Abstract
| Space Weather Impacts of Solar Wind High-Speed Streams: A comparative study for the Earth and comet |
Rajkumar Hajra |
| Space weather generally refers to dynamic variations at the Sun and in interplanetary space disturbing the plasma environment of solar system bodies like the Earth, planets and comets. Solar wind high-speed (> 550 km s-1) streams (HSSs) emanating from solar coronal holes are one of the main sources of space weather. As the solar coronal holes are long-lived structures, the corresponding HSSs appear to “corotate” with the Sun, very much like water spewing from a lawn sprinkler. The interaction between HSSs and slow-speed (~300-400 km s-1) streams near the ecliptic plane gives rise to compressed plasma and magnetic field regions, the so-called corotating interaction regions (CIRs). At large heliocentric distances (≥ 3 AU) the leading and trailing edges of the CIRs are characterized by interplanetary forward and reverse “collisionless” shocks, respectively. In the present talk, some recent studies on the HSS/CIR characteristics and impacts on the Earth (1 AU) and the comet (~3 AU) will be discussed. The CIRs followed by HSSs sometimes lead to intense auroral activities that continue for days to weeks, known as HILDCAA (high-intensity long-duration continuous AE activity) events. Injections of ~10-100 keV energetic electrons during substorm and convection events associated with HILDCAAs generate electromagnetic chorus waves in the outer radiation belt of the Earth’s magnetosphere. Resonant interactions of these waves with ~100 keV electrons lead to the acceleration to relativistic (~MeV) energies. Our study indicates that ground-based HILDCAA observations can be utilized to predict magnetospheric whistler-mode chorus waves and relativistic electron acceleration more than 1 day in advance. Using ESA Rosetta observation of comet 67P/Churyumov-Gerasimenko, HSS/CIR impacts on cometary plasma environment at ~3 AU will be shown to access the differential interplanetary characteristics and impacts compared to those at 1 AU (Earth). |
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Last updated on: February 20, 2024