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Blogs > loveisamyth > loveisamyth, stars are forever


loveisamyth 68M
849 posts
5/27/2015 6:44 am

Last Read:
5/28/2015 6:09 am
RADAR ECHOES FROM THE NOCTILUCENT ZONE
Every summer since the late 1970s, radars probing Earth's upper atmosphere have detected strong echoes from altitudes between 80 km and 90 km. These altitudes comprise the "noctilucent zone," where water vapor crystallizes around meteor smoke to form icy noctilucent clouds (NLCs). The first NLCs of the 2015 northern summer season were spotted by NASA's AIM spacecraft on May 19th. The radar echoes have followed close behind.

Les Dean of the MST Radar Facility in Aberystwyth, Wales, reports: "We detected our first echoes of the summer season on May 26th."



Researchers call them "Polar Mesospheric Summer Echoes" or "PMSEs." They occur over the Arctic during the months of May through August, and over the Antarctic during the months of November through February. These are the same months that NLCs appear.

But do the radar echoes actually come from noctilucent clouds? "The association is controversial," notes Dean. A leading theory holds that the ice particles in noctilucent clouds are electrically charged, and this makes them good reflectors of HF radio waves. However, NLCs are not always visible when the radar echoes are observed and vice versa. So the connection is not clear-cut.

One thing is sure: the season for both NLCs and PMSEs has begun. Stay tuned for more echoes from the noctilucent zone.





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