论文标题
在低海拔的bbelf波加热的O+离子上：测试粒子模拟
On O+ ion heating by BBELF waves at low altitude: Test particle simulations
论文作者
论文摘要
We investigate mechanisms of wave-particle heating of ionospheric O$^{+}$ ions resulting from broadband extremely low frequency (BBELF) waves using numerical test particle simulations that take into account ion-neutral collisions, in order to explain observations from the Enhanced Polar Outflow Probe (e-POP) satellite at low altitudes ($\sim$400 km)[Shen et al., 2018].我们认为，为了在E-Pop高度上观察到的离子温度，最有效的离子加热机制是通过与短级静电离子转基因（EIC）波（具有垂直波长$λ_{\ perp} $ perp} $ 4 $ \ leq $ 200 m的速度静电离子转基因（EIC）的加速度。有限的垂直波长，波浪振幅和离子 - 中性碰撞频率共同确定电离层离子加热极限之间的相互作用，该频率开始急剧下降，随着高度降低高于500 km的高度，该频率急剧降低，其中比率$ \\ frac $ \ frac {ν_c} $ frac {n v _} $ a} $ν_c$和$ f_ {ci} $表示O $^+$ - o碰撞频率和离子回旋频率。在数值和分析上，我们得出了离子Gyroradius的极限，从EIC波在一半的回旋频率下加热。限制为0.28 $λ_{\ perp} $。通过添加不同$λ_ {\ perp} $的波，或通过随机的“突破”，可以超越EIC波的离子Gyroradius极限，这意味着能量的离子扩散，而超出了Gyroradius限制，这是由于随机加热引起的随机加热而导致的振幅升高。我们的二维模拟表明，小规模（$ <$ 1 km）的Alfvén波无法通过捕获或随机加热来解释观察到的离子加热。
We investigate mechanisms of wave-particle heating of ionospheric O$^{+}$ ions resulting from broadband extremely low frequency (BBELF) waves using numerical test particle simulations that take into account ion-neutral collisions, in order to explain observations from the Enhanced Polar Outflow Probe (e-POP) satellite at low altitudes ($\sim$400 km)[Shen et al., 2018]. We argue that in order to reproduce ion temperatures observed at e-POP altitudes, the most effective ion heating mechanism is through cyclotron acceleration by short-scale electrostatic ion cyclotron (EIC) waves with perpendicular wavelengths $λ_{\perp}$$\leq$200 m. The interplay between finite perpendicular wavelengths, wave amplitudes, and ion-neutral collision frequencies collectively determine the ionospheric ion heating limit, which begins to decrease sharply with decreasing altitude below approximately 500 km, where the ratio $\frac{ν_c}{f_{ci}}$ becomes larger than 10$^{-3}$, $ν_c$ and $f_{ci}$ denoting the O$^+$--O collision frequency and ion cyclotron frequency. We derive, both numerically and analytically, the ion gyroradius limit from heating by an EIC wave at half the cyclotron frequency. The limit is 0.28$λ_{\perp}$. The ion gyroradius limit from an EIC wave can be surpassed either through adding waves with different $λ_{\perp}$, or through stochastic "breakout", meaning ions diffuse in energy beyond the gyroradius limit due to stochastic heating from large-amplitude waves. Our two-dimensional simulations indicate that small-scale ($<$1 km) Alfvén waves cannot account for the observed ion heating through trapping or stochastic heating.
