Scientific objectives of the Solar Mesosphere Explorer mission

The 1981–82 Solar Mesosphere Explorer (SME) mission is described. The SME experiment will provide a comprehensive study of mesospheric ozone and the processes which form and destroy it. Five instruments will be carried on the spinning spacecraft to measure the ozone density and its altitude distribution from 30 to 80 km, monitor the incoming solar ultraviolet radiation, and measure other atmospheric constituent which affect ozone. The polar-orbiting spacecraft will be placed into a 3pm-3 am Sun-synchronous orbit. The atmospheric measurements will scan the Earth's limb and measure: (1) the mesospheric and stratospheric ozone density distribution by inversion of Rayleigh-scattered ultraviolet limb radiance, and the thermal emission from ozone at 9.6 m; (2) the water vapor density distribution by inversion of thermal emission at 6.3 m; (3) the ozone photolysis rate by inversion of the O₂(¹g) 1.27 m limb radiance; (4) the temperature profile by a combination of narrow-band and wide-band measurements of the 15 m thermal emission by CO₂; and, (5) theNO₂ density distribution by inversion of Rayleighscattered limb radiance at 0.439 m. The solar ultraviolet monitor will measure both the 0.2–0.31 m spectral region and the Lyman-alpha (0.1216 m) contribution to the solar irradiance. This combination of measurements will provide a rigorous test of the photochemical equilibrium theory of the mesospheric oxygen-hydrogen system, will determine what changes occur in the ozone distribution as a result of changes in the incoming solar radiation, and will detect changes that may occur as a result of meteorological disturbances.     

Solar Forcing of Climate

Solar activity is evident both in the equatorial activity centres and in the polar magnetic field variations. The total solar irradiance variation is due to the former component. During the extraordinarily long minimum of activity between sunspot cycles 23 and 24, the variations related to the equatorial field components reached their minimum values in the first half of 2008, while those related to the polar field variations had their extreme values rather at the end of 2009 and the first half of 2010. The explanation of this delay is another challenge for dynamo theories. The role of the open solar flux has so far been grossly underestimated in discussions of Sun-climate relations. The gradual increase in the average terrestrial ground temperature since 1610 is related both to the equatorial and polar field variations. The main component (0.077?K/century) is due to the variation of the total solar irradiance. The second component (0.040?K/century) waits for an explanation. The smoothed residual increase, presumably antropogenic, obtained after subtraction of the known components from the total increase was 0.31?K in 1999.     

Anomalous Heating of the Solar Atmosphere in the Epoch of the Solar Activity Minimum

Geomagnetism and Aeronomy - The article studies the physical mechanism of the generation of a steady stream of weak shock waves at the photospheric level during the epoch of the solar-activity...     

Nickel isotope heterogeneity in the early Solar System

We report small but significant variations in the ⁵⁸Ni/⁶¹Ni-normalised ⁶⁰Ni/⁶¹Ni and ⁶²Ni/⁶¹Ni ratios (expressed as ε⁶⁰Ni and ε⁶²Ni) of bulk iron and chondritic meteorites. Carbonaceous chondrites have variable, positive ε⁶²Ni (0.05 to 0.25), whereas ordinary chondrites have negative ε⁶²Ni (− 0.04 to − 0.09). The Ni isotope compositions of iron meteorites overlap with those of chondrites, and define an array with negative slope in the ε⁶⁰Ni versus ε⁶²Ni diagram. The Ni isotope compositions of the volatile-depleted Group IVB irons are similar to those of the refractory CO, CV carbonaceous chondrites, whereas the other common magmatic iron groups have Ni isotope compositions similar to ordinary chondrites. Only enstatite chondrites have identical Ni isotope compositions to Earth and so appear to represent the most appropriate terrestrial building material. Differences in ε⁶²Ni reflect distinct nucleosynthetic components in precursor solids that have been variably mixed, but some of the ε⁶⁰Ni variability could reflect a radiogenic component from the decay of ⁶⁰Fe. Comparison of the ε⁶⁰Ni of iron and chondritic meteorites with the same ε⁶²Ni allows us to place upper limits on the ⁶⁰Fe/⁵⁶Fe of planetesimals during core segregation. We estimate that carbonaceous chondrites had initial ⁶⁰Fe/⁵⁶Fe < 1 × 10^− 7. Our data place less good constraints on initial ⁶⁰Fe/⁵⁶Fe ratios of ordinary chondrites but our results are not incompatible with values as high as 3 × 10^− 7 as determined by in-situ measurements. We suggest that the Ni isotope variations and apparently heterogeneous initial ⁶⁰Fe/⁵⁶Fe results from physical sorting within the protosolar nebula of different phases (silicate, metal and sulphide) that carry different isotopic signatures.     

