A5001665641- Solar and Space Plasma Dynamics
- Ionosphere and magnetosphere dynamics
- Geomagnetism and Paleomagnetism Studies
- Stellar, planetary, and galactic studies
- Astro and Planetary Science
- Geophysics and Gravity Measurements
University of Helsinki
2022-2023
Helsinki Institute of Physics
2022
Abstract We report direct observations of a fast magnetosonic forward–reverse shock pair observed by Solar Orbiter on 2022 March 8 at the short heliocentric distance 0.5 au. The structure, sharing some features with fully-formed stream interaction regions, is due to between two successive coronal mass ejections (CMEs), never previously give rise pair. scenario supported remote from extreme ultraviolet cameras and coronagraphs, where candidate eruptions compatible in situ signatures have been...
Abstract. We have performed an extensive statistical investigation of how interplanetary fast forward shocks affect certain turbulence parameters – namely, the normalised cross-helicity (𝜎𝑐), residual energy (𝜎𝑟) and magnetic helicity (𝜎𝑚). A total 371 detected by Wind at 1 au seven Solar Orbiter below 0.5 been analysed. explore aforementioned their variations across shock depend on characteristics, i.e. gas compression ratio, upstream plasma beta, velocity jump angle. find that in vicinity,...
ABSTRACT Interplanetary coronal mass ejections (ICMEs) contain magnetic field and velocity fluctuations across a wide range of scales. These may be interpreted as Alfvénic wave packets propagating parallel or antiparallel to the background field, with difference in power between counterpropagating fluxes quantified by cross helicity. We have determined helicity inertial at 10−3 10−2 Hz 226 ICME flux ropes 176 sheaths observed Wind spacecraft 1 au during 1995–2015. The had mean, normalized...
We have investigated how the degree of imbalance in solar wind turbulence is modified by large-scale velocity shears plasma. The balance between counterpropagating Alfv\'enic fluctuations, which interact nonlinearly to generate turbulence, has been quantified cross helicity and Elsasser ratio. Velocity at a 30-min timescale were identified, with shear amplitude defined terms linear Kelvin-Helmholtz (KH) instability threshold. associated 74 interplanetary coronal mass ejection (ICME) sheaths...
Sheaths ahead of interplanetary coronal mass ejections (ICMEs) are turbulent heliospheric structures. Knowledge their structure and fluctuations is important for understanding geoeffectiveness, role in accelerating particles, the interaction ICMEs with solar wind. We studied observations from Parker Solar Probe a sheath observed at 0.5 au March 2019, slow streamer blowout CME. To examine MHD-scale properties, we calculated fluctuation amplitudes, magnetic compressibility, partial variance...
Fast Coronal Mass Ejections (CMEs) gather compressed and heated solar wind ahead of them to for turbulent sheath regions. In this presentation we will first demonstrate with recent examples (using e.g. Parker Solar Probe Orbiter measurements) the results from a statistical analysis (the ACE spacecraft data) that CME-driven regions can significantly contribute acceleration charged particles in interplanetary space, independent effect leading shock wave.  Then, present key...
ICME plasma fluctuates across a broad range of scales, with fluctuations that display many similar spectral properties to other kinds solar wind. These fluctuations, which may represent turbulence, waves or structures in the plasma, are not well understood holistically context. Using data from Parker Solar Probe and Orbiter, we present analysis magnetic field spectra flux ropes at scales between rope radial width correlation length. The presence global causes significant steepening these...
Cross helicity quantifies the balance between counterpropagating Alfvénic fluctuations, which interact nonlinearly to generate turbulence in solar wind. We have investigated how cross is modified by large-scale velocity shears wind plasma. Using linear Kelvin–Helmholtz (KH) instability threshold, we identified at a 30-min timescale. The were associated with 74 interplanetary coronal mass ejection (ICME) sheaths observed Wind spacecraft 1 au 1997 and 2018. Typically weaker...
We have investigated how the degree of imbalance in solar wind turbulence is modified by large-scale velocity shears plasma. The balance between counterpropagating Alfvénic fluctuations, which interact nonlinearly to generate turbulence, has been quantified cross helicity and Elsasser ratio. Velocity at a 30-min timescale were identified, with shear amplitude defined terms linear Kelvin-Helmholtz (KH) instability threshold. associated 74 interplanetary coronal mass ejection (ICME) sheaths...
<p>Fast coronal mass ejections (CMEs) drive shock waves ahead of them. The turbulent sheath region between the and CME itself contains magnetic field velocity fluctuations on a broad spectrum frequencies. In this work we aim to characterise direction source solar wind at MHD fluid scales in CME-driven sheaths near Earth. One possible for these is shear, which are common occurrences sheaths. Here first identify shear as it occurs then relate that signatures new being created...
<p>Like the solar wind in general, interplanetary coronal mass ejections (ICMEs) display magnetic field and velocity fluctuations across a wide range of scales. These may be interpreted as Alfvénic wave packets propagating parallel or anti-parallel to local direction, with cross helicity, σ<sub>c</sub>, quantifying difference power between counter-propagating fluxes. We have determined...