Coincident multi-point observations of the E- and F-region decametre-scale plasma waves at high latitudes

Presented is an extensive analysis of the E-region backscatter observed at magnetic latitudes 75 ◦ {80 ◦ N by the PolarDARN component of the Su- per Dual Auroral Radar Network (SuperDARN). The statistical occurrence characteristics of the short-range echoes reveal signicant differences from those of the auroral and sub-auroral SuperDARN radars. In particular, most backscatter is detected in the midnight sector in the closest range gates where the geometric magnetic aspect angles are in excess of 10 ◦ where no backscat- ter is normally expected. One explanation offered is that intense ionisation layers signicantly refract the radar waves allowing a regular detection of the backscatter from the nearest range gates. A statistical analysis of the spectral echo types within the PolarDARN dataset showed strong similar- ities with the auroral SuperDARN radars, despite signicant differences in the geometric aspect angle coverage. The low-velocity echoes dominated the datasets, while the high-velocity echoes were observed rather sporadically in the morning sector. The location of the PolarDARN radars relative to the more-equatorward SuperDARN radars facilitates the use of a new experi- mental setup that has coincident and simultaneous HF radar coverage of the E and F regions on the same magneticeld lines. Using this conguration, the SuperDARN plasma ow measurements are employed to investigate the

[1]  A. Koustov,et al.  On the relationship between the velocity of E-region HF echoes and E × B plasma drift , 2005 .

[2]  E. Nielsen,et al.  STARE velocities: 2. Evening westward electron flow , 2004 .

[3]  E. C. Thomas,et al.  Interferometric evidence for the observation of ground backscatter originating behind the CUTLASS coherent HF radars , 1997 .

[4]  A. Koustov,et al.  Simultaneous HF measurements of E- and F-region Doppler velocities at large flow angles. , 2004 .

[5]  R. Greenwald,et al.  HF radar observations of E region plasma irregularities produced by oblique electron streaming , 1987 .

[6]  D. Moorcroft.  An examination of radio-auroral aspect sensitivity , 1985 .

[7]  D. Moorcroft,et al.  Aspect angle variations in intensity, phase velocity, and altitude for high-latitude 34-cm E region irregularities , 1992 .

[8]  N. Nishitani,et al.  Upper mesosphere summer echoes detected with the Antarctic Syowa HF radar , 2002 .

[9]  J. Ruohoniemi,et al.  Climatological patterns of high-latitude convection in the Northern and Southern hemispheres: Dipole tilt dependencies and interhemispheric comparisons , 2010 .

[10]  Extraction of polar mesosphere summer echoes from SuperDARN data , 2005 .

[11]  R. Greenwald,et al.  Obliquely propagating ion acoustic waves in the auroral E region: Further evidence of irregularity production by field‐aligned electron streaming , 1990 .

[12]  P. Dyson,et al.  Aspect angle dependence of the E region irregularity velocity at large flow angles , 2007 .

[13]  B. Carter,et al.  On the diurnal variation of the E-region coherent HF echo occurrence , 2010 .

[14]  B. Carter,et al.  HF echo types revisited: aspect angle attenuation effects , 2009 .

[15]  D. T. Farley,et al.  Theory of plasma waves in the auroral E-region , 1984 .

[16]  R. Makarevich.  HF radar observations of high-velocity E-region echoes , 2008 .

[17]  J. M. Ruohoniemi,et al.  Large-scale imaging of high-latitude convection with Super Dual Auroral Radar Network HF radar observations , 1998 .

[18]  D. Moorcroft,et al.  New insights from a nonlocal generalization of the Farley-Buneman instability problem at high latitudes , 2002 .

[19]  T. Iyemori,et al.  Statistics of Antarctic mesospheric echoes observed with the SuperDARN Syowa Radar , 2004 .

[20]  R. Greenwald,et al.  Radar observations of auroral electrojet currents , 1975 .

[21]  A. Simon.  Instability of a Partially Ionized Plasma in Crossed Electric and Magnetic Fields , 1963 .

[22]  D. T. Farley,et al.  Three-wave coupling in the auroral E-region , 1995 .

[23]  F. Primdahl,et al.  Farley instability in the polar cap E region , 1975 .

[24]  G. Sofko,et al.  The SAPPHIRE‐North radar experiment: Observations of discrete and diffuse echoes , 1996 .

[25]  Steve E. Milan,et al.  Multi-frequency observations of E-region HF radar aurora , 2003 .

