[IGPP Everyone] Reminder - Friday - Space Physics Seminar - Spring Quarter - Fri.May 7 , 2021 - 3:30pm - Zoom

[Marjorie Sowmendran]

R E M I N D E R 

SPACE PHYSICS SEMINAR 


DEPARTMENT OF EARTH, PLANETARY, AND SPACE SCIENCES 
DEPARTMENT OF ATMOSPHERIC AND OCEANIC SCIENCES 
UNIVERSITY OF CALIFORNIA, LOS ANGELES 

Join Zoom Meeting 

https://ucla.zoom.us/j/96663537686?pwd=bXVLSVFrU2g5T0dsU2lMQTFtOW5yUT09 




Meeting ID: 966 6353 7686; Passcode: 981246 

Lightning on Venus confirmed with 9 years of whistler-mode wave observations 


R. A. Hart 
Department of Earth, Planetary, and Space Sciences 
University of California, Los Angeles 


When lightning occurs, it produces atmospheric waves that can leak into the ionosphere and propagate in the whistler-mode. At Earth, these waves can be ducted by the dipolar magnetic field and propagate back and forth between conjugate magnetic footpoints. At Venus, however, there is no intrinsic magnetic dipole, instead the interplanetary magnetic field (IMF) drapes around the planet, magnetizing the ionosphere and forming a comet-like tail. The field lines tend to be nearly horizontal, parallel to the surface around much of the planet, except in the tail where it is more radial. Regions with a strong radial component to the field allow propagation to higher altitudes. Therefore, a wave on the dayside is less likely to enter the ionosphere at the zenith of its source and more likely to enter at angles towards the horizon, where the field lines and wave path are more aligned. 

The dual fluxgate magnetometer onboard Venus Express (VEX) was able to detect extremely low frequency (ELF) signals up to 64 Hz throughout the ionosphere of Venus. The mission was in orbit from 2006 - 2014 and in that time there were ~6 cumulative hours of whistler-mode wave observations. In some cases, there was continuous activity for over a minute, implying a connection to an electrical storm below. Most signals were observed when the spacecraft was within 200-300 km altitude at a rate of ~3% of the time. Whistlers may propagate significant distances in the ionosphere before detection, so the observation region may be 1000’s of kilometers from the source region. However, we are still able to estimate a lower limit for the global flash rate on Venus, which is 10x the global flash rate at Earth. 




Friday, May 7, 2021 

3:30 - 5:00 PM 

In-Charge: C. T. Russell 







-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.igpp.ucla.edu/pipermail/everyone/attachments/20210505/3d323306/attachment.html>