Multiple-frequency investigations of radio wave absorption during the dawn-breakup phase of auroras

Abstract

frequ e ncy a nd multiple stati o n radi o wave absorption data from the auroral zone are used to inves tigate th e electron de nsi ty co nte nt in th e D region durin g a ce rtain type of absorption eve nts. The typ e is c harac te rized by s mooth variability and widespread geograp hi c exte nt; th e ap proxima te electron density profiles are derived and di sc ussed. Th e general features of the profiles were found co mpatibl e with th e ionizati on due to the hi gh e ne rgy e lectro ns a nd th e associa ted bre mss tra hlung xrays. Such eve nts are also discussed in relation to th e visual a uroral a nd mag netic reco rd s.