Solar Activity

We study possible interrelations between the 300-year record of the yearly sunspot numbers and the solar inertial motion (SIM) using the recently developed technique of synchronization analysis. Phase synchronization of the sunspot cycle and the SIM is found and statistically confirmed in three epochs (1734-1790, 1855-1875 and 1907-1960) of the whole period 1700-2000. These results give quantitative support to the hypothesis that there is a weak interaction between the solar activity and the SIM.

Context. The Solar Dynamics Observatory (SDO) was launched in February 2010 and is now providing an unprecedented view of the solar activity at high spatial resolution and high cadence covering a broad range of temperature layers of the atmosphere. Aims. We aim at defining the structure of a polar crown cavity and describing its evolution during the erupting process. Methods. We use high cadence time series of SDO/AIA observations at 304Å (50000 K) and 171Å (0.6 MK) to determine the structure of the polar crown cavity and its associated plasma as well as the evolution of the cavity during the different phases of the eruption. Results. We observe coronal plasma shaped by magnetic field lines with a negative curvature (U-shape) sitting at the bottom of a cavity. The cavity is located just above the polar crown filament material. We thus observe the inner part of the cavity above the filament as depicted in the classical three part Coronal Mass Ejection (CME) model composed of a filament, a cavity and a CME front. The filament (in this case a polar crown filament) is part of the cavity and makes a continuous structuring from the filament to the CME front depicted by concentric ellipses (in a 2D cartoon). Conclusions. We propose to define a polar crown cavity as a density depletion sitting above denser polar crown filament plasma drained down the cavity due to gravity. As part of the polar crown filament, plasma at different temperatures (ranging from 50000K to 0.6 MK) is observed at the same location on the cavity dips and sustained by a competition between the gravity and the curvature of magnetic field lines. The eruption of the polar crown cavity as a solid body can be decomposed into two phases: a slow rise at a speed of 0.6 km•s −1 , and an acceleration phase at a mean speed of 25 km•s −1 .

V. A. KUDRYAVTSEV, V. A. KUZNETSOV, AND O. G. RYAZHKAYA Institute.for Nuclear Research of the Academy of Sciences of the USSR, Moscow We study the self-arline properties of intensity fluctuations of underground muons generated by primary cosmic rays of rigidity > 1600 GV. The muon time series were recorded at a vertical depth of 570 Hg/cm 2 during the years 1981-1983. This time interval includes a period of intense solar activity in the summer of 1982 which was characterized by the creation of large solar wind shocks and associated production of major interplanetary disturbances. The purpose of our analysis is to obtain from the behavior of the muon intensity some insight into the large-scale behavior of interplanetary magnetic field fluctuations and their effects on the propagation of high-rigidity galactic cosmic rays. The results give good evidence for fractal behavior of large-scale muon fluctuations in the range from a few hours to more than 10 days, w,•th the scaling exponent H varying according to the time interval analyzed. We find that the large time scale muon fluctuations evolve from a preshock condition in late 1981 to early 1982 characterized by a scaling exponent H = 0.28 and power spectrum f-x.6 to a condition with H = 0.07 and anj '-•'• power spectrum during the most intense solar activity in 1982, followed by a slow return in 1983 to the original preshock conditions (H = 0.14, f-•.3).

Unexplained periodic fluctuations in the decay rates of 32 Si and 226 Ra have been reported by groups at Brookhaven National Laboratory ( 32 Si), and at the Physikalisch-Technische-Bundesandstalt in Germany ( 226 Ra). We show from an analysis of the raw data in these experiments that the observed fluctuations are strongly correlated in time, not only with each other, but also with the distance between the Earth and the Sun. Some implications of these results are also discussed, including the suggestion that discrepancies in published half-life determinations for these and other nuclides may be attributable in part to differences in solar activity during the course of the various experiments, or to seasonal variations in fundamental constants.

