The next Orders of Magnitude - what s Next in Auroral Research,

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1 The next Orders of Magnitude - what s Next in Auroral Research, with some Geographical Implications Björn Gustavsson University of Southampton The next Orders of Magnitude - what s Next in Auroral Research, p. 1

2 Flickering Aurora The next Orders of Magnitude - what s Next in Auroral Research, p. 2

3 Flickering aurora is aurora that varies at high frequencies, most often at frequencies between 5 and 12 Hz. Whiter et al. [2010] showed that the intensity ratio of the energy of the flickering component of the precipitation increases with decreasing frequency - exactly as predicted from the Sakanoi-model [Sakanoi et al., 2005], from spectral ratios between emissions from O (7774 Å) and N2 (6730 Å) based on imaging with the ASK instrument (32 frames/s). Kataoka (in press) have recently (2011) presented spectral observations of flickering aurora at 100 frames/s also in emissions from O (8446) and N2 (6700), at these framerates it is possible to start to see phase shifts between the two emissions, possibly caused by time-offlight effects. McHarg et al. [1998] have shown flickering aurora at 100 Hz, from observations at 1000 frames/s (in white light). Grydeland et al. [2008] studied the ionospheric response to flickering aurora with ESR by using conditional integration (radar-pulses recieved at same phase of the optical flickering intensity variations was added together instead of adding pulse contiguous in time time) showing that the backscattered power was anticorrelated with the light - consistent with Te variations caused by variation in electron-electron heating. The vast improvement in time-resolution obtainable with optical instrumentation combined with the power of an E3D radar should make it possible to study flickering aurora (and other phenomena varying rapidly in time) and aurora should 2-1

4 confirm or refute these claims, in combination with multistation optical observations. If such observations were combined with simultaneous in-situ observations from rockets very solid science will be made. 2-2

5 Shear-motion The next Orders of Magnitude - what s Next in Auroral Research, p. 3

6 Shear motions and vortex-structures often appears in more dynamical auroral structures [e.g. Vogt et al., 1999; Asamura et al., 2009]- on all scales, from substorm-scales down to the smallest scales of a few ion gyro-radii - this example is from ASK where we see shear in an 500m wide arc ( 5 km between bulges). To determine what processes drives this motion we need an E3D radar, in combination with multistation spectral imaging. If such observations were combined with simultaneous in-situ observations from rockets very solid science will be made. 3-1

7 Auroral Filamentation The next Orders of Magnitude - what s Next in Auroral Research, p. 4

8 Filamentation of auroral arcs is often seen, [e.g. Semeter and Blixt, 2006; Semeter et al., 2008] have argued that it is caused by Alfven-waves. To study this we need E3D, in combination with multistation spectral imaging. and preferably together with simultaneous in-situ observations from rockets. If such observations were combined with simultaneous in-situ observations from rockets very solid science will be made. 4-1

9 Black Aurora I The next Orders of Magnitude - what s Next in Auroral Research, p. 5

10 Black aurora has been found to not be black at all [Gustavsson et al., 2008], and less black in emissions from atomic Oxygen than in emissions from molecular species, also radar observations show that black aurora structures do not move with the ionospheric convection but the drift velocity of black aurora is rather proportional to the energy of the electgrons in the surrounding diffuse aurora [Blixt et al., 2005b]. This is poorly consistent with the theory that black aurora is caused by retarding electrical fields. black aurora is also not a static phenomena but has a rather typical developing sequence - starting with smaller black blobbs, that elongates with time, and as they grow longer and more arc-like there is an increase in their wiggliness, sometimes developing to shear-flowing motions. 5-1

11 Black Aurora II The next Orders of Magnitude - what s Next in Auroral Research, p. 6

12 Sometimes BA appears simultaneously with pulsating aurora, how this differs from ordinary BA, and ordinary PA is something E3D should be able to answer in combination with multistation optical observations, and preferably together with simultaneous in-situ observations from rockets. How the black aurora and other structures in diffuse aurora evolves is something E3D should be able to answer in combination with multistation optical observations. If such observations were combined with simultaneous in-situ observations from rockets very solid science will be made. 6-1

13 NEIALs I The next Orders of Magnitude - what s Next in Auroral Research, p. 7

14 Then there is of course the NEIALs, that we just have to understand becuse of its very dynamic and structured characteristics, both in the radar observations Grydeland et al. [Here from 2004], and

