Status of Cycle 23 Forecasts

NASA Technical Reports Server (NTRS)

Hathaway, D. H.

2000-01-01

A number of techniques for predicting solar activity on a solar cycle time scale are identified, described, and tested with historical data. Some techniques, e.g,, regression and curve-fitting, work well as solar activity approaches maximum and provide a month- by-month description of future activity, while others, e.g., geomagnetic precursors, work well near solar minimum but provide an estimate only of the amplitude of the cycle. A synthesis of different techniques is shown to provide a more accurate and useful forecast of solar cycle activity levels. A combination of two uncorrelated geomagnetic precursor techniques provides the most accurate prediction for the amplitude of a solar activity cycle at a time well before activity minimum. This precursor method gave a smoothed sunspot number maximum of 154+21 for cycle 23. A mathematical function dependent upon the time of cycle initiation and the cycle amplitude then describes the level of solar activity for the complete cycle. As the time of cycle maximum approaches a better estimate of the cycle activity is obtained by including the fit between recent activity levels and this function. This Combined Solar Cycle Activity Forecast now gives a smoothed sunspot maximum of 140+20 for cycle 23. The success of the geomagnetic precursors in predicting future solar activity suggests that solar magnetic phenomena at latitudes above the sunspot activity belts are linked to solar activity, which occurs many years later in the lower latitudes.

The solar cycle dependence of the location and shape of the Venus bow shock

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, T.L.; Luhmann, J.G.; Russell, C.T.

1990-09-01

From initial Pioneer Venus observations during the maximum of solar cycle 21 it was evident that the position of the Venus bow shock varies with solar activity. The bow shock radius in the terminator plane changed from 2.4 R{sub v} to 2.1 R{sub v} as solar activity went from maximum to minimum and, as activity has increased in cycle 22, it has increased again. The recent studies of the subsolar region show that the altitude of the nose of the bow shock varies from 1,600 km at solar minimum to 2,200 km at intermediate solar activity in concert with themore » terminator altitude so that the shape remains constant and only the size varies during the solar cycle. Using a gas dynamic model and the observed bow shock location, the authors infer the variation in the size of the effective obstacle during the solar cycle. At solar maximum, the effective obstacle is larger than the ionopause as if a magnetic barrier exists in the inner magnetosheath. This magnetic barrier acts as the effective obstacle deflecting the magnetosheath plasma about 500 km above the surface of Venus. However, at solar minimum the effective obstacle is well below the subsolar ionopause, and some absorption of the solar wind plasma by the Venus neutral atmosphere is suggested by these observations. The dependence of the solar cycle variation of the shock position on the orientation of the interplanetary magnetic field reinforces the idea that planetary ion pickup is important in the interaction of the solar wind with Venus.« less

A Possible Cause of the Diminished Solar Wind During the Solar Cycle 23 - 24 Minimum

NASA Astrophysics Data System (ADS)

Liou, Kan; Wu, Chin-Chun

2016-12-01

Interplanetary magnetic field and solar wind plasma density observed at 1 AU during Solar Cycle 23 - 24 (SC-23/24) minimum were significantly smaller than those during its previous solar cycle (SC-22/23) minimum. Because the Earth's orbit is embedded in the slow wind during solar minimum, changes in the geometry and/or content of the slow wind region (SWR) can have a direct influence on the solar wind parameters near the Earth. In this study, we analyze solar wind plasma and magnetic field data of hourly values acquired by Ulysses. It is found that the solar wind, when averaging over the first (1995.6 - 1995.8) and third (2006.9 - 2008.2) Ulysses' perihelion ({˜} 1.4 AU) crossings, was about the same speed, but significantly less dense ({˜} 34 %) and cooler ({˜} 20 %), and the total magnetic field was {˜} 30 % weaker during the third compared to the first crossing. It is also found that the SWR was {˜} 50 % wider in the third ({˜} 68.5^deg; in heliographic latitude) than in the first ({˜} 44.8°) solar orbit. The observed latitudinal increase in the SWR is sufficient to explain the excessive decline in the near-Earth solar wind density during the recent solar minimum without speculating that the total solar output may have been decreasing. The observed SWR inflation is also consistent with a cooler solar wind in the SC-23/24 than in the SC-22/23 minimum. Furthermore, the ratio of the high-to-low latitude photospheric magnetic field (or equatorward magnetic pressure force), as observed by the Mountain Wilson Observatory, is smaller during the third than the first Ulysses' perihelion orbit. These findings suggest that the smaller equatorward magnetic pressure at the Sun may have led to the latitudinally-wider SRW observed by Ulysses in SC-23/24 minimum.

Chromospheric Signatures of the Subdued Cycle 23/24 Solar Minimum in Microwaves

NASA Technical Reports Server (NTRS)

Yashiro, S.; Makela, P.; Shibasaki, K.; Hathaway, D.

2011-01-01

Coronal holes appear brighter than the quiet Sun in microwave images, with a brightness enhancement of 500 to 2000 K. The brightness enhancement corresponds to the upper chromosphere, where the plasma temperature is about 10000 K. We constructed a microwave butterfly diagram using the synoptic images obtained by the Nobeyama radio-heliograph (NoRH) showing the evolution of the polar and low latitude brightness temperature. While the polar brightness reveals the chromospheric conditions, the low latitude brightness is attributed to active regions in the corona. When we compared the microwave butterfly diagram with the magnetic butterfly diagram, we found a good correlation between the microwave brightness enhancement and the polar field strength. The microwave butterfly diagram covers part of solar cycle 22, whole of cycle 23, and part of cycle 24, thus enabling comparison between the cycle 23/24 and cycle 22/23 minima. The microwave brightness during the cycle 23/24 minimum was found to be lower than that during the cycle 22/23 minimum by approx.250 K. The reduced brightness temperature is consistent with the reduced polar field strength during the cycle 23/24 minimum seen in the magnetic butterfly diagram. We suggest that the microwave brightness at the solar poles is a good indicator of the speed of the solar wind sampled by Ulysses at high latitudes.

Solar origins of solar wind properties during the cycle 23 solar minimum and rising phase of cycle 24

PubMed Central

Luhmann, Janet G.; Petrie, Gordon; Riley, Pete

2012-01-01

The solar wind was originally envisioned using a simple dipolar corona/polar coronal hole sources picture, but modern observations and models, together with the recent unusual solar cycle minimum, have demonstrated the limitations of this picture. The solar surface fields in both polar and low-to-mid-latitude active region zones routinely produce coronal magnetic fields and related solar wind sources much more complex than a dipole. This makes low-to-mid latitude coronal holes and their associated streamer boundaries major contributors to what is observed in the ecliptic and affects the Earth. In this paper we use magnetogram-based coronal field models to describe the conditions that prevailed in the corona from the decline of cycle 23 into the rising phase of cycle 24. The results emphasize the need for adopting new views of what is ‘typical’ solar wind, even when the Sun is relatively inactive. PMID:25685422

Implications of Extended Solar Minima

NASA Technical Reports Server (NTRS)

Adams, Mitzi L.; Davis, J. M.

2009-01-01

Since the discovery of periodicity in the solar cycle, the historical record of sunspot number has been carefully examined, attempting to make predictions about the next cycle. Much emphasis has been on predicting the maximum amplitude and length of the next cycle. Because current space-based and suborbital instruments are designed to study active phenomena, there is considerable interest in estimating the length and depth of the current minimum. We have developed criteria for the definition of a minimum and applied it to the historical sunspot record starting in 1749. In doing so, we find that 1) the current minimum is not yet unusually long and 2) there is no obvious way of predicting when, using our definition, the current minimum may end. However, by grouping the data into 22- year cycles there is an interesting pattern of extended minima that recurs every fourth or fifth 22-year cycle. A preliminary comparison of this pattern with other records, suggests the possibility of a correlation between extended minima and lower levels of solar irradiance.

A Synthesis of Solar Cycle Prediction Techniques

NASA Technical Reports Server (NTRS)

Hathaway, David H.; Wilson, Robert M.; Reichmann, Edwin J.

1999-01-01

A number of techniques currently in use for predicting solar activity on a solar cycle timescale are tested with historical data. Some techniques, e.g., regression and curve fitting, work well as solar activity approaches maximum and provide a month-by-month description of future activity, while others, e.g., geomagnetic precursors, work well near solar minimum but only provide an estimate of the amplitude of the cycle. A synthesis of different techniques is shown to provide a more accurate and useful forecast of solar cycle activity levels. A combination of two uncorrelated geomagnetic precursor techniques provides a more accurate prediction for the amplitude of a solar activity cycle at a time well before activity minimum. This combined precursor method gives a smoothed sunspot number maximum of 154 plus or minus 21 at the 95% level of confidence for the next cycle maximum. A mathematical function dependent on the time of cycle initiation and the cycle amplitude is used to describe the level of solar activity month by month for the next cycle. As the time of cycle maximum approaches a better estimate of the cycle activity is obtained by including the fit between previous activity levels and this function. This Combined Solar Cycle Activity Forecast gives, as of January 1999, a smoothed sunspot maximum of 146 plus or minus 20 at the 95% level of confidence for the next cycle maximum.

Using the Solar Polar Magnetic Field for Longterm Predictions of Solar Activity, Solar Cycles 21-25

NASA Astrophysics Data System (ADS)

Pesnell, W. D.; Schatten, K. H.

2017-12-01

We briefly review the dynamo and geomagnetic precursor methods of long-term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the amplification of pre-existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, to the Solar Dynamo Amplitude (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. We will show how effective the SODA Index has been in predicting Solar Cycles 23 and 24, and present a unified picture of earlier estimates of the polar magnetic configuration in Solar Cycle 21 and 22. Using the present value of the SODA index, we estimate that the next cycle's smoothed peak activity will be about 125 ± 30 solar flux units for the 10.7 cm radio flux and a sunspot number of 70 ± 25. This suggests that Solar Cycle 25 will be comparable to Solar Cycle 24. Since the current approach uses data prior to solar minimum, these estimates may improve when the upcoming solar minimum is reached.

Modulation of galactic cosmic rays in solar cycles 22-24: Analysis and physical interpretation

NASA Astrophysics Data System (ADS)

Kalinin, M. S.; Bazilevskaya, G. A.; Krainev, M. B.; Svirzhevskaya, A. K.; Svirzhevsky, N. S.; Starodubtsev, S. A.

2017-09-01

This work represents a physical interpretation of cosmic ray modulation in the 22nd-24th solar cycles, including an interpretation of an unusual behavior of their intensity in the last minimum of the solar activity (2008-2010). In terms of the Parker modulation model, which deals with regularly measured heliospheric characteristics, it is shown that the determining factor of the increased intensity of the galactic cosmic rays in the minimum of the 24th solar cycle is an anomalous reduction of the heliospheric magnetic field strength during this time interval under the additional influence of the solar wind velocity and the tilt angle of the heliospheric current sheet. We have used in the calculations the dependence of the diffusion tensor on the rigidity in the form K ij ∝ R 2-μ with μ = 1.2 in the sector zones of the heliospheric magnetic field and with μ = 0.8 outside the sector zones, which leads to an additional amplification of the diffusion mechanism of cosmic ray modulation. The proposed approach allows us to describe quite satisfactorily the integral intensity of protons with an energy above 0.1 GeV and the energy spectra in the minima of the 22nd-24th solar cycles at the same value of the free parameter. The determining factor of the anomalously high level of the galactic cosmic ray intensity in the minimum of the 24th solar cycle is the significant reduction of the heliospheric magnetic field strength during this time interval. The forecast of the intensity level in the minimum of the 25th solar cycle is provided.

Solar Modulation of Inner Trapped Belt Radiation Flux as a Function of Atmospheric Density

NASA Technical Reports Server (NTRS)

Lodhi, M. A. K.

2005-01-01

No simple algorithm seems to exist for calculating proton fluxes and lifetimes in the Earth's inner, trapped radiation belt throughout the solar cycle. Most models of the inner trapped belt in use depend upon AP8 which only describes the radiation environment at solar maximum and solar minimum in Cycle 20. One exception is NOAAPRO which incorporates flight data from the TIROS/NOAA polar orbiting spacecraft. The present study discloses yet another, simple formulation for approximating proton fluxes at any time in a given solar cycle, in particular between solar maximum and solar minimum. It is derived from AP8 using a regression algorithm technique from nuclear physics. From flux and its time integral fluence, one can then approximate dose rate and its time integral dose.

A Solar Cycle Prediction Puzzle's PossibleExplanation?

NASA Astrophysics Data System (ADS)

Luhmann, Janet

2007-05-01

A long-standing and intriguing puzzle of the last few decades has been Joan Feynman's (1982) discovery that the solar cycle (sunspot number) maximum trends follow the level of geomagnetic activity during the prior minimum phase. Recently Hathaway (GRL 33, 2006) used this relationship to make a prediction of the size of the next solar maximum. But the physical reason why this should work at all remains a matter of speculation. Although it has been suggested that geomagnetic activity around solar minimum is determined by the terrestrial magnetosphere's response to high speed solar wind streams which seem to often characterize the declining phase of the cycle, why should the occurrence of these streams portend the new solar maximum? Our improving understanding of solar wind sources may hold the key, and also tell us something useful about the solar dynamo.

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

NASA Astrophysics Data System (ADS)

Krainev, M. B.; Bazilevskaya, G. A.; Kalinin, M. S.; Svirzhevskaya, A. K.; Svirzhevskii, N. S.

2018-03-01

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).

An early solar dynamo prediction: Cycle 23 is approximately cycle 22

NASA Technical Reports Server (NTRS)

Schatten, Kenneth H.; Pesnell, W. Dean

1993-01-01

In this paper, we briefly review the 'dynamo' and 'geomagnetic precursor' methods of long-term solar activity forecasting. These methods depend upon the most basic aspect of dynamo theory to predict future activity, future magnetic field arises directly from the magnification of pre-existing magnetic field. We then generalize the dynamo technique, allowing the method to be used at any phase of the solar cycle, through the development of the 'Solar Dynamo Amplitude' (SODA) index. This index is sensitive to the magnetic flux trapped within the Sun's convection zone but insensitive to the phase of the solar cycle. Since magnetic fields inside the Sun can become buoyant, one may think of the acronym SODA as describing the amount of buoyant flux. Using the present value of the SODA index, we estimate that the next cycle's smoothed peak activity will be about 210 +/- 30 solar flux units for the 10.7 cm radio flux and a sunspot number of 170 +/- 25. This suggests that solar cycle #23 will be large, comparable to cycle #22. The estimated peak is expected to occur near 1999.7 +/- 1 year. Since the current approach is novel (using data prior to solar minimum), these estimates may improve when the upcoming solar minimum is reached.

Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum.

PubMed

Yamaguchi, Yasuhiko T; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi

2010-11-30

The Maunder Minimum (A.D. 1645-1715) is a useful period to investigate possible sun-climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ(18)O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun-climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ(14)C) and climate (δ(18)O) isotope records derived from annual tree rings. The tree-ring δ(18)O record in Japan shows distinct negative δ(18)O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ(18)O record and the GCR flux reconstructed by an ice-core (10)Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum.

Synchronized Northern Hemisphere climate change and solar magnetic cycles during the Maunder Minimum

PubMed Central

Yamaguchi, Yasuhiko T.; Yokoyama, Yusuke; Miyahara, Hiroko; Sho, Kenjiro; Nakatsuka, Takeshi

2010-01-01

The Maunder Minimum (A.D. 1645–1715) is a useful period to investigate possible sun–climate linkages as sunspots became exceedingly rare and the characteristics of solar cycles were different from those of today. Here, we report annual variations in the oxygen isotopic composition (δ18O) of tree-ring cellulose in central Japan during the Maunder Minimum. We were able to explore possible sun–climate connections through high-temporal resolution solar activity (radiocarbon contents; Δ14C) and climate (δ18O) isotope records derived from annual tree rings. The tree-ring δ18O record in Japan shows distinct negative δ18O spikes (wetter rainy seasons) coinciding with rapid cooling in Greenland and with decreases in Northern Hemisphere mean temperature at around minima of decadal solar cycles. We have determined that the climate signals in all three records strongly correlate with changes in the polarity of solar dipole magnetic field, suggesting a causal link to galactic cosmic rays (GCRs). These findings are further supported by a comparison between the interannual patterns of tree-ring δ18O record and the GCR flux reconstructed by an ice-core 10Be record. Therefore, the variation of GCR flux associated with the multidecadal cycles of solar magnetic field seem to be causally related to the significant and widespread climate changes at least during the Maunder Minimum. PMID:21076031

Quasi-Biennial Oscillation and Solar Cycle Influences over the Winter Arctic Simulated by the WACCM4 Model

NASA Astrophysics Data System (ADS)

Li, K. F.; Limpasuvan, T. L.; Limpasuvan, V.; Tung, K. K.; Yung, Y. L.

2017-12-01

Observations show that the quasi-biennial oscillation (QBO) and the 11-year solar cycle perturb the polar vortex via planetary wave convergence at high latitudes, a mechanism first proposed by Holton and Tan in 1980. Their perturbations lead to increases of stratospheric sudden warming events, and hence observable increases in temperature and ozone abundance in the polar vortex, during the easterly phase of QBO and the solar maximum. Here we simulate the changes in the polar atmosphere using the Whole Atmosphere Community Climate Model 4 (WACCM4) with the prescribed QBO and 11-year solar cycle forcing. The simulation is diagnosed in four groups: westerly QBO phase and solar minimum, westerly QBO phase and solar maximum, easterly QBO phase and solar minimum, and easterly QBO phase and solar maximum. The simulated changes in temperature and ozone are compared with satellite observations.

Intense Geomagnetic Storms of Solar Cycle 24 and Associated Energetics

NASA Astrophysics Data System (ADS)

Rawat, R.; Echer, E.; Gonzalez, W. D.

2013-12-01

Solar cycle 24 commenced in November 2008 following a deep solar minimum. The solar activity picked up gradually and consequently led to increase in geomagnetic activity during the ascending phase of new cycle. From the start of this cycle till July 2013, only 12 intense geomagnetic storms (Dst < -100 nT) have occurred. We investigate the solar wind-interplanetary drivers for these intense geomagnetic storms using satellite data. Total energy Poynting flux (ɛ) representing the fraction of solar wind energy transferred into the magnetosphere during different storms will be calculated. Solar cycle 24 is weaker as compared to previous solar cycle (23). In this work, a comparative study of solar and geomagnetic signatures during the ascending phase of the two cycles will be carried out.

The radial distribution of cosmic rays in the heliosphere at solar maximum

NASA Astrophysics Data System (ADS)

McDonald, F. B.; Fujii, Z.; Heikkila, B.; Lal, N.

2003-08-01

To obtain a more detailed profile of the radial distribution of galactic (GCRs) and anomalous (ACRs) cosmic rays, a unique time in the 11-year solar activity cycle has been selected - that of solar maximum. At this time of minimum cosmic ray intensity a simple, straight-forward normalization technique has been found that allows the cosmic ray data from IMP 8, Pioneer 10 (P-10) and Voyagers 1 and 2 (V1, V2) to be combined for the solar maxima of cycles 21, 22 and 23. This combined distribution reveals a functional form of the radial gradient that varies as G 0/r with G 0 being constant and relatively small in the inner heliosphere. After a transition region between ˜10 and 20 AU, G 0 increases to a much larger value that remains constant between ˜25 and 82 AU. This implies that at solar maximum the changes that produce the 11-year modulation cycle are mainly occurring in the outer heliosphere between ˜15 AU and the termination shock. These observations are not inconsistent with the concept that Global Merged Interaction. regions (GMIRs) are the principal agent of modulation between solar minimum and solar maximum. There does not appear to be a significant change in the amount of heliosheath modulation occurring between the 1997 solar minimum and the cycle 23 solar maximum.

Radio Imaging Observations of Solar Activity Cycle and Its Anomaly

NASA Astrophysics Data System (ADS)

Shibasaki, K.

2011-12-01

The 24th solar activity cycle has started and relative sunspot numbers are increasing. However, their rate of increase is rather slow compared to previous cycles. Active region sizes are small, lifetime is short, and big (X-class) flares are rare so far. We study this anomalous situation using data from Nobeyama Radioheliograph (NoRH). Radio imaging observations have been done by NoRH since 1992. Nearly 20 years of daily radio images of the Sun at 17 GHz are used to synthesize a radio butterfly diagram. Due to stable operation of the instrument and a robust calibration method, uniform datasets are available covering the whole period of observation. The radio butterfly diagram shows bright features corresponding to active region belts and their migration toward low latitude as the solar cycle progresses. In the present solar activity cycle (24), increase of radio brightness is delayed and slow. There are also bright features around both poles (polar brightening). Their brightness show solar cycle dependence but peaks around solar minimum. Comparison between the last minimum and the previous one shows decrease of its brightness. This corresponds to weakening of polar magnetic field activity between them. In the northern pole, polar brightening is already weakened in 2011, which means it is close to solar maximum in the northern hemisphere. Southern pole does not show such feature yet. Slow rise of activity in active region belt, weakening of polar activity during the minimum, and large north-south asymmetry in polar activity imply that global solar activity and its synchronization are weakening.

UNUSUAL TRENDS IN SOLAR P-MODE FREQUENCIES DURING THE CURRENT EXTENDED MINIMUM

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tripathy, S. C.; Jain, K.; Hill, F.

2010-03-10

We investigate the behavior of the intermediate-degree mode frequencies of the Sun during the current extended minimum phase to explore the time-varying conditions in the solar interior. Using contemporaneous helioseismic data from the Global Oscillation Network Group (GONG) and the Michelson Doppler Imager (MDI), we find that the changes in resonant mode frequencies during the activity minimum period are significantly greater than the changes in solar activity as measured by different proxies. We detect a seismic minimum in MDI p-mode frequency shifts during 2008 July-August but no such signature is seen in mean shifts computed from GONG frequencies. We alsomore » analyze the frequencies of individual oscillation modes from GONG data as a function of latitude and observe a signature of the onset of the solar cycle 24 in early 2009. Thus, the intermediate-degree modes do not confirm the onset of the cycle 24 during late 2007 as reported from the analysis of the low-degree Global Oscillations at Low Frequency frequencies. Further, both the GONG and MDI frequencies show a surprising anti-correlation between frequencies and activity proxies during the current minimum, in contrast to the behavior during the minimum between cycles 22 and 23.« less

SOLAR WIND HEAVY IONS OVER SOLAR CYCLE 23: ACE/SWICS MEASUREMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lepri, S. T.; Landi, E.; Zurbuchen, T. H.

2013-05-01

Solar wind plasma and compositional properties reflect the physical properties of the corona and its evolution over time. Studies comparing the previous solar minimum with the most recent, unusual solar minimum indicate that significant environmental changes are occurring globally on the Sun. For example, the magnetic field decreased 30% between the last two solar minima, and the ionic charge states of O have been reported to change toward lower values in the fast wind. In this work, we systematically and comprehensively analyze the compositional changes of the solar wind during cycle 23 from 2000 to 2010 while the Sun movedmore » from solar maximum to solar minimum. We find a systematic change of C, O, Si, and Fe ionic charge states toward lower ionization distributions. We also discuss long-term changes in elemental abundances and show that there is a {approx}50% decrease of heavy ion abundances (He, C, O, Si, and Fe) relative to H as the Sun went from solar maximum to solar minimum. During this time, the relative abundances in the slow wind remain organized by their first ionization potential. We discuss these results and their implications for models of the evolution of the solar atmosphere, and for the identification of the fast and slow wind themselves.« less

Changes in the relationship NAO-Northern hemisphere temperature due to solar activity

NASA Astrophysics Data System (ADS)

Gimeno, Luis; de la Torre, Laura; Nieto, Raquel; García, Ricardo; Hernández, Emiliano; Ribera, Pedro

2003-01-01

The influence of the North Atlantic Oscillation (NAO) on wintertime Northern Hemisphere Temperature (NHT) is investigated. The results suggest that this relationship has different sign according to the phase of the solar cycle. For solar maximum phases NAO and NHT are positively correlated - a result assumed up to the moment - but for solar minimum phases correlations are not significant or even negative. This result is in agreement with the different extension of the NAO for solar cycle phases [Kodera, Geophys. Res. Lett. 29 (2002) 14557-14560] - almost hemispheric for maximum phases and confined to the eastern Atlantic for minimum phases.

Solar activities and Climate change hazards

NASA Astrophysics Data System (ADS)

Hady, A. A., II

2014-12-01

Throughout the geological history of Earth, climate change is one of the recurrent natural hazards. In recent history, the impact of man brought about additional climatic change. Solar activities have had notable effect on palaeoclimatic changes. Contemporary, both solar activities and building-up of green-house gases effect added to the climatic changes. This paper discusses if the global worming caused by the green-house gases effect will be equal or less than the global cooling resulting from the solar activities. In this respect, we refer to the Modern Dalton Minimum (MDM) which stated that starting from year 2005 for the next 40 years; the earth's surface temperature will become cooler than nowadays. However the degree of cooling, previously mentioned in old Dalton Minimum (c. 210 y ago), will be minimized by building-up of green-house gases effect during MDM period. Regarding to the periodicities of solar activities, it is clear that now we have a new solar cycle of around 210 years. Keywords: Solar activities; solar cycles; palaeoclimatic changes; Global cooling; Modern Dalton Minimum.

Properties of the suprathermal heavy ion population near 1 AU during solar cycles 23 and 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dayeh, Maher A., E-mail: maldayeh@swri.edu; Ebert, Robert W.; Desai, Mihir I.

2016-03-25

Using measurements from the Advanced Composition Explorer/Ultra-Low Energy Isotope Spectrometer (ACE/ULEIS) near 1 AU, we surveyed the composition and spectra of heavy ions (He-through-Fe) during interplanetary quiet times from 1998 January 1 to 2014 December 31 at suprathermal energies between ∼0.11 and ∼1.28 MeV nucleon{sup −1}. The selected time period covers the maxima of solar cycles 23 and 24 and the extended solar minimum in between. We find the following: (1) The number of quiet-hours in each year correlates well with the sunspot number, year 2009 was the quietest for about 90% of the time; (2) The composition of the quiet-timemore » suprathermal heavy ion population ({sup 3}He, C-through-O, and Fe) correlates well with the level of solar activity, exhibiting SEP-like composition signatures during solar maximum, and CIR- or solar wind-like composition during solar minimum; (3) The heavy ion spectra at ∼0.11-0.32 MeV nucleon{sup −1} exhibit suprathermal tails with power-law spectral indices ranging from 1.4 to 2.7. (4) Fe spectral indices get softer (steeper) from solar minimum of cycle 23 to solar cycle 24 maximum. These results imply that during IP quiet times and at energies above ∼0.1 MeV nucleon{sup −1}, the IP medium is dominated by material from prior solar and interplanetary events.« less

Quiet-Time Suprathermal ( 0.1-1.5 keV) Electrons in the Solar Wind

NASA Astrophysics Data System (ADS)

Wang, L.; Tao, J.; Zong, Q.; Li, G.; Salem, C. S.; Wimmer-Schweingruber, R. F.; He, J.; Tu, C.; Bale, S. D.

2016-12-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND/3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

Quiet-time Suprathermal (~0.1-1.5 keV) Electrons in the Solar Wind

NASA Astrophysics Data System (ADS)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang; Li, Gang; Salem, Chadi S.; Wimmer-Schweingruber, Robert F.; He, Jiansen; Tu, Chuanyi; Bale, Stuart D.

2016-03-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ˜0.1-1.5 keV to a Kappa distribution function with an index κ and effective temperature Teff. We also calculate the number density n and average energy Eavg of strahl and halo electrons by integrating the electron measurements between ˜0.1 and 1.5 keV. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity).

SOLAR CYCLE 25: ANOTHER MODERATE CYCLE?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cameron, R. H.; Schüssler, M.; Jiang, J., E-mail: cameron@mps.mpg.de

2016-06-01

Surface flux transport simulations for the descending phase of Cycle 24 using random sources (emerging bipolar magnetic regions) with empirically determined scatter of their properties provide a prediction of the axial dipole moment during the upcoming activity minimum together with a realistic uncertainty range. The expectation value for the dipole moment around 2020 (2.5 ± 1.1 G) is comparable to that observed at the end of Cycle 23 (about 2 G). The empirical correlation between the dipole moment during solar minimum and the strength of the subsequent cycle thus suggests that Cycle 25 will be of moderate amplitude, not muchmore » higher than that of the current cycle. However, the intrinsic uncertainty of such predictions resulting from the random scatter of the source properties is considerable and fundamentally limits the reliability with which such predictions can be made before activity minimum is reached.« less

The investigation of solar activity signals by analyzing of tree ring chronological scales

NASA Astrophysics Data System (ADS)

Nickiforov, M. G.

2017-07-01

The present study examines the ability of detecting short-cycles and global minima of solar activity by analyzing dendrochronologies. Starting with the study of Douglass, which was devoted to the question of climatic cycles and the growth of trees, it is believed that the analysis of dendrochronologies allows to detect the cycle of Wolf-Schwabe. According to his results, the cycle was absent during Maunder's minimum and appeared after its completion. Having checked Douglass's conclusions by using 10 dendrochronologies of yellow pines from Arizona, which cover the time period from 1600 to 1900, we have come to the opposite results. The verification shows that: a) none of the considered dendroscale allows to detect an 11-year cycle; 2) the behaviour of a short peroid-signal does not undergo significant changes before, during or after Maunder's minimum. A similar attempt to detect global minima of solar activity by using five dendrochronologies from different areas has not led to positive results. On the one hand, the signal of global extremum is not always recorded in dendrochronology, on the other hand, the deep depression of annual rings allows to suppose the existence of a global minimum of solar activity, which is actually absent.

Changes in the relationship NAO-Northern Hemisphere Temperature due to solar activity

NASA Astrophysics Data System (ADS)

de La Torre, L.; Gimeno, L.; Añel, J. A.; Nieto, R.; Tesouro, M.; Ribera, P.; García, R.; Hernández, E.

2003-04-01

The influence of the North Atlantic Oscillation (NAO) on wintertime Northern Hemisphere Temperature (NHT) is investigated. To check the hypothesis that the solar cycle is modulating this relationship, the sample was divided into two groups, one included the years corresponding to the three consecutive lowest values of sunspots number for every 11-years cycle (43 years) and the other the ones corresponding to the three consecutive highest numbers (39 years) for every 11-years cycle. If the data of each year were independent, the correlation coefficients between NAO index and NHT for 43 (39) years would be 0.30 (0.32) at 95% confidence level. Correlation index corresponding to the solar minimum phases was -0.17 and to the solar maximum phases was 0.35. The second result is statistically significant and indicates that there are periods when a positive phase of the NAO is related to positive anomalies of NHT- result that supports our current idea of the influence of the NAO on temperature- but there are other periods when NAO and NHT are not correlated. So, results suggest that this relationship has different sign according to the phase of the solar cycle. For solar maximum phases NAO and NHT are positively correlated -result assumed up to the moment- but for solar minimum phases correlations are not significant or even negative. This result is in agreement with the different extension of the NAO for solar cycle phases [1] - almost hemispheric for maximum phases and confined to the eastern Atlantic for minimum phases-.

Examination of Solar Cycle Statistical Model and New Prediction of Solar Cycle 23

NASA Technical Reports Server (NTRS)

Kim, Myung-Hee Y.; Wilson, John W.

2000-01-01

Sunspot numbers in the current solar cycle 23 were estimated by using a statistical model with the accumulating cycle sunspot data based on the odd-even behavior of historical sunspot cycles from 1 to 22. Since cycle 23 has progressed and the accurate solar minimum occurrence has been defined, the statistical model is validated by comparing the previous prediction with the new measured sunspot number; the improved sunspot projection in short range of future time is made accordingly. The current cycle is expected to have a moderate level of activity. Errors of this model are shown to be self-correcting as cycle observations become available.

Solar-Cycle Variability of Magnetosheath Fluctuations at Earth and Venus

NASA Astrophysics Data System (ADS)

Dwivedi, N. K.; Narita, Y.; Kovacs, P.

2014-12-01

The magnetosheath is a region between the bow-shock and magnetopause and the magnetosheath plasma is mostly in the turbulent state. In the present investigation we put an effort to closely examine the magnetosheath fluctuations dependency on the solar-cycles (solar-maximum and solar minimum) at the magnetized planetary body (Earth) and their comparison with the un-magnetized planetary body (Venus) for the solar minimum. We use the CLUSTER FGM data for the solar-maximum (2001-2002), solar-minimum (2006-2008) and Venus fluxgate magnetometer data for the solar-minimum (2006-2008) to perform a comparative statistical study on the energy spectra and probability density function (PDF) and asses the spectral features of the magnetic fluctuations of the both planetary bodies. In the comparison we study the relation between the inertial ranges of the spectra and the temporal scales of non-Gaussian magnetic fluctuations derived from PDF analyses. The first can refer to turbulent cascade dynamics, while the latter may indicate intermittency. We first transformed the magnetic field data into mean field aligned coordinate system with respect to the large-scale magnetic field direction and then after we compute the power spectral density with the help of Welch algorithm. The computed energy spectra of Earth's magnetosheath show a moderate variability with the solar-cycles and have a broader inertial range. However the estimated energy spectra for the solar-minimum at Venus give the clear evidence of the existence of the break point in the vicinity of the ion gyroradius. After the break-point the energy spectra become steeper and show a distinctive spectral scales which is interpreted as the realization of the begging of the energy cascade. We also briefly address the influence of turbulence on the plasma transport and wave dynamics responsible for the spectral break and predict spectral features of the energy spectra for the solar-maximum at Venus based on the results obtained for the solar-minimum. The research leading to these results has received funding from the European Community's Seventh Framework Programme ([FP7/2007-2013]) under grant agreement number 313038/STORM.

