Response of the Ionospheric TEC at the American low latitudes to SSW and
storm-time induced SSW
Abstract
We investigated the American low-latitude ionosphere around 75°W during
the two 2013 sudden stratospheric warming (SSW) events: one in quiet
geomagnetic conditions, and the other overlapped by a minor geomagnetic
storm using total electron content (TEC) data from 12 Global Positioning
System (GPS) receivers. A pair of magnetometers revealing the varying
inferred vertical E X B drift and the NASA Thermosphere Ionosphere
Mesosphere Energetics and Dynamics (TIMED) satellite airglow instrument
to understand the global changes in the neutral composition, O⁄N_2
ratio are also used. The late morning inferred downward-directed E X B
drift during the first major SSW did not support the varying equatorial
ionization anomaly (EIA) signature. However, during the second major
SSW, the well-reported and enhanced late morning inferred
upward-directed E X B drift relocated a northern EIA crest to higher
latitudes. Interestingly, the effect of a minor geomagnetic storm on 17
January 2013 that modulated the ongoing second SSW reduced the maximum
inferred upward-directed E X B drift. The second major SSW contribution
to the northern crest is higher than photo-ionization and the first
major SSW contribution, while each major contribution is higher than
minor warming. The minor geomagnetic storm reduced the effect of the
second major SSW on the TEC from 58% to 50% and 28% to 20% at the
northern and southern crest, respectively. Also, the storm’s overall
effect of - 1 % (22 %) leads to a slight reduction (enhancement) in
TEC magnitude at the northern (southern) crest.