Decameter radio emission from Jupiter and solar activity.
Jovian decametric emission correlated to solar activity, noting artificial periodicities of Jupiter data due to observational procedures
Sastry, Ch. V.↗
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The response of the neutral upper atmosphere to variations in solar activity
Neutral upper atmosphere response to solar activity variations, discussing temperature, density and helium/oxygen composition
Keating, G. M.↗
Force-free magnetic-field structures and their role in solar activity.
Magnetic-field structures in solar active regions are expected to be substantially force-free. A method is proposed for calculating such structures by numerical methods. The method is applied to the study of the magnetic-field pattern associated with a sunspot of one polarity surrounded by a magnetic region of opposite polarity when the sunspot rotates with respect to the surrounding region. Rotation introduces a toroidal component of magnetic field, and the associated pressure leads to inflation of the magnetic field pattern. If the differential rotation exceeds about 180 deg, the force-free magnetic field has energy greater than that of an open magnetic-field configuration with the same photospheric boundary conditions. It is concluded that, beyond this point, the force-free field structure is metastable and can be converted into an open field structure by an explosive MHD instability.
Barnes, C. W.↗
Solar activity, magnetic clouds, and geomagnetic storms
Associational aspects of magnetic clouds and solar activity, and of magnetic clouds and geomagentic storms are described. For example, recent research has shown associations to exist between the launch of magnetic clouds directed Earthward from the Sun and, in particular, two forms of solar activity: flare-related, type II metric radio bursts and disappearing filaments (prominences). Furthermore, recent research has shown an association to exist between the onset of magnetic clouds on Earth and the initiation of geomagnetic storms. Based on these findings, STIP Intervals XV-XIX are examined for possible occurrences of Earthward-directed magnetic clouds.
Wilson, Robert M.↗
The difference in the energy spectra of galactic cosmic rays at the minima of the 19th and 20th solar activity cycles
The absorption curves of the cosmic ray charged component for solar minima in 1965 and 1975 to 1977 are analyzed on the basis of daily stratospheric measurements in Murmansk, Moscow, Alma-Ata and Mirny (Antarctic). Two distinct features in the energy spectra of galactic cosmic rays are revealed during these periods. At the 20th solar activity minimum there was the additional short range component of cosmic rays. Additional fluxes in the stratosphere at high latitudes caused by this component are probably protons and He nuclei with the energy 100 to 500 MeV/n. The fluxes are estimates as Approx. 300 sq m/s/sr. At the minimum in 1975 to 1977 the proton intensity in the energy range 1 to 15 GeV is 10 to 15% lower than that in the 1965 solar activity minimum.
Svirzhevskaya, A. K.↗
Solar activity during Skylab: Its distribution and relation to coronal holes
Solar active regions observed during the period of Skylab observations (May 1973-February 1974) were examined for properties that varied systematically with location on the sun, particularly with respect to the location of coronal holes. Approximately 90 percent of the optical and X-ray flare activity occurred in one solar hemisphere (136-315 heliographic degrees longitude). Active regions within 20 heliographic degrees of coronal holes were below average in lifetimes, flare production, and magnetic complexity. Histograms of solar flares as a function of solar longitude were aligned with H alpha synoptic charts on which active region serial numbers and coronal hole boundaries were added.
Speich, D. M.↗
A correlative study of ssc's, interplanetary shocks, and solar activity
Ninety-three ssc's during the 4-year period from 1968 to 1971 at and near the peak of the solar activity cycle were examined. Of the 93 ssc's, 81 could be associated with solar activity such as solar flares and type 2 and type 4 radio bursts. Disturbances associated with 48 of the ssc's have been studied in detail by using the corresponding interplanetary (IP) magnetic field and plasma data when they were available. It was found that 41 of the 48 disturbances corresponded to IP shock waves, and the remaining 7 events were tangential discontinuities. Thirty per cent of the IP shocks had thick structure (i.e., the magnetic field jump across the shock occurred over a distance much greater than 50 proton Larmor radii). By considering the orientations of 22 well-determined shock normals in relation to the positions of the parent flares on the solar disk, it is suggested that a typical shock front propagating out from the sun at 1 AU has a radius of curvature of the order of 1 AU.
