Simultaneous optical and meteor head echo measurements using the Middle Atmosphere Alomar Radar System (MAARSY): Data collection and preliminary analysis

Abstract

Highlights• 105 optical meteors simultaneously detected as head echoes by MAARSY are analysed • Radiants measured by radar and optical show median differences of 1.5 degrees.• Optical calibration shows MAARSY detects meteoroids of masses 10 -9 kg -10 -10 kg • Clear trend of larger RCS for brighter meteors at higher heights and larger speeds • Many events show variations in RCS significantly different than optical light curve AbstractThe initial results of a two year simultaneous optical-radar meteor campaign are described.Analysis of 105 double-station optical meteors having plane of sky intersection angles greater than 5 degrees and trail lengths in excess of 2 km also detected by the Middle Atmosphere Alomar Radar System (MAARSY) as head echoes was performed. These events show a median deviation in radiants between radar and optical determinations of 1.5 degrees, with 1/3 of events having radiant agreement to less than one degree. MAARSY tends to record average speeds roughly 0.5 km/s and 1.3 km higher than optical records, in part due to the higher sensitivity of MAARSY as compared to the optical instruments.More than 98% of all head echoes are not detected with the optical system. Using this nondetection ratio and the known limiting sensitivity of the cameras, we estimate that the limiting meteoroid detection mass of MAARSY is in the 10 -9 kg to 10 -10 kg (astronomical limiting meteor magnitudes of +11 to +12) appropriate to speeds from 30-60 km/s. There is a clear trend of higher peak RCS for brighter meteors between 35 and -30 dBsm. For meteors with similar magnitudes, the MAARSY head echo radar cross-section is larger at higher speeds. Brighter meteors at fixed heights and similar speeds have consistently, on average, larger RCS values, in accordance with established scattering theory. However, our data show RCS ∝ v/2, much weaker than the normally assumed RCS ∝ v 3 , a consequence of our requiring head echoes to also be detectable optically. Most events show a smooth variation of RCS with height broadly following the light production behavior. A significant minority of meteors show large variations in RCS relative to the optical light curve over common height intervals, reflecting fragmentation or possibly differential ablation. No optically detected meteor occurring in the main radar beam and at times when the radar was collecting head echo data went unrecorded by MAARSY. Thus there does not appear to be any large scale bias in MAARSY head echo detections for the (comparatively) larger optical events in our dataset, even at very low speeds.

Studying a Long-Lasting Meteor Trail from Stereo Images and Radar Data

“…The study was performed for meteoroids with different chemical compositions and velocities. Similar research was performed in [4] using the MAARSY radar. In [5], the authors performed a multi-instrumental optical and radio study of non-underdense meteor trails, the ionization of which is significantly higher than the background level at the initial moment.…”

Contribution of meteor flux in the occurrence of sporadic-E (Es) layers over the Arabian Peninsula

“…Meteors can be categorized as being either part of a shower or of the back-ground meteor flux. There is a vast amount and variety of meteoroid material entering the atmosphere every day (Ceplecha et al, 1998), and its deposition is highly variable spatially as well as temporally. These variations are attributed to the inconsistency of the meteoroid material density surrounding the Earth, seasonal changes of the atmosphere and the Earth's movement around the Sun, the methods of observing them such as the geographical location of the observing site, and geometrical factors related to the observing instruments' capability and positions of sources.…”

“…This extraterrestrial influx changes the metallic composition of the Earth's atmosphere and lower ionosphere. This happens when meteors burn in the dense atmosphere, resulting in the heating and deposition of free metal atoms and ions (Ceplecha et al, 1998). It is now a well-established fact that the permanent ionized metal layer in the lower ionosphere, at around 90-130 km altitude, is due to the ablation of meteors in that region (Plane et al, 2015).…”

“…Detection using visual cameras can only be performed during the night compared to radio-based observations that can be performed throughout the day and suitable for estimating total meteor activity. A combination of multiple types of observations may also be used (Brown et al, 2017). Kopp (1997) showed that the thin-layered structured sporadic-E (Es) layer in the Earth's ionosphere, lying in the altitude range of 90-130 km, mostly consists of ionized metal atoms FeC, MgC, and NaC.…”

Contribution of Meteor Flux in the Occurrence of Sporadic-E over Arabian Peninsula

“…Detection using visual cameras can only be performed during night compared to radio-based observations which can be performed throughout the day and is 30 suitable for estimation of total meteor activity. A combination of multiple types of observations may also be used (Brown et al, 2017). Kopp, (1997) showed that the thin-layered structured sporadic-E layer (Es) in the Earth's ionosphere, lying between the altitude range of 90-130 km, is mostly consisted of ionized metal atoms FeC, MgC and NaC.…”