Equatorial temperature anomaly during solar minimum

• Published in: Journal of Geophysical Research. A. Space Physics 2001-11, Vol.106 (A11), p.24
• Main Authors: Suhasini, R, Raghavarao, R, Mayr, H G, Hoegy, W R, Wharton, L E
• Format: Article
• Language: English
• ISSN: 0148-0227

We show evidence for the occurrence of the equatorial temperature anomaly (ETA) during solar minimum by analyzing the temperature and total ion density data from the Neutral Atmosphere Temperature Experiment (NATE) and the Cylindrical Electrostatic Probe (CEP), respectively, on board the Atmospheric Explorer-E satellite. The chosen data refer to a height of about 254 km in the African and Asian longitude sector (340.1 deg E-200 deg E) during a summer season in the Southern Hemisphere. As during the solar maximum period, the spatial characteristics of the ETA are similar to those of the equatorial ionization anomaly (EIA). A minimum in the gas temperature is collocated with the minimum in the ion density at the dip equator, and a temperature maximum on the south side of the equator is collocated with the density maximum of the EIA. The daytime behavior of ETA formation is about the same as that of EIA as both of them are clearly present at around 1300 and 1400 local solar time (LST) only. At 1400 LST the difference between the temperatures at the crest and the trough (ETA strength) reaches a maximum value of about 100 K, which is about 14 percent of the temperature at the trough. Like the EIA, the ETA also suddenly disappears after 1400 LST. Thus the EIA appears to be a prerequisite for the ETA formation. (Author)