Experiment Motivation

1. Simultaneous Measurements of Lower E-region Nighttime Electrodynamics Gathered with Rockets and the Altair Radar During the EQUIS II Campaign at Kwajalein Atoll R. Pfaff, D. Rowland, M. Acuña, H. Freudenreich NASA/Goddard Space Flight Center E. Kudeki University of Illinois, Urbana-Champaign, IL M. Larsen Clemson University, Clemson, S.C. J. Clemmons, R. Bishop Aerospace Corp., El Segundo, CA C. Steigies University of Kiel, Germany R. Woodman, M. Sarango Jicamarca Radio Observatory, Peru AGU Meeting New Orleans, LA 24 May 2005

2. Experiment Motivation • The objective of the EQUIS-2 “Nighttime E-region” experiment was to investigate the electrodynamics of the nighttime E-region near the magnetic equator. • Experiment included two sets of rocket payloads designed to determine how the DC electric field, plasma density, neutral winds, neutral density, and instabilities characterize the nighttime, lower E-region (95-115 km) near the magnetic equator. • Powerful Altair incoherent scatter/coherent scatter radar would be used to characterize the unstable lower ionosphere. • Although radar measurements from Piura, Peru and Gadanki, India at similar latitudes provided important background information, we were uncertain whether we would encounter conditions similar to mid-latitude sporadic-E or to those of the nighttime electrojet.

3. Roi-Namur Kwajalein is ~ 5 degrees from the magnetic equator.

4. Geometry for E-region Rocket/Radar Experiment

5. Rocket Instrumentation Instrumented rocket Prime Measurements • DC and AC electric fields • DC magnetic fields • Plasma density • Wavevector and phase velocity (using interferometers) • Neutral density Chemical Release rocket • Neutral winds and turbulence using tri-methyl aluminum vapor trails

6. Payload orientation placed electric field double probes in plane perpendicular to the magnetic field. Emeridional Ezonal

9. Kwajalein Atoll -- 21.132 7 September 2004, 11:43:55.0 U.T. Upleg Downleg

10. DC Electric Fields E x B Plasma Velocity Local time of launch: 23:43:55

11. Kwajalein Atoll -- September 7, 2004 Neutral Wind Rocket (Launched 12 minutes later)

14. Altair Radar -- 17 Sept 2005 -- 08:00 U.T. UHF -- 422 MHz (36 cm backscatter) VHF -- 158 MHz (95 cm backscatter) Altitude, km Zonal Range (km) Radar data reveal a moderate layer near 101 km in the vicinity of the rocket trajectory upleg.

15. Kwajalein Atoll -- 21.133 17 September 2004, 08:00:45.0 U.T. Upleg Downleg

16. Goddard Impedance Probe provides absolute plasma density See presentation by Rowland et al. (this meeting).

17. DC Electric Fields E x B Plasma Velocity Local time of launch: 20:00:45

20. TMA (Wind) Rocket Launch: 08:12:00 U.T. Dual Rocket and Radar Experiment Kwajalein Atoll 17 September 2005 Instrumented Rocket Launch: 08:00:45 U.T.

22. Large scale electric field structures Up/Down Zonal Total E • Large scale horizontal/vertical structure: ~ 5 - 10 km, primarily below 110 km • Smaller scale structures: ~ 1-3 km, primarily below 105 km • Minimum variance shows wavevectors primarily are down/west or up/east.

23. Shorter scale electric fields in downleg region. Spin plane, orthogonal E measurements Meridional (up/down) Zonal (East-West)

24. Dual baseline plasma wave interferometer 4.35 m baseline 0.75 m baseline 4.35 m baseline 0.75 m baseline

25. Plasma wave interferometer -- downleg region 4.35 m baseline 0.75 m baseline meas= k.b + n 2 Vf = b/ meas At 232 sec, f = 39.1 Hz, meas = 60o for b = 4.35m,  = 26 m V’f = 1021 m/s; Vrocket along b is 916 m/s; V = 105 m/s ~ E x B

26. • Measureable phase extends only to about 150 Hz or ~7m • Both baselines show wave phase velocity is constant (dispersionless) at low frequencies

27. 21.133 -- Downleg Irregularities 100 m 10 m

28. Summary --Rocket 21.133 • Rocket launched while moderate meter-scale backscatter was observed by the Altair radar. • In-situ probes measured enhanced eastward electric fields from 95-105 km with an upwards meridional component of 4 mV/m on the downleg. • Distinct, yet broad layer of plasma waves with amplitudes of several mV/m were observed in the altitude range of 96-105km. • Short scale waves propagate primarily in the zonal direction with spectra extending to about 6-8m. • Plasma density of 104 cm-3 without any sharp gradients or layers • Large scale electric field and plasma density variations observed with horizontal scales or 2-10 km yet with distinct vertical components. • Neutral wind data show intense shear at 105 km, velocities of 200 m/s. • Neutral wind “turbules” were observed primarily below 100 km with scales of about 1 km.

29. Major Questions Raised by Experiment What is causing the sudden appearance and disappearance of very large amplitude patches of VHF and UHF backscatter observed by the Altair radar? What determines the observed horizontal spatial scales of several tens of km? What sets up the large neutral wind velocity and shear and how does this effect the electrodynamics? What drives the km-scale plasma irregularities observed in situ without any well-developed plasma gradient and despite different DC electric field orientations between the two experiments? What drives the short scale plasma waves observed in situ that are presumably related to the backscatter meter-scale Altair radar echoes? Clearly, they are sub-acoustic (not 2-stream driven) and the density gradient is stable.

30. Back-up Slides

32. Altair Radar -- 7 Sept 2005 -- 11:42 U.T. UHF -- 422 MHz Altitude, km VHF -- 158 MHz Zonal Range (km)

33. Altair Radar -- 7 Sept 2005 -- 11:42 U.T. VHF -- 158 MHz Altitude, km Zonal Range (km) Radar data reveal a weak layer near 107 km in the vicinity of the rocket trajectory upleg.