Low Frequency (f < 200 Hz) Polar Plasmaspheric Hiss: Coherent and Intense

Bruce T Tsurutani (1) , Sang Park (2) , Barbara Falkowski (3) , Jacob Bortnik (4) , Gurbax Lakhina (5) , Abhijit Sen (6) , Jolene Pickett (7) , Rajkumar Hajra (8) , Michel Parrot (9) , Pierre Henri (9)

1 JPL - Jet Propulsion Laboratory
2 UC Berkeley - University of California [Berkeley]
3 Glendale Community College
4 UCLA - University of California [Los Angeles]
5 IIG - Indian Institute of Geomagnetism [Navi Mumbai, India]
6 Institute for plasma research
7 Department of Physics and Astronomy [Ames, Iowa]
8 NARL - National Atmospheric Research Laboratory [Tirupati]
9 LPC2E - Laboratoire de Physique et Chimie de l'Environnement et de l'Espace

Low Frequency (LF) ~22 Hz to 200 Hz plasmaspheric hiss was studied using a year of Polar plasma wave data occurring during solar cycle minimum. The waves are found to be most intense in the noon and early dusk sectors. When only the most intense LF (ILF) hiss were examined, they are found to be substorm dependent and most prominent in the noon sector. The noon sector ILF waves were also determined to be independent of solar wind ram pressure. The ILF hiss intensity are independent of magnetic latitude. ILF hiss is found to be highly coherent in nature. ILF hiss propagates at all angles relative to the ambient magnetic field. Circular, elliptical and linear/highly elliptically polarized hiss have been detected, with elliptical polarization the dominant characteristic. A case of linear polarized ILF hiss that occurred deep in the plasmasphere during geomagnetic quiet was noted. The waveforms and polarizations of ILF hiss are similar to those of intense high frequency (IHF) hiss. We propose the hypothesis that ~10‐100 keV substorm injected electrons gradient drift to dayside minimum B pockets close to the magnetopause to generate LF chorus. The closeness of this chorus to low altitude entry points into the plasmasphere will minimize wave damping and allow intense noon‐sector ILF hiss. The coherency of ILF hiss leads the authors to predict energetic electron precipitation into the midlatitude ionosphere and the electron slot formation during substorms. Several means of testing the above hypotheses are discussed.

Domaines: Planète et Univers [physics]

Bruce T Tsurutani, Sang Park, Barbara Falkowski, Jacob Bortnik, Gurbax Lakhina, et al.. Low Frequency (f < 200 Hz) Polar Plasmaspheric Hiss: Coherent and Intense. Journal of Geophysical Research Space Physics, 2019, 124 (12), pp.10063-10084. ⟨10.1029/2019JA027102⟩. ⟨insu-02404879⟩