Abstrakt
During the Juno perijove explorations from 27 August 2016 through 1 September 2017, strong electromagnetic impulses induced by Jupiter lightning were detected by the Microwave Radiometer (MWR) instrument in the form of 600-MHz sferics and recorded by the Waves instrument in the form of Jovian low-dispersion whistlers discovered in waveform snapshots below 20 kHz. We found 71 overlapping events including sferics, while Waves waveforms were available.
Eleven of these also included whistler detections by Waves. By measuring the separation distances between the MWR boresight and the whistler exit point, we estimated the distance whistlers propagate below the ionosphere before exiting to the magnetosphere, called the coupling distance, to be typically one to several thousand of kilometers with a possibility of no subionospheric propagation, which gives a new constraint on the atmospheric whistler propagation.
Plain Language Summary Lightning at Jupiter produces a strong electromagnetic impulse, which can escape the Jovian atmosphere and enter the inner magnetosphere. Among the lightning, microwave-frequency sferics come from lightning spots, and audio-frequency whistlers propagate away from the spots below the ionosphere.
If certain plasma conditions are met, these whistlers can leak into the magnetosphere. Estimates of whistler propagation distances at the planet have not been previously performed.
Since the arrival at Jupiter on 5 July 2016, the Juno spacecraft has provided the opportunity to monitor the two kinds of lightning activity with two onboard instruments during its closest approach to Jupiter. This opportunity happens every 53.6 day in the eccentric, polar orbit of Juno.
Using data collected during Juno's closest approaches to Jupiter, the whistler propagation distance was estimated to be approximately one to several thousand kilometers, which may be comparable to the terrestrial equivalent. This new approach provides the benefit of understanding multidimensional structures of lightning at Jupiter.