Chao, J. K.↗
A correlative study of SSC's, interplanetary shocks, and solar activity
A total of 93 SSC's were examined during the four year period from 1968 to 1971 at and near the peak of the solar activity cycle. Of the 93 SSC's 81 could be associated with solar activity, such as solar flares and radio bursts of Type II and Type IV. The mean propagation speeds of these flare-associated events ranged from 400 to 1000 km/sec with an average speed of 600-700 km/sec. Disturbances associated with 48 of the SSC's have been studied in detail using the corresponding interplanetary (IP) magnetic field, and plasma data when they were available. It was found that 41 of the 48 disturbances corresponded to IP shock waves, and the remaining seven events were tangential discontinuities. Thirty percent of the IP shocks had thick structure (i.e. the magnetic field jump across the shock occurred over a distance much greater than 50 proton Larmor radii). Also given is a statistical study of the gross geometry of a typical or average shock surface based on multiple spacecraft sightings and their relative orientation with respect to the solar flare. It is suggested that a typical shock front propagating out from the sun at l AU has a radius of curvature on the order of l AU. Also given are some general properties of oblique IP flare-shocks.
Chao, J. K.↗
Indices of solar activity, appendix 6
Indices of solar & geomagnetic activity, variation of earth magnetic field in time & space, & field variation in magnetic storm
SOLAR ACTIVITY EFFECT↗
Method and apparatus for measuring solar activity and atmospheric radiation effects
A radiometric measuring system is described for observing solar activity, atmospheric attenuation, and atmospheric emission. Two highly directional microwave antennas are mounted side by-side on an equatorial mount which tracks the sun. One antenna is aimed directly at the sun to provide a sun temperature, and the other antenna is aimed at a slight angle to the sun antenna to provide a sky temperature reference. Signals from the two antennas are compared in a radiometric detecting system and provide information concerning solar activity and atmospheric attenuation and emission.
Haroules, G. G.↗
Are Solar Activity Variations Amplified by the QBO: A Modeling Study
Solar cycle activity effects (SCAE) in the lower and middle atmosphere, reported in several studies, are difficult to explain on the basis of the small changes in solar radiation that accompany the 11-year cycle. It is therefore natural to speculate that dynamical processes may come into play to produce a leverage. Such a leverage may be provided by the Quasi-Biennial Oscillation (QBO) in the zonal circulation of the stratosphere, which has been linked to solar activity variations. Driven primarily by wave mean flow interaction, the QBO period and its amplitude are variable but are also strongly influenced by the seasonal cycle in the solar radiation. This influence extends to low altitudes and is referred to as 'downward control'. Small changes in the solar radiative forcing may produce small changes in the period and phase of the QBO, but these in turn may produce measurable differences in the wind field. Thus, the QBO may be an amplifier of solar activity variations and a natural conduit of these variations to lower altitudes. To test this hypothesis, we conducted experiments with a 2D version of our Numerical Spectral Model that incorporates Hines' Doppler Spread Parameterization for small-scale gravity waves (GW). Solar cycle radiance variations (SCRV) are accounted for by changing the radiative heating rate on a logarithmic scale from 0.1% at the surface to 1% at 50 km to 10% at 100 km. With and without SCRV, but with the same GW flux, we then conduct numerical experiments to evaluate the magnitude of the SCAE in the zonal circulation. The numerical results indicate that, under certain conditions, the SCAE is significant and can extend to lower altitudes where the SCRV is small. For a modeled QBO period of 30 months, we find that the seasonal cycle in the solar forcing acts as a strong pacemaker to lock up the phase and period of the QBO. The SCAE then shows up primarily as a distinct but relatively weak amplitude modulation. But with a different QBO period between 30 and 34 (or less than 30, presumably) months, the seasonal phase lock is weak. Solar flux variations in the seasonal cycle then cause variations in the QBO period and phase. These amplify the SCAE to produce relatively large variations in the wind field. The SCAE in this case extends to mid-latitudes.
Mengel, J. G.↗
Influence of solar activity upon light curves of comets P/Halley (1986 3) and P/Churyumov-Gerasimenko (1982 8)
It is shown that the comet P/Halley's (1986 3) total magnitudes correlate with changes in the solar activity indices and the solar wind velocity. A statistically reliable correlation between the outbursts of brightness and magnitude variations of the short-period comet Churyumov-Gerasimenko (1982 8) and the level of the solar activity has been discovered.
