A Preliminary Analysis of the Shangri-La Bolide on 2017 Oct 4

At 12:07 UT (8:07 pm China Standard Time) on 2017 Oct 4, a bright bolide was widely observed in the Shangri-La region in the Province of Yunnan, China (Figure 1). The event was well observed by the general public as it took place on the night of the Mid Autumn Festival which associates with moon gazing. Sonic booms and ground shaking were reported in an area about a thousand square kilometers wide to the northwest of the Shangri-La City. Data from the U.S. government sensor suggested that the impact energy of the event is approximately 0.54 kt TNT equivalent, with the terminus of the bolide positioned at $28.1^\circ$ N, $99.4^\circ$ E. This is the largest observed bolide event overland since the bolide event took place in Mauritania on 2016 Jun 27 (1.2 kt). In this Research Note we present a preliminary analysis of this event.Comment: Earth and Planetary Physics in pres

Ozone Measurements with Meteors: A Revisit

Understanding the role of ozone in the Mesosphere/Lower Thermosphere (MLT) region is essential for understanding the atmospheric processes in the upper atmosphere. Earlier studies have shown that it is possible to use overdense meteor trails to measure ozone concentration in the meteor region. Here we revisit this topic by comparing a compilation of radar observations to satellite measurements. We observe a modest agreement between the values derived from these two methods, which confirm the usefulness of the meteor trail technique for measuring ozone content at certain heights in the MLT region. Future simultaneous measurements will help quantifying the performance of this technique.Comment: MNRAS in pres

Meteor showers from active asteroids and dormant comets in near-Earth space: a review

Small bodies in the solar system are conventionally classified into asteroids and comets. However, it is recently found that a small number of objects can exhibit properties of both asteroids and comets. Some are more consistent with asteroids despite episodic ejections and are labeled as "active asteroids", while some might be aging comets with depleting volatiles. Ejecta produced by active asteroids and/or dormant comets are potentially detectable as meteor showers at the Earth if they are in Earth-crossing orbits, allowing us to retrieve information about the historic activities of these objects. Meteor showers from small bodies with low and/or intermittent activities are usually weak, making shower confirmation and parent association challenging. We show that statistical tests are useful for identifying likely parent-shower pairs. Comprehensive analyses of physical and dynamical properties of meteor showers can lead to deepen understanding on the history of their parents. Meteor outbursts can trace to recent episodic ejections from the parents, and "orphan" showers may point to historic disintegration events. The flourish of NEO and meteor surveys during the past decade has produced a number of high-confidence parent-shower associations, most have not been studied in detail. More work is needed to understand the formation and evolution of these parent-shower pairs.Comment: PSS in pres