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Spread F- An Historical Review. Ronald F. Woodman Instituto Geofísico del Perú. , 1938. Woodman, 1960.
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Spread F- An Historical Review Ronald F. Woodman InstitutoGeofísico del Perú LISN, INPE 2011
, 1938 LISN, INPE 2011
Woodman, 1960 LISN, INPE 2011
Figure 3. Graphic showing the state of Spread F for different days, different times of the day and the efeect it had on two satellites, 1960 Eta and 1960 Nu. Those passes that have a yellow underline, showed satellite scintillation. Notice the good correlation between scintillation and Spread F. (Adapted from Woodman, 1960) Scintillations vs Sp F LISN, INPE 2011 Woodman, 1960
LISN, INPE 2011 Abdu et al.,1998
Roettger, 1973 LISN, INPE 2011
After Woodman and La Hoz, 1976. Ilustrates Farley et al, 1970, conclusions LISN, INPE 2011
Woodman and La Hoz, 1976 LISN, INPE 2011
Woodman and La Hoz, 1976 Zalensak et al., 1982 LISN, INPE 2011
Woodman and La Hoz, 1976 Zalesak et al., 1982 LISN, INPE 2011
Woodman and La Hoz, 1976 LISN, INPE 2011
Woodman and La Hoz, 1976 LISN, INPE 2011
McClure, Hanson and Hoffman, 1977 LISN, INPE 2011
McClure, Hanson and Hoffman, 1977 LISN, INPE 2011
Figure 12. Neutral winds measured by AE-E during the same two consecutive orbits shown in Fig. 10 showing similar undulations atributed to gravity waves. After Singh et al., 1997. Figure 11. Ion drift data and electron density plots taking during two consecutive orbits (7192 and 7193), almost retracing one another. The large scale fluctuations are very similar. The first show undulations, attributed to gravity waves by the aut that have become unstable and broke under large structured bubbles. After Singh et al., 1997 Singh et al., 1997 LISN, INPE 2011
Spread-F event as viewed by (a) an airglow imager located in Cerro Tololo, Chile, and (b) by the Jicamarca Incoherent Scatter Radar in Lima, Peru. The event was observed on October 01, 2006. (J. Makela, personal communication) LISN, INPE 2011
Kelley et al., 1976 Morse et al., 1977 LISN, INPE 2011
Figure 13. Spatial relationship between Spread F depletions measured by satellites and backscatter power measured by the radar. After Tsunoda et al., 1982. Tsunoda et al., 1982 LISN, INPE 2011
ESF echoes(from Woodman and Chau [2001]) LISN, INPE 2011
used with permission Slit-camera Analogy and Problems • In some applications like races it is useful • In many other applications it provides misleading results: • Slow structures are stretch out • Fast-moving structures are compressed. • In general, it is difficult to discriminate space-time features. LISN, INPE 2011 Courtesy of Tom Grydeland
LISN, INPE 2011 Courtesy of D.L. Hysell
Hysell et al., 2006 LISN, INPE 2011
Figure 16. F and E region backscattering echoes from FAI. Notice the supression of the E region echoes when the velocity of the F region is downwards LISN, INPE 2011
Kudeki and Bhattacharya, 1999 LISN, INPE 2011
Hysell et al., 2006 LISN, INPE 2011
Figure 19. Numerical simulation showing the development of a shear collisional instability in the bottom of the F region. The model includes a sheared zonal plasma drift profile reversing to westward at lower altitudes, a altitude varying collision frequency and an eastward neutral wind. The top panel represents the plasma density, and the bottom, a stream function which controls the drift velocity perturbations . Notice the 45 quasi-sinusoidal waves changing from a transient behavior to longer wavelength during the steady state. Transient and steady states have been identified before in linear analytical mathematical models involving shear flows. After Hysell and Kudeki, 2004. LISN, INPE 2011
Figure 21. Plasma density fluctuations resultant from a non-local linear perturbation model of the “collisional shear instability”. Dimensions are normalized with respect to the gradient scale length, L. For L=20km, a neutral wind of 200 m/sec, vertical drift of 20 m/sec , gravity included, the growth rate is equivalent to 18 e-folds in an hour. No zonal plasma drift (hour. No zonal plasma drift( nd ireegularitieslower atmospheric origen poin increase the level of the geophysical noise aboveand no shear) is included. After Kudeki et al., 2007. LISN, INPE 2011
Measurements needed • Conductivities along the whole field tube (LISN) • Drift measurements at the bottom of the F region (Jicamarca) • Neutral wind (C/NOFS, LISN Inversions?) LISN, INPE 2011
Figure 10. Medium scale simulation of an interchange instablity diven by gravity and a zonal electric field. Notice the teardrop formations with steep boundaries . They would be the location where meter- scale wavelengths would be formed (bottom panel) in discrete clusters. The size of the simulation is 2Pi kilometer to a side. After Hysell, 2000. LISN, INPE 2011
Theory needed • 3D simulation including zonal winds and bottom drift shears, gravity, vertical drift and realistic density profiles at foot of magnetic field lines • 3m and 35 cm irregularity formation, kinetic description LISN, INPE 2011
Thank you Spread F- An old equatorial aeronomy problem finally resolved? Woodman, R. F. AnnalesGeophysicae Vol. 27, 1915-1934 (2009) LISN, INPE 2011