The first satellite observations of the total field-aligned component of the quasi-dc Poynting flux are presented for two passes over the polar region, one in the noon sector and one in the afternoon. The energy input due to electron precipitation is also presented. In the noon pass the downward Poynting flux in the auroral oval was comparable to the kinetic energy input rate. The peak electromagnetic energy input rate of 6 ergs/(cm 2 s) equaled the peak particle input while the integrated electromagnetic value along the trajectory was 60% that of the particles. In the afternoon pass the peak electromagnetic energy input was also about 6 ergs/(cm 2 s), but the peak particle energy was 6 times this value. The average electromagnetic input was 10% of the particle input for the pass. In this study we can measure the Poynting flux only over a limited range of scale sizes; thus the contribution to the total energy budget in the polar cap cannot be determined. Both passes show small regions characterized by upward Poyntiag flux suggesting a neutral wind dynamo. There is also evidence during part of the noontime pass that the external generator acted in opposition to an existing wind field since the Poynting flux was greater than the estimate of Joule heating from the electric field measurement alone (i.e., from •pE2). In the course of deriving Poynting's theorem for the geophysical case we also present a proof that ground magnetometer systems respond primarily to the Hall current which does not depend upon geometric cancellation between the field generated by Pedersen and field-aligned currents.

The ICE experiment onboard DEMETER micro-satellite provides, since July 2004, continuous and regular observations of electromagnetic emissions in the frequency range from 20 Hz to 20 kHz. We analyse the behaviour of the natural and also the artificial signals before and after the earthquake, to find some optionally association to seismic events. We consider three transmitter signals emitted at 16.58 kHz, 17.8 kHz and 19.8 kHz by stations in Europe (Germany, DFY), in Asia (Japan, JP) and in Australia (Australia, NWC), respectively. We select specific large earthquakes, with a magnitude more than 5.5, which occurred close to the transmitter areas. We discuss particularly the variation of the VLF natural and transmitter signals and the dependence, or not, on the geomagnetic and solar activities.

Ion drift meter observations from the Atmosphere Explorer E satellite during the period of January 1977 to December 1979 are used to study the dependence of equatorial (dip latitudes < 7.5 ø) F region vertical plasma drifts (east-west electric fields) on solar activity, season, and longitude. The satellite-observed ion drifts show large day-to-day and seasonal variations. Solar cycle effects are most pronounced near the dusk sector with a large increase of the prereversal velocity enhancement from solar minimum to maximum. The diurnal, seasonal, and solar cycle dependence of the longitudinally averaged drifts are consistent with results from the Jicamarca radar except near the June solstice when the AE-E nighttime downward velocities are significantly smaller than those observed by the radar. Pronounced presunrise downward drift enhancements are often observed over a large longitudinal range but not in the Peruvian equatorial region. The satellite data indicate that longitudinal variations are largest near the June solstice, particularly near dawn and dusk but are virtually absent during equinox. The longitudinal dependence of the AE-E vertical drifts is consistent with results from ionosonde data. These measurements were also used to develop a description of equatorial F region vertical drifts in four longitudinal sectors.

The past few hundred years have seen large fluctuations in atmospheric 14 C concentration. In part, these have been the result of natural factors, including the climatic changes of the Little Ice Age, and the Spö rer and Maunder solar activity minima. In addition, however, changes in human activity since the middle of the 19th century have released 14 C-free CO 2 to the atmosphere. Moreover, between c. 1955 and c. 1963, atmospheric nuclear weapon testing resulted in a dramatic increase in the concentration of 14 C in the atmosphere. This was followed by a significant decrease in atmospheric 14 C as restrictions on nuclear weapon testing began to take effect and as rapid exchange occurred between the atmosphere and other carbon reservoirs. The large fluctuations in atmospheric 14 C that occurred prior to 1955 mean that a single radiocarbon date may yield an imprecise calibrated age consisting of several possible age ranges. This difficulty may be overcome by obtaining a series of 14 C dates from a sequence and either wigglematching these dates to a radiocarbon calibration curve or using additional information on dated materials and their surrounding environment to narrow the calibrated age ranges associated with each 14 C date. For the period since 1955 (the bomb-pulse period), significant differences in atmospheric 14 C levels between consecutive years offer the possibility of dating recent samples with a resolution of from one to a few years. These approaches to dating the recent past are illustrated using examples from peats, lake and salt marsh sediments, tree rings, marine organisms and speleothems.

The sandhopper Talitrus saltator has an endogenous activity rhythm with a circadian periodicity. It is well known for its ability to compensate for the apparent movement of the sun during its migrations along the sea-land axis of the beach. Both chronometric mechanisms are entrained by the natural LD photoperiod. Using actographic recordings and tests of solar orientation of individuals kept under an LD 12:12 clock-shifted cycle, after 1-13 days of treatment, we demonstrate that the timing mechanism of activity rhythm and the chronometric mechanism underlying the sun compass are the same.

