Logo
ScienceStack
Table of Contents
Fetching ...
Sign In

Seasonal asymmetry in vertical distribution of meteor decay time at two conjugate polar latitudes

Chenna Reddy Kammadhanam

TL;DR

Problem: how the vertical distributions of meteor occurrence height and meteor decay time height vary seasonally at conjugate polar latitudes. Approach: analysis of long-term SKiYMET radar data from Esrange (68°N) and Rothera (68°S), with echoes split into weak and strong by received power to build seasonal mean profiles for meteor height and decay time in the 85–95 km range. Key findings: occurrence-height profiles are seasonally symmetric between hemispheres with about a 1 km difference between weak and strong echoes; decay-time turning altitude is seasonal (80–86 km) and shows opposite hemispheric maxima (Northern winter at Esrange, Southern summer at Rothera); strong echoes have higher turning altitudes than weak echoes, and hemispheric asymmetry in turning altitude arises from background MLT conditions and ion chemistry. Significance: results improve interpretation of meteor trail diffusion/recombination processes, support temperature inference from decay-time gradients, and highlight the role of hemispheric differences in mesospheric dynamics.

Abstract

The meteor occurrence height and decay time height are strongly dependent on local atmospheric conditions in the mesosphere and lower thermosphere (MLT)-region. In this study, we comparatively examine the seasonal behaviour of vertical distribution of meteor occurrence height and decay time height at two identical radars of conjugate polar latitudes, Esrange (68$^\circ$N) and Rothera (68$^\circ$S). In order to understand the nature of meteor trail variations, the received signal power is categorised into two groups as weak and strong echoes, and their seasonal mean vertical profiles are constructed. It has been noticed that the meteor occurrence height shown a seasonal symmetry, however, decay time vertical profiles shows an asymmetric pattern at conjugate polar latitudes, particularly for strong echoes. Seasonally, there is about 1 km difference in occurrence height and decay time height of weak and strong echoes. From the decay time vertical profiles, it has been noticed that the decay time turning altitude (i.e., inflection point) varies seasonally in the altitudes range of 80-86 km for weak and strong echoes. The maximum turning altitude of about 85 km is observed in Northern winter at Esrange (68$^\circ$N) and in Southern summer at Rothera (68$^\circ$S), similarly minimum turning altitude of about 80 km is observed in Northern winter at Esrange (68$^\circ$N) and in Southern summer at Rothera (68$^\circ$S). The probable reasons for such behaviour of meteor trails at opposite polar latitudes are discussed.

Seasonal asymmetry in vertical distribution of meteor decay time at two conjugate polar latitudes

TL;DR

Problem: how the vertical distributions of meteor occurrence height and meteor decay time height vary seasonally at conjugate polar latitudes. Approach: analysis of long-term SKiYMET radar data from Esrange (68°N) and Rothera (68°S), with echoes split into weak and strong by received power to build seasonal mean profiles for meteor height and decay time in the 85–95 km range. Key findings: occurrence-height profiles are seasonally symmetric between hemispheres with about a 1 km difference between weak and strong echoes; decay-time turning altitude is seasonal (80–86 km) and shows opposite hemispheric maxima (Northern winter at Esrange, Southern summer at Rothera); strong echoes have higher turning altitudes than weak echoes, and hemispheric asymmetry in turning altitude arises from background MLT conditions and ion chemistry. Significance: results improve interpretation of meteor trail diffusion/recombination processes, support temperature inference from decay-time gradients, and highlight the role of hemispheric differences in mesospheric dynamics.

Abstract

The meteor occurrence height and decay time height are strongly dependent on local atmospheric conditions in the mesosphere and lower thermosphere (MLT)-region. In this study, we comparatively examine the seasonal behaviour of vertical distribution of meteor occurrence height and decay time height at two identical radars of conjugate polar latitudes, Esrange (68N) and Rothera (68S). In order to understand the nature of meteor trail variations, the received signal power is categorised into two groups as weak and strong echoes, and their seasonal mean vertical profiles are constructed. It has been noticed that the meteor occurrence height shown a seasonal symmetry, however, decay time vertical profiles shows an asymmetric pattern at conjugate polar latitudes, particularly for strong echoes. Seasonally, there is about 1 km difference in occurrence height and decay time height of weak and strong echoes. From the decay time vertical profiles, it has been noticed that the decay time turning altitude (i.e., inflection point) varies seasonally in the altitudes range of 80-86 km for weak and strong echoes. The maximum turning altitude of about 85 km is observed in Northern winter at Esrange (68N) and in Southern summer at Rothera (68S), similarly minimum turning altitude of about 80 km is observed in Northern winter at Esrange (68N) and in Southern summer at Rothera (68S). The probable reasons for such behaviour of meteor trails at opposite polar latitudes are discussed.

Paper Structure

This paper contains 4 sections, 5 figures, 1 table.

Table of Contents

  1. Introduction
  2. Radar System and Data Analysis
  3. Results and Discussion
  4. Conclusions

Figures (5)

  • Figure 1: The 15 year composite mean meteor count at Esrange (68$^\circ$N) and Rothera (68$^\circ$S) (i.e., average number of meteors detected per day) during 2005 - 2019. Black line in left side figures represent the yearly mean and in right side figure represents the 21-day moving mean in each case.
  • Figure 2: The 15-year composite mean of the median (M) and upper quartile (Uq) & lower quartile (Lq) of meteor trail ionisation heights and their corresponding residual plots at Esrange (68$^\circ$N) and Rothera (68$^\circ$S) during 2005 - 2019. Black line in upper two panels represent the 21-day moving mean. The peaks in corresponding residual plots are marked as major shower days.
  • Figure 3: The 15-year composite mean of seasonal distribution of meteor occurrence height (km) for weak (--- blue line) and strong (--- red line) echoes at Esrange (68$^\circ$N) and Rothera (68$^\circ$S) during the period 2005 - 2019. Each data point represents the seasonal mean for each height bin and the error bars denote the corresponding standard deviation values.
  • Figure 4: The vertical profiles of 15-year composite mean meteor decay time for weak (--- blue line) and strong (--- red line) echoes at Esrange (68$^\circ$N) and Rothera (68$^\circ$S) during the period 2005 - 2019. Each data point represents the seasonal mean of decay time and the error bars denote the corresponding standard deviation values. The data used in this study are confined to the altitude range between 85 and 95 km, as marked by bold horizontal dashed lines. For better visualisation, the turning altitudes in each case are marked with filled circles.
  • Figure 5: The seasonal representation of decay time for both weak (left figure) and strong (right figure) echoes at Esrange (68$^\circ$N) (--- blue line) and Rothera (68$^\circ$S)(--- red line). The data from Rothera are presented with a shift of six months to allow an easy comparison of seasonal variation at opposite hemispheres.