Venus Express flew over an electrical storm

Christopher Russell has been looking for proof of lightning in the atmosphere of Venus for quite a while (his earliest publication I could find on the subject was in 1979).  Now, Russell and his colleagues report on the strongest evidence yet for Venusian lightning (2012).

In order to remove interference from magnetometer data collected previously by Venus Express, Russell and his team devised a new algorithm that uses the inboard sensor to detect interfering signals and then removes the same signals from the outboard sensor data, resulting in a "cleaned" signal covering the frequency rane from 0 to 64 Hz.

Using the improved data collected during periapsis of the Venus Express spacecraft on April 15th of 2007, the researchers detected magnetic signals that led them to believe the craft had flown over an electrical storm.

Of note are two very different signals the authors believe are associated with electrical activity in the atmosphere of Venus:

1. a waveform that follows the prevailing magnetic field in the ionosphere and occurs at 20 Hz or above in the Extremely Low Frequency (ELF) range, and

2. a second signal that occurs at Ultra-low (ULF) frequencies (and are thus not restricted to moving along the magnetic field) and which propagates upward through the atmosphere.  The likely source is electrical activity beneath the spacecraft.

In addition, the data revealed the presence of whistler waves (which would be expected if lightning were present), and are consistent with previous studies (Russell et al. 2007).

Why is lightning on Venus important?  Knowing it is there can help in comparative studies between Earth and Venus, but more importantly it can help assist in the understanding of the chemical processes at work in the Venusian atmosphere.  The temperatures and pressures present in a lightning discharge provide a significant amount of energy that can drive chemical reactions, such as those that produce nitrous oxide.  Lightning is a proposed energy source for the creation of amino acids on the primordial Earth, the building blocks of life.


REFERENCES

Taylor, W. W. L., Scarf, F. L., Russell, C. T., & Brace, L. H. (1979). Evidence for lightning on venus. Nature, 279, 614-616.

Russell, C., Zhang, T., Delva, M., Magnes, W., Strangeway, R., & Wei, H. (2007). Lightning on venus inferred from whistler-mode waves in the ionosphere. Nature, 450(7170), 661-662.

Russell, C., Leinweber, H., Zhang, T., Daniels, J., Strangeway, R., & Wei, H. (2012). Electromagnetic waves observed on a flight over a Venus electrical storm Geophysical Research Letters DOI: 10.1029/2012GL054308