Jovian Lightning-Induced Electromagnetic Waves Observed by the Juno Waves Instrument

0504692 - ÚFA 2020 BE eng A - Abstrakt
Kolmašová, Ivana - Imai, M. - Santolík, Ondřej - Kurth, W. S. - Hospodarsky, G. B. - Gurnett, D. A. - Bolton, S.J. - Connerney, J. E. P.
Jovian Lightning-Induced Electromagnetic Waves Observed by the Juno Waves Instrument.
URSI AP-RASC 2019 Proceedings. Gent: URSI, 2019.
[URSI Asia Pacific Radio Science Conference (AT-RASC). 09.03.2019-15.03.2019, New Delhi]
Institucionální podpora: RVO:68378289
Klíčová slova: lightning whistlers pulses * discrete dispersed pulses * Juno spacecraf
Obor OECD: Fluids and plasma physics (including surface physics)
http://www.ursi.org/proceedings/procAP19/papers2019/URSIAPRASCAbstractKolmasovafinal1.pdf

Two new types of lightning induced electromagnetic signals - low dispersion lightning whistlers and discrete
dispersed pulses - were observed by the Waves instrument [1] onboard the Juno spacecraft during close
approaches of the spacecraft to the planet below radial distances of 5.5 Jovian radii. The detections of these two
emissions show evidence on very low density ionosphere at Jupiter.
More than 2500 of lightning whistlers were detected in electric and magnetic field waveform snapshots recorded
by the Low Frequency Receiver from August 2016 to May 2018. The whistlers at frequencies from 50 Hz to 20
kHz have unusually low dispersion which can be, in some cases, explained by dispersion calculations based on
existing models of ionospheric plasma density and magnetic field. Some observations, however, indicate low
ionospheric density regions predominantly occurring in the northern hemisphere at latitudes between 20° and
70°. We detect peak occurrence rates of more than four whistlers per second, with an average rate of one
whistler per second at midlatitudes, similar to thunderstorms at Earth [2]. Additionally, we estimated the
whistler propagation distance below ionosphere to be typically one to several thousand kilometers but with a
possibility of no sub-ionospheric propagation [3].
We have also found nearly five hundred unusual discrete dispersed pulses in electric field waveform snapshots
at millisecond time scales. They were collected by the Low Frequency Receiver between10 kHz and 150 kHz
from August 2016 to October 2017. We propose that these Jupiter dispersed pulses (JDPs) propagate in the free
space left-hand ordinary mode. Based on the dispersion and on the cutoff frequency of detected pulses we
estimated plasma densities and lengths of plasma irregularities along the line of propagation of JDPs from
lightning to Juno. Our findings imply existence of very low density holes (≤ 250 cm-3) in the night-side
ionosphere.

Trvalý link: http://hdl.handle.net/11104/0296275