We identify solar cycle signals in 155 years of global sea level pressure (SLP) and sea surface temperature (SST) data using a multiple linear regression approach. In SLP we find in the North Pacific a statistically significant weakening of the Aleutian Low and a northward shift of the Hawaiian High in response to higher solar activity, confirming the results of previous authors. We also find a weak but broad reduction in pressure across the equatorial Pacific. In SST we identify a weak El Niño-like pattern in the tropics, unlike the strong La Niña-like signal found recently by some other authors. We show that the latter have been influenced by the technique of compositing data from peak years of the sunspot cycle as these years have often coincided with the negative phase of the ENSO cycle. Furthermore, the date of peak annual sunspot number generally falls a year or more in advance of the broader maximum of the 11-year solar cycle so that analyses which incorporate data from all years represent more coherently the difference between periods of high and low solar activity on these timescales.

We present a continuous record of the Asian monsoon over the last 16 ka from y 18 O measurements of stalagmite calcite. Over 900 oxygen isotopic measurements providing information on shifts in monsoon precipitation are combined with a chronology from 45 precise 230 Th dates. y 18 O and therefore Asian monsoon intensity generally follows changes in insolation, although changes in y 18 O are generally accommodated in abrupt shifts in contrast to smoothly varying insolation, indicating that threshold effects may be important. y 18 O decreased dramatically (~3x) at the start of the Holocene (~11.5 ka) and remained low for~6 ka. Four positive y 18 O events centered at 11225F97 yr BP (1.05x), 10880F117 yr BP (1.15x), 9165F75 yr BP (1.4x), and a double event centered at 8260F64 yr BP (1.1x) and 8080F74 yr BP (1.0x) punctuated this period of high monsoon intensity. All four events correlate within error with climate changes in Greenland ice cores. Thus, the relationship between the Asian monsoon and the North Atlantic observed during the glacial period appears to continue into the early Holocene. In addition, three of the four events correlate within error with outburst events from Lake Agassiz. The decline of monsoon intensity in the mid-late Holocene is characterized by an abrupt positive shift in y 18 O which occurs at 3550F59 yr BP (1.1x in~100 yr). In addition, the Holocene is punctuated by numerous centennial-and multi-decadal-scale events (amplitudes 0.5 to 1x) up to half the amplitude of the glacial interstadial events seen in the last glacial period. Thus, Holocene centennialand multi-decadal-scale monsoon variability is significant, although not as large as glacial millennial-scale variability. The monsoon shows a strong connection with northern South American hydrological changes related by changes in ITCZ position. Spectral analysis of the y 18 O record shows significant peaks at solar periodicities of 208 yr and 86 yr suggesting variation is influenced by solar forcing. However, there are numerous other significant peaks including peaks at El Niño frequencies (observed for high-resolution portions of the record between 8110 and 8250 yr) which suggest that changes in oceanic and atmospheric circulation patterns in addition to those forced by solar changes are important in controlling Holocene monsoon Earth and Planetary Science Letters 233 www.elsevier.com/locate/epsl climate. In addition, for this high-resolution portion, we observe a distinctive biennial oscillation of the Asian monsoon, which has been associated with the Tropospheric Biennial Oscillation (TBO).

Page 1. 1484 IEEE TRANSACTIONS ON NUCLEAR SCIENCE, VOL. 40, NO. 6, DECEMBER 1993 Altitude and Latitude Variations in Avionics SEU and Atmospheric Neutron Flux E. Normand and T. J. Baker Boeing Defense &amp;amp; Space Group, Seattle, WA 98124-2499 Abstract ...

In south-central Siberia archaeological evidence suggests an acceleration of cultural development and an increase in the density of nomadic populations around 850 BC. We hypothesize a relationship with an abrupt climatic shift towards increased humidity caused by a decline of solar activity. Areas that initially may have been hostile semi-deserts changed into attractive steppe landscapes with a high biomass production and high carrying capacity. Newly available steppe areas could be invaded by herbivores, making them attractive for nomadic tribes. The central Asian horse-riding Scythian culture expanded, and an increased population density was a stimulus for westward migration towards southeastern Europe.