[26]  B. Carter,et al.  E-region decameter-scale plasma waves observed by the dual TIGER HF radars , 2009 .

[27]  S. Nozawa,et al.  STARE velocities: the importance of off-orthogonality and ion motions , 2003 .

[28]  B. Fejer,et al.  Correction [to “Ionospheric irregularities”] , 1981 .

[29]  D. André,et al.  Observations of 50- and 12-MHz auroral coherent echoes at the Antarctic Syowa station , 2001 .

[30]  C. Hanuise.  High‐latitude ionospheric irregularities: A review of recent radar results , 1983 .

[31]  I. B. Iversen,et al.  Further evidence for the Farley-Buneman instability in the polar cap ionosphere , 1975 .

[32]  C. Hanuise,et al.  Ionospheric refraction effects in slant range profiles of auroral HF coherent echoes , 1994 .

[33]  M. Lester,et al.  Finland HF and Esrange MST radar observations of polar mesosphere summer echoes , 2003 .

[34]  I. F. Grant,et al.  Comparison of plasma flow velocities determined by the ionosonde Doppler drift technique, SuperDARN radars, and patch motion , 1995 .

[35]  A. Koustov,et al.  A study of aspect angle effects in the E‐region irregularity velocity using multi‐point electric field measurements , 2006 .

[36]  John D. Sahr,et al.  Auroral electrojet plasma irregularity theory and experiment: A critical review of present understanding and future directions , 1996 .

[37]  Raymond A. Greenwald,et al.  Dependencies of high-latitude plasma convection: Consideration of interplanetary magnetic field, seasonal, and universal time factors in statistical patterns , 2005 .

[38]  Nils Olsen,et al.  The 10th generation international geomagnetic reference field , 2005 .

[39]  Mark Lester,et al.  A classification of spectral populations observed in HF radar backscatter from the E region auroral electrojets , 2001 .

[40]  T. Pulkkinen,et al.  CUTLASS HF radar observations of high-velocity E-region echoes , 2001 .

[41]  G. Sofko,et al.  Mapping ionospheric backscatter measured by the SuperDARN HF radars - Part 1: A new empirical virtual height model , 2008 .

[42]  Bodo W. Reinisch,et al.  International Reference Ionosphere 2000 , 2001 .

[43]  E. Nielsen,et al.  Coherent radar Doppler measurements and their relationship to the ionospheric electron drift velocity , 1985 .

[44]  M. Lester,et al.  Velocities of auroral coherent echoes at 12 and 144 MHz , 2002 .

[45]  G. Sofko,et al.  Three‐way validation of the Rankin Inlet PolarDARN radar velocity measurements , 2009 .

[46]  Mark Lester,et al.  On the altitude dependence of the spectral characteristics of decametre-wavelength E region backscatter and the relationship with optical auroral forms , 2001 .

[47]  N. Nishitani,et al.  Comparison of flow angle variations of E-region echo characteristics at VHF and HF , 2002 .

[48]  S. Nozawa,et al.  Arctic and Antarctic polar mesosphere summer echoes observed with oblique incidence HF radars: analysis using simultaneous MF and VHF radar data , 2004 .

[49]  G. Sofko,et al.  Relationship of the SAPPHIRE‐North merged velocity and the plasma convection velocity derived from simultaneous SuperDARN radar measurements , 1997 .

[50]  Mark Lester,et al.  Simultaneous observations at different altitudes of ionospheric backscatter in the eastward electrojet , 1997 .

[51]  D. Moorcroft.  A statistical study of UHF auroral backscatter at large magnetic aspect angle: A reanalysis of unpublished results from 1968 , 1996 .

[52]  I. McCrea,et al.  A first comparison of irregularity and ion drift velocity measurements in the E-region , 2006 .

[53]  M. Lester,et al.  HF radar observations of high-aspect angle backscatter from the E-region , 2004 .

[54]  Erling Nielsen,et al.  A first comparison of STARE and EISCAT electron drift velocity measurements , 1983 .

[55]  I. McCrea,et al.  Doppler spectrum statistics obtained from three different-frequency radar auroral experiments , 1995 .

[56]  Peter. Dyson,et al.  A decade of the Super Dual Auroral Radar Network (SuperDARN): scientific achievements, new techniques and future directions , 2007 .

[57]  P. Perreault,et al.  Azimuthal distribution of HF slant E echoes and its relationship to the polar cap electric field , 1976 .

[58]  R. Makarevich.  On the occurrence of high‐velocity E‐region echoes in SuperDARN observations , 2010 .