Solar activity variations and climatic changes

Summary For the last two millenia it has been possible to determine the secular variation of solar activity from naked-eye sunspots, aurorae and radiocarbon variations. The results of the analysis of old East Asian observations of comets, which reflect the night cloudiness variation, do not agree with the former findings that the long-term climatic changes derived from comets depend on solar activity. The distinct anticorrelation between the Chinese records of comets and naked-eye sunspots is found only for the period from the 3rd to 6th century A.D., but in other centuries any correlation can hardly be seen. East Asian cometary observations give evidence of climatic changes in different parts of this large geographic region.Secular variations of the River Nile levels, regularly measured from the 7th to 15th century A.D., clearly correlate with the solar variations, which suggests evidence for solar influence on the climatic changes in the East African tropics. The decline of the Kingdoms in ancient Egypt and the occurrence of the Intermediate Periods are generally explained by very low Nile floods and prolonged droughts followed by severe famines and the destruction of the political structure. But the radiocarbon data show that at least the First and Second Intermediate Periods coincide with the secular maxima of solar activity and the Middle Kingdom with the minimum. This contradicts the positive correlation found from the eight centuries of measurements of River Nile levels made by Arabs. It seems that the influence of solar activity on the secular climatic changes has an episodic character.

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Solar response in the temperature over the equatorial middle atmosphere

One of the longest temperature records available for the equatorial region is provided by Rocketsonde from Thumba (8°N, 77°E), India during the period 1971–1993. In recent times, these data sets are reanalyzed using the up-to-date regression models, which take care of several corrections and parameters, not accounted for in earlier analyses and hence affecting the conclusions. In this paper, annual mean solar response in this data set along with the seasonal solar coefficient is quantitatively estimated now with improved confidence. A negative solar response in the stratosphere (1–2 K/100 solar flux unit, sfu) and a positive response for the mesosphere (0.5–3 K/100 sfu) are found. The negative stratospheric solar response is in contrast to the solar coefficient reported for low latitudes by earlier workers for other stations.     

Interaction of Solar-Flare-Accelerated Nuclei with the Solar Photosphere and the Isotopic Composition of the Solar Wind

The nuclear interactions of solar-flare-accelerated protons and ions with the solar atmosphere and the deeper layers of the Sun lead to the formation of several stable and radioactive isotopes. This article examines the GEANT4 depth profiles of ²H, ³H, ³He, ⁶Li, ⁷Li, ¹⁰Be, and ¹⁴C. When accelerated particles pass through a layer of 0.1–2 g cm^–2, ⁶Li, ⁷Li, ¹⁰Be, and ¹⁴C isotopes form in sufficient amounts to explain their anomalous abundances in lunar soil samples. It is assumed that they escape into interplanetary space with coronal mass ejections immediately after the flare.     

Solar magnetic field distribution and geomagnetic activity

Summary Regularities in the solar background magnetic field distribution are described and some of their specific patterns and their structures are studied. The influence of the solar differential rotation on the behaviour of Magnetic Active Longitudes is demonstrated. The origin of some specific details different in both polarities is discussed. The relation of this longitudinal solar magnetic field distribution to the longitudinal distribution of the daily geomagnetic character figures C9 is investigated. Some correlational characteristics are given. The specific Index of Geomagnetic Recurrence is estimated and the changes of its values in time are demonstrated.

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Solar activity effects in the ionospheric D region

Variations in the D-region electron concentration within the solar activity cycle are considered. It is demonstrated that conclusions of various authors, who have analyzed various sets of experimental data on [e], differ significantly. The most reliable seem to be the conclusions based on analysis of the [e] measurements carried out by the Faraday rotation method and on the theoretical concepts on the D-region photochemistry. Possible QBO effects in the relation of [e] to solar activity are considered and an assumption is made that such effects may be the reason for the aforementioned disagreement in conclusions on the [e] relation to solar indices.Paper Presented at the Second IAGA/ICMA (IAMAS) Workshop on Solar Activity Forcing of the Middle Atmosphere, Prague, August 1997     

Solar UV radiation and its absorption in the mesosphere and stratosphere

Solar radiation of >175 nm and of Lyman-alpha at 121.6 nm is absorbed in the mesosphere and stratosphere by molecular oxygen (<242 nm) and also by ozone molecules at >200 nm. This paper describes the photodissociation processes resulting from absorption in the Schumann-Runge bands and Herzberg continuum of molecular oxygen and also in the Hartley, Huggins and Chappuis bands of ozone. Special consideration is given to differences between the stratospheric and mesospheric problems.     