The relation between solar activities and the geomagnetic field induced currents (GIC) have been well studied in the auroral region and it usually occurs most frequently at high latitudes. However, during major geomagnetic storms, the auroral zone can extend substantially towards lower latitudes. Disturbance caused by solar activities can disrupt power grids and also increase the corrosion rate of buried natural gas pipelines. GIC are driven by the geomagnetic field induced by a geomagnetic disturbance. In this paper, we investigated the correlation between solar activities using the interplanetary magnetic field (IMF) and geomagnetic disturbance storm time (DST) index data with the telluric currents (also referred to as geomagnetic induced currents GIC) level through the disturbance pattern of geomagnetic field. The research areas are from Lunas in Kedah to Perlis. The pattern of geomagnetic field disturbance had been identified and analyzed to investigate the harmful effect of geomagnetic storms towards the performance of complex power grid in Malaysia.

The physics of solar forcing of the climate and long term climate change is summarized, and the role of energetic charged particles (including cosmic rays) on cloud formation and their effect on climate is examined. It is considered that the cosmic raycloud cover hypothesis is not supported by presently available data and further investigations (during Forbush decreases and at other times) should be analyzed to further examine the hypothesis. Another player in climate is lightning through the production of NO x ; this greenhouse gas, water vapour in the troposphere (and stratosphere) and carbon dioxide influence the global temperature through different processes. The enhancement of aerosol concentrations and their distribution in the troposphere also affect the climate and may result in enhanced lightning activity. Finally, the roles of atmospheric conductivity on the electrical activity of thunderstorms and lightning discharges in relation to climate are discussed.

The new Climate Timeline and Correlating Periods of Human and Earth History chart is revised, more detailed and improved.
These view of Earth's history over the last 20 million years addresses various interdisciplinary aspects of Earth's history and their interactivity, along with the emergence and development of human and human-like species. The new graph focuses on high-precision dating, so far possible, regarding the overall timing of the events.

The Sun is the nearest stellar and astrophysical laboratory, available for detailed studies in several fields of physics and astronomy. It is a sphere of hot gas with a complex and highly variable magnetic field which plays a very important role. The Sun shows an unprecedented wealth of phenomena that can be studied extensively and to the greatest detail, in a way we will never be in a position to study in other stars. Humans have studied the Sun for millennia and after the discovery of the telescope they realized that the Sun varies with time, i.e., solar activity is highly variable, in tune scales of millennia to seconds. The study of these variabilities helps us to understand how the Sun works and how it affects the interplanetary medium, Earth and the other planets. Solar power varies substantially and greatly affects the Earth and humans. Solar activity has several important periodicities, and quasi-periodicities. Knowledge of these periodicities helps us to forecast, to an extent, solar events that affect our planet. The most prominent periodicity of solar activity is the one of 11 years. The actual period is in fact 22 years because the magnetic field polarity of the Sun has to be taken into account. The Sun can be considered as a non-linear RLC electric circuit with a period of 22 years. The RLC equivalent circuit of the Sun is a van der Pol oscillator and such a model can explain many solar phenomena, including the variability of solar energy with time. Other quasi-periodicities such as the ones of 154 days, the 1.3, 1.7 to 2 years, etc., some of which might be harmonics of the 22 year cycle are also present in solar activity, and their study is very interesting and important since they affect the Earth and human activities. The period of 27 days related to solar rotation plays also a very important role in geophysical phenomena. It is noticeable that almost all periodicities are highly variable with time as wavelet analysis reveals. It is very important for humans to be in a position to forecast solar activity during the next hour, day, year, decade and century, because solar phenomena affect life on Earth and such predictions will help politicians and policy makers to better serve their countries and our planet. (X. Moussas). z Deceased. 1 We can assume astronomers are the only humans that their life is affected by the stars since they make their living with them, although people believing in astrology are also affected by the stars. www.elsevier.com/locate/asr Advances in Space Research 35 (2005) 725-738

Ionospheric total electron content (TEC) of the equatorial ionization anomaly (EIA) is studied by analyzing dual-frequency signals of the Global Position System (GPS) acquired from a network of receivers around the Asian-Australian region during 1996-2004. The latitude, occurrence time, strength of the most developed EIA crest, and crest-to-trough ratio (CTR) for both the noon and post-sunset sector obtained from a daily TEC contour map have been used to study the solar cycle variations of EIA in the Asian-Australian region. The results reveal that semiannual and seasonal variations were the dominant factor that controls the morphology of the EIA structure which can be identified in the past studies (e.g. Wu et al., 2008). It is also found that the latitude and local time position of the anomaly crest show a hemispheric asymmetry because (a) The northern crest of EIA is expanded during the equinox indicating a weak semiannual variation while the southern crest is inhibited during June-August presenting a strong seasonal variation, and (b) The local time of the northern crest appears ~1.3 h earlier than that of the southern crest in June while showing no difference at December. Solar activity dependence is more evident in the EIA crest region than in the EIA trough region and least in the post-sunset sector at equinox. A seasonal linear relationship is derived between the post-sunset CTR and solar flux, which should be caused by the solar-dependant equatorial E×B vertical drift.

