Multi‐Parameter Chorus and Plasmaspheric Hiss Wave Models

Abstract

The resonant interaction of energetic particles with plasma waves, such as chorus and plasmaspheric hiss waves, plays a direct and crucial role in the acceleration and loss of radiation belt electrons that ultimately affect the dynamics of the radiation belts. In this study, we use the comprehensive wave data measurements made by the Electric and Magnetic Field Instrument Suite and Integrated Science instruments on board the two Van Allen probes, to develop multi‐parameter statistical chorus and plasmaspheric hiss wave models. The models of chorus and plasmaspheric hiss waves are presented as a function of combined geomagnetic activity (AE), solar wind velocity (V), and southward interplanetary magnetic field (Bs). The relatively smooth wave models reveal new features. Despite, the coupling between geomagnetic and solar wind parameters, the results show that each parameter still carries a sufficient amount of unique information to more accurately constrain the chorus and plasmaspheric hiss wave intensities. The new wave models presented here highlight the importance of multi‐parameter wave models, and can improve radiation belt modeling.

Global Map of Chorus Wave Sizes in the Inner Magnetosphere

“…This is an indication of well defined chorus wave packets during active conditions compared to more quiet and moderate conditions. Also, it is worth pointing out that for high solar wind velocities the observations show a less clear transition point than for high AE and high Bz, indicating that AE and Bz are better controlling parameters for chorus wave activity than solar wind velocity, which is consistent with past studies (Aryan et al., 2014, 2016, 2021).…”

“…Overall, the results indicate that the size of chorus wave packets depends on the intensity and activity of chorus waves in the inner magnetosphere. In general, the largest chorus wave packets are observed where chorus wave activity is also high (Aryan et al., 2016, 2017, 2021; Meredith et al., 2001).…”

“…Results show that the size of lower band chorus wave packets varies between ∼1,000 and 2,000 km depending on the intensity and activity of chorus waves in the inner magnetosphere. The largest chorus wave packets are generally observed on the dawn-dayside during active geomagnetic conditions where chorus wave intensity and activity is also high (Aryan et al, 2016(Aryan et al, , 2017(Aryan et al, , 2021Meredith et al, 2001).…”

“…Local acceleration by wave particle interactions further energizes the seed electrons to highly relativistic energies (>1 MeV) (Horne et al., 2000; Summers et al., 2002; Thorne et al., 2013), over broad regions of the outer radiation belt on timescales of hours (Baker & Kanekal, 2008; Baker et al., 2014; Foster et al., 2014; Reeves et al., 2013; Summers et al., 1998). Chorus emissions are excited naturally within a few degrees of the geomagnetic equator outside the plasmapause where the density is low (Agapitov et al., 2010; Burtis & Helliwell, 1969; LeDocq et al., 1998; Santolík et al., 2005) mainly throughout the dawn‐dayside (Aryan et al., 2016, 2017, 2021; Meredith et al., 2001) where they propagate from the geomagnetic equator roughly along the magnetic field (Agapitov et al., 2013; Bortnik et al., 2007; LeDocq et al., 1998; Santolík et al., 2005) to higher latitudes in both the Southern and the Northern hemispheres (Bortnik & Thorne, 2007; LeDocq et al., 1998; Santolík et al., 2014; Santolík & Gurnett, 2003).…”

Identification of Controlling Geomagnetic and Solar Wind Factors for Magnetospheric Chorus Intensity Using Feature Selection Techniques

“…Their results show that the large amplitude chorus waves are connected with both electron cyclotron frequency and magnetic latitude during active geomagnetic conditions. Very recently, Aryan et al (2021) used ∼7 years VAP data to develop a multi-parameter chorus wave model as a function of combined geomagnetic activity (AE), solar wind speed (V SW ), and southward interplanetary magnetic field (B s ), which can potentially provide significant improvement to the radiation belt models. They further investigated the variation of chorus wave intensity by splitting AE, V SW , and Bs into three intervals.…”