15 NEIALs I The next Orders of Magnitude - what s Next in Auroral Research, p. 8

16 The corresponding auroral displays [The image/movie in the previous slice is from Blixt et al., 2005a]. This is something E3D should be able to answer in combination with multistation optical observations, however it might be a bit tricky to get simultaneous in-situ observations from rockets. 8-1

17 Geometry I Altitude (km) North South distance (km) North South distance (km) The next Orders of Magnitude - what s Next in Auroral Research, p. 9

18 In order to be able to use in-situ observations to their full potential it is imperative to be within one to a few horizontal scale lengths of the radar beam. Since the characteristical scale sizes are on the order of a few 100 m to a km this requires the rocket to pass above the magnetic zenith of the radar. For the case where rockets are launched from close to the radar site to the south. For an E-region apogee of km this puts the rocket impact to approximately 60 km south, while for an apogee of km the impact would be km to the south. For a launch-site 50 km south of the radar site the impact of a rocket with km would be km north of the rocket launch-site. For a launch site km south of the radar site the impact of rocket with apogee at km will fall north of the launch-site. 9-1

19 Geometry II Altitude (km) North South distance (km) North South distance (km) The next Orders of Magnitude - what s Next in Auroral Research, p. 10

20 In the next three slides it is shown that it would be possible to combine radar obsevations with an E-region rocket if the radar site would be located at Jouvlavarri inside the ESRANGE down-range area. Road already exists. For rockets reaching F- region altitudes is is more suitable to have the radar site in the general Skibotn-Kilpisjärvi area, then the rockets would impact smack in the middle of the normal ESRANGE impact area. From Andøya it seems difficult to launch rockets to the south, since there is some population living in the Lofoten and Bodøregion. 10-1

21 Geography I The next Orders of Magnitude - what s Next in Auroral Research, p. 11

22 Geography II The next Orders of Magnitude - what s Next in Auroral Research, p. 12

23 Geography III The next Orders of Magnitude - what s Next in Auroral Research, p. 13

24 References Asamura, K., et al., Sheared flows and small-scale alfvén wave generation in the auroral acceleration region, Geophys. Res. Lett., 36, L05,105, Blixt, E. M., T. Grydeland, N. Ivchenko, T. Hagfors, C. La Hoz, B. S. Lanchester, U. P. Løvhaug, and T. S. Trondsen, Dynamic rayed aurora and enhanced ion-acoustic radar echoes, Annales Geophysicae, 23, 3 11, 2005a. Blixt, E. M., M. J. Kosch, and J. Semeter, Relative drift between black aurora and the ionospheric plasma, Ann. Geophys., 23, , 2005b. Grydeland, T., E. M. Blixt, U. P. Løvhaug, T. Hagfors, C. La Hoz, and T. S. Trondsen, Interferometric radar observations of filamented structures due to plasma instabilities and their relation to auroral rays, Ann. Geophys., 22, , Grydeland, T., B. Gustavsson, L. Baddeley, J. Lunde, and E. M. Blixt, Conditional integration of incoherent scattering in relation to flickering aurora, J. Geophys. Res., 113, A08,305, Gustavsson, B., M. J. Kosch, A. Senior, A. J. Kavanagh, B. U. E. Brändström, and E. M. Blixt, Combined EISCAT radar and 13-1

25 optical multispectral and tomographic observations of black aurora, Journal of Geophysical Research (Space Physics), 113, A06,308, McHarg, M. G., L. Hampton, Don, and H. C. Stenbaek-Nielsen, Fast photometry of flickering in discrete auroral arcs, Geophys. Res. Lett., 25, , Sakanoi, K., K. Fukunishi, and Y. Kasahara, A possible generation mechanism of temporal and spatial structures of flickering aurora, J. Geophys. Res., 110, Semeter, J., and E. M. Blixt, Evidence for Alfvén wave dispersion identified in high-resolution auroral imagery, Geophys. Res. Lett., 33, 13,106, Semeter, J., M. Zettergren, M. Diaz, and S. Mende, Wave dispersion and the discrete aurora: New constraints derived from high-speed imagery, J. Geophys. Res., 113, A12,208, Vogt, J., H. U. Frey, G. Haerendel, H. Höfner, and J. L. Semeter, Shear velocity profiles associated with auroral curls, J. Geophys. Res., 104, 17,277 17,288, Whiter, D. K., B. S. Lanchester, B. Gustavsson, N. Ivchenko,, and H. Dahlgren, Using multispectral optical observations to 13-2

26 identify the acceleration mechanism responsible for flickering aurora, J. Geophys. Res., 115, A12,315,