(2015), Further evidence for a connection between auroral kilometric radiation and ground-level signals measured in Antarctica, J. Geophys. Res. Space Physics, 120, 2061-2075, doi:10.1002 Polarization measurements of one event show it to be right-hand polarized. Correlation analysis of ground-level and satellite data suggests an imperfect correlation with 2-3 sigma significance, although occasionally much better. (Perfect correlation is not expected, for at least two reasons: distant satellites detect AKR from many sources over a significant part of the oval, and many effects can hinder transmission of AKR from those sources to either distant satellites or ground stations.) Statistical analysis of the existing quantity of data is therefore suggestive but does not prove a connection between the ground-level AKR-like signals and outgoing AKR. However, two other methods provide evidence favoring such a connection. The first full-resolution measurements of ground-level AKR-like signals show that their fine structure strongly resembles that of AKR as known from high-resolution spacecraft receivers. Two case studies show that the location of active aurora, presumed connected with the AKR sources, controls whether or not the ground station detects the AKR, or which of several ground stations detects it most strongly. These investigations strengthen the hypothesis that through some mechanism, sources of outgoing AKR detected by distant satellites occasionally generate signals detectable as whistler mode waves at low altitude or right-hand polarized signals at ground level.

[1] The ACES-High rocket, part of the Auroral Current and Electrodynamics Structure (ACES) mission launched from Poker Flat Research Range on 29 January 2009, obtained the first in situ measurements indicative of both of the observational characteristics associated with the ionospheric feedback instability as it flew through an auroral arc and its associated return current region. ACES-High observed Alfvénic wave structures localized in areas of roughly 10 km near the boundaries of the return current region associated with the discrete auroral arc and increased electron density with a temperature characteristic of a cold ionosphere. This density enhancement is believed to be caused by the excavation of plasma from lower altitudes via the ponderomotive force produced by the ionospheric Alfvén resonator, as shown by Streltsov and Lotko (2008). While this density is lower than expected from simulations and other observations by as much as an order of magnitude, the ratio of the enhancement to the background density is in agreement with predictions. The observations made by ACES-High agree with the model results by Streltsov and Lotko (2008) but show the localized wave structures only near the boundaries of the return current region and not throughout it. This can be explained by strong small-scale magnetic field-aligned currents that are generated by the interaction between the large-scale downward current and the ionosphere at these boundaries. Finally, a new model, based on that by Streltsov and Marklund (2006), was run with only one downward current region and produced results very similar to the observations seen by ACES-High.

Abstract.The Auroral Current and Electrodynamics Structure (ACES) mission consisted of two sounding rockets launched nearly simultaneously from Poker Flat Research Range, AK on January 29, 2009 into a dynamic multiple-arc aurora. The ACES rocket mission was designed to observe electrodynamic and plasma parameters above and within the current closure region of the auroral ionosphere. Two well instrumented payloads were flown along very similar magnetic field footprints, at different altitudes, with small temporal separation between both payloads. The higher altitude payload (apogee 360 km), obtained in-situ measurements of electrodynamic and plasma parameters above the current closure region to determine the input signature.The low altitude payload (apogee 130 km), made similar observations within the current closure region. Results are presented comparing observations of the electric fields, magnetic components, and the differential electron energy flux at magnetic footpoints common to both payloads. In situ data is compared to the ground based all-sky imager data, which presents the evolution of the auroral event as the payloads traversed through magnetically similar regions. Current measurements derived from the magnetometers on the high altitude payload observed upward and downward field-aligned currents. The effect of collisions with the neutral atmosphere is investigated to determine

No abstract

Wave‐particle correlations, particularly of Langmuir waves and electrons, have been the subject of significant interest extending back to the 1970s. Often, these correlations have been simply observing modulation of the electrons at the plasma frequency with no phase resolution. The first phase‐resolving correlators were developed at UC Berkeley in the late 1980s and reported by Ergun in the early 1990s. A design is presented which further improves on phase resolution in correlations of Langmuir waves and electrons with phase resolution of 22.5°. In this technique, a phase‐locked loop (PLL) is used to lock onto the wave and subdivide the phase. Electrons are sorted on‐the‐fly as they arrive into the phase bins. Discussed are details of accurate timing, testing, and calibration of this system as well as results from rocket flights in which statistically significant phase correlations have been observed.