HR: 1340h
AN: AE23A-0833    [Abstracts]
TI: Initial Data from Balloon Borne Slow-Antenna
AU: * Sonnenfeld, R
EM: rsonnenf@nmt.edu
AF: Physics Department, New Mexico Tech, Socorro, NM 87801 United States
AU: Battles, J
EM: jbattles@nmt.edu
AF: Physics Department, New Mexico Tech, Socorro, NM 87801 United States
AU: Mong, B
AF: Physics Department, New Mexico Tech, Socorro, NM 87801 United States
AU: Aulich, G
AF: Langmuir Laboratory, 801 Leroy Place, Socorro, NM 87801 United States
AU: Eack, K
AF: Langmuir Laboratory, 801 Leroy Place, Socorro, NM 87801 United States
AU: Peischl, J
AF: Langmuir Laboratory, 801 Leroy Place, Socorro, NM 87801 United States
AU: Hunyady, S
AF: Langmuir Laboratory, 801 Leroy Place, Socorro, NM 87801 United States
AB: We report on progress toward the goal of using Balloon-borne slow antenna measurements in conjunction with lightning mapping array data to discern details of charge transport in lightning strokes. Our field-change electronics directly descended from traditional slow antennas. Each of four 100 cm$^{2}$ electrodes connects to a charge amplifier designed to swing each output by 1 Volt for 22.5 kV/meter of external E-field change. The instrument comprises four electrodes(virtual ground) mounted to a 6" diameter sheet aluminum cylinder (which provides common for all on-board electronics). The electrodes are arranged on the cylinder such that summing and differencing of electrode charges yields signals proportional to the E-field along the symmetry axis of the cylinder and in two directions perpendicular to it. Were it possible to hold the cylinder fixed in the sky, this electrode configuration would provide vector field-change data directly. As the cylinder cannot easily be constrained from rotating under a balloon, a multi-axis magnetometer is added to allow calculation of the instantaneous orientation of sonde and electrodes relative to fixed Earth B-field. To put all measurements in proper geographic context and enable ready package recovery, GPS data are collected and transmitted to ground. All data acquisition is integrated at a 16-channel, 16-bit A/D converter which multiplexes through 8 channels every 100 $\mu$s. The A/D converter is part of a single-board computer running Linux. The A/D buffering scheme is sufficient to acquire 2 seconds worth of data continuously. Every two seconds, data acquisition pauses for some tenths of a second to write the data to a compact flash. Telemetry at 19200 kbaud is also provided to enable real-time monitoring of instrument health and maximum E-field change over each 18-second data interval. Three flights into electrical storms and two ground tests during storms provided initial data. Lightning flashes are clearly seen on the ground corresponding to measurements by other ground-based E-field instruments. In flight, the dominant signal in an electrified environment with distant lightning flashes consists of two elements. a) Continuously varying signals in the fractional hertz range caused by the transverse components of the cloud electrical field modulated by the rotation of the package. b) Impulsive signals with periods of 2-5 milliseconds corresponding to corona discharge. With nearer lightning flashes, the signal is similar to ground-based measurements to first order. Our current efforts are in data analysis to properly remove the rotation effects and impulsive discharges.
DE: 0320 Cloud physics and chemistry
DE: 0394 Instruments and techniques
DE: 0694 Instrumentation and techniques
SC: Atmospheric and Space Electricity [AE]
MN: 2004 AGU Fall Meeting