Forecasting the peak of the present solar activity cycle 24

NASA Astrophysics Data System (ADS)

Hamid, R. H.; Marzouk, B. A.

2018-06-01

Solar forecasting of the level of sun Activity is very important subject for all space programs. Most predictions are based on the physical conditions prevailing at or before the solar cycle minimum preceding the maximum in question. Our aim is to predict the maximum peak of cycle 24 using precursor techniques in particular those using spotless event, geomagnetic aamin. index and solar flux F10.7. Also prediction of exact date of the maximum (Tr) is taken in consideration. A study of variation over previous spotless event for cycles 7-23 and that for even cycles (8-22) are carried out for the prediction. Linear correlation between maximum of solar cycles (RM) and spotless event around the preceding minimum gives R24t = 88.4 with rise time Tr = 4.6 years. For the even cycles R24E = 77.9 with rise time Tr = 4.5 y's. Based on the average aamin. index for cycles (12-23), we estimate the expected amplitude for cycle 24 to be Raamin = 99.4 and 98.1 with time rise of Traamin = 4.04 & 4.3 years for both the total and even cycles in consecutive. The application of the data of solar flux F10.7 which cover only cycles (19-23) was taken in consideration and gives predicted maximum amplitude R24 10.7 = 126 with rise time Tr107 = 3.7 years, which are over estimation. Our result indicating to somewhat weaker of cycle 24 as compared to cycles 21-23.

Analysis of regression methods for solar activity forecasting

NASA Technical Reports Server (NTRS)

Lundquist, C. A.; Vaughan, W. W.

1979-01-01

The paper deals with the potential use of the most recent solar data to project trends in the next few years. Assuming that a mode of solar influence on weather can be identified, advantageous use of that knowledge presumably depends on estimating future solar activity. A frequently used technique for solar cycle predictions is a linear regression procedure along the lines formulated by McNish and Lincoln (1949). The paper presents a sensitivity analysis of the behavior of such regression methods relative to the following aspects: cycle minimum, time into cycle, composition of historical data base, and unnormalized vs. normalized solar cycle data. Comparative solar cycle forecasts for several past cycles are presented as to these aspects of the input data. Implications for the current cycle, No. 21, are also given.

Prediction of the total cycle 24 of solar activity by several autoregressive methods and by the precursor method

NASA Astrophysics Data System (ADS)

Ozheredov, V. A.; Breus, T. K.; Obridko, V. N.

2012-12-01

As follows from the statement of the Third Official Solar Cycle 24 Prediction Panel created by the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the International Space Environment Service (ISES) based on the results of an analysis of many solar cycle 24 predictions, there has been no consensus on the amplitude and time of the maximum. There are two different scenarios: 90 units and August 2012 or 140 units and October 2011. The aim of our study is to revise the solar cycle 24 predictions by a comparative analysis of data obtained by three different methods: the singular spectral method, the nonlinear neural-based method, and the precursor method. As a precursor for solar cycle 24, we used the dynamics of the solar magnetic fields forming solar spots with Wolf numbers Rz. According to the prediction on the basis of the neural-based approach, it was established that the maximum of solar cycle 24 is expected to be 70. The precursor method predicted 50 units for the amplitude and April of 2012 for the time of the maximum. In view of the fact that the data used in the precursor method were averaged over 4.4 years, the amplitude of the maximum can be 20-30% larger (i.e., around 60-70 units), which is close to the values predicted by the neural-based method. The protracted minimum of solar cycle 23 and predicted low values of the maximum of solar cycle 24 are reminiscent of the historical Dalton minimum.

QUIET-TIME SUPRATHERMAL (∼0.1–1.5 keV) ELECTRONS IN THE SOLAR WIND

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tao, Jiawei; Wang, Linghua; Zong, Qiugang

2016-03-20

We present a statistical survey of the energy spectrum of solar wind suprathermal (∼0.1–1.5 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. After separating (beaming) strahl electrons from (isotropic) halo electrons according to their different behaviors in the angular distribution, we fit the observed energy spectrum of both strahl and halo electrons at ∼0.1–1.5 keV to a Kappa distribution function with an index κ and effective temperature T{sub eff}. We also calculate the number density n and average energy E{sub avg} of strahl andmore » halo electrons by integrating the electron measurements between ∼0.1 and 1.5 keV. We find a strong positive correlation between κ and T{sub eff} for both strahl and halo electrons, and a strong positive correlation between the strahl n and halo n, likely reflecting the nature of the generation of these suprathermal electrons. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. The halo κ is generally smaller than the strahl κ (except during the solar minimum of cycle 23). The strahl n is larger at solar maximum, but the halo n shows no difference between solar minimum and maximum. Both the strahl n and halo n have no clear association with the solar wind core population, but the density ratio between the strahl and halo roughly anti-correlates (correlates) with the solar wind density (velocity)« less

Effects of meridional flow variations on solar cycles 23 and 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Upton, Lisa; Hathaway, David H., E-mail: lisa.a.upton@vanderbilt.edu, E-mail: lar0009@uah.edu, E-mail: david.hathaway@nasa.gov

2014-09-10

The faster meridional flow that preceded the solar cycle 23/24 minimum is thought to have led to weaker polar field strengths, producing the extended solar minimum and the unusually weak cycle 24. To determine the impact of meridional flow variations on the sunspot cycle, we have simulated the Sun's surface magnetic field evolution with our newly developed surface flux transport model. We investigate three different cases: a constant average meridional flow, the observed time-varying meridional flow, and a time-varying meridional flow in which the observed variations from the average have been doubled. Comparison of these simulations shows that the variationsmore » in the meridional flow over cycle 23 have a significant impact (∼20%) on the polar fields. However, the variations produced polar fields that were stronger than they would have been otherwise. We propose that the primary cause of the extended cycle 23/24 minimum and weak cycle 24 was the weakness of cycle 23 itself—with fewer sunspots, there was insufficient flux to build a big cycle. We also find that any polar counter-cells in the meridional flow (equatorward flow at high latitudes) produce flux concentrations at mid-to-high latitudes that are not consistent with observations.« less

Influence of geomagnetic activity and atmospheric pressure on human arterial pressure during the solar cycle 24

NASA Astrophysics Data System (ADS)

Azcárate, T.; Mendoza, B.; Levi, J. R.

2016-11-01

We performed a study of the systolic (SBP) and diastolic (DBP) arterial blood pressure behavior under natural variables such as the atmospheric pressure (AtmP) and the horizontal geomagnetic field component (H). We worked with a sample of 304 healthy normotense volunteers, 152 men and 152 women, with ages between 18 and 84 years in Mexico City during the period 2008-2014, corresponding to the minimum, ascending and maximum phases of the solar cycle 24. The data was divided by gender, age and day/night cycle. We studied the time series using three methods: Correlations, bivariate and superposed epochs (within a window of three days around the day of occurrence of a geomagnetic storm) analysis, between the SBP and DBP and the natural variables (AtmP and H). The correlation analysis indicated correlation between the SBP and DBP and AtmP and H, being the largest during the night. Furthermore, the correlation and bivariate analysis showed that the largest correlations are between the SBP and DBP and the AtmP. The superposed epoch analysis found that the largest number of significant SBP and DBP changes occurred for women. Finally, the blood pressure changes are larger during the solar minimum and ascending solar cycle phases than during the solar maximum; the storms of the minimum were more intense than those of the maximum and this could be the reason of behavior of the blood pressure changes along the solar cycle.

Solar Energetic Particle Composition over Two Solar Cycles as Observed by the Ulysses/HISCALE and ACE/EPAM Pulse Height Analyzers.

NASA Astrophysics Data System (ADS)

Patterson, J. D.; Madanian, H.; Manweiler, J. W.; Lanzerotti, L. J.

2017-12-01

We present the compositional variation in the Solar Energetic Particle (SEP) population in the inner heliosphere over two solar cycles using data from the Ulysses Heliospheric Instrument for Spectra, Composition, and Anisotropy at Low Energies (HISCALE) and Advanced Composition Explorer (ACE) Electron Proton Alpha Monitor (EPAM). The Ulysses mission was active from late 1990 to mid-2009 in a heliopolar orbit inclined by 80° with a perihelion of 1.3 AU and an aphelion of 5.4 AU. The ACE mission has been active since its launch in late 1997 and is in a halo orbit about L1. These two missions provide a total of 27 years of continuous observation in the inner heliosphere with twelve years of simultaneous observation. HISCALE and EPAM data provide species-resolved differential flux and density of SEP between 0.5-5 MeV/nuc. Several ion species (He, C, O, Ne, Si, Fe) are identified using the Pulse Height Analyzer (PHA) system of the Composition Aperture for both instruments. The He density shows a noticeable increase at high solar activity followed by a moderate drop at the quiet time of the solar minimum between cycles 23 and 24. The density of heavier ions (i.e. O and Fe) change minimally with respect to the F10.7 index variations however, certain energy-specific count rates decrease during solar minimum. With Ulysses and ACE observing in different regions of the inner heliosphere, there are significant latitudinal differences in how the O/He ratios vary with the solar cycle. At solar minimum, there is reasonable agreement between the observations from both instruments. At solar max 23, the differences in composition over the course of the solar cycle, and as observed at different heliospheric locations can provide insight to the origins of and acceleration processes differentially affecting solar energetic ions.

Proton Fluxes Measured by the PAMELA Experiment from the Minimum to the Maximum Solar Activity for Solar Cycle 24

NASA Astrophysics Data System (ADS)

Martucci, M.; Munini, R.; Boezio, M.; Di Felice, V.; Adriani, O.; Barbarino, G. C.; Bazilevskaya, G. A.; Bellotti, R.; Bongi, M.; Bonvicini, V.; Bottai, S.; Bruno, A.; Cafagna, F.; Campana, D.; Carlson, P.; Casolino, M.; Castellini, G.; De Santis, C.; Galper, A. M.; Karelin, A. V.; Koldashov, S. V.; Koldobskiy, S.; Krutkov, S. Y.; Kvashnin, A. N.; Leonov, A.; Malakhov, V.; Marcelli, L.; Marcelli, N.; Mayorov, A. G.; Menn, W.; Mergè, M.; Mikhailov, V. V.; Mocchiutti, E.; Monaco, A.; Mori, N.; Osteria, G.; Panico, B.; Papini, P.; Pearce, M.; Picozza, P.; Ricci, M.; Ricciarini, S. B.; Simon, M.; Sparvoli, R.; Spillantini, P.; Stozhkov, Y. I.; Vacchi, A.; Vannuccini, E.; Vasilyev, G.; Voronov, S. A.; Yurkin, Y. T.; Zampa, G.; Zampa, N.; Potgieter, M. S.; Raath, J. L.

2018-02-01

Precise measurements of the time-dependent intensity of the low-energy (<50 GeV) galactic cosmic rays (GCRs) are fundamental to test and improve the models that describe their propagation inside the heliosphere. In particular, data spanning different solar activity periods, i.e., from minimum to maximum, are needed to achieve comprehensive understanding of such physical phenomena. The minimum phase between solar cycles 23 and 24 was peculiarly long, extending up to the beginning of 2010 and followed by the maximum phase, reached during early 2014. In this Letter, we present proton differential spectra measured from 2010 January to 2014 February by the PAMELA experiment. For the first time the GCR proton intensity was studied over a wide energy range (0.08–50 GeV) by a single apparatus from a minimum to a maximum period of solar activity. The large statistics allowed the time variation to be investigated on a nearly monthly basis. Data were compared and interpreted in the context of a state-of-the-art three-dimensional model describing the GCRs propagation through the heliosphere.

H-alpha synoptic charts of solar activity during the first year of solar cycle 20, October 1964 - August 1965. [Skylab program

NASA Technical Reports Server (NTRS)

Mcintosh, P. S.

1975-01-01

Solar activity during the period October 28, 1964 through August 27, 1965 is presented in the form of charts for each solar rotation constructed from observations made with the chromospheric H-alpha spectra line. These H-alpha synoptic charts are identical in format and method of construction to those published for the period of Skylab observations. The sunspot minimum marking the start of Solar Cycle 20 occurred in October, 1964; therefore, charts represent solar activity during the first year of this solar cycle.

Comparison of solar activity during last two minima on turn of Activity Cycles 22/23 and 23/24

NASA Astrophysics Data System (ADS)

Gryciuk, Magdalena; Gburek, Szymon; Siarkowski, Marek; Podgorski, Piotr; Sylwester, Janusz; Farnik, Frantisek

2013-07-01

The subject of our work is the review and comparison of solar activity during the last two solar minima that occurred between recent activity cycles. We use the soft X-ray global solar corona observations covering the two nine-months long time intervals in 1997/98 and 2009. Data from RF15-I multichannel photometer are used for the penultimate minimum. For the last unusually deep and prolonged solar activity minimum in 2009 the data from SphinX spectrophotometer are used. Comparison of measurements from both minima takes place in the overlapping energy range 2-15 keV. We focus on the active region formation, evolution and flaring productivity during respective minima.

Deep space telecommunications and the solar cycle: A reappraisal

NASA Technical Reports Server (NTRS)

Berman, A. L.

1978-01-01

Observations of density enhancement in the near corona at solar cycle (sunspot) maximum have rather uncritically been interpreted to apply equally well to the extended corona, thus generating concern about the quality of outer planet navigational data at solar cycle maximum. Spacecraft have been deployed almost continuously during the recently completed solar cycle 20, providing two powerful new coronal investigatory data sources: (1) in-situ spacecraft plasma measurements at approximately 1 AU, and (2) plasma effects on monochromatic spacecraft signals at all signal closest approach points. A comprehensive review of these (solar cycle 20) data lead to the somewhat surprising conclusions that for the region of interest of navigational data, the highest levels of charged particle corruption of navigational data can be expected to occur at solar cycle minimum, rather than solar cycle maximum, as previously believed.

A comparison of solar wind streams and coronal structure near solar minimum

NASA Technical Reports Server (NTRS)

Nolte, J. T.; Davis, J. M.; Gerassimenko, M.; Lazarus, A. J.; Sullivan, J. D.

1977-01-01

Solar wind data from the MIT detectors on the IMP 7 and 8 satellites and the SOLRAD 11B satellite for the solar-minimum period September-December, 1976, were compared with X-ray images of the solar corona taken by rocket-borne telescopes on September 16 and November 17, 1976. There was no compelling evidence that a coronal hole was the source of any high speed stream. Thus it is possible that either coronal holes were not the sources of all recurrent high-speed solar wind streams during the declining phase of the solar cycle, as might be inferred from the Skylab period, or there was a change in the appearance of some magnetic field regions near the time of solar minimum.

Statistical properties of solar flares and coronal mass ejections through the solar cycle

NASA Astrophysics Data System (ADS)

Telloni, Daniele; Carbone, Vincenzo; Lepreti, Fabio; Antonucci, Ester

2016-03-01

Waiting Time Distributions (WTDs) of solar flares are investigated all through the solar cycle. The same approach applied to Coronal Mass Ejections (CMEs) in a previous work is considered here for flare occurrence. Our analysis reveals that flares and CMEs share some common statistical properties, which result dependent on the level of solar activity. Both flares and CMEs seem to independently occur during minimum solar activity phases, whilst their WTDs significantly deviate from a Poisson function at solar maximum, thus suggesting that these events are correlated. The characteristics of WTDs are constrained by the physical processes generating those eruptions associated with flares and CMEs. A scenario may be drawn in which different mechanisms are actively at work during different phases of the solar cycle. Stochastic processes, most likely related to random magnetic reconnections of the field lines, seem to play a key role during solar minimum periods. On the other hand, persistent processes, like sympathetic eruptions associated to the variability of the photospheric magnetism, are suggested to dominate during periods of high solar activity. Moreover, despite the similar statistical properties shown by flares and CMEs, as it was mentioned above, their WTDs appear different in some aspects. During solar minimum periods, the flare occurrence randomness seems to be more evident than for CMEs. Those persistent mechanisms generating interdependent events during maximum periods of solar activity can be suggested to play a more important role for CMEs than for flares, thus mitigating the competitive action of the random processes, which seem instead strong enough to weaken the correlations among flare event occurrence during solar minimum periods. However, it cannot be excluded that the physical processes at the basis of the origin of the temporal correlation between solar events are different for flares and CMEs, or that, more likely, more sophisticated effects are at work at the same time leading to an even more complex picture. This work represents a first step for further investigations.

HEMISPHERIC ASYMMETRIES IN THE POLAR SOLAR WIND OBSERVED BY ULYSSES NEAR THE MINIMA OF SOLAR CYCLES 22 AND 23

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ebert, R. W.; Dayeh, M. A.; Desai, M. I.

2013-05-10

We examined solar wind plasma and interplanetary magnetic field (IMF) observations from Ulysses' first and third orbits to study hemispheric differences in the properties of the solar wind and IMF originating from the Sun's large polar coronal holes (PCHs) during the declining and minimum phase of solar cycles 22 and 23. We identified hemispheric asymmetries in several parameters, most notably {approx}15%-30% south-to-north differences in averages for the solar wind density, mass flux, dynamic pressure, and energy flux and the radial and total IMF magnitudes. These differences were driven by relatively larger, more variable solar wind density and radial IMF betweenmore » {approx}36 Degree-Sign S-60 Degree-Sign S during the declining phase of solar cycles 22 and 23. These observations indicate either a hemispheric asymmetry in the PCH output during the declining and minimum phase of solar cycles 22 and 23 with the southern hemisphere being more active than its northern counterpart, or a solar cycle effect where the PCH output in both hemispheres is enhanced during periods of higher solar activity. We also report a strong linear correlation between these solar wind and IMF parameters, including the periods of enhanced PCH output, that highlight the connection between the solar wind mass and energy output and the Sun's magnetic field. That these enhancements were not matched by similar sized variations in solar wind speed points to the mass and energy responsible for these increases being added to the solar wind while its flow was subsonic.« less

Long periods (1 -10 mHz) geomagnetic pulsations variation with solar cycle in South Atlantic Magnetic Anomaly

NASA Astrophysics Data System (ADS)

Rigon Silva, Willian; Schuch, Nelson Jorge; Guimarães Dutra, Severino Luiz; Babulal Trivedi, Nalin; Claudir da Silva, Andirlei; Souza Savian, Fernando; Ronan Coelho Stekel, Tardelli; de Siqueira, Josemar; Espindola Antunes, Cassio

The occurrence and intensity of the geomagnetic pulsations Pc-5 (2-7 mHz) and its relationship with the solar cycle in the South Atlantic Magnetic Anomaly -SAMA is presented. The study of geomagnetic pulsations is important to help the understanding of the physical processes that occurs in the magnetosphere region and help to predict geomagnetic storms. The fluxgate mag-netometers H, D and Z, three axis geomagnetic field data from the Southern Space Observatory -SSO/CRS/INPE -MCT, São Martinho da Serra (29.42° S, 53.87° W, 480m a.s.l.), RS, Brasil, a were analyzed and correlated with the solar wind parameters (speed, density and temperature) from the ACE and SOHO satellites. A digital filtering to enhance the 2-7 mHz geomagnetic pulsations was used. Five quiet days and five perturbed days in the solar minimum and in the solar maximum were selected for this analysis. The days were chosen based on the IAGA definition and on the Bartels Musical Diagrams (Kp index) for 2001 (solar maximum) and 2008 (solar minimum). The biggest Pc-5 amplitude averages differences between the H-component is 78,35 nT for the perturbed days and 1,60nT for the quiet days during the solar maximum. For perturbed days the average amplitude during the solar minimum is 8,32 nT, confirming a direct solar cycle influence in the geomagnetic pulsations intensity for long periods.

foF2 vs solar indices for the Rome station: Looking for the best general relation which is able to describe the anomalous minimum between cycles 23 and 24

NASA Astrophysics Data System (ADS)

Perna, L.; Pezzopane, M.

2016-10-01

Analyses of the dependence of the F2layer critical frequency, foF2, on five widely used solar activity indices (F10.7, Lym-α, MgII, R and EUV0.1-50)are carried out considering noon values manually validated at the ionospheric station of Rome (41.8°N, 12.5°E, Italy) between January 1976 and December 2013, a period of time covering the last three solar cycles and including the prolonged and anomalous minimum of solar cycle 23/24 (years 2008-2009). After applying a 1-year running mean to both foF2 and solar activity indices time series, a second order polynomial fitting proves to perform better than a linear one, and this is specifically due to the very low solar activity of the last solar minimum and to the remaining saturation effect characterizing the high solar activity. A comparison between observed and synthetic foF2 values, the latter calculated by using the analytical relations found for every index, and some considerations made on the R parameter introduced by Solomon et al. (2013), suggest that MgII is the best index to describe the dependence of foF2 on the solar activity. Three main reasons justify this result: (1) the good sensibility of MgII to the variations of foF2 for low solar activity; (2) the reduced saturation effect characterizing MgII at high solar activity; (3) the poor influence of the hysteresis effect characterizing MgII at medium solar activity. On the other hand, the F10.7 index, widely used as input parameter for numerous ionospheric models, does not represent properly the last minimum; specifically, it is not able to describe the variations of foF2 under a solar activity level of F10.7=82·10-22 [J Hz-1 s-1 m-2].

The Solar Cycle.

PubMed

Hathaway, David H

The solar cycle is reviewed. The 11-year cycle of solar activity is characterized by the rise and fall in the numbers and surface area of sunspots. A number of other solar activity indicators also vary in association with the sunspots including; the 10.7 cm radio flux, the total solar irradiance, the magnetic field, flares and coronal mass ejections, geomagnetic activity, galactic cosmic ray fluxes, and radioisotopes in tree rings and ice cores. Individual solar cycles are characterized by their maxima and minima, cycle periods and amplitudes, cycle shape, the equatorward drift of the active latitudes, hemispheric asymmetries, and active longitudes. Cycle-to-cycle variability includes the Maunder Minimum, the Gleissberg Cycle, and the Gnevyshev-Ohl (even-odd) Rule. Short-term variability includes the 154-day periodicity, quasi-biennial variations, and double-peaked maxima. We conclude with an examination of prediction techniques for the solar cycle and a closer look at cycles 23 and 24. Supplementary material is available for this article at 10.1007/lrsp-2015-4.

The Unusual Minimum of Cycle 23: Observations and Interpretation

NASA Astrophysics Data System (ADS)

Martens, Petrus C.; Nandy, D.; Munoz-Jaramillo, A.

2009-05-01

The current minimum of cycle 23 is unusual in its long duration, the very low level to which Total Solar Irradiance (TSI) has fallen, and the small flux of the open polar fields. The deep minimum of TSI seems to be related to an unprecedented dearth of polar faculae, and hence to the small amount of open flux. Based upon surface flux transport models it has been suggested that the causes of these phenomena may be an unusually vigorous meridional flow, or even a deviation from Joy's law resulting in smaller Joy angles than usual for emerging flux in cycle 23. There is also the possibility of a connection with the recently inferred emergence in polar regions of bipoles that systematically defy Hale's law. Much speculation has been going on as to the consequences of this exceptional minimum: are we entering another global minimum, is this the end of the 80 year period of exceptionally high solar activity, or is this just a statistical hiccup? Dynamo simulations are underway that may help answer this question. As an aside it must be mentioned that the current minimum of TSI puts an upper limit in the TSI input for global climate simulations during the Maunder minimum, and that a possible decrease in future solar activity will result in a very small but not insignificant reduction in the pace of global warming.

Space weather influence on the agriculture technology and wheat prices in the medieval England (1259-1703) through cosmic ray/solar activity cycle variations

NASA Astrophysics Data System (ADS)

Dorman, L. I.; Pustil'Nik, L. A.; Yom Din, G.

2003-04-01

The database of Professor Rogers (1887), which includes wheat prices in England in the Middle Ages (1249-1703) was used to search for possible manifestations of solar activity and cosmic ray intensity variations. The main object of our statistical analysis is investigation of bursts of prices. Our study shows that bursts and troughs of wheat prices take place at extreme states (maximums or minimums) of solar activity cycles. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by cosmic ray intensity solar cycle variations, and compare the expected price fluctuations with wheat price variations recorded in the Medieval England. We compared statistical properties of the intervals between price bursts with statistical properties of the intervals between extremes (minimums) of solar cycles during the years 1700-2000. The medians of both samples have the values of 11.00 and 10.7 years; standard deviations are 1.44 and 1.53 years for prices and for solar activity, respectively. The hypothesis that the frequency distributions are the same for both of the samples have significance level >95%. In the next step we analyzed direct links between wheat prices and cosmic ray cycle variations in the 17th Century, for which both wheat prices and cosmic ray intensity (derived from Be-10 isotope data) are available. We show that for all seven solar activity minimums (cosmic ray intensity maximums) the observed prices were higher than prices for the seven intervals of maximal solar activity (100% sign correlation). This result, combined with the conclusion of similarity of statistical properties of the price and solar activity extremes can be considered as direct evidence of a causal connection between wheat prices bursts and solar activity/cosmic ray intensity extremes.

Dynamo theory prediction of solar activity

NASA Technical Reports Server (NTRS)

Schatten, Kenneth H.

1988-01-01

The dynamo theory technique to predict decadal time scale solar activity variations is introduced. The technique was developed following puzzling correlations involved with geomagnetic precursors of solar activity. Based upon this, a dynamo theory method was developed to predict solar activity. The method was used successfully in solar cycle 21 by Schatten, Scherrer, Svalgaard, and Wilcox, after testing with 8 prior solar cycles. Schatten and Sofia used the technique to predict an exceptionally large cycle, peaking early (in 1990) with a sunspot value near 170, likely the second largest on record. Sunspot numbers are increasing, suggesting that: (1) a large cycle is developing, and (2) that the cycle may even surpass the largest cycle (19). A Sporer Butterfly method shows that the cycle can now be expected to peak in the latter half of 1989, consistent with an amplitude comparable to the value predicted near the last solar minimum.

Solar Rotational Periodicities and the Semiannual Variation in the Solar Wind, Radiation Belt, and Aurora

NASA Technical Reports Server (NTRS)

Emery, Barbara A.; Richardson, Ian G.; Evans, David S.; Rich, Frederick J.; Wilson, Gordon R.

2011-01-01

The behavior of a number of solar wind, radiation belt, auroral and geomagnetic parameters is examined during the recent extended solar minimum and previous solar cycles, covering the period from January 1972 to July 2010. This period includes most of the solar minimum between Cycles 23 and 24, which was more extended than recent solar minima, with historically low values of most of these parameters in 2009. Solar rotational periodicities from S to 27 days were found from daily averages over 81 days for the parameters. There were very strong 9-day periodicities in many variables in 2005 -2008, triggered by recurring corotating high-speed streams (HSS). All rotational amplitudes were relatively large in the descending and early minimum phases of the solar cycle, when HSS are the predominant solar wind structures. There were minima in the amplitudes of all solar rotational periodicities near the end of each solar minimum, as well as at the start of the reversal of the solar magnetic field polarity at solar maximum (approx.1980, approx.1990, and approx. 2001) when the occurrence frequency of HSS is relatively low. Semiannual equinoctial periodicities, which were relatively strong in the 1995-1997 solar minimum, were found to be primarily the result of the changing amplitudes of the 13.5- and 27-day periodicities, where 13.5-day amplitudes were better correlated with heliospheric daily observations and 27-day amplitudes correlated better with Earth-based daily observations. The equinoctial rotational amplitudes of the Earth-based parameters were probably enhanced by a combination of the Russell-McPherron effect and a reduction in the solar wind-magnetosphere coupling efficiency during solstices. The rotational amplitudes were cross-correlated with each other, where the 27 -day amplitudes showed some of the weakest cross-correlations. The rotational amplitudes of the > 2 MeV radiation belt electron number fluxes were progressively weaker from 27- to 5-day periods, showing that processes in the magnetosphere act as a low-pass filter between the solar wind and the radiation belt. The A(sub p)/K(sub p) magnetic currents observed at subauroral latitudes are sensitive to proton auroral precipitation, especially for 9-day and shorter periods, while the A(sub p)/K(sub p) currents are governed by electron auroral precipitation for 13.5- and 27-day periodicities.

ESTIMATE OF SOLAR MAXIMUM USING THE 1-8 Å GEOSTATIONARY OPERATIONAL ENVIRONMENTAL SATELLITES X-RAY MEASUREMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Winter, L. M.; Balasubramaniam, K. S., E-mail: lwinter@aer.com

We present an alternate method of determining the progression of the solar cycle through an analysis of the solar X-ray background. Our results are based on the NOAA Geostationary Operational Environmental Satellites (GOES) X-ray data in the 1-8 Å band from 1986 to the present, covering solar cycles 22, 23, and 24. The X-ray background level tracks the progression of the solar cycle through its maximum and minimum. Using the X-ray data, we can therefore make estimates of the solar cycle progression and the date of solar maximum. Based upon our analysis, we conclude that the Sun reached its hemisphere-averagedmore » maximum in solar cycle 24 in late 2013. This is within six months of the NOAA prediction of a maximum in spring 2013.« less

Adverse Space Weather at the Solar Cycle Minimum

NASA Astrophysics Data System (ADS)

Baker, D. N.; Kanekal, S. G.; McCollough, J. P.; Singer, H. J.; Chappell, S. P.; Allen, J. H.

2008-05-01

It is commonly understood that many types of adverse space weather (solar flares, coronal mass ejections, geomagnetic storms) occur most commonly around the maximum of the 11-year sunspot activity cycle. Other types of well-known space weather such as relativistic electron events in the Earth's outer magnetosphere (that produce deep dielectric charging in spacecraft systems) are usually associated with the period just after sunspot maximum. At the present time, we are in the very lowest activity phase of the sunspot cycle (solar minimum). As such we would not expect much in the way of adverse space weather events. However, in early to mid-February of 2008 quite prominent solar coronal holes produced two high-speed streams that in turn stimulated very large, long-duration relativistic electron enhancements in Earth's magnetosphere. These seem to have been associated with several spacecraft operational anomalies at various spacecraft orbital locations. We describe these recent space weather events and assess their operational significance in this presentation. These results show that substantial space weather events can and do occur even during the quietest parts of the solar cycle.

Geomagnetism during solar cycle 23: Characteristics.

PubMed

Zerbo, Jean-Louis; Amory-Mazaudier, Christine; Ouattara, Frédéric

2013-05-01

On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996-2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3 nT) and yearly averaged solar wind speed (364 km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568 km/s), associated to the highest value of the yearly averaged aa index (37 nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum.

Solar cycle variability of nonmigrating tides in the infrared cooling of the thermosphere

NASA Astrophysics Data System (ADS)

Nischal, N.; Oberheide, J.; Mlynczak, M. G.; Marsh, D. R.

2017-12-01

Nitric Oxide (NO) at 5.3 μm and Carbon dioxide (CO2) at 15 μm are the major infrared emissions responsible for the radiative cooling of the thermosphere. We study the impact of two important diurnal nonmigrating tides, the DE2 and DE3, on NO and CO2 infrared emissions over a complete solar cycle (2002-2013) by (i) analyzing NO and CO2 cooling rate data from SABER and (ii) photochemical modeling using dynamical tides from a thermospheric empirical tidal model, CTMT. Both observed and modeled results show that the NO cooling rate amplitudes for DE2 and DE3 exhibit strong solar cycle dependence. NO 5.3 μm cooling rate tides are relatively unimportant for the infrared energy budget during solar minimum but important during solar maximum. On the other hand DE2 and DE3 in CO2 show comparatively small variability over a solar cycle. CO2 15 μm cooling rate tides remain, to a large extent, constant between solar minimum and maximum. This different responses by NO and CO2 emissions to the DE2 and DE3 during a solar cycle comes form the fact that the collisional reaction rate for NO is highly sensitive to the temperature comparative to that for CO2. Moreover, the solar cycle variability of these nonmigrating tides in thermospheric infrared emissions shows a clear QBO signals substantiating the impact of tropospheric weather system on the energy budget of the thermosphere. The relative contribution from the individual tidal drivers; temperature, density and advection to the observed DE2 and DE3 tides does not vary much over the course of the solar cycle, and this is true for both NO and CO2 emissions.

