Multi-instrument observations of atmospheric gravity waves/traveling ionospheric disturbances associated with enhanced auroral activity Zama Katamzi-Joseph * , Anasuya Aruliah, Kjellmar Oksavik, John Bosco Habarulema, Kirsti Kauristie, and Michael Kosch * South African National Space Agency, Hermanus, South Africa. Dept. Physics & Electronics, Rhodes University, Grahamstown, South Africa. 4 th International ANGWIN Workshop, Brazil, 24-26 April 2018
Atmospheric Gravity Waves/Traveling Ionospheric Disturbances (AGWs/TIDs) • Traveling ionospheric disturbances manifestation of atmospheric gravity waves in the ionosphere • appear as wave-like perturbations in measurements, e.g. TEC • Classified into 2 main categories based on period, and horizontal speed or wavelength: – Medium scale: periods 15-60 minutes, horizontal speeds 100-250 m/s and wavelength <100 – 400 km. Mostly associated with meteorological events (Mayr et al., 1984; Hernàndez-Parajes et al., 2006). – Large scale: periods > 30 minutes, horizontal speeds > 400 m/s and wavelength > 1000 km. Typically associated with disturbed geomagnetic conditions (Ding et al, 2006). • Aim: determine characteristics and source of AGWs/TIDs observed in GNSS and FPI measurements during night of 6 January 2014
Data • GNSS receivers (University of Bergen, Norway): GPS total electron content (TEC), 60 s cadence, • FPI (University College London): 630 nm intensity, emission height 240 km, 30° elevation angle, 9 minutes cadence • All sky camera (Finnish Meteorological Institute): 557.7 nm intensity, emission height 110 km, 1 minute cadence • Magnetometers (IMAGE): Horizontal X component, 1 minute cadence
Method: SADM-GPS • Velocities obtained from Statistical Angle of Arrival and Doppler method for GPS radio interferometry by Afraimovich et al. (1998). – Also used by Valladares and Hei (2012) and Habarulema et al. (2013) • Assume TID is plane sinusoidal traveling wave: 𝐽 𝑦, 𝑧, 𝑢 = 𝐵 sin(Ω𝑢 − 𝑙 𝑦 𝑦 − 𝑙 𝑧 𝑧 + 𝜒 0 ) x and y components TEC of wave number k TID amplitude Initial disturbance phase Angular disturbance frequency ′ = 𝑧 𝐿𝐼𝑃 𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 − 𝐸𝑈𝐹𝐷 𝐶𝐾𝑂 − 𝑧 𝐶𝐾𝑂 (𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 − 𝐸𝑈𝐹𝐷 𝐿𝐼𝑃 ) 𝐽 𝑦 𝑦 𝐿𝐼𝑃 𝑧 𝐶𝐾𝑂 − 𝑦 𝐶𝐾𝑂 𝑧 𝐿𝐼𝑃 𝑦 𝐶𝐾𝑂 𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 −𝐸𝑈𝐹𝐷 𝐿𝐼𝑃 − 𝑦 𝐿𝐼𝑃 (𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 −𝐸𝑈𝐹𝐷 𝐶𝐾𝑂 ) ′ = 𝐽 𝑧 𝑦 𝐿𝐼𝑃 𝑧 𝐶𝐾𝑂 − 𝑦 𝐶𝐾𝑂 𝑧 𝐿𝐼𝑃 • I’ x and I’ y are functions of t
Method: SADM-GPS • Azimuthal propagation direction of phase wavefront: ′ (𝑢) = tan −1 𝑣 𝑧 (𝑢) = tan −1 𝐽 𝑧 𝛽 𝑢 ′ (𝑢) 𝑣 𝑦 (𝑢) 𝐽 𝑦 • Horizontal phase velocity 𝑤 ℎ 𝑢 = 𝑣 𝑢 + 𝑥 𝑦 𝑢 sin 𝛽 𝑢 + 𝑥 𝑧 𝑢 cos(𝛽(𝑢)) 𝑣 𝑢 = ห𝑣 𝑦 (𝑢) 𝑣 𝑧 (𝑢) ห 𝑣 𝑦2 + 𝑣 𝑧2 ′ (𝑢) ′ (𝑢) 𝑣 𝑦 𝑢 = 𝐽 𝑢 𝑣 𝑧 𝑢 = 𝐽 𝑢 𝑏𝑜𝑒 ′ ′ 𝐽 𝑦 𝐽 𝑧 ′ = 𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 𝑢 + 𝑒𝑢 − 𝐸𝑈𝐹𝐷 𝐼𝑃𝑄 𝐽 𝑢 𝑒𝑢 𝑥 𝑦 = 𝑦 𝐽𝑄𝑄 𝑢 + 𝑒𝑢 − 𝑦 𝐽𝑄𝑄 (𝑢) 𝑥 𝑧 = 𝑧 𝐽𝑄𝑄 𝑢 + 𝑒𝑢 − 𝑧 𝐽𝑄𝑄 (𝑢) and 𝑒𝑢 𝑒𝑢
TEC Results • TEC shows wave-like perturbations between 17 and 23 UT on 6 Jan 2014 Approximate diurnal trend by 4 th order polynomial and remove to get TEC • perturbations, and therefore determine characteristics of wavelike perturbations (e.g. periods, velocities)
TEC Results A B C D • Periods: normalised Lomb-Scargle least squares frequency analysis; 99.99% confidence level • PRN 3 – A: 29 minutes (KHO) – B: 32 minutes (BJN) – C: 37 minutes (HOP+KHO) – D: 58 minutes (BJN + HOP) • PRN 11: 39 minutes (BJN+KHO)
TEC Results • PRN 3: <Vh> = 760 ± 235 m/s < α > = 347˚ ± 19˚ (east of north) poleward propagation • PRN 11: <Vh> = 749 ± 267 m/s α = 345˚ ± 20˚ (east of north) poleward propagation
FPI Results p = 128 min • Periodic enhancements in SE and SW between 15 and 02 UT • Periodogram for data between 15 and 21 UT – Period (ZEN and SW) = 128 minutes (2.1 hours) – Period (SE) = 174 minutes (2.9 hours) • Not enough information at different directions to determine propagation information
