Solar Irradiance Observed from PVO and Inferred Solar Rotation

Solar irradiance in the extreme ultraviolet flux (EUV) has been monitored for 11 years by the Pioneer Venus Orbiter (PVO). Since the experiment moves around the Sun with the orbital rate of Venus rather than that of Earth, the measurement gives us a second viewing location from which to begin unravelling which irradiance variations are intrinsic to the Sun, and which are merely rotational modulations whose periods depend on the motion of the observer. Researchers confirm an earlier detection, made with only 8.6 years of data, that the EUV irradiance is modulated by rotation rates of two families of global oscillation modes. One family is assumed to be r-modes occupying the convective envelope and sharing its rotation, while the other family (g-modes) lies in the radiative interior which as a slower rotation. Measured power in r-modes of low angular harmonic number indicates that the Sun's envelope rotated about 0.7 percent faster near the last solar maximum (1979 thru 1982) than it did during the next rise to maximum (1986 to 1989). No change was seen in the g-mode family of lines, as would be expected from the much greater rotational inertia of the radiative interior

Use of Langmuir probes in non-Maxwellian space plasmas

Disturbance of the Maxwellian plasma may occur in the vicinity of a spacecraft due to photoemission, interactions between the spacecraft and thermospheric gases, or electron emissions from other devices on the spacecraft. Significant non-Maxwellian plasma distributions may also occur in nature as a mixture of ionospheric and magnetospheric plasmas or secondaries produced by photoionization in the thermosphere or auroral precipitation. The general formulas for current collection (volt–ampere curves) by planar, cylindrical, and spherical Langmuir probes in isotropic and anisotropic non-Maxwellian plasmas are examined. Examples are given of how one may identify and remove the non-Maxwellian components in the Langmuir probe current to permit the ionospheric parameters to be determined. Theoretical volt–ampere curves presented for typical examples of non-Maxwellian distributions include: two-temperature plasmas and a thermal plasma with an energetic electron beam. If the nonionospheric electrons are Maxwellian at a temperature distinct from that of the ionosphere electrons, the volt–ampere curves can be fitted directly to obtain the temperatures and densities of both electron components without resorting to techniques that attempt to derive the plasma distribution from the current by taking derivatives. For an arbitrary isotropic distribution, the current for retarded particles is shown to be identical for the three geometries. For anisotropic distributions, the three probe geometries are not equally suited for measuring the ionospheric electron temperature and density or for determining the distribution function in the presence of non-Maxwellian background electrons. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70117/2/RSINAK-70-7-3015-1.pd

Pioneer Venus Orbiter Measurements of Solar EUV Flux During Solar Cycles 21 and 22

The Pioneer Venus Orbiter (PVO) had on board the electron temperature probe experiment which measured temperature and concentration of electrons in the ionosphere of Venus. When the probe was outside the Venus ionosphere and was in the solar wind, the probe current was entirely due to solar photons striking the probe surface. This probe thus measured integrated solar EUV flux (Ipe) over a 13-year period from January 1979 to December 1991, thereby covering the declining phase of solar cycle 21 and the rising phase of solar cycle 22. In this paper, we examine the behavior of Ipe translated to the solar longitude of Earth (to be called EIpe) during the two solar cycles. We find that total EUV flux changed by about 60% during solar cycle 21 and by about 100% in solar cycle 22. We also compare this flux with other solar activity indicators such as F_10.7 , Lα, and the solar magnetic field. We find that while the daily values of EIpe are highly correlated with F_10.7 (correlation coefficient 0.87), there is a large scatter in EIpe for any value of this Earth-based index. A comparison of EIpe with SME and UARS SOLSTICE Lα measurements taken during the same period shows that EIpe tracks Lα quite faithfully with a correlation coefficient of 0.94. Similar comparison with the solar magnetic field (Bs) shows that EIpe correlates better with Bs than with F_10.7 . We also compare EIpe with total solar irradiance measured during the same period.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43713/1/11207_2004_Article_140430.pd

On the kinetic theory of the Lorentz gas

http://deepblue.lib.umich.edu/bitstream/2027.42/5560/5/bac4662.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5560/4/bac4662.0001.001.tx

The Dumbbell electrostatic ionosphere probe : theoretical aspects

http://deepblue.lib.umich.edu/bitstream/2027.42/5561/5/bac4879.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/5561/4/bac4879.0001.001.tx

A theoretical study of the effect of collective interaction on the electron temperature in the ionosphere and of the Langmuir probe characteristics in the presence of a magnetic field: semiannual report no. 1

http://deepblue.lib.umich.edu/bitstream/2027.42/4937/5/bac2278.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/4937/4/bac2278.0001.001.tx

Ionospheric ion composition from satellite measurements made during 1970-1980: Altitude profiles

Ion mass spectrometers were carried by a number of satellites in the 1970s. The ion composition measurements from two of these missions, the Orbiting Geophysical Observatory-6 and the Atmosphere Explorer-C, have been collected into an ion composition data base to evaluate several widely used empirical and theoretical models for the species H+, He+, N+, O+, NO+, N2+, and O2+. The data base covers all latitudes and local times, and the altitude range from 150 km to 1200 km, but here we present altitude plots of the ion densities at noon and at dip latitudes of 20-40[deg] N. The satellite data are compared with an early ion density profile by Johnson, with the Kochnlein and IRI-90 empirical models, and with the Utah State University theoretical ionosphere model. These comparisons serve to verify some aspects of the models, but they also reveal some outstanding differences. The solar activity dependence of H+, He+, N+, and O+ is demonstrated, although this has not been possible for the molecular ions because low altitude measurements have not been made near solar maximum.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/29568/1/0000656.pd

The photoelectron energy distribution in the ionosphere ; Theoretical study of the moving Langmuir probe in the presence of a magnetic field ; Theoretical study of the response of a probe to plasma waves : annual report no. 1

http://deepblue.lib.umich.edu/bitstream/2027.42/4933/5/bac3066.0001.001.pdfhttp://deepblue.lib.umich.edu/bitstream/2027.42/4933/4/bac3066.0001.001.tx

Atmospheric Effects of Biomass Burning in Madagascar

Simultaneous tropospheric ozone and aerosols observed using the TOMS satellite instrument are reported for Madagascar during the 1979 through 1999 time period Ozone observations made using the TOMS tropospheric ozone convective-cloud differential method show that the tropospheric ozone amount associated with Madagascar has an average monthly value of 30 DU (Dobson units). The average value is enhanced by 10 to 15 DU in October This maximum coincides with the time of maximum biomass area burning in Madagascar and parts of southern Africa. The aerosol index derived from TOMS is examined for correlation with biomass burning in Madagascar and southern Africa. There is good correlation between a satellite observation derived fire index for different parts of Madagascar, tropospheric ozone and the TOMS aerosol index in the same geographical area. Aerosols from fires were found to reach their peak in November and to persist over Madagascar until sometime in December