Solar Cycle 24 and the Solar Dynamo

NASA Technical Reports Server (NTRS)

Pesnell, W. D.; Schatten, K.

2007-01-01

We will discuss the polar field precursor method for solar activity prediction, which predicts cycle 24 will be significantly lower than recent activity cycles, and some new ideas rejuvenating Babcock's shallow surface dynamo. The polar field precursor method is based on Babcock and Leighton's dynamo models wherein the polar field at solar minimum plays a major role in generating the next cycle's toroidal field and sunspots. Thus, by examining the polar fields of the Sun near solar minimum, a forecast for the next cycle's activity is obtained. With the current low value for the Sun's polar fields, this method predicts solar cycle 24 will be one of the lowest in recent times, with smoothed F10.7 radio flux values peaking near 135 plus or minus 35 (2 sigma), in the 2012-2013 timeframe (equivalent to smoothed Rz near 80 plus or minus 35 [2 sigma]). One may have to consider solar activity as far back as the early 20th century to find a cycle of comparable magnitude. We discuss unusual behavior in the Sun's polar fields that support this prediction. Normally, the solar precursor method is consistent with the geomagnetic precursor method, wherein geomagnetic variations are thought to be a good measure of the Sun's polar field strength. Because of the unusual polar field, the Earth does not appear to be currently bathed in the Sun's extended polar field (the interplanetary field), hence negating the primal cause behind the geomagnetic precursor technique. We also discuss how percolation may support Babcock's original shallow solar dynamo. In this process ephemeral regions from the solar magnetic carpet, guided by shallow surface fields, may collect to form pores and sunspots.

Evolution of Our Understanding of the Solar Dynamo During Solar Cycle 24

NASA Astrophysics Data System (ADS)

Munoz-Jaramillo, A.

2017-12-01

Solar cycle 24 has been an exciting cycle for our understanding of the solar dynamo: 1. It was the first cycle for which dynamo based predictions were ever used teaching us valuable lessons. 2. It has given us the opportunity to observe a deep minimum and a weak cycle with a high level of of observational detail . 3. It is full of breaktrhoughs in anelastic MHD dynamo simulations (regular cycles, buoyant flux-tubes, mounder-like events). 4. It has seen the creation of bridges between the kinematic flux-transport and anelastic MHD approaches. 5. It has ushered a new generation of realistic surface flux-transport simulations 6. We have achieved significant observational progress in our understanding of solar cycle propagation. The objective of this talk is to highlight some of the most important results, giving special emphasis on what they have taught us about solar cycle predictability.

AFT: Extending Solar Cycle Prediction with Data Assimilation

NASA Astrophysics Data System (ADS)

Upton, L.; Hathaway, D. H.

2017-12-01

The Advective Flux Transport (AFT) model is an innovative surface flux transport model that simulates the evolution of the radial magnetic field on the surface of the Sun. AFT was designed to be as realistic as possible by 1: incorporating the observed surface flows (meridional flow, differential rotation, and an explicit evolving convective pattern) and by 2: using data assimilation to incorporate the observed magnetic fields directly from line-of-sight (LOS) magnetograms. AFT has proven to be successful in simulating the evolution of the surface magnetic fields on both short time scales (days-weeks) as well as for long time scales (years). In particular, AFT has been shown to accurately predict the evolution of the Sun's dipolar magnetic field 3-5 years in advance. Since the Sun's polar magnetic field strength at solar cycle minimum is the best indicator of the amplitude of the next cycle, this has in turn extended our ability to make solar cycle predictions to 3-5 years before solar minimum occurs. Here, we will discuss some of the challenges of implementing data assimilation into AFT. We will also discuss the role of data assimilation in advancing solar cycle predictive capability.

C-14 and temperature variation around and after AD 775 - after the Dark Age Grand Minimum

NASA Astrophysics Data System (ADS)

Neuhäuser, Ralph; Neuhäuser, Dagmar L.

2016-04-01

We have compiled an extensive catalog of aurora observations from the Far and Near East as well as Europe for the time from AD 550 to 845. From historic observations of aurorae and sunspots as well as the C-14 and Be-10 data, we can date the end of the Dark Age grand minimum to about AD 690; we see strong activity after this period. We can fix the solar activity Schwabe cycle maxima and minima in the 7th and 8th centuries.. The strong 14-C increase in data with 1-yr time resolution in the AD 770s (e.g. Miyake et al. 2012) is still a matter of debate, e.g. a solar super-flare. In the last three millennia, there were two more strong rapid rises in 14-C - around BC 671 and AD 1795. All three 14-C variations are embedded in similar evolution of solar activity, as we can show with various solar activity proxies; secular evolution of solar wind plays an important role. The rises of 14-C - within a few years each - can be explained by a sudden strong decrease in solar modulation potential leading to increased radioisotope production. The strong rises around AD 775 and 1795 are due to three effects: (i) very strong activity in the previous cycles (i.e. very low 14-C level), (ii) the declining phase of a very strong Schwabe cycle, and (iii) a phase of very weak activity after the strong 14-C rise - very short and/or weak cycle(s) like the suddenly starting Dalton minimum. In addition to arXiv:1503.01581 and arXiv:1508.06745, we also discuss the temperature depression and new quasi-annual 10-Be data. If a temperature depression right after AD 775 for a few decades can be confirmed, this would be fully consistent with our suggestion: reduced solar activity since AD 775 (for a few decades like in the Dalton minimum). Otherwise, one would not expect such a temperature depression after a solar super-flare.

A stochastically forced time delay solar dynamo model: Self-consistent recovery from a maunder-like grand minimum necessitates a mean-field alpha effect

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hazra, Soumitra; Nandy, Dibyendu; Passos, Dário, E-mail: s.hazra@iiserkol.ac.in, E-mail: dariopassos@ist.utl.pt, E-mail: dnandi@iiserkol.ac.in

Fluctuations in the Sun's magnetic activity, including episodes of grand minima such as the Maunder minimum have important consequences for space and planetary environments. However, the underlying dynamics of such extreme fluctuations remain ill-understood. Here, we use a novel mathematical model based on stochastically forced, non-linear delay differential equations to study solar cycle fluctuations in which time delays capture the physics of magnetic flux transport between spatially segregated dynamo source regions in the solar interior. Using this model, we explicitly demonstrate that the Babcock-Leighton poloidal field source based on dispersal of tilted bipolar sunspot flux, alone, cannot recover the sunspotmore » cycle from a grand minimum. We find that an additional poloidal field source effective on weak fields—e.g., the mean-field α effect driven by helical turbulence—is necessary for self-consistent recovery of the sunspot cycle from grand minima episodes.« less

Deciphering Solar Magnetic Activity: On Grand Minima in Solar Activity

NASA Astrophysics Data System (ADS)

Mcintosh, Scott; Leamon, Robert

2015-07-01

The Sun provides the energy necessary to sustain our existence. While the Sun provides for us, it is also capable of taking away. The weather and climatic scales of solar evolution and the Sun-Earth connection are not well understood. There has been tremendous progress in the century since the discovery of solar magnetism - magnetism that ultimately drives the electromagnetic, particulate and eruptive forcing of our planetary system. There is contemporary evidence of a decrease in solar magnetism, perhaps even indicators of a significant downward trend, over recent decades. Are we entering a minimum in solar activity that is deeper and longer than a typical solar minimum, a "grand minimum"? How could we tell if we are? What is a grand minimum and how does the Sun recover? These are very pertinent questions for modern civilization. In this paper we present a hypothetical demonstration of entry and exit from grand minimum conditions based on a recent analysis of solar features over the past 20 years and their possible connection to the origins of the 11(-ish) year solar activity cycle.

TWO NOVEL PARAMETERS TO EVALUATE THE GLOBAL COMPLEXITY OF THE SUN'S MAGNETIC FIELD AND TRACK THE SOLAR CYCLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhao, L.; Landi, E.; Gibson, S. E., E-mail: lzh@umich.edu

2013-08-20

Since the unusually prolonged and weak solar minimum between solar cycles 23 and 24 (2008-2010), the sunspot number is smaller and the overall morphology of the Sun's magnetic field is more complicated (i.e., less of a dipole component and more of a tilted current sheet) compared with the same minimum and ascending phases of the previous cycle. Nearly 13 yr after the last solar maximum ({approx}2000), the monthly sunspot number is currently only at half the highest value of the past cycle's maximum, whereas the polar magnetic field of the Sun is reversing (north pole first). These circumstances make itmore » timely to consider alternatives to the sunspot number for tracking the Sun's magnetic cycle and measuring its complexity. In this study, we introduce two novel parameters, the standard deviation (SD) of the latitude of the heliospheric current sheet (HCS) and the integrated slope (SL) of the HCS, to evaluate the complexity of the Sun's magnetic field and track the solar cycle. SD and SL are obtained from the magnetic synoptic maps calculated by a potential field source surface model. We find that SD and SL are sensitive to the complexity of the HCS: (1) they have low values when the HCS is flat at solar minimum, and high values when the HCS is highly tilted at solar maximum; (2) they respond to the topology of the HCS differently, as a higher SD value indicates that a larger part of the HCS extends to higher latitude, while a higher SL value implies that the HCS is wavier; (3) they are good indicators of magnetically anomalous cycles. Based on the comparison between SD and SL with the normalized sunspot number in the most recent four solar cycles, we find that in 2011 the solar magnetic field had attained a similar complexity as compared to the previous maxima. In addition, in the ascending phase of cycle 24, SD and SL in the northern hemisphere were on the average much greater than in the southern hemisphere, indicating a more tilted and wavier HCS in the north than the south, associated with the early reversal of the polar magnetic field in the north relative to the south.« less

Field aligned current study during the solar declining- extreme minimum of 23 solar cycle

NASA Astrophysics Data System (ADS)

Nepolian, Jeni Victor; Kumar, Anil; C, Panneerselvam

Field Aligned Current (FAC) density study has been carried out during the solar declining phase from 2004 to 2006 of the 23rd solar cycle and the ambient terrestrial magnetic field of the extended minimum period of 2008 and 2009. We mainly depended on CHAMP satellite data (http://isdc.gfz-potsdam.de/) for computing the FAC density with backup of IGRF-10 model. The study indicates that, the FAC is controlled by quasi-viscous processes occurring at the flank of the earth’s magnetosphere. The dawn-dusk conventional pattern enhanced during disturbed days. The intensity of R1 current system is higher than the R2 current system. Detailed results will be discussed in the conference.

Predictions of Sunspot Cycle 24: A Comparison with Observations

NASA Astrophysics Data System (ADS)

Bhatt, N. J.; Jain, R.

2017-12-01

The space weather is largely affected due to explosions on the Sun viz. solar flares and CMEs, which, however, in turn depend upon the magnitude of the solar activity i e. number of sunspots and their magnetic configuration. Owing to these space weather effects, predictions of sunspot cycle are important. Precursor techniques, particularly employing geomagnetic indices, are often used in the prediction of the maximum amplitude of a sunspot cycle. Based on the average geomagnetic activity index aa (since 1868 onwards) for the year of the sunspot minimum and the preceding four years, Bhatt et al. (2009) made two predictions for sunspot cycle 24 considering 2008 as the year of sunspot minimum: (i) The annual maximum amplitude would be 92.8±19.6 (1-sigma accuracy) indicating a somewhat weaker cycle 24 as compared to cycles 21-23, and (ii) smoothed monthly mean sunspot number maximum would be in October 2012±4 months (1-sigma accuracy). However, observations reveal that the sunspot minima extended up to 2009, and the maximum amplitude attained is 79, with a monthly mean sunspot number maximum of 102.3 in February 2014. In view of the observations and particularly owing to the extended solar minimum in 2009, we re-examined our prediction model and revised the prediction results. We find that (i) The annual maximum amplitude of cycle 24 = 71.2 ± 19.6 and (ii) A smoothed monthly mean sunspot number maximum in January 2014±4 months. We discuss our failure and success aspects and present improved predictions for the maximum amplitude as well as for the timing, which are now in good agreement with the observations. Also, we present the limitations of our forecasting in the view of long term predictions. We show if year of sunspot minimum activity and magnitude of geomagnetic activity during sunspot minimum are taken correctly then our prediction method appears to be a reliable indicator to forecast the sunspot amplitude of the following solar cycle. References:Bhatt, N.J., Jain, R. & Aggarwal, M.: 2009, Sol. Phys. 260, 225

LASCO Observations Of The K-Corona From Solar Minimum To Solar Maximum And Beyond

NASA Astrophysics Data System (ADS)

Andrews, Michael D.; Howard, Russell A.

2003-09-01

The LASCO C2 and C3 coronagraphs on SOHO have been recording a regular series of images of the corona since May 1996. This sequence of data covers the period of solar minimum, the increase to solar maximum, and the beginning of the decline toward the next solar minimum. The images have been analyzed to determine the brightness of the K-corona (solar photons Thomson scattered from free electrons). The total brightness of the K-corona is approximately constant from May 1996 through May 1997. The brightness is then seen to increase steadily until early in the year 2000. The structure of the K-corona changes dramatically with solar cycle. The shape as seen in C2 becomes almost circular at solar maximum while the C3 images continue to show equatorial streamers. The magnitude of the solar cycle variation decreases as the height increases. We present data animations (movies) to show the large-scale structure. We have inverted 28-day averages of the white light images to determine radial profiles of electron density. We present these electron profiles, show how they vary as a function of both latitude and time, and compare our observed profiles with other models and observations.

Comment on "The Predicted Size of Cycle 23 Based on the Inferred three-cycle Quasiperiodicity of the Planetary Index Ap"

NASA Technical Reports Server (NTRS)

Wilson, Robert M.; Hathaway, David H.

1999-01-01

Recently, Ahluwalia reviewed the solar and geomagnetic data for the last 6 decades and remarked that these data "indicate the existence of a three-solar-activity-cycle quasiperiodicity in them." Furthermore, on the basis of this inferred quasiperiodicity, he asserted that cycle 23 represents the initial cycle in a new three-cycle string, implying that it "will be more modest (a la cycle 17) with an annual mean sunspot number count of 119.3 +/- 30 at the maximum", a prediction that is considerably below the consensus prediction of 160 +/- 30 by Joselin et al. and of similar predictions by others based on a variety of predictive techniques. Several major sticking points of Ahluwalia's presentation, however, must be readdressed, and these issues form the basis of this comment. First, Ahluwalia appears to have based his analysis on a data set of Ap index values that is erroneous. For example, he depicts for the interval of 1932-1997 the variation of the Ap index in terms of annual averages, contrasting them against annual averages of sunspot number (SSN), and he lists for cycles 17-23 the minimum and maximum value of each, as well as the years in which they occur and a quantity which he calls "Amplitude" (defined as the numeric difference between the maximum and minimum values). In particular, he identifies the minimum Ap index (i.e., the minimum value of the Ap index in the vicinity of sunspot cycle minimum, which usually occurs in the year following sunspot minimum and which will be called hereafter, simply, Ap min) and the year in which it occur for cycles 17 - 23 respectively.

Manifestations of Influence of Solar Activity and Cosmic Ray Intensity on the Wheat Price in the Medieval England (1259-1703 Years)

NASA Astrophysics Data System (ADS)

Pustil'Nik, Lev A.; Dorman, L. I.; Yom Din, G.

2003-07-01

The database of Professor Rogers, with wheat prices in England in the Middle Ages (1249-1703) was used to search for possible manifestations of solar activity and cosmic ray variations. The main object of the statistical analysis is investigation of bursts of prices. We present a conceptual model of possible modes for sensitivity of wheat prices to weather conditions, caused by solar cycle variations in cosmic rays, and compare the expected price fluctuations with wheat price variations recorded in the Medieval England. We compared statistical properties of the intervals between price bursts with statistical properties of the intervals between extremes (minimums) of solar cycles during the years 1700-2000. Statistical properties of these two samples are similar both in averaged/median values of intervals and in standard deviation of this values. We show that histogram of intervals distribution for price bursts and solar minimums are coincidence with high confidence level. We analyzed direct links between wheat prices and solar activity in the th 17 Century, for which wheat prices and solar activity data as well as cosmic ray intensity (from 10 Be isotop e) are available. We show that for all seven solar activity minimums the observed prices were higher than prices for the nine intervals of maximal solar activity proceed preceding to the minimums. This result, combined with the conclusion on similarity of statistical properties of the price bursts and solar activity extremes we consider as direct evidence of a causal connection between wheat prices bursts and solar activity.

Behavior of Solar Cycles 23 and 24 Revealed by Microwave Observations

NASA Technical Reports Server (NTRS)

Gopalswamy, N.; Yashiro, S.; Maekelae, P.; Michalek, G.; Shibasaki, K.; Hathaway, D. H.

2012-01-01

Using magnetic and microwave butterfly diagrams, we compare the behavior of solar polar regions to show that (1) the polar magnetic field and the microwave brightness temperature during solar minimum substantially diminished during the cycle 23/24 minimum compared to the 22/23 minimum. (2) The polar microwave brightness temperature (Tb) seems to be a good proxy for the underlying magnetic field strength (B). The analysis indicates a relationship, B = 0.0067Tb - 70, where B is in G and Tb in K. (3) Both the brightness temperature and the magnetic field strength show north-south asymmetry most of the time except for a short period during the maximum phase. (4) The rush-to-the-pole phenomenon observed in the prominence eruption (PE) activity seems to be complete in the northern hemisphere as of 2012 March. (5) The decline of the microwave brightness temperature in the north polar region to the quiet-Sun levels and the sustained PE activity poleward of 60degN suggest that solar maximum conditions have arrived at the northern hemisphere. The southern hemisphere continues to exhibit conditions corresponding to the rise phase of solar cycle 24. Key words: Sun: chromosphere Sun: coronal mass ejections (CMEs) Sun: filaments, prominences Sun: photosphere Sun: radio radiation Sun: surface magnetism

A Change in the Solar He II EUV Global Network Structure as an Indicator of the Geo-Effectiveness of Solar Minima

NASA Technical Reports Server (NTRS)

Didkovsky, L.; Gurman, J. B.

2013-01-01

Solar activity during 2007 - 2009 was very low, causing anomalously low thermospheric density. A comparison of solar extreme ultraviolet (EUV) irradiance in the He II spectral band (26 to 34 nm) from the Solar Extreme ultraviolet Monitor (SEM), one of instruments on the Charge Element and Isotope Analysis System (CELIAS) on board the Solar and Heliospheric Observatory (SOHO) for the two latest solar minima showed a decrease of the absolute irradiance of about 15 +/- 6 % during the solar minimum between Cycles 23 and 24 compared with the Cycle 22/23 minimum when a yearly running-mean filter was used. We found that some local, shorter-term minima including those with the same absolute EUV flux in the SEM spectral band show a higher concentration of spatial power in the global network structure from the 30.4 nm SOHO/Extreme ultraviolet Imaging Telescope (EIT) images for the local minimum of 1996 compared with the minima of 2008 - 2011.We interpret this higher concentration of spatial power in the transition region's global network structure as a larger number of larger-area features on the solar disk. These changes in the global network structure during solar minima may characterize, in part, the geo-effectiveness of the solar He II EUV irradiance in addition to the estimations based on its absolute levels.

Mars surface radiation exposure for solar maximum conditions and 1989 solar proton events

NASA Technical Reports Server (NTRS)

Simonsen, Lisa C.; Nealy, John E.

1992-01-01

The Langley heavy-ion/nucleon transport code, HZETRN, and the high-energy nucleon transport code, BRYNTRN, are used to predict the propagation of galactic cosmic rays (GCR's) and solar flare protons through the carbon dioxide atmosphere of Mars. Particle fluences and the resulting doses are estimated on the surface of Mars for GCR's during solar maximum conditions and the Aug., Sep., and Oct. 1989 solar proton events. These results extend previously calculated surface estimates for GCR's at solar minimum conditions and the Feb. 1956, Nov. 1960, and Aug. 1972 solar proton events. Surface doses are estimated with both a low-density and a high-density carbon dioxide model of the atmosphere for altitudes of 0, 4, 8, and 12 km above the surface. A solar modulation function is incorporated to estimate the GCR dose variation between solar minimum and maximum conditions over the 11-year solar cycle. By using current Mars mission scenarios, doses to the skin, eye, and blood-forming organs are predicted for short- and long-duration stay times on the Martian surface throughout the solar cycle.

Detection of large scale geomagnetic pulsations by MAGDAS-egypt stations during the solar minimum of the solar cycle 24

NASA Astrophysics Data System (ADS)

Fathy, Ibrahim

2016-07-01

This paper presents a statistical study of different types of large-scale geomagnetic pulsation (Pc3, Pc4, Pc5 and Pi2) detected simultaneously by two MAGDAS stations located at Fayum (Geo. Coordinates 29.18 N and 30.50 E) and Aswan (Geo. Coordinates 23.59 N and 32.51 E) in Egypt. The second order butter-worth band-pass filter has been used to filter and analyze the horizontal H-component of the geomagnetic field in one-second data. The data was collected during the solar minimum of the current solar cycle 24. We list the most energetic pulsations detected by the two stations instantaneously, in addition; the average amplitude of the pulsation signals was calculated.

Cyclic Evolution of Coronal Fields from a Coupled Dynamo Potential-Field Source-Surface Model.

PubMed

Dikpati, Mausumi; Suresh, Akshaya; Burkepile, Joan

The structure of the Sun's corona varies with the solar-cycle phase, from a near spherical symmetry at solar maximum to an axial dipole at solar minimum. It is widely accepted that the large-scale coronal structure is governed by magnetic fields that are most likely generated by dynamo action in the solar interior. In order to understand the variation in coronal structure, we couple a potential-field source-surface model with a cyclic dynamo model. In this coupled model, the magnetic field inside the convection zone is governed by the dynamo equation; these dynamo-generated fields are extended from the photosphere to the corona using a potential-field source-surface model. Assuming axisymmetry, we take linear combinations of associated Legendre polynomials that match the more complex coronal structures. Choosing images of the global corona from the Mauna Loa Solar Observatory at each Carrington rotation over half a cycle (1986 - 1991), we compute the coefficients of the associated Legendre polynomials up to degree eight and compare with observations. We show that at minimum the dipole term dominates, but it fades as the cycle progresses; higher-order multipolar terms begin to dominate. The amplitudes of these terms are not exactly the same for the two limbs, indicating that there is a longitude dependence. While both the 1986 and the 1996 minimum coronas were dipolar, the minimum in 2008 was unusual, since there was a substantial departure from a dipole. We investigate the physical cause of this departure by including a North-South asymmetry in the surface source of the magnetic fields in our flux-transport dynamo model, and find that this asymmetry could be one of the reasons for departure from the dipole in the 2008 minimum.

Variability of space climate and its extremes with successive solar cycles

NASA Astrophysics Data System (ADS)

Chapman, Sandra; Hush, Phillip; Tindale, Elisabeth; Dunlop, Malcolm; Watkins, Nicholas

2016-04-01

Auroral geomagnetic indices coupled with in situ solar wind monitors provide a comprehensive data set, spanning several solar cycles. Space climate can be considered as the distribution of space weather. We can then characterize these observations in terms of changing space climate by quantifying how the statistical properties of ensembles of these observed variables vary between different phases of the solar cycle. We first consider the AE index burst distribution. Bursts are constructed by thresholding the AE time series; the size of a burst is the sum of the excess in the time series for each time interval over which the threshold is exceeded. The distribution of burst sizes is two component with a crossover in behaviour at thresholds ≈ 1000 nT. Above this threshold, we find[1] a range over which the mean burst size is almost constant with threshold for both solar maxima and minima. The burst size distribution of the largest events has a functional form which is exponential. The relative likelihood of these large events varies from one solar maximum and minimum to the next. If the relative overall activity of a solar maximum/minimum can be estimated, these results then constrain the likelihood of extreme events of a given size for that solar maximum/minimum. We next develop and apply a methodology to quantify how the full distribution of geomagnetic indices and upstream solar wind observables are changing between and across different solar cycles. This methodology[2] estimates how different quantiles of the distribution, or equivalently, how the return times of events of a given size, are changing. [1] Hush, P., S. C. Chapman, M. W. Dunlop, and N. W. Watkins (2015), Robust statistical properties of the size of large burst events in AE, Geophys. Res. Lett.,42 doi:10.1002/2015GL066277 [2] Chapman, S. C., D. A. Stainforth, N. W. Watkins, (2013) On estimating long term local climate trends , Phil. Trans. Royal Soc., A,371 20120287 DOI:10.1098/rsta.2012.0287

Geomagnetism during solar cycle 23: Characteristics

PubMed Central

Zerbo, Jean-Louis; Amory-Mazaudier, Christine; Ouattara, Frédéric

2012-01-01

On the basis of more than 48 years of morphological analysis of yearly and monthly values of the sunspot number, the aa index, the solar wind speed and interplanetary magnetic field, we point out the particularities of geomagnetic activity during the period 1996–2009. We especially investigate the last cycle 23 and the long minimum which followed it. During this period, the lowest values of the yearly averaged IMF (3 nT) and yearly averaged solar wind speed (364 km/s) are recorded in 1996, and 2009 respectively. The year 2003 shows itself particular by recording the highest value of the averaged solar wind (568 km/s), associated to the highest value of the yearly averaged aa index (37 nT). We also find that observations during the year 2003 seem to be related to several coronal holes which are known to generate high-speed wind stream. From the long time (more than one century) study of solar variability, the present period is similar to the beginning of twentieth century. We especially present the morphological features of solar cycle 23 which is followed by a deep solar minimum. PMID:25685427

Geomagnetic detection of the sectorial solar magnetic field and the historical peculiarity of minimum 23-24

USGS Publications Warehouse

Love, Jeffrey J.; Rigler, J.

2012-01-01

[1] Analysis is made of the geomagnetic-activityaaindex covering solar cycle 11 to the beginning of 24, 1868–2011. Autocorrelation shows 27.0-d recurrent geomagnetic activity that is well-known to be prominent during solar-cycle minima; some minima also exhibit a smaller amount of 13.5-d recurrence. Previous work has shown that the recent solar minimum 23–24 exhibited 9.0 and 6.7-d recurrence in geomagnetic and heliospheric data, but those recurrence intervals were not prominently present during the preceding minima 21–22 and 22–23. Using annual-averages and solar-cycle averages of autocorrelations of the historicalaadata, we put these observations into a long-term perspective: none of the 12 minima preceding 23–24 exhibited prominent 9.0 and 6.7-d geomagnetic activity recurrence. We show that the detection of these recurrence intervals can be traced to an unusual combination of sectorial spherical-harmonic structure in the solar magnetic field and anomalously low sunspot number. We speculate that 9.0 and 6.7-d recurrence is related to transient large-scale, low-latitude organization of the solar dynamo, such as seen in some numerical simulations.

Heartbeat of the Sun from Principal Component Analysis and prediction of solar activity on a millenium timescale

PubMed Central

Zharkova, V. V.; Shepherd, S. J.; Popova, E.; Zharkov, S. I.

2015-01-01

We derive two principal components (PCs) of temporal magnetic field variations over the solar cycles 21–24 from full disk magnetograms covering about 39% of data variance, with σ = 0.67. These PCs are attributed to two main magnetic waves travelling from the opposite hemispheres with close frequencies and increasing phase shift. Using symbolic regeression analysis we also derive mathematical formulae for these waves and calculate their summary curve which we show is linked to solar activity index. Extrapolation of the PCs backward for 800 years reveals the two 350-year grand cycles superimposed on 22 year-cycles with the features showing a remarkable resemblance to sunspot activity reported in the past including the Maunder and Dalton minimum. The summary curve calculated for the next millennium predicts further three grand cycles with the closest grand minimum occurring in the forthcoming cycles 26–27 with the two magnetic field waves separating into the opposite hemispheres leading to strongly reduced solar activity. These grand cycle variations are probed by α − Ω dynamo model with meridional circulation. Dynamo waves are found generated with close frequencies whose interaction leads to beating effects responsible for the grand cycles (350–400 years) superimposed on a standard 22 year cycle. This approach opens a new era in investigation and confident prediction of solar activity on a millenium timescale. PMID:26511513

QBO of temperature in mesopause and lower thermosphere caused by solar activity variations

NASA Astrophysics Data System (ADS)

Shefov, N. N.; Semenov, A. I.

2003-04-01

On the basis of the data of the emission (hydroxyl, sodium and atomic oxygen 557.7 nm) and radiophysical (87-107 km) measurements some regularities of quasi-biennial oscillation (QBO) of the atmospheric temperature at heights of the mesopause and lower thermosphere are investigated. It is shown, that they are closely connected with quasi-biennial variations of solar activity and form within the limits of a cycle of solar activity the fading wave train of oscillations. Such behaviour of the wave train can be adequately described by the Airy function. As a result of the analysis of characteristics of QBO of solar activity during 17-23rd cycles it is shown, that to each 11-years cycle correspond its wave train of QBO. Amplitudes and periods of this wave train decrease during a cycle, i.e. it represents Not harmonious oscillation but it is a cyclic aperiodic oscillation (CAO). Therefore usual methods of Fourier analysis used earlier did not result in the same values of the period. The wave train of the current cycle begins at the end of previous and some time together with the subsequent cycle proceeds. Thus, the time sequence of activity during solar cycle represents superposition of three wave trains. Period of CAO in the beginning of a cycle has ~ 38 months and decreases to the end of a cycle up to ~ 21 months. The first wide negative minimum of Airy function describing of the wave train of CAO corresponds to solar activity minimum in the 11-year cycle. The time scale of the wave train varies from one cycle to another. Full duration of individual wave train is ~ 22 years. Owing to a mutual interference of the consecutive wave trains in the 11-year cycles the observable variations of solar activity are not identical. Structure of CAO obviously displays magnetohydrodynamic processes inside the Sun. This work was supported by the Grant No. 2274 of ISTC.

Temporal Variability of Atomic Hydrogen From the Mesopause to the Upper Thermosphere

NASA Astrophysics Data System (ADS)

Qian, Liying; Burns, Alan G.; Solomon, Stan S.; Smith, Anne K.; McInerney, Joseph M.; Hunt, Linda A.; Marsh, Daniel R.; Liu, Hanli; Mlynczak, Martin G.; Vitt, Francis M.

2018-01-01

We investigate atomic hydrogen (H) variability from the mesopause to the upper thermosphere, on time scales of solar cycle, seasonal, and diurnal, using measurements made by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere Ionosphere Mesosphere Energetics Dynamics satellite, and simulations by the National Center for Atmospheric Research Whole Atmosphere Community Climate Model-eXtended (WACCM-X). In the mesopause region (85 to 95 km), the seasonal and solar cycle variations of H simulated by WACCM-X are consistent with those from SABER observations: H density is higher in summer than in winter, and slightly higher at solar minimum than at solar maximum. However, mesopause region H density from the Mass-Spectrometer-Incoherent-Scatter (National Research Laboratory Mass-Spectrometer-Incoherent-Scatter 00 (NRLMSISE-00)) empirical model has reversed seasonal variation compared to WACCM-X and SABER. From the mesopause to the upper thermosphere, H density simulated by WACCM-X switches its solar cycle variation twice, and seasonal dependence once, and these changes of solar cycle and seasonal variability occur in the lower thermosphere ( 95 to 130 km), whereas H from NRLMSISE-00 does not change solar cycle and seasonal dependence from the mesopause through the thermosphere. In the upper thermosphere (above 150 km), H density simulated by WACCM-X is higher at solar minimum than at solar maximum, higher in winter than in summer, and also higher during nighttime than daytime. The amplitudes of these variations are on the order of factors of 10, 2, and 2, respectively. This is consistent with NRLMSISE-00.

Solar Minimum

NASA Astrophysics Data System (ADS)

Lopresto, James C.; Mathews, John; Manross, Kevin

1995-12-01

Calcium K plage, H alpha plage and sunspot area have been monitored daily on the INTERNET since November of 1992. The plage and sunspot area have been measured by image processing. The purpose of the project is to investigate the degree of correlation between plage area and solar irradiance. The plage variation shows the expected variation produced by solar rotation and the longer secular changes produced by the solar cycle. The H alpha and sunspot plage area reached a minimum in about late 1994 or early 1995. This is in agreement with the K2 spectral index obtained daily from Sacramento Peak Observatory. The Calcium K plage area minimum seems delayed with respect to the others mentioned above. The minimum of the K line plage area is projected to come within the last few months of 1995.

