Anderson, Phillip C.

Permanent URI for this collectionhttps://hdl.handle.net/10735.1/4982

Phillip C. Anderson serves as Professor in the Department of Physics and as graduate advisor for physics majors. His research involves "the study of ionospheric and magnetospheric electrodynamics as well as the interaction of the Sun and the near-Earth environment and its effects on human technology & space weather."

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    An Auroral Boundary-Oriented Model of Subauroral Polarization Streams (SAPS)
    (Amer Geophysical Union) Landry, Russell G.; Anderson, Phillip C.; 0000-0003-1320-4064 (Landry, RG); Landry, Russell G.; Anderson, Phillip C.
    An empirical model of subauroral polarization stream (SAPS) electric fields has been developed using measurements of ion drifts and particle precipitation made by the Defense Meteorological Satellite Program from 1987 to 2012 and Dynamics Explorer 2 as functions of magnetic local time (MLT), magnetic latitude, the auroral electrojet index (AE), hemisphere, and day of year. Over 500,000 subauroral passes are used. This model is oriented in degree magnetic latitude equatorward of the aurora and takes median values instead of the mean to avoid the contribution of low occurrence frequency subauroral ion drifts so that the model is representative of the much more common, latitudinally broad, low-amplitude SAPS field. The SAPS model is in broad agreement with previous statistical efforts in the variation of the SAPS field with MLT and magnetic activity level, although the median field is weaker. Furthermore, we find that the median SAPS field is roughly conjugate in both hemispheres for all seasons, with a maximum in SAPS amplitude and width found for 1800-2000 MLT. The SAPS amplitude is found to vary seasonally only from about 1800-2000 MLT, maximizing in both hemispheres during equinox months. Because this feature exists despite controlling for the AE index, it is suggested that this is due to a seasonal variation in the flux tube averaged ionospheric conductance at MLT sectors where it is more likely that one flux tube footprint is in darkness while the other is in daylight.
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    Topside Ionospheric Response to Solar EUV Variability
    (Blackwell Publishing Ltd, 2016-02-05) Anderson, Phillip C.; Hawkins, Jessica M.; Anderson, Phillip C.; Hawkins, Jessica M.
    We present an analysis of 23 years of thermal plasma measurements in the topside ionosphere from the Defense Meteorological Satellite Program (DMSP) spacecraft. The H⁺/O⁺ ratio and density vary dramatically with the solar cycle; cross-correlation coefficients between E(10.7) and the daily averaged densities are greater than 0.85. The ionospheric parameters also vary dramatically with season, particularly at latitudes away from the equator where the solar zenith angle varies greatly with season. There are also 27 day solar rotation periodicities in the density, associated with periodicities in the directly measured solar EUV flux. Empirical orthogonal function analysis captures over 95% of the variation in the density in the first two principal components. The first principal component (PC1) is clearly associated with the solar EUV while the second principal component (PC2) is clearly associated with the solar zenith angle variation. The magnitude of the variation of the response of the topside ionosphere to solar EUV variability is shown to be closely related to the ionospheric composition. This is interpreted as the result of the effect of composition on the scale height in the topside ionosphere and the "pivot effect" in which the variation in density near the F(2) peak is amplified by a factor of e at an altitude a scale height above the F(2) peak. When the topside ionosphere is H⁺ dominated during solar minimum, DMSP may be much less than a scale height above the F(2) peak while during solar maximum, when it is O⁺ dominated, DMSP may be several scale heights above the F(2) peak.

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