Solar wind induced processes in the magnetotail

Solar wind/IMF parameters and their variations influence the state and dynamics of the magnetosphere in several different ways, and the plasma sheet plays its own active role to form the magnetotail’s rssponse to external driving. This field is still quite conrtoversial; key unsolved issues are those which probably involve the nonsteady, nonequilibrium and nonlinear character of the system. This paper discusses an interesting development of concepts concerning (1) plasma sheet convection, (2) mechanisms which initiate the substorm onset, and (3) variability of tail dynamics. A remarkable example is a recognition of Bursty Bulk Flows as a basic way for the plasma sheet to sustain the convective transport of plasma, energy and magnetic flux via transient mesoscale dynamic structures. As concerns the substorm onset, the sharp change from the magnetic reconnection (NEL) model to processes in the dipolar-like near tail is now moving into a synthetic stage. Hear non-linear models of different coupled instabilities are actively explored to find a way to excite the tearing mode starting from a singular thin current sheet configuration which seems to form in the near tail prior to breakup. Variable responses to external drivers and the variability of substorms compel a recognition of the magnetotail as a very complicated nonlinear open system which includes a heirarchy of coupled process of different scales. A unique fleet of magnetospheric spacecraft, simultaneously probing different domains and supported by extensive ground observations, global imaging and solar wind monitoring, noe provides a real chance to understand the magnetotail as a global dynamic system.     

Solar infrared spectral observations around the 1999 solar eclipse

An experiment was performed at the Roseland Community Observatory, Cornwall, during the 11 August 1999 total solar eclipse. The main objective was to search for strong infrared coronal lines with a view to identifying candidates for subsequent coronal magnetic field measurements. In particular we hoped to measure the intensity of the Si IX line at 3.93 m, the most likely candidate line. The secondary aim of the experiment was to search for Rydberg transitions of neutral hydrogen and helium in the corona, previous observations of the infrared corona having produced evidence that cool, in coronal terms, material may co-exist in the corona with the hot (10⁶ K) plasma. The experiment did not succeed in the above aims as the Sun was obscured by cloud on the morning of the eclipse at the Roseland Observatory site. However, infrared observations of the sunlight scattered through the clouds produced a remarkable result. The infrared intensity fell precipitously 6.5 minutes before second contact and rose just as suddenly 6.5 minutes after third contact. The authors are unable to explain this result but suggest that it might be a terrestrial atmospheric rather than a solar phenomenon.
Intriguing observations from the total solar eclipse in Cornwall last year are reported by A Ridgeley, B Sheen, G Barnard, C Corrigan, G E Derbyshire, R Jones, P Moir-Riches, C Purchase, P D Read and T Richards.     

Solar dynamo and geomagnetic activity

The correlation between geomagnetic activity and the sunspot number in the 11-year solar cycle exhibits long-term variations due to the varying time lag between the sunspot-related and non-sunspot related geomagnetic activity, and the varying relative amplitude of the respective geomagnetic activity peaks. As the sunspot-related and non-sunspot related geomagnetic activity peaks are caused by different solar agents, related to the solar toroidal and poloidal fields, respectively, we use their variations to derive the parameters of the solar dynamo transforming the poloidal field into toroidal field and back. We find that in the last 12 cycles the solar surface meridional circulation varied between 5 and 20 m/s (averaged over latitude and over the sunspot cycle), the deep circulation varied between 2.5 and 5.5 m/s, and the diffusivity in the whole of the convection zone was ～10⁸ m²/s. In the last 12 cycles solar dynamo has been operating in moderately diffusion dominated regime in the bulk of the convection zone. This means that a part of the poloidal field generated at the surface is advected by the meridional circulation all the way to the poles, down to the tachocline and equatorward to sunspot latitudes, while another part is diffused directly to the tachocline at midlatitudes, “short-circuiting” the meridional circulation. The sunspot maximum is the superposition of the two surges of toroidal field generated by these two parts of the poloidal field, which is the explanation of the double peaks and the Gnevyshev gap in sunspot maximum. Near the tachocline, dynamo has been operating in diffusion dominated regime in which diffusion is more important than advection, so with increasing speed of the deep circulation the time for diffusive decay of the poloidal field decreases, and more toroidal field is generated leading to a higher sunspot maximum. During the Maunder minimum the dynamo was operating in advection dominated regime near the tachocline, with the transition from diffusion dominated to advection dominated regime caused by a sharp drop in the surface meridional circulation which is in general the most important factor modulating the amplitude of the sunspot cycle.     