Scale Height variations with solar cycle in the ionosphere of Mars

NASA Astrophysics Data System (ADS)

Sanchez-Cano, Beatriz; Lester, Mark; Witasse, Olivier; Milan, Stephen E.; Hall, Benjamin E. S.; Cartacci, Marco; Radicella, Sandro M.; Blelly, Pierre-Louis

2015-04-01

The Mars Advanced Radar for Subsurface and Ionospheric Sounding (MARSIS) on board the Mars Express spacecraft has been probing the topside of the ionosphere of Mars since June 2005, covering currently almost one solar cycle. A good knowledge of the behaviour of the ionospheric variability for a whole solar period is essential since the ionosphere is strongly dependent on solar activity. Using part of this dataset, covering the years 2005 - 2012, differences in the shape of the topside electron density profiles have been observed. These variations seem to be linked to changes in the ionospheric temperature due to the solar cycle variation. In particular, Mars' ionospheric response to the extreme solar minimum between end-2007 and end-2009 followed a similar pattern to the response observed in the Earth's ionosphere, despite the large differences related to internal origin of the magnetic field between both planets. Plasma parameters such as the scale height as a function of altitude, the main peak characteristics (altitude, density), the total electron content (TEC), the temperatures, and the ionospheric thermal pressures show variations related to the solar cycle. The main changes in the topside ionosphere are detected during the period of very low solar minimum, when ionospheric cooling occurs. The effect on the scale height is analysed in detail. In contrast, a clear increase of the scale height is observed during the high solar activity period due to enhanced ionospheric heating. The scale height variation during the solar cycle has been empirically modelled. The results have been compared with other datasets such as radio-occultation and retarding potential analyser data from old missions, especially in low solar activity periods (e.g. Mariner 4, Viking 1 and 2 landers), as well as with numerical modelling.

Potential impacts of a future Grand Solar Minimum on decadal regional climate change and interannual hemispherical climate variability

NASA Astrophysics Data System (ADS)

Spiegl, Tobias; Langematz, Ulrike

2016-04-01

The political, technical and socio-economic developments of the next decades will determine the magnitude of 21st century climate change, since they are inextricably linked to future anthropogenic greenhouse gas emissions. To assess the range of uncertainty that is related to these developments, it is common to assume different emission scenarios for 21st climate projections. While the uncertainties associated with the anthropogenic greenhouse gas forcing have been studied intensely, the contribution of natural climate drivers (particularly solar variability) to recent and future climate change are subject of intense debate. The past 1,000 years featured at least 5 excursions (lasting 60-100 years) of exceptionally low solar activity, induced by a weak magnetic field of the Sun, so called Grand Solar Minima. While the global temperature response to such a decrease in solar activity is assumed to be rather small, nonlinear mechanisms in the climate system might amplify the regional temperature signal. This hypothesis is supported by the last Grand Solar Minimum (the Maunder Minimum, 1645-1715) which coincides with the Little Ice Age, an epoch which is characterized by severe cold and hardship over Europe, North America and Asia. The long-lasting minimum of Solar Cycle 23 as well as the overall weak maximum of Cycle 24 reveal the possibility for a return to Grand Solar Minimum conditions within the next decades. The quantification of the implications of such a projected decrease in solar forcing is of ultimate importance, given the on-going public discussion of the role of carbon dioxide emissions for global warming, and the possible role a cooling due to decreasing solar activity could be ascribed to. Since there is still no clear consensus about the actual strength of the Maunder Minimum, we used 3 acknowledged solar reconstruction datasets that show significant differences in both, total solar irradiance (TSI) and spectral irradiance (SSI) to simulate a future Grand Solar Minimum under RCP6.0 conditions. The results obtained were compared to a RCP6.0 simulation that was carried out using the CCMI recommendations for a 21st century solar forcing. We used the ECHAM/MESSy Atmospheric Chemistry (EMAC) chemistry-climate model that incorporates interactive ozone chemistry, a high-resolution shortwave radiation scheme, a high model top (0.01 hPa) and is coupled to a 3D ocean general circulation model. We focused on the regional responses to a future Grand Solar Minimum and interannual variability patterns (i.e. the Northern and Southern Annular Mode (NAM/SAM)).

Solar photospheric network properties and their cycle variation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thibault, K.; Charbonneau, P.; Béland, M., E-mail: kim@astro.umontreal.ca-a, E-mail: paulchar@astro.umontreal.ca-b, E-mail: michel.beland@calculquebec.ca-c

We present a numerical simulation of the formation and evolution of the solar photospheric magnetic network over a full solar cycle. The model exhibits realistic behavior as it produces large, unipolar concentrations of flux in the polar caps, a power-law flux distribution with index –1.69, a flux replacement timescale of 19.3 hr, and supergranule diameters of 20 Mm. The polar behavior is especially telling of model accuracy, as it results from lower-latitude activity, and accumulates the residues of any potential modeling inaccuracy and oversimplification. In this case, the main oversimplification is the absence of a polar sink for the flux,more » causing an amount of polar cap unsigned flux larger than expected by almost one order of magnitude. Nonetheless, our simulated polar caps carry the proper signed flux and dipole moment, and also show a spatial distribution of flux in good qualitative agreement with recent high-latitude magnetographic observations by Hinode. After the last cycle emergence, the simulation is extended until the network has recovered its quiet Sun initial condition. This permits an estimate of the network relaxation time toward the baseline state characterizing extended periods of suppressed activity, such as the Maunder Grand Minimum. Our simulation results indicate a network relaxation time of 2.9 yr, setting 2011 October as the soonest the time after which the last solar activity minimum could have qualified as a Maunder-type Minimum. This suggests that photospheric magnetism did not reach its baseline state during the recent extended minimum between cycles 23 and 24.« less

Spotless

NASA Technical Reports Server (NTRS)

2008-01-01

Everything runs in cycles and what goes up must come down. We hear that a lot these days. The topic of conversation is of course the sun. The solar cycle takes 11 years to go from sunspot minimum to maximum and back to minimum. The cycle is driven by changes in the Sun's magnetic field, and is actually a 22-year cycle: during the second 11 years the magnetic polarity of the solar field is reversed. The Solar and Heliospheric Observatory satellite (or SOHO for short), a joint ESA and NASA mission, has been watching the sun since 1995. Rarely is the sun as quiet as it was on September 27, 2008 - as shown in the visible-light image above left, there were absolutely no sunspots to be seen. If the activity stays this low, this might be the most inactive the Sun has been since the dawn of the space age. This still pales in comparison to the 17th century when for a period of 70 years (called the Maunder Minimum) there were no reported sunspots. Some scientists believe the Maunder Minimum responsible for a 'Little Ice Age' and the sound of some violins. The image on the right, taken 3 days later in extreme UV light, shows the formation of two active regions (in the circles) but both faded away before becoming full-fledged spots. So how low will it go? Only time will tell.

THE MINIMUM OF SOLAR CYCLE 23: AS DEEP AS IT COULD BE?

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muñoz-Jaramillo, Andrés; Longcope, Dana W.; Senkpeil, Ryan R.

2015-05-01

In this work we introduce a new way of binning sunspot group data with the purpose of better understanding the impact of the solar cycle on sunspot properties and how this defined the characteristics of the extended minimum of cycle 23. Our approach assumes that the statistical properties of sunspots are completely determined by the strength of the underlying large-scale field and have no additional time dependencies. We use the amplitude of the cycle at any given moment (something we refer to as activity level) as a proxy for the strength of this deep-seated magnetic field. We find that themore » sunspot size distribution is composed of two populations: one population of groups and active regions and a second population of pores and ephemeral regions. When fits are performed at periods of different activity level, only the statistical properties of the former population, the active regions, are found to vary. Finally, we study the relative contribution of each component (small-scale versus large-scale) to solar magnetism. We find that when hemispheres are treated separately, almost every one of the past 12 solar minima reaches a point where the main contribution to magnetism comes from the small-scale component. However, due to asymmetries in cycle phase, this state is very rarely reached by both hemispheres at the same time. From this we infer that even though each hemisphere did reach the magnetic baseline, from a heliospheric point of view the minimum of cycle 23 was not as deep as it could have been.« less

Solar activity during the deep minimum of 2009

NASA Astrophysics Data System (ADS)

Sylwester, Janusz; Siarkowski, Marek; Gburek, Szymon; Gryciuk, Magdalena; Kepa, Anna; Kowaliński, Mirosław; Mrozek, Tomek; Phillips, Kenneth J. H.; Podgórski, Piotr; Sylwester, Barbara

2014-12-01

We discuss the character of the unusually deep solar activity minimum of 2009 between Solar Cycles 23 and 24. Levels of solar activity in various parts of the solar atmosphere -- photosphere, chromosphere, transition region, and corona -- were observed to be at their lowest for a century. The soft X-ray emission from the corona (hot outer part of the Sun's atmosphere) was measured throughout most of 2009 with the Polish-built SphinX spectrophotometer. Unlike other X-ray monitoring spacecraft, this sensitive spacecraft-borne instrument was able to continue measurements throughout this extended period of low activity.

The Fraction of Interplanetary Coronal Mass Ejections That Are Magnetic Clouds: Evidence for a Solar Cycle Variation

NASA Technical Reports Server (NTRS)

Richardson, I. G.; Cane, H. V.

2004-01-01

"Magnetic clouds" (MCs) are a subset of interplanetary coronal mass ejections (ICMEs) characterized by enhanced magnetic fields with an organized rotation in direction, and low plasma beta. Though intensely studied, MCs only constitute a fraction of all the ICMEs that are detected in the solar wind. A comprehensive survey of ICMEs in the near- Earth solar wind during the ascending, maximum and early declining phases of solar cycle 23 in 1996 - 2003 shows that the MC fraction varies with the phase of the solar cycle, from approximately 100% (though with low statistics) at solar minimum to approximately 15% at solar maximum. A similar trend is evident in near-Earth observations during solar cycles 20 - 21, while Helios 1/2 spacecraft observations at 0.3 - 1.0 AU show a weaker trend and larger MC fraction.

Project for Solar-Terrestrial Environment Prediction (PSTEP): Towards Predicting Next Solar Cycle

NASA Astrophysics Data System (ADS)

Imada, S.; Iijima, H.; Hotta, H.; Shiota, D.; Kanou, O.; Fujiyama, M.; Kusano, K.

2016-10-01

It is believed that the longer-term variations of the solar activity can affect the Earth's climate. Therefore, predicting the next solar cycle is crucial for the forecast of the "solar-terrestrial environment". To build prediction schemes for the activity level of the next solar cycle is a key for the long-term space weather study. Although three-years prediction can be almost achieved, the prediction of next solar cycle is very limited, so far. We are developing a five-years prediction scheme by combining the Surface Flux Transport (SFT) model and the most accurate measurements of solar magnetic fields as a part of the PSTEP (Project for Solar-Terrestrial Environment Prediction),. We estimate the meridional flow, differential rotation, and turbulent diffusivity from recent modern observations (Hinode and Solar Dynamics Observatory). These parameters are used in the SFT models to predict the polar magnetic fields strength at the solar minimum. In this presentation, we will explain the outline of our strategy to predict the next solar cycle. We also report the present status and the future perspective of our project.

Solar wind velocity and temperature in the outer heliosphere

NASA Technical Reports Server (NTRS)

Gazis, P. R.; Barnes, A.; Mihalov, J. D.; Lazarus, A. J.

1994-01-01

At the end of 1992, the Pioneer 10, Pioneer 11, and Voyager 2 spacecraft were at heliocentric distances of 56.0, 37.3, and 39.0 AU and heliographic latitudes of 3.3 deg N, 17.4 deg N, and 8.6 deg S, respectively. Pioneer 11 and Voyager 2 are at similar celestial longitudes, while Pioneer 10 is on the opposite side of the Sun. All three spacecraft have working plasma analyzers, so intercomparison of data from these spacecraft provides important information about the global character of the solar wind in the outer heliosphere. The averaged solar wind speed continued to exhibit its well-known variation with solar cycle: Even at heliocentric distances greater than 50 AU, the average speed is highest during the declining phase of the solar cycle and lowest near solar minimum. There was a strong latitudinal gradient in solar wind speed between 3 deg and 17 deg N during the last solar minimum, but this gradient has since disappeared. The solar wind temperature declined with increasing heliocentric distance out to a heliocentric distance of at least 20 AU; this decline appeared to continue at larger heliocentric distances, but temperatures in the outer heliosphere were suprisingly high. While Pioneer 10 and Voyager 2 observed comparable solar wind temperatures, the temperature at Pioneer 11 was significantly higher, which suggests the existence of a large-scale variation of temperature with heliographic longitude. There was also some suggestion that solar wind temperatures were higher near solar minimum.

Structure of the photospheric magnetic field during sector crossings of the heliospheric magnetic field

NASA Astrophysics Data System (ADS)

Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

2017-04-01

The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we study the structure of the photospheric field during the HMF sector crossings during solar cycles 21-24, separately for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at the Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976-2014. We find that the structure of the photospheric field corresponding to the HMF sector crossings, and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle and with solar cycle phase. We find evidence for Hale boundaries in many, but not all ascending, maximum and declining phases of solar cycles but no minimum phase. The most clear Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd cycles 21 and 23, but less systematically during the (+,-) crossings in the southern hemisphere of even cycles 22 and 24. We also find that the Hale structure of cycles 23 and 24 is more systematic than during cycles 21 and 22. This may be due to the weakening activity, which reduces the complexity of the photospheric field and clarifies the Hale pattern. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon. The HMF sector crossings observed at 1AU have only a partial correspondence to Hale boundaries in the photosphere, indicating that the two HMF sectors often originate from the opposite hemispheres across the equator. Our results also give evidence for hemispheric and polarity related differences in the photospheric field between the odd and even solar cycles.

Ionospheric effects of the extreme solar activity of February 1986

NASA Technical Reports Server (NTRS)

Boska, J.; Pancheva, D.

1989-01-01

During February 1986, near the minimum of the 11 year Solar sunspot cycle, after a long period of totally quiet solar activity (R sub z = 0 on most days in January) a period of a suddenly enhanced solar activity occurred in the minimum between solar cycles 21 and 22. Two proton flares were observed during this period. A few other flares, various phenomena accompanying proton flares, an extremely severe geomagnetic storm and strong disturbances in the Earth's ionosphere were observed in this period of enhanced solar activity. Two active regions appeared on the solar disc. The flares in both active regions were associated with enhancement of solar high energy proton flux which started on 4 February of 0900 UT. Associated with the flares, the magnetic storm with sudden commencement had its onset on 6 February 1312 UT and attained its maximum on 8 February (Kp = 9). The sudden enhancement in solar activity in February 1986 was accompanied by strong disturbances in the Earth's ionosphere, SIDs and ionospheric storm. These events and their effects on the ionosphere are discussed.

Evolution of 3D electron density of the solar corona from the minimum to maximum of Solar Cycle 24

NASA Astrophysics Data System (ADS)

Wang, Tongjiang; Reginald, Nelson L.; Davila, Joseph M.; St Cyr, O. C.

2016-10-01

The variability of the solar white-light corona and its connection to the solar activity has been studied for more than a half century. It is widely accepted that the temporal variation of the total radiance of the K-corona follows the solar cycle pattern (e.g., correlated with sunspot number). However, the origin of this variation and its relationships with regard to coronal mass ejections and the solar wind are yet to be clearly understood. COR1-A and -B instruments onboard the STEREO spacecraft have continued to perform high-cadence (5 min) polarized brightness (pB) measurements from two different vantage points from the solar minimum to the solar maximum of Solar Cycle 24. With these pB observations we have reconstructed the 3D coronal density between 1.5-4.0 solar radii for 100 Carrington rotations (CRs) from 2007 to 2014 using the spherically symmetric inversion (SSI) method. We validate these 3D density reconstructions by other means such as tomography, MHD modeling, and pB inversion of LASCO/C2 data. We analyze the solar cycle variations of total coronal mass (or average density) over the global Sun and in two hemispheres, as well as the variations of the streamer area and mean density. We find the short-term oscillations of 8-9 CRs during the ascending and maximum phases through wavelet analysis. We explore the origin of these oscillations based on evolution of the photospheric magnetic flux and coronal structures.

Solar cycle variations of the solar wind

NASA Technical Reports Server (NTRS)

Crooker, N. U.

1983-01-01

Throughout the course of the past one and a half solar cycles, solar wind parameters measured near the ecliptic plane at 1 AU varied in the following way: speed and proton temperature have maxima during the declining phase and minima at solar minimum and are approximately anti-correlated with number density and electron temperature, while magnetic field magnitude and relative abundance of helium roughly follow the sunspot cycle. These variations are described in terms of the solar cycle variations of coronal holes, streamers, and transients. The solar wind signatures of the three features are discussed in turn, with special emphasis on the signature of transients, which is still in the process of being defined. It is proposed that magnetic clouds be identified with helium abundance enhancements and that they form the head of a transient surrounded by streamer like plasma, with an optional shock front. It is stressed that relative values of a parameter through a solar cycle should be compared beginning with the declining phase, especially in the case of magnetic field magnitude.

Solar Spectral Irradiance Variations in 240 - 1600 nm During the Recent Solar Cycles 21 - 23

NASA Astrophysics Data System (ADS)

Pagaran, J.; Weber, M.; Deland, M. T.; Floyd, L. E.; Burrows, J. P.

2011-08-01

Regular solar spectral irradiance (SSI) observations from space that simultaneously cover the UV, visible (vis), and the near-IR (NIR) spectral region began with SCIAMACHY aboard ENVISAT in August 2002. Up to now, these direct observations cover less than a decade. In order for these SSI measurements to be useful in assessing the role of the Sun in climate change, records covering more than an eleven-year solar cycle are required. By using our recently developed empirical SCIA proxy model, we reconstruct daily SSI values over several decades by using solar proxies scaled to short-term SCIAMACHY solar irradiance observations to describe decadal irradiance changes. These calculations are compared to existing solar data: the UV data from SUSIM/UARS, from the DeLand & Cebula satellite composite, and the SIP model (S2K+VUV2002); and UV-vis-IR data from the NRLSSI and SATIRE models, and SIM/SORCE measurements. The mean SSI of the latter models show good agreement (less than 5%) in the vis regions over three decades while larger disagreements (10 - 20%) are found in the UV and IR regions. Between minima and maxima of Solar Cycles 21, 22, and 23, the inferred SSI variability from the SCIA proxy is intermediate between SATIRE and NRLSSI in the UV. While the DeLand & Cebula composite provide the highest variability between solar minimum and maximum, the SIP/Solar2000 and NRLSSI models show minimum variability, which may be due to the use of a single proxy in the modeling of the irradiances. In the vis-IR spectral region, the SCIA proxy model reports lower values in the changes from solar maximum to minimum, which may be attributed to overestimations of the sunspot proxy used in modeling the SCIAMACHY irradiances. The fairly short timeseries of SIM/SORCE shows a steeper decreasing (increasing) trend in the UV (vis) than the other data during the descending phase of Solar Cycle 23. Though considered to be only provisional, the opposite trend seen in the visible SIM data challenges the validity of proxy-based linear extrapolation commonly used in reconstructing past irradiances.

Study the gradient characteristics of the ionosphere at equatorial latitude during the latest cycle of solar activity

NASA Astrophysics Data System (ADS)

Nguyen Thai, Chinh; Temitope Seun, Oluwadare; Le Thi, Nhung; Schuh, Harald

2017-04-01

The sun has its own seasons with an average duration of about 11 years. In this time, the sun enters a period of increased activity called the solar maximum and a period of decreased activity called the solar minimum. Cycles span from one minimum to the next. The current solar cycle is 24, which began on January 4, 2008 and is expected to be ended in 2019. During this period, the ionosphere changes its thickness and its characteristics as well. The change is most complicated and unpredictable at the equatorial latitudes in a band around 150 northward and 150 southward from the equator. Thailand is located in these regions is known as one of the countries most affected by the ionosphere change. Ionospheric information such as the vertical total electron content (VTEC) and scintillation indices can be extracted from the measurements of GNSS dual-frequency receivers. In this study, a Matlab tool is programmed to calculate some ionosphere parameters from the normal RINEX observation file including VTEC value, amplitude scintillation S4 index and others. The value of VTEC at one IGS station in Thailand (13.740N, 100.530E) is computed for almost one full solar cycle, that is 8 years, from 2009 to 2016. From these results, we are able to derive the rules of TEC variation over time and its dependence on solar activity in the equatorial regions. The change of VTEC is estimated in diurnal, seasonal and annual variation for the latest solar cycle. The solar cycle can be represented in several ways, in this paper we use the sunspot number and the F10.7 cm radio flux to describe the solar activity. The correlation coefficients between these solar indices and the monthly maximum of VTEC value are around 0.87, this indicates a high dependence of the ionosphere on solar activity. Besides, a scintillation map derived from GNSS data is displayed to indicate the intensity of scintillation activity.

Simulating the Outer Radiation Belt During the Rising Phase of Solar Cycle 24

NASA Technical Reports Server (NTRS)

Fok, Mei-Ching; Glocer, Alex; Zheng, Qiuhua; Chen, Sheng-Hsien; Kanekal, Shri; Nagai, Tsungunobu; Albert, Jay

2011-01-01

After prolonged period of solar minimum, there has been an increase in solar activity and its terrestrial consequences. We are in the midst of the rising phase of solar cycle 24, which began in January 2008. During the initial portion of the cycle, moderate geomagnetic storms occurred follow the 27 day solar rotation. Most of the storms were accompanied by increases in electron fluxes in the outer radiation belt. These enhancements were often preceded with rapid dropout at high L shells. We seek to understand the similarities and differences in radiation belt behavior during the active times observed during the of this solar cycle. This study includes extensive data and simulations our Radiation Belt Environment Model. We identify the processes, transport and wave-particle interactions, that are responsible for the flux dropout and the enhancement and recovery.

Recent Studies of the Behavior of the Sun's White-Light Corona Over Time

NASA Technical Reports Server (NTRS)

SaintCyr, O. C.; Young, D. E.; Pesnell, W. D.; Lecinski, A.; Eddy, J.

2008-01-01

Predictions of upcoming solar cycles are often related to the nature and dynamics of the Sun's polar magnetic field and its influence on the corona. For the past 30 years we have a more-or-less continuous record of the Sun's white-light corona from groundbased and spacebased coronagraphs. Over that interval, the large scale features of the corona have varied in what we now consider a 'predictable' fashion--complex, showing multiple streamers at all latitudes during solar activity maximum; and a simple dipolar shape aligned with the rotational pole during solar minimum. Over the past three decades the white-light corona appears to be a better indicator of 'true' solar minimum than sunspot number since sunspots disappear for months (even years) at solar minimum. Since almost all predictions of the timing of the next solar maximum depend on the timing of solar minimum, the white-light corona is a potentially important observational discriminator for future predictors. In this contribution we describe recent work quantifying the large-scale appearance of the Sun's corona to correlate it with the sunspot record, especially around solar minimum. These three decades can be expanded with the HAO archive of eclipse photographs which, although sparse compared to the coronagraphic coverage, extends back to 1869. A more extensive understanding of this proxy would give researchers confidence in using the white-light corona as an indicator of solar minimum conditions.

A SOLAR CYCLE LOST IN 1793-1800: EARLY SUNSPOT OBSERVATIONS RESOLVE THE OLD MYSTERY

DOE Office of Scientific and Technical Information (OSTI.GOV)

Usoskin, Ilya G.; Mursula, Kalevi; Arlt, Rainer

2009-08-01

Because of the lack of reliable sunspot observations, the quality of the sunspot number series is poor in the late 18th century, leading to the abnormally long solar cycle (1784-1799) before the Dalton minimum. Using the newly recovered solar drawings by the 18-19th century observers Staudacher and Hamilton, we construct the solar butterfly diagram, i.e., the latitudinal distribution of sunspots in the 1790s. The sudden, systematic occurrence of sunspots at high solar latitudes in 1793-1796 unambiguously shows that a new cycle started in 1793, which was lost in the traditional Wolf sunspot series. This finally confirms the existence of themore » lost cycle that has been proposed earlier, thus resolving an old mystery. This Letter brings the attention of the scientific community to the need of revising the sunspot series in the 18th century. The presence of a new short, asymmetric cycle implies changes and constraints to sunspot cycle statistics, solar activity predictions, and solar dynamo theories, as well as for solar-terrestrial relations.« less

A Topside Equatorial Ionospheric Density and Composition Climatology During and After Extreme Solar Minimum

NASA Technical Reports Server (NTRS)

Klenzing, J. H.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R. F.; Rowland, D. E.

2011-01-01

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth's ionosphere and thermosphere when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Climatological altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the C/NOFS satellite to characterize the shape of the top side ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. [2009], here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

Topside Equatorial Ionospheric Density and Composition During and After Extreme Solar Minimum

NASA Technical Reports Server (NTRS)

Klenzing, J.; Simoes, F.; Ivanov, S.; Heelis, R. A.; Bilitza, D.; Pfaff, R.; Rowland, D.

2011-01-01

During the recent solar minimum, solar activity reached the lowest levels observed during the space age. This extremely low solar activity has accompanied a number of unexpected observations in the Earth s ionosphere-thermosphere system when compared to previous solar minima. Among these are the fact that the ionosphere is significantly contracted beyond expectations based on empirical models. Altitude profiles of ion density and composition measurements near the magnetic dip equator are constructed from the Communication/Navigation Outage Forecast System (C/NOFS) satellite to characterize the shape of the topside ionosphere during the recent solar minimum and into the new solar cycle. The variation of the profiles with respect to local time, season, and solar activity are compared to the IRI-2007 model. Building on initial results reported by Heelis et al. (2009), here we describe the extent of the contracted ionosphere, which is found to persist throughout 2009. The shape of the ionosphere during 2010 is found to be consistent with observations from previous solar minima.

Cosmic Ray Modulation and Radiation Dose of Aircrews During Possible Grand Minimum

NASA Astrophysics Data System (ADS)

Miyake, S.; Kataoka, R.; Sato, T.; Imada, S.; Miyahara, H.; Shiota, D.; Matsumoto, T.; Ueno, H.

2017-12-01

The Sun is exhibiting low solar activity levels since the descending phase of the last solar cycle, and it is likely to be continued as well as in the case of the past grand solar minima. The cosmic-ray modulation, which is the variation of the galactic cosmic ray (GCR) spectrum caused by the heliospheric environmental change, is basically anti-correlated with the solar activity. In the recent weak solar cycle, we thus expect that the flux of GCRs is getting higher than that in the previous solar cycles, leading to the increase in the radiation exposure in the space and atmosphere. In order to quantitatively evaluate the possible solar modulation of GCRs and resultant radiation exposure at flight altitude, we have developed the time-dependent and three-dimensional model of the cosmic-ray modulation. Our model can give the flux of GCRs anywhere in the heliosphere by assuming the variation of the solar wind speed, the strength of the heliospheric magnetic field (HMF), and its tilt angle. We solve the gradient-curvature drift motion of GCRs in the HMF, and therefore reproduce the 22-year variation of the cosmic-ray modulation. We also calculate the neutron monitor counting rate and the radiation dose of aircrews at flight altitude, by the air-shower simulation performed by PHITS (Particle and Heavy Ion Transport code System). In our previous study [1], we calculated the radiation dose at a flight altitude during the coming solar cycle by assuming the variation of the solar wind speed and the strength of the HMF expressed by sinusoidal curve, and obtained that an annual radiation dose of aircrews in 5 years around the next solar minimum will be up to 19% higher than that at the last cycle. In this study, we predict the new model of the heliospheric environmental change on the basis of a prediction model for the sunspot number. The quantitative predictions of the cosmic-ray modulation and the radiation dose at a flight altitude during possible Grand Minimum considering the new model for the heliospheric environmental change will be presented at the meeting. [1] S. Miyake, R. Kataoka, and T. Sato, Space Weather, 15, 589-605, 2017.

Two-parameter model of total solar irradiance variation over the solar cycle

NASA Technical Reports Server (NTRS)

Pap, Judit M.; Willson, Richard C.; Donnelly, Richard F.

1991-01-01

Total solar irradiance measured by the SMM/ACRIM radiometer is modelled from the Photometric Sunspot Index and the Mg II core-to-wing ratio with multiple regression analysis. Considering that the formation of the Mg II line is very similar to that of the Ca II K line, the Mg II core-to-wing ratio, measured by the Nimbus-7 and NOAA9 satellites, is used as a proxy for the bright magnetic elements, including faculae and the magnetic network. It is shown that the relationship between the variations in total solar irradiance and the above solar activity indices depends upon the phase of the solar cycle. Thus, a better fit between total irradiance and its model estimates can be achieved if the irradiance models are calculated for the declining portion and minimum of solar cycle 21, and the rising portion of solar cycle 22, respectively. There is an indication that during the rising portion of solar cycle 22, similar to the maximum time of solar cycle 21, the modelled total irradiance values underestimate the measured values. This suggests that there is an asymmetry in the long-term total irradiance variability.

Predictions of Solar Cycle 24: How are We Doing?

NASA Technical Reports Server (NTRS)

Pesnell, William D.

2016-01-01

Predictions of solar activity are an essential part of our Space Weather forecast capability. Users are requiring usable predictions of an upcoming solar cycle to be delivered several years before solar minimum. A set of predictions of the amplitude of Solar Cycle 24 accumulated in 2008 ranged from zero to unprecedented levels of solar activity. The predictions formed an almost normal distribution, centered on the average amplitude of all preceding solar cycles. The average of the current compilation of 105 predictions of the annual-average sunspot number is 106 +/- 31, slightly lower than earlier compilations but still with a wide distribution. Solar Cycle 24 is on track to have a below-average amplitude, peaking at an annual sunspot number of about 80. Our need for solar activity predictions and our desire for those predictions to be made ever earlier in the preceding solar cycle will be discussed. Solar Cycle 24 has been a below-average sunspot cycle. There were peaks in the daily and monthly averaged sunspot number in the Northern Hemisphere in 2011 and in the Southern Hemisphere in 2014. With the rapid increase in solar data and capability of numerical models of the solar convection zone we are developing the ability to forecast the level of the next sunspot cycle. But predictions based only on the statistics of the sunspot number are not adequate for predicting the next solar maximum. I will describe how we did in predicting the amplitude of Solar Cycle 24 and describe how solar polar field predictions could be made more accurate in the future.

On the prospect of using butterfly diagrams to predict cycle minimum

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

1987-01-01

Features enabling the prediction of the beginning and the length of a solar cycle, in addition to the turning points in the period-growth dichotomy, have been identified based on butterfly diagrams for the period from 1874 to the present. The present results indicate that cycle 21 will be a long-period cycle ending after July 1987. On the assumption that April 1985 was the first occurrence of high latitude new cycle (cycle 22) spots during the decline of cycle 21 (the old cycle), it is suggested that the last occurrence of high latitude old cycle spots was September 1983 and that the minimum for cycle 22 will be about 1986.7 + or - 1.1 yr.

High-latitude spacecraft charging in low-Earth polar orbit

NASA Astrophysics Data System (ADS)

Frooninckx, Thomas B.

Spacecraft charging within the upper ionosphere is commonly thought to be insignificant and thus has received little attention. Recent experimental evidence has shown that electric potential differences as severe as 680 volts can develop between Defense Meteorological Satellite Program (DMSP) polar-orbiting (840 kilometers) spacecraft and their high-latitude environment. To explore space vehicle charging in this region more fully, an analysis was performed using DMSP F6, F7, F8, and F9 satellite precipitating particle and ambient plasma measurements taken during the winters of 1986-87 (solar minimum) and 1989-90 (solar maximum). An extreme solar cycle dependence was discovered as charging occurred more frequently and with greater severity during the period of solar minimum. One hundred seventy charging events ranging from -46 to 1,430 volts were identified, and satellite measurements and Time Dependent Ionospheric Model (TDIM) output were used to characterize the environments which generated and inhibited these potentials. All current sources were considered to determine the cause of the solar cycle dependence.

The magnetic field of the earth - Performance considerations for space-based observing systems

NASA Technical Reports Server (NTRS)

Webster, W. J., Jr.; Taylor, P. T.; Schnetzler, C. C.; Langel, R. A.

1985-01-01

Basic problems inherent in carrying out observations of the earth magnetic field from space are reviewed. It is shown that while useful observations of the core and crustal fields are possible at the peak of the solar cycle, the greatest useful data volume is obtained during solar minimum. During the last three solar cycles, the proportion of data with a planetary disturbance index of less than 2 at solar maximum was in the range 0.4-0.8 in comparison with solar minimum. It is found that current state of the art orbit determination techniques should eliminate orbit error as a problem in gravitational field measurements from space. The spatial resolution obtained for crustal field anomalies during the major satellite observation programs of the last 30 years are compared in a table. The relationship between observing altitude and the spatial resolution of magnetic field structures is discussed. Reference is made to data obtained using the Magsat, the Polar Orbiting Geophysical Observatory (POGO), and instruments on board the Space Shuttle.

Solar Wind Helium Abundance as a Function of Speed and Heliographic Latitude: Variation through a Solar Cycle

NASA Technical Reports Server (NTRS)

Kasper, J. C.; Stenens, M. L.; Stevens, M. L.; Lazarus, A. J.; Steinberg, J. T.; Ogilvie, Keith W.

