Abstract
AbstractMeteor radar observations at the Sodankylä Geophysical Observatory (67° 22′N, 26° 38′E, Finland) indicate that the mesospheric temperature derived from meteor decay times is systematically underestimated by 20–50 K during the Geminids meteor shower which has peak on 13 December. A very good coincidence of the minimum of routinely calculated temperature and maximum of meteor flux (the number of meteors detected per day) was observed regularly on that day in December 2008–2014. These observations are for a specific height‐lifetime distribution of the Geminids meteor trails and indicate a larger percentage of overdense trails compared to that for sporadic meteors. A consequence of this is that the routine estimates of mesospheric temperature during the Geminids are in fact underestimates. The observations do, however, indicate unusual properties (e.g., mass, speed, or chemical composition) of the Geminids meteoroids. Similar properties were found also for Quadrantids in January 2009–2015, which like the Geminids has as a parent body an asteroid, but not for other meteor showers.
Highlights
Modern meteor radars (MR) are widely used to continuously monitor the mesospheric temperature and wind velocity
Meteor radar observations at the Sodankylä Geophysical Observatory (67° 22′N, 26° 38′E, Finland) indicate that the mesospheric temperature derived from meteor decay times is systematically underestimated by 20–50 K during the Geminids meteor shower which has peak on 13 December
Such a conclusion agrees with the results of Rapp et al [2012] who studied properties of meteor smoke particles (MSP) with data from three rocket flights on 4, 13, and 19 December 2010, which corresponded to the times before, during, and after the Geminids shower, respectively
Summary
Modern meteor radars (MR) are widely used to continuously monitor the mesospheric temperature and wind velocity. Thayer and Livingston [2008] found that the arctic mesosphere cooling in December 2000 was associated with stratosphere baroclinic zones, which was supported by multi-instrument temperature measurements from ground to mesosphere heights in Greenland Except these papers on the event from December 2000, we have not found in the literature other reports on such a regular yearly behavior of mesospheric temperature or peculiarity of atmospheric dynamics in December. This plot shows the mesosphere temperature values mostly within 190–200 K during the whole month. We calculated daily averaged temperature from the MR data obtained only for the 02–04 and 12–14 local time intervals to match to the Aura measurements These data (not shown here) demonstrated the same temperature drop that is manifested in Figure 2a for the daily MR data. We discuss the results in view of our knowledge of composition, physical properties, and origin of meteors
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