Ann. Geophys., 39, 461–470, 2021 https://doi.org/10.5194/angeo-39-461-2021 © Author(s) 2021. This work is distributed under the Creative Commons Attribution 4.0 License. Attenuation of plasmaspheric hiss associated with the enhanced magnetospheric electric field Haimeng Li1,2, Wen Li2, Qianli Ma3,2, Yukitoshi Nishimura2, Zhigang Yuan4, Alex J. Boyd5,6, Xiaochen Shen2, Rongxin Tang1, and Xiaohua Deng1 1Institute of Space Science and Technology, Nanchang University, Nanchang, China 2Center for Space Physics, Boston University, Boston, MA, USA 3Department of Atmospheric and Oceanic Sciences, University of California, Los Angeles, CA, USA 4School of Electronic Information, Wuhan University, Wuhan, China 5New Mexico Consortium, Los Alamos, NM, USA 6Space Sciences Department, The Aerospace Corporation, Chantilly, VA, USA Correspondence: Haimeng Li ([email protected]) and Wen Li ([email protected]) Received: 25 January 2021 – Discussion started: 5 February 2021 Revised: 7 April 2021 – Accepted: 8 April 2021 – Published: 18 May 2021 Abstract. We report an attenuation of hiss wave intensity in Thorne et al., 1973). However, recent studies indicate that the duskside of the outer plasmasphere in response to en- hiss wave frequencies can extend below 100 Hz during strong hanced convection and a substorm based on Van Allen Probe substorm activities (W. Li et al., 2013, 2015b, H. Li et al., observations. Using test particle codes, we simulate the dy- 2015; Ni et al., 2014). Hiss waves can scatter energetic elec- namics of energetic electron fluxes based on a realistic mag- trons into the loss cone, thereby playing an important role netospheric electric field model driven by solar wind and sub- in energetic electron dynamics in the radiation belt (Ma et auroral polarization stream. We suggest that the enhanced al., 2016; Meredith et al., 2006, 2007, 2009; Su et al., 2011; magnetospheric electric field causes the outward and sun- Thorne et al., 2013). The mechanism of hiss wave generation ward motion of energetic electrons, corresponding to the de- is still under active research. Two main generation mecha- crease of energetic electron fluxes on the duskside, leading nisms have been proposed: (1) external origination, propa- to the subsequent attenuation of hiss wave intensity. The re- gation effects of the whistler-mode chorus from the plasma- sults indicate that the enhanced electric field can significantly trough (Bortnik et al., 2008, 2009; W. Li et al., 2015a; Su et change the energetic electron distributions, which provide al., 2015) or lightning generated whistler (Draganov et al., free energy for hiss wave amplification. This new finding 1992; Green et al., 2005); and (2) internal generation, excita- is critical for understanding the generation of plasmaspheric tion due to local electron cyclotron resonance instability in- hiss and its response to solar wind and substorm activity. side the plasmasphere or plasmaspheric plume (Chen et al., 2014; Su et al., 2018; Summers et al., 2014; Thorne et al., 1979). Shi et al. (2019) suggest that the hiss waves in the outer plasmasphere tend to be locally amplified, whereas the 1 Introduction hiss waves at the lower L shells may propagate from higher L shells. The Poynting flux of hiss directed away from the Plasmaspheric hiss is a structureless, extremely low- Equator provides evidence of internal local generation of hiss frequency (ELF) whistler-mode wave that is found primarily waves (He et al., 2019; Kletzing et al., 2014; Laakso et al., in the plasmasphere (Russell et al., 1969; Thorne et al., 1973) 2015; Su et al., 2018). In contrast, the bidirectional Poynting and plasmaspheric plumes (Chan and Holzer, 1976; Shi et al., flux of hiss waves implies that local electron instability is rel- 2019; Yuan et al., 2012; Hayakawa et al., 1986). Hiss waves atively weak, and the observed hiss waves mainly originate are broadband emissions with frequencies typically between from chorus waves (Liu et al., 2017a, b). 100 Hz and 2 kHz (Meredith, 2004; Khazanov et al., 2004; Published by Copernicus Publications on behalf of the European Geosciences Union. 