Polar Magnetic Indices • Kp max: 1 and min Dst: - 10 nT quiet storm conditions • Auroral geomagnetic disturbance observed, especially around 18UT – AE max ~200 nT – PCN max ~1.5 mV/m Minor substorm conditions
All sky Camera Results • ASC keogram: intensity brightening at ~18 UT associated with aurora activity coincides with AGWs/TIDs observations • Intensities extracted at specific latitudes corresponding to GPS receivers shows shift in intensities peaks – Poleward propagation, virtual horizontal velocity ~823 ± 143 m/s
ASC Results • Periodogram shows periods of 41 minute and 49 minutes
Magnetometer Results * • X-components obtained from SuperMAG shows disturbance around 18 UT – Baseline: yearly trend • Periodogram obtained using data shows period of 53 minutes for BJN and HOP stations * Ignored since greater than half the data length • Horizontal speed and azimuth (used altered SADM-GPS): 708 ± 261 m/s, 2˚ ±29 ˚ east of north
Discussion • Correlation of AGWs/TIDs characteristics from instruments sampling ionosphere/thermosphere at different heights – TEC calculated assuming thin shell at 300km: period 29-58 minutes, velocity 749- 760 m/s poleward; – Intensities of 557.7 nm emission assumed height at 110 km: periods 41-49 minutes, velocity 823 m/s poleward; – X-magnetic field deflection infers about ionospheric currents at also ~ 110 km: period 53 minutes, velocity 708 m/s poleward. • The AGWs/TIDs similar characteristics as those of large-scale TID class. • Characteristics comparable to other high latitudes studies, e.g. – Nicolls et al. (2012): 32.7±0.3 min, 560±270 m/s, 33.5±15.8° (Alaska) – Momani et al. (2010): 800-1200 m/s poleward propagation (Antarctica) • Observations of similar velocities at various heights also observed by Shiokawa et al. (2003): – Obtained 640 m/s from all sky imager, 379-560 m/s from GPS and 580 m/s from ionosondes
Summary + Conclusion • Presented AGWs/TIDs observed with measurements from radio, optical and magnetic field over Svalbard on a quiet geomagnetic night of 6 January 2014 – Properties match large scale TID characteristics • At same time substorm and auroral disturbances of similar periods and velocities observed from magnetometers and all-sky camera data. AGWs/TIDs generated through particle precipitation, Joule heating or Lorentz forcing
Thank You Zama Katamzi-Joseph 1,2 , Anasuya Aruliah 3 , Kjellmar Oksavik 4,5 , John Bosco Habarulema 1,2 , Kirsti Kauristie 6 , and Michael Kosch 1,7,8 1 South African National Space Agency , Hermanus, South Africa. 2 Dept. Physics & Electronics, Rhodes University , Grahamstown, South Africa. 3 Dept. Physics & Astronomy, University College London , UK. 4 Dept Physics & Technology, University of Bergen , Norway. 5 Arctic Geophysics, University Centre in Svalbard , Norway. 6 Finnish Meteorological Institute , Finland. 7 Dept Physics, Lancaster University , UK. 8 Dept, Physics & Astronomy, University of the Western Cape , South Africa.
References • Afraimovich, E., K. Palamartchouk, and N. Perevalova (1998), GPS radio interferometry of traveling ionospheric disturbances, J. Atmos. Sol. Terr. Phys., 60, 1205-1223, dio: 10.1016/S1364-6826(98)00074-1. • Habarulema, J., Z. Katamzi, and L.-A. McKinnell (2013), Estimating the propagation characteristics of large-scale traveling ionospheric disturbances using ground-based and satellite data, J. Gophys. Res. Space Physics, 118, 7768-7782, doi: 10.1002/2013JA018997. • Valladares, C., and M. Hei (2012), Measurements of the characteristics of TIDs using small and regional networks of GPS receivers during the campaign of 17-30 July of 2008, Int. J. Geophys., doi: 10.1155/2012/548784.
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