Hokkaido HF radar signatures of periodically reoccurring nighttime medium‐scale traveling ionospheric disturbances detected at short ranges

Abstract

The Super Dual Auroral Radar Network Hokkaido HF radar often detects periodically reoccurring E region echoing regions propagating toward or away from it. In this work, we consider 117 of such events identified for [2008][2009][2010][2011][2012]. These are shown to occur at nighttime, preferentially during summer, although significant number for events was found for winter. Statistics for the local time of occurrence, magnitude of the speed and polarity of progressions, and temporal and spatial periodicities are presented. We show that the power of echoes is linearly related to their Doppler velocity which makes it possible to identify the events on both power and Doppler velocity plots. Other peculiar characteristics of echoes are discussed. The onset of events is associated with gravity waves propagation through the radar field of view.

Review of the accomplishments of mid-latitude Super Dual Auroral Radar Network (SuperDARN) HF radars

“…Several additional arguments supporting the notion of strong electrical coupling between the E and F regions during MSTID events have been identified. These include (1) F region echo velocity is consistent with the expected electric field direction within regions of depleted/enhanced electron density ), (2) E region plasma velocity is comparable to that in the F region (Koustov et al 2014), (3) polarity of the E region velocity changes consistently in neighboring regions with enhanced/depleted plasma density ), and (4) the power of E region echoes correlates with the measured Doppler velocity (Koustov et al 2014). However, there are also several outstanding issues, including (1) sometimes, the region of depleted plasma correlates with a sheared plasma flow of opposite polarities, instead of a single direction ) and (2) polarity of the velocity is inconsistent with that usually observed for MSTIDs over Japan with the middle and upper atmosphere (MU) VHF radar (although at quite different MLAT).…”

“…Ogawa et al (2009) suggested such a coincidence is indicative of electrodynamic coupling between these two regions in the form of a polarization electric field (Perkins 1973) which maps into the E region without attenuation, as envisioned theoretically (e.g., Yokoyama and Hysell 2010). Koustov et al (2014) performed a more comprehensive analysis of E region MSTID signatures in HOK echoes and reported preferential occurrence of such echoes in summer with a secondary maximum in winter. This tendency is despite the fact that E region nighttime HOK echoes are more frequent in winter (Yakymenko et al 2015).…”

“…So far, however, this expectation has not been fully articulated. Oinats et al (2016a) found increased amplitude of MSTIDs with AE magnetic index in all LT sectors but individual events studied by Shiokawa et al (2008) and Koustov et al (2009Koustov et al ( , 2014 were during geomagnetically quiet conditions. Only one of the events considered by Ogawa et al (2009) can be related to geomagnetic disturbances at high latitudes while two others occurred under very quiet conditions, according to the Kp and AE indices.…”

“…The alternating polarization fields, through E × B drifts, cause variations in the Doppler shifts with opposite signs for the enhanced/depleted echo power, which also vary due to modulation of the GDI. Koustov et al (2014) made a statistical study of the HF radar signatures of nighttime MSTIDs at near ranges corresponding to E region backscatter. They found a reversal in the sense of propagation through midnight from southward-southwestward (toward the radar) to northward-northeastward (away from the radar).…”

Statistical characteristics of medium-scale traveling ionospheric disturbances revealed from the Hokkaido East and Ekaterinburg HF radar data

“…These two directions look very similar to the corresponding Hok-F directions, but they are observed slightly later or earlier accordingly. The possibility of the southwestward or northwestward MSTIDs in the E region was reported by Koustov et al (2013), who had also used the Hokkaido radar data in their study. The southeast daytime peak is significantly weaker for Hok-E as compared to Hok-F (see azimuths~120°at~12 LT in Fig.…”