462 H. Li et al.: Attenuation of plasmaspheric hiss associated with the enhanced magnetospheric electric field A large-scale dawn–dusk convection electric field is pro- duced in the inner magnetosphere due to the motional so- lar wind electric field .ESW D −V × B), where V is the so- lar wind velocity, and B is the interplanetary magnetic field (Lei et al., 1981). Since the ESW is mapped along the geo- magnetic field lines and penetrates into the magnetosphere (Huang et al., 2007; Toffoletto and Hill, 1989), Goldstein et al. (2005a) suggest that the electric field at the plasma- pause was approximately 13 % of ESW. Besides the global contribution of ESW, the ionospheric subauroral polarization stream (SAPS) is potentially an important contributor to the magnetospheric electric field near the duskside (Goldstein et al., 2003, 2005b, a). The SAPS is the westward flow lo- cated at ∼ 3–5◦ of magnetic latitude below the auroral oval near the duskside. The ionospheric SAPS electric field can be mapped to the magnetic equatorial plane as radial electric fields. In general, the SAPS is related to the substorm and intensifies within ∼ 10 min after the substorm onset (Mishin and Mishin, 2007). It has been known that the dawn–dusk convection electric field plays an important role in the mo- tions of charged particles through the E × B drift, especially during strong geomagnetic activity (Burch, 1977; Ejiri, 1978; Frank, 1975). Using an improved electric field model driven by ESW and SAPS, Goldstein et al. (2003) simulated the evo- lution of the plasmapause location, which is found to be very similar to the plasmapause produced by the IMAGE extreme ultraviolet imager. Figure 1. Solar wind and geomagnetic parameters from 14:30 to In this paper, we report an interesting event where plas- 17:40 UT on 27 August 2013. (a) Three components of IMF in maspheric hiss intensity decreased, associated with the en- GSM coordinates. (b) Solar wind dynamic pressure, (c) proton den- hanced convection and substorm activity on 27 August 2013. sity, (d) solar wind velocity, and (e) convection electric field of solar Using test particle simulations based on the realistic electric wind. (f) AL index and (g) SYM-H index. The vertical line indicates field model, we provide direct evidence that the enhanced the time when the solar wind convection electric field started to in- magnetospheric electric field can contribute to the attenua- crease. tion of hiss wave intensity on the duskside. are used to identify the SAPS event. Furthermore, we use the 1 min resolution OMNI data to analyze the solar wind pa- 2 Satellite data rameters, including the interplanetary magnetic field (IMF). The twin Van Allen Probes with perigee and apogee of about 1.1 and 5.8 RE measure both hiss waves and energetic elec- 3 Event overview tron fluxes (Mauk et al., 2012). In this study, data from the Electric and Magnetic Field Instrument Suite and Integrated Figure 1 shows the overview of solar wind parameters and Science (EMFISIS) instrument are utilized to measure hiss geomagnetic indices for the event which occurred from 14:30 waves (Kletzing et al., 2013), and the data from the Electric to 17:40 UT on 27 August 2013. Following the enhanced Fields and Waves (EFW) instrument are utilized to measure southward IMF (Fig. 1a), ESW (Fig. 1e) evidently increased electric fields (Walsh et al., 2013). Moreover, we use the data at ∼ 15:53 UT and reached >2 mV/m after 16:30 UT. As from the Magnetic Electron Ion Spectrometer (MagEIS) and shown by AL and SYM-H indices (Fig. 1f and g), the strong the Helium Oxygen Proton Electron (HOPE) spectrometer to southward IMF triggered a substorm, which occurred during analyze in situ energetic electron distributions (Blake et al., the initial and main phases of a geomagnetic storm. Since 2013; Funsten et al., 2013; Spence et al., 2013). the large-scale magnetospheric dawn–dusk convection elec- The Defense Meteorological Satellite Program (DMSP) tric field is produced mainly due to the penetration of ESW satellites orbit around the Earth at an altitude of about 850 km (Huang et al., 2007; Lei et al., 1981; Toffoletto and Hill, and measure the ion drift velocities in both horizontal and 1989), the magnetospheric electric field is also expected to vertical directions perpendicular to the satellite orbit (Rich be enhanced during this time interval. and Hairston, 1994). In this study, the data of DMSP F17 Ann. Geophys., 39, 461–470, 2021 https://doi.org/10.5194/angeo-39-461-2021 H. Li et al.: Attenuation of plasmaspheric hiss associated with the enhanced magnetospheric electric field 463 Figure 2a–g show the observation of Van Allen Probe Figure 2h–n show the observation of Van Allen Probe B A from 14:00 to 16:30 UT. The measurement of total elec- from 16:00 to 18:20 UT. Van Allen Probe B passed through tron density (Fig. 2a) with a high value (>60 cm−3) before the same region at ∼ 2 h later than the observation by Probe 16:20 UT implies that the Van Allen Probe A was inside the A (Fig. 2a–g). At the same L shell, the change in total elec- duskside plasmasphere during this time interval. Strong plas- tron density was very small. Interestingly, compared to the maspheric hiss waves (Fig. 2b–e) were observed over 14:00– observation of Probe A (Fig. 2f), there was a very clear de- 16:30 UT, together with magnetosonic waves (MS) at low crease in energetic electron fluxes at > ∼ 10 keV at higher frequencies (below 90 Hz), whose ellipticity is close to zero L shells (Fig. 2m). Furthermore, the electron flux at > ∼ and wave normal angle is close to 90◦.