2006-01-01

We present a study of the variation of the relative abundance of helium to hydrogen in the solar wind as a function of solar wind speed and heliographic latitude over the previous solar cycle. The average values of A(sub He), the ratio of helium to hydrogen number densities, are calculated in 25 speed intervals over 27-day Carrington rotations using Faraday Cup observations from the Wind spacecraft between 1995 and 2005. The higher speed and time resolution of this study compared to an earlier work with the Wind observations has led to the discovery of three new aspects of A(sub He), modulation during solar minimum from mid-1995 to mid-1997. First, we find that for solar wind speeds between 350 and 415 km/s, A(sub He), varies with a clear six-month periodicity, with a minimum value at the heliographic equatorial plane and a typical gradient of 0.01 per degree in latitude. For the slow wind this is a 30% effect. We suggest that the latitudinal gradient may be due to an additional dependence of coronal proton flux on coronal field strength or the stability of coronal loops. Second, once the gradient is subtracted, we find that A(sub He), is a remarkably linear function of solar wind speed. Finally, we identify a vanishing speed, at which A(sub He), is zero, is 259 km/s and note that this speed corresponds to the minimum solar wind speed observed at one AU. The vanishing speed may be related to previous theoretical work in which enhancements of coronal helium lead to stagnation of the escaping proton flux. During solar maximum the A(sub He), dependences on speed and latitude disappear, and we interpret this as evidence of two source regions for slow solar wind in the ecliptic plane, one being the solar minimum streamer belt and the other likely being active regions.

DMSP Auroral Charging at Solar Cycle 24 Maximum

NASA Technical Reports Server (NTRS)

Chandler, M.; Parker, L. Neergaard; Minow, J. I.

2013-01-01

It has been well established that polar orbiting satellites can experience mild to severe auroral charging levels (on the order of a few hundred volts to few kilovolts negative frame potentials) during solar minimum conditions. These same studies have shown a strong reduction in charging during the rising and declining phases of the past few solar cycles with a nearly complete suppression of auroral charging at solar maximum. Recently, we have observed examples of high level charging during the recent approach to Solar Cycle 24 solar maximum conditions not unlike those reported by Frooninckx and Sojka. These observations demonstrate that spacecraft operations during solar maximum cannot be considered safe from auroral charging when solar activity is low. We present a survey of auroral charging events experienced by the Defense Meteorological Satellite Program (DMSP) F16 satellite during Solar Cycle 24 maximum conditions. We summarize the auroral energetic particle environment and the conditions necessary for charging to occur in this environment, we describe how the lower than normal solar activity levels for Solar Cycle 24 maximum conditions are conducive to charging in polar orbits, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period.

Solar Surface Velocity in the Large Scale estimated by Magnetic Element Tracking Method

NASA Astrophysics Data System (ADS)

Fujiyama, M.; Imada, S.; Iijima, H.; Machida, S.

2017-12-01

The 11years variation in the solar activity is one of the important sources of decadal variation in the solar-terrestrial environment. Therefore, predicting the solar cycle activity is crucial for the space weather. To build the prediction schemes for the next solar cycle is a key for the long-term space weather study. Recently, the relationship between polar magnetic field at the solar minimum and next solar cycle activity is intensively discussed. Nowadays, many people believe that the polar magnetic field at the solar minimum is one of the best predictor for the next solar cycle. To estimate polar magnetic field, Surface Flux Transport (SFT) model have been often used. On the other hand, SFT model needs several parameters, for example Meridional circulation, differential rotation, turbulent diffusion etc.. So far, those parameters have not been fully understood, and their uncertainties may affect the accuracy of the prediction. In this study, we try to discuss the parameters which are used in SFT model. We focus on two kinds of the solar surface motions, Differential rotation and Meridional circulation. First, we have developed Magnetic Element Tracking (MET) module, which is able to obtain the surface velocity by using the magnetic field data. We have used SOHO/MDI and SDO/HMI for the magnetic field data. By using MET, we study the solar surface motion over 2 cycle (nearly 24 years), and we found that the velocity variation is related to the active region belt. This result is consistent with [Hathaway et al., 2011]. Further, we apply our module to the Hinode/SOT data which spatial resolution is high. Because of its high resolution, we can discuss the surface motion close to the pole which has not been discussed enough. Further, we discuss the relationship between the surface motion and the magnetic field strength and the location of longitude.

Solar cycle dependence of the heliospheric shape deduced from a global MHD simulation of the interaction process between a nonuniform time-dependent solar wind and the local interstellar medium

NASA Astrophysics Data System (ADS)

Tanaka, T.; Washimi, H.

1999-06-01

The global structure of the solar wind/very local interstellar medium interaction is studied from a fully three-dimensional time-dependent magnetohydrodynamic model, in which the solar wind speed increases from 400 to 800 km/s in going from the ecliptic to pole and the heliolatitude of the low-high-speed boundary changes from 30° to 80° in going from the solar minimum to solar maximum. In addition, the interplanetary magnetic field (IMF) changes its polarity at the solar maximum. As a whole, the shapes of the terminal shock (TS) and heliopause (HP) are elongated along the solar polar axis owing to a high solar wind ram pressure over the poles. In the ecliptic plane, the heliospheric structure changes little throughout a solar cycle. The TS in this plane shows a characteristic bullet-shaped structure. In the polar plane, on the other hand, the shape of the TS exhibits many specific structures according to the stage of the solar cycle. These structures include the polygonal configuration of the polar TS seen around the solar minimum, the mesa- and terrace-shaped TSs in the high- and low-speed solar wind regions seen around the ascending phase, and the chimney-shaped TS in the high-speed solar wind region seen around the solar maximum. These structures are formed from different combinations of right-angle shock, oblique shock, and steep oblique shock so as to transport the heliosheath plasma most efficiently toward the heliotail (HT). In the HT, the hot and weakly-magnetized plasma from the high-heliolatitude TS invades as far as the ecliptic plane. A weakly time-dependent recirculation flow in the HT is a manifestation of invading flow. Distributions of magnetic field in the HT, which are a pile-up of the compressed MF over several solar cycles, are modified by the flow from high-heliolatitude.

What the Sunspot Record Tells Us About Space Climate

NASA Technical Reports Server (NTRS)

Hathaway, David H.; Wilson, Robert M.

2004-01-01

The records concerning the number, sizes, and positions of sunspots provide a direct means of characterizing solar activity over nearly 400 years. Sunspot numbers are strongly correlated with modem measures of solar activity including: 10.7-cm radio flux, total irradiance, x-ray flares, sunspot area, the baseline level of geomagnetic activity, and the flux of galactic cosmic rays. The Group Sunspot Number provides information on 27 sunspot cycles, far more than any of the modem measures of solar activity, and enough to provide important details about long-term variations in solar activity or Space Climate. The sunspot record shows: 1) sunspot cycles have periods of 131 plus or minus 14 months with a normal distribution; 2) sunspot cycles are asymmetric with a fast rise and slow decline; 3) the rise time from minimum to maximum decreases with cycle amplitude; 4) large amplitude cycles are preceded by short period cycles; 5 ) large amplitude cycles are preceded by high minima; 6) although the two hemispheres remain linked in phase, there are significant asymmetries in the activity in each hemisphere; 7) the rate at which the active latitudes drift toward the equator is anti-correlated with the cycle period, 8) the rate at which the active latitudes drift toward the equator is positively correlated with the amplitude of the cycle after the next; 9) there has been a significant secular increase in the amplitudes of the sunspot cycles since the end of the Maunder Minimum (1715); and 10) there is weak evidence for a quasi-periodic variation in the sunspot cycle amplitudes with a period of about 90 years. These characteristics indicate that the next solar cycle should have a maximum smoothed sunspot number of about 1.45 plus or minus 30 in 2010 while the following cycle should have a maximum of about 70 plus or minus 30 in 2023.

Sunspot Time Series: Passive and Active Intervals

NASA Astrophysics Data System (ADS)

Zięba, S.; Nieckarz, Z.

2014-07-01

Solar activity slowly and irregularly decreases from the first spotless day (FSD) in the declining phase of the old sunspot cycle and systematically, but also in an irregular way, increases to the new cycle maximum after the last spotless day (LSD). The time interval between the first and the last spotless day can be called the passive interval (PI), while the time interval from the last spotless day to the first one after the new cycle maximum is the related active interval (AI). Minima of solar cycles are inside PIs, while maxima are inside AIs. In this article, we study the properties of passive and active intervals to determine the relation between them. We have found that some properties of PIs, and related AIs, differ significantly between two group of solar cycles; this has allowed us to classify Cycles 8 - 15 as passive cycles, and Cycles 17 - 23 as active ones. We conclude that the solar activity in the PI declining phase (a descending phase of the previous cycle) determines the strength of the approaching maximum in the case of active cycles, while the activity of the PI rising phase (a phase of the ongoing cycle early growth) determines the strength of passive cycles. This can have implications for solar dynamo models. Our approach indicates the important role of solar activity during the declining and the rising phases of the solar-cycle minimum.

MODULATION OF GALACTIC COSMIC RAYS OBSERVED AT L1 IN SOLAR CYCLE 23

DOE Office of Scientific and Technical Information (OSTI.GOV)

Fludra, A., E-mail: Andrzej.Fludra@stfc.ac.uk

2015-01-20

We analyze a unique 15 yr record of galactic cosmic-ray (GCR) measurements made by the SOHO Coronal Diagnostic Spectrometer NIS detectors, recording integrated GCR numbers with energies above 1.0 GeV between 1996 July and 2011 June. We are able to closely reproduce the main features of the SOHO/CDS GCR record using the modulation potential calculated from neutron monitor data by Usoskin et al. The GCR numbers show a clear solar cycle modulation: they decrease by 50% from the 1997 minimum to the 2000 maximum of the solar cycle, then return to the 1997 level in 2007 and continue to rise, in 2009 Decembermore » reaching a level 25% higher than in 1997. This 25% increase is in contrast with the behavior of Ulysses/KET GCR protons extrapolated to 1 AU in the ecliptic plane, showing the same level in 2008-2009 as in 1997. The GCR numbers are inversely correlated with the tilt angle of the heliospheric current sheet. In particular, the continued increase of SOHO/CDS GCRs from 2007 until 2009 is correlated with the decrease of the minimum tilt angle from 30° in mid-2008 to 5° in late 2009. The GCR level then drops sharply from 2010 January, again consistent with a rapid increase of the tilt angle to over 35°. This shows that the extended 2008 solar minimum was different from the 1997 minimum in terms of the structure of the heliospheric current sheet.« less

Solar-Iss a New Solar Reference Spectrum Covering the Far UV to the Infrared (165 to 3088 Nm) Based on Reanalyzed Solar/solspec Cycle 24 Observations

NASA Astrophysics Data System (ADS)

Damé, L.; Meftah, M.; Irbah, A.; Hauchecorne, A.; Bekki, S.; Bolsée, D.; Pereira, N.; Sluse, D.; Cessateur, G.

2017-12-01

Since April 5, 2008 and until February 15, 2017, the SOLSPEC (SOLar SPECtrometer) spectro-radiometer of the SOLAR facility on the International Space Station performed accurate measurements of Solar Spectral Irradiance (SSI) from the far ultraviolet to the infrared (165 nm to 3088 nm). These measurements, unique by their large spectral coverage and long time range, are of primary importance for a better understanding of solar physics and of the impact of solar variability on climate (via Earth's atmospheric photochemistry), noticeably through the "top-down" mechanism amplifying ultraviolet (UV) solar forcing effects on the climate (UV affects stratospheric dynamics and temperatures, altering interplanetary waves and weather patterns both poleward and downward to the lower stratosphere and troposphere regions). SOLAR/SOLSPEC, with almost 9 years of observations covering the essential of the unusual solar cycle 24 from minimum in 2008 to maximum, allowed to establish new reference solar spectra from UV to IR (165 to 3088 nm) at minimum (beginning of mission) and maximum of activity. The complete reanalysis was possible thanks to revised engineering corrections, improved calibrations and advanced procedures to account for thermal, aging and pointing corrections. The high quality and sensitivity of SOLSPEC data allow to follow temporal variability in UV but also in visible along the cycle. Uncertainties on these measurements are evaluated and results, absolute reference spectra and variability, are compared with other measurements (WHI, ATLAS-3, SCIAMACHY, SORCE/SOLSTICE, SORCE/SIM) and models (SATIRE-S, NRLSSI, NESSY)

Encore of the Bashful ballerina in solar cycle 23

NASA Astrophysics Data System (ADS)

Mursula, K.; Virtanen, I. I.

2009-04-01

The rotation averaged location of the heliospheric current sheet has been found to be shifted systematically southward for about three years in the late declining to minimum phase of the solar cycle. This behaviour, called by the concept of the Bashful ballerina, has earlier been shown to be valid at least during the active solar cycle of the last century since the late 1920s. Recently, Zhao et al have analysed the WSO observations and conclude that there is no southward coning in HCS or north-south difference in the heliospheric magnetic field during the late declining phase of solar cycle 23. In disagreement with these results, we find that there is a similar but smaller southward shift of the HCS and dominance of the northern field area as in all previous solar cycles. The present smaller asymmetry is in agreement with an earlier observation based on long-term geomagnetic activity that solar hemispheric asymmetry is larger during highly active solar cycles. Moreover, we connect the smallness of shift to the structure of the solar magnetic field with an exceptionally large tilt. We also discuss the cause of the differences between the two approaches reaching different conclusions.

Quiet-Time Suprathermal (˜0.1 - 200 keV) Electrons in the Solar Wind

NASA Astrophysics Data System (ADS)

Wang, Linghua; Yang, Liu; Tao, Jiawei; Zong, Qiugang; Li, Gang; Wimmer-Schweingruber, Robert; He, Jiansen; Tu, Chuanyi; Bale, Stuart

2017-04-01

We present a statistical survey of the energy spectrum of solar wind suprathermal (˜0.1-200 keV) electrons measured by the WIND 3DP instrument at 1 AU during quiet times at the minimum and maximum of solar cycles 23 and 24. The observed energy spectrum of both (beaming) strahl and (isotropic) halo electrons at ˜0.1-1.5 keV generally fits to a Kappa distribution function with an index κ and effective temperature Teff, while the observed energy spectrum of nearly isotropic superhalo electrons at ˜20-200 keV generally fits to a power-law function, J ˜ E-β. We find a strong positive correlation between κ and Teff for both strahl and halo electrons, and a strong positive correlation between the strahl density and halo density. In both solar cycles, κ is larger at solar minimum than at solar maximum for both strahl and halo electrons. For the superhalo population, the spectral index β ranges from ˜1.6 to ˜3.7 and the integrated density nsup ranges from 10-8 cm-3 to 10-5 cm-3, with no clear association with the sunspot number. In solar cycle 23 (24), the distribution of β has a broad maximum between 2.4 and 2.8 (2.0 and 2.4). All the strahl, halo and superhalo populations show no obvious correlation with the solar wind core population. These results reflect the nature of the generation of solar wind suprathermal electrons.

Galactic CR in the Heliosphere according to NM data, 3. Results for even solar cycles 20 and 22.

NASA Astrophysics Data System (ADS)

Dorman, L.; Dorman, I.; Iucci, N.; Parisi, M.; Villoresi, G.; Zukerman, I.

We found that the maximum of correlation coefficient between cosmic ray (CR) intensity and solar activity (SA) variations is occurred for even cycles 20 and 22 for about two-three times in the shorter time than for odd cycles 19 and 21. We came to conclusion that this difference is caused by CR drift effects: during even cycle drifts produced the small increasing of CR global modulation (additional to the caused by convection-diffusion mechanism) in the period from minimum to maximum of SA, and after the maximum of SA up to the minimum- about the same decreasing of CR modulation. This gives sufficient decreasing of observed time lag between CR and- SA in even solar cycles. We analyzed monthly and 11 months smoothed data of (CR) intensity observed by neutron monitors with different cut-off rigidities for even solar cycles 20 and 22. We use a special model described the connection between solar activity (characterized by monthly sunspot numbers) and CR convection- diff usion global modulation with taking into account time-lag of processes in the Heliosphere relative to the active processes on the Sun. For taking into account drifts we use models described in literature. In the first we correct observed long-term CR modulation on drifts with different amplitudes from 0 (no drifts), then 0.15%, 0.25%,... up to 4%. For each expected amplitude of drifts we determine the correlation coefficient between expected CR variations and observed by neutron monitors with different cut - off rigidities for different times of solar wind transportation from the Sun to the boundary of the modulation region from 1 to 60 average months (it corresponds approximately to dimension of modulation region from about 6 to 360 AU). We compare observed res ults for even solar cycles 20 and 22.

The relationship of the large-scale solar field to the interplanetary magnetic field - What will Ulysses find?

NASA Technical Reports Server (NTRS)

Hoeksema, J. T.

1986-01-01

Using photospheric magnetic field observations obtained at the Stanford Wilcox Solar Observatory, results from a potential field model for the present solar cycle are given, and qualitative predictions of the IMF that Ulysses may encounter are presented. Results indicate that the IMF consists of large regions of opposite polarity separated by a neutral sheet (NS) (extended to at least 50 deg) and a four-sector structure near solar minimum (produced by small quadripolar NS warps). The latitudinal extent of the NS increases following minimum and the structure near maximum includes multiple NSs, while a simplified IMF is found during the declining phase.

CORONAL DYNAMIC ACTIVITIES IN THE DECLINING PHASE OF A SOLAR CYCLE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jang, Minhwan; Choe, G. S.; Woods, T. N.

2016-12-10

It has been known that some solar activity indicators show a double-peak feature in their evolution through a solar cycle, which is not conspicuous in sunspot number. In this Letter, we investigate the high solar dynamic activity in the declining phase of the sunspot cycle by examining the evolution of polar and low-latitude coronal hole (CH) areas, splitting and merging events of CHs, and coronal mass ejections (CMEs) detected by SOHO /LASCO C3 in solar cycle 23. Although the total CH area is at its maximum near the sunspot minimum, in which polar CHs prevail, it shows a comparable secondmore » maximum in the declining phase of the cycle, in which low-latitude CHs are dominant. The events of CH splitting or merging, which are attributed to surface motions of magnetic fluxes, are also mostly populated in the declining phase of the cycle. The far-reaching C3 CMEs are also overpopulated in the declining phase of the cycle. From these results we suggest that solar dynamic activities due to the horizontal surface motions of magnetic fluxes extend far in the declining phase of the sunspot cycle.« less

A Snapshot of the Sun Near Solar Minimum: The Whole Heliosphere Interval

NASA Technical Reports Server (NTRS)

Thompson, Barbara J.; Gibson, Sarah E.; Schroeder, Peter C.; Webb, David F.; Arge, Charles N.; Bisi, Mario M.; de Toma, Giuliana; Emery, Barbara A.; Galvin, Antoinette B.; Haber, Deborah A.;

Long dance of the bashful ballerina

NASA Astrophysics Data System (ADS)

Hiltula, T.; Mursula, K.

2006-02-01

In this letter we extend our earlier analysis of the north-south asymmetry of the heliospheric current sheet (HCS) using a recent data set of heliospheric magnetic field (HMF) sector polarities extracted from ground-based magnetic observations. We find that the heliospheric current sheet is similarly southward coned or shifted during the late declining to minimum phase of the solar cycle in the early part of the studied data interval (1926-1955), as earlier found for the more recent solar cycles. Accordingly, the HCS has been southward shifted; that is, the solar ballerina has been bashful at least during the last 80 years. We also discuss solar cycle 19 which presents a period of a very curious behaviour for the HCS with an exceptionally large HMF toward sector dominance in 1957, the year of cycle 19 maximum, and an equally strong HMF away sector dominance in 1960, the time of final solar polarity reversal.

Application of the Maximum Amplitude-Early Rise Correlation to Cycle 23

NASA Technical Reports Server (NTRS)

Willson, Robert M.; Hathaway, David H.

2004-01-01

On the basis of the maximum amplitude-early rise correlation, cycle 23 could have been predicted to be about the size of the mean cycle as early as 12 mo following cycle minimum. Indeed, estimates for the size of cycle 23 throughout its rise consistently suggested a maximum amplitude that would not differ appreciably from the mean cycle, contrary to predictions based on precursor information. Because cycle 23 s average slope during the rising portion of the solar cycle measured 2.4, computed as the difference between the conventional maximum (120.8) and minimum (8) amplitudes divided by the ascent duration in months (47), statistically speaking, it should be a cycle of shorter period. Hence, conventional sunspot minimum for cycle 24 should occur before December 2006, probably near July 2006 (+/-4 mo). However, if cycle 23 proves to be a statistical outlier, then conventional sunspot minimum for cycle 24 would be delayed until after July 2007, probably near December 2007 (+/-4 mo). In anticipation of cycle 24, a chart and table are provided for easy monitoring of the nearness and size of its maximum amplitude once onset has occurred (with respect to the mean cycle and using the updated maximum amplitude-early rise relationship).

A seven-month solar cycle observed with the Langmuir probe on Pioneer Venus Orbiter

NASA Technical Reports Server (NTRS)

Hoegy, W. R.; Wolff, C. L.

1989-01-01

Data collected by the Langmuir probe aboard the Pioneer Venus orbiter (PVO) over the years 1979 though 1987 were normalized to remove the long-period 11-year solar maximum to minimum trend and were analyzed for periodicity. Results yield evidence for the existence of an approximately 7-month solar cycle, which was also observed from SME Lyman alpha and 2800-MHz radio flux measurements carried out from an earth-based platform. This coincidence suggests that the cycle is an intrinsic periodicity in the solar output. The cycle has a frequency independent of the orbital frequency of the PVO and is distinct from a 'rotating beacon' cycle whose period depends on the orbital motion of the PVO about the sun. The second most dominant cycle discovered was a 5-month period. Results of an oscillation model of solar periodicity indicate that the 7-month and 5-month cycles are caused by long-lived flux enhancements from nonlinear interactions of global oscillation modes in the sun's convective envelope (r modes) and radiative interior (g modes).

Comparative Study of foF2 Measurements with IRI-2007 Model Predictions During Extended Solar Minimum

NASA Technical Reports Server (NTRS)

Zakharenkova, I. E.; Krankowski, A.; Bilitza, D.; Cherniak, Iu.V.; Shagimuratov, I.I.; Sieradzki, R.

2013-01-01

The unusually deep and extended solar minimum of cycle 2324 made it very difficult to predict the solar indices 1 or 2 years into the future. Most of the predictions were proven wrong by the actual observed indices. IRI gets its solar, magnetic, and ionospheric indices from an indices file that is updated twice a year. In recent years, due to the unusual solar minimum, predictions had to be corrected downward with every new indices update. In this paper we analyse how much the uncertainties in the predictability of solar activity indices affect the IRI outcome and how the IRI values calculated with predicted and observed indices compared to the actual measurements.Monthly median values of F2 layer critical frequency (foF2) derived from the ionosonde measurements at the mid-latitude ionospheric station Juliusruh were compared with the International Reference Ionosphere (IRI-2007) model predictions. The analysis found that IRIprovides reliable results that compare well with actual measurements, when the definite (observed and adjusted) indices of solar activityare used, while IRI values based on earlier predictions of these indices noticeably overestimated the measurements during the solar minimum.One of the principal objectives of this paper is to direct attention of IRI users to update their solar activity indices files regularly.Use of an older index file can lead to serious IRI overestimations of F-region electron density during the recent extended solar minimum.

Will Solar Cycles 25 and 26 Be Weaker than Cycle 24?

NASA Astrophysics Data System (ADS)

Javaraiah, J.

2017-11-01

The study of variations in solar activity is important for understanding the underlying mechanism of solar activity and for predicting the level of activity in view of the activity impact on space weather and global climate. Here we have used the amplitudes (the peak values of the 13-month smoothed international sunspot number) of Solar Cycles 1 - 24 to predict the relative amplitudes of the solar cycles during the rising phase of the upcoming Gleissberg cycle. We fitted a cosine function to the amplitudes and times of the solar cycles after subtracting a linear fit of the amplitudes. The best cosine fit shows overall properties (periods, maxima, minima, etc.) of Gleissberg cycles, but with large uncertainties. We obtain a pattern of the rising phase of the upcoming Gleissberg cycle, but there is considerable ambiguity. Using the epochs of violations of the Gnevyshev-Ohl rule (G-O rule) and the `tentative inverse G-O rule' of solar cycles during the period 1610 - 2015, and also using the epochs where the orbital angular momentum of the Sun is steeply decreased during the period 1600 - 2099, we infer that Solar Cycle 25 will be weaker than Cycle 24. Cycles 25 and 26 will have almost same strength, and their epochs are at the minimum between the current and upcoming Gleissberg cycles. In addition, Cycle 27 is expected to be stronger than Cycle 26 and weaker than Cycle 28, and Cycle 29 is expected to be stronger than both Cycles 28 and 30. The maximum of Cycle 29 is expected to represent the next Gleissberg maximum. Our analysis also suggests a much lower value (30 - 40) for the maximum amplitude of the upcoming Cycle 25.

Spectral solar UV irradiance data for cycle 21

NASA Astrophysics Data System (ADS)

DeLand, Matthew T.; Cebula, Richard P.

2001-10-01

The Nimbus 7 Solar Backscatter Ultraviolet (SBUV) instrument, which began taking data in November 1978, was the first instrument to make solar UV irradiance measurements covering both the minimum and maximum activity levels of a solar cycle. The currently archived irradiance data set was processed with an instrument characterization which fails to completely account for sensor degradation in the later part of the data record, thus limiting the accuracy of estimated long-term solar activity variations and the scientific value of the data. In this paper, we describe an improved Nimbus 7 SBUV spectral irradiance data set, which utilizes a more accurate model for instrument sensitivity and treats other time-dependent problems in the archived data. Estimated long-term irradiance changes during solar cycle 21 are 8.3(+/-2.6%) at 205 nm, and 4.9(+/-1.8)% at 240 nm. The revised Nimbus 7 SBUV irradiance data are in good agreement with predictions of solar cycle variations from the Mg II index proxy model. These solar irradiance changes are also consistent with overlapping irradiance data from the declining phase of solar cycle 21 measured by the Solar Mesosphere Explorer (SME). The Nimbus 7 SBUV irradiance data represent the earliest component of a 20+ year continuous record of solar spectral UV activity.

DMSP Auroral Charging at Solar Cycle 24 Maximum

NASA Technical Reports Server (NTRS)

Chandler, Michael; Parker, Linda Neergaard; Minow, Joseph I.

2013-01-01

It has been well established that polar orbiting satellites can experience mild to severe auroral charging levels (on the order of a few hundred volts to few kilovolts negative frame potentials) during solar minimum conditions (Frooninckx and Sojka, 1992; Anderson and Koons, 1996; Anderson, 2012). These same studies have shown a strong reduction in charging during the rising and declining phases of the past few solar cycles with a nearly complete suppression of auroral charging at solar maximum. Recently, we have observed examples of high level charging during the recent approach to Solar Cycle 24 solar maximum conditions not unlike those reported by Frooninckx and Sojka (1992). These observations demonstrate that spacecraft operations during solar maximum cannot be considered safe from auroral charging when solar activity is low. We present a survey of auroral charging events experienced by the Defense Meteorological Satellite Program (DMSP) F16 satellite during Solar Cycle 24 maximum conditions. We summarize the auroral energetic particle environment and the conditions necessary for charging to occur in this environment, we describe how the lower than normal solar activity levels for Solar Cycle 24 maximum conditions are conducive to charging in polar orbits, and we show examples of the more extreme charging events, sometimes exceeding 1 kV, during this time period.

THE EFFECT OF A DYNAMIC INNER HELIOSHEATH THICKNESS ON COSMIC-RAY MODULATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Manuel, R.; Ferreira, S. E. S.; Potgieter, M. S., E-mail: rexmanuel@live.com

2015-02-01

The time-dependent modulation of galactic cosmic rays in the heliosphere is studied over different polarity cycles by computing 2.5 GV proton intensities using a two-dimensional, time-dependent modulation model. By incorporating recent theoretical advances in the relevant transport parameters in the model, we showed in previous work that this approach gave realistic computed intensities over a solar cycle. New in this work is that a time dependence of the solar wind termination shock (TS) position is implemented in our model to study the effect of a dynamic inner heliosheath thickness (the region between the TS and heliopause) on the solar modulationmore » of galactic cosmic rays. The study reveals that changes in the inner heliosheath thickness, arising from a time-dependent shock position, does affect cosmic-ray intensities everywhere in the heliosphere over a solar cycle, with the smallest effect in the innermost heliosphere. A time-dependent TS position causes a phase difference between the solar activity periods and the corresponding intensity periods. The maximum intensities in response to a solar minimum activity period are found to be dependent on the time-dependent TS profile. It is found that changing the width of the inner heliosheath with time over a solar cycle can shift the time of when the maximum or minimum cosmic-ray intensities occur at various distances throughout the heliosphere, but more significantly in the outer heliosphere. The time-dependent extent of the inner heliosheath, as affected by solar activity conditions, is thus an additional time-dependent factor to be considered in the long-term modulation of cosmic rays.« less

Simplified Solar Modulation Model of Inner Trapped Belt Proton Flux As a Function of Atmospheric Density

NASA Technical Reports Server (NTRS)

Wilson, Thomas L.; Lodhi, M. A. K.; Diaz, Abel B.

2005-01-01

No simple algorithm seems to exist for calculating proton fluxes and lifetimes in the Earth's inner, trapped radiation belt throughout the solar cycle. Most models of the inner trapped belt in use depend upon AP8 which only describes the radiation environment at solar maximum and solar minimum in Cycle 20. One exception is NOAAPRO which incorporates flight data from the TIROS/NOAA polar orbiting spacecraft. The present study discloses yet another, simple formulation for approximating proton fluxes at any time in a given solar cycle, in particular between solar maximum and solar minimum. It is derived from AP8 using a regression algorithm technique from nuclear physics. From flux and its time integral fluence, one can then approximate dose rate and its time integral dose. It has already been published in this journal that the absorbed dose rate, D, in the trapped belts exhibits a power law relationship, D = A(rho)(sup -n), where A is a constant, rho is the atmospheric density, and the index n is weakly dependent upon shielding. However, that method does not work for flux and fluence. Instead, we extend this idea by showing that the power law approximation for flux J is actually bivariant in energy E as well as density rho. The resulting relation is J(E,rho)approx.(sum of)A(E(sup n))rho(sup -n), with A itself a power law in E. This provides another method for calculating approximate proton flux and lifetime at any time in the solar cycle. These in turn can be used to predict the associated dose and dose rate.

Maximum performance of solar heat engines: Discussion of thermodynamic availability and other second law considerations and their implications

NASA Astrophysics Data System (ADS)

Boehm, R. F.

1985-09-01

A review of thermodynamic principles is given in an effort to see if these concepts may indicate possibilities for improvements in solar central receiver power plants. Aspects related to rate limitations in cycles, thermodynamic availability of solar radiation, and sink temperature considerations are noted. It appears that considerably higher instantaneous plant efficiencies are possible by raising the maximum temperature and lowering the minimum temperature of the cycles. Of course, many practical engineering problems will have to be solved to realize the promised benefits.

Development of an accelerated reliability test schedule for terrestrial solar cells

NASA Technical Reports Server (NTRS)

Lathrop, J. W.; Prince, J. L.

1981-01-01

An accelerated test schedule using a minimum amount of tests and a minimum number of cells has been developed on the basis of stress test results obtained from more than 1500 cells of seven different cell types. The proposed tests, which include bias-temperature, bias-temperature-humidity, power cycle, thermal cycle, and thermal shock tests, use as little as 10 and up to 25 cells, depending on the test type.

Model for Solar Proton Risk Assessment

NASA Technical Reports Server (NTRS)

Xapos, M. A.; Stauffer, C.; Gee, G. B.; Barth, J. L.; Stassinopoulos, E. G.; McGuire, R. E.

2004-01-01

A statistical model for cumulative solar proton event fluences during space missions is presented that covers both the solar minimum and solar maximum phases of the solar cycle. It is based on data from the IMP and GOES series of satellites that is integrated together to allow the best features of each data set to be taken advantage of. This allows fluence-energy spectra to be extended out to energies of 327 MeV.

Time Exceedances for High Intensity Solar Proton Fluxes

NASA Technical Reports Server (NTRS)

Xapsos, Michael A.; Stauffer, Craig A.; Jordan, Thomas M.; Adam, James H., Jr.; Dietrich, William F.

2011-01-01

A model is presented for times during a space mission that specified solar proton flux levels are exceeded. This includes both total time and continuous time periods during missions. Results for the solar maximum and solar minimum phases of the solar cycle are presented and compared for a broad range of proton energies and shielding levels. This type of approach is more amenable to reliability analysis for spacecraft systems and instrumentation than standard statistical models.

Periods of High Intensity Solar Proton Flux

NASA Technical Reports Server (NTRS)

Xapsos, Michael A.; Stauffer, Craig A.; Jordan, Thomas M.; Adams, James H.; Dietrich, William F.

2012-01-01

Analysis is presented for times during a space mission that specified solar proton flux levels are exceeded. This includes both total time and continuous time periods during missions. Results for the solar maximum and solar minimum phases of the solar cycle are presented and compared for a broad range of proton energies and shielding levels. This type of approach is more amenable to reliability analysis for spacecraft systems and instrumentation than standard statistical models.

