Geomagnetic storms: Occurrence rate related to Solar cycle and the role of Alfvénic turbulence

Abstract:

Geomagnetic storms are disturbances in the Earth’s magnetosphere due to interactions
with solar wind, where plasma ejected from Sun transfer large amounts of energy to the
upper atmosphere. These events are usually responsible for a wide range of anomalies
and malfunctions in satellites, communication systems and technological infrastructure,
and therefore are considered a threat to high latitude and space exploration as well as a
risk to human life. For this reason, the study of their occurrence and intensity is relevant
in space weather in order to prevent and reduce their impact over modern technological
infrastructure. Several studies have revised relationship between geomagnetic storms
and solar activity, concluding that quantity and intensity of storms enhances if the
sunspot number increase. On this basis, the aim of this work is to establish an analysis
of energy transfer mechanisms from the solar wind to the inner magnetosphere during a
geomagnetic storm by analyzing Dst time series between 1957-2019, to establish a
probability occurrence due to its intensity. Data were separated by solar cycle and solar
cycle phases, and fitted through Maximum Likelihood method, with median rate of 95%
confidence intervals using Bootstrap Method, finding year frequency, and comparing
with events happened during solar cycle 24. In addition, we establish a prediction over
solar cycle 25, expected to be similar to the previous one. We also explore the
mechanisms that trigger these storms considering that the solar wind-magnetosphere
interactions are turbulent, by establishing correlations between many geomagnetic
indexes such as PC, AE and SYM-H, with the occurrence of ULF fluctuations on the
solar wind, and analyzing the role of Alfvénic turbulence role on the energy transference
from the solar wind to the magnetosphere.