Geoeffective jets impacting the magnetopause are very common

Area of Science:

• Space Physics
• Plasma Physics
• Geophysics

Background:

• Transient dynamic pressure enhancements, known as high-speed jets, frequently occur in the subsolar magnetosheath.
• These jets can impact the magnetopause, leading to localized indentations and various downstream effects on the magnetosphere and ionosphere.

Purpose of the Study:

• To calculate the impact rates of geoeffective high-speed jets on the dayside magnetopause for the first time.
• To determine the frequency of jet impacts based on their size and occurrence conditions.

Main Methods:

• Utilized a large dataset of Time History of Events and Macroscale Interactions during Substorms (THEMIS) multispacecraft observations.
• Analyzed jet observations to determine distributions of scale sizes perpendicular and parallel to the direction of propagation.
• Derived jet impact rates using the distribution of perpendicular scale sizes.

Main Results:

• Jet scale sizes were modeled by an exponential function with characteristic scales of 1.34 RE (perpendicular) and 0.71 RE (parallel).
• The impact rate of jets with diameters larger than 2 RE on the subsolar magnetopause is approximately 3 per hour.
• Under conditions favorable for jet occurrence (low interplanetary magnetic field cone angle <30°), the impact rate increases to about 9 per hour.

Conclusions:

• This study provides the first quantitative assessment of high-speed jet impact rates on the magnetopause.
• Jet characteristics and their impact frequency are crucial for understanding solar wind-magnetosphere coupling and space weather.
• The findings highlight the significant role of these jets in driving geomagnetic activity.