"Tempus Solaris: Some concepts on solar activity, secular variations of atmospheric Carbon–14,  and the Carbon Isotope Stages

"Absolute dating by the Radiocarbon method has been a fundamental tool for archaeologist worldwide since mid-twentieth century. But, even today Radiocarbon calibration has received little attention, because there is no full understanding on the implications of existence of cyclic abnormalities in calibration curves for chronology building at regional or continental level. A critical class of such anomalies is the De Vries Effect, or Suess ‘wiggles’, which refer to secular or middle range variations in the 14C record. Account of such anomaly, far from limiting the utility of Radiocarbon method, constitute a useful tool for chronology building at macro-regional level, taking as a reference natural and global scale events instead of local cultural phenomena, sometimes difficult to correlate between them because their characteristics are so particular. The advantage of the issued chronology is it’s foundation on secular atmospheric variations that renew the bond between solar variability and Earth’s climate, rescuing its eventual impact in the cultural development.""

This paper gives a brief overview over the International Reference Ionosphere (IRI) project and model. IRI is recognized as the official standard for the ionosphere by the International Standardization Organization (ISO), the International Union of Radio Science (URSI), the Committee on Space Research (COSPAR), and the European Cooperation for Space Standardization (ECCS). Of great importance are the external drivers of the model that help IRI to represent ionospheric conditions as realistically as possible. The paper discusses the drivers currently used presents recent improvements and changes. Besides the standard solar, magnetic, and ionospheric indices the paper also reports on the adjustment of the model with data and equivalent indices and on the progress towards a Real-Time IRI using data assimilation. IRI has been widely validated with many different data sources and has fared very well in community wide assessment studies. We present some of these studies and document the wide usages of the model in the scientific literature. Finally, we present an outlook on things to come in IRI-2018 and thereafter.

The development of regional ionospheric Total Electron Content (TEC) models has contributed to understanding the behavior of ionospheric parameters and the coupling of the ionosphere to space weather activities on both local and global scales. In the past several decades, the International Global Navigation Satellite Systems Service (GNSS) networks of dual frequency receiver data have been applied to develop global and regional models of ionospheric TEC. These models were mainly developed in the Northern Hemisphere where there are dense network of ground based GPS receivers for regional data coverage. Such efforts have been historically rare over the African region, and have only recently begun. This thesis reports the investigation of the effect of mid-latitude magnetic storms on TEC over South Africa for portions of Solar Cycles 23 and 24. The MAGIC package was used to estimate TEC over South Africa during Post Solar Maximum, Solar Minimum, and Post Solar Minimum periods. It is found that TEC is largely determined by the diurnal cycle of solar forcing and subsequent relaxation, but effects due to storms can be determined.

The Sun's magnetic field and differential rotation give rise to much complexity in its structure and activity over a large range in both spatial and temporal scales. The most notable among these is the solar activity cycle of 11 years, or magnetic cycle of 22 years. On shorter time scales of a few seconds to several hours, spectacular explosive events occur in the solar atmosphere, such as, solar flares, prominence eruptions, and coronal mass ejections (CMEs). The explosive energy release takes place in the form of accelerated particles, bulk mass motion, and enhancement of radiation over the entire electromagnetic spectrum ranging from γ-rays to radio wavelengths. These solar transients are essentially the source of disturbance in the interplanetary medium, and also cause geomagnetic effects upon their encounter with the Earth. We present an account of the recent developments in our understanding of these phenomena using both space-borne, and ground-based observations.

Whether the solar activity was very low, and especially whether the solar cycle existed, during the Maunder Minimum (1645 1715 AD), have been disputed for a long time. In this paper we use the Guliya NO 3 data, which can reflect the solar activity, to analyze the characteristics of the solar activity during the Maunder Minimum. The results show that the solar activity was indeed low, and solar cycle displayed normal as present, i.e. about 11a, in that period. Moreover, it was found that the solar activity contains a 36-year periodic component probably, which might be related to the variations in the length of the sunspot cycle. This finding is of importance for the study of the relationship between the sun variability and the Earth climate change.