Churyumov, Klim I.↗
An analysis of the solar-activity effects in the upper atmosphere
A study of the upper-atmosphere variations induced by solar activity was made by using 29,574 densities derived from the drag of 10 satellites in the interval 1958-1971. In a comparison of the respective merits of the Ca II-plage index and the 10.7 cm solar flux to represent the erratic ('27 day') component of the variation, the latter is shown to give invariably better results. The ratio of the temperature variations to the variations of the decimetric flux is shown to vary considerably with solar activity, but little with height or with local solar time. The time lag of the atmospheric variations behind those of the decimetric flux varies from a minimum of 0.9 day at noon to 1.6 days at midnight.
Jacchia, L. G.↗
An analysis of the solar-activity effects in the upper atmosphere.
A study of the upper-atmosphere variations induced by solar activity was made by using 29,574 densities derived from the drag of ten satellites in the interval from 1958 to 1971. In a comparison of the respective merits of the Ca II plage index and the 10.7-cm solar flux to represent the erratic (27-day) component of the variation, the latter is shown to give invariably better results. The ratio of the temperature variations to the variations of the decimetric flux is shown to vary considerably with solar activity, but little with height or with local solar time. The time lag of the atmospheric variations behind those of the decimetric flux varies from a minimum of 0.9 day at noon to 1.6 days at midnight.
Jacchia, L. G.↗
Nonlinear techniques for forecasting solar activity directly from its time series
Numerical techniques for constructing nonlinear predictive models to forecast solar flux directly from its time series are presented. This approach makes it possible to extract dynamical invariants of our system without reference to any underlying solar physics. We consider the dynamical evolution of solar activity in a reconstructed phase space that captures the attractor (strange), given a procedure for constructing a predictor of future solar activity, and discuss extraction of dynamical invariants such as Lyapunov exponents and attractor dimension.
Ashrafi, S.↗
Initiation of non-tropical thunderstorms by solar activity
Correlative evidence accumulating since 1926 suggests that there must be some physical coupling mechanism between solar activity and thunderstorm occurrence in middle to high latitudes. Such a link may be provided by alteration of atmospheric electric parameters through the combined influence of high-energy solar protons and decreased cosmic ray intensities, both of which are associated with active solar events. The protons produce excess ionization near and above 20km, while the Forbush decreases a lowered conductivity and enhanced fair-weather atmospheric electric field below that altitude. Consequent effects ultimately lead to a charge distribution similar to that found in thunderclouds, and then other cloud physics processes take over to generate the intense electric fields required for lightning discharge.
Herman, J. R.↗
Solar activity and its relation to certain parameters of phenomena in the geophysical complex
Results of a detailed analysis of solar activity in 1957-1965 are compared with the data on solar activity with variations of cosmic ray activity, and geomagnetic, ionospheric and terrestrial currents. Cosmic ray variations are investigated with reference to the asymmetry of solar hemispheres. All storms in the IGY are classified and a symbolic diagram of the time sequence is drawn up.
Razmadze, T. S.↗
The Heliosphere Through the Solar Activity Cycle
Understanding how the Sun changes though its 11-year sunspot cycle and how these changes affect the vast space around the Sun the heliosphere has been one of the principal objectives of space research since the advent of the space age. This book presents the evolution of the heliosphere through an entire solar activity cycle. The last solar cycle (cycle 23) has been the best observed from both the Earth and from a fleet of spacecraft. Of these, the joint ESA-NASA Ulysses probe has provided continuous observations of the state of the heliosphere since 1990 from a unique vantage point, that of a nearly polar orbit around the Sun. Ulysses results affect our understanding of the heliosphere from the interior of the Sun to the interstellar medium - beyond the outer boundary of the heliosphere. Written by scientists closely associated with the Ulysses mission, the book describes and explains the many different aspects of changes in the heliosphere in response to solar activity. In particular, the authors describe the rise in solar ESA and NASA have now unamiously agreed a third extension to operate the highly successful Ulysses spacecraft until March 2008 and, in 2007 and 2008, the European-built space probe will fly over the poles of the Sun for a third time. This will enable Ulysses to add an important chapter to its survey of the high-latitude heliosphere and this additional material would be included in a 2nd edition of this book.
Balogh, A.↗