Dependence of Properties of Magnetospheric Line Radiation and Quasiperiodic Emissions on Solar Wind Parameters and Geomagnetic Activity

Abstract

Very low frequency electromagnetic waves in the inner magnetosphere sometimes exhibit either frequency or time modulation. These phenomena are called, respectively, magnetospheric line radiation (MLR) and quasiperiodic (QP) emissions. Data from Detection of Electro-Magnetic Emissions Transmitted from Earthquake Regions spacecraft were used to analyze their properties, such as MLR frequency spacing, QP modulation period, and QP intensity as functions of geomagnetic activity and solar wind parameters. Altogether, 1,152 MLR events and 2,172 QP emissions were analyzed. It is shown that the influence of the analyzed parameters on QP emissions is different for QP events with modulation periods shorter/longer than 20 s. While the properties of QP events with long modulation periods are significantly related to the geomagnetic activity and solar wind parameters, no such dependences are observed for events with short modulation periods. This suggests that there might be two types of QP emissions generated by two different mechanisms. It is further shown that there seems to be no relation between the properties of QP and MLR events observed at the same times. Finally, the event properties do not seem to be related to the whistler occurrence rate.

Conjugate Observations of Quasiperiodic Emissions by the Van Allen Probes Spacecraft and Ground‐Based Station Kannuslehto

“…However, this QP classification was based on ground-based measurements and, as shown by Tixier and Cornilleau-Wehrlin (1986), it is not straightforward to apply to spacecraft observations, rendering it somewhat unclear (Sazhin & Hayakawa, 1994). Additionally, Bezděková et al (2019) reported that properties of QP emissions with short (<∼20 s) and long (>∼20 s) modulation periods react differently to geomagnetic activity, suggesting that they might be generated by different mechanisms.…”

A Large‐Scale Magnetospheric Line Radiation Event in the Upper Ionosphere Recorded by the China‐Seismo‐Electromagnetic Satellite

“…MLR events occur more often on the dayside than the night side, and their location is mostly at regions of L > 2 but typically inside the plasmasphere. Additionally, their occurrence primarily depends on disturbed space weather conditions (Bezděková et al., 2019; Parrot et al., 2007).…”

Very Low Frequency Whistler Mode Wave Events Observed Simultaneously by the Kannuslehto Station and Van Allen Probes

“…Due to the relatively straightforward measurement technique used for their detection, they have been studied on the ground for more than 60 years (Helliwell, 1965). However, while their detection provides a remarkable amount of information about the magnetosphere, generation mechanisms, properties, and means of propagation of many of the observed wave phenomena are not yet fully understood (e.g., Bezděková et al., 2019; Breuillard et al., 2014; Green et al., 2005; Manninen, 2005; Rodger et al., 2000). Hence, they are still in the scope of intense research.…”