Statistical and fragmentation properties of the micrometeoroid flux observed at Arecibo

Abstract

The micrometeor observations performed using the 430 MHz Arecibo Observatory radar have proven to be crucial for the understanding of meteoric effects on the aeronomy of the upper atmosphere. Meteors observed during the February 2001, 2006, and 2007 campaigns have been analyzed with a fast Fourier transform periodic search algorithm that automatically and uniformly detects meteor events between altitudes of 80 and 142 km. We present a description of the new technique used to detect meteors as well as the meteoroid parameters: altitude profiles, radial speeds, and decelerations. We also note the expected correlation between the radar transmitted power and the observed meteor event rate. The large number of events has enabled us to statistically estimate the average mass density of the observed population indicating that our detected events are generally cometary (1 g/cm3) and not asteroidal (3 g/cm3) in origin. Additionally, many meteor events are observed in which the radar meteor disappears from one radar pulse to the next (i.e., in 1 ms). We interpret this as indicative of the catastrophic destruction of the meteoroid. Until destruction, these events appear to undergo only minor ablation of their volatile components over the observed trajectory. As with a major fraction of all events recorded, the meteoroids that disappear in a terminal event show linear decelerations before their abrupt disappearance. This apparently low ablative mass deposition process may play an important role in the composition (aeronomy) of the upper atmosphere, as it likely produces submicron‐sized particles rather than the atom level products of ablation. First results on the altitude, speed, and mass distributions of terminal event meteoroids are given yielding some clues on the physics of the terminal event. Finally, the statistics of those events that yield no deceleration are compared statistically with those that exhibit deceleration with the conclusion that both groups are statistically the same. We further conclude that along with low signal‐to‐noise ratio and short echo duration, fragmentation of this group of particles is a primary cause of the inability to determine deceleration.

Simultaneous optical and radar measurements of meteors using the Poker Flat Incoherent Scatter Radar

“…One advantage of this method is a reduction in processing time because the FFT only needs to be computed for the output of the algorithm, a much reduced amount of data. In addition, several other sophisticated and robust searching algorithms are described in the literature, including Mathews et al (2003) and Briczinski et al (2009).…”

Comparison of sporadic sodium layer characteristics observed at different time resolutions

“…On the other hand, massive meteor trails have been observed by various radars (Briczinski et al, 2009;Ceplecha et al, 1998;Dyrud et al, 2011;Janches et al, 2001;Sugar et al, 2010;Zeng and Yi, 2011;Zhou and Perillat, 1998). Furthermore, there is some experimental evidence for a correlation between Na s and Es layer occurrence and meteor rates (Batista et al, 1989;Dou et al, 2010;Hansen and von Zahn, 1990;Hoeffner and Friedman, 2005;Höffner and Friedman, 2004), combined with the similar quasi-periodic oscillation and spatially localized scattering regions in Na s , Es and meteor trails, so that a possible role of meteor deposition in the formation of Na s layers should not be discarded.…”

“…In this respect it should be noted that the metallic atoms detected were potassium and calcium, and these two metallic atoms have far lower abundances than those of sodium and iron in the meteor ablation region. Alternatively, the duration of these trails might be too short, on the order of milliseconds, to be detected by a lidar with a relative low repetition rate (Briczinski et al, 2009;Dyrud et al, 2011;Pfrommer et al, 2009). Only those metallic atomic trails strong enough and lasting long enough relative to the lidar would be discerned easily.…”

The 2011 Draconids Meteor Light Curves and Meteoroid Fragmentation

“…Kero et al (2008) report three types of light curves-a smooth light curve event which simply outlines the antenna beam pattern and a ''beat pattern'' light curve event, shown to be consistent with two slowly separating particles, while yet more complex third type, found to be consistent with three or more fragments and/or continuous fragmentation. Briczinski et al (2009) and Sugar et al (2010) discuss the radar meteor head echo ''terminal events'' that are substantial through the meteor lifetime and then suddenly disappears below the noise level. Mathews et al (2010) reported many previously unaccounted features in the radar meteor return that are consistent with meteoroid fragmentation including ''terminal flare'' events.…”