Features of the Electric Field HF Wave of the Sunsynchronous Orbit in the Solar Minimum Year

Abstract

Using the electric field High Frequency (HF) waves recorded by the Instrument Champ Electrique (ICE) onboard the DEMETER spacecraft in a solar low year, the spatial features of the waves from 10 kHz to 3.33 MHz are studied. During the quiet time of the geomagnetics, the higher the HF wave, the bigger the power spectrum intensity when the frequency lies between 2.08 MHz and 3.33 MHz. At the same time, the power spectrum intensity is almost uniform at different longitudes and latitudes. The difference of the power spectrum intensity between different longitudes and latitudes on the dayside is less than that on the nightside. The seasonal changes of the HF power spectrum intensity show that there are peaks at the dayside low latitudes in the frequency bands of 1.25 MHz and 1.66 MHz. During the quiet time, the discrepancy of the power spectrum intensities between different longitudes and latitudes obviously occurs at the frequency bands of 0.42 MHz and 1.66 MHz especially at high latitudea of the northern hemisphere on the dayside. During the geomagnetic activity, the HF response mainly appears at the low frequency band especially in high-latitude areas. In the equator and regions close to the low latitudes (latitude is between ±40 • ), the geomagnetic response of the HF is weak while that on the nightside in the magnetotail direction becomes strong especially during storms. Both at the northern and southern high latitudes during the storms on the nightside, the biggest power spectrum intensity is ten times that during the quiet. The biggest power spectrum intensity on the dayside at high latitudes of the southern hemisphere during the substorm and the period of the high latitude magnetic perturbation are ten times that during the quiet time. Considering that the perturbation coming from the space has an effect on high-latitude areas during the substorm and the periods of the high-latitude magnetic perturbation, the enhancement of the HF power spectrum intensity may origin from the spatial process. In view of that the data used in this study were collected in the solar minimum year and most of the storms were very weak with the strongest storm belonging to the moderate storm, the enhancements of the HF power spectrum intensity during the strong, severe even the great storms may be more obvious. If there is anomalous accretion in local areas during the quiet time especially when there is no storm, the abnormal phenomena are likely the ionospheric seismic-response to the dynamic processes of the internal earth such as earthquake preparation.