Abstract
AbstractWe present all‐sky interferometric meteor radar (MR), VHF (36.9 MHz), observations from Sodankylä Geophysical Observatory and report on the unusual echoes, which were detected at low elevation on the northern horizon, typically during substorms. These echoes have a near‐zero Doppler shift, relatively low power, but with a sharp rise to the power peak, short lifetime (less than 2 s), and nonexponential decay (NED). We suggest that such auroral NED echoes are in fact ground backscatter of the MR waves which have been refracted in the ionosphere, passing through the ionosphere in the substorm region, where pulsating aurora (at a frequency higher than 1.7 Hz) occurs and causes quasiperiodic modulation of the wave propagation conditions, which leads to corresponding modulation of the amplitude of return. The MR treats such oscillating signal as meteor trails.
Highlights
Radars are commonly used to monitor the ionosphere and atmosphere, but they provide information on ionospheric structures and irregularities
Aiming to understand the nature of such unusual meteor radar (MR) echoes, we have checked non-‐ exponential decay (NED) detections throughout the whole data set of MR observations in Sodankylä Geophysical Observatory (SGO) from January 2009 to April 2014. The results of this search are described in the present paper. 71 First, we shortly describe the MR data and present typical cases when NED echoes were observed, together with simultaneous ionosonde and magnetometer data from SGO and the surrounding area
In the following we mostly focus on the non-‐exponentially decayed echoes, for which the standard analysis is not able to determine the decay time. 106 Figure 2 presents the numbers of NED echoes detected during each day from 107 January 2009 until April 2014
Summary
Radars are commonly used to monitor the ionosphere and atmosphere, but they provide information on ionospheric structures and irregularities. We present SKiYMET meteor radar (MR), VHF (36.9 MHz), observations from Sodankylä Geophysical Observatory, and report on the unusual echoes, which were detected at low elevation on the northern horizon, typically during substorms.
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