Spaced transmitter measurements of medium scale traveling ionospheric disturbances near the equator

Abstract

The motion of Medium Scale Traveling Ionospheric Disturbances (MSTIDs) was measured for 1 year from the eastern tip of Brazil, about 10° degrees south of the magnetic and geographic equators using spaced fixed frequency radio transmitters. The motion was very similar during all of the year. The daytime average direction was towards 150° azimuth (clockwise from north) and speed was typically in the range 150–300 m/s. The azimuth varied only slightly during the day being slightly more easterly during evening‐morning hours. During winter months there were also some TIDs whose motion was northward. None of the known sources for MSTIDs fits well with MSTIDs having these velocity patterns. A possible unconfirmed source is the Inter‐Tropical Convergence Zone (ITCZ).

Observation of TEC perturbation associated with medium‐scale traveling ionospheric disturbance and possible seeding mechanism of atmospheric gravity wave at a Brazilian sector

“…Periods and wavelengths of these ΔTEC disturbances are in same range as those of the MSTIDs, and therefore, they can be classified as the MSTIDs. These properties are in close agreement with past literatures on MSTIDs [ Hernandez‐Pajares et al ., , ; Tsugawa et al ., ; Otsuka et al ., , ; Kotake et al ., , MacDougall and Jayachandran , ]. Taking Hernandez‐Pajares et al .…”

“…[, ] are during winter‐fall daytime and spring‐summer nighttime, but there were no major reports of MSTIDs occurrence during summer daytime for a complete solar cycle. MacDougall and Jayachandran [] using N m F 2 from Southern Hemisphere shows daytime MSTIDs during summer and explain that daytime MSTIDs during summer should be expected since the AGW activity causing most daytime MSTIDs are approximately equal for both day and night.…”

“…We further adopt a methodology dealing with the cross‐correlation maps that enable us to identify the MSTIDs from the derived TEC disturbances. Our results have been compared with relevant literatures over Southern Hemisphere [ Hernandez‐Pajares et al ., , ] using perturbed GPS‐TEC at one New Zealand sector (43.8°S–43.3°S and 169.5°E–170.5°E) and MacDougall and Jayachandran [] using digisonde data over the Brazilian equatorial region and they show good agreement.…”

“…While there have been few studies of daytime MSTIDs using the GNSS receiver network [e.g., Hernandez‐Pajares et al ., , ; MacDougall and Jayachandran , ; Grocott et al ., ], most of the studies over Southern Hemisphere (e.g., Brazil) have been limited to the nighttime MSTIDs observed using the all‐sky imagers [ Pimenta et al ., ; Candido et al ., ; Amorim et al ., ]. Unlike Northern Hemisphere, over most parts of the Southern Hemisphere, the detailed features of daytime MSTIDs are not reported mainly due to the limited spatial resolution of the GNSS network.…”

Medium-scale traveling ionospheric disturbances over Taiwan observed with HF Doppler sounding

“…GWs have been reported as caused by meteorological processes in the troposphere, such as the jet stream (Bertin et al 1978;Waldock and Jones 1987;Wautelet and Warnant 2015), vortexes (Wan et al 1998), typhoons (Huang et al 1985), or convective systems (Lay et al 2015;MacDougall et al 2011). The propagation of GWs from the troposphere to the thermosphere may be indirect.…”