INVESTIGATIONS OF COSMIC SOURCES RADIOEMISSION SCINTILLATIONS DUE TO INTERPLANETARY PLASMA IRREGULARITIES AT THE INSTITUTE OF RADIO ASTRONOMY, NAS UKRAINE

Purpose: Review of investigations of cosmic sources radioemission scintillations due to interplanetary plasma irregularities made at the Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, from the first observations in the mid-70s until now. Design/methodology/approach: In the course of preparation of this paper, the authors have reviewed, analyzed and summarized the information being published in the home and foreign publications, and reported at scientific conferences. Findings: The investigations of the interplanetary scintillations carried out at the Institute of Radio Astronomy, NAS Ukraine have been reviewed. A retrospective discussion has been made on how in the course of these researches the knowledge about the basic parameters of interplanetary scintillations in the decameter wavelength range, as well as that on the important parameters of the solar wind and its structure, have been obtained. Also, various methods of processing and analysis of experimental data were offered, and new means for receiving cosmic radiation were created. The place and importance of the discussed researches for the world science are shown. Conclusions: Over the years since the beginning of the research, the think tank of the Department of Low-Frequency Radio Astronomy of the Institute of Radio Astronomy, NAS Ukraine has obtained a number of new relevant results, which bring Ukraine into the cohort of world centers of interplanetary scintillation researches. The construction of a new GURT radio telescope, among other things, creates new prospects for the development of this relevant line of investigation. Key words: interplanetary scintillations; decameter wavelength range; solar wind; solar wind stream structure; coronal mass ejection

Study of Galactic Cosmic-Ray Flux Modulation by Interplanetary Plasma Structures for the Evaluation of Space Instrument Performance and Space Weather Science Investigations

The role of high-energy particles in limiting the performance of on-board instruments was studied for the European Space Agency (ESA) Laser Interferometer Space Antenna (LISA) Pathfinder (LPF) and ESA/National Astronautics and Space Administration Solar Orbiter missions. Particle detectors (PD) placed on board the LPF spacecraft allowed for testing the reliability of pre-launch predictions of galactic cosmic-ray (GCR) energy spectra and for studying the modulation of proton and helium overall flux above 70 MeV n − 1 on a day-by-day basis. GCR flux variations up to approximately 15% in less than a month were observed with LPF orbiting around the Lagrange point L1 between 2016 and 2017. These variations appeared barely detected or undetected in neutron monitors. In this work the LPF data and contemporaneous observations carried out with the magnetic spectrometer AMS-02 experiment are considered to show the effects of GCR flux short-term variations with respect to monthly averaged measurements. Moreover, it is shown that subsequent large-scale interplanetary structures cause a continuous modulation of GCR fluxes. As a result, small Forbush decreases cannot be considered good proxies for the transit of interplanetary coronal mass ejections and for geomagnetic storm forecasting.

DIVISION E COMMISSION 49: INTERPLANETARY PLASMA AND HELIOSPHERE

After a little more than forty years of work related to the interplanetary plasma and the heliosphere the IAU's Commission 49 was formally discontinued in 2015. The commission started its work when the first spacecraft were launched to measure the solar wind in–situ away from Earth orbit, both inward and outward from 1 AU. It now hands over its activities to a new commission during an era of space research when Voyager 1 measures in–situ the parameters of the local interstellar medium at the edge of the heliosphere. The commission will be succeeded by C.E3 with a similar area of responsibility but with more focused specific tasks that the community intends to address during the coming several years. This report includes a short description of the motivation for this commission and of the historical context. It then describes work from 2012 to 2015 during the present solar cycle 24 that has been the weakest in the space era so far. It gave rise to a large number of studies on solar energetic particles and cosmic rays. Other studies addressed e.g. the variation of the solar wind structure and energetic particle fluxes on long time scales, the detection of dust in the solar wind and the Voyager measurements at the edge of the heliosphere. The research is based on measurements from spacecraft that are at present operational and motivated by the upcoming Solar Probe + and Solar Orbiter missions to explore the vicinity of the Sun. We also report here the progress on new and planned radio instruments and their importance for heliospheric studies. Contributors to this report are Carine Briand, Yoichiro Hanaoka, Eduard Kontar, David Lario, Ingrid Mann, John D. Richardson.