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Solar proton flux origin and propagation in corona and interplanetary magnetic field regions from Pioneer satellites data
Cosmic ray intensity during solar cycles, considering minima relationship to Bartel index maxima and solar wind modulation theory
VLA-RATAN-600 observations of the sun around the partial solar eclipse in July 1990 are discussed. The relatively flat spectrum of the extended emission is attributed to the optically thin thermal bremsstrahlung of electrons trapped in a magnetic loop at coronal temperatures. Step-spectrum sunspot-associated emission is attributed to thermal gyroresonance radiation at different heights along the leg of a loop joining regions of positive magnetic polarity. Comparisons with predicted distributions of gyroresonance radio indicate that compact sunspot-associated sources lie at heights of 2500-17,500 km above the photosphere. Differences in the observed and predicted microwave emission suggest an inhomogeneous distribution of thermal plasma in the corona above the sunspot or the presence of localized flux tubes containing higher density plasma or nonpotential fields.
Review of proceedings from seminar on solar dendroclimatic relationships and discussion of predictions of sunspot activity on basis of tree ring variance
We used slit spectra from the 1995 flight of Goddard Space Flight Center's Solar EUV Rocket Telescope and Spectrograph (SERTS-95) to measure wavelength shifts of coronal emission lines in the core of NOAA active region 7870 relative to its immediate surroundings (its "edge"). This method circumvents the unavailability of reliable laboratory rest wavelengths for the observed lines by using wavelengths from the edge spectrum as references. We derived the, SERTS-95 wavelength calibration from measurements of a post-flight laboratory spectrum containing 28 He II and Ne II EUV standard wavelengths known to high accuracy. Wavelength measurements for lines of He I, Ne III, and additional lines of Ne II in the laboratory calibration spectrum provide more accurate values than were previously available, enabling these lines also to serve as future calibration standards. Six solar lines were chosen for this study, namely, He II at 303.78 A, Fe XII at 193.51 A, Fe XIII at 202.05 A, Fe XIV at 211.33 A, Fe XV at 284.15 A, and Fe XVI at 335.41 A. Because these lines are free from known blends in the SERTS-95 spectra and are either intrinsically strong or near the SERTS-95 peak sensitivity, they are our most reliable lines for measuring relative wavelength shifts in the spatially resolved active region core spectra. The iron ions are the hottest ions ever used for this type of analysis. All six lines reveal statistically significant spatial variations in their measured relative wavelength shifts in the active region core, including mixtures of blueshifts and redshifts (each with maximum values corresponding to relative Doppler velocities approximately 15 km/s), indicating a dynamic, turbulent corona. For each of these lines we calculated weighted-average relative Doppler velocities from the wavelength shifts in the spatially resolved core spectra by weighting the shifts in the individual spatial pixels with their respective measurement uncertainties.
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Solar soft X rays observed from OSO-3, correlating to solar flares and radio bursts
A unified overview of present knowledge of the geomagnetic response to the dynamic solar wind is reported. The formation of the magnetosphere and the magnetospheric tail is discussed the importance of electric fields is stressed, and the magnetospheric convection of plasma and frozen-in magnetic field lines under the influence of large scale magnetospheric electric fields is outlined. Ionospheric electric fields and currents are intimately related to electric fields and currents in the magnetosphere and the strong coupling between the two regions is discussed. The energy input of the solar wind to the magnetosphere and upper atmosphere is discussed in terms of the reconnection model where interplanetary magnetic field lines merge or connect with the terrestrial field on the sunward side of the magnetosphere. The merging model emphasizes the importance of the interplanetary magnetic field and especially the north-south component. The solar sector structure with its organized magnetic field and embeeded high speed plasma streams is identified as the source of recurrent geomagnetic disturbances while flare associated interplanetary shock waves are the source of most violet and sporadic geomagnetic storms.
The models for sunspots are combined into an active region model with consideration for the energy flow beneath active regions. An apparent average energy balance exists between the sunspot deficit and the facular excess, i.e., no 11 year variations in solar luminosity associated with the activity centers. This is seen as a consequence of the upper convection zone's inability to store these significant amounts of energy for periods greatly in excess of weeks. This view is supported by observed active region behavior and detailed numerical modelling. Increases in facular and spot brightness are nearly commensurate, with the faculae outlasting the spots on time scales of the order of weeks to a couple of months. Foukal finds the radiation (deficit from a sunspot blocking model) recovers slowly on a timescale of approximately 83 days.
Several related investigations of the possible influence of the solar and interplanetary magnetic sector structure on the atmospheric circulation are described. The area of low pressure troughs in the northern hemisphere has a minimum about one day after a warped heliospheric current sheet has been carried past the earth by the solar wind. Possible physical mechanisms could relate to phase changes in meteorological processes, changes in atmospheric electricity or changes in solar extreme ultraviolet irradiation. A quantitative analysis suggests that the accuracy of weather forcasting decreases during the two days after the warped heliospheric current sheet has passed the earth. A description is given of several further investigations in progress.
