Multi‐Point Observation of Hiss Emerging From Lightning Whistlers

• Published in: Journal of geophysical research. Space physics Vol. 126; no. 12
• Main Authors: Santolík, Ondřej, Kolmašová, Ivana, Pickett, Jolene S., Gurnett, Donald A.
• Format: Journal Article
• Language: English
• Published: 01.12.2021
• Subjects: Cluster; plasmaspheric hiss; whistlers; WWLLN
• ISSN: 2169-9380; 2169-9402
• DOI: 10.1029/2021JA029524

We analyze continuous multi‐point measurements of electromagnetic field waveforms onboard the Cluster spacecraft in order to contribute to the discussion on sources of plasmaspheric hiss, known as a shaping agent for the Earth radiation belts. In our case study we aim at finding sources of hiss observed close to the geomagnetic equator in the outer plasmasphere on the dayside. We find hiss to be triggered from whistlers of different spectral properties. Whistlers with the lowest observed dispersion arrive to different spacecraft with time delays indicating their origin in the northern hemisphere. Positions of source lightning discharges are then found using the time coincidences with the Word Wide Lightning Location Network data from three active thunderstorm regions in Europe. We find that subionospheric propagation of lightning atmospherics is necessary to explain the observations. Geographic locations of their ionospheric exit points then determine spectral properties of resulting unducted whistlers and triggered hiss. By this well documented chain of events starting with a lightning discharge in the atmosphere we confirm that magnetospherically reflecting whistlers and hiss triggered from them are among possible sources of plasmaspheric hiss. Key Points We use multi‐point measurements of electromagnetic field fluctuations by the cluster space fleet to discuss sources of plasmaspheric hiss Our case study shows hiss which was triggered in the dayside outer plasmasphere by unducted whistlers emitted from strong lightning strokes Spectral properties of magnetospherically reflecting whistlers and hiss strongly depend on geographical location of the source thunderstorm