Low-energy solar electron bursts and solar wind stream structure at 1 AU

BepiColombo is going to conduct its first Mercury flyby in October 2021. During this flyby,&#160; plasma measurement will be obtained and bring new insights on the Hermean magnetosphere and its interaction with the Sun despite the limited field of view of the instruments during the cruise phase. Unlike Mariner-10 ion measurements will be obtained, and unlike MESSENGER, low energy electrons and ions will be measured simultaneously. In this study, we have revisited Mariner 10 and MESSENGER observations with the help of the global hybrid model LatHyS in order to understand the influence of time-variable solar wind and to constraint the plasma environment. We are able to reproduce the magnetic field observations of Mariner 10 along its trajectory with in particular two distinct signatures consisting of a quiet and disturbed state of the magnetosphere. In addition, the plasma spectrogram is also collected in the model and this enables us to detail the properties of the charged particles observed during the flyby. We will discuss all these signatures both in term of an interaction with a time-variable solar wind and localized processes occurring in the magnetosphere. We will then present the virtual sampling of both the magnetic field and plasma spectrogram along BepiColombo&#8217;s first Mercury flyby trajectory and discuss the possible signatures to be observed at that time.

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The low-energy ion event on 2020 June 19 measured by Solar Orbiter

10.5194/egusphere-egu21-15864 ◽

2021 ◽

Author(s):

Angels Aran ◽

Daniel Pacheco ◽

Monica Laurenza ◽

Nicolas Wijsen ◽

Evangelia Samara ◽

...

Keyword(s):

Solar Wind ◽

Energy Range ◽

Extreme Ultraviolet ◽

Solar Rotation ◽

Complex Structure ◽

Forbush Decrease ◽

Solar Wind Plasma ◽

Low Energy ◽

The European Union ◽

Horizon 2020

Shortly after reaching the first perihelion, the Energetic Particle Detector (EPD) onboard Solar Orbiter measured a low-energy (<1 MeV/nuc) ion event whose duration varied with the energy of the particles. The increase above pre-event intensity levels was detected early on June 19 for ions in the energy range from ~50 keV to ~1 MeV and lasted up to ~12:00 UT on June 20. In the energy range from ~10 keV to < 40 keV, the ion event spanned from June 18 to 21. This latter low-energy ion intensity enhancement coincided with a two-step Forbush decrease (FD) as displayed in the EPD > 17 MeV/nuc ion measurements. On the other hand, no electron increases were detected. As seen from 1 au, there is no clear evidence of solar activity from the visible disk that could be associated with the origin of this ion event. We hypothesize about the origin of this event as due to either a possible solar eruption occurring behind the visible part of the Sun or to an interplanetary spatial structure. We use interplanetary magnetic field data from the Solar Orbiter Magnetometer (MAG), solar wind electron density derived from measurements of the Solar Orbiter Radio and Plasma Waves (RPW) instrument to specify the in-situ solar wind conditions where the ion event was observed. In addition, we use solar wind plasma measurements from the Solar Orbiter Solar Wind Analyser (SWA) suite gathered during the following solar rotation, for comparison purposes. In order to seek for possible associated solar sources, we use images from the Extreme Ultraviolet Imager (EUI) instrument onboard Solar Orbiter. Together with the lack of electron observations and Type III radio bursts, the simultaneous response of the ion intensity-time profiles at various energies indicates an interplanetary source for the particles. The two-step FD shape observed during this event suggests that the first step early on June 18 was due to a transient structure, whereas the second step on June 19, together with the ~50 &#8211;1000 keV/nuc ion enhancement, was due to a solar wind stream interaction region. The observation of a similar FD in the next solar rotation favours this interpretation, although a more complex structure cannot be discarded due to the lack of concurrent solar wind temperature and velocity observations.Different parts of this research have received funding from the European Union&#8217;s Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) and grant agreement No 01004159 (SERPENTINE).

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