Speaker
Description
The origin, acceleration, and anisotropy of suprathermal ions in the interplanetary medium remain poorly understood till date. These ions serve as seed populations for solar energetic particles (SEP) which are capable of damaging space assets. In this study, we investigate the directional spectra of suprathermal ions during quiet solar wind conditions in January-November, 2024. We utilize in situ data from the Supra-Thermal and Energetic Particle Spectrometer (STEPS), a key instrument of the Aditya Solar Wind Particle EXperiment (ASPEX) onboard India’s Aditya-L1 spacecraft. STEPS includes four sensors: Parker Spiral (PS), Inter-Mediate (IM), Earth Pointing (EP), and North Pointing (NP), with three sensors located in the ecliptic plane and one (NP) oriented orthogonal to the rest of the three. The spectral indices derived from these sensors during multiple quiet intervals in 2024 indicate nearly isotropic suprathermal ion distributions. This validates the isotropic assumption made by previous researchers while solving Parker Transport equation to explain the acceleration of suprathermal ions. Although STEPS provides directional measurements, it does not differentiate species. Hence, we analysed elemental abundance ratios (³He/⁴He, Fe/O, and C/O) using data from the Ultra-Low Energy Isotope Spectrometer (ULEIS) onboard the ACE spacecraft for the same intervals to understand source processes that might have created these suprathermal ions. These analyses suggest that the quiet-time suprathermal pool contains residual ions from previous impulsive (solar flare) and gradual (CME-driven) SEP events. Therefore, the investigation provides valuable insights into the directional characteristics and source processes of the suprathermal ion population in the interplanetary medium during quiet solar conditions in the maximum of solar cycle 25. The key results and implications of this study will be discussed in detail in this presentation.
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