The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes

Younger, P. T.; Astin, Ivan; Sandford, D. J.; Mitchell, N. J.

doi:10.5194/angeo-27-2831-2009

Cited by 40 publications

(38 citation statements)

References 18 publications

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“…The differences between the count rates recorded over Rothera and Esrange arises from differences in the levels of radio interference at the two sites, small differences in the performance of the radars and differences in the strengths of the visible sporadic meteor radiants. The annual cycle of count rates is a consequence of the visibility above the horizon of the astronomical sources of sporadic meteors (radiants) (e.g., Younger et al, 2009). Figure 2a and b presents the normalised diurnal variation of meteor counts in local time for Rothera and Esrange, respectively.…”

Section: Discussionmentioning

confidence: 99%

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Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

et al. 2010

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Abstract. Zonal and meridional winds have been measured in the upper mesosphere and lower thermosphere at polar latitudes using two ground-based meteor radars. One radar is located at Rothera (68 • S, 68 • W) in the Antarctic and has been operational since February 2005. The second radar is located at Esrange (68 • N, 21 • E) in the Arctic and has been operational since October 1999. Both radars have produced relatively continuous measurements. Here we consider measurements made up to the end of 2009. Both radars are of similar design and at conjugate geographical latitudes, making the results directly comparable and thus allowing investigation of the differences in the mean winds of the Antarctic and Arctic regions. The data from each radar have been used to construct climatologies of monthly-mean zonal and meridional winds at heights between 80 and 100 km. Both Antarctic and Arctic data sets reveal seasonally varying zonal and meridional winds in which the broad pattern repeats from year to year. In particular, the zonal winds display a strong shear in summer associated with the upper part of the westward summertime zonal jet. The winds generally reverse to eastward flow at heights of ∼90 km. The zonal winds are eastward throughout the rest of the year. The meridional winds are generally equatorward over both sites, although brief episodes of poleward flow are often evident near the equinoxes and during winter. The strongest equatorward flows occur at heights of ∼90 km during summer.There are significant differences between the mean winds observed in the Antarctic and Arctic. In particular, the westward winds in summer are stronger and occur earlier in the season in the Antarctic compared with the Arctic. The eastward winds evident above the summertime zonal wind reversal are significantly stronger in the Arctic. The summertime equatorward flow in the Antarctic is slightly weaker, but occurs over a greater depth than is the case in the Arctic.Correspondence to: D. J. Sandford (d.j.sandford@bath.ac.uk) Comparisons of these observations with those of the URAP and HWM-07 empirical models reveal a number of significant differences. In particular, the zonal winds observed in the Antarctic during wintertime are significantly weaker than those of URAP. However, the URAP zonal winds are a good match to the observations of the Arctic. Significant differences are evident between the observations and HWM-07. In particular, the strong wintertime zonal winds of the Arctic in HWM-07 are not evident in the observations and the summertime zonal winds in HWM-07 are systematically stronger than observed. The agreement with meridional winds is generally poor.There is a significant amount of inter-annual variability in the observed zonal and meridional winds. Particularly high variability is observed in the Arctic zonal winds in spring and is probably associated with stratospheric warmings.

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Section: Discussionmentioning

confidence: 99%

“…This behaviour is again a consequence of the visibility above the horizon of the astronomical sources of sporadic meteor radiants. A more detailed examination of these variations is presented in Younger et al (2009).…”

Section: Discussionmentioning

confidence: 99%

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

et al. 2010

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“…In the past there was no evidence that could show a strong seasonal dependence of meteor input. Younger et al (2009) used long-term VHF radar observations from high-latitude stations in both hemispheres along with a low-latitude station. They showed that the meteor counts peak around local summer at the high-latitude stations in both hemispheres, whereas the equatorial station shows a semi-annual variation with two peaks close to the local summer and winter.…”

Section: Discussionmentioning

confidence: 99%

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

et al. 2014

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Abstract.A thin and highly dense sporadic E layer, which can occasionally block the upper ionospheric layers, is called blanketing sporadic E (E sb ). We present the statistical seasonal local time occurrence pattern of E sb at equatorial station Tirunelveli (8.7 • N, 77.8 • E, dip latitude 0.7 • N) during the extended minimum of solar cycle 24 (2007-2009). In spite of nearly the same average solar activity during both 2007 and 2009, considerable differences are noticed in the seasonal occurrence of E sb during this period. The percentage of E sb occurrence is found to be the highest during the summer solstice (≥ 50 %) for both 2007 and 2009, which is in general accordance with the earlier studies. The occurrences of E sb during the vernal equinox (∼ 33 %) and January-February (∼ 28 %) are substantial in 2009 as compared to those during the same seasons in 2007. We find that, during winter (January-February), ∼ 75 % of E sb occurred during or just after the period of sudden stratospheric warming (SSW). We suggest that enhanced E sb occurrence during winter (January-February) and the vernal equinox of 2009 could be associated with SSW-driven changes in the E region ambient conditions. Furthermore, the close association of E sb with counter equatorial electrojet (CEEJ) suggested by earlier studies is re-examined carefully using the scenario of E sb occurrence on non-CEEJ days. Such an exercise is crucial as we are unaware whether the physical mechanisms driving E sb and CEEJ are linked or not. We find that, of all the seasons, the association of E sb and CEEJ is strongest during winter (November-December).

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“…As shown by e.g. Younger et al (2009);Stober et al (2012), the density can be as variable as 10-20 %. Fig.…”

Section: Geminid Velocity and Initial Altitudementioning

confidence: 99%

MU head echo observations of the 2010 Geminids: radiant, orbit, and meteor flux observing biases

2013

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Abstract. We report Geminid meteor head echo observations with the high-power large-aperture (HPLA) Shigaraki middle and upper atmosphere (MU) radar in Japan (34.85° N, 136.10° E). The MU radar observation campaign was conducted from 13 December 2010, 08:00 UTC to 15 December, 20:00 UTC and resulted in 48 h of radar data. A total of ~ 270 Geminids were observed among ~ 8800 meteor head echoes with precisely determined orbits. The Geminid head echo activity is consistent with an earlier peak than the visual Geminid activity determined by the International Meteor Organization (IMO). The observed flux of Geminids is a factor of ~ 3 lower than the previously reported flux of the 2009 Orionids measured with an identical MU~radar setup. We use the observed flux ratio to discuss the relation between the head echo mass–velocity selection effect, the mass distribution indices of meteor showers and the mass threshold of the MU radar.

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The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes

Cited by 40 publications

References 18 publications

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24

MU head echo observations of the 2010 Geminids: radiant, orbit, and meteor flux observing biases

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The sporadic radiant and distribution of meteors in the atmosphere as observed by VHF radar at Arctic, Antarctic and equatorial latitudes

Cited by 40 publications

References 18 publications

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Dynamics of the Antarctic and Arctic mesosphere and lower thermosphere – Part 1: Mean winds

Occurrence of blanketing E&lt;sub&gt;s&lt;/sub&gt; layer (E&lt;sub&gt;sb&lt;/sub&gt;) over the equatorial region during the peculiar minimum of solar cycle 24

MU head echo observations of the 2010 Geminids: radiant, orbit, and meteor flux observing biases

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Occurrence of blanketing E<sub>s</sub> layer (E<sub>sb</sub>) over the equatorial region during the peculiar minimum of solar cycle 24