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Space Physics Seminar

High-Speed Solar Wind Streams and Corotating Interaction Regions: Some Study on Interplanetary Characteristics, Evolution and Impacts
Presented by Rajkumar Hajra
National Atmospheric Research Laboratory, Gadanki, India

Tuesday, February 19, 2019
11:00 A.M. in 169-336

Solar coronal holes emanate high-speed (~750-800 km s-1) streams (HSSs). As the coronal holes are long-lived structures, the corresponding HSSs appear to "corotate" with the Sun, very much like water spewing from a lawn sprinkler. These HSSs, when they interact with slow-speed (~300-400 km s-1) streams near the ecliptic plane, give 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 shocks, respectively. However, as the shock formation occurs due to the nonlinear steepening of waves that requires several nonlinear steepening times, most CIRs do not have shocks at 1 AU.

In the present talk, we will show some recent results of the HSS/CIR impacts on the Earth's outer radiation belt and topside ionosphere using satellite and radar observation data. Using incoherent scatter radar (ISR) observations from Arecibo Observatory (geomagnetic: 28.17°N, 5.88°E, dip: 46.7°, L = 1.3), it will be shown that the topside ionosphere can become hotter and expand significantly in altitude during a HSS interval, with a significant increase in the O+/H+ transition altitude/protonosphere base.

The CIR followed by HSS sometimes leads to intense auroral activity that continues for days to weeks, known as HILDCAA events (high-intensity long-duration continuous AE activity). Injections of ~10-100 keV energetic electrons during substorm and convection events associated with HILDCAAs generate electromagnetic chorus waves in the outer radiation belt. Resonant interactions of these waves with ~100 keV electrons lead to the acceleration to relativistic energies. Our study indicates that ground-based HILDCAA observations can be utilized to predict whistler-mode chorus waves and magnetospheric relativistic electron acceleration more than 1 day in advance.

Using ESA Rosetta observation of comet 67P/Churyumov-Gerasimenko, CIR/HSS 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). At the end, we will discuss the acceleration of relativistic electrons in the outer radiation belt of Jupiter.

JPL Contact: If you would like to meet with the speaker, please contact Bruce Tsurutani (4-7559).

SVCP Astrophysics

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