Ionospheric climatology derived from gps occultation observations made by the ionospheric occultation experiment

The ionospheric occultation experiment (IOX) is a GPS occultation sensor with an ionospheric mission focus. IOX measurements of GPS L1 and L2 carrier phase during Earth limb views of setting GPS satellites are used together with the Abel transform to determine vertical profiles of electron density from which F-region peak parameters are determined. Data from a four and a half month period beginning in November 2001 are statistically binned and compared with a climatological model. To account for potential errors in interpretation that could arise from violation of the Abel transform assertion of spherical symmetry, the data are compared to both the climatology and to statistics of simulated ionospheric inversions using the climatological model. General characteristics of the climatology are reproduced by the occultation data. However, several significant discrepancies between the model and the data are observed during this near-solar maximum time period. In particular, average mid-latitude daytime densities are shown to be higher than the climatological prediction and the height of F2 layer in the post-sunset equatorial region is underestimated by up to 150 km.

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A Maunder Minimum Scenario Based on Cross-Hemispheric Coupling and Intermittency

A novel scenario for Maunder minimum-like grand minima epochs of reduced solar activity is proposed, based on diffusive coupling between both solar hemispheres, each susceptible to stochastically-driven intermittent behavior. After introducing cross-hemispheric coupling into a well-validated reduced model of the solar cycle based on the Babcock–Leighton mechanism for poloidal field regeneration, simulations are presented demonstrating that even weak coupling can lead to a high degree of synchronicity between the two hemispheres. This is in qualitative agreement with the similar onset and recovery times of sunspot activity at and around the Maunder minimum. Moreover, even weak coupling manages to greatly reduce the frequency and duration of quiescent episodes, again in qualitative agreement with the relative paucity of grand minima in the sunspot and radioisotope records.     

Drift velocity at the wave breaking point

Wave-tank studies were conducted on the measurement of the drift velocity at the breaking point under different types of breaking waves on a rigid, plane beach. The drift velocity has onshore direction near the surface and close to the bottom; in the main flow column, the drift velocity is always offshore. The offshore drift velocity shows a more uniform vertical distribution than that in the offshore region. The experimental data are compared with theoretical values of three different second-order constant-depth wave theories. Comparisons with data from other sources are also made.     

Long term storage of relativistic particles in the solar corona

A model is presented which shows that large numbers of energetic electrons (0.3-> 10 MeV) and protons (1–30 MeV) can be stored in the solar corona at altitudes around 3 × 10⁵ km for periods in excess of 5 days. Specific reference is made to the time period July 6–16 1968 as an excellent example of energetic solar particle storage. Time histories of interplanetary charged particle intensities observed by the IMP-4 and Pioneer 8 satellites are used to substantiate this contention. Detailed reference is also made to solar X-ray, optical and radio data obtained during the period in question, in addition to interplanetary magnetometer data. This model provides a unique solution to many hitherto unexplained solar particle events, and can also account for the lack of prompt particle emission from certain large solar flares recorded in the past.     

Solar irradiance between 120 and 400nm and its variations

The solar ultraviolet irradiance measurements in the 120–400 nm wavelength range are reviewed and compared showing still important discrepancies between the irradiance values deduced from the most recent observations.The possible variations of the solar ultraviolet irradiances with the 27-day rotation period of the Sun and with the 11-year activity cycle are presented and discussed on the basis of the available irradiation fluxes obtained during the rising phase of solar cycle 21.The spectral features of both kinds of variation are clearly related to the solar atmospheric layer from which the corresponding radiation is emitted.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

Solar flux determination in the spectral range 150–210 nm

Solar irradiation fluxes are determined between 150 and 210 nm from stigmatic spectra of the Sun obtained by means of a rocket-borne spectrograph. Absolute intensities at the disk center with a spectral resolution of 0.04 nm and a spatial resolution of 7 arc sec are presented. From center-to-limb intensity variations determined from the same spectra, mean full disk intensities of the quiet Sun can be deduced. In order to compare them with other measurements, the new solar fluxes have been averaged over a bandpass of 1 nm.     

A solar flare videometer

A new instrument, called a videometer, has been developed to measure solar flare area, peak intensity and integrated intensity in real time. The videometer uses a closed circuit television system to convert an optical H image into electrical signals for measurement. Observations of two Class I flares with the videometer are discussed.