Causes of the longitudinal differences in the equatorial vertical E × B drift during the 2013 SSW period as simulated by the TIME-GCM

During stratospheric sudden warming (SSW) periods large changes in the low‐latitude vertical drift have been observed at Jicamarca as well as in other longitudinal sectors. In general, a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed. Durin...

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Bibliographic Details
Published in:Journal of geophysical research. Space physics 2015-06, Vol.120 (6), p.5117-5136
Main Authors: Maute, A., Hagan, M. E., Yudin, V., Liu, H.-L., Yizengaw, E.
Format: Article
Language:English
Subjects:
Atmospheric circulation
Atmospheric research
Atmospherics
Computer simulation
Daytime
Diurnal variations
Drift
Electrodynamics
equatorial vertical drift
General circulation models
Geomagnetic activity
geomagnetic forcing
Geomagnetism
Geophysics
Ionosphere
lower atmosphere forcing
Mesosphere
Meteorology
Numerical experiments
Rotating generators
Simulation
Solar tides
Stratosphere
stratospheric sudden warming
Stratospheric warming
Temperature
Thermosphere
Tides
Vertical drift
Wave propagation
Wind
Zonal waves
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Summary:During stratospheric sudden warming (SSW) periods large changes in the low‐latitude vertical drift have been observed at Jicamarca as well as in other longitudinal sectors. In general, a strengthening of the daytime maximum vertical drift with a shift from prenoon to the afternoon is observed. During the January 2013 stratospheric warming significant longitudinal differences in the equatorial vertical drift were observed. At Jicamarca the previously reported SSW behavior prevails; however, no shift of the daytime maximum drift was exhibited in the African sector. Using the National Center for Atmospheric Research thermosphere‐ionosphere‐mesosphere electrodynamics general circulation model (TIME‐GCM) the possible causes for the longitudinal difference are examined. The timing of the strong SSW effect in the vertical drift (15–20 January) coincides with moderate geomagnetic activity. The simulation indicates that approximately half of the daytime vertical drift increase in the American sector may be related to the moderate geophysical conditions (Kp = 4) with the effect being negligible in the African sector. The simulation suggests that the wind dynamo accounts for approximately 50% of the daytime vertical drift in the American sector and almost 100% in the African sector. The simulation agrees with previous findings that the migrating solar tides and the semidiurnal westward propagating tide with zonal wave number 1 (SW1) mainly contribute to the daytime wind dynamo and vertical drift. Numerical experiments suggest that the neutral wind and the geomagnetic main field contribute to the presence (absence) of a local time shift in the daytime maximum drift in the American (African) sector. Key Points TIME‐GCM can reproduce the SSW signature in the observed vertical E × B drift Strong longitudinal differences in the vertical E × B drift during the 2013 SSW Moderate geomagnetic activity causes part of longitudinal variation in E × B drift
ISSN:2169-9380
2169-9402
DOI:10.1002/2015JA021126