Modification of mesospheric OH and O3 during a measured highly relativistic electron precipitation event

NASA Technical Reports Server (NTRS)

Goldberg, R. A.; Jackman, C. H.; Backer, D. N.; Herrero, F. A.

1994-01-01

Highly relativistic electron precipitation events (HRE's) can provide a major source of energy affecting mesospheric constituents and ionization. Based on satellite data, these events are most pronounced near the minimum of the solar sunspot cycle, increasing in intensity, spectral hardness, and frequency of occurrence as the solar cycle declines. Since such events can be sustained up to several days, their integrated effect in the mesosphere can dominate over those of other energy sources such as relativistic electron precipitation events (REP's) and auroral precipitation. The energy deposition data to be discussed and analyzed were obtained by rocket at Poker Flat, Alaska, in May 1990 during a modest HRE observed at midday near the peak of the sunspot cycle. Using a NASA two dimensional model, significant enhancement of OH and depletion of O3 at 75 +/- 10 km altitude from the measured radiation are found. Estimates of enhanced effects were made for more intense HRE events, as might be expected during solar minimum. By causing O3 depletion, the electron precipitation can also regulate the penetration of solar UV radiation, which could affect the thermal properties of the mesosphere.

Planetary resonances, bi-stable oscillation modes, and solar activity cycles

NASA Technical Reports Server (NTRS)

Sleeper, H. P., Jr.

1972-01-01

The natural resonance structure of the planets in the solar system yields resonance periods of 11.08 and 180 years. The 11.08 year period is due to resonance of the sidereal periods of the three inner planets. The 180-year period is due to synodic resonances of the four major planets. These periods are also observed in the sunspot time series. The 11-year sunspot cycles from 1 to 19 are separated into categories of positive and negative cycles, Mode 1 and Mode 2 cycles, and typical and anomalous cycles. Each category has a characteristic shape, magnitude, or duration, so that statistical prediction techniques are improved when a cycle can be classified in a given category. These categories provide evidence for bistable modes of solar oscillation. The next minimum is expected in 1977 and the next maximum in 1981 or later. These epoch values are 2.5 years later than those based on typical cycle characteristics.

Radiation Risks From A Weak Field in the Coming Years

NASA Astrophysics Data System (ADS)

Rahmanifard, F.; Schwadron, N.; Smith, C. W.; Joyce, C. J.; Townsend, L.

2017-12-01

Recent solar conditions, including a prolonged solar minimum (2005-2009) and the recent small solar maximum, indicate that we are entering an era of lower solar activity than observed at other times during the space age- possibly similar to the past solar grand minima. During such periods of extremely low activity, the fluxes of galactic cosmic rays (GCRs) increase dramatically and limit the allowable days for human space missions. We use data from the Cosmic Ray Telescope for the Effects of Radiation (CRaTER) on the Lunar Reconnaissance Orbiter (LRO) to examine the correlation between the heliospheric magnetic field at 1AU and the modulation potential of the GCRs. We apply past grand solar minima conditions, including the Maunder minimum (1645-1715) and the Dalton minimum (1790-1830), to predict the modulation potential and the dose rates of the GCRs throughout the next solar cycle. The heliospheric magnetic field can drop to 4.21 (3.72) nT, leading to a modulation potential of 448.51 (235.96) MV and dose rates as high as 11.72 (16.68) cGy/yr for the case of conditions similar to the Dalton minimum (Maunder minimum). We use these results to predict the most conservative estimations of the time to 3% risk of exposure-induced death (REID) and the allowable mission durations in interplanetary space.

A solar cycle dependence of nonlinearity in magnetospheric activity

NASA Astrophysics Data System (ADS)

Johnson, Jay R.; Wing, Simon

2005-04-01

The nonlinear dependencies inherent to the historical Kp data stream (1932-2003) are examined using mutual information and cumulant-based cost as discriminating statistics. The discriminating statistics are compared with surrogate data streams that are constructed using the corrected amplitude adjustment Fourier transform (CAAFT) method and capture the linear properties of the original Kp data. Differences are regularly seen in the discriminating statistics a few years prior to solar minima, while no differences are apparent at the time of solar maxima. These results suggest that the dynamics of the magnetosphere tend to be more linear at solar maximum than at solar minimum. The strong nonlinear dependencies tend to peak on a timescale around 40-50 hours and are statistically significant up to 1 week. Because the solar wind driver variables, VBs, and dynamical pressure exhibit a much shorter decorrelation time for nonlinearities, the results seem to indicate that the nonlinearity is related to internal magnetospheric dynamics. Moreover, the timescales for the nonlinearity seem to be on the same order as that for storm/ring current relaxation. We suggest that the strong solar wind driving that occurs around solar maximum dominates the magnetospheric dynamics, suppressing the internal magnetospheric nonlinearity. On the other hand, in the descending phase of the solar cycle just prior to solar minimum, when magnetospheric activity is weaker, the dynamics exhibit a significant nonlinear internal magnetospheric response that may be related to increased solar wind speed.

Evaluation of long term solar activity effects on GPS derived TEC

NASA Astrophysics Data System (ADS)

Mansoori, Azad A.; Khan, Parvaiz A.; Ahmad, Rafi; Atulkar, Roshni; M, Aslam A.; Bhardwaj, Shivangi; Malvi, Bhupendra; Purohit, P. K.; Gwal, A. K.

2016-10-01

The solar activity hence the solar radiance follows a long term periodic variability with eleven years periodicity, known as solar cycle. This drives the long term variability of the ionosphere. In the present problem we investigate the long term behaviour of the ionosphere with the eleven year cyclic solar activity. Under the present study we characterize the ionospheric variability by Total Electron Content (TEC) using measurements made by Global Positioning System (GPS) and solar cycle variability by various solar activity indices. We make use of five solar activity indices viz. sunspot number (Rz), solar radio Flux (F10.7 cm), EUV Flux (26-34 nm), flare index and CME occurrences. The long term variability of these solar activity indices were then compared and correlated with the variability of ionospheric TEC, at a mid latitude station, Usuda (36.13N, 138.36E), of Japan, during the solar cycle 23 and ascending phase of cycle 24. From our study, we found that long term changes in the ionospheric TEC vary synchronously with corresponding changes in the solar activity indices. The correlation analysis shows that all the solar activity indices exhibit a very strong correlation with TEC (R =0.76 -0.99). Moreover the correlation between the two is stronger in the descending phase of the solar cycle. The correlation is found to be remarkably strongest during the deep minimum of the solar cycle 24 i.e. between 2007- 2009. Also we noticed a hysteresis effect exists with solar radio flux (F10.7 cm) and solar EUV flux (26-34 nm). This effect is absent with other parameters.

Observed Seasonal to Decadal-Scale Responses in Mesospheric Water Vapor

NASA Technical Reports Server (NTRS)

Remsberg, Ellis

2010-01-01

The 14-yr (1991-2005) time series of mesospheric water vapor from the Halogen Occultation Experiment (HALOE) are analyzed using multiple linear regression (MLR) techniques for their6 seasonal and longer-period terms from 45S to 45N. The distribution of annual average water vapor shows a decrease from a maximum of 6.5 ppmv at 0.2 hPa to about 3.2 ppmv at 0.01 hPa, in accord with the effects of the photolysis of water vapor due to the Lyman-flux. The distribution of the semi-annual cycle amplitudes is nearly hemispherically symmetric at the low latitudes, while that of the annual cycles show larger amplitudes in the northern hemisphere. The diagnosed 11-yr, or solar cycle, max minus min, water vapor values are of the order of several percent at 0.2 hPa to about 23% at 0.01 hPa. The solar cycle terms have larger values in the northern than in the southern hemisphere, particularly in the middle mesosphere, and the associated linear trend terms are anomalously large in the same region. Those anomalies are due, at least in part, to the fact that the amplitudes of the seasonal cycles were varying at northern mid latitudes during 1991-2005, while the corresponding seasonal terms of the MLR model do not allow for that possibility. Although the 11-yr variation in water vapor is essentially hemispherically-symmetric and anti-phased with the solar cycle flux near 0.01 hPa, the concurrent temperature variations produce slightly colder conditions at the northern high latitudes at solar minimum. It is concluded that this temperature difference is most likely the reason for the greater occurrence of polar mesospheric clouds at the northern versus the southern high latitudes at solar minimum during the HALOE time period.

Modeling the heliospheric current sheet: Solar cycle variations

NASA Astrophysics Data System (ADS)

Riley, Pete; Linker, J. A.; Mikić, Z.

2002-07-01

In this report we employ an empirically driven, three-dimensional MHD model to explore the evolution of the heliospheric current sheet (HCS) during the course of the solar cycle. We compare our results with a simpler ``constant-speed'' approach for mapping the HCS outward into the solar wind to demonstrate that dynamic effects can substantially deform the HCS in the inner heliosphere (<~5 AU). We find that these deformations are most pronounced at solar minimum and become less significant at solar maximum, when interaction regions are less effective. Although solar maximum is typically associated with transient, rather than corotating, processes, we show that even under such conditions, the HCS can maintain its structure over the course of several solar rotations. While the HCS may almost always be topologically equivalent to a ``ballerina skirt,'' we discuss an interval approaching the maximum of solar cycle 23 (Carrington rotations 1960 and 1961) when the shape would be better described as ``conch shell''-like. We use Ulysses magnetic field measurements to support the model results.

On the variation of the Nimbus 7 total solar irradiance

NASA Technical Reports Server (NTRS)

Wilson, Robert M.

1992-01-01

For the interval December 1978 to April 1991, the value of the mean total solar irradiance, as measured by the Nimbus-7 Earth Radiation Budget Experiment channel 10C, was 1,372.02 Wm(exp -2), having a standard deviation of 0.65 Wm(exp -2), a coefficient of variation (mean divided by the standard deviation) of 0.047 percent, and a normal deviate z (a measure of the randomness of the data) of -8.019 (inferring a highly significant non-random variation in the solar irradiance measurements, presumably related to the action of the solar cycle). Comparison of the 12-month moving average (also called the 13-month running mean) of solar irradiance to those of the usual descriptors of the solar cycle (i.e., sunspot number, 10.7-cm solar radio flux, and total corrected sunspot area) suggests possibly significant temporal differences. For example, solar irradiance is found to have been greatest on or before mid 1979 (leading solar maximum for cycle 21), lowest in early 1987 (lagging solar minimum for cycle 22), and was rising again through late 1990 (thus, lagging solar maximum for cycle 22), having last reported values below those that were seen in 1979 (even though cycles 21 and 22 were of comparable strength). Presuming a genuine correlation between solar irradiance and the solar cycle (in particular, sunspot number) one infers that the correlation is weak (having a coefficient of correlation r less than 0.84) and that major excursions (both as 'excesses' and 'deficits') have occurred (about every 2 to 3 years, perhaps suggesting a pulsating Sun).

Changes in photochemically significant solar UV spectral irradiance as estimated by the composite Mg II index and scale factors

NASA Technical Reports Server (NTRS)

Deland, Matthew T.; Cebula, Richard P.

1994-01-01

Quantitative assessment of the impact of solar ultraviolet irradiance variations on stratospheric ozone abundances currently requires the use of proxy indicators. The Mg II core-to-wing index has been developed as an indicator of solar UV activity between 175-400 nm that is independent of most instrument artifacts, and measures solar variability on both rotational and solar cycle time scales. Linear regression fits have been used to merge the individual Mg II index data sets from the Nimbus-7, NOAA-9, and NOAA-11 instruments onto a single reference scale. The change in 27-dayrunning average of the composite Mg II index from solar maximum to solar minimum is approximately 8 percent for solar cycle 21, and approximately 9 percent for solar cycle 22 through January 1992. Scaling factors based on the short-term variations in the Mg II index and solar irradiance data sets have been developed to estimate solar variability at mid-UV and near-UV wavelengths. Near 205 nm, where solar irradiance variations are important for stratospheric photo-chemistry and dynamics, the estimated change in irradiance during solar cycle 22 is approximately 10 percent using the composite Mg II index and scale factors.

The temperature of quiescent streamers during solar cycles 23 and 24

DOE Office of Scientific and Technical Information (OSTI.GOV)

Landi, E.; Testa, P.

2014-05-20

Recent in-situ determinations of the temporal evolution of the charge state distribution in the fast and slow solar wind have shown a general decrease in the degree of ionization of all the elements in the solar wind along solar cycles 23 and 24. Such a decrease has been interpreted as a cooling of the solar corona which occurred during the decline and minimum phase of solar cycle 23 from 2000 to 2010. In the present work, we investigate whether spectroscopic determinations of the temperature of the quiescent streamers show signatures of coronal plasma cooling during cycles 23 and 24. Wemore » measure the coronal electron density and thermal structure at the base of 60 quiescent streamers observed from 1996 to 2013 by SOHO/SUMER and Hinode/EIS and find that both quantities do now show any significant dependence on the solar cycle. We argue that if the slow solar wind is accelerated from the solar photosphere or chromosphere, the measured decrease in the in-situ wind charge state distribution might be due to an increased efficiency in the wind acceleration mechanism at low altitudes. If the slow wind originates from the corona, a combination of density and wind acceleration changes may be responsible for the in-situ results.« less

Sunspot cycle-dependent changes in the distribution of GSE latitudinal angles of IMF observed near 1 AU

NASA Astrophysics Data System (ADS)

Felix Pereira, B.; Girish, T. E.

2004-05-01

The solar cycle variations in the characteristics of the GSE latitudinal angles of the Interplanetary Magnetic Field ($\\theta$GSE) observed near 1 AU have been studied for the period 1967-2000. It is observed that the statistical parameters mean, standard deviation, skewness and kurtosis vary with sunspot cycle. The $\\theta$GSE distribution resembles the Gaussian curve during sunspot maximum and is clearly non-Gaussian during sunspot minimum. The width of the $\\theta$GSE distribution is found to increase with sunspot activity, which is likely to depend on the occurrence of solar transients. Solar cycle variations in skewness are ordered by the solar polar magnetic field changes. This can be explained in terms of the dependence of the dominant polarity of the north-south component of IMF in the GSE system near 1 AU on the IMF sector polarity and the structure of the heliospheric current sheet.

Phase space representation of neutron monitor count rate and atmospheric electric field in relation to solar activity in cycles 21 and 22.

PubMed

Silva, H G; Lopes, I

Heliospheric modulation of galactic cosmic rays links solar cycle activity with neutron monitor count rate on earth. A less direct relation holds between neutron monitor count rate and atmospheric electric field because different atmospheric processes, including fluctuations in the ionosphere, are involved. Although a full quantitative model is still lacking, this link is supported by solid statistical evidence. Thus, a connection between the solar cycle activity and atmospheric electric field is expected. To gain a deeper insight into these relations, sunspot area (NOAA, USA), neutron monitor count rate (Climax, Colorado, USA), and atmospheric electric field (Lisbon, Portugal) are presented here in a phase space representation. The period considered covers two solar cycles (21, 22) and extends from 1978 to 1990. Two solar maxima were observed in this dataset, one in 1979 and another in 1989, as well as one solar minimum in 1986. Two main observations of the present study were: (1) similar short-term topological features of the phase space representations of the three variables, (2) a long-term phase space radius synchronization between the solar cycle activity, neutron monitor count rate, and potential gradient (confirmed by absolute correlation values above ~0.8). Finally, the methodology proposed here can be used for obtaining the relations between other atmospheric parameters (e.g., solar radiation) and solar cycle activity.

Interplanetary Coronal Mass Ejections in the Near-Earth Solar Wind During 1996-2002

NASA Technical Reports Server (NTRS)

Cane, H. V.; Richardson, I. G.

2003-01-01

We summarize the occurrence of interplanetary coronal mass injections (ICMEs) in the near-Earth solar wind during 1996-2002, corresponding to the increasing and maximum phases of solar cycle 23. In particular, we give a detailed list of such events. This list, based on in-situ observations, is not confined to subsets of ICMEs, such as magnetic clouds or those preceded by halo CMEs observed by the SOHO/LASCO coronagraph, and provides an overview of 214 ICMEs in the near-Earth solar wind during this period. The ICME rate increases by about an order of magnitude from solar minimum to solar maximum (when the rate is approximately 3 ICMEs/solar rotation period). The rate also shows a temporary reduction during 1999, and another brief, deeper reduction in late 2000-early 2001, which only approximately track variations in the solar 10 cm flux. In addition, there are occasional periods of several rotations duration when the ICME rate is enhanced in association with high solar activity levels. We find an indication of a periodic variation in the ICME rate, with a prominent period of approximately 165 days similar to that previously reported in various solar phenomena. It is found that the fraction of ICMEs that are magnetic clouds has a solar cycle variation, the fraction being larger near solar minimum. For the subset of events that we could associate with a CME at the Sun, the transit speeds from the Sun to the Earth were highest after solar maximum.

Lower Ionosphere Sensitivity to Solar X-ray Flares Over a Complete Solar Cycle Evaluated From VLF Signal Measurements

NASA Astrophysics Data System (ADS)

Macotela, Edith L.; Raulin, Jean-Pierre; Manninen, Jyrki; Correia, Emília; Turunen, Tauno; Magalhães, Antonio

2017-12-01

The daytime lower ionosphere behaves as a solar X-ray flare detector, which can be monitored using very low frequency (VLF) radio waves that propagate inside the Earth-ionosphere waveguide. In this paper, we infer the lower ionosphere sensitivity variation over a complete solar cycle by using the minimum X-ray fluence (FXmin) necessary to produce a disturbance of the quiescent ionospheric conductivity. FXmin is the photon energy flux integrated over the time interval from the start of a solar X-ray flare to the beginning of the ionospheric disturbance recorded as amplitude deviation of the VLF signal. FXmin is computed for ionospheric disturbances that occurred in the time interval of December-January from 2007 to 2016 (solar cycle 24). The computation of FXmin uses the X-ray flux in the wavelength band below 0.2 nm and the amplitude of VLF signals transmitted from France (HWU), Turkey (TBB), and U.S. (NAA), which were recorded in Brazil, Finland, and Peru. The main result of this study is that the long-term variation of FXmin is correlated with the level of solar activity, having FXmin values in the range (1 - 12) × 10-7 J/m2. Our result suggests that FXmin is anticorrelated with the lower ionosphere sensitivity, confirming that the long-term variation of the ionospheric sensitivity is anticorrelated with the level of solar activity. This result is important to identify the minimum X-ray fluence that an external source of ionization must overcome in order to produce a measurable ionospheric disturbance during daytime.

Simulated solar cycle effects on the middle atmosphere: WACCM3 Versus WACCM4

NASA Astrophysics Data System (ADS)

Peck, E. D.; Randall, C. E.; Harvey, V. L.; Marsh, D. R.

2015-06-01

The Whole Atmosphere Community Climate Model version 4 (WACCM4) is used to quantify solar cycle impacts, including both irradiance and particle precipitation, on the middle atmosphere. Results are compared to previous work using WACCM version 3 (WACCM3) to estimate the sensitivity of simulated solar cycle effects to model modifications. The residual circulation in WACCM4 is stronger than in WACCM3, leading to larger solar cycle effects from energetic particle precipitation; this impacts polar stratospheric odd nitrogen and ozone, as well as polar mesospheric temperatures. The cold pole problem, which is present in both versions, is exacerbated in WACCM4, leading to more ozone loss in the Antarctic stratosphere. Relative to WACCM3, a westerly shift in the WACCM4 zonal winds in the tropical stratosphere and mesosphere, and a strengthening and poleward shift of the Antarctic polar night jet, are attributed to inclusion of the QBO and changes in the gravity wave parameterization in WACCM4. Solar cycle effects in WACCM3 and WACCM4 are qualitatively similar. However, the EPP-induced increase from solar minimum to solar maximum in polar stratospheric NOy is about twice as large in WACCM4 as in WACCM3; correspondingly, maximum increases in polar O3 loss from solar min to solar max are more than twice as large in WACCM4. This does not cause large differences in the WACCM3 versus WACCM4 solar cycle responses in temperature and wind. Overall, these results provide a framework for future studies using WACCM to analyze the impacts of the solar cycle on the middle atmosphere.

Almost Spotless

NASA Image and Video Library

2016-11-30

This week the sun was hitting its lowest level of solar activity since 2011 (Nov. 14-18, 2016) as it gradually marches toward solar minimum. This activity is usually measured by sunspot count and over the past several days the sun has been almost spotless. The sun has a pendulum-like pattern of solar cycle of activity that extends over about an 11-year period. The last peak of activity was in early 2014. At this point in time, the sunspot numbers seem to be sliding downwards faster than expected, though the solar minimum level should not occur until 2021. No doubt more and larger sunspots will inevitably appear, but we'll just have to wait and see. Movies are available at http://photojournal.jpl.nasa.gov/catalog/PIA21207

Quiet-time 0.04 - 2 MeV/nucleon Ions at 1 AU in Solar Cycles 23 and 24

NASA Astrophysics Data System (ADS)

Zeldovich, M. A.; Logachev, Y. I.; Kecskeméty, K.

2018-01-01

The fluxes of 3He, 4He, C, O, and Fe ions at low energies (about 0.04 - 2 MeV/nucleon) are studied during quiet periods in Solar Cycles (SC) 23 and 24 using data from the ULEIS/ACE instrument. In selecting quiet periods (the definition is given in Section 2.1), additional data from EPHIN/SOHO and EPAM/ACE were also used. The analysis of the ion energy spectra and their relative abundances shows that their behavior is governed by their first-ionization potential. Substantial differences in the ion energy spectra in two consecutive solar cycles are observed during the quiet periods selected. Quiet-time fluxes are divided into three distinct types according to the {˜} 80 - 320 keV/nucleon Fe/O ratio. Our results confirm the earlier observation that these types of suprathermal particles have different origins, that is, they represent different seed populations that are accelerated by different processes. Except for the solar activity minimum, the Fe/O ratio during quiet-time periods correspond either to the abundances of ions in particle fluxes accelerated in impulsive solar flares or to the mean abundances of elements in the solar corona. At the activity minimum, this ratio takes on values that are characteristic for the solar wind. These results indicate that the background fluxes of low-energy particles in the ascending, maximum, and decay phases of the solar cycle include significant contributions from both coronal particles accelerated to suprathermal energies and ions accelerated in small impulsive solar flares rich in Fe, while the contribution of remnants from earlier SEP events cannot be excluded. The comparison of suprathermal ion abundances during the first five years of SC 23 and SC 24 suggests that the quiet-time and non-quiet fluxes of Fe and 3He were lower in SC 24.

On the Relationship between Solar Wind Speed, Earthward-Directed Coronal Mass Ejections, Geomagnetic Activity, and the Sunspot Cycle Using 12-Month Moving Averages

NASA Technical Reports Server (NTRS)

Wilson, Robert M.; Hathaway, David H.

2008-01-01

For 1996 .2006 (cycle 23), 12-month moving averages of the aa geomagnetic index strongly correlate (r = 0.92) with 12-month moving averages of solar wind speed, and 12-month moving averages of the number of coronal mass ejections (CMEs) (halo and partial halo events) strongly correlate (r = 0.87) with 12-month moving averages of sunspot number. In particular, the minimum (15.8, September/October 1997) and maximum (38.0, August 2003) values of the aa geomagnetic index occur simultaneously with the minimum (376 km/s) and maximum (547 km/s) solar wind speeds, both being strongly correlated with the following recurrent component (due to high-speed streams). The large peak of aa geomagnetic activity in cycle 23, the largest on record, spans the interval late 2002 to mid 2004 and is associated with a decreased number of halo and partial halo CMEs, whereas the smaller secondary peak of early 2005 seems to be associated with a slight rebound in the number of halo and partial halo CMEs. Based on the observed aaM during the declining portion of cycle 23, RM for cycle 24 is predicted to be larger than average, being about 168+/-60 (the 90% prediction interval), whereas based on the expected aam for cycle 24 (greater than or equal to 14.6), RM for cycle 24 should measure greater than or equal to 118+/-30, yielding an overlap of about 128+/-20.

Simulating Cyclic Evolution of Coronal Magnetic Fields using a Potential Field Source Surface Model Coupled with a Dynamo Model

NASA Astrophysics Data System (ADS)

Suresh, A.; Dikpati, M.; Burkepile, J.; de Toma, G.

2013-12-01

The structure of the Sun's corona varies with solar cycle, from a near spherical symmetry at solar maximum to an axial dipole at solar minimum. Why does this pattern occur? It is widely accepted that large-scale coronal structure is governed by magnetic fields, which are most likely generated by the dynamo action in the solar interior. In order to understand the variation in coronal structure, we couple a potential field source surface model with a cyclic dynamo model. In this coupled model, the magnetic field inside the convection zone is governed by the dynamo equation and above the photosphere these dynamo-generated fields are extended from the photosphere to the corona by using a potential field source surface model. Under the assumption of axisymmetry, the large-scale poloidal fields can be written in terms of the curl of a vector potential. Since from the photosphere and above the magnetic diffusivity is essentially infinite, the evolution of the vector potential is given by Laplace's Equation, the solution of which is obtained in the form of a first order Associated Legendre Polynomial. By taking linear combinations of these polynomial terms, we find solutions that match more complex coronal structures. Choosing images of the global corona from the Mauna Loa Solar Observatory at each Carrington rotation over half a cycle (1986-1991), we compute the coefficients of the Associated Legendre Polynomials up to degree eight and compare with observation. We reproduce some previous results that at minimum the dipole term dominates, but that this term fades with the progress of the cycle and higher order multipole terms begin to dominate. We find that the amplitudes of these terms are not exactly the same in the two limbs, indicating that there is some phi dependence. Furthermore, by comparing the solar minimum corona during the past three minima (1986, 1996, and 2008), we find that, while both the 1986 and 1996 minima were dipolar, the minimum in 2008 was unusual, as there was departure from a dipole. In order to investigate the physical cause of this departure from dipole, we implement north-south asymmetry in the surface source of the magnetic fields in our model, and find that such n/s asymmetry in solar cycle could be one of the reasons for this departure. This work is partially supported by NASA's LWS grant with award number NNX08AQ34G. NCAR is sponsored by the NSF.

Cross correlation and time-lag between cosmic ray intensity and solar activity during solar cycles 21, 22 and 23

NASA Astrophysics Data System (ADS)

Sierra-Porta, D.

2018-07-01

In the present paper a systematic study is carried out to validate the similarity or co-variability between daily terrestrial cosmic-ray intensity and three parameters of the solar corona evolution, i.e., the number of sunspots and flare index observed in the solar corona and the Ap index for regular magnetic field variations caused by regular solar radiation changes. The study is made for a period including three solar cycles starting with cycle 21 (year 1976) and ending on cycle 23 (year 2008). A cross-correlation analysis was used to establish patterns and dependence of the variables. This study focused on the time lag calculation for these variables and found a maximum of negative correlation over CC1≈ 0.85, CC2≈ 0.75 and CC3≈ 0.63 with an estimation of 181, 156 and 2 days of deviation between maximum/minimum of peaks for the intensity of cosmic rays related with sunspot number, flare index and Ap index regression, respectively.

Trends and solar cycle effects in mesospheric ice clouds

NASA Astrophysics Data System (ADS)

Lübken, Franz-Josef; Berger, Uwe; Fiedler, Jens; Baumgarten, Gerd; Gerding, Michael

Lidar observations of mesospheric ice layers (noctilucent clouds, NLC) are now available since 12 years which allows to study solar cycle effects on NLC parameters such as altitudes, bright-ness, and occurrence rates. We present observations from our lidar stations in Kuehlungsborn (54N) and ALOMAR (69N). Different from general expectations the mean layer characteris-tics at ALOMAR do not show a persistent anti-correlation with solar cycle. Although a nice anti-correlation of Ly-alpha and occurrence rates is detected in the first half of the solar cycle, occurrence rates decreased with decreasing solar activity thereafter. Interestingly, in summer 2009 record high NLC parameters were detected as expected in solar minimum conditions. The morphology of NLC suggests that other processes except solar radiation may affect NLC. We have recently applied our LIMA model to study in detail the solar cycle effects on tempera-tures and water vapor concentration the middle atmosphere and its subsequent influence on mesospheric ice clouds. Furthermore, lower atmosphere effects are implicitly included because LIMA nudges to the conditions in the troposphere and lower stratosphere. We compare LIMA results regarding solar cycle effects on temperatures and ice layers with observations at ALO-MAR as well as satellite borne measurements. We will also present LIMA results regarding the latitude variation of solar cycle and trends, including a comparison of northern and southern hemisphere. We have adapted the observation conditions from SBUV (wavelength and scatter-ing angle) in LIMA for a detailed comparison with long term observations of ice clouds from satellites.

Solar induced long- and short-term variations of the cosmic ray intensity in the past, and predictions and opportunities for the future

NASA Astrophysics Data System (ADS)

McCracken, K. G.; McDonald, F. B.; Beer, J.

2009-12-01

The cosmogenic radionuclide data from the past 10,000 years, and the instrumental cosmic ray data since 1936 provide detailed information on the possible consequences of the present long and deep solar minimum. Furthermore, the cosmic ray transport equation has been used to estimate the strength of the interplanetary magnetic field (IMF) throughout the past 10,000 years. This paper presents a series of figures that document the behavior of both the cosmic radiation and the IMF at Earth in the past. In particular, the 11-year cycles in both quantities for the past 600 years are displayed; and estimates given of the cosmic ray spectrum at Earth for situations that history tells us may occur in the near future. Over the longer term, a minimum of the Hallstatt cycle (2200 yr periodicity) of solar activity occurred ~500 years ago and the Sun is now on a steadily rising plane of activity. The historic record shows that the cosmic ray intensity has decreased extremely rapidly after earlier prolonged deep minima and this suggests rapid and large changes in the heliospheric conditions that we may see replicated. The paper will also display data from the deep, isolated solar minimum of 1956 that exhibited unusual low energy cosmic ray fluxes, and a highly anomalous cosmic ray gradient in the inner heliosphere. Paleo-cosmic ray evidence will also be displayed of an episode of intense solar energetic particle (SEP) events in the interval of reduced solar activity, 1892-1900, that may possibly be repeated. If the present long, deep solar minimum is a precursor to a “Grand Minimum” such as the Dalton minimum, it will provide a much improved insight into the spectrum of the cosmic radiation in interstellar space, and to the cosmic ray modulation process in the heliosphere. With this in mind, the paper suggests key measurements, and speculates on experimental conditions that may be markedly different from those encountered in the instrumental era.

Solar Cycle Variability and Grand Minima Induced by Joy's Law Scatter

NASA Astrophysics Data System (ADS)

Karak, Bidya Binay; Miesch, Mark S.

2017-08-01

The strength of the solar cycle varies from one cycle to another in an irregular manner and the extreme example of this irregularity is the Maunder minimum when Sun produced only a few spots for several years. We explore the cause of these variabilities using a 3D Babcock--Leighton dynamo. In this model, based on the toroidal flux at the base of the convection zone, bipolar magnetic regions (BMRs) are produced with flux, tilt angle, and time of emergence all obtain from their observed distributions. The dynamo growth is limited by a tilt quenching.The randomnesses in the BMR emergences make the poloidal field unequal and eventually cause an unequal solar cycle. When observed fluctuations of BMR tilts around Joy's law, i.e., a standard deviation of 15 degrees, are considered, our model produces a variation in the solar cycle comparable to the observed solar cycle variability. Tilt scatter also causes occasional Maunder-like grand minima, although the observed scatter does not reproduce correct statistics of grand minima. However, when we double the tilt scatter, we find grand minima consistent with observations. Importantly, our dynamo model can operate even during grand minima with only a few BMRs, without requiring any additional alpha effect.

NASA Radiation Belt Models AP-8 and AE-8

DTIC Science & Technology

1989-09-30

MeV). The quiet day solar cycle variation is defined by taking the ratio of the omni-directional flux measured from solar minimum to a standard...Note 1: Model Evaluation, TREND issued at IASB , Printed at MATRA, ESTEC/Contract #8011/88/NIJMAC, 28 June 1989. "Models of the Trapped Radiation

A Mechanism For Solar Forcing of Climate: Did the Maunder Minimum Cause the Little Ice Age?

NASA Technical Reports Server (NTRS)

Yung, Yuk L.

2004-01-01

The mechanism we wish to demonstrate exploits chemical, radiative, and dynamical sensitivities in the stratosphere to affect the climate of the troposphere. The sun, while its variability in total radiative output over the course of the solar cycle is on the order of 0.1%, exhibits variability in the UV output on the order of 5%. We expect to show that a substantially decreased solar UV output lessened the heating of the Earth's stratosphere during the Maunder Minimum, through decreased radiative absorption by ozone and oxygen. These changes in stratospheric heating would lead to major changes in the stratospheric zonal wind pattern which would in turn affect the propagation characteristics of planetary-scale waves launched in the winter hemisphere. Until recently, there was no quantitative data to relate the changes in the stratosphere to those at the surface. There is now empirical evidence from the NCEP Reanalysis data that a definitive effect of the solar cycle on climate in the troposphere exists. Our recent work is summarized as follows (see complete list of publications in later part of this report).

