Spread F- An Historical Review

Ronald F. WoodmanInstituto Geofísico del Perú

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, 1938

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Woodman, 1960

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Scintillations vs Sp F

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)

Woodman, 19604/28/2010 LISN, INPE 2011

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Abdu et al.,19984/28/2010 LISN, INPE 2011

Roettger, 19734/28/2010 LISN, INPE 2011

After Woodman and La Hoz, 1976.Ilustrates Farley et al, 1970, conclusions

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Woodman and La Hoz, 1976

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Woodman and La Hoz, 1976Zalensak et al., 1982

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Woodman and La Hoz, 1976Zalesak et al., 1982

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Woodman and La Hoz, 1976

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Woodman and La Hoz, 1976

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McClure, Hanson and Hoffman, 1977

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McClure, Hanson and Hoffman, 19774/28/2010 LISN, INPE 2011

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

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.

Singh et al., 1997

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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)

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Morse et al., 1977

Kelley et al., 1976

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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

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ESF echoes(from Woodman and Chau [2001])

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Slit-camera Analogy and Problems

used with permission

•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.

Courtesy of Tom Grydeland4/28/2010 LISN, INPE 2011

Courtesy of D.L. Hysell4/28/2010 LISN, INPE 2011

Hysell et al., 20064/28/2010 LISN, INPE 2011

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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

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Kudeki and Bhattacharya, 1999

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Hysell et al., 20064/28/2010 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.

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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.

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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?)

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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

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Thank you

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Spread F- An old equatorial aeronomy problem finally resolved? Woodman, R. F.Annales Geophysicae Vol. 27, 1915-1934 (2009)