M.A. Sergeeva

Mexican Space Weather Service (SCIESMEX)

Legislative modifications of the General Civil Protection Law in Mexico in 2014 included specific references to space hazards and space weather phenomena. The legislation is consistent with United Nations promotion of international engagement and cooperation on space weather awareness, studies and monitoring. These internal and external conditions motivated the creation of a space weather service in Mexico. The Mexican Space Weather Service (SCiESMEX in Spanish) (www.sciesmex.unam.mx) was initiated in October 2014 and is operated by the Institute of Geophysics at the Universidad Nacional Autonoma de Mexico (UNAM). SCiESMEX became a Regional Warning Center of the International Space Environment Services (ISES) in June 2015. We present the characteristics of the service, some products and the initial actions for developing a space weather strategy in Mexico. The service operates a computing infrastructure including a web application, data repository and a high-performance computing server to run numerical models. SCiESMEX uses data of the ground-based instrumental network of the National Space Weather Laboratory (LANCE), covering solar radio burst emissions, solar wind and interplanetary disturbances (by interplanetary scintillation observations), geomagnetic measurements, and analysis of the total electron content (TEC) of the ionosphere (by employing data from local networks of GPS receiver stations).

Impact of magnetic storms on the global TEC distribution

The study is focused on the analysis of Total Electron Content (TEC) variations during six geomagnetic storms of 10 different intensity: from Dstmin = – 46 nT to Dstmin = -223 nT. The values of TEC deviations from its 27-day median value (δTEC) were calculated during the periods of the storms along three meridians: American, Euro-African and AsianAustralian. The following results were obtained. For the majority of the storms almost simultaneous occurrence of δTEC maximums was observed along all three meridians at the beginning of the storm. The transition from weak storm to superstorm (the increase of magnetic activity) almost does not affect the intensity of δTEC maximum. The seasonal effect 15 was most pronounced at Asian-Australian meridian, less often at Euro-African meridian and was not revealed at American meridian. Sometimes the seasonal effect can penetrate to the opposite hemisphere. The character of averaged δTEC variations for the intense storms was confirmed by GOES satellite data. Though there are some common features of TEC variation revealed during each storm phase, in general no clear dependence of TEC responses on the storm phases was found: the effects were different during each storm at different locations. The behaviour of correlation coefficient (R) 20 between δTEC at three meridians was analyzed for each storm. In general, R>0.5 between δTEC averaged along each meridian. This result is new. The possible reasons for the exceptions (when R < 0.5) were provided: time-shift of δTEC maximum at different latitudes along the American meridian, the complexity of phenomena during the intense storms and discordance in local time of geomagnetic storm beginning at different meridians. Notwithstanding the complex dependence of R on the intensity of magnetic disturbance, in general R decreased with the growth of storm intensity. 25

Estimates of ionosphere state over Mexico with TEC data

The ionosphere behaviour over Mexico was studied. We analysed variations of Total Electron Content (TEC) and critical frequency of F2-layer of the ionosphere (foF2). TEC values were extracted from data of local GNSS receivers and if missed then from global ionospheric maps. foF2 values were reconstructed using TEC measured over Mexico and equivalent slab thickness of the ionosphere measured in the adjacent to Mexico regions having ionosondes. Diurnal and seasonal patterns of TEC and foF2 behaviour over Mexico were revealed. The peculiarity of TEC behaviour during disturbances were studied. The presence of strong positive enhancements is a characteristic feature for Mexico that is confirmed by measurements of electron concentration at satellites CHAMP and DSMP.