New experimental evidence of the effect of magnetic storms on the magnetosphere

New methods of whistler analysis have recently been developed and have been used to study the effect of magnetic storms on the magnetosphere. It is found that whistler observations preceded within 72 hours by a 3-hour Kp level of 6 or more show relatively low values of time delay at typical whistler nose frequencies. During the main phase and recovery phase of several severe magnetic storms, depressions in nose frequency time delays on the order of 2:1 are observed. Evidence is presented that the depressions in whistler delays may be interpreted as reductions in electron density in the magnetosphere. The depression in electron density during several severe storms is then on the order of 4∶1.