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WN4 variability in DMSP ion densities across season, solar cycle, and local time
Author(s) -
Hawkins J. M.,
Anderson P. C.
Publication year - 2017
Publication title -
journal of geophysical research: space physics
Language(s) - English
Resource type - Journals
eISSN - 2169-9402
pISSN - 2169-9380
DOI - 10.1002/2017ja024065
Subject(s) - longitude , ionosphere , thermosphere , atmospheric sciences , latitude , defense meteorological satellite program , solar cycle , troposphere , environmental science , atmosphere (unit) , equinox , satellite , climatology , geology , meteorology , physics , geodesy , geophysics , solar wind , plasma , astronomy , quantum mechanics
Nonmigrating tides are a major coupling mechanism between the different regions of the atmosphere and ionosphere. The wave number 4 (WN4) pattern in the ionosphere has been recognized as originating primarily with the diurnal eastward propagating wave‐3 nonmigrating tide (DE3) in the troposphere, and significant effort has been devoted in recent years to understanding how tidal effects manifest in various physical parameters across a very wide range of altitudes. While DE3 and WN4 signatures have been much studied in the mesosphere‐lower thermosphere region, relatively little is known about how WN4 impacts the ionosphere above the F peak. We present an analysis of WN4 in the topside ionosphere as measured by the Defense Meteorological Satellite Program (DMSP) spacecraft, using monthly averages of total ion densities and composition binned by latitude and longitude. We found that WN4 is most strongly present during September equinox. In May–August, ion densities near 180–270 geographic longitude (GLON) are enhanced and the WN4 pattern moves 5–10° north; in November–February, ion densities are reduced in this region and WN4 moves 5–10° south. No solar cycle effects were found in the magnitude of dN / N . The longitude position of the peaks (phase) was observed to vary by about 10° with F10.7, moving eastward with increasing F10.7. The latitude variation was less than 5° and did not show a trend with F10.7. The WN4 pattern changes rapidly near dawn but is very constant throughout the afternoon and evening in terms of dN / N and drifts eastward at about 2° GLON per hour magnetic local time.