Occurrence and Altitude of the Non-Specular Long-Lived Meteor Trails
During Meteor Showers at High Latitudes
Abstract
Meteoroids entering the Earth’s atmosphere produce ionized trails, which
are detectable by radio sounding. Cylindrical underdense (and partly
overdense) trails form a great majority of meteor echoes received by
meteor radars (MR). Additionally, the long-lived non-specular (LLNS)
meteor echoes are received from non-field-aligned irregularities of
ionization generated along tracks of relatively large meteoroids. The
occurrence and height distributions of LLNS are studied using MR
observations at Sodankylä Geophysical Observatory (SGO, 67° 22’ N, 26°
38’ E, Finland) during 2008-2019. Two parameters are analyzed: the
percentage and height distribution of LLNS echoes. These LLNS echoes
constitute about 2% of all MR detections. However during certain meteor
showers (Geminids, Perseids, Quadrantids, Arietids or/and Daytime
ζ-Perseids, and Lyrids) the percentage of LLNS echoes is noticeably
higher (about 6, 5, 4, 4, and 3%, respectively). Typically, the LLNSs
occur ∼2 km higher than other echoes (in June-July the height difference
is reduced to ∼1 km). Due to this elevation, a larger percentage of
LLNSs is manifested as an upward shift of the height distribution of
meteor trails during meteor showers. Moreover, during Lyrids,
η-Aquariids, Perseids, Orionids, and Leonids the LLNS echoes occur
noticeably, up to 3-6 km, higher than the echoes from other types of
trails. Thus, enhanced heights of meteor detections during major meteor
showers (Quadrantids, Lyrids, η-Aquariids, Arietids or/and Daytime
ζ-Perseids, Perseids, Orionids, Leonids, and Geminids) are predominantly
due to long-lived non-specular echoes from the non-field-aligned
irregularities associated with large meteoroids.