Statistical distribution of height-integrated energy exchange rates in the ionosphere

摘要

[1]The EISCAT radar in Troms? (67° cgmLat) has been used to estimate statistics of electromagnetic (EM) energy transfer rates by utilizing calculated electric fields, conductivities and E-region neutral winds. It was found that the magnetospheric EM energy input is slightly larger in the evening than morning sector, but due to winds, the Joule heating rate has the largest values in the morning sector. The duskside subauroral region contains large northward electric fields and is a site of significant magnetospheric EM energy input and Joule heating. For quiet conditions (Kp: 0-2 ~+), the neutral wind is the major source for Joule heating at all MLT except at the evening maximum of magnetospheric EM input. For medium (Kp: 3 ~--4 ~+) and high (Kp ≥ 5-) activity levels, winds increase Joule heating rates in the morning, but decrease them in the evening. The positive contribution of winds during the morning maximum is 30% and 20% for medium and high activity levels, respectively. The region where winds are a net load for the magnetospheric EM energy input is 17-20 MLT for medium and 13-18 MLT for high activity conditions. The median EM energy transfer to mechanical work made on winds is 20% at maximum. An event with a long-lasting high electric field showed that the ion drag acting on neutrals can decrease the Joule (ion-neutral collisional) heating by more than 50%.