Investigation of mid-latitude electron density trough diptrace at ionospheric critical frequencies

Solar winds caused by solar flares affect the Earth?s magnetic field significantlyand this interaction can cause large and sudden changes in the electron density of theionosphere. Especially during geomagnetic active periods, mid-latitude electron densitychanges between the 30 and 70 degree invariant magnetic latitude create a negative effecton communication and navigation systems. Approximately 550 km height, the ambientelectron densities trough observed in magnetic mid-latitudes is called "mid-latitudeelectron density trough (MLEDT)?. Between the years of 1960-1972, in the number of lowearth-orbit (LEO) satellites was little. As a result of morphological studies by especiallyAriel 3 and Ariel 4 satellites continuous and a large number of electron density data havebeen made identification of qualitative of MLEDT and quantitative criteria have beendeveloped. In subsequent studies, a theoretical ?plasmapause? model compared with about550 km in the ionosphere has been observed MLEDT and MLEDT has been discovered asionospheric trace of ?magnetosferic plasmapause?.In this study, a possible trace of MLEDT?s tried to determine from ionosphericcritical frequencies. To do this, critical frequency values, were obtained from ionosondesof 30o-70o invariant magnetic latitudes of the northern hemisphere for every hour, wereused. The hourly foF2 values from the ionosondes were analyzed according to thestatistical method. These methods include a local time, seasons, different groups of p K andviiinvariant magnetic latitude. Data analysis was made magnetically "quiet" and "disturb"periods. Magnetic quality is defined by ?planetary 3h- Kp ?. In brief, K £ 2+ p and K > 2+ pis described quite and disturb period, respectively.While trough-like structures are detected in large part hours of night for K > 2+ pthese structures are observed only some local time for K £ 2+ p . This structure occurred innight hours more than day hours. Furthermore, increased value of p K was seen a strongereffect in which occurred trough-like structures in night hours. In case of magneticallyquite, these structures has been seen for night hours of all season. Between these periodsmore trough were observed the in March despite that less trough was observed inDecember. In case of magnetically disturb, these structures has been seen all night.Between these periods most trough were observed during March and December periods, atleast troughs were observed during June period.In particular for K > 2+ p state, Ariel 3 and Ariel 4 satellites is measured electrondensity data near the 550 km compared with, and foF2 data were shown the similar tovariations in different local times and seasons.KEYWORDS: Ionosphere, magnetosphere, electron density trough, critical frequency.