Characteristics of low-latitude TEC during solar cycles 23 and 24 using global ionospheric maps (GIMs) over Indian sector

NASA Astrophysics Data System (ADS)

Dashora, N.; Suresh, Sunanda

2015-06-01

The characteristics of quiet time equatorial and low-latitude total electron content over the Indian sector using global ionospheric map (GIM) data (1998-2014) are obtained filtering out the solar flare and storm effects. The results are examined and interpreted in the context of large number of previous studies. The newly found features from this study are as follows. Marked difference in nature of equinoctial asymmetry is noted between solar cycles 23 and 24. Long absence of winter anomaly both during low and high solar activity (HSA) in LL (low-latitude) regions is found. Climatology of the diurnal cycle is provided in four categories using new criteria for demarcation of solar activity levels. Highest correlation (~77%) between GIM ionospheric electron content (IEC) and PI (solar EUV proxy index) is noted over equator in contrast to previous studies. The minimum positive contribution of PI in variation of IEC requires minimum of 2 years of data, and if more than 7-8 years of data are used, it saturates. Root-mean-square width of PI can be used to define the HSA. Strong QBO (quasi-biennial oscillations) in IEC is noted in tune with the one in PI over both LL locations but QBO remains surprisingly subdued over equator. The semiannual oscillations in GIM-IEC are found to be stronger at all locations during high solar activity and weaker between 2005 and 2011, whereas the annual oscillations are found to be substantially stronger only during HSA-23 and weakest over southern LL location throughout 17 years.

Time Dependence of the Electron and Positron Components of the Cosmic Radiation Measured by the PAMELA Experiment between July 2006 and December 2015.

PubMed

Adriani, O; Barbarino, G C; Bazilevskaya, G A; Bellotti, R; Boezio, M; Bogomolov, E A; Bongi, M; Bonvicini, V; Bottai, S; Bruno, A; Cafagna, F; Campana, D; Carlson, P; Casolino, M; Castellini, G; De Santis, C; Di Felice, V; Galper, A M; Karelin, A V; Koldashov, S V; Koldobskiy, S A; Krutkov, S Y; Kvashnin, A N; Leonov, A; Malakhov, V; Marcelli, L; Martucci, M; Mayorov, A G; Menn, W; Mergé, M; Mikhailov, V V; Mocchiutti, E; Monaco, A; Mori, N; Munini, R; Osteria, G; Panico, B; Papini, P; Pearce, M; Picozza, P; Ricci, M; Ricciarini, S B; Simon, M; Sparvoli, R; Spillantini, P; Stozhkov, Y I; Vacchi, A; Vannuccini, E; Vasilyev, G I; Voronov, S A; Yurkin, Y T; Zampa, G; Zampa, N; Potgieter, M S; Vos, E E

2016-06-17

Cosmic-ray electrons and positrons are a unique probe of the propagation of cosmic rays as well as of the nature and distribution of particle sources in our Galaxy. Recent measurements of these particles are challenging our basic understanding of the mechanisms of production, acceleration, and propagation of cosmic rays. Particularly striking are the differences between the low energy results collected by the space-borne PAMELA and AMS-02 experiments and older measurements pointing to sign-charge dependence of the solar modulation of cosmic-ray spectra. The PAMELA experiment has been measuring the time variation of the positron and electron intensity at Earth from July 2006 to December 2015 covering the period for the minimum of solar cycle 23 (2006-2009) until the middle of the maximum of solar cycle 24, through the polarity reversal of the heliospheric magnetic field which took place between 2013 and 2014. The positron to electron ratio measured in this time period clearly shows a sign-charge dependence of the solar modulation introduced by particle drifts. These results provide the first clear and continuous observation of how drift effects on solar modulation have unfolded with time from solar minimum to solar maximum and their dependence on the particle rigidity and the cyclic polarity of the solar magnetic field.

Nonlinear solar cycle forecasting: theory and perspectives

NASA Astrophysics Data System (ADS)

Baranovski, A. L.; Clette, F.; Nollau, V.

2008-02-01

In this paper we develop a modern approach to solar cycle forecasting, based on the mathematical theory of nonlinear dynamics. We start from the design of a static curve fitting model for the experimental yearly sunspot number series, over a time scale of 306 years, starting from year 1700 and we establish a least-squares optimal pulse shape of a solar cycle. The cycle-to-cycle evolution of the parameters of the cycle shape displays different patterns, such as a Gleissberg cycle and a strong anomaly in the cycle evolution during the Dalton minimum. In a second step, we extract a chaotic mapping for the successive values of one of the key model parameters - the rate of the exponential growth-decrease of the solar activity during the n-th cycle. We examine piece-wise linear techniques for the approximation of the derived mapping and we provide its probabilistic analysis: calculation of the invariant distribution and autocorrelation function. We find analytical relationships for the sunspot maxima and minima, as well as their occurrence times, as functions of chaotic values of the above parameter. Based on a Lyapunov spectrum analysis of the embedded mapping, we finally establish a horizon of predictability for the method, which allows us to give the most probable forecasting of the upcoming solar cycle 24, with an expected peak height of 93±21 occurring in 2011/2012.

MAGNETIC ACTIVITY CYCLES IN THE EXOPLANET HOST STAR {epsilon} ERIDANI

DOE Office of Scientific and Technical Information (OSTI.GOV)

Metcalfe, T. S.; Mathur, S.; Buccino, A. P.

2013-02-01

The active K2 dwarf {epsilon} Eri has been extensively characterized both as a young solar analog and more recently as an exoplanet host star. As one of the nearest and brightest stars in the sky, it provides an unparalleled opportunity to constrain stellar dynamo theory beyond the Sun. We confirm and document the 3-year magnetic activity cycle in {epsilon} Eri originally reported by Hatzes and coworkers, and we examine the archival data from previous observations spanning 45 years. The data show coexisting 3-year and 13-year periods leading into a broad activity minimum that resembles a Maunder minimum-like state, followed bymore » the resurgence of a coherent 3-year cycle. The nearly continuous activity record suggests the simultaneous operation of two stellar dynamos with cycle periods of 2.95 {+-} 0.03 years and 12.7 {+-} 0.3 years, which, by analogy with the solar case, suggests a revised identification of the dynamo mechanisms that are responsible for the so-called 'active' and 'inactive' sequences as proposed by Boehm-Vitense. Finally, based on the observed properties of {epsilon} Eri, we argue that the rotational history of the Sun is what makes it an outlier in the context of magnetic cycles observed in other stars (as also suggested by its Li depletion), and that a Jovian-mass companion cannot be the universal explanation for the solar peculiarities.« less

A Solar Cycle Dependence of Nonlinearity in Magnetospheric Activity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Johnson, Jay R; Wing, Simon

2005-03-08

The nonlinear dependencies inherent to the historical K(sub)p data stream (1932-2003) are examined using mutual information and cumulant based cost as discriminating statistics. The discriminating statistics are compared with surrogate data streams that are constructed using the corrected amplitude adjustment Fourier transform (CAAFT) method and capture the linear properties of the original K(sub)p data. Differences are regularly seen in the discriminating statistics a few years prior to solar minima, while no differences are apparent at the time of solar maximum. These results suggest that the dynamics of the magnetosphere tend to be more linear at solar maximum than at solarmore » minimum. The strong nonlinear dependencies tend to peak on a timescale around 40-50 hours and are statistically significant up to one week. Because the solar wind driver variables, VB(sub)s and dynamical pressure exhibit a much shorter decorrelation time for nonlinearities, the results seem to indicate that the nonlinearity is related to internal magnetospheric dynamics. Moreover, the timescales for the nonlinearity seem to be on the same order as that for storm/ring current relaxation. We suggest that the strong solar wind driving that occurs around solar maximum dominates the magnetospheric dynamics suppressing the internal magnetospheric nonlinearity. On the other hand, in the descending phase of the solar cycle just prior to solar minimum, when magnetospheric activity is weaker, the dynamics exhibit a significant nonlinear internal magnetospheric response that may be related to increased solar wind speed.« less

Sunspot activity and cosmic ray modulation at 1 a.u. for 1900-2013

NASA Astrophysics Data System (ADS)

Ahluwalia, H. S.

2014-10-01

The descent of sunspot cycle 23 to an unprecedented minimum of long duration in 2006-2009 led to a prolonged galactic cosmic ray (GCR) recovery to the highest level observed in the instrumental era for a variety of energetic charged particle species on Earth, over a wide range of rigidities. The remarkable GCR increase measured by several ground-based, balloon-borne, and detectors on a satellite is described and discussed. It is accompanied by a decrease in solar wind velocity and interplanetary magnetic field at 1 a.u., reaching the lowest values since measurements of the solar wind began in October 1963; the solar polar field strength (μT) measured at the Wilcox Solar Observatory (WSO) is also significantly reduced compared to prior cycles since the start of the program in 1976, the polar field in the northern hemisphere reversed in June 2012 and again in February 2014, that in the southern hemisphere reversed in July 2013. If updates of WSO data confirm the second reversal in northern solar hemisphere, it would pose a serious challenge to the Dynamo Theory. The long-term change in solar behavior may have begun in 1992, perhaps earlier. The physical underpinnings of these solar changes need to be understood and their effect on GCR modulation processes clarified. The study discusses the recent phenomena in the context of GCR modulation since 1900. These happenings affected our empirical predictions for the key parameters for the next two sunspot cycles (they may be progressively less active than sunspot cycle 24) but it enhanced support for our prediction that solar activity is descending into a Dalton-like grand minimum in the middle of the twentyfirst century, reducing the frequency of the coronal mass ejections; they determine the space weather affecting the quality of life on Earth, radiation dose for hardware and human activities in space as well as the frequency of large Forbush decreases at 1 a.u.

An analysis of interplanetary space radiation exposure for various solar cycles

NASA Technical Reports Server (NTRS)

Badhwar, G. D.; Cucinotta, F. A.; O'Neill, P. M.; Wilson, J. W. (Principal Investigator)

1994-01-01

The radiation dose received by crew members in interplanetary space is influenced by the stage of the solar cycle. Using the recently developed models of the galactic cosmic radiation (GCR) environment and the energy-dependent radiation transport code, we have calculated the dose at 0 and 5 cm water depth; using a computerized anatomical man (CAM) model, we have calculated the skin, eye and blood-forming organ (BFO) doses as a function of aluminum shielding for various solar minima and maxima between 1954 and 1989. These results show that the equivalent dose is within about 15% of the mean for the various solar minima (maxima). The maximum variation between solar minimum and maximum equivalent dose is about a factor of three. We have extended these calculations for the 1976-1977 solar minimum to five practical shielding geometries: Apollo Command Module, the least and most heavily shielded locations in the U.S. space shuttle mid-deck, center of the proposed Space Station Freedom cluster and sleeping compartment of the Skylab. These calculations, using the quality factor of ICRP 60, show that the average CAM BFO equivalent dose is 0.46 Sv/year. Based on an approach that takes fragmentation into account, we estimate a calculation uncertainty of 15% if the uncertainty in the quality factor is neglected.

Solar Activity Heading for a Maunder Minimum?

NASA Astrophysics Data System (ADS)

Schatten, K. H.; Tobiska, W. K.

2003-05-01

Long-range (few years to decades) solar activity prediction techniques vary greatly in their methods. They range from examining planetary orbits, to spectral analyses (e.g. Fourier, wavelet and spectral analyses), to artificial intelligence methods, to simply using general statistical techniques. Rather than concentrate on statistical/mathematical/numerical methods, we discuss a class of methods which appears to have a "physical basis." Not only does it have a physical basis, but this basis is rooted in both "basic" physics (dynamo theory), but also solar physics (Babcock dynamo theory). The class we discuss is referred to as "precursor methods," originally developed by Ohl, Brown and Williams and others, using geomagnetic observations. My colleagues and I have developed some understanding for how these methods work and have expanded the prediction methods using "solar dynamo precursor" methods, notably a "SODA" index (SOlar Dynamo Amplitude). These methods are now based upon an understanding of the Sun's dynamo processes- to explain a connection between how the Sun's fields are generated and how the Sun broadcasts its future activity levels to Earth. This has led to better monitoring of the Sun's dynamo fields and is leading to more accurate prediction techniques. Related to the Sun's polar and toroidal magnetic fields, we explain how these methods work, past predictions, the current cycle, and predictions of future of solar activity levels for the next few solar cycles. The surprising result of these long-range predictions is a rapid decline in solar activity, starting with cycle #24. If this trend continues, we may see the Sun heading towards a "Maunder" type of solar activity minimum - an extensive period of reduced levels of solar activity. For the solar physicists, who enjoy studying solar activity, we hope this isn't so, but for NASA, which must place and maintain satellites in low earth orbit (LEO), it may help with reboost problems. Space debris, and other aspects of objects in LEO will also be affected. This research is supported by the NSF and NASA.

Influence of System Operation Method on CO2 Emissions of PV/Solar Heat/Cogeneration System

NASA Astrophysics Data System (ADS)

Oke, Shinichiro; Kemmoku, Yoshishige; Takikawa, Hirofumi; Sakakibara, Tateki

A PV/solar heat/cogeneration system is assumed to be installed in a hotel. The system is operated with various operation methods: CO2 minimum operation, fees minimum operation, seasonal operation, daytime operation and heat demand following operation. Of these five operations, the former two are virtual operations that are operated with the dynamic programming method, and the latter three are actual operations. Computer simulation is implemented using hourly data of solar radiation intensity, atmospheric temperature, electric, cooling, heating and hot water supply demands for one year, and the life-cycle CO2 emission and the total cost are calculated for every operations. The calculation results show that the virtual two and the actual three operations reduce the life-cycle CO2 emission by 21% and 13% compared with the conventional system, respectively. In regard to both the CO2 emission and the cost, there is no significant difference between the virtual two operation methods or among actual three operation methods.

Solar Cycle variations in Earth's open flux content measured by the SuperDARN radar network

NASA Astrophysics Data System (ADS)

Imber, S. M.; Milan, S. E.; Lester, M.

2013-09-01

We present a long term study, from 1996 - 2012, of the latitude of the Heppner-Maynard Boundary (HMB) determined using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection and is here used as a proxy for the amount of open flux in the polar cap. The mean HMB latitude (measured at midnight) is found to be at 64 degrees during the entire period, with secondary peaks at lower latitudes during the solar maximum of 2003, and at higher latitudes during the recent extreme solar minimum of 2008-2011. We associate these large scale statistical variations in open flux content with solar cycle variations in the solar wind parameters leading to changes in the intensity of the coupling between the solar wind and the magnetosphere.

Periodicities observed on solar flux index (F10.7) during geomagnetic disturbances

NASA Astrophysics Data System (ADS)

Adhikari, B.; Narayan, C.; Chhatkuli, D. N.

2017-12-01

Solar activities change within the period of 11 years. Sometimes the greatest event occurs in the period of solar maxima and the lowest activity occurs in the period of solar minimum. During the time period of solar activity sunspots number will vary. A 10.7 cm solar flux measurement is a determination of the strength of solar radio emission. The solar flux index is more often used for the prediction and monitoring of the solar activity. This study mainly focused on the variation on solar flux index and amount of electromagnetic wave in the atmosphere. Both seasonal and yearly variation on solar F10.7 index. We also analyzed the dataset obatained from riometer.Both instruments show seasonal and yearly variations. We also observed the solar cycle dependence on solar flux index and found a strong dependence on solar activity. Results also show that solar intensities higher during the rising phase of solar cycle. We also observed periodicities on solar flux index using wavelet analysis. Through this analysis, it was found that the power intensities of solar flux index show a high spectral variability.

Natural variability of tropical upper stratospheric ozone inferred from the Atmosphere Explorer backscatter ultraviolet experiment

NASA Technical Reports Server (NTRS)

Frederick, J. E.; Abrams, R. B.; Dasgupta, R.; Guenther, B.

1981-01-01

Analysis of backscattered ultraviolet radiances observed at tropical latitudes by the Atmosphere Explorer-E satellite reveals both annual and semiannual cycles in upper stratospheric ozone. The annual variation dominates the signal at wavelengths which sense ozone primarily above 45 km while below this, to the lowest altitude sensed, 35 km, the semiannual component has comparable amplitude. Comparison of radiance measurements taken with the same instrument at solar minimum during 1976 and solar maximum in 1979 show no significant differences. This suggests that variations in upper stratospheric ozone over the solar cycle are small, although the data presently available do not allow a definite conclusion.

Peculiarities of cosmic ray modulation in the solar minimum 23/24

NASA Astrophysics Data System (ADS)

Alania, M. V.; Modzelewska, R.; Wawrzynczak, A.

2014-06-01

We study changes of the galactic cosmic ray (GCR) intensity for the ending period of the solar cycle 23 and the beginning of the solar cycle 24 using neutron monitors experimental data. We show that an increase of the GCR intensity in 2009 is generally related with decrease of the solar wind velocity U, the strength B of the interplanetary magnetic field (IMF), and the drift in negative (A < 0) polarity epoch. We present that temporal changes of rigidity dependence of the GCR intensity variation, before reaching maximum level in 2009 and after it, do not noticeably differ from each other. The rigidity spectrum of the GCR intensity variations calculated based on neutron monitors data (for rigidities > 10 GV) is hard in the minimum and near-minimum epoch. We do not recognize any nonordinary changes in the physical mechanism of modulation of the GCR intensity in the rigidity range of GCR particles to which neutron monitors respond. We compose 2-D nonstationary model of transport equation to describe variations of the GCR intensity for 1996-2012 including the A > 0 (1996-2001) and the A < 0 (2002-2012) periods; diffusion coefficient of cosmic rays for rigidity 10-15 GV is increased by 30% in 2009 (A < 0) comparing with 1996 (A > 0). We believe that the proposed model is relatively realistic, and obtained results are satisfactorily compatible with neutron monitors data.

Solar Cycle and Geomagnetic Activity Variation of Topside Ionospheric Upflow as Measured by DMSP

NASA Astrophysics Data System (ADS)

Coley, W. R.; Hairston, M. R.

2016-12-01

Under the proper conditions a considerable amount of plasma can escape the Earth's ionosphere into the magnetosphere. Indeed, there are indications that at least part of the time the ionosphere may be the dominant source of ions for the plasma sheet and near-Earth portion of the magnetosphere. The upward flux of thermal O+ from the lower part of the topside ionosphere actively provides plasma into intermediate altitudes where they may be given escape energy by various mechanisms. Previous work has indicated that there is considerable time variation of upwelling low energy ionospheric plasma to these intermediate altitudes during moderate to high solar activity. Here we use the SSIES thermal plasma instruments on board the Defense Meteorological Satellite Program (DMSP) F13-F19 series of spacecraft to examine the vertical flux of thermal O+ from the deep solar minimum of 2008-2009 to the moderately active period of 2012-2015. Separately integrating the upward and downward fluxes over the high-latitude region (auroral zone and polar cap) allows the observation of the total upflow/downflow as a function of the current geomagnetic conditions, solar cycle, and solar wind conditions. In particular we investigate the incidence of high upward flux events as a function of solar wind velocity and density during the deepest solar minimum since the space age began.

Coronal Field Opens at Lower Height During the Solar Cycles 22 and 23 Minimum Periods: IMF Comparison Suggests the Source Surface Should Be Lowered (Postprint)

DTIC Science & Technology

2012-03-01

understood simply from differences in the areas of the coronal holes , as opposed to differences in the surface fields within them. In this study, we...invoke smaller source surface radii in the potential-field source-surface (PFSS) model to construct a consistent picture of the observed coronal holes ...that the values of ≈1.9 R and ≈1.8 R for the cycles 22 and 23 minimum periods, respectively, produce the best results. The larger coronal holes

Cosmic ray modulation and radiation dose of aircrews during the solar cycle 24/25

NASA Astrophysics Data System (ADS)

Miyake, Shoko; Kataoka, Ryuho; Sato, Tatsuhiko

2017-04-01

Weak solar activity and high cosmic ray flux during the coming solar cycle are qualitatively anticipated by the recent observations that show the decline in the solar activity levels. We predict the cosmic ray modulation and resultant radiation exposure at flight altitude by using the time-dependent and three-dimensional model of the cosmic ray modulation. Our galactic cosmic ray (GCR) model is based on the variations of the solar wind speed, the strength of the heliospheric magnetic field, and the tilt angle of the heliospheric current sheet. We reproduce the 22 year variation of the cosmic ray modulation from 1980 to 2015 taking into account the gradient-curvature drift motion of GCRs. The energy spectra of GCR protons obtained by our model show good agreement with the observations by the Balloon-borne Experiment with a Superconducting magnetic rigidity Spectrometer (BESS) and the Payload for Antimatter Matter Exploration and Light-nuclei Astrophysics (PAMELA) except for a discrepancy at the solar maximum. Five-year annual radiation dose around the solar minimum at the solar cycle 24/25 will be approximately 19% higher than that in the last cycle. This is caused by the charge sign dependence of the cosmic ray modulation, such as the flattop profiles in a positive polarity.

Solar causes of strong geomagnetic disturbances during the period 1996—2013

NASA Astrophysics Data System (ADS)

Hejda, Pavel; Bochníček, Josef; Valach, Fridrich; Revallo, Miloš

2017-04-01

The purpose of this research is to assess the contribution of CMEs and CIRs to geomagnetic activity during the period 1996—2013, covering the 23rd solar cycle, the solar minimum between the 23rd and the 24th solar cycles as well as the ascending part of the current 24th solar cycle. Both CMEs and CIRs are capable of driving significant space weather effects on the Earth. Current study is not primarily aimed at construction of prediction models but can contribute to this topic by answering two principal questions: (1) what is the contribution of CME and CIR type solar events to various levels of geomagnetic disturbances and how it varies during the solar cycle (2) how does the successive emergence of CME and CIR events influence the geomagnetic response. Sometimes it can be difficult to assign the response to a particular event properly, especially in the case of several successive events. We noticed that the CIRs appeared to play important role also in years when strongly geoeffective CMEs occurred. An interesting finding, which we have revealed on this subject, concerned the year 2009; then the extremely low geomagnetic activity was probably caused by very slow solar wind from coronal holes along with the rare occurrences of CIRs.

The Slowly Varying Corona. I. Daily Differential Emission Measure Distributions Derived from EVE Spectra

NASA Astrophysics Data System (ADS)

Schonfeld, S. J.; White, S. M.; Hock-Mysliwiec, R. A.; McAteer, R. T. J.

2017-08-01

Daily differential emission measure (DEM) distributions of the solar corona are derived from spectra obtained by the Extreme-ultraviolet Variability Experiment (EVE) over a 4 yr period starting in 2010 near solar minimum and continuing through the maximum of solar cycle 24. The DEMs are calculated using six strong emission features dominated by Fe lines of charge states viii, ix, xi, xii, xiv, and xvi that sample the nonflaring coronal temperature range 0.3-5 MK. A proxy for the non-Fe xviii emission in the wavelength band around the 93.9 Å line is demonstrated. There is little variability in the cool component of the corona (T < 1.3 MK) over the 4 yr, suggesting that the quiet-Sun corona does not respond strongly to the solar cycle, whereas the hotter component (T > 2.0 MK) varies by more than an order of magnitude. A discontinuity in the behavior of coronal diagnostics in 2011 February-March, around the time of the first X-class flare of cycle 24, suggests fundamentally different behavior in the corona under solar minimum and maximum conditions. This global state transition occurs over a period of several months. The DEMs are used to estimate the thermal energy of the visible solar corona (of order 1031 erg), its radiative energy loss rate ((2.5-8) × {10}27 erg s-1), and the corresponding energy turnover timescale (about an hour). The uncertainties associated with the DEMs and these derived values are mostly due to the coronal Fe abundance and density and the CHIANTI atomic line database.

Systems efficiency and specific mass estimates for direct and indirect solar-pumped closed-cycle high-energy lasers in space

NASA Technical Reports Server (NTRS)

Monson, D. J.

1978-01-01

Based on expected advances in technology, the maximum system efficiency and minimum specific mass have been calculated for closed-cycle CO and CO2 electric-discharge lasers (EDL's) and a direct solar-pumped laser in space. The efficiency calculations take into account losses from excitation gas heating, ducting frictional and turning losses, and the compressor efficiency. The mass calculations include the power source, radiator, compressor, fluids, ducting, laser channel, optics, and heat exchanger for all of the systems; and in addition the power conditioner for the EDL's and a focusing mirror for the solar-pumped laser. The results show the major component masses in each system, show which is the lightest system, and provide the necessary criteria for solar-pumped lasers to be lighter than the EDL's. Finally, the masses are compared with results from other studies for a closed-cycle CO2 gasdynamic laser (GDL) and the proposed microwave satellite solar power station (SSPS).

Latitude Distribution of Sunspots: Analysis Using Sunspot Data and a Dynamo Model

NASA Astrophysics Data System (ADS)

Mandal, Sudip; Karak, Bidya Binay; Banerjee, Dipankar

2017-12-01

In this paper, we explore the evolution of sunspot latitude distribution and explore its relations with the cycle strength. With the progress of the solar cycle, the distributions in two hemispheres from mid-latitudes propagate toward the equator and then (before the usual solar minimum) these two distributions touch each other. By visualizing the evolution of the distributions in two hemispheres, we separate the solar cycles by excluding this hemispheric overlap. From these isolated solar cycles in two hemispheres, we generate latitude distributions for each cycle, starting from cycle 8 to cycle 23. We find that the parameters of these distributions, namely the central latitude (C), width (δ), and height (H), evolve with the cycle number, and they show some hemispheric asymmetries. Although the asymmetries in these parameters persist for a few successive cycles, they get corrected within a few cycles, and the new asymmetries appear again. In agreement with the previous study, we find that distribution parameters are correlated with the strengths of the cycles, although these correlations are significantly different in two hemispheres. The general trend features, i.e., (i) stronger cycles that begin sunspot eruptions at relatively higher latitudes, and (ii) stronger cycles that have wider bands of sunspot emergence latitudes, are confirmed when combining the data from two hemispheres. We explore these features using a flux transport dynamo model with stochastic fluctuations. We find that these features are correctly reproduced in this model. The solar cycle evolution of the distribution center is also in good agreement with observations. Possible explanations of the observed features based on this dynamo model are presented.

Observed solar near UV variability: A contribution to variations of the solar constant

NASA Technical Reports Server (NTRS)

London, Julius; Pap, Judit; Rottman, Gary J.

1989-01-01

Continuous Measurements of the Solar UV have been made by an instrument on the Solar Mesosphere Explorer (SME) since October 1981. The results for the wavelength interval 200 to 300 nm show an irradiance decrease to a minimum in early 1987 and a subsequent increase to mid-April 1989. The observed UV changes during part of solar cycles 21 to 22 represent approx. 35 percent (during the decreasing phase) and 25 percent (during the increasing phase) of the observed variations of the solar constant for the same time period as the SME measurements.

On a thermonuclear origin for the 1980-81 deep light minimum of the symbiotic nova PU Vul

NASA Technical Reports Server (NTRS)

Sion, Edward M.

1993-01-01

The puzzling 1980-81 deep light minimum of the symbiotic nova PU Vul is discussed in terms of a sequence of quasi-static evolutionary models of a hot, 0.5 solar mass white dwarf accreting H-rich matter at a rate 1 x 10 exp -8 solar mass/yr. On the basis of the morphological behavior of the models, it is suggested that the deep light minimum of PU Vul could have been the result of two successive, closely spaced, hydrogen shell flashes on an accreting white dwarf whose core thermal structure and accreted H-rich envelope was not in a long-term thermal 'cycle-averaged' steady state with the rate of accretion.

Solar Drivers of 11-yr and Long-Term Cosmic Ray Modulation

NASA Technical Reports Server (NTRS)

Cliver, E. W.; Richardson, I. G.; Ling, A. G.

2011-01-01

In the current paradigm for the modulation of galactic cosmic rays (GCRs), diffusion is taken to be the dominant process during solar maxima while drift dominates at minima. Observations during the recent solar minimum challenge the pre-eminence of drift: at such times. In 2009, the approx.2 GV GCR intensity measured by the Newark neutron monitor increased by approx.5% relative to its maximum value two cycles earlier even though the average tilt angle in 2009 was slightly larger than that in 1986 (approx.20deg vs. approx.14deg), while solar wind B was significantly lower (approx.3.9 nT vs. approx.5.4 nT). A decomposition of the solar wind into high-speed streams, slow solar wind, and coronal mass ejections (CMEs; including postshock flows) reveals that the Sun transmits its message of changing magnetic field (diffusion coefficient) to the heliosphere primarily through CMEs at solar maximum and high-speed streams at solar minimum. Long-term reconstructions of solar wind B are in general agreement for the approx. 1900-present interval and can be used to reliably estimate GCR intensity over this period. For earlier epochs, however, a recent Be-10-based reconstruction covering the past approx. 10(exp 4) years shows nine abrupt and relatively short-lived drops of B to < or approx.= 0 nT, with the first of these corresponding to the Sporer minimum. Such dips are at variance with the recent suggestion that B has a minimum or floor value of approx.2.8 nT. A floor in solar wind B implies a ceiling in the GCR intensity (a permanent modulation of the local interstellar spectrum) at a given energy/rigidity. The 30-40% increase in the intensity of 2.5 GV electrons observed by Ulysses during the recent solar minimum raises an interesting paradox that will need to be resolved.

Ionospheric Change and Solar EUV Irradiance

NASA Astrophysics Data System (ADS)

Sojka, J. J.; David, M.; Jensen, J. B.; Schunk, R. W.

2011-12-01

The ionosphere has been quantitatively monitored for the past six solar cycles. The past few years of observations are showing trends that differ from the prior cycles! Our good statistical relationships between the solar radio flux index at 10.7 cm, the solar EUV Irradiance, and the ionospheric F-layer peak density are showing indications of divergence! Present day discussion of the Sun-Earth entering a Dalton Minimum would suggest change is occurring in the Sun, as the driver, followed by the Earth, as the receptor. The dayside ionosphere is driven by the solar EUV Irradiance. But different components of this spectrum affect the ionospheric layers differently. For a first time the continuous high cadence EUV spectra from the SDO EVE instrument enable ionospheric scientists the opportunity to evaluate solar EUV variability as a driver of ionospheric variability. A definitive understanding of which spectral components are responsible for the E- and F-layers of the ionosphere will enable assessments of how over 50 years of ionospheric observations, the solar EUV Irradiance has changed. If indeed the evidence suggesting the Sun-Earth system is entering a Dalton Minimum periods is correct, then the comprehensive EVE solar EUV Irradiance data base combined with the ongoing ionospheric data bases will provide a most fortuitous fiduciary reference baseline for Sun-Earth dependencies. Using the EVE EUV Irradiances, a physics based ionospheric model (TDIM), and 50 plus years of ionospheric observation from Wallops Island (Virginia) the above Sun-Earth ionospheric relationship will be reported on.

Long-Range Solar Activity Predictions: A Reprieve from Cycle #24's Activity

NASA Technical Reports Server (NTRS)

Richon, K.; Schatten, K.

2003-01-01

We discuss the field of long-range solar activity predictions and provide an outlook into future solar activity. Orbital predictions for satellites in Low Earth Orbit (LEO) depend strongly on exospheric densities. Solar activity forecasting is important in this regard, as the solar ultra-violet (UV) and extreme ultraviolet (EUV) radiations inflate the upper atmospheric layers of the Earth, forming the exosphere in which satellites orbit. Rather than concentrate on statistical, or numerical methods, we utilize a class of techniques (precursor methods) which is founded in physical theory. The geomagnetic precursor method was originally developed by the Russian geophysicist, Ohl, using geomagnetic observations to predict future solar activity. It was later extended to solar observations, and placed within the context of physical theory, namely the workings of the Sun s Babcock dynamo. We later expanded the prediction methods with a SOlar Dynamo Amplitude (SODA) index. The SODA index is a measure of the buried solar magnetic flux, using toroidal and poloidal field components. It allows one to predict future solar activity during any phase of the solar cycle, whereas previously, one was restricted to making predictions only at solar minimum. We are encouraged that solar cycle #23's behavior fell closely along our predicted curve, peaking near 192, comparable to the Schatten, Myers and Sofia (1996) forecast of 182+/-30. Cycle #23 extends from 1996 through approximately 2006 or 2007, with cycle #24 starting thereafter. We discuss the current forecast of solar cycle #24, (2006-2016), with a predicted smoothed F10.7 radio flux of 142+/-28 (1-sigma errors). This, we believe, represents a reprieve, in terms of reduced fuel costs, etc., for new satellites to be launched or old satellites (requiring reboosting) which have been placed in LEO. By monitoring the Sun s most deeply rooted magnetic fields; long-range solar activity can be predicted. Although a degree of uncertainty in the long-range predictions remains, requiring future monitoring, we do not expect the next cycle's + 2-sigma value will rise significantly above solar cycle #23's activity level.