The detection of a significant correlation between the solar irradiance, corrected for flux deficit due to sunspots, and both the 205 nm flux and a photometric facular index were examined. A detailed analysis supports facular emission as the more likely source of correlation with the corrected radiance, rather then the error in sunspot correction. A computer program which simulates two dimensional convection in a compressible, stratified medium was investigated. Subroutines to calculate ionization and other thermodynamic variables were also completed.
We are currently experiencing a period of high solar radiation combined with wide short-term fluctuations in the radiation. The short-term fluctuations, especially when combined with highly energetic solar flares, can adversely affect the mission of U.S. Space Command's Space Surveillance Center (SSC) which catalogs and tracks the satellites in orbit around the Earth. Rapidly increasing levels of solar electromagnetic and/or particle radiation (solar wind) causes atmospheric warming, which, in turn, causes the upper-most portions of the atmosphere to expand outward, into the regime of low altitude satellites. The increased drag on satellites from this expansion can cause large, unmodeled, in-track displacements, thus undermining the SSC's ability to track and predict satellite position. On 13 March 1989, high solar radiation levels, combined with a high-energy solar flare, caused an exceptional amount of short-term atmospheric warming. The SSC temporarily lost track of over 1300 low altitude satellites--nearly half of the low altitude satellite population. Observational data on satellites that became lost during the days following the 13 March 'solar event' was analyzed and compared with the satellites' last element set prior to the event (referred to as a geomagnetic storm because of the large increase in magnetic flux in the upper atmosphere). The analysis led to a set of procedures for reducing the impact of future geomagnetic storms. These procedures adjust selected software limit parameters in the differential correction of element sets and in the observation association process and must be manually initiated at the onset of a geomagnetic storm. Sensor tasking procedures must be adjusted to ensure that a minimum of four observations per day are received for low altitude satellites. These procedures have been implemented and, thus far, appear to be successful in minimizing the effect of subsequent geomagnetic storms on satellite tracking and ephemeris computation.
I review recent space-borne and ground-based observations of cyclical solar phenomena, from the interior to the inner heliosphere. Two classes of observations will be stressed: those that bear on the generation and emergence of subsurface magnetic fields, and those that elucidate magnetic reorganization in the corona.
During the Helios mission a total of 391 fast forward non-corotating interplanetary shock waves was identified. For most of the 12 years between 1974 and 1986 unique shock detection was possible for more than 80 % of the time. The occurrence rate (in shocks per day) varied from 0.02 at activity minimum in 1976 to 0.17 in 1979 and 0.22 in 1982 with a significant drop to 0.13 in 1980, i.e. right at activity maximum. The average properties of all events as functions of solar distance. phase in the solar cycle, heliographic and -magnetic latitude and others are discussed.
Thermospheric neutral particle molecular nitrogen density and temperature measurements by rockets, noting correlations with diurnal, solar cycle and other variations
Results of observation of solar wind fluxes near earth obtained by Venera 2 and Venera 4 satellites
The suggestion that galactic cosmic rays (GCR) as modulated by the solar wind are the carriers of the component of solar variability that affects weather and climate has been discussed in the literature for 30 years, and there is now a considerable body of evidence that supports it. Variations of GCR occur with the 11 year solar cycle, matching the time scale of recent results for atmospheric variations, as modulated by the quasibiennial oscillation of equatorial stratospheric winds (the QBO). Variations in GCR occur on the time scale of centuries with a well defined peak in the coldest decade of the little ice age. New evidence is presented on the meteorological responses to GCR variations on the time scale of a few days. These responses include changes in the vertical temperature profile in the troposphere and lower stratosphere in the two days following solar flare related high speed plasma streams and associated GCR decreases, and in decreases in Vorticity Area Index (VAI) following Forbush decreases of GCR. The occurrence of correlations of GCR and meteorological responses on all three time scales strengthens the hypothesis of GCR as carriers of solar variability to the lower atmosphere. Both short and long term tropospheric responses are understandable as changes in the intensity of cyclonic storms initiated by mechanisms involving cloud microphysical and cloud electrification processes, due to changes in local ion production from changes in GCR fluxes and other high energy particles in the MeV to low GeV range. The nature of these mechanisms remains undetermined. Possible stratospheric wind (particularly QBO) effects on the transport of HNO3 and other constituents incorporated in cluster ions and possible condensation and freezing nuclei are considered as relevant to the long term variations.
An analysis is presented of the variability of centimeter wavelength emission originating from the solar transition region and lower corona, and the variability is compared with the sun's quiescent emission. Sequential dual wavelength observations are presented and used to put constraints on a possible model of the variability of active region emissions and to better understand the dynamics of active regions. It is shown that gyroresonance emission contributes significantly to the active region emission at 6 cm, whereas all the quiet-sun emission can be attributed to free-free emission. From comparison of the quiet-sun and active region models, it is shown that the density at the base of the transition region is higher in active regions.