The cosmogenic nuclide beryllium-10 (10Be), recovered from ice cores, is often used to study solar activity on long time-
scales. However, the 10Be signal is also influenced by factors other than the Sun. To identify and quantify various contributions to the 10Be signal, two Antarctic snow records from the Vostok and Concordia sites spanning the last 60 years were studied at a sub-annual resolution. Three factors that contribute to the 10Be signal were identified. First, a significant period of approximately 11 yr that can be associated with the modulation of 10Be production by solar activity was detected in both records. The solar imprint constitutes 20–35% of the variance within the total signal. The 11-yr 10Be snow component was attenuated by a factor of ~0.5 and was delayed by ~1.4 yr compared to the10Be production expected within the polar atmosphere. The result could be interpreted as the composite response of a stratospheric 10Be reservoir with an 11-yr modulation that was attenuated and delayed (with respect to 10Be polar production) and to a tropospheric 10Be reservoir with an 11-yr modulation that was not attenuated or delayed. Then, peaks in 10Be concentrations that were ~66% and ~35% higher than the average concentration were observed during the stratospheric volcanic eruptions of Agung (in 1963) and Pinatubo (in 1991), respectively. In light of these new results, published 10Be ice core records could be reinterpreted because spikes in 10Be concentration appear at the time of several stratospheric events. The data indicate that stratospheric volcanic eruptions can impact 10Be transport and deposition as a result of the roles played by the sedimentation of sulfate aerosols and the formation and rapid settling of polar
stratospheric clouds (PSC). Also, an interannual variability of ~4 yr was determined in both 10Be records, corresponding to
~26% of the variance within the signal at Vostok. As with species of marine origin (sodium), this 4-yr variability is interpreted
as a tropospheric modulation. The 4-yr variability could be associated with atmospheric circulation associated with the coupled Southern Ocean ocean–atmosphere system. The results presented here, from sites within the high Antarctic plateau, open new possibilities for ice core dating over the last few centuries and for the reconstruction of past solar activity in relation to climate.

This research was performed to characterize the variability of weather behavior in the lower and upper atmosphere layers, particularly its dependence on conditions in the troposphere and ionosphere at six different stations over UKM Bangi, Selangor. The measurements are based on short-term monitoring of precipitable water vapour (PWV) in the troposphere and total electron content (TEC) in the ionosphere using

Radiation measurements made onboard the MIR Orbital Station have spanned nearly a decade and covered two solar cycles, including one of the largest solar particle events, one of the largest magnetic storms, and a mean solar radio ux level reaching 250 × 10 4 Jansky that has been observed in the last 40 years. The cosmonaut absorbed dose rates varied from about 450 Gy day −1 during solar minimum to approximately half this value during the last solar maximum. There is a factor of about two in dose rate within a given module, and a similar variation from module to module. The average radiation quality factor during solar minimum, using the ICRP-26 deÿnition, was about 2.4. The drift of the South Atlantic Anomaly was measured to be 6:0 ± 0:5 • W, and 1:6 ± 0:5 • N. These measurements are of direct applicability to the International Space Station. This paper represents a comprehensive review of Mir Space Station radiation data available from a variety of sources.

The total odd nitrogen (NOy) budget in the stratosphere and lower mesosphere has been determined using the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) measurements of NO, NO2, N2O5, HNO3, ClONO2, and HNO4. ACE-FTS has been measuring these six major NOy species from orbit since February 2004 using infrared solar occultation. A global NOy climatology of monthly mean volume mixing

Time series analysis of the leaf biometry and rhizome production of the endemic Mediterranean seagrass Posidonia oceanica (L.) Delile was performed for a meadow in the Ligurian Sea (NW Mediterranean) in order to assess changes in plant growth during a massive flowering event that occurred in 2003 and coincided with the warmest summer temperatures recorded in the last centuries. P. oceanica exhibited the highest values of leaf surface area during the flowering year and the highest values of rhizome production in the previous year. The years immediately following the flowering event were characterized by a decrease in both parameters. Comparison of the years of massive flowering events reported in the literature for the entire Mediterranean with the historical series (spanning the last 50 years) of air temperature and sunspot number suggests that intense solar activity, and not warmer temperature per se, is likely to be the main trigger of massive Posidonia oceanica flowering events.

