Simultaneous observations of Polar Mesosphere Summer/Winter Echoes with EISCAT and MST radars Evgenia Belova Swedish Institute of Space Physics, Kiruna, Sweden
PMSE / PMWE PMSE: 80-90 km, summer time, relation to NLCs. Generation due to presence of ice charged particles and neutral turbulence. Observed by radars in wide frequency range: HF- UHF PMWE: 55-80 km, beyond summer time, at VHF frequencies, presence of MSPs. Generation mechanism is unknown, turbulent with and without charged particles and infrasound wave mechanisms were suggested.
What can one learn from observations at different frequencies (scale lengths)? Echo strength. PSD Adapted from F.- J. Luebkin, 2004 3 m MST 67 cm EISCAT VHF Sc=ν/D»1 16 cm EISCAT UHF k Radar cross section per unit volume = Volume reflectivity [m -1 ]= Function (turbulence parameters (e.g.ε), dusty plasma parameters (Sc))
What can one learn from observations at different frequencies (scale lengths)? Spectral width. Spectral width ~ fluctuating (turbulent) velocity of scatterers ~ dissipative rate of turbulence. Spectral width is a local measure of turbulence. Spectral width for the echoes of a turbulent origin is the same for any radars, independent on frequency (radar wavelength). Comparison of spectral widths of the echoes at different frequencies is a test for turbulent origin of echoes provided common volume measurements.
Case study 1: PMWE in November 2004 2004 11 12 ESRAD EISCAT Belova et al., 2013
Case study 2: PMSE during the PHOCUS rocket campaign 21 July 2011 PHOCUS Particles, Hydrogen and Oxygen Chemistry in the Upper Summer mesosphere. The PHOCUS rocket was launched at 7 UT on 21 July 2011 into a strong mesospheric ice layer. Esrange lidar, NLC ESRAD radar, PMSE
Radars operating during PHOCUS MST radars ESRAD MORRO MAARSY MAARSY 250 km EISCAT VHF & UHF MORRO 150 km 200 km ESRAD Loca7on ESRANGE, ESRAD Sweden RamSord- moen, Norway Andenes, Norway Frequency 52 MHz 56 MHz 53.5 MHz Beam width Experiment /Analysis 4.4 5 3.6 Ver3cal beam, FCA due to spaced antennas Ver3cal beam Ver3cal beam EISCAT VHF (224 MHz) & UHF (933 MHz) radars ran manda experiments during 7-10 UT
PMSE with three MST radars PMSE strength PMSE spectral width Cross-correlation coefficients between time variations in PMSE strength for each pair of radars are up to 0.6. All three radars recorded the same waves (e.g. wave with 6-hour period) as shown by cross-spectrum analysis. Simultaneous values of PMSE spectral width were shown to be different for three radars, i.e. turbulence is produced locally. Belova et al, submitted to JASTP in 2013
Comparison of PMSE at 56 and 224 MHz EISCAT Log10 VR, m - 1 Preliminary results: different spectral widths due to different turbulence? different volumes? Beam broadening for MORRO?
Summary and outlook for EISCAT_3D Multi-frequency and multi-radar observations of mesospheric echoes were shown to be powerful method to study atmospheric turbulence and waves, dust particles and generation mechanism of echoes (e.g. Hoppe et al, 1990; Röttger et al., 1990; Belova et al, 2005; 2007; 2013; Rapp et al., 2008; Strelnikova and Rapp, 2010). With the high power, interferometric capabilities and common volume measurement possibilities of EISCAT_3D and other MST radars as MORRO or MAARSY, new combined studies become possible that will provide new insights in mesospheric turbulence, PMSE microphysics and scattering mechanisms. The high power of the EISCAT_3D system will allow detection of weaker echoes from the lower heights (50-70 km) and also derivation of PMWE spectral characteristics. This, together with horizontal velocity measurements making use of interferometric capabilities of EISCAT_3D, could help to distinguish between different generation mechanisms suggested for PMWE.
Swedish Application on EISCAT_3D to VR The specific scientific questions in mesospheric research that we will address using EISCAT_3D are: What is the three dimensional structure of the wave fields propagating to the mesosphere and lower thermosphere from below? How do they change as they move upwards? What is the three dimensional structure of turbulence within the thin mesospheric layers? What is the horizontal and vertical structure of the ice particle size and number density in PMSE layers (connected to noctilucent clouds), and how does this vary? How do PMWE form, and what determines when they appear and their properties? What is the horizontal and vertical structure of the dust size and number density of MSP in the mesosphere, and how does this vary?
Acknowledgements Henry Pinedo, University of Tromso, Norway Ralf Latteck, Marius Zecha, Leibniz-institute of Atmospheric Physics, Kuhlungsborn, Germany Ingemar Häggström, EISCAT Scientific Association, Kiruna, Sweden Sheila Kirkwood, Tima Sergienko, Swedish Institute of Space Physics, Kiruna, Sweden