A Generalized Magnetospheric Disturbance Index: Initial Application to Mars Using MAVEN Observations

Since MAVEN's arrival at Mars in 2014, in situ observations of the magnetic field have been made continually. During this time, the Martian magnetosphere has been disturbed by various solar transient events such as stream interaction regions (SIRs) and interplanetary coronal mass ejections (ICMEs). To understand the impact of transient events on magnetospheres, statistical studies with large sets of events are necessary. At Earth, quantitative disturbance metrics have been employed, primarily relying on ground‐based magnetometer observations, enabling statistical studies of transient events to various physical processes driven by solar wind‐planetary interactions. However, many of these indices require assumptions about the magnetic field background. Lacking an intrinsic global magnetic field, the Martian magnetosphere is a product of piled‐up interplanetary magnetic field resulting in a variable “nominal” state of the system. To estimate the level of the disturbance to the Martian system, we have developed a generalized Magnetospheric Disturbance Index (MDI). MDI normalizes each observation and quantifies the change in field strength and variability inside of the bow shock. As an initial application, we compare the effectiveness of more than 70 SIRs and ICMEs at disturbing the Martian system. We find that the strength of MDI is not dependent on the type of space weather event impacting Mars. Additionally, the duration of the disturbance is not correlated to the type of space weather event or strength of disturbance. The short duration of the disturbance may imply that the system reacts to enhanced dynamic pressure and quickly relaxes back to a nominal state. Key Points We develop the Magnetospheric Disturbance Index to quantify space weather effects at Mars The strength of magnetospheric disturbance at Mars is not well correlated with a specific type of space weather event Most of the disturbance events have a duration of less than 20 hr, regardless of space weather event type or strength of disturbance