Significance of lightning‐generated whistlers to inner radiation belt electron lifetimes

Abstract

[1] The behavior of high-energy electrons trapped in the Earth's Van Allen radiation belts has been extensively studied, through both experimental and theoretical techniques. While the evidence for whistler induced electron precipitation (WEP) from the radiation belts is overwhelming, and the mechanisms behind WEP are well understood, the overall significance of WEP on radiation belt loss rates has not been clear. In this paper we investigate the L-shell variation and significance of WEP-driven loss of Van Allen belt electrons by combining in situ measurements of electron precipitation, local WEP rates determined from Trimpi perturbations, and global lightning distributions. Our modeling suggests that long-term WEP driven losses are more significant than all other inner radiation belt loss processes for electron kinetic energies in the range $50-150 keV in the L-shell range L = 2-2.4. These calculated lifetimes are comparable to the observed decay rates of artificially injected high-energy electrons. The upper energy limit of the WEP significance range increases with decreasing L to $225 keV at L = 2. For electron energies above this range manmade VLF transmitters and plasmaspheric hiss should dominate over all other loss processes. However, as our lifetimes are based on rather conservative parameter estimates, these conclusions should represent the lower bounds for the energy ranges over which WEP losses are significant. For lower L-shells the coupling of lightning activity to the production of WEP events rapidly decreases, such that by L $ 1.7 WEP will be unimportant in the overall loss processes.INDEX TERMS: 2716 Magnetospheric Physics: Energetic particles, precipitating; 2730 Magnetospheric Physics: Magnetosphere-inner; 2736 Magnetospheric Physics: Magnetosphere/ionosphere interactions; 2483 Ionosphere: Wave/particle interactions; 3304 Meteorology and Atmospheric Dynamics: Atmospheric electricity; KEYWORDS: whistlers, inner radiation belt, electron precipitation, Trimpi, lightning, wave-particle interaction Citation: Rodger, C. J., M. A. Clilverd, and R. J. McCormick, Significance of lightning-generated whistlers to inner radiation belt electron lifetimes,

Assigning the causative lightning to the whistlers observed on satellites

“…Indeed, Manoranjan et al (1974) reported the low-latitude cutoff for whistlers observed on the ground, despite the fact that most of the lightning activity is in the tropics and/or in the subtropics (see, e.g. Rycroft et al, 2000).…”

“…The overall significance of lightning-generated whistlers to inner radiation belt electron loss rates is still an open question, and the approach to the problem and published results of various authors differ in some details. Rodger et al (2003) assumed ducted propagation and concluded that whistler-induced electron precipitation dominates in the L-shell range with L=2-2.4. Lauben et al (2001) and Bortnik et al (2003) assumed obliquely propagating and MR whistlers.…”

Relativistic electron flux dropouts in the outer radiation belt associated with corotating interaction regions

“…Precipitation loss of electrons due to wave scattering is attributed to a number of wave scattering mechanisms-e.g., interaction with electromagnetic ion cyclotron waves Meredith et al, 2003;Loto'aniu et al, 2006;, plasmaspheric hiss [Abel and Thorne, 1998;Meredith et al, 2006Meredith et al, , 2007, whistler mode chorus waves Thorne et al, 2005;Shprits et al, 2007], and lightning-generated whistlers [Voss et al, 1998;Rodger et al, 2003;Bortnik et al, 2006]. Drift loss of electrons occurs when the magnetopause is compressed inward and intersects the drift path of electrons in the outer radiation belt [Shprits et al, 2006;Turner et al, 2012;Tu et al, 2013Tu et al, , 2014.…”

Storm-time electron flux precipitation in the inner radiation belt caused by wave-particle interactions

“…In fact, the regular precipitation of energetic electrons (∼ several tens of keV) in the inner belt has been observed by low altitude satellites (e.g., Imhof et al, 1974;Inan et al, 1982). Recent articles reported that whistler-induced electron precipitation (WEP) from lightning is a significant inner radiation belt loss process at more than 100 keV (e.g., Rodger et al, 2003Rodger et al, , 2007. Thorne (1998a, b, 1999) estimated precipitation lifetimes due to wave-particle interactions with plasmaspheric hiss, lightning-generated whistler mode waves, and VLF transmitter sources as well as Coulomb collisions.…”