The knowledge of the scale height in the topside ionosphere region remains rather poor due to the insufficient observations carried so far. To advance this knowledge, presented here is a new method of retrieving the topside ionospheric scale height based on radio occultation observations onboard low-earth-orbiting satellites. The scale height, well known for its dependence on the temperatures and masses of the ionospheric constituents, understandably experiences large spatial and temporal variability. With the help of the CHAMP satellite's occultation experiment, analysed is the scale height behaviour with respect to solar and geomagnetic activity, local time, season, longitude and latitude. The expected strong dependence on temperature has been confirmed; however, it has been found that this dependence is not straightforward but more complex and clearly affected by other factors. For example, while the daytime scale height values increase at higher solar activity, the night-time values do not show such a trend. The seasonal dependence proved to be strong with summer-time values significantly higher than winter-time numbers. Also, there is no common pattern for the diurnal variations: sometimes daytime values are higher, sometimes the night-time values dominate; large differences are detected from season to season and from latitude to latitude. Generally, the scale increases at higher latitudes, although a few differences do exist. No major longitudinal and hemispheric differences have been detected so far. Based on the accumulated data, a first attempt has been made to empirically simulate the scale height value at 425 km altitude; as input parameters, the model respects the local time, latitude, and season. The scale height model can be implemented into the electron density profile retrieval procedure by delivering an improved initial guess. r

The climate of Labrador is uniquely influenced by Labrador Sea atmosphere-ocean dynamics and related sea surface temperature, sea ice and atmospheric fluctuations in the northwest Atlantic. Here we describe composite ring width and maximum latewood density white spruce records averaged over five (four for density) treeline sites in northern Labrador, spanning the past four centuries. These records correlate significantly with surface air and sea surface temperature records for the northwest Atlantic as well as with the North Atlantic Oscillation (NAO). Temperatures over Labrador appear to have been influenced by climate processes operating on interannual to multidecadal time scales over the length of the tree-ring record. The ring width composite reveals a significant (>99% level) mode of variation centered at around 40-60 years which appears to be robust over the full length of record and may correspond to multidecadal modes identified in model and instrumental studies of North Atlantic climate. The density composite indicates significant peaks at about 21-24, 9 and 2-3 years, which generally correspond to spectral modes identified for the NAO. This density series also shows a significant (>99% level) mode of variation at 3.6 years, which is statistically coherent with the winter (DJF) Southern Oscillation Index. This mode decreases in amplitude in the 1800s period of the Little Ice Age, one of the lowest growth periods in the Labrador tree-ring series as well as other northern temperature proxies. This period was also a time of diminished solar activity and several major volcanic events, including the eruption of Tambora in 1815. The ensuing summer of 1816 was the coldest over the past four centuries as inferred from the Labrador density composite. Hardships suffered by Labrador Inuit resulting from the extreme cold period of 1816-17 are mentioned in Moravian mission records. Archaeological and ethnohistorical data also document shifts in the subsistence practices and settlement patterns of Labrador Inuit throughout the 1800s. Many of the cultural changes have been attributed to the effects of European settlement of the region, but may also be a response to the severe climatic conditions during this time.

Space exploration programmes, currently under discussion in the US and in Europe, foresee human missions to Mars to happen within the first half of this century. In this context, the European Space Agency (ESA) has conducted a study on the human responses, limits and needs for such exploratory missions, the so-called HUMEX study (ESA SP-1264). Based on a critical assessment of the limiting factors for human health and performance and the definition of the life science and life support requirements performed in the frame of the HUMEX study, the following major critical items have been identified: (i) radiation health risks, mainly occurring during the interplanetary transfer phases and severely augmented in case of an eruption of a solar particle event;

Key drivers of solar weather and mid-term solar weather are reviewed by considering a selection of relevant physics-and statistics-based scientific models as well as a M. Messerotti ( ) INAF-Astronomical Observatory of Trieste, space weather applications. The characteristics and outcomes of the considered scientific and prediction models indicate that they only partially cope with the complex nature of solar activity for the lack of a detailed knowledge of the underlying physics. This is indicated by the fact that, on one hand, scientific models based on chaos theory and non-linear dynamics reproduce better the observed features, and, on the other hand, that prediction models based on statistics and artificial neural networks perform better. To date, the solar weather prediction success at most time and spatial scales is far from being satisfactory, but the forthcoming ground-and space-based high-resolution observations can add fundamental tiles to the modelling and predicting frameworks as well as the application of advanced mathematical approaches in the analysis of diachronic solar observations, that are a must to provide comprehensive and homogeneous data sets.