Simultaneous Observations of Electric Fields, Current Density, Plasma Density, and Neutral Winds During Two Sounding Rocket Experiments Launched from Wallops Island into Strong Daytime Dynamo Currents

Tuesday, 15 December 2015: 10:35
2016 (Moscone West)
Robert F Pfaff Jr1, Douglas E. Rowland1, Jeffrey Klenzing2, Henry T Freudenreich2, Steven C Martin2, Takumi Abe3, Hiroto Habu3, Masa-yuki Yamamoto4, Shigeto Watanabe5, Mamoru Yamamoto6, Tatsuhiro Yokoyama7, Yoshihiro Kakinami8, Yosuke Yamazaki9, Miguel Folkmar Larsen10, Lucas Hurd10, James H Clemmons11, Rebecca L Bishop12, Richard L Walterscheid12, Chad S Fish13, Terence W Bullett14, Justin John Mabie14, Neil Murphy15, Vassilis Angelopoulos16, Hannes Karl Leinweber17, Ivan Bernal16 and Peter J Chi18, (1)NASA Goddard Space Flight Center, Heliophysics Sci. Div., Greenbelt, MD, United States, (2)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (3)Japan Aerospace Exploration Agency, Kanagawa, Japan, (4)Kochi University of Technology, School of Systems Engineering, Kami, Japan, (5)Hokkaido University, Sapporo, Japan, (6)Kyoto University, Kyoto, Japan, (7)National Institute of Information and Communications Technolog, Koganei, Japan, (8)Kochi University of Technology, Kami, Kochi, Japan, (9)University of Lancaster, Physics, Lancaster, United Kingdom, (10)Clemson University, Clemson, SC, United States, (11)Aerospace Corporation El Segundo, El Segundo, CA, United States, (12)Aerospace Corporation Los Angeles, Los Angeles, CA, United States, (13)Atmospheric and Space Technology Research Associates, LLC, Boulder, CO, United States, (14)NOAA, Boulder, CO, United States, (15)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (16)University of California Los Angeles, Earth, Planetary, and Space Sciences, Los Angeles, CA, United States, (17)Institute of Geophysics and Planetary Physics Los Angeles, Los Angeles, CA, United States, (18)University of California Los Angeles, Los Angeles, CA, United States
To investigate the ion-neutral coupling that creates the global electrical daytime “dynamo” currents in the mid-latitude, lower ionosphere, NASA carried out two multiple sounding rocket experiments from Wallops Island, VA on July 10, 2011 (14:00 UT, 10:00 LT) and July 4, 2013 (14:31 UT, 10:31 LT). The rockets were launched in the presence of well-defined, westward Hall currents observed on the ground with ΔH values of ­–25 nT and –30 nT, respectively, as well as a well-defined, daytime ionospheric density observed by the VIPIR ionosonde at Wallops. During the 2011 experiment, a narrow, intense sporadic-E layer was observed near 102 km. Each experiment consisted of a pair of rockets launched 15 sec apart. The first rocket of each pair carried instruments to measure DC electric and magnetic fields, as well as the ambient plasma and neutral gases and attained apogees of 158 km and 135 km in the 2011 and 2013 experiments, respectively. The second rocket of each pair carried canisters which released a lithium vapor trail along the upleg to illuminate neutral winds in the upper atmosphere. This daytime vapor trail technology was developed jointly by researchers at JAXA and Clemson University. In the second experiment, the lithium release was clearly visible in cameras with infrared filters operated by US and Japanese researchers in a NASA airplane at 9.6 km altitude. The observed wind profiles reached speeds of 100 m/s with strong shears with respect to altitude and were consistent with an independent derivation of the wind from the ionization gauge sensor suite on the instrumented rocket. The “vapor trail” rockets, which also included a falling sphere, attained apogees of 150 km and 143 km in the 2011 and 2013 experiments, respectively.

By measuring the current density, conductivity, DC electric fields, and neutral winds, we solve the dynamo equation as a function of altitude, revealing the different contributions to the lower E-region currents. We find that the DC electric fields (~2 mV/m, peak) and neutral winds (~100 m/s, peak) are organized such that their contributions to the overall dynamo current largely cancel, leaving net current densities commensurate with those largely predicted by tidal theory. We discuss the implications of these measurements for our understanding of the daytime dynamo process.