On the Dependence of the Solar Wind Velocity on the Fractional Area of Coronal Holes in Longitude

Geomagnetism and Aeronomy - The relationship between the fractional area of coronal holes and the maximum velocity of the fast solar wind at 1 AU based on AIA/SDO and ACE/SWEPAM observations is...     

Formation Conditions and Energetics of Solar Nanoflares

The energy potential of solar nanoflares is estimated with a new approach proposed by the author. This approach is based on the drift mechanism for the formation of a dense loop structure in the magnetic field of a bipolar source. The densification process is assumed to proceed until the appearance of unmagnetized protons. These protons produce a current that heats the loop structure. The presence of bipolar sources is associated with local amplification of the background magnetic field by mesogranulation cells. The calculations conducted with the proposed model, which take into account observational data, yield a nanoflare energy range of 10²⁴–10²⁶ erg. The same estimates are obtained from the observed emission of nanoflare radiation. This fact is evidence, on the one hand, that the proposed model is adequate to the given process and, on the other hand, that there are no significant fluxes of the energy of this process as thermal conductivity and nonthermal particle beams. This situation is characterized by a maximum possible nanoflare energy release at a level of ≈10²⁷ erg during the mesogranule lifetime (≈10⁴ s), which yields an intensity of the energy flux of ≈10⁵ erg/s cm². This flux is insufficient to heat even the quiet regions of solar corona.     

Volcanism in the Solar System

Volcanic activity is the main process for heat-material exchange and circulation for differentiated planets. All terrestrial planets in the Solar System, the Moon, the satellites of giant planets, and the dwarf planets once experienced or are currently experiencing volcanic activities. This paper summarized the volcanism(main volcanic features and their formation) on the Moon, Mars, Venus, and Mercury in the inner Solar System, volcanism and cryovolcanism on satellites(Io, Europa,Enceladus) of g...     

Total Solar Irradiance Observations

The record of total solar irradiance (TSI) during the past 35?years has overlapping observations from space which can be merged to a composite, and three are available, namely the PMOD, the ACRIM and the IRMB composites. There are important differences between them, which are discussed in detail in order to find the best representation of solar variability during the last three cycles, for the following discussions of solar irradiance variability. Moreover, the absolute value of TSI from TIM on SORCE is 1,361?Wm^?2, substantially lower than the value 1,365?Wm^?2, which was observed by the classical radiometers. New results from specific experiments are now available, which are discussed in order to define the value to be used in, e.g., climate models. The most important issue regarding the recent TSI records is the low value observed during the minimum in 2009, which is 25% of a typical cycle amplitude lower than the value in 1996. The validity of this low value has been confirmed by comparing all existing TSI observations during cycle 23. On the other hand, activity indices, such as the sunspot number, the 10.7-cm radio flux (F10.7), the CaII and MgII indices and also the Ly-α irradiance or the frequency changes in low-order p modes, show a much smaller decreases relative to their respective typical cycle amplitude. It is most likely that an increasing contrast of the facular and network elements with decreasing magnetic field is responsible for this discrepancy. The value of TSI at minima is correlated with the open magnetic field of the Sun, B _R,?at minima. Using B _R at minima, interpolated linearly in between as a fourth component of a proxy model based on the photometric sunspot index and on the MgII index improves the explanation of the variance of TSI over the full period of the last three solar cycles to 84.7%. Results from other models are also discussed.     

Comparison of Solar and Geomagnetic Activity Effects on the Northern Hemisphere Weather Changes

The changes of pressure and temperature fields in the winter lower troposphere observed in association with changes in solar and/or geomagnetic activity are compared. It is shown that the fact whether it was solar or geomagnetic activity was not so important as whether the levels of the two activities were high or low. The differences between the effects of solar/geomagnetic activity, however, are revealed, the pressure and temperature data being stratified according to the QBO phase. The relationship obtained are discussed from the viewpoint of mechanisms resting upon both the planetary wave propagation and the changes of atmospheric air currents in the global electric circuit.     

Forecast of the Quasi-Stationary and Transient Solar Wind Streams Based on Solar Observations in 2010

Geomagnetism and Aeronomy - The results of the forecasting of quasi-stationary and transient solar wind streams velocity for a period from May to December 2010 are presented. The velocity of...