, geochemistry, macrofossil, and microfossil analyses) of a paleoecological record from the Padul Basin in Sierra Nevada, southern Iberian Peninsula. This sequence covers a relevant time interval hitherto unreported in the studies of the Padul sedimentary sequence. The ∼ 4700-year record has preserved proxies of climate variability, with vegetation, lake levels, and sedimentological change during the Holocene in one of the most unique and southernmost wetlands in Europe. The progressive middle and late Holocene trend toward arid conditions identified by numerous authors in the western Mediterranean region, mostly related to a decrease in summer insolation, is also documented in this record; here it is also superimposed by centennial-scale variability in humidity. In turn, this record shows centennial-scale climate oscillations in temperature that correlate with well-known climatic events during the late Holocene in the western Mediterranean region, synchronous with variability in solar and atmospheric dynamics. The multiproxy Padul record first shows a transition from a relatively humid middle Holocene in the western Mediterranean region to more aridity from ∼ 4700 to ∼ 2800 cal yr BP. A relatively warm and humid period occurred between ∼ 2600 and ∼ 1600 cal yr BP, coinciding with persistent negative North Atlantic Oscillation (NAO) conditions and the historic Iberian–Roman Humid Period. Enhanced arid conditions, co-occurring with overall positive NAO conditions and increasing solar activity, are observed between ∼ 1550 and ∼ 450 cal yr BP (∼ 400 to ∼ 1400 CE) and colder and warmer conditions occurred during the Dark Ages and Medieval Climate Anomaly (MCA), respectively. Slightly wetter conditions took place during the end of the MCA and the first part of the Little Ice Age, which could be related to a change towards negative NAO conditions and minima in solar activity. Time series analysis performed from local (Botryococcus and total organic carbon) and regional (Mediterranean forest) signals helped us determining the relationship between southern Iberian climate evolution, atmospheric and oceanic dynamics, and solar activity. Our multiproxy record shows little evidence of human impact in the area until ∼ 1550 cal yr BP, when evidence of agriculture and livestock grazing occurs. Therefore, climate is the main forcing mechanism controlling environmental change in the area until relatively recently.

Forecasting the sunspot maximum through an analysis of geomagnetic activity

In the present work we show that it is possible to predict the maximum sunspot number for a particular solar cycle from the maximum value of the solar dipole magnetic field of the previous cycle. Based on the measured dipole field maximum, we determine the geomagnetic activity in the upcoming solar minimum during the intervals when the Earth is not exposed to CME and HSS influences. The physical meaning of the relationship between the geomagnetic activity in the solar activity minimum and the maximum value of the solar dipole magnetic field is that the basic factor determining the geomagnetic activity during the minimum is not the heliospheric current sheet thickness but the physical parameters of the slow solar wind in this period.Then, based on the established relationship between the average geomagnetic activity at the specified minimum and the next solar maximum, we can predict the sunspot maximum of the next solar cycle.