Solar-cycle Variations of Meridional Flows in the Solar Convection Zone Using Helioseismic Methods

NASA Astrophysics Data System (ADS)

Lin, Chia-Hsien; Chou, Dean-Yi

2018-06-01

The solar meridional flow is an axisymmetric flow in solar meridional planes, extending through the convection zone. Here we study its solar-cycle variations in the convection zone using SOHO/MDI helioseismic data from 1996 to 2010, including two solar minima and one maximum. The travel-time difference between northward and southward acoustic waves is related to the meridional flow along the wave path. Applying the ray approximation and the SOLA inversion method to the travel-time difference measured in a previous study, we obtain the meridional flow distributions in 0.67 ≤ r ≤ 0.96R ⊙ at the minimum and maximum. At the minimum, the flow has a three-layer structure: poleward in the upper convection zone, equatorward in the middle convection zone, and poleward again in the lower convection zone. The flow speed is close to zero within the error bar near the base of the convection zone. The flow distribution changes significantly from the minimum to the maximum. The change above 0.9R ⊙ shows two phenomena: first, the poleward flow speed is reduced at the maximum; second, an additional convergent flow centered at the active latitudes is generated at the maximum. These two phenomena are consistent with the surface meridional flow reported in previous studies. The change in flow extends all the way down to the base of the convection zone, and the pattern of the change below 0.9R ⊙ is more complicated. However, it is clear that the active latitudes play a role in the flow change: the changes in flow speed below and above the active latitudes have opposite signs. This suggests that magnetic fields could be responsible for the flow change.

Flow downstream of the heliospheric terminal shock: Magnetic field line topology and solar cycle imprint

NASA Technical Reports Server (NTRS)

Nerney, Steven; Suess, S. T.; Schmahl, E. J.

1995-01-01

The topology of the magnetic field in the heliosheath is illustrated using plots of the field lines. It is shown that the Archimedean spiral inside the terminal shock is rotated back in the heliosheath into nested spirals that are advected in the direction of the interstellar wind. The 22-year solar magnetic cycle is imprinted onto these field lines in the form of unipolar magnetic envelopes surrounded by volumes of strongly mixed polarity. Each envelope is defined by the changing tilt of the heliospheric current sheet, which is in turn defined by the boundary of unipolar high-latitude regions on the Sun that shrink to the pole at solar maximum and expand to the equator at solar minimum. The detailed shape of the envelopes is regulated by the solar wind velocity structure in the heliosheath.

Variability of fractal dimension of solar radio flux

NASA Astrophysics Data System (ADS)

Bhatt, Hitaishi; Sharma, Som Kumar; Trivedi, Rupal; Vats, Hari Om

2018-04-01

In the present communication, the variation of the fractal dimension of solar radio flux is reported. Solar radio flux observations on a day to day basis at 410, 1415, 2695, 4995, and 8800 MHz are used in this study. The data were recorded at Learmonth Solar Observatory, Australia from 1988 to 2009 covering an epoch of two solar activity cycles (22 yr). The fractal dimension is calculated for the listed frequencies for this period. The fractal dimension, being a measure of randomness, represents variability of solar radio flux at shorter time-scales. The contour plot of fractal dimension on a grid of years versus radio frequency suggests high correlation with solar activity. Fractal dimension increases with increasing frequency suggests randomness increases towards the inner corona. This study also shows that the low frequency is more affected by solar activity (at low frequency fractal dimension difference between solar maximum and solar minimum is 0.42) whereas, the higher frequency is less affected by solar activity (here fractal dimension difference between solar maximum and solar minimum is 0.07). A good positive correlation is found between fractal dimension averaged over all frequencies and yearly averaged sunspot number (Pearson's coefficient is 0.87).

Carrington cycle 24: the solar chromospheric emission in a historical and stellar perspective

NASA Astrophysics Data System (ADS)

Schröder, K.-P.; Mittag, M.; Schmitt, J. H. M. M.; Jack, D.; Hempelmann, A.; González-Pérez, J. N.

2017-09-01

We present the solar S-index record of cycle 24, obtained by the Telescopio Internacional de Guanajuato, Robotico Espectroscopico robotic telescope facility and its high-resolution spectrograph HEROS (R ≈ 20 000), which measures the solar chromospheric Ca II H&K line emission by using moonlight. Our calibration process uses the same set of standard stars as introduced by the Mount Wilson team, thus giving us a direct comparison with their huge body of observations taken between 1966 and 1992, as well as with other cool stars. Carrington cycle 24 activity started from the unusually deep and long minimum 2008/2009, with an S-index average of only 0.154, 0.015 deeper than the one of 1986 (〈S〉 = 0.169). In this respect, the chromospheric radiative losses differ remarkably from the variation of the coronal radio flux F10.7 cm and the sunspot numbers. In addition, the cycle 24 S-amplitude remained small, 0.022 (cycles 21 and 22 averaged: 0.024), and so resulted in a very low 2014 maximum of 〈S〉 = 0.176 (cycles 21 and 22 averaged: 0.193). We argue that this find is significant, since the Ca II H&K line emission is a good proxy for the solar far-ultraviolet (far-UV) flux, which plays an important role in the heating of the Earth's stratosphere, and we further argue that the solar far-UV flux changes with solar activity much more strongly than the total solar output.

Solar total irradiance in cycle 23

NASA Astrophysics Data System (ADS)

Krivova, N. A.; Solanki, S. K.; Schmutz, W.

2011-05-01

Context. The most recent minimum of solar activity was deeper and longer than the previous two minima as indicated by different proxies of solar activity. This is also true for the total solar irradiance (TSI) according to the PMOD composite. Aims: The apparently unusual behaviour of the TSI has been interpreted as evidence against solar surface magnetism as the main driver of the secular change in the TSI. We test claims that the evolution of the solar surface magnetic field does not reproduce the observed TSI in cycle 23. Methods: We use sensitive, 60-min averaged MDI magnetograms and quasi-simultaneous continuum images as an input to our SATIRE-S model and calculate the TSI variation over cycle 23, sampled roughly every two weeks. The computed TSI is then compared with the PMOD composite of TSI measurements and with the data from two individual instruments, SORCE/TIM and UARS/ACRIM II, that monitored the TSI during the declining phase of cycle 23 and over the previous minimum in 1996, respectively. Results: Excellent agreement is found between the trends shown by the model and almost all sets of measurements. The only exception is the early, i.e. 1996 to 1998, PMOD data. Whereas the agreement between the model and the PMOD composite over the period 1999-2009 is almost perfect, the modelled TSI shows a steeper increase between 1996 and 1999 than implied by the PMOD composite. On the other hand, the steeper trend in the model agrees remarkably well with the ACRIM II data. A closer look at the VIRGO data, which are the basis of the PMOD composite after 1996, reveals that only one of the two VIRGO instruments, the PMO6V, shows the shallower trend present in the composite, whereas the DIARAD measurements indicate a steeper trend. Conclusions: Based on these results, we conclude that (1) the sensitivity changes of the PMO6V radiometers within VIRGO during the first two years have very likely not been correctly evaluated; and that (2) the TSI variations over cycle 23 and the change in the TSI levels between the minima in 1996 and 2008 are consistent with the solar surface magnetism mechanism.

Temporal variations in the position of the heliospheric equator

NASA Astrophysics Data System (ADS)

Obridko, V. N.; Shelting, B. D.

2008-08-01

It is shown that the centroid of the heliospheric equator undergoes quasi-periodic oscillations. During the minimum of the 11-year cycle, the centroid shifts southwards (the so-called bashful-ballerina effect). The direction of the shift reverses during the solar maximum. The solar quadrupole is responsible for this effect. The shift is compared with the tilt of the heliospheric current sheet.

Novel Stimulated Electromagnetic Emission Observations with Artificial Airglow Using RF Excitation with HAARP

NASA Astrophysics Data System (ADS)

Briczinski, S. J., Jr.; Bernhardt, P. A.; Siefring, C. L.; Michell, R.; Hampton, D. L.; Watkins, B. J.; Bristow, W. A.

2014-12-01

Neutral hydrogen plays an important role in determining the state of the plasmasphere and its response to forcing from geomagnetic storms. Hydrogen's solar cycle variation is counterintuitive: there is more hydrogen at solar minimum at 300 km that there is at solar maximum. Similarly there is more hydrogen in winter than in summer and hydrogen density maximizes in the morning. In this presentation we describe these variations and consider some possible causes for them.

Solar-cycle dependence of a model turbulence spectrum using IMP and ACE observations over 38 years

NASA Astrophysics Data System (ADS)

Burger, R. A.; Nel, A. E.; Engelbrecht, N. E.

2014-12-01

Ab initio modulation models require a number of turbulence quantities as input for any reasonable diffusion tensor. While turbulence transport models describe the radial evolution of such quantities, they in turn require observations in the inner heliosphere as input values. So far we have concentrated on solar minimum conditions (e.g. Engelbrecht and Burger 2013, ApJ), but are now looking at long-term modulation which requires turbulence data over at a least a solar magnetic cycle. As a start we analyzed 1-minute resolution data for the N-component of the magnetic field, from 1974 to 2012, covering about two solar magnetic cycles (initially using IMP and then ACE data). We assume a very simple three-stage power-law frequency spectrum, calculate the integral from the highest to the lowest frequency, and fit it to variances calculated with lags from 5 minutes to 80 hours. From the fit we then obtain not only the asymptotic variance at large lags, but also the spectral index of the inertial and the energy, as well as the breakpoint between the inertial and energy range (bendover scale) and between the energy and cutoff range (cutoff scale). All values given here are preliminary. The cutoff range is a constraint imposed in order to ensure a finite energy density; the spectrum is forced to be either flat or to decrease with decreasing frequency in this range. Given that cosmic rays sample magnetic fluctuations over long periods in their transport through the heliosphere, we average the spectra over at least 27 days. We find that the variance of the N-component has a clear solar cycle dependence, with smaller values (~6 nT2) during solar minimum and larger during solar maximum periods (~17 nT2), well correlated with the magnetic field magnitude (e.g. Smith et al. 2006, ApJ). Whereas the inertial range spectral index (-1.65 ± 0.06) does not show a significant solar cycle variation, the energy range index (-1.1 ± 0.3) seems to be anti-correlated with the variance (Bieber et al. 1993, JGR); both indices show close to normal distributions. In contrast, the variance (e.g. Burlaga and Ness, 1998, JGR), and both the bendover scale (see Ruiz et al. 2014, Solar Physics) and cutoff scale appear to be log-normal distributed.

Latitude and Power Characteristics of Solar Activity at the End of the Maunder Minimum

NASA Astrophysics Data System (ADS)

Ivanov, V. G.; Miletsky, E. V.

2017-12-01

Two important sources of information about sunspots in the Maunder minimum are the Spörer catalog (Spörer, 1889) and observations of the Paris observatory (Ribes and Nesme-Ribes, 1993), which cover in total the last quarter of the 17th and the first two decades of the 18th century. These data, in particular, contain information about sunspot latitudes. As we showed in (Ivanov et al., 2011; Ivanov and Miletsky, 2016), dispersions of sunspot latitude distributions are tightly related to sunspot indices, and we can estimate the level of solar activity in the past using a method which is not based on direct calculation of sunspots and weakly affected by loss of observational data. The latitude distributions of sunspots in the time of transition from the Maunder minimum to the regular regime of solar activity proved to be wide enough. It gives evidences in favor of, first, not very low cycle no.-3 (1712-1723) with the Wolf number in maximum W = 100 ± 50, and, second, nonzero activity in the maximum of cycle no.-4 (1700-1711) W = 60 ± 45. Therefore, the latitude distributions in the end of the Maunder minimum are in better agreement with the traditional Wolf numbers and new revisited indices of activity SN and GN (Clette et al., 2014; Svalgaard and Schatten, 2016) than with the GSN (Hoyt and Schatten, 1998); the latter provide much lower level of activity in this epoch.

Implications of potential future grand solar minimum for ozone layer and climate

NASA Astrophysics Data System (ADS)

Arsenovic, Pavle; Rozanov, Eugene; Anet, Julien; Stenke, Andrea; Schmutz, Werner; Peter, Thomas

2018-03-01

Continued anthropogenic greenhouse gas (GHG) emissions are expected to cause further global warming throughout the 21st century. Understanding the role of natural forcings and their influence on global warming is thus of great interest. Here we investigate the impact of a recently proposed 21st century grand solar minimum on atmospheric chemistry and climate using the SOCOL3-MPIOM chemistry-climate model with an interactive ocean element. We examine five model simulations for the period 2000-2199, following the greenhouse gas concentration scenario RCP4.5 and a range of different solar forcings. The reference simulation is forced by perpetual repetition of solar cycle 23 until the year 2199. This reference is compared with grand solar minimum simulations, assuming a strong decline in solar activity of 3.5 and 6.5 W m-2, respectively, that last either until 2199 or recover in the 22nd century. Decreased solar activity by 6.5 W m-2 is found to yield up to a doubling of the GHG-induced stratospheric and mesospheric cooling. Under the grand solar minimum scenario, tropospheric temperatures are also projected to decrease compared to the reference. On the global scale a reduced solar forcing compensates for at most 15 % of the expected greenhouse warming at the end of the 21st and around 25 % at the end of the 22nd century. The regional effects are predicted to be significant, in particular in northern high-latitude winter. In the stratosphere, the reduction of around 15 % of incoming ultraviolet radiation leads to a decrease in ozone production by up to 8 %, which overcompensates for the anticipated ozone increase due to reduced stratospheric temperatures and an acceleration of the Brewer-Dobson circulation. This, in turn, leads to a delay in total ozone column recovery from anthropogenic halogen-induced depletion, with a global ozone recovery to the pre-ozone hole values happening only upon completion of the grand solar minimum.

Estimation of the solar Lyman alpha flux from ground based measurements of the Ca II K line

NASA Technical Reports Server (NTRS)

Rottman, G. J.; Livingston, W. C.; White, O. R.

1990-01-01

Measurements of the solar Lyman alpha and Ca II K from October 1981 to April 1989 show a strong correlation (r = 0.95) that allows estimation of the Lyman alpha flux at 1 AU from 1975 to December 1989. The estimated Lyman alpha strength of 3.9 x 10 to the 11th + or - 0.15 x 10 to the 11th photons/s sq cm on December 7, 1989 is at the same maximum levels seen in Cycle 21. Relative to other UV surrogates (sunspot number, 10.7 cm radio flux, and He I 10830 line strength), Lyman alpha estimates computed from the K line track the SME measurements well from solar maximum, through solar minimum, and into Cycle 22.

The asymmetrical features in electron density during extreme solar minimum

NASA Astrophysics Data System (ADS)

Zhang, Xuemin; Shen, Xuhui; Liu, Jing; Yao, Lu; Yuan, Guiping; Huang, Jianping

2014-12-01

The variations of plasma density in topside ionosphere during 23rd/24th solar cycle minimum attract more attentions in recently years. In this analysis, we use the data of electron density (Ne) from DEMETER (Detection of Electromagnetic Emissions Transmitted from Earthquake Regions) satellite at the altitude of 660-710 km to investigate the solstitial and equinoctial asymmetry under geomagnetic coordinate system at LT (local time) 1030 and 2230 during 2005-2010, especially in solar minimum years of 2008-2009. The results reveal that ΔNe (December-June) is always positive over Southern Hemisphere and negative over northern part whatever at LT 1030 or 2230, only at 0-10°N the winter anomaly occurs with ΔNe (December-June) > 0, and its amplitude becomes smaller with the declining of solar flux from 2005 to 2009. The ΔNe between September and March is completely negative during 2005-2008, but in 2009, it turns to be positive at latitudes of 20°S-40°N at LT 1030 and 10°S-20°N at LT 2230. Furthermore, the solstitial and equinoctial asymmetry index (AI) are calculated and studied respectively, which all depends on local time, latitude and longitude. The notable differences occur at higher latitudes in solar minimum year of 2009 with those in 2005-2008. The equinoctial AI at LT 2230 is quite consistent with the variational trend of solar flux with the lowest absolute AI occurring in 2009, the extreme solar minimum, but the solstitial AI exhibits abnormal enhancement during 2008 and 2009 with bigger AI than those in 2005-2007. Compared with the neutral compositions at 500 km altitude, it illustrates that [O/N2] and [O] play some roles in daytime and nighttime asymmetry of Ne at topside ionosphere.

Structure and sources of solar wind in the growing phase of 24th solar cycle

NASA Astrophysics Data System (ADS)

Slemzin, Vladimir; Goryaev, Farid; Shugay, Julia; Rodkin, Denis; Veselovsky, Igor

2015-04-01

We present analysis of the solar wind (SW) structure and its association with coronal sources during the minimum and rising phase of 24th solar cycle (2009-2011). The coronal sources prominent in this period - coronal holes, small areas of open magnetic fields near active regions and transient sources associated with small-scale solar activity have been investigated using EUV solar images and soft X-ray fluxes obtained by the CORONAS-Photon/TESIS/Sphinx, PROBA2/SWAP, Hinode/EIS and AIA/SDO instruments as well as the magnetograms obtained by HMI/SDO. It was found that at solar minimum (2009) velocity and magnetic field strength of high speed wind (HSW) and transient SW from small-scale flares did not differ significantly from those of the background slow speed wind (SSW). The major difference between parameters of different SW components was seen in the ion composition represented by the C6/C5, O7/O6, Fe/O ratios and the mean charge of Fe ions. With growing solar activity, the speed of HSW increased due to transformation of its sources - small-size low-latitude coronal holes into equatorial extensions of large polar holes. At that period, the ion composition of transient SW changed from low-temperature to high-temperature values, which was caused by variation of the source conditions and change of the recombination/ionization rates during passage of the plasma flow through the low corona. However, we conclude that criteria of separation of the SW components based on the ion ratios established earlier by Zhao&Fisk (2009) for higher solar activity are not applicable to the extremely weak beginning of 24th cycle. The research leading to these results has received funding from the European Commission's Seventh Framework Programme (FP7/2007-2013) under the grant agreement eHeroes (project n° 284461, www.eheroes.eu).

Forecast for solar cycle 23 activity: a progress report

NASA Astrophysics Data System (ADS)

Ahluwalia, H. S.

2001-08-01

At the 25th International Cosmic Ray Conference (ICRC) at Durban, South Africa, I announced the discovery of a three cycle quasi-periodicity in the ion chamber data string assembled by me, for the 1937 to 1994 period (Conf. Pap., v. 2, p. 109, 1997). It corresponded in time with a similar quasi-periodicity observed in the dataset for the planetary index Ap. At the 26th ICRC at Salt Lake City, UT, I reported on our analysis of the Ap data to forecast the amplitude of solar cycle 23 activity (Conf. Pap., v. 2, pl. 260, 1999). I predicted that cycle 23 will be moderate (a la cycle 17), notwithstanding the early exuberant forecasts of some solar astronomers that cycle 23, "may be one of the greatest cycles in recent times, if not the greatest." Sunspot number data up to April 2001 indicate that our forecast appears to be right on the mark. We review the solar, interplanetary and geophysical data and describe the important lessons learned from this experience. 1. Introduction Ohl (1971) was the first to realize that Sun may be sending us a subliminal message as to its intent for its activity (Sunspot Numbers, SSN) in the next cycle. He posited that the message was embedded in the geomagnetic activity (given by sum Kp). Schatten at al (1978) suggested that Ohl hypothesis could be understood on the basis of the model proposed by Babcock (1961) who suggested that the high latitude solar poloidal fields, near a minimum, emerge as the toroidal fields on opposite sides of the solar equator. This is known as the Solar Dynamo Model. One can speculate that the precursor poloidal solar field is entrained in the high speed solar wind streams (HSSWS) from the coronal holes which are observed at Earth's orbit during the descending phase of the previous cycle. The interaction

Interpretation of 3He variations in the solar wind

NASA Technical Reports Server (NTRS)

Coplan, M. A.; Ogilvie, K. W.; Geiss, J.; Bochsler, P.

1983-01-01

The ion composition instrument (ICI) on ISEE-3 observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km/s. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of 3He flares occurred during this time.

Interpretation of He-3 abundance variations in the solar wind

NASA Technical Reports Server (NTRS)

Coplan, M. A.; Ogilvie, K. W.; Bochsler, P.; Geiss, J.

1984-01-01

The ion composition instrument (ICI) on ISEE-3 observed the isotopes of helium of mass 3 and 4 in the solar wind almost continuously between August 1978 and July 1982. This period included the increase towards the maximum of solar activity cycle 21, the maximum period, and the beginning of the descent towards solar minimum. Observations were made when the solar wind speed was between 300 and 620 km/s. For part of the period evidence for regular interplanetary magnetic sector structure was clear and a number of He-3 flares occurred during this time.

Structure of the Photospheric Magnetic Field During Sector Crossings of the Heliospheric Magnetic Field

NASA Astrophysics Data System (ADS)

Getachew, Tibebu; Virtanen, Ilpo; Mursula, Kalevi

2017-11-01

The photospheric magnetic field is the source of the coronal and heliospheric magnetic fields (HMF), but their mutual correspondence is non-trivial and depends on the phase of the solar cycle. The photospheric field during the HMF sector crossings observed at 1 AU has been found to contain enhanced field intensities and definite polarity ordering, forming regions called Hale boundaries. Here we separately study the structure of the photospheric field during the HMF sector crossings during Solar Cycles 21 - 24 for the four phases of each solar cycle. We use a refined version of Svalgaard's list of major HMF sector crossings, mapped to the Sun using the solar wind speed observed at Earth, and the daily level-3 magnetograms of the photospheric field measured at the Wilcox Solar Observatory in 1976 - 2016. We find that the structure of the photospheric field corresponding to the HMF sector crossings and the existence and properties of the corresponding Hale bipolar regions varies significantly with solar cycle, solar cycle phase, and hemisphere. The Hale boundaries in more than half of the ascending, maximum, and declining phases are clear and statistically significant. The clearest Hale boundaries are found during the (+,-) HMF crossings in the northern hemisphere of odd Cycles 21 and 23, but less systematical during the (+,-) crossings in the southern hemisphere of even Cycles 22 and 24. No similar difference between odd and even cycles is found for the (-,+) crossings. This shows that the northern hemisphere has a more organized Hale pattern overall. The photospheric field distribution also depicts a larger area for the field of the northern hemisphere during the declining and minimum phases, in a good agreement with the bashful ballerina phenomenon.

SuperDARN observations of an unusually contracted ionospheric convection pattern during the recent deep solar minimum

NASA Astrophysics Data System (ADS)

Imber, S. M.; Milan, S. E.; Lester, M.

2012-04-01

We present a long term study, from 1995 - 2011, of the latitude of the Heppner-Maynard Boundary (HMB) determined using the northern hemisphere SuperDARN radars. The HMB represents the equatorward extent of ionospheric convection. We find that the average latitude of the HMB at midnight is 61° magnetic latitude during the solar maximum of 2003, but it moves significantly poleward during solar minimum, averaging 64° latitude during 1996, and 68° during 2010. This poleward motion is observed despite the increasing number of low latitude radars built in recent years as part of the StormDARN network, and so is not an artefact of data coverage. We believe that the recent extreme solar minimum lead to an average HMB location that was further poleward than previous solar cycles. We also calculated the open-closed field line boundary (OCB) from auroral images during the years 2000-2002 and find that on average the HMB is located equatorward of the OCB by ~6°. We suggest that the HMB may be a useful proxy for the OCB when global auroral images are not available.

Critical frequencies of the ionospheric F1 and F2 layers during the last four solar cycles: Sunspot group type dependencies

NASA Astrophysics Data System (ADS)

Yiǧit, Erdal; Kilcik, Ali; Elias, Ana Georgina; Dönmez, Burçin; Ozguc, Atila; Yurchshyn, Vasyl; Rozelot, Jean-Pierre

2018-06-01

The long term solar activity dependencies of ionospheric F1 and F2 regions' critical frequencies (f0F1 and f0F2) are analyzed for the last four solar cycles (1976-2015). We show that the ionospheric F1 and F2 regions have different solar activity dependencies in terms of the sunspot group (SG) numbers: F1 region critical frequency (f0F1) peaks at the same time with the small SG numbers, while the f0F2 reaches its maximum at the same time with the large SG numbers, especially during the solar cycle 23. The observed differences in the sensitivity of ionospheric critical frequencies to sunspot group (SG) numbers provide a new insight into the solar activity effects on the ionosphere and space weather. While the F1 layer is influenced by the slow solar wind, which is largely associated with small SGs, the ionospheric F2 layer is more sensitive to Coronal Mass Ejections (CMEs) and fast solar winds, which are mainly produced by large SGs and coronal holes. The SG numbers maximize during of peak of the solar cycle and the number of coronal holes peaks during the sunspot declining phase. During solar minimum there are relatively less large SGs, hence reduced CME and flare activity. These results provide a new perspective for assessing how the different regions of the ionosphere respond to space weather effects.

Solar activity as driver for the Dark Age Grand Solar Minimum

NASA Astrophysics Data System (ADS)

Neuhäuser, Ralph; Neuhäuser, Dagmar

2017-04-01

We will discuss the role of solar activity for the temperature variability from AD 550 to 840, roughly the last three centuries of the Dark Ages. This time range includes the so-called Dark Age Grand Solar Minimum, whose deep part is dated to about AD 650 to 700, which is seen in increased radiocarbon, but decreased aurora observations (and a lack of naked-eye sunspot sightings). We present historical reports on aurorae from all human cultures with written reports including East Asia, Near East (Arabia), and Europe. To classify such reports correctly, clear criteria are needed, which are also discussed. We compare our catalog of historical aurorae (and sunspots) as well as C-14 data, i.e. solar activity proxies, with temperature reconstructions (PAGES). After increased solar activity until around AD 600, we see a dearth of aurorae and increased radiocarbon production in particular in the second half of the 7th century, i.e. a typical Grand Solar Minimum. Then, after about AD 690 (the maximum in radiocarbon, the end of the Dark Age Grand Minimum), we see increased auroral activity, decreasing radiocarbon, and increasing temperature until about AD 775. At around AD 775, we see the well-known strong C-14 variability (solar activity drop), then immediately another dearth of aurorae plus high C-14, indicating another solar activity minimum. This is consistent with a temperature depression from about AD 775 on into the beginning of the 9th century. Very high solar activity is then seen in the first four decades with four aurora clusters and three simultaneous sunspot clusters, and low C-14, again also increasing temperature. The period of increasing solar activity marks the end of the so-called Dark Ages: While auroral activity increases since about AD 793, temperature starts to increase quite exactly at AD 800. We can reconstruct the Schwabe cycles with aurorae and C-14 data. In summary, we can see a clear correspondence of the variability of solar activity proxies and surface temperature reconstructions. This indicates that solar activity is an important climate driver.

Salient Features of the New Sunspot Number Time Series

NASA Astrophysics Data System (ADS)

Ahluwalia, H. S.; Ygbuhay, R. C.

2016-12-01

Recently Clette et al. (Space Sci. Rev. 186, 35, 2014) completed the first revision of the international sunspot number SSN(V2) since its creation by Wolf in 1849 SSN(V1) starting in 1700 and ending in May 2015. The yearly values of SSN(V2) are larger than those of SSN(V1) but the secular trend in their timelines both exhibit a gradual descent after Cycle 21 minimum resulting in greatly reduced activity for Cycle 24. It has two peaks; one in 2012 due to activity in the north hemisphere (NH) and the other in 2014 due to excess activity in the south hemisphere (SH). The N-S excess of hemispheric SSNs is examined for 1950 - 2014, in relation to the time variations of the solar polar field for 1976 - 2015, covering five complete solar cycles (19 - 23) and parts of the bordering two (18, 24). We find that SH tends to become progressively more active in the declining phase of the cycles reaching an extreme value that gave rise to a second higher peak in October 2014 in the smoothed SSNs accompanied by a strong solar polar field in SH. There may be a Gleissberg cyclicity in the asymmetric solar dynamo operation. The continuing descent of the secular trend in SSNs implies that we may be near a Dalton-level grand minimum. The low activity spell may last well past 2060, accompanied by a stable but reduced level of the space weather/climate. Fourier spectrum of the time domain of SSNs shows no evidence of the 208 year/cycle (ypc) (DeVries/Suess cycle) seen in the cosmogenic radionuclide ({}^{10}Be) concentration in the polar ice cores and {}^{14}C record in trees indicating that 208 ypc peak may be of non-solar origin. It may arise from the climate process(es) that change(s) the way radionuclides are deposited on polar ice. It should be noted that we only have {˜} 400 years of SSN data, so it is possible that DeVries/Suess cycle is really driven by the Sun but for now we do not have any evidence of that; there is no known physical process linking 208 ypc to solar dynamo operation.

Modeling the heliolatitudinal gradient of the solar wind parameters with exact MHD solutions

NASA Technical Reports Server (NTRS)

Lima, J. J. G.; Tsinganos, K.

1995-01-01

The heliolatitudinal dependence of observations of the solar wind macroscopic quantities such as the averaged proton speed, density and the mass and momentum flux are modeled. The published observations covering the last two and a half solar cycles, are obtained either via the technique of interplanetary scintillations for the last 2 solar cycles (1970-1990), or, from the plasma experiment aboard the ULYSSES spacecraft for the recent period 1990-1994. Exact, two dimensional solutions of the full set of the steady MHD equations are used which are obtained through a nonlinear separation of the variables in the MHD equations. The three parameters emerging from the solutions are fixed from these observations, as well as from observations of the solar rotation. It is found that near solar maximum the solar wind speed is uniformly low, around the 400 km/s over a wide range of latitudes. On the other hand, during solar minimum and the declining phase of the solar activity cycle, there is a strong heliolatitudinal gradient in proton speed between 400-800 from equator to pole. This modeling also agrees with previous findings that the gradient in wind speed with the latitude is offset by a gradient in density such that the mass and momentum flux vary relatively little.

Influence of solar variability on the infrared radiative cooling of the thermosphere from 2002 to 2014.

PubMed

Mlynczak, Martin G; Hunt, Linda A; Mertens, Christopher J; Thomas Marshall, B; Russell, James M; Woods, Thomas; Earl Thompson, R; Gordley, Larry L

2014-04-16

Infrared radiative cooling of the thermosphere by carbon dioxide (CO 2 , 15 µm) and by nitric oxide (NO, 5.3 µm) has been observed for 12 years by the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument on the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics satellite. For the first time we present a record of the two most important thermospheric infrared cooling agents over a complete solar cycle. SABER has documented dramatic variability in the radiative cooling on time scales ranging from days to the 11 year solar cycle. Deep minima in global mean vertical profiles of radiative cooling are observed in 2008-2009. Current solar maximum conditions, evidenced in the rates of radiative cooling, are substantially weaker than prior maximum conditions in 2002-2003. The observed changes in thermospheric cooling correlate well with changes in solar ultraviolet irradiance and geomagnetic activity during the prior maximum conditions. NO and CO 2 combine to emit 7 × 10 18 more Joules annually at solar maximum than at solar minimum. First record of thermospheric IR cooling rates over a complete solar cycleIR cooling in current solar maximum conditions much weaker than prior maximumVariability in thermospheric IR cooling observed on scale of days to 11 years.

Coronal and heliospheric magnetic flux circulation and its relation to open solar flux evolution

NASA Astrophysics Data System (ADS)

Lockwood, Mike; Owens, Mathew J.; Imber, Suzanne M.; James, Matthew K.; Bunce, Emma J.; Yeoman, Timothy K.

2017-06-01

Solar cycle 24 is notable for three features that can be found in previous cycles but which have been unusually prominent: (1) sunspot activity was considerably greater in the northern/southern hemisphere during the rising/declining phase; (2) accumulation of open solar flux (OSF) during the rising phase was modest, but rapid in the early declining phase; (3) the heliospheric current sheet (HCS) tilt showed large fluctuations. We show that these features had a major influence on the progression of the cycle. All flux emergence causes a rise then a fall in OSF, but only OSF with foot points in opposing hemispheres progresses the solar cycle via the evolution of the polar fields. Emergence in one hemisphere, or symmetric emergence without some form of foot point exchange across the heliographic equator, causes poleward migrating fields of both polarities in one or both (respectively) hemispheres which temporarily enhance OSF but do not advance the polar field cycle. The heliospheric field observed near Mercury and Earth reflects the asymmetries in emergence. Using magnetograms, we find evidence that the poleward magnetic flux transport (of both polarities) is modulated by the HCS tilt, revealing an effect on OSF loss rate. The declining phase rise in OSF was caused by strong emergence in the southern hemisphere with an anomalously low HCS tilt. This implies the recent fall in the southern polar field will be sustained and that the peak OSF has limited implications for the polar field at the next sunspot minimum and hence for the amplitude of cycle 25.