Abstract
AbstractUsing the Van Allen Probes A and B observations from 01 January 2013 to 28 February 2018, we surveyed statistically the occurrence rate, intensity, and propagation properties of hiss waves in the inner radiation belt (1.1 < L ≤ 2). Like the outer plasmaspheric hiss (L > 2), the occurrence rate and amplitude of lower‐band hiss (<600 Hz) are higher in the dayside high‐L region (L > 1.3 and magnetic local time [MLT] = 6–20 hr) than the nightside (MLT ∼ 20–6 hr) and increase with enhanced substorm activities (AE increases). Furthermore, their peak power spectral densities are located nearly in the same band (∼200–500 Hz). The equatorward propagation of middle‐latitude hiss suggests that the lower‐band hiss waves in the inner radiation belt mostly originate from the outer plasmaspheric hiss at high latitudes. Although the outer plasmaspheric hiss is also a likely source of weak upper‐band hiss (≥600 Hz) in the dayside high‐L region (L > 1.3 and MLT = 6–20 hr), the intense upper‐band hiss waves mostly appear in the dayside low‐L region (L < 1.3) and most nightside regions. In the low‐L region, the amplitude of the upper‐band hiss has no obvious substorm dependence, and the average of its wave normal angles is comparable to that of lightning‐generated whistlers reported in the past.
Published Version
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