Survey of Magnetospheric Line Radiation Observed by a Low-Altitude Spacecraft

We present results of a large survey of observations of Magnetospheric Line Radiation (MLR) events. These are electromagnetic waves in the frequency range about 1 - 8 kHz that, when represented in a frequency-time spectrogram, have a form of several clearly seen lines, nearly equidistant in frequency and with a rather slow frequency drift. They have been observed both by satellites and ground-based instruments; however, their origin remains still unclear. We have used 3 years of electric field data measured by the DEMETER spacecraft (circular orbit with an altitude about 700 km) and a manual search for the presence of MLR events, resulting in a unique data set of more than 600 events. According to our knowledge, this is the largest satellite database of MLR events collected to date. The properties of MLR events (frequency range, time duration, dimension, etc.) have been thoroughly investigated. Moreover, it has been checked whether the occurrence rate of these events is larger above some specific (e. g. industrialized) areas. Finally, the most favorable geomagnetic conditions (characterized by Kp and Dst indices) for the occurrence of MLR events have been found.