These data are collected under a collaborative arrangement between the Australian Antarctic Division (Principal Investigator: Gary Burns) and the Russian Antarctic Expeditions (Most-recent contact: Alexandr Frank-Kamenetsky, Institute of Arctic and Antarctic Studies, St Petersburg)
In 2006 a new electric field mill (EFM) commenced operation at Vostok. This electric field mill is mounted on an all metal post ~3m above the snow surface. Values are positive for a downward-directed electric field. This EFM is different in operation and deployment from an earlier instrument that operated between 1998-2002 and in 2004 which was mounted on a 1.5m metal pole at deployment.
The ASAC_974 project formally concluded in June 2011, but the Russians (contact: Alexandr Frank-Kamenetsky, Institute of Arctic and Antarctic Studies, St Petersburg) have continued data collection at Vostok after this time, under an agreement to utilise the Australian developed equipment.
Data provided here-in consist of 20-minute averaged, absolute values of the electric field measured at ~3m above the snow surface at Vostok across the years 2006 to 2011, inclusive. Absolute values were determined by stepping voltages between +5 and -5kV through a wire above the EFM at Vostok. Monthly calibrations were undertaken relative to a Faraday-shielded box containing parallel plates placed over the rotating dipole to which a range of stepped voltages were applied. Linear interpolations of these monthly relative calibrations were applied to the raw minute-averaged data to yield absolute values. The linear interpolations will be more fully described in a future data set of minute-averaged data. The variations associated with the monthly calibrations are less than the statistical uncertainties associated with the 20-minute averaging.
Three of the four data sets here-in have been corrected for the solar wind imposed potential (SWIP) above Vostok determined from the Weimer (2001) empirical model (without adjustment for the possible AL auroral index allowance), offset by 20-minutes as the average allowance for the propagation of the interplanetary magnetic field influence from the noon magnetopause to the near-ground-level (~3m) electric field measurements at Vostok. The magnitude of the correction for the SWIP influence and the determination of the appropriate scaling factor are described in the Appendix section of Burns et al. (2017).
The three separate, corrected-for-SWIP, data selections are described in Burns et al. (2017). An initial rejection of the minute-averaged data is made for electric fields with two hour prior to and after exceeding 300 V/m for all data sets. This rejects measurements generally influenced by local falling, wind-blown or lifted snow or ice which result in high electric field values. The two extended time intervals are a conservative allowance for the local influences prior to the cut-off electric field value being reached.
For two of the three separate, corrected-for-SWIP data sets an additional criteria with different levels of severity was used to reject rapid variations below the cut-off threshold based on jumps in the electric field within a five-minute interval. Due to the time constant (~15 minutes) associated with the atmospheric circuit, rapid variations in the electric field are more likely to be associated with local influences. This is confirmed in Burns et al. (2017) by the relative association of the selected data sets with the SWIP-above-Vostok and independently by comparison with simultaneous electric field measurements at Concordia.
Strong variation rejection (svr) data selections reject minute-averaged data within 30 minutes of a jump of 30 V/m (with 5 minutes). Medium variation rejection (mvr) data selections reject minute-averaged data within 10 minutes of a jump of 50 V/m (within 5 minutes). No variation rejection (nvr) data selections made no rejection on the basis of rapid variations (within 5 minutes). At least 16 individual minutes of data (80%) were required for determination of a 20-minute average.
The fourth electric field data set listed herein is the 20-minute average of the nvr data without correction for the local SWIP. Here-in this may be referred to as the ‘raw’ absolute, 20-minute-average, electric field measurement. Also included with the data are the Weimer (2001) model SWIP (in kV) above Vostok, calculated as described in Burns et al. (2017).
Tests of instrumentation resulted in the earliest 20-minute-averaged electric field measurements at Vostok commencing at 14.5UT, 5th January, 2006.
The data provided consists of up to 11 fields.
The first six columns are date-time related fields. The first field is an Excel derived date-time to 6 decimal places of the mid-point of the 20-minute average. The second field is the ‘year’, followed by the ‘month’, ‘day-of-month’ and decimal UT hour (two decimal places) designating the 20-minute averaging interval and then the integer ‘day-of-year’.
The seventh column is the Weimer (2001) model (without AL auroral activity adjustment) estimate of the SWIP above Vostok (derived as per explained in Burns et al., 2017).
The eighth column is the ‘raw’ 20-minute averaged electric field (V/m) at Vostok..
The ninth to eleventh columns list the nvr, mvr and svr 20-minute electric field data as described and tested in Burns et al. (2017).
Missing data are presented as blanks.
Suggested acknowledgements for the utilisation of these data are:
‘These Vostok electric field data were collected by collaboration between the Australian Antarctic Division and the Russian Antarctic Expeditions. Australian involvement was approved by the Australian Antarctic Advisory Committee (AAS 974). Russian involvement was supported under the Russian Federal Program: World Ocean: Study and Research in Antarctica: Determination of Changes in the Antarctic Environment: Environmental Monitoring operated by the Arctic and Antarctic Research Institute, St. Petersburg.’
Burns, G.B., A.V. Frank-Kamenetsky, B.A. Tinsley, W.J.R. French, and P. Grigioni, G. Camporeale, and E.A. Bering, 2017: Atmospheric global circuit variations from Vostok and Concordia electric field measurements. J. Atmos. Sci., doi:10.1175/JAS-D-16-0159-1.
Weimer, D.R., 2001: An improved model of ionospheric electric potentials including substorm perturbations and application to the Geospace Environment Modelling November 24, 1996, event. J